PAU/GNSS-R: Implementation, Performance and First Results of a Real-Time Delay-Doppler Map Reflectometer Using Global Navigation Satellite System Signals

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Enric Valencia

2008-05-01

Full Text Available Signals from Global Navigation Satellite Systems (GNSS were originally conceived for position and speed determination, but they can be used as signals of opportunity as well. The reflection process over a given surface modifies the properties of the scattered signal, and therefore, by processing the reflected signal, relevant geophysical data regarding the surface under study (land, sea, ice… can be retrieved. In essence, a GNSS-R receiver is a multi-channel GNSS receiver that computes the received power from a given satellite at a number of different delay and Doppler bins of the incoming signal. The first approaches to build such a receiver consisted of sampling and storing the scattered signal for later post-processing. However, a real-time approach to the problem is desirable to obtain immediately useful geophysical variables and reduce the amount of data. The use of FPGA technology makes this possible, while at the same time the system can be easily reconfigured. The signal tracking and processing constraints made necessary to fully design several new blocks. The uniqueness of the implemented system described in this work is the capability to compute in real-time Delay-Doppler maps (DDMs either for four simultaneous satellites or just one, but with a larger number of bins. The first tests have been conducted from a cliff over the sea and demonstrate the successful performance of the instrument to compute DDMs in real-time from the measured reflected GNSS/R signals. The processing of these measurements shall yield quantitative relationships between the sea state (mainly driven by the surface wind and the swell and the overall DDM shape. The ultimate goal is to use the DDM shape to correct the sea state influence on the L-band brightness temperature to improve the retrieval of the sea surface salinity (SSS.

Progress Report on the GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height) Research Project

Science.gov (United States)

Kitazawa, Y.; Ichikawa, K.; Akiyama, H.; Ebinuma, T.; Isoguchi, O.; Kimura, N.; Konda, M.; Kouguchi, N.; Tamura, H.; Tomita, H.; Yoshikawa, Y.; Waseda, T.

2016-12-01

Global Navigation Satellite Systems (GNSS), such as GPS is a system of satellites that provide autonomous geo-spatial positioning with global coverage. It allows small electronic receivers to determine their location to high precision using radio signals transmitted from satellites, GNSS reflectometry (GNSS-R) involves making measurements from the reflections from the Earth of navigation signals from GNSS satellites. Reflected signals from sea surface are considered that those are useful to observe sea state and sea surface height. We have started a research program for GNSS-R applications on oceanographic observations under the contract with MEXT (Ministry of Education Culture, Sports, Science and Technology, JAPAN) and launched a Japanese research consortium, GROWTH (GNSS Reflectometry for Ocean Waves, Tides, and Height). It is aiming to evaluate the capabilities of GNSS-R observations for oceanographic phenomena with different time scales, such as ocean waves (1/10 to tens of seconds), tides (one or half days), and sea surface dynamic height (a few days to years). In situ observations of ocean wave spectrum, wind speed vertical profile, and sea surface height will be quantitatively compared with equivalent estimates from simultaneous GNSS-R measurements. The GROWTH project will utilize different types of observation platforms; marine observation towers (about 20 m height), multi-copters (about 100 to 150 m height), and much higher-altitude CYGNSS data. Cross-platform data, together with in situ oceanographic observations, will be compared after adequate temporal averaging that accounts differences of the footprint sizes and temporal and spatial scales of oceanographic phenomena. This paper will provide overview of the GROWTH project, preliminary test results, obtained by the multi-sensor platform at observation towers, suggest actual footprint sizes and identification of swell. Preparation status of a ground station which will be supplied to receive CYGNSS data

GNSS-Reflectometry based water level monitoring

Science.gov (United States)

Beckheinrich, Jamila; Schön, Steffen; Beyerle, Georg; Apel, Heiko; Semmling, Maximilian; Wickert, Jens

2013-04-01

Due to climate changing conditions severe changes in the Mekong delta in Vietnam have been recorded in the last years. The goal of the German Vietnamese WISDOM (Water-related Information system for the Sustainable Development Of the Mekong Delta) project is to build an information system to support and assist the decision makers, planners and authorities for an optimized water and land management. One of WISDOM's tasks is the flood monitoring of the Mekong delta. Earth reflected L-band signals from the Global Navigation Satellite System show a high reflectivity on water and ice surfaces or on wet soil so that GNSS-Reflectometry (GNSS-R) could contribute to monitor the water level in the main streams of the Mekong delta complementary to already existing monitoring networks. In principle, two different GNSS-R methods exist: the code- and the phase-based one. As the latter being more accurate, a new generation of GORS (GNSS Occultation, Reflectometry and Scatterometry) JAVAD DELTA GNSS receiver has been developed with the aim to extract precise phase observations. In a two week lasting measurement campaign, the receiver has been tested and several reflection events at the 150-200 m wide Can Tho river in Vietnam have been recorded. To analyze the geometrical impact on the quantity and quality of the reflection traces two different antennas height were tested. To track separately the direct and the reflected signal, two antennas were used. To derive an average height of the water level, for a 15 min observation interval, a phase model has been developed. Combined with the coherent observations, the minimum slope has been calculated based on the Least- Squares method. As cycle slips and outliers will impair the results, a preprocessing of the data has been performed. A cycle slip detection strategy that allows for automatic detection, identification and correction is proposed. To identify outliers, the data snooping method developed by Baarda 1968 is used. In this

Monocular Camera/IMU/GNSS Integration for Ground Vehicle Navigation in Challenging GNSS Environments

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Dennis Akos

2012-03-01

Full Text Available Low-cost MEMS-based IMUs, video cameras and portable GNSS devices are commercially available for automotive applications and some manufacturers have already integrated such facilities into their vehicle systems. GNSS provides positioning, navigation and timing solutions to users worldwide. However, signal attenuation, reflections or blockages may give rise to positioning difficulties. As opposed to GNSS, a generic IMU, which is independent of electromagnetic wave reception, can calculate a high-bandwidth navigation solution, however the output from a self-contained IMU accumulates errors over time. In addition, video cameras also possess great potential as alternate sensors in the navigation community, particularly in challenging GNSS environments and are becoming more common as options in vehicles. Aiming at taking advantage of these existing onboard technologies for ground vehicle navigation in challenging environments, this paper develops an integrated camera/IMU/GNSS system based on the extended Kalman filter (EKF. Our proposed integration architecture is examined using a live dataset collected in an operational traffic environment. The experimental results demonstrate that the proposed integrated system provides accurate estimations and potentially outperforms the tightly coupled GNSS/IMU integration in challenging environments with sparse GNSS observations.

Monocular camera/IMU/GNSS integration for ground vehicle navigation in challenging GNSS environments.

Science.gov (United States)

Chu, Tianxing; Guo, Ningyan; Backén, Staffan; Akos, Dennis

2012-01-01

Low-cost MEMS-based IMUs, video cameras and portable GNSS devices are commercially available for automotive applications and some manufacturers have already integrated such facilities into their vehicle systems. GNSS provides positioning, navigation and timing solutions to users worldwide. However, signal attenuation, reflections or blockages may give rise to positioning difficulties. As opposed to GNSS, a generic IMU, which is independent of electromagnetic wave reception, can calculate a high-bandwidth navigation solution, however the output from a self-contained IMU accumulates errors over time. In addition, video cameras also possess great potential as alternate sensors in the navigation community, particularly in challenging GNSS environments and are becoming more common as options in vehicles. Aiming at taking advantage of these existing onboard technologies for ground vehicle navigation in challenging environments, this paper develops an integrated camera/IMU/GNSS system based on the extended Kalman filter (EKF). Our proposed integration architecture is examined using a live dataset collected in an operational traffic environment. The experimental results demonstrate that the proposed integrated system provides accurate estimations and potentially outperforms the tightly coupled GNSS/IMU integration in challenging environments with sparse GNSS observations.

Monocular Camera/IMU/GNSS Integration for Ground Vehicle Navigation in Challenging GNSS Environments

Science.gov (United States)

Chu, Tianxing; Guo, Ningyan; Backén, Staffan; Akos, Dennis

2012-01-01

Low-cost MEMS-based IMUs, video cameras and portable GNSS devices are commercially available for automotive applications and some manufacturers have already integrated such facilities into their vehicle systems. GNSS provides positioning, navigation and timing solutions to users worldwide. However, signal attenuation, reflections or blockages may give rise to positioning difficulties. As opposed to GNSS, a generic IMU, which is independent of electromagnetic wave reception, can calculate a high-bandwidth navigation solution, however the output from a self-contained IMU accumulates errors over time. In addition, video cameras also possess great potential as alternate sensors in the navigation community, particularly in challenging GNSS environments and are becoming more common as options in vehicles. Aiming at taking advantage of these existing onboard technologies for ground vehicle navigation in challenging environments, this paper develops an integrated camera/IMU/GNSS system based on the extended Kalman filter (EKF). Our proposed integration architecture is examined using a live dataset collected in an operational traffic environment. The experimental results demonstrate that the proposed integrated system provides accurate estimations and potentially outperforms the tightly coupled GNSS/IMU integration in challenging environments with sparse GNSS observations. PMID:22736999

Fusão INS/GNSS com auxílio de medidas de baseline e ângulo GNSS

OpenAIRE

Priscylla Angélica da Silva Oliveira

2014-01-01

Este trabalho investiga sistemas de navegação INS/GNSS auxiliado por medidas de baseline e ângulo GNSS. Os dados gerados para as simulações foram os dados IMU, dados GNSS e informações de baseline e ângulo GNSS. Estas informações, determinadas a partir de um sistema multiantenas para o posicionamento simples e relativo e no método direto, respectivamente, foram utilizadas como medidas auxiliares para a fusão INS/GNSS. Foi estudada a influência dessas medidas auxiliares nas estimativas de atit...

First spaceborne phase altimetry over sea ice using TechDemoSat-1 GNSS-R signals

Science.gov (United States)

Li, Weiqiang; Cardellach, Estel; Fabra, Fran; Rius, Antonio; Ribó, Serni; Martín-Neira, Manuel

2017-08-01

A track of sea ice reflected Global Navigation Satellite System (GNSS) signal collected by the TechDemoSat-1 mission is processed to perform phase altimetry over sea ice. High-precision carrier phase measurements are extracted from coherent GNSS reflections at a high angle of elevation (>57°). The altimetric results show good consistency with a mean sea surface (MSS) model, and the root-mean-square difference is 4.7 cm with an along-track sampling distance of ˜140 m and a spatial resolution of ˜400 m. The difference observed between the altimetric results and the MSS shows good correlation with the colocated sea ice thickness data from Soil Moisture and Ocean Salinity. This is consistent with the reflecting surface aligned with the bottom of the ice-water interface, due to the penetration of the GNSS signal into the sea ice. Therefore, these high-precision altimetric results have potential to be used for determination of sea ice thickness.

3Cat-3/MOTS Nanosatellite Mission for Optical Multispectral and GNSS-R Earth Observation: Concept and Analysis

OpenAIRE

Castellví, Jordi; Camps, Adriano; Corbera, Jordi; Alamús, Ramon

2018-01-01

The 3Cat-3/MOTS (3: Cube, Cat: Catalunya, 3: 3rd CubeSat mission/Missió Observació Terra Satèl·lit) mission is a joint initiative between the Institut Cartogràfic i Geològic de Catalunya (ICGC) and the Universitat Politècnica de Catalunya-BarcelonaTech (UPC) to foster innovative Earth Observation (EO) techniques based on data fusion of Global Navigation Satellite Systems Reflectometry (GNSS-R) and optical payloads. It is based on a 6U CubeSat platform, roughly a 10 cm × 20 cm × 30 cm parallel...

Overview of new GNSS tropospheric products for GNSS-meteorology and their assessment at Geodetic Observatory Pecny (CZ)

Science.gov (United States)

Dousa, J.; Vaclavovic, P.; Gyori, G.

2012-12-01

Geodetic Observatory Pecný (GOP) has a long-term experience in the estimation of precise tropospheric parameters from GNSS permanent stations, in particular under the limited timelines of near real time. More than a decade, the GOP zenith total delays (ZTD) contributed to various projects in Europe (COST-716, TOUGH, E-GVAP, E-GVAP II) and the operational ZTD hourly updated product flows via the meteorological observation exchange network - GTS - to the end users worldwide. Currently, the GOP regional ZTD product is operationally assimilated in Météo France and UK MetOffice at least and further exploited in various ways at many other meteorological institutions. New developments at GOP over last three years consist of a) implementation and assessment of the global hourly ZTD product of about 170 stations, b) implementation of routine multi-GNSS (GPS+GLONASS) ZTD European product, and c) implementation of ultra-fast/real-time ZTD product. The GOP global ZTD product has been implemented on request of the meteorological institutions running global numerical weather forecasting models. The global ZTD product was seriously evaluated over ten months (Oct 2009 - Aug 2011) when compared to reprocessed EUREF and IGS ZTDs, radiosondes and ZTDs derived from UK MetOffice's global numerical weather model. After the evaluation (and on special request of UK MetOffice) the product has been switched from testing to operational status within the framework of the EUMETNET EIG GPS Water Vapour Programme (E-GVAP) and officially disseminated via the GTS network. The GOP multi-GNSS ZTD solution has been tested since 2009 shortly after developing GOP ultra-rapid GPS+GLONASS orbits for the International GNSS Service (IGS). A specific bias of mean value 1.5 mm was identified between GPS- and GLONASS-only ZTD at that time, and relation to the IGS05 antenna phase centre offset and variation models (PCO+PCV) identified. Consequently, the implementation of a routine operation has been done

Evoluzione dei sistemi GNSS

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Gianluca Pititto

2010-03-01

Full Text Available Evolution of GNSS systems With this article GEOmedia is starting a review on the latest updates concerning GNSS technology. Since the first GPS satellites, the evolution of GNSS sector witnessed the grow of other constellations: GLONASS, Beidou (Compass and Galileo. The development of positioning techniques even brought to the creation of specific Augmentation Systems, capable of the enhancement of the localization signals (GBAS and SBAS. The aim of this review is to provide a general-to-particular knowledge of all the positiong and augmentation systems, from a historical point of view to real applications.

Coastal Sea Level and Estuary Tide Modeling in Bangladesh Using SAR, Radar and GNSS-R Altimetry

Science.gov (United States)

Jia, Y.; Shum, C. K.; Sun, J.; Li, D.; Shang, K.; Yi, Y.; Calmant, S.; Ballu, V.; Chu, P.; Johnson, J.; Park, J.; Bao, L.; Kuo, C. Y.; Wickert, J.

2017-12-01

Bangladesh, located at the confluence of three large rivers - Ganges, Brahmaputra and Meghna, is a low-lying country. It is prone to monsoonal flooding, potentially aggravated by more frequent and intensified cyclones resulting from anthropogenic climate change. Its coastal estuaries, the Sundarbans wetlands, have the largest Mangrove forest in the world, and exhibits complex tidal dynamics. In order to study flood hazards, ecological or climate changes over floodplains, it is fundamentally important to know the water level and water storage capacity in wetlands. Inaccurate or inadequate information about wetland water storage will cause significant errors in hydrological simulation and modeling for understanding ecological and economic implications. However, in most areas, the exact knowledge of water level change and the flow patterns is lacking due to insufficient monitoring of water level gauging stations on private and public lands within wetlands or floodplains, due to the difficulty of physical access to the sites and logistics in data gathering. Usage of satellite all-weather remote sensing products provides an alternative approach for monitoring the water level variation over floodplains or wetlands. In this study, we used a combination of observations from satellite radar altimetry (Envisat/Jason-2/Altika/Sentinel-3), L-band synthetic aperture radar (ALOS-1/-2) backscattering coefficients inferred water level, GNSS-R altimetry from two coastal/river GNSS sites, for measuring coastal and estuary sea-level and conducting estuary ocean tide modeling in the Bangladesh delta including the Sundarbans wetlands.

GNSS Software Receiver for UAVs

DEFF Research Database (Denmark)

Olesen, Daniel Madelung; Jakobsen, Jakob; von Benzon, Hans-Henrik

2016-01-01

This paper describes the current activities of GPS/GNSS Software receiver development at DTU Space. GNSS Software receivers have received a great deal of attention in the last two decades and numerous implementations have already been presented. DTU Space has just recently started development of ...... of our own GNSS software-receiver targeted for mini UAV applications, and we will in in this paper present our current progress and briefly discuss the benefits of Software Receivers in relation to our research interests....

Simulation of space-borne tsunami detection using GNSS-Reflectometry applied to tsunamis in the Indian Ocean

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R. Stosius

2010-06-01

Full Text Available Within the German-Indonesian Tsunami Early Warning System project GITEWS (Rudloff et al., 2009, a feasibility study on a future tsunami detection system from space has been carried out. The Global Navigation Satellite System Reflectometry (GNSS-R is an innovative way of using reflected GNSS signals for remote sensing, e.g. sea surface altimetry. In contrast to conventional satellite radar altimetry, multiple height measurements within a wide field of view can be made simultaneously. With a dedicated Low Earth Orbit (LEO constellation of satellites equipped with GNSS-R, densely spaced sea surface height measurements could be established to detect tsunamis. This simulation study compares the Walker and the meshed comb constellation with respect to their global reflection point distribution. The detection performance of various LEO constellation scenarios with GPS, GLONASS and Galileo as signal sources is investigated. The study concentrates on the detection performance for six historic tsunami events in the Indian Ocean generated by earthquakes of different magnitudes, as well as on different constellation types and orbit parameters. The GNSS-R carrier phase is compared with the PARIS or code altimetry approach. The study shows that Walker constellations have a much better reflection point distribution compared to the meshed comb constellation. Considering simulation assumptions and assuming technical feasibility it can be demonstrated that strong tsunamis with magnitudes (M ≥8.5 can be detected with certainty from any orbit altitude within 15–25 min by a 48/8 or 81/9 Walker constellation if tsunami waves of 20 cm or higher can be detected by space-borne GNSS-R. The carrier phase approach outperforms the PARIS altimetry approach especially at low orbit altitudes and for a low number of LEO satellites.

Estimating the Geocenter from GNSS Observations

Science.gov (United States)

Dach, Rolf; Michael, Meindl; Beutler, Gerhard; Schaer, Stefan; Lutz, Simon; Jäggi, Adrian

2014-05-01

The satellites of the Global Navigation Satellite Systems (GNSS) are orbiting the Earth according to the laws of celestial mechanics. As a consequence, the satellites are sensitive to the coordinates of the center of mass of the Earth. The coordinates of the (ground) tracking stations are referring to the center of figure as the conventional origin of the reference frame. The difference between the center of mass and center of figure is the instantaneous geocenter. Following this definition the global GNSS solutions are sensitive to the geocenter. Several studies demonstrated strong correlations of the GNSS-derived geocenter coordinates with parameters intended to absorb radiation pressure effects acting on the GNSS satellites, and with GNSS satellite clock parameters. One should thus pose the question to what extent these satellite-related parameters absorb (or hide) the geocenter information. A clean simulation study has been performed to answer this question. The simulation environment allows it in particular to introduce user-defined shifts of the geocenter (systematic inconsistencies between the satellite's and station's reference frames). These geocenter shifts may be recovered by the mentioned parameters - provided they were set up in the analysis. If the geocenter coordinates are not estimated, one may find out which other parameters absorb the user-defined shifts of the geocenter and to what extent. Furthermore, the simulation environment also allows it to extract the correlation matrix from the a posteriori covariance matrix to study the correlations between different parameter types of the GNSS analysis system. Our results show high degrees of correlations between geocenter coordinates, orbit-related parameters, and satellite clock parameters. These correlations are of the same order of magnitude as the correlations between station heights, troposphere, and receiver clock parameters in each regional or global GNSS network analysis. If such correlations

High Precision GNSS Guidance for Field Mobile Robots

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Ladislav Jurišica

2012-11-01

Full Text Available In this paper, we discuss GNSS (Global Navigation Satellite System guidance for field mobile robots. Several GNSS systems and receivers, as well as multiple measurement methods and principles of GNSS systems are examined. We focus mainly on sources of errors and investigate diverse approaches for precise measuring and effective use of GNSS systems for real-time robot localization. The main body of the article compares two GNSS receivers and their measurement methods. We design, implement and evaluate several mathematical methods for precise robot localization.

Investigation of the Air Quality Change Effect on Gnss Signals

Science.gov (United States)

Gurbuz, G.; Gormus, K. S.; Altan, U.

2017-11-01

Air pollution is the most important environmental problem in Zonguldak city center. Since bituminous coal is used for domestic heating in houses and generating electricity in thermal power plants, particulate matter (PM10) is the leading air pollutant. Previous studies have shown that the water vapor in the troposphere is responsible for the tropospheric zenith delay in Global Navigation Satellite System (GNSS) measurements. In this study, data obtained from the ZONG GNSS station from Türkiye Ulusal Sabit GNSS Ağı (TUSAGA-Active network) in the central district of Zonguldak province, processed with GIPSY-OASIS II and GAMIT/GlobK software using the VMF1 mapping function, which is developed previously and considered to be the most accurate model. The resulting values were examined separately in terms of software. The meteorological parameters obtained from the Turkish State Meteorological Service and the air pollution values obtained from the Ministry of Environment and Urban Planning were analyzed and the zenith delay values were compared. When wet zenith delays of different days with different amounts of PM10 concentrations were examined in succession and under the same meteorological conditions, differences in the range of 20-40 mm on ZTD were observed.

THE PERFORMANCE OF A TIGHT INS/GNSS/PHOTOGRAMMETRIC INTEGRATION SCHEME FOR LAND BASED MMS APPLICATIONS IN GNSS DENIED ENVIRONMENTS

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C. H. Chu

2012-07-01

Full Text Available Nowadays the most common technologies used for positioning and orientation of a mobile mapping system include using Global Navigation Satellite System (GNSS as a major positioning sensor and Inertial Navigation System (INS as the major orientation sensor. The integration strategy of the most commercially system is the loosely coupled (LC architecture, that has the simplest architecture using the GNSS solutions to aid the INS navigation information with proper optimization estimator. The LC does combine the two sensors’ solutions when the number of tracked satellite is more than four. In recent year, another commonly integration strategy is known as tightly coupled (TC architecture. Because the TC uses the GNSS measurements to aid INS, it can integrate measurements provided by GNSS receiver and INS unless no GNSS satellite is tracked. Obviously, the TC architecture is a better candidate for land based mobile mapping applications than LC in Taiwan. Unfortunately, there are still many GNSS denied environment in the urban area, therefore the TC architecture is still not robust and stable enough for MMS application. The overall objective of this paper is to provide a scheme that tightly integrates INS/GNSS and Photogrammetric for land based MMS applications with sufficient and stable POS solutions during GNSS outages. In the traditional photogrammetry operation, numerous ground control points are applied to compute those Exterior Orientation Parameters (EOPs of cameras by bundle adjustment. The key opinion is to derive the INS centre position and attitude and reconstruct 3-D tracking and 3-D object space by cameras EOPs. The proposed algorithm is verified using field test data collected in GNSS denied environments and the preliminary results presented in this study illustrated that the proposed algorithm is able to provide 60% improvement in terms of positioning and orientation accuracy in Taipei and Tainan cities.

The Performance of a Tight Ins/gnss/photogrammetric Integration Scheme for Land Based MMS Applications in Gnss Denied Environments

Science.gov (United States)

Chu, C. H.; Chiang, K. W.

2012-07-01

Nowadays the most common technologies used for positioning and orientation of a mobile mapping system include using Global Navigation Satellite System (GNSS) as a major positioning sensor and Inertial Navigation System (INS) as the major orientation sensor. The integration strategy of the most commercially system is the loosely coupled (LC) architecture, that has the simplest architecture using the GNSS solutions to aid the INS navigation information with proper optimization estimator. The LC does combine the two sensors' solutions when the number of tracked satellite is more than four. In recent year, another commonly integration strategy is known as tightly coupled (TC) architecture. Because the TC uses the GNSS measurements to aid INS, it can integrate measurements provided by GNSS receiver and INS unless no GNSS satellite is tracked. Obviously, the TC architecture is a better candidate for land based mobile mapping applications than LC in Taiwan. Unfortunately, there are still many GNSS denied environment in the urban area, therefore the TC architecture is still not robust and stable enough for MMS application. The overall objective of this paper is to provide a scheme that tightly integrates INS/GNSS and Photogrammetric for land based MMS applications with sufficient and stable POS solutions during GNSS outages. In the traditional photogrammetry operation, numerous ground control points are applied to compute those Exterior Orientation Parameters (EOPs) of cameras by bundle adjustment. The key opinion is to derive the INS centre position and attitude and reconstruct 3-D tracking and 3-D object space by cameras EOPs. The proposed algorithm is verified using field test data collected in GNSS denied environments and the preliminary results presented in this study illustrated that the proposed algorithm is able to provide 60% improvement in terms of positioning and orientation accuracy in Taipei and Tainan cities.

Quality Improvement of the Satellite Soil Moisture Products by Fusing In Situ and GNSS-R Observation

Science.gov (United States)

Yuan, Q.; Xu, H.; Li, T.; Shen, H.; Zhang, L.

2017-12-01

Soil moisture plays a fundamental role in the hydrological cycle as well as in the energy partitioning. On this basis, it is of great concern to derive a long-term soil moisture time series on a global scale and monitor its temporal and spatial variations for practical applications. Although passive and active microwave satellites have been shown to provide useful retrievals of near-surface soil moisture at regional and global scales, the limitations in retrieval accuracy prevent them from high-quality applications in specific areas. On the other hand, measuring soil moisture straightly through in situdevices, such as soil moisture probes, is high accuracy, but is not able to derive global soil moisture maps. Recently, the ground-based GNSS-R method is emerging in monitoring near-surface soil moisture variations but still over limited spatial scales. In this paper, a multi-source data fusion method was applied to synthesize regional high-quality soil moisture products from 2015 to 2017 in western parts of the continental United States. Firstly, we put all the three soil moisture datasets into the generalized regression neural network (GRNN) model. The input signals of the model are SMOS and SMAP satellite-derived passive level 3 soil moisture daily products combined with date and latitude and longitude information, while the in situ measured and GNSS-R retrieved soil moisture are used as target. Finally, we apply the model to all the soil moisture time series in the experiment area and obtain two high-quality regional soil moisture products for SMOS and SMAP, respectively. The results before fusion show that the correlation coefficients between site-specific soil moisture and satellite-derived soil moisture are 0.39 for SMOS and 0.27 for SMAP and that unbiased root-mean-square errors (ubRMSE) are 0.113 for SMOS and 0.128 for SMAP, respectively. After applying the GRNN-R, the model fitted correlation coefficients have reached 0.72 for SMOS and 0.75 for SMAP and the

INVESTIGATION OF THE AIR QUALITY CHANGE EFFECT ON GNSS SIGNALS

Directory of Open Access Journals (Sweden)

G. Gurbuz

2017-11-01

Full Text Available Air pollution is the most important environmental problem in Zonguldak city center. Since bituminous coal is used for domestic heating in houses and generating electricity in thermal power plants, particulate matter (PM10 is the leading air pollutant. Previous studies have shown that the water vapor in the troposphere is responsible for the tropospheric zenith delay in Global Navigation Satellite System (GNSS measurements. In this study, data obtained from the ZONG GNSS station from Türkiye Ulusal Sabit GNSS Ağı (TUSAGA-Active network in the central district of Zonguldak province, processed with GIPSY-OASIS II and GAMIT/GlobK software using the VMF1 mapping function, which is developed previously and considered to be the most accurate model. The resulting values were examined separately in terms of software. The meteorological parameters obtained from the Turkish State Meteorological Service and the air pollution values obtained from the Ministry of Environment and Urban Planning were analyzed and the zenith delay values were compared. When wet zenith delays of different days with different amounts of PM10 concentrations were examined in succession and under the same meteorological conditions, differences in the range of 20–40 mm on ZTD were observed.

Deep Coupled Integration of CSAC and GNSS for Robust PNT

Directory of Open Access Journals (Sweden)

Lin Ma

2015-09-01

Full Text Available Global navigation satellite systems (GNSS are the most widely used positioning, navigation, and timing (PNT technology. However, a GNSS cannot provide effective PNT services in physical blocks, such as in a natural canyon, canyon city, underground, underwater, and indoors. With the development of micro-electromechanical system (MEMS technology, the chip scale atomic clock (CSAC gradually matures, and performance is constantly improved. A deep coupled integration of CSAC and GNSS is explored in this thesis to enhance PNT robustness. “Clock coasting” of CSAC provides time synchronized with GNSS and optimizes navigation equations. However, errors of clock coasting increase over time and can be corrected by GNSS time, which is stable but noisy. In this paper, weighted linear optimal estimation algorithm is used for CSAC-aided GNSS, while Kalman filter is used for GNSS-corrected CSAC. Simulations of the model are conducted, and field tests are carried out. Dilution of precision can be improved by integration. Integration is more accurate than traditional GNSS. When only three satellites are visible, the integration still works, whereas the traditional method fails. The deep coupled integration of CSAC and GNSS can improve the accuracy, reliability, and availability of PNT.

Deep Coupled Integration of CSAC and GNSS for Robust PNT.

Science.gov (United States)

Ma, Lin; You, Zheng; Li, Bin; Zhou, Bin; Han, Runqi

2015-09-11

Global navigation satellite systems (GNSS) are the most widely used positioning, navigation, and timing (PNT) technology. However, a GNSS cannot provide effective PNT services in physical blocks, such as in a natural canyon, canyon city, underground, underwater, and indoors. With the development of micro-electromechanical system (MEMS) technology, the chip scale atomic clock (CSAC) gradually matures, and performance is constantly improved. A deep coupled integration of CSAC and GNSS is explored in this thesis to enhance PNT robustness. "Clock coasting" of CSAC provides time synchronized with GNSS and optimizes navigation equations. However, errors of clock coasting increase over time and can be corrected by GNSS time, which is stable but noisy. In this paper, weighted linear optimal estimation algorithm is used for CSAC-aided GNSS, while Kalman filter is used for GNSS-corrected CSAC. Simulations of the model are conducted, and field tests are carried out. Dilution of precision can be improved by integration. Integration is more accurate than traditional GNSS. When only three satellites are visible, the integration still works, whereas the traditional method fails. The deep coupled integration of CSAC and GNSS can improve the accuracy, reliability, and availability of PNT.

Preparing the Plate Boundary Observatory GNSS Network for the Future

Science.gov (United States)

Austin, K. E.; Walls, C. P.; Dittman, T.; Mann, D.; Boyce, E. S.; Basset, A.; Woolace, A. C.; Turner, R.; Lawrence, S.; Rhoades, S.; Pyatt, C.; Willoughby, H.; Feaux, K.; Mattioli, G. S.

2017-12-01

The EarthScope Plate Boundary Observatory (PBO) GNSS network, funded by the NSF and operated by UNAVCO, is comprised of 1100 permanent GPS and GNSS stations spanning three principal tectonic regimes and is administered by distinct management. The GPS-only network was initially designed for daily data file downloads primarily for tectonic analysis. This low data volume requirement and circa-2004 IP-based cellular/VSat modems provided significant freedom for station placement and enabled science-targeted installation of stations in some of the most remote and geologically interesting areas. Community requests for high-rate data downloads for GNSS seismology, airborne LiDAR surveys, meteorological/GNSS/seismic real-time data flow and other demands, however, require significantly increased bandwidth beyond the 5-20 kB/s transfer rates that were needed as part of the original design. Since the close of construction in September 2008, PBO enhancements have been implemented through additional funding by the NSF (ARRA/Cascadia), NOAA, and NASA and in collaboration with stakeholders such as Caltrans, ODOT, Scripps, and the USGS. Today, only 18 of the original cell modems remain, with 601 upgraded cell modems providing 3G/4G/LTE data communications that support transfer rates ranging from 80-400 kB/s. Radio network expansion and upgrades continue to harden communications using both 2.4 GHz and 5.8 GHz radios. 78 VSAT and 5 manual download sites remain. PBO-wide the network capabilities for 1 Hz & 5 Hz downloads or low latency 1 Hz streaming are 85%, 80% and 65% of PBO stations, respectively, with 708 active 1 Hz streams. Vaisala meteorological instruments are located at 140 sites most of which stream GPS/Met data in real time. GPS-only receivers are being replaced with GNSS receivers and antennas. Today, there are 279 stations in the PBO network with either GLONASS enabled Trimble NetR9 or full GNSS constellation Septentrio PolaRx5 receivers. Just as the scale and

Gnss Geodetic Monitoring as Support of Geodynamics Research in Colombia, South America

Science.gov (United States)

Mora-Paez, H.; Acero-Patino, N.; Rodriguez-Zuluaga, J. S.; Diederix, H.; Bohorquez-Orozco, O. P.; Martinez-Diaz, G. P.; Diaz-Mila, F.; Giraldo-Londono, L. S.; Cardozo-Giraldo, S.; Vasquez-Ospina, A. F.; Lizarazo, S. C.

2013-05-01

To support the geodynamics research at the northwestern corner of South America, GEORED, the acronym for "Geodesia: Red de Estudios de Deformación" has been adopted for the Project "Implementation of the National GNSS Network for Geodynamics" carried out by the Colombian Geological Survey, (SGC), formerly INGEOMINAS. Beginning in 2007, discussions within the GEORED group led to a master plan for the distribution of the base permanent GPS/GNSS station array and specific areas of interest for campaign site construction. The use of previously identified active faults as preferred structures along which stresses are transferred through the deformational area led to the idea of segmentation of the North Andes within Colombia into 20 tectonic sub-blocks. Each of the 20 sub-blocks is expected to have, at least, three-four permanent GPS/GNSS stations within the block along with construction of campaign sites along the boundaries. Currently, the GEORED Network is managing 46 continuously including: 40 GEORED GPS/GNSS continuously operating stations; 4 GNSS continuously operating stations provided by the COCONet (Continuously Operating Caribbean GPS Observational Network) Project; the Bogotá IGS GPS station (BOGT), installed in 1994 under the agreement between JPL-NASA and the SGC; and the San Andres Island station, installed in 2007 under the MOU between UCAR and the SGC. In addition to the permanent installations, more than 230 GPS campaign sites have been constructed and are being occupied one time per year. The Authority of the Panama Canal and the Escuela Politecnica de Quito have also provided data of 4 and 5 GPS/GNSS stations respectively. The GPS data are processed using the GIPSY-OASIS II software, and the GPS time series of daily station positions give fundamental information for both regional and local geodynamics studies. Until now, we have obtained 100 quality vector velocities for Colombia, 23 of them as part of the permanent network. The GPS/GNSS stations

Crustal block motion model and interplate coupling along Ecuador-Colombia trench based on GNSS observation network

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Ito, T.; Mora-Páez, H.; Peláez-Gaviria, J. R.; Kimura, H.; Sagiya, T.

2017-12-01

IntroductionEcuador-Colombia trench is located at the boundary between South-America plate, Nazca Plate and Caribrian plate. This region is very complexes such as subducting Caribrian plate and Nazca plate, and collision between Panama and northern part of the Andes mountains. The previous large earthquakes occurred along the subducting boundary of Nazca plate, such as 1906 (M8.8) and 1979 (M8.2). And also, earthquakes occurred inland, too. So, it is important to evaluate earthquake potentials for preparing huge damage due to large earthquake in near future. GNSS observation In the last decade, the GNSS observation was established in Columbia. The GNSS observation is called by GEORED, which is operated by servicing Geologico Colomiano. The purpose of GEORED is research of crustal deformation. The number of GNSS site of GEORED is consist of 60 continuous GNSS observation site at 2017 (Mora et al., 2017). The sampling interval of almost GNSS site is 30 seconds. These GNSS data were processed by PPP processing using GIPSY-OASYS II software. GEORED can obtain the detailed crustal deformation map in whole Colombia. In addition, we use 100 GNSS data at Ecuador-Peru region (Nocquet et al. 2014). Method We developed a crustal block movements model based on crustal deformation derived from GNSS observation. Our model considers to the block motion with pole location and angular velocity and the interplate coupling between each block boundaries, including subduction between the South-American plate and the Nazca plate. And also, our approach of estimation of crustal block motion and coefficient of interplate coupling are based on MCMC method. The estimated each parameter is obtained probably density function (PDF). Result We tested 11 crustal block models based on geological data, such as active fault trace at surface. The optimal number of crustal blocks is 11 for based on geological and geodetic data using AIC. We use optimal block motion model. And also, we estimate

Tropospheric Delay from VLBI and GNSS Measurements

Science.gov (United States)

Gubanov, V. S.

2018-02-01

Using an updated version of the QUASAR software package developed at the Institute of Applied Astronomy of the Russian Academy of Sciences, we have processed the VLBI observations within the international CONT14 program (May 6-20, 2014), in which a global network of 17 stations was involved (a total of 250 000 observations). The package update concerned the optimization of data structure and the refinement of stochastic models for the random variations in wet tropospheric delay and atomic clock difference. The main goal of this paper is to compare the VLBI determinations of the tropospheric delay with its independent determinations using global navigation satellite systems (GNSS). We show that both these determinations agree well between themselves only in the case of a global analysis of the VLBI observations, where the VLBI station coordinates are also refined, along with the tropospheric delay and the clock synchronization and Earth orientation parameters. If, alternatively, the station coordinates are insufficiently accurate and are not refined from VLBI observations, then it is appropriate not to determine the tropospheric delay from these observations, but to take it from the publicly accessible independent GNSS data. However, this requires that the VLBI and GNSS techniques operate simultaneously at a common observing site. We have established the shortcomings of the universally accepted method of stabilizing the global solution associated with the absence of a criterion for choosing reference stations and radio sources. Two ways of their elimination are proposed: (i) introducing a coordinated list of weight factors for the errors in the coordinates of such stations and sources into the stabilization algorithm and (ii) adopting a coordinated list of stations and sources the refinement of whose coordinates is not required at all for a certain time.

GNSS CORS hardware and software enabling new science

Science.gov (United States)

Drummond, P.

2009-12-01

GNSS CORS networks are enabling new opportunities for science and public and private sector business. This paper will explore how the newest geodetic monitoring software and GNSS receiver hardware from Trimble Navigation Ltd are enabling new science. Technology trends and science opportunities will be explored. These trends include the installation of active GNSS control, automation of observations and processing, and the advantages of multi-observable and multi-constellation observations, all performed with the use of off the shelf products and industry standard open-source data formats. Also the possibilities with moving science from an after-the-fact postprocessed model to a real-time epoch-by-epoch solution will be explored. This presentation will also discuss the combination of existing GNSS CORS networks with project specific installations used for monitoring. Experience is showing GNSS is able to provide higher resolution data than previous methods, providing new tools for science, decision makers and financial planners.

Assessment of local GNSS baselines at co-location sites

Science.gov (United States)

Herrera Pinzón, Iván; Rothacher, Markus

2018-01-01

As one of the major contributors to the realisation of the International Terrestrial Reference System (ITRS), the Global Navigation Satellite Systems (GNSS) are prone to suffer from irregularities and discontinuities in time series. While often associated with hardware/software changes and the influence of the local environment, these discrepancies constitute a major threat for ITRS realisations. Co-located GNSS at fundamental sites, with two or more available instruments, provide the opportunity to mitigate their influence while improving the accuracy of estimated positions by examining data breaks, local biases, deformations, time-dependent variations and the comparison of GNSS baselines with existing local tie measurements. With the use of co-located GNSS data from a subset sites of the International GNSS Service network, this paper discusses a global multi-year analysis with the aim of delivering homogeneous time series of coordinates to analyse system-specific error sources in the local baselines. Results based on the comparison of different GNSS-based solutions with the local survey ties show discrepancies of up to 10 mm despite GNSS coordinate repeatabilities at the sub-mm level. The discrepancies are especially large for the solutions using the ionosphere-free linear combination and estimating tropospheric zenith delays, thus corresponding to the processing strategy used for global solutions. Snow on the antennas causes further problems and seasonal variations of the station coordinates. These demonstrate the need for a permanent high-quality monitoring of the effects present in the short GNSS baselines at fundamental sites.

Global Navigation Satellite Systems (GNSS: The Utmost Interdisciplinary Integrator

Directory of Open Access Journals (Sweden)

Bernd Eissfeller

2015-08-01

Full Text Available Currently four global satellite navigation systems are under modernization and development: The US American GPS III, the Russian GLONASS, the European Galileo and Chinese BeiDou systems. In the paper the interdisciplinary contributions of different scientific areas to GNSS are assessed. It is outlined that GNSS is not only a technical system but also a basic element of mobile computing high-tech market. At the same time a GNSS has the role of a force enabler in security related applications. Technology, market and security policies are interdependent and are sometimes in a relationship of tension. The goal of the paper is to describe the overall systemics of GNSS from a holistic point of view. The paper also addresses the human factor side of GNSS. The requirements on human resources in GNSS are at least two-fold: On the one hand very specialized engineers are needed; on the other hand the generalists are necessary who are able to understand the system aspects. Decision makers in institutions and industry need special knowledge in technologies, economics and political strategies. Is the current university system able to educate and prepare such generalists? Are specialized master courses for GNSS needed? Are external training courses necessary?

Measuring sea surface height with a GNSS-Wave Glider

Science.gov (United States)

Morales Maqueda, Miguel Angel; Penna, Nigel T.; Foden, Peter R.; Martin, Ian; Cipollini, Paolo; Williams, Simon D.; Pugh, Jeff P.

2017-04-01

A GNSS-Wave Glider is a novel technique to measure sea surface height autonomously using the Global Navigation Satellite System (GNSS). It consists of an unmanned surface vehicle manufactured by Liquid Robotics, a Wave Glider, and a geodetic-grade GNSS antenna-receiver system, with the antenna installed on a mast on the vehicle's deck. The Wave Glider uses the differential wave motion through the water column for propulsion, thus guaranteeing an, in principle, indefinite autonomy. Solar energy is collected to power all on-board instrumentation, including the GNSS system. The GNSS-Wave Glider was first tested in Loch Ness in 2013, demonstrating that the technology is capable of mapping geoid heights within the loch with an accuracy of a few centimetres. The trial in Loch Ness did not conclusively confirm the reliability of the technique because, during the tests, the state of the water surface was much more benign than would normally be expect in the open ocean. We now report on a first deployment of a GNSS-Wave Glider in the North Sea. The deployment took place in August 2016 and lasted thirteen days, during which the vehicle covered a distance of about 350 nautical miles in the north western North Sea off Great Britain. During the experiment, the GNSS-Wave Glider experienced sea states between 1 (0-0.1 m wave heights) and 5 (2.5-4 m wave heights). The GNSS-Wave Glider data, recorded at 5 Hz frequency, were analysed using a post-processed kinematic GPS-GLONASS precise point positioning (PPP) approach, which were quality controlled using double difference GPS kinematic processing with respect to onshore reference stations. Filtered with a 900 s moving-average window, the PPP heights reveal geoid patterns in the survey area that are very similar to the EGM2008 geoid model, thus demonstrating the potential use of a GNSS-Wave Glider for marine geoid determination. The residual of subtracting the modelled or measured marine geoid from the PPP signal combines information

THE PERFORMANCE OF A TIGHT INS/GNSS/PHOTOGRAMMETRIC INTEGRATION SCHEME FOR LAND BASED MMS APPLICATIONS IN GNSS DENIED ENVIRONMENTS

Directory of Open Access Journals (Sweden)

C.-H. Chu

2016-06-01

Full Text Available The early development of mobile mapping system (MMS was restricted to applications that permitted the determination of the elements of exterior orientation from existing ground control. Mobile mapping refers to a means of collecting geospatial data using mapping sensors that are mounted on a mobile platform. Research works concerning mobile mapping dates back to the late 1980s. This process is mainly driven by the need for highway infrastructure mapping and transportation corridor inventories. In the early nineties, advances in satellite and inertial technology made it possible to think about mobile mapping in a different way. Instead of using ground control points as references for orienting the images in space, the trajectory and attitude of the imager platform could now be determined directly. Cameras, along with navigation and positioning sensors are integrated and mounted on a land vehicle for mapping purposes. Objects of interest can be directly measured and mapped from images that have been georeferenced using navigation and positioning sensors. Direct georeferencing (DG is the determination of time-variable position and orientation parameters for a mobile digital imager. The most common technologies used for this purpose today are satellite positioning using the Global Navigation Satellite System (GNSS and inertial navigation using an Inertial Measuring Unit (IMU. Although either technology used along could in principle determine both position and orientation, they are usually integrated in such a way that the IMU is the main orientation sensor, while the GNSS receiver is the main position sensor. However, GNSS signals are obstructed due to limited number of visible satellites in GNSS denied environments such as urban canyon, foliage, tunnel and indoor that cause the GNSS gap or interfered by reflected signals that cause abnormal measurement residuals thus deteriorates the positioning accuracy in GNSS denied environments. This study aims

Rapid characterization of seismic sources in Chile: Contribution of the GNSS component

Science.gov (United States)

Barrientos, S. E.; Riquelme, S.; Baez, J. C., Sr.

2017-12-01

The recently created National Seismological Center (CSN) of the University of Chile was tasked to upgrade the countrýs seismic network in 2013. The upgrade included new 65 collocated accelerometer and broadband instruments together with 130 GNSS devices designed to transmit their data in real time. Forty units of the GNSS devices include the RTX option, a real time 1-Hz positioning capability at 4-cm error level. The observation system is complemented with 297 additional stand-alone strong motion instruments mainly located in basins for seismic engineering purposes. Broadband data can be accessed in real time from IRIS Data Management Service under networks C and C1. Strong motion event data can be retrieved through the CSN database (evtdb.csn.uchile.cl). A server is being established to handle GNSS data requests through an NTRIP Caster. Completion of the connectivity of the GNSS remote units to the main acquisition servers is expected to take place within several months. In addition to the 40 units providing real time positioning through the RTX option, Precise Point Positioning (PPP) algorithms are being tested on the CSN main servers to enable real time estimates every second for all GNSS remote devices. Because of the high earthquake productivity rate in Chile, the RTX system capabilities have been positively tested in two cases already, demonstrating their excellent performance: i) the main aftershock (M7.6) of the April 1, 2014, northern Chile event and ii) the April 24, 2017, (M6.9) event in central Chile. The former produced coastal horizontal static displacements of the order of 30 cm while the latter of the order of 5 cm. In addition to rapid earthquake characterization through static deformation, W-phase displacement waveform inversions are included in the fast analysis providing excellent results. These new applications and methodologies have profoundly impacted the rapid evaluation of the tsunamigenic potential of large earthquakes in the near field.

Impacto de perfis de rádio ocultação GNSS na qualidade das Previsões de tempo do CPTEC/INPE

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Luiz Fernando Sapucci

2014-12-01

Full Text Available Estudos sobre a sensibilidade dos modelos de previsão numérica de tempo a erros nas condições iniciais têm evidenciado a contribuição da assimilação de dados na melhoria do desempenho dos mesmos em descrever o estado futuro da atmosfera. Entre outras fontes de dados, a assimilação de perfis atmosféricos obtidos por rádio ocultação Global Navigation Satellite System (GNSS tem-se destacado como uma ferramenta adicional na redução das deficiências do sistema de coleta de dados meteorológicos. Com o intuito de explorar os benefícios dessa fonte adicional de dados na previsão numérica de tempo gerada pelo modelo de circulação geral atmosférico do CPTEC/INPE, foram realizados experimentos assimilando perfis atmosféricos de altura geopotencial e umidade obtidos por rádio ocultação GNSS, utilizando dados da constelação Constellation Observing System for Meteorology Ionosphere & Climate (COSMIC, para os meses de janeiro e julho de 2009. Os resultados mostraram que o impacto é significativamente positivo durante o verão em todas as variáveis de estado, com ganhos expressivos na extensão das previsões válidas (coeficiente de correlação de anomalia acima de 60%, os quais foram em alguns casos superiores a 48 horas. Esse impacto foi ainda maior sobre a América do Sul com resultados positivos mesmo durante o inverno.

USGS GNSS Applications to Earthquake Disaster Response and Hazard Mitigation

Science.gov (United States)

Hudnut, K. W.; Murray, J. R.; Minson, S. E.

2015-12-01

Rapid characterization of earthquake rupture is important during a disaster because it establishes which fault ruptured and the extent and amount of fault slip. These key parameters, in turn, can augment in situ seismic sensors for identifying disruption to lifelines as well as localized damage along the fault break. Differential GNSS station positioning, along with imagery differencing, are important methods for augmenting seismic sensors. During response to recent earthquakes (1989 Loma Prieta, 1992 Landers, 1994 Northridge, 1999 Hector Mine, 2010 El Mayor - Cucapah, 2012 Brawley Swarm and 2014 South Napa earthquakes), GNSS co-seismic and post-seismic observations proved to be essential for rapid earthquake source characterization. Often, we find that GNSS results indicate key aspects of the earthquake source that would not have been known in the absence of GNSS data. Seismic, geologic, and imagery data alone, without GNSS, would miss important details of the earthquake source. That is, GNSS results provide important additional insight into the earthquake source properties, which in turn help understand the relationship between shaking and damage patterns. GNSS also adds to understanding of the distribution of slip along strike and with depth on a fault, which can help determine possible lifeline damage due to fault offset, as well as the vertical deformation and tilt that are vitally important for gravitationally driven water systems. The GNSS processing work flow that took more than one week 25 years ago now takes less than one second. Formerly, portable receivers needed to be set up at a site, operated for many hours, then data retrieved, processed and modeled by a series of manual steps. The establishment of continuously telemetered, continuously operating high-rate GNSS stations and the robust automation of all aspects of data retrieval and processing, has led to sub-second overall system latency. Within the past few years, the final challenges of

Contribution of Multi-GNSS Constellation to SLR-Derived Terrestrial Reference Frame

Science.gov (United States)

Sośnica, K.; Bury, G.; Zajdel, R.

2018-03-01

All satellites of new Global Navigation Satellite Systems (GNSS) are equipped with laser retroreflectors dedicated to Satellite Laser Ranging (SLR). This paper demonstrates the contribution of SLR tracking of multi-GNSS constellations to the improved SLR-derived reference frame and scientific products. We show a solution strategy with estimating satellite orbits, SLR station coordinates, geocenter coordinates, and Earth rotation parameters using SLR observations to 2 Laser Geodynamics Satellites (LAGEOS) and 55 GNSS satellites: 1 GPS, 31 Globalnaya Navigatsionnaya Sputnikovaya Sistema, 18 Galileo, 3 BeiDou Inclined Geosynchronous Orbit, 1 BeiDou Medium Earth Orbit, and 1 Quasi-Zenith Satellite System satellite for the period 2014.0-2017.4. Due to a substantial number of GNSS observations, the number of weekly solutions for some SLR stations, for example, Arkhyz, Komsomolsk, Altay, and Brasilia, is larger up to 41% in the combined LAGEOS + GNSS solution when compared to the LAGEOS-only solution. The SLR observations to GNSS can transfer the orientation of the reference frame from GNSS to SLR solutions. As a result, the SLR-derived pole coordinates and length-of-day estimates become more consistent with GNSS microwave-based results. The root-mean-square errors of length-of-day are reduced from 122.5 μs/d to 43.0 μs/d, whereas mean offsets are reduced from -81.6 μs/d to 0.5 μs/d in LAGEOS only and in the combined LAGEOS + GNSS solutions, respectively.

CONCEPTUAL DESIGN OF MONITORING AND CONTROL SUBSYSTEM FOR GNSS GROUND STATION

Directory of Open Access Journals (Sweden)

Seongkyun Jeong

2007-12-01

Full Text Available The Global Navigation Satellite System (GNSS becomes more important and is applied to various systems. Recently, the Galileo navigation system is being developed in Europe. Also, other countries like China, Japan and India are developing the global/regional navigation satellite system. As various global/regional navigation satellite systems are used, the navigation ground system gets more important for using the navigation system reasonably and efficiently. According to this trend, the technology of GNSS Ground Station (GGS is developing in many fields. The one of purposes for this study is to develop the high precision receiver for GNSS sensor station and to provide ground infrastructure for better performance services on navigation system. In this study, we consider the configuration of GNSS Ground Station and analyze function of Monitoring and Control subsystem which is a part of GNSS Ground Station. We propose Monitoring and Control subsystem which contains the navigation software for GNSS Ground System to monitor and control equipments in GNSS Ground Station, to spread the applied field of navigation system, and to provide improved navigation information to user.

Strong Sporadic E Occurrence Detected by Ground-Based GNSS

Science.gov (United States)

Sun, Wenjie; Ning, Baiqi; Yue, Xinan; Li, Guozhu; Hu, Lianhuan; Chang, Shoumin; Lan, Jiaping; Zhu, Zhengping; Zhao, Biqiang; Lin, Jian

2018-04-01

The ionospheric sporadic E (Es) layer has significant impact on radio wave propagation. The traditional techniques employed for Es layer observation, for example, ionosondes, are not dense enough to resolve the morphology and dynamics of Es layer in spatial distribution. The ground-based Global Navigation Satellite Systems (GNSS) technique is expected to shed light on the understanding of regional strong Es occurrence, owing to the facts that the critical frequency (foEs) of strong Es structure is usually high enough to cause pulse-like disturbances in GNSS total electron content (TEC), and a large number of GNSS receivers have been deployed all over the world. Based on the Chinese ground-based GNSS networks, including the Crustal Movement Observation Network of China and the Beidou Ionospheric Observation Network, a large-scale strong Es event was observed in the middle latitude of China. The strong Es shown as a band-like structure in the southwest-northeast direction extended more than 1,000 km. By making a comparative analysis of Es occurrences identified from the simultaneous observations by ionosondes and GNSS TEC receivers over China middle latitude statistically, we found that GNSS TEC can be well employed to observe strong Es occurrence with a threshold value of foEs, 14 MHz.

Sensing of the atmospheric variation using Low Cost GNSS Receiver

Science.gov (United States)

Bramanto, Brian; Gumilar, Irwan; Sidiq, Teguh P.; Kuntjoro, Wedyanto; Tampubolon, Daniel A.

2018-05-01

As the GNSS signals transmitted through the atmosphere, they are delayed by interference of TEC (Total Electron Content) in the ionosphere and water vapor in the troposphere. By using inverse-problem, name GNSS Meteorology, those parameters can be obtained precisely and several researches has approved and supported that method. However, the geodetic GNSS receivers are relatively high cost (30,000 to 70,000 each) to be established on a regular and uniform network. This research aims to investigate the potential use of low cost GNSS receiver (less than 2,000) to observe the atmospheric dynamic both in ionosphere and troposphere. Results indicated that low cost GNSS receiver is a promising tools to sensing the atmospheric dynamic, however, further processing is needed to enhance the data quality. It is found that both of ionosphere and troposphere dynamic has diurnal periodic component.

CDDIS_GNSS_products_erp

Data.gov (United States)

National Aeronautics and Space Administration — Earth Rotation Parameters (ERPs) derived from analysis of Global Navigation Satellite System (GNSS) data. These products are the generated by analysis centers in...

Application of GNSS Methods for Monitoring Offshore Platform Deformation

Science.gov (United States)

Myint, Khin Cho; Nasir Matori, Abd; Gohari, Adel

2018-03-01

Global Navigation Satellite System (GNSS) has become a powerful tool for high-precision deformation monitoring application. Monitoring of deformation and subsidence of offshore platform due to factors such as shallow gas phenomena. GNSS is the technical interoperability and compatibility between various satellite navigation systems such as modernized GPS, Galileo, reconstructed GLONASS to be used by civilian users. It has been known that excessive deformation affects platform structurally, causing loss of production and affects the efficiency of the machinery on board the platform. GNSS have been proven to be one of the most precise positioning methods where by users can get accuracy to the nearest centimeter of a given position from carrier phase measurement processing of GPS signals. This research is aimed at using GNSS technique, which is one of the most standard methods to monitor the deformation of offshore platforms. Therefore, station modeling, which accounts for the spatial correlated errors, and hence speeds up the ambiguity resolution process is employed. It was found that GNSS combines the high accuracy of the results monitoring the offshore platforms deformation with the possibility of survey.

Ultra-Tightly Coupled GNSS/INS for small UAVs

DEFF Research Database (Denmark)

Olesen, Daniel; Jakobsen, Jakob; Knudsen, Per

2017-01-01

This paper describes an ultra-tight integration of a Global Navigation Satellite System ( GNSS) receiver and an Inertial Navigation System ( INS) for small Unmanned Aerial Vehicles ( UAVs). The system is based on a low-cost and low-weight GNSS Intermediate Frequency ( IF) sampler which has been...

Tracking Clouds with low cost GNSS chips aided by the Arduino platform

Science.gov (United States)

Hameed, Saji; Realini, Eugenio; Ishida, Shinya

2016-04-01

The Global Navigation Satellite System (GNSS) is a constellation of satellites that is used to provide geo-positioning services. Besides this application, the GNSS system is important for a wide range of scientific and civilian applications. For example, GNSS systems are routinely used in civilian applications such as surveying and scientific applications such as the study of crustal deformation. Another important scientific application of GNSS system is in meteorological research. Here it is mainly used to determine the total water vapour content of the troposphere, hereafter Precipitable Water Vapor (PWV). However, both GNSS receivers and software have prohibitively high price due to a variety of reasons. To overcome this somewhat artificial barrier we are exploring the use of low-cost GNSS receivers along with open source GNSS software for scientific research, in particular for GNSS meteorology research. To achieve this aim, we have developed a custom Arduino compatible data logging board that is able to operate together with a specific low-cost single frequency GNSS receiver chip from NVS Technologies AG. We have also developed an open-source software bundle that includes a new Arduino core for the Atmel324p chip, which is the main processor used in our custom logger. We have also developed software code that enables data collection, logging and parsing of the GNSS data stream. Additionally we have comprehensively evaluated the low power characteristics of the GNSS receiver and logger boards. Currently we are exploring the use of several openly source or free to use for research software to map GNSS delays to PWV. These include the open source goGPS (http://www.gogps-project.org/) and gLAB (http://gage.upc.edu/gLAB) and the openly available GAMIT software from Massachusetts Institute of Technology (MIT). We note that all the firmware and software developed as part of this project is available on an open source license.

Utilizing new GNSS capabilities for exploring Geospace

Science.gov (United States)

Coster, A. J.

2015-12-01

In 2000 the density of GPS receivers across the continental United States increased to the point that strictly data-driven regional maps of total electron content (TEC) could be constructed. These data-driven maps allowed the TEC to be monitored throughout the course of geomagnetic storms and to observe the progression of traveling ionospheric disturbances. This allowed studies of the development of storm enhanced density plumes in both hemispheres and of the dynamic changes in the equatorial TEC following stratospheric warming events. Currently, GPS TEC maps have become recognized as one of the premier tools to monitor coupling of atmospheric regions from both below and above the ionosphere. The number of available scientific dual-frequency receivers across the globe now exceeds 3000. However this number is anticipated to increase rapidly in part due to the numerous arrays being fielded for commercial applications such as precision farming and highway surveying. In addition, there will be a rapid increase in the number of GNSS signals available in the near future. Besides GPS, the European Union is building a system named GALILEO, which will consist of a 30-satellite constellation. The Russians have a system based on a 24-satellite constellation named GLONASS. The Chinese are developing a system called Beidou, which means "stars of the Big Dipper". The Beidou system will consist of 35 satellites. By 2023, there will be more than 160 GNSS satellites and 400 signals. Multi-constellation, multi-band GNSS will be a major enabler for space weather studies. This talk will focus on the potential of using the multiple new GNSS signals and the new higher density receiver arrays for measurements of plasma drift, detailed studies of traveling ionospheric disturbances (TIDS) and expanded studies of atmospheric coupling. We will conclude by describing the tremendous potential of merging GNSS observations with observations collected by arrays of low-cost, low-power, and small

Preliminary Design of Monitoring and Control Subsystem for GNSS Ground Station

Directory of Open Access Journals (Sweden)

Seongkyun Jeong

2008-06-01

Full Text Available GNSS (Global Navigation Satellite System Ground Station monitors navigation satellite signal, analyzes navigation result, and uploads correction information to satellite. GNSS Ground Station is considered as a main object for constructing GNSS infra-structure and applied in various fields. ETRI (Electronics and Telecommunications Research Institute is developing Monitoring and Control subsystem, which is subsystem of GNSS Ground Station. Monitoring and Control subsystem acquires GPS and Galileo satellite signal and provides signal monitoring data to GNSS control center. In this paper, the configurations of GNSS Ground Station and Monitoring and Control subsystem are introduced and the preliminary design of Monitoring and Control subsystem is performed. Monitoring and Control subsystem consists of data acquisition module, data formatting and archiving module, data error correction module, navigation solution determination module, independent quality monitoring module, and system operation and maintenance module. The design process uses UML (Unified Modeling Language method which is a standard for developing software and consists of use-case modeling, domain design, software structure design, and user interface structure design. The preliminary design of Monitoring and Control subsystem enhances operation capability of GNSS Ground Station and is used as basic material for detail design of Monitoring and Control subsystem.

International Collaboration in the field of GNSS-Meteorology and Climate Monitoring

Science.gov (United States)

Jones, J.; Guerova, G.; Dousa, J.; Bock, O.; Elgered, G.; Vedel, H.; Pottiaux, E.; de Haan, S.; Pacione, R.; Dick, G.; Wang, J.; Gutman, S. I.; Wickert, J.; Rannat, K.; Liu, G.; Braun, J. J.; Shoji, Y.

2012-12-01

International collaboration in the field of GNSS-meteorology and climate monitoring is essential, as severe weather and climate change have no respect for national boundaries. The use of Global Navigation Satellite Systems (GNSS) for meteorological purposes is an established atmospheric observing technique, which can accurately sense water vapour, the most abundant greenhouse gas, accounting for 60-70% of atmospheric warming. Severe weather forecasting is challenging, in part due to the high temporal and spatial variation of atmospheric water vapour. Water vapour is currently under-sampled and obtaining and exploiting more high-quality humidity observations is essential to severe weather forecasting and climate monitoring. A proposed EU COST Action (http://www.cost.eu) will address new and improved capabilities from concurrent developments in both GNSS and atmospheric communities to improve (short-range) weather forecasts and climate projections. For the first time, the synergy of the three GNSS systems, GPS, GLONASS and Galileo, will be used to develop new, advanced tropospheric products, stimulating the full potential exploitation of multi-GNSS water vapour estimates on a wide range of temporal and spatial scales, from real-time severe weather monitoring and forecasting to climate research. The Action will work in close collaboration with the Global Climate Observing System (GCOS) Reference Upper Air Network (GRUAN), GNSS Precipitable Water Task Team (TT). GRUAN is a global reference observing network, designed to meet climate requirements and to fill a major void in the current global observing system. GRUAN observations will provide long-term, high-quality data to determine climatic trends and to constrain and validate data from space-based remote sensors. Ground-based GNSS PW was identified as a Priority 1 measurement for GRUAN, and the GNSS-PW TT's goal is to develop explicit guidance on hardware, software and data management practices to obtain GNSS PW

Deep Coupled Integration of CSAC and GNSS for Robust PNT

OpenAIRE

Ma, Lin; You, Zheng; Li, Bin; Zhou, Bin; Han, Runqi

2015-01-01

Global navigation satellite systems (GNSS) are the most widely used positioning, navigation, and timing (PNT) technology. However, a GNSS cannot provide effective PNT services in physical blocks, such as in a natural canyon, canyon city, underground, underwater, and indoors. With the development of micro-electromechanical system (MEMS) technology, the chip scale atomic clock (CSAC) gradually matures, and performance is constantly improved. A deep coupled integration of CSAC and GNSS is explo...

MULTI-GNSS RECEIVER FOR AEROSPACE NAVIGATION AND POSITIONING APPLICATIONS

Directory of Open Access Journals (Sweden)

T. R. Peres

2014-03-01

Full Text Available The upcoming Galileo system opens a wide range of new opportunities in the Global Navigation Satellite System (GNSS market. However, the characteristics of the future GNSS signals require the development of new GNSS receivers. In the frame of the REAGE project, DEIMOS and ISEL have developed a GNSS receiver targeted for aerospace applications, supporting current and future GPS L1 and Galileo E1 signals, based on commercial (or, in the furthest extent, industrial grade components. Although the REAGE project aimed at space applications, the REAGE receiver is also applicable to many terrestrial applications (ground or airborne, such as Georeferencing and Unmanned Aerial Vehicle (UAV navigation. This paper presents the architecture and features of the REAGE receiver, as well as some results of the validation campaign with GPS L1 and Galileo E1 signals.

Modeling the Effects of the Local Environment on a Received GNSS Signal

Science.gov (United States)

2012-12-18

fIF + fDm(t)) t+ φm) (3.5) rIF(t) ∈ C is now restated using a complex exponential instead of sine and cosine functions: rIF(t) = M(t)∑ m=0 Am(t)D(t− τm... Portugal , 2010, pp. 1480-1485. 35. F. Caron, E. Duflos, M. Davy, P. Vanheeghe, “Particle Filtering for Multipath Effects Reduction in Land Vehicule...GNSS Re- ceivers,” M.S. thesis, Instituto Superior Tecnico, Universidade Tecnica de Lisboa, Lisbon, Portugal , 2008. 45. J. Soubielle, I. Fijalkow, P

Short-term estimation of GNSS TEC using a neural network model in Brazil

Science.gov (United States)

Ferreira, Arthur Amaral; Borges, Renato Alves; Paparini, Claudia; Ciraolo, Luigi; Radicella, Sandro M.

2017-10-01

This work presents a novel Neural Network (NN) model to estimate Total Electron Content (TEC) from Global Navigation Satellite Systems (GNSS) measurements in three distinct sectors in Brazil. The purpose of this work is to start the investigations on the development of a regional model that can be used to determine the vertical TEC over Brazil, aiming future applications on a near real-time frame estimations and short-term forecasting. The NN is used to estimate the GNSS TEC values at void locations, where no dual-frequency GNSS receiver that may be used as a source of data to GNSS TEC estimation is available. This approach is particularly useful for GNSS single-frequency users that rely on corrections of ionospheric range errors by TEC models. GNSS data from the first GLONASS network for research and development (GLONASS R&D network) installed in Latin America, and from the Brazilian Network for Continuous Monitoring of the GNSS (RMBC) were used on TEC calibration. The input parameters of the NN model are based on features known to influence TEC values, such as geographic location of the GNSS receiver, magnetic activity, seasonal and diurnal variations, and solar activity. Data from two ten-days periods (from DoY 154 to 163 and from 282 to 291) are used to train the network. Three distinct analyses have been carried out in order to assess time-varying and spatial performance of the model. At the spatial performance analysis, for each region, a set of stations is chosen to provide training data to the NN, and after the training procedure, the NN is used to estimate vTEC behavior for the test station which data were not presented to the NN in training process. An analysis is done by comparing, for each testing station, the estimated NN vTEC delivered by the NN and reference calibrated vTEC. Also, as a second analysis, the network ability to forecast one day after the time interval (DoY 292) based on information of the second period of investigation is also assessed

Influence of Ionospheric Irregularities on GNSS Remote Sensing

Directory of Open Access Journals (Sweden)

M. V. Tinin

2015-01-01

Full Text Available We have used numerical simulation to study the effects of ionospheric irregularities on accuracy of global navigation satellite system (GNSS measurements, using ionosphere-free (in atmospheric research and geometry-free (in ionospheric research dual-frequency phase combinations. It is known that elimination of these effects from multifrequency GNSS measurements is handi-capped by diffraction effects during signal propagation through turbulent ionospheric plasma with the inner scale being smaller than the Fresnel radius. We demonstrated the possibility of reducing the residual ionospheric error in dual-frequency GNSS remote sensing in ionosphere-free combination by Fresnel inversion. The inversion parameter, the distance to the virtual screen, may be selected from the minimum of amplitude fluctuations. This suggests the possibility of improving the accuracy of GNSS remote sensing in meteorology. In the study of ionospheric disturbances with the aid of geometry-free combination, the Fresnel inversion eliminates only the third-order error. To eliminate the random TEC component which, like the measured average TEC, is the first-order correction, we should use temporal filtering (averaging.

Detecting Volcanic Ash Plumes with GNSS Signals

Science.gov (United States)

Rainville, N.; Larson, K. M.; Palo, S. E.; Mattia, M.; Rossi, M.; Coltelli, M.; Roesler, C.; Fee, D.

2016-12-01

Global Navigation Satellite Systems (GNSS) receivers are commonly placed near volcanic sites to measure ground deformation. In addition to the carrier phase data used to measure ground position, these receivers also record Signal to Noise ratio (SNR) data. Larson (2013) showed that attenuations in SNR data strongly correlate with ash emissions at a series of eruptions of Redoubt Volcano. This finding has been confirmed at eruptions for Tongariro, Mt Etna, Mt Shindake, and Sakurajima. In each of these detections, very expensive geodetic quality GNSS receivers were used. If low-cost GNSS instruments could be used instead, a networked array could be deployed and optimized for plume detection and tomography. The outputs of this sensor array could then be used by both local volcanic observatories and Volcano Ash Advisory Centers. Here we will describe progress in developing such an array. The sensors we are working with are intended for navigation use, and thus lack the supporting power and communications equipment necessary for a networked system. Reliably providing those features is major challenge for the overall sensor design. We have built prototypes of our Volcano Ash Plume Receiver (VAPR), with solar panels, lithium-ion batteries and onboard data storage for preliminary testing. We will present results of our field tests of both receivers and antennas. A second critical need for our array is a reliable detection algorithm. We have tested our algorithm on data from recent eruptions and have incorporated the noise characteristics of the low-cost GNSS receiver. We have also developed a simulation capability so that the receivers can be deployed to optimize vent crossing GNSS signals.

Global Ionospheric Modelling using Multi-GNSS: BeiDou, Galileo, GLONASS and GPS.

Science.gov (United States)

Ren, Xiaodong; Zhang, Xiaohong; Xie, Weiliang; Zhang, Keke; Yuan, Yongqiang; Li, Xingxing

2016-09-15

The emergence of China's Beidou, Europe's Galileo and Russia's GLONASS satellites has multiplied the number of ionospheric piercing points (IPP) offered by GPS alone. This provides great opportunities for deriving precise global ionospheric maps (GIMs) with high resolution to improve positioning accuracy and ionospheric monitoring capabilities. In this paper, the GIM is developed based on multi-GNSS (GPS, GLONASS, BeiDou and Galileo) observations in the current multi-constellation condition. The performance and contribution of multi-GNSS for ionospheric modelling are carefully analysed and evaluated. Multi-GNSS observations of over 300 stations from the Multi-GNSS Experiment (MGEX) and International GNSS Service (IGS) networks for two months are processed. The results show that the multi-GNSS GIM products are better than those of GIM products based on GPS-only. Differential code biases (DCB) are by-products of the multi-GNSS ionosphere modelling, the corresponding standard deviations (STDs) are 0.06 ns, 0.10 ns, 0.18 ns and 0.15 ns for GPS, GLONASS, BeiDou and Galileo, respectively in satellite, and the STDs for the receiver are approximately 0.2~0.4 ns. The single-frequency precise point positioning (SF-PPP) results indicate that the ionospheric modelling accuracy of the proposed method based on multi-GNSS observations is better than that of the current dual-system GIM in specific areas.

Data assimilation of GNSS zenith total delays from a Nordic processing centre

Science.gov (United States)

Lindskog, Magnus; Ridal, Martin; Thorsteinsson, Sigurdur; Ning, Tong

2017-11-01

Atmospheric moisture-related information estimated from Global Navigation Satellite System (GNSS) ground-based receiver stations by the Nordic GNSS Analysis Centre (NGAA) have been used within a state-of-the-art kilometre-scale numerical weather prediction system. Different processing techniques have been implemented to derive the moisture-related GNSS information in the form of zenith total delays (ZTDs) and these are described and compared. In addition full-scale data assimilation and modelling experiments have been carried out to investigate the impact of utilizing moisture-related GNSS data from the NGAA processing centre on a numerical weather prediction (NWP) model initial state and on the ensuing forecast quality. The sensitivity of results to aspects of the data processing, station density, bias-correction and data assimilation have been investigated. Results show benefits to forecast quality when using GNSS ZTD as an additional observation type. The results also show a sensitivity to thinning distance applied for GNSS ZTD observations but not to modifications to the number of predictors used in the variational bias correction applied. In addition, it is demonstrated that the assimilation of GNSS ZTD can benefit from more general data assimilation enhancements and that there is an interaction of GNSS ZTD with other types of observations used in the data assimilation. Future plans include further investigation of optimal thinning distances and application of more advanced data assimilation techniques.

a Precise, Low-Cost Rtk Gnss System for Uav Applications

Science.gov (United States)

Stempfhuber, W.; Buchholz, M.

2011-09-01

High accuracy with real-time positioning of moving objects has been considered a standard task of engineering geodesy for 10 to 15 years. An absolute positioning accuracy of 1-3 cm is generally possible worldwide and is further used in many areas of machine guidance (machine control and guidance), and farming (precision farming) as well as for various special applications (e.g. railway trolley, mining, etc.). The cost of the measuring instruments required for the use of geodetic L1/L2 receivers with a local reference station amounts to approximately USD 30,000 to 50,000. Therefore, dual frequency RTK GNSS receivers are not used in the mass market. Affordable GPS/GNSS modules have already reached the mass market in various areas such as mobile phones, car navigation, the leisure industry, etc. Kinematic real-time positioning applications with centimetre or decimetre levels could also evolve into a mass product. In order for this to happen, the costs for such systems must lie between USD 1,000 to 2,000. What exactly low-cost means is determined by the precise specifications of the given individual application. Several university studies in geodesy focus on the approach of high-accuracy positioning by means of single frequency receivers for static applications [e.g. GLABSCH et. al. 2009, SCHWIEGER and GLÄSER 2005, ALKAN 2010, REALINI et. al. 2010, KORTH and HOFMANN 2011]. Although intelligent approaches have been developed that compute a trajectory in the post-processing mode [REALINI et. al., 2010], at present, there are only a very few GNSS Low-Cost Systems that enable real-time processing. This approach to precise position determination by means of the computation of static raw data with single frequency receivers is currently being explored in a research project at the Beuth Hochschule für Technik Berlin - and is being further developed for kinematic applications. The project is embedded in the European Social Fund. It is a follow-up project in the area of

A comprehensive method for GNSS data quality determination to improve ionospheric data analysis.

Science.gov (United States)

Kim, Minchan; Seo, Jiwon; Lee, Jiyun

2014-08-14

Global Navigation Satellite Systems (GNSS) are now recognized as cost-effective tools for ionospheric studies by providing the global coverage through worldwide networks of GNSS stations. While GNSS networks continue to expand to improve the observability of the ionosphere, the amount of poor quality GNSS observation data is also increasing and the use of poor-quality GNSS data degrades the accuracy of ionospheric measurements. This paper develops a comprehensive method to determine the quality of GNSS observations for the purpose of ionospheric studies. The algorithms are designed especially to compute key GNSS data quality parameters which affect the quality of ionospheric product. The quality of data collected from the Continuously Operating Reference Stations (CORS) network in the conterminous United States (CONUS) is analyzed. The resulting quality varies widely, depending on each station and the data quality of individual stations persists for an extended time period. When compared to conventional methods, the quality parameters obtained from the proposed method have a stronger correlation with the quality of ionospheric data. The results suggest that a set of data quality parameters when used in combination can effectively select stations with high-quality GNSS data and improve the performance of ionospheric data analysis.

The inertial attitude augmentation for ambiguity resolution in SF/SE-GNSS attitude determination.

Science.gov (United States)

Zhu, Jiancheng; Hu, Xiaoping; Zhang, Jingyu; Li, Tao; Wang, Jinling; Wu, Meiping

2014-06-26

The Unaided Single Frequency/Single Epoch Global Navigation Satellite System (SF/SE GNSS) model is the most challenging scenario for ambiguity resolution in the GNSS attitude determination application. To improve the performance of SF/SE-GNSS ambiguity resolution without excessive cost, the Micro-Electro-Mechanical System Inertial Measurement Unit (MEMS-IMU) is a proper choice for the auxiliary sensor that carries out the inertial attitude augmentation. Firstly, based on the SF/SE-GNSS compass model, the Inertial Derived Baseline Vector (IDBV) is defined to connect the MEMS-IMU attitude measurement with the SF/SE-GNSS ambiguity search space, and the mechanism of inertial attitude augmentation is revealed from the perspective of geometry. Then, through the quantitative description of model strength by Ambiguity Dilution of Precision (ADOP), two ADOPs are specified for the unaided SF/SE-GNSS compass model and its inertial attitude augmentation counterparts, respectively, and a sufficient condition is proposed for augmenting the SF/SE-GNSS model strength with inertial attitude measurement. Finally, in the framework of an integer aperture estimator with fixed failure rate, the performance of SF/SE-GNSS ambiguity resolution with inertial attitude augmentation is analyzed when the model strength is varying from strong to weak. The simulation results show that, in the SF/SE-GNSS attitude determination application, MEMS-IMU can satisfy the requirements of ambiguity resolution with inertial attitude augmentation.

The Inertial Attitude Augmentation for Ambiguity Resolution in SF/SE-GNSS Attitude Determination

Science.gov (United States)

Zhu, Jiancheng; Hu, Xiaoping; Zhang, Jingyu; Li, Tao; Wang, Jinling; Wu, Meiping

2014-01-01

The Unaided Single Frequency/Single Epoch Global Navigation Satellite System (SF/SE GNSS) model is the most challenging scenario for ambiguity resolution in the GNSS attitude determination application. To improve the performance of SF/SE-GNSS ambiguity resolution without excessive cost, the Micro-Electro-Mechanical System Inertial Measurement Unit (MEMS-IMU) is a proper choice for the auxiliary sensor that carries out the inertial attitude augmentation. Firstly, based on the SF/SE-GNSS compass model, the Inertial Derived Baseline Vector (IDBV) is defined to connect the MEMS-IMU attitude measurement with the SF/SE-GNSS ambiguity search space, and the mechanism of inertial attitude augmentation is revealed from the perspective of geometry. Then, through the quantitative description of model strength by Ambiguity Dilution of Precision (ADOP), two ADOPs are specified for the unaided SF/SE-GNSS compass model and its inertial attitude augmentation counterparts, respectively, and a sufficient condition is proposed for augmenting the SF/SE-GNSS model strength with inertial attitude measurement. Finally, in the framework of an integer aperture estimator with fixed failure rate, the performance of SF/SE-GNSS ambiguity resolution with inertial attitude augmentation is analyzed when the model strength is varying from strong to weak. The simulation results show that, in the SF/SE-GNSS attitude determination application, MEMS-IMU can satisfy the requirements of ambiguity resolution with inertial attitude augmentation. PMID:24971472

A REVIEW ON LEGAL TRACEABILITY OF GNSS MEASUREMENTS IN THE MALAYSIAN CADASTRAL PRACTICE

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J. Gill

2016-09-01

Full Text Available As the dependency on Global Navigation Satellite System (GNSS in surveying has been growing over the years, the need for legal traceability of GNSS measurements has become a significant matter. In Malaysia, with the advent of the Malaysia Real-time Kinematic Network (MyRTKnet, GNSS surveying has revolutionised land survey and mapping. Correspondingly, the Department of Survey and Mapping Malaysia (DSMM amended and published standard regulations and guidelines concerning cadastral survey, i.e., Cadastral Survey Regulations 2009, to include GNSS measurements. However, these regulations and guidelines has not comprehensively incorporated legal traceability of GNSS measurements; which is a prerequisite for cadastral surveys as it requires reliable and conclusive evidence for issues such as boundary disputes. The first objective of this paper is to review and discuss the legal traceability of GNSS measurements. Secondly, it will highlight the current practice and issues, i.e., with regard to legal traceability, within the present Malaysian cadastral regulation and guidelines, in relation to the prevalently adopted Network RTK (N-RTK technique, GNSS instrument calibrations, and reference stations’ accuracy. Lastly, a rudimentary best practice guideline for GNSS surveying in cadastral survey for Malaysia is proposed. It is expected that this paper will contribute to the implementation of a best practice guideline, which is inclusive of legal traceability of GNSS measurements, for the Malaysian cadastral practice.

Study of GNSS Loss of Lock Characteristics under Ionosphere Scintillation with GNSS Data at Weipa (Australia) During Solar Maximum Phase.

Science.gov (United States)

Liu, Yang; Fu, Lianjie; Wang, Jinling; Zhang, Chunxi

2017-09-25

One of the adverse impacts of scintillation on GNSS signals is the loss of lock status, which can lead to GNSS geometry and visibility reductions that compromise the accuracy and integrity of navigation performance. In this paper the loss of lock based on ionosphere scintillation in this solar maximum phase has been well investigated with respect to both temporal and spatial behaviors, based on GNSS observatory data collected at Weipa (Australia; geographic: 12.45° S, 130.95° E; geomagnetic: 21.79° S, 214.41° E) from 2011 to 2015. Experiments demonstrate that the percentage of occurrence of loss of lock events under ionosphere scintillation is closely related with solar activity and seasonal shifts. Loss of lock behaviors under ionosphere scintillation related to elevation and azimuth angles are statistically analyzed, with some distinct characteristics found. The influences of daytime scintillation and geomagnetic storms on loss of lock have also been discussed in details. The proposed work is valuable for a deeper understanding of theoretical mechanisms of-loss of lock under ionosphere scintillation in global regions, and provides a reference for GNSS applications in certain regions at Australian low latitudes.

A grid-based tropospheric product for China using a GNSS network

Science.gov (United States)

Zhang, Hongxing; Yuan, Yunbin; Li, Wei; Zhang, Baocheng; Ou, Jikun

2017-11-01

Tropospheric delay accounts for one source of error in global navigation satellite systems (GNSS). To better characterize the tropospheric delays in the temporal and spatial domain and facilitate the safety-critical use of GNSS across China, a method is proposed to generate a grid-based tropospheric product (GTP) using the GNSS network with an empirical tropospheric model, known as IGGtrop. The prototype system generates the GTPs in post-processing and real-time modes and is based on the undifferenced and uncombined precise point positioning (UU-PPP) technique. GTPs are constructed for a grid form (2.0{°}× 2.5{°} latitude-longitude) over China with a time resolution of 5 min. The real-time GTP messages are encoded in a self-defined RTCM3 format and broadcast to users using NTRIP (networked transport of RTCM via internet protocol), which enables efficient and safe transmission to real-time users. Our approach for GTP generation consists of three sequential steps. In the first step, GNSS-derived zenith tropospheric delays (ZTDs) for a network of GNSS stations are estimated using UU-PPP. In the second step, vertical adjustments for the GNSS-derived ZTDs are applied to address the height differences between the GNSS stations and grid points. The ZTD height corrections are provided by the IGGtrop model. Finally, an inverse distance weighting method is used to interpolate the GNSS-derived ZTDs from the surrounding GNSS stations to the location of the grid point. A total of 210 global positioning system (GPS) stations from the crustal movement observation network of China are used to generate the GTPs in both post-processing and real-time modes. The accuracies of the GTPs are assessed against with ERA-Interim-derived ZTDs and the GPS-derived ZTDs at 12 test GPS stations, respectively. The results show that the post-processing and real-time GTPs can provide the ZTDs with accuracies of 1.4 and 1.8 cm, respectively. We also apply the GTPs in real-time kinematic GPS PPP

GNSS-based receiver autonomous integrity monitoring for aircraft navigation

NARCIS (Netherlands)

Imparato, D.

2016-01-01

Nowadays, GNSS-based navigation is moving more and more to critical applications. Global Navigation Satellite Systems (GNSS), which in the past used to be represented by the American GPS and the Russian GLONASS are now growing in number and performance. The European systemGalileo and the Chinese

A hybrid data fusion method for GNSS/INS integration navigation system

Science.gov (United States)

Yang, Ling; Li, Bofeng; Shen, Yunzhong; Li, Haojun

2017-04-01

Although DGNSS is widely used and PPP-GNSS is nowadays a viable precise positioning technology option, the major disadvantage of GNSS still remains: signal blockage due to obstructions in urban and built up environments, and extreme power attenuation of the signals when operated indoors. The combination of GNSS with other sensors, such as a self-contained inertial navigation system (INS), provides an ideal position and attitude determination solution which can not only mitigate the weakness of GNSS, but also bound the INS error that otherwise would grow with time when the INS operates alone. However, the navigation accuracy provided by GNSS/INS strongly depends on the quality and geometry of the GNSS observations, the quality of the INS technology used, and the integration model applied. There are two main types of coupled schemes for integration systems: loosely coupled integration and tightly coupled integration. In loosely coupled integration, position measurements are taken from both systems and combined optimally, usually in a Kalman filter. Tightly coupled integration directly combines the raw pseudorange or carrier phase measurements of GNSS with inertial measurements in an extended Kalman filter. The latter technique improves the ability to resolve ambiguities, i.e. allows a quicker recovery from outage events such as a loss of signal under vegetation. In recent years, tightly coupled differential carrier phase GNSS/INS integration has become popular, because it has the advantage of providing accurate position information even when GPS measurements are rank-deficient in stand-alone processing and is theoretically optimal in a filtering sense, especially in urban navigation applications. However, the heavier computational burden and sensor communication usually complicate the tightly coupled integration and reduce the system efficiency, compared with the loosely coupled integration. In this paper, it has been proved that the loosely coupled and tightly

Beamsteerable GNSS Radio Occultation ASIC

Data.gov (United States)

National Aeronautics and Space Administration — We will develop an integrated RF ASIC to enable high quality radio occultation (RO) weather observations using the Global Navigations System Satellite (GNSS)...

Establishment of Karadeniz Technical University Permanent GNSS Station as Reactivated of TRAB IGS Station

Directory of Open Access Journals (Sweden)

Kazancı Selma Zengin

2017-12-01

Full Text Available In recent years, Global Navigation Satellite Systems (GNSS have gained great importance in terms of the benefi ts it provides such as precise geodetic point positioning, determining crustal deformations, navigation, vehicle monitoring systems and meteorological applications etc. As in Turkey, for this purpose, each country has set up its own GNSS station networks like Turkish National Permanent RTK Network analyzed precise station coordinates and velocities together with the International GNSS Service, Turkish National Fundamental GPS Network and Turkish National Permanent GNSS Network (TNPGN stations not only are utilized as precise positioning but also GNSS meteorology studies so total number of stations are increased. This work is related to the reactivated of the TRAB IGS station which was established in Karadeniz Technical University, Department of Geomatics Engineering. Within the COST ES1206 Action (GNSS4SWEC KTU analysis center was established and Trop-NET system developed by Geodetic Observatory Pecny (GOP, RIGTC in order to troposphere monitoring. The project titled “Using Regional GNSS Networks to Strengthen Severe Weather Prediction” was accepted to the scientifi c and technological research council of Turkey (TUBITAK. With this project, we will design 2 new constructed GNSS reference station network. Using observation data of network, we will compare water vapor distribution derived by GNSS Meteorology and GNSS Tomography. At this time, KTU AC was accepted as E-GVAP Analysis Centre in December 2016. KTU reference station is aimed to be a member of the EUREF network with these studies.

Establishment of Karadeniz Technical University Permanent GNSS Station as Reactivated of TRAB IGS Station

Science.gov (United States)

Kazancı, Selma Zengin; Kayıkçı, Emine Tanır

2017-12-01

In recent years, Global Navigation Satellite Systems (GNSS) have gained great importance in terms of the benefi ts it provides such as precise geodetic point positioning, determining crustal deformations, navigation, vehicle monitoring systems and meteorological applications etc. As in Turkey, for this purpose, each country has set up its own GNSS station networks like Turkish National Permanent RTK Network analyzed precise station coordinates and velocities together with the International GNSS Service, Turkish National Fundamental GPS Network and Turkish National Permanent GNSS Network (TNPGN) stations not only are utilized as precise positioning but also GNSS meteorology studies so total number of stations are increased. This work is related to the reactivated of the TRAB IGS station which was established in Karadeniz Technical University, Department of Geomatics Engineering. Within the COST ES1206 Action (GNSS4SWEC) KTU analysis center was established and Trop-NET system developed by Geodetic Observatory Pecny (GOP, RIGTC) in order to troposphere monitoring. The project titled "Using Regional GNSS Networks to Strengthen Severe Weather Prediction" was accepted to the scientifi c and technological research council of Turkey (TUBITAK). With this project, we will design 2 new constructed GNSS reference station network. Using observation data of network, we will compare water vapor distribution derived by GNSS Meteorology and GNSS Tomography. At this time, KTU AC was accepted as E-GVAP Analysis Centre in December 2016. KTU reference station is aimed to be a member of the EUREF network with these studies.

A Novel Range Compression Algorithm for Resolution Enhancement in GNSS-SARs

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Yu Zheng

2017-06-01

Full Text Available In this paper, a novel range compression algorithm for enhancing range resolutions of a passive Global Navigation Satellite System-based Synthetic Aperture Radar (GNSS-SAR is proposed. In the proposed algorithm, within each azimuth bin, firstly range compression is carried out by correlating a reflected GNSS intermediate frequency (IF signal with a synchronized direct GNSS base-band signal in the range domain. Thereafter, spectrum equalization is applied to the compressed results for suppressing side lobes to obtain a final range-compressed signal. Both theoretical analysis and simulation results have demonstrated that significant range resolution improvement in GNSS-SAR images can be achieved by the proposed range compression algorithm, compared to the conventional range compression algorithm.

GEOREFERENCING IN GNSS-CHALLENGED ENVIRONMENT: INTEGRATING UWB AND IMU TECHNOLOGIES

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C. K. Toth

2017-05-01

Full Text Available Acquiring geospatial data in GNSS compromised environments remains a problem in mapping and positioning in general. Urban canyons, heavily vegetated areas, indoor environments represent different levels of GNSS signal availability from weak to no signal reception. Even outdoors, with multiple GNSS systems, with an ever-increasing number of satellites, there are many situations with limited or no access to GNSS signals. Independent navigation sensors, such as IMU can provide high-data rate information but their initial accuracy degrades quickly, as the measurement data drift over time unless positioning fixes are provided from another source. At The Ohio State University’s Satellite Positioning and Inertial Navigation (SPIN Laboratory, as one feasible solution, Ultra- Wideband (UWB radio units are used to aid positioning and navigating in GNSS compromised environments, including indoor and outdoor scenarios. Here we report about experiences obtained with georeferencing a pushcart based sensor system under canopied areas. The positioning system is based on UWB and IMU sensor integration, and provides sensor platform orientation for an electromagnetic inference (EMI sensor. Performance evaluation results are provided for various test scenarios, confirming acceptable results for applications where high accuracy is not required.

The contribution of Multi-GNSS Experiment (MGEX) to precise point positioning

Science.gov (United States)

Guo, Fei; Li, Xingxing; Zhang, Xiaohong; Wang, Jinling

2017-06-01

In response to the changing world of GNSS, the International GNSS Service (IGS) has initiated the Multi-GNSS Experiment (MGEX). As part of the MGEX project, initial precise orbit and clock products have been released for public use, which are the key prerequisites for multi-GNSS precise point positioning (PPP). In particular, precise orbits and clocks at intervals of 5 min and 30 s are presently available for the new emerging systems. This paper investigates the benefits of multi-GNSS for PPP. Firstly, orbit and clock consistency tests (between different providers) were performed for GPS, GLONASS, Galileo and BeiDou. In general, the differences of GPS are, respectively, 1.0-1.5 cm for orbit and 0.1 ns for clock. The consistency of GLONASS is worse than GPS by a factor of 2-3, i.e. 2-4 cm for orbit and 0.2 ns for clock. However, the corresponding differences of Galileo and BeiDou are significantly larger than those of GPS and GLONASS, particularly for the BeiDou GEO satellites. Galileo as well as BeiDou IGSO/MEO products have a consistency of 0.1-0.2 m for orbit, and 0.2-0.3 ns for clock. As to BeiDou GEO satellites, the difference of their orbits reaches 3-4 m in along-track, 0.5-0.6 m in cross-track, and 0.2-0.3 m in the radial directions, together with an average RMS of 0.6 ns for clock. Furthermore, the short-term stability of multi-GNSS clocks was analyzed by Allan deviation. Results show that clock stability of the onboard GNSS is highly dependent on the satellites generations, operational lifetime, orbit types, and frequency standards. Finally, kinematic PPP tests were conducted to investigate the contribution of multi-GNSS and higher rate clock corrections. As expected, the positioning accuracy as well as convergence speed benefit from the fusion of multi-GNSS and higher rate of precise clock corrections. The multi-GNSS PPP improves the positioning accuracy by 10-20%, 40-60%, and 60-80% relative to the GPS-, GLONASS-, and BeiDou-only PPP. The usage of 30 s

Multi-GNSS PPP-RTK : From large- to Small-Scale networks

NARCIS (Netherlands)

Nadarajah, Nandakumaran; Khodabandeh, Amir; Wang, Kan; Choudhury, Mazher; Teunissen, P.J.G.

2018-01-01

Precise point positioning (PPP) and its integer ambiguity resolution-enabled variant, PPP-RTK (real-time kinematic), can benefit enormously from the integration of multiple global navigation satellite systems (GNSS). In such a multi-GNSS landscape, the positioning convergence time is expected to

Research Progress and Prospect of GNSS Space Environment Science

Directory of Open Access Journals (Sweden)

YAO Yibin

2017-10-01

Full Text Available Troposphere and ionosphere are two important components of the near-earth space environment. They are close to the surface of the earth and have great influence on human life. The developments of Global Navigation Satellite System (GNSS over the past several decades provide a great opportunity for the GNSS-based space environment science. This review summarizes the research progress and prospect of the GNSS-based research of the Earth's troposphere and ionosphere. On the tropospheric perspective, modeling of the key tropospheric parameters and inversion of precipitable water vapor (PWV are dominant researching fields. On the ionospheric perspective, 2D/3D ionospheric models and regional/global ionospheric monitoring are dominant researching fields.

Integrated GNSS attitude determination and positioning for direct geo-referencing

NARCIS (Netherlands)

Nadarajah, N.; Paffenholz, J.A.; Teunissen, P.J.G.

2014-01-01

Direct geo-referencing is an efficient methodology for the fast acquisition of 3D spatial data. It requires the fusion of spatial data acquisition sensors with navigation sensors, such as Global Navigation Satellite System (GNSS) receivers. In this contribution, we consider an integrated GNSS

Spoofing Detection Using GNSS/INS/Odometer Coupling for Vehicular Navigation.

Science.gov (United States)

Broumandan, Ali; Lachapelle, Gérard

2018-04-24

Location information is one of the most vital information required to achieve intelligent and context-aware capability for various applications such as driverless cars. However, related security and privacy threats are a major holdback. With increasing focus on using Global Navigation Satellite Systems (GNSS) for autonomous navigation and related applications, it is important to provide robust navigation solutions, yet signal spoofing for illegal or covert transportation and misleading receiver timing is increasing and now frequent. Hence, detection and mitigation of spoofing attacks has become an important topic. Several contributions on spoofing detection have been made, focusing on different layers of a GNSS receiver. This paper focuses on spoofing detection utilizing self-contained sensors, namely inertial measurement units (IMUs) and vehicle odometer outputs. A spoofing detection approach based on a consistency check between GNSS and IMU/odometer mechanization is proposed. To detect a spoofing attack, the method analyses GNSS and IMU/odometer measurements independently during a pre-selected observation window and cross checks the solutions provided by GNSS and inertial navigation solution (INS)/odometer mechanization. The performance of the proposed method is verified in real vehicular environments. Mean spoofing detection time and detection performance in terms of receiver operation characteristics (ROC) in sub-urban and dense urban environments are evaluated.

Spoofing Detection Using GNSS/INS/Odometer Coupling for Vehicular Navigation

Directory of Open Access Journals (Sweden)

Ali Broumandan

2018-04-01

Full Text Available Location information is one of the most vital information required to achieve intelligent and context-aware capability for various applications such as driverless cars. However, related security and privacy threats are a major holdback. With increasing focus on using Global Navigation Satellite Systems (GNSS for autonomous navigation and related applications, it is important to provide robust navigation solutions, yet signal spoofing for illegal or covert transportation and misleading receiver timing is increasing and now frequent. Hence, detection and mitigation of spoofing attacks has become an important topic. Several contributions on spoofing detection have been made, focusing on different layers of a GNSS receiver. This paper focuses on spoofing detection utilizing self-contained sensors, namely inertial measurement units (IMUs and vehicle odometer outputs. A spoofing detection approach based on a consistency check between GNSS and IMU/odometer mechanization is proposed. To detect a spoofing attack, the method analyses GNSS and IMU/odometer measurements independently during a pre-selected observation window and cross checks the solutions provided by GNSS and inertial navigation solution (INS/odometer mechanization. The performance of the proposed method is verified in real vehicular environments. Mean spoofing detection time and detection performance in terms of receiver operation characteristics (ROC in sub-urban and dense urban environments are evaluated.

GLOBAL NAVIGATION SATELLITE SYSTEMS (GNSS IN GEOGRAPHICAL EDUCATION AND APPLIED RESEARCH

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A. A. Suchilin

2017-01-01

Full Text Available The paper considers the introduction of the newest methods of topographic surveying into the educational and scientific process, using global navigation satellite systems (GNSS at the Faculty of Geography of Moscow State University. It describes the designation and use of the current reference geodetic training network for the training of students within the program of topographic practice. The basic concepts and purpose of the equipment of the geodetic class of the user segment of GNSS, both the basic location (reference stations and mobile complexes are disclosed. The technique of measuring and processing the accumulated data after field fixation (in static or kinematic modes of geographic objects and phenomena using GNSS has been given. A constantly operating network of reference stations of the faculty has been described. A full-scale example of using the GNSS complex by students of the faculty of the study area is given, the collected materials have been used for subsequent modeling (relief restoration based on the results of field measurements. Within the framework of the perspective development of the network of GNSS reference stations of the Moscow State University, the scheme of their location in the meridian direction on an ongoing basis has been shown, which will substantially expand the territorial coverage of the use of mobile GNSS complexes in geographic studies. Within the framework of the program of preservation of monuments of Russia’s cultural heritage, an example has been shown of the joint use of groundbased laser scanning techniques and a mobile GNSS complex conducted by students and teachers of leading Moscow universities and representatives of GFK Firm LLC. The result is the fixation of the geometric characteristics of the object in 1 cm steps in real coordinates, which makes it possible to carry out the necessary modeling, visualize the object in perspective form, carry out the necessary measurements, build sections

A PRECISE, LOW-COST RTK GNSS SYSTEM FOR UAV APPLICATIONS

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W. Stempfhuber

2012-09-01

Full Text Available High accuracy with real-time positioning of moving objects has been considered a standard task of engineering geodesy for 10 to 15 years. An absolute positioning accuracy of 1–3 cm is generally possible worldwide and is further used in many areas of machine guidance (machine control and guidance, and farming (precision farming as well as for various special applications (e.g. railway trolley, mining, etc.. The cost of the measuring instruments required for the use of geodetic L1/L2 receivers with a local reference station amounts to approximately USD 30,000 to 50,000. Therefore, dual frequency RTK GNSS receivers are not used in the mass market. Affordable GPS/GNSS modules have already reached the mass market in various areas such as mobile phones, car navigation, the leisure industry, etc. Kinematic real-time positioning applications with centimetre or decimetre levels could also evolve into a mass product. In order for this to happen, the costs for such systems must lie between USD 1,000 to 2,000. What exactly low-cost means is determined by the precise specifications of the given individual application. Several university studies in geodesy focus on the approach of high-accuracy positioning by means of single frequency receivers for static applications [e.g. GLABSCH et. al. 2009, SCHWIEGER and GLÄSER 2005, ALKAN 2010, REALINI et. al. 2010, KORTH and HOFMANN 2011]. Although intelligent approaches have been developed that compute a trajectory in the post-processing mode [REALINI et. al., 2010], at present, there are only a very few GNSS Low-Cost Systems that enable real-time processing. This approach to precise position determination by means of the computation of static raw data with single frequency receivers is currently being explored in a research project at the Beuth Hochschule für Technik Berlin – and is being further developed for kinematic applications. The project is embedded in the European Social Fund. It is a follow-up project

Multi-frequency GNSS robust carrier tracking for ionospheric scintillation mitigation

Science.gov (United States)

Vilà-Valls, Jordi; Closas, Pau; Curran, James T.

2017-10-01

Ionospheric scintillation is the physical phenomena affecting radio waves propagating from the space through the ionosphere to earth. The signal distortion induced by scintillation can pose a major threat to some GNSS application. Scintillation is one of the more challenging propagation scenarios, particularly affecting high-precision GNSS receivers which require high quality carrier phase measurements; and safety critical applications which have strict accuracy, availability and integrity requirements. Under ionospheric scintillation conditions, GNSS signals are affected by fast amplitude and phase variations, which can compromise the receiver synchronization. To take into account the underlying correlation among different frequency bands, we propose a new multivariate autoregressive model (MAR) for the multi-frequency ionospheric scintillation process. Multi-frequency GNSS observations and the scintillation MAR are modeled in state-space, allowing independent tracking of both line-of-sight phase variations and complex gain scintillation components. The resulting joint synchronization and scintillation mitigation problem is solved using a robust nonlinear Kalman filter, validated using real multi-frequency scintillation data with encouraging results.

EPOS-GNSS - Improving the infrastructure for GNSS data and products in Europe

Science.gov (United States)

Fernandes, Rui; Bos, Machiel; Bruyninx, Carine; Crocker, Paul; Dousa, Jan; Socquet, Anne; Walpersdorf, Andrea; Avallone, Antonio; Ganas, Athanassios; Gunnar, Benedikt; Ionescu, Constantin; Kenyeres, Ambrus; Ozener, Haluk; Vergnolle, Mathilde; Lidberg, Martin; Liwosz, Tomek; Soehne, Wolfgang

2017-04-01

EPOS-IP WP10 - "GNSS Data & Products" is the Working Package 10 of the European Plate Observing System - Implementation Phase project in charge of implementing services for the geo-sciences community to access existing Pan-European Geodetic Infrastructures. WP10 is currently formed by representatives of participating European institutions but in the operational phase contributions will be solicited from the entire geodetic community. In fact, WP10 also includes members from other institutions/countries that formally are not participating in the EPOS-IP but will be key players in the future services to be provided by EPOS. Additionally, several partners are also key partners at EUREF, which is also actively collaborating with EPOS. The geodetic component of EPOS is dealing essentially with implementing an e-infrastructure to store and disseminate the continuous GNSS data from existing Research Infrastructures. Present efforts are on developing geodetic tools to support Solid Earth research by optimizing the existing resources. However, other research and technical applications (e.g., reference frames, meteorology, space weather) can also benefit in the future from the optimization of the geodetic resources in Europe. We present and discuss the status of the implementation of the thematic and core services (TCS) for GNSS data within EPOS and the related business plan. We explain the tools and web-services being developed towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the geodetic data, derived solutions, and associated metadata using a transparent and standardized processes. We also detail the different DDSS (Data, Data-Products, Services, Software) that will be made available for the Operational Phase of EPOS, which will start to be tested and made available during 2017 and 2018.

GNSS-based operational monitoring devices for forest logging operation chains

Directory of Open Access Journals (Sweden)

Raimondo Gallo

2013-09-01

Full Text Available The first results of a new approach for implementing operational monitoring tool to control the performance of forest mechanisation chains are proposed and discussed. The solution is based on Global Navigation Satellite System (GNSS tools that are the core of a datalogging system that, in combination with a specific inference-engine, is able to analyse process times, work distances, forward speeds, vehicle tracking and number of working cycles in forest operations. As a consequence the operational monitoring control methods could provide an evaluation of the efficiency of the investigated forest operations. The study has monitored the performance of a tower yarder with crane and processor-head, during logging operations. The field surveys consisted on the installation of the GNSS device directly on the forest equipment for monitoring its movements. Simultaneously the field survey considered the integration of the GNSS information with a time study of work elements based on the continuous time methods supported by a time study board. Additionally, where possible, the onboard computer of the forest machine was also used in order to obtain additional information to be integrated to the GNSS data and the time study. All the recorded GNSS data integrated with the work elements study were thus post-processed through GIS analysis. The preliminary overview about the application of this approach on harvesting operations has permitted to assess a good feasibility of the use of GNSS in the relief of operative times in high mechanised forest chains. Results showed an easy and complete identification of the different operative cycles and elementary operations phases, with a maximum difference between the two methodologies of 10.32%. The use of GNSS installed on forest equipment, integrated with the inferenceengine and also with an interface for data communication or data storage, will permit an automatic or semi-automatic operational monitoring, improving

On the impact of GNSS ambiguity resolution: geometry, ionosphere, time and biases

Science.gov (United States)

Khodabandeh, A.; Teunissen, P. J. G.

2018-06-01

Integer ambiguity resolution (IAR) is the key to fast and precise GNSS positioning and navigation. Next to the positioning parameters, however, there are several other types of GNSS parameters that are of importance for a range of different applications like atmospheric sounding, instrumental calibrations or time transfer. As some of these parameters may still require pseudo-range data for their estimation, their response to IAR may differ significantly. To infer the impact of ambiguity resolution on the parameters, we show how the ambiguity-resolved double-differenced phase data propagate into the GNSS parameter solutions. For that purpose, we introduce a canonical decomposition of the GNSS network model that, through its decoupled and decorrelated nature, provides direct insight into which parameters, or functions thereof, gain from IAR and which do not. Next to this qualitative analysis, we present for the GNSS estimable parameters of geometry, ionosphere, timing and instrumental biases closed-form expressions of their IAR precision gains together with supporting numerical examples.

Use of GNSS derived ionospheric information to detect and measure Solar Flares

OpenAIRE

Hernández Pajares, Manuel; García Rigo, Alberto; Aragón Ángel, María Ángeles

2014-01-01

The Ionosphere, the partially ionized atmospheric r egion ranging from approximately 60 to +1000 km height, is typically affected by spatial and tempor al variations, driven by Local Time (solar illumina - tion), Latitude (magnetic field and solar illuminat ion) and time (space weather, among seasonal and solar cycle dependence). It can be indirectly studi ed from the dual L-band frequency GNSS measure- ments by assuming the first order ionospheric delay approximation (the higher order ionosp...

Uniqueness and nonuniqueness of the GNSS carrier-phase compass readings

NARCIS (Netherlands)

Teunissen, P.J.G.

2009-01-01

In this contribution we analyse the possible nonuniqueness in the least-squares solution of the GNSS carrier-phase compass model. It is shown that this lack of uniqueness may manifest itself in the fixed baseline estimator and therefore in the GNSS compass readings. We present the conditions under

High-rate multi-GNSS: what does it mean to seismology?

Science.gov (United States)

Geng, J.

2017-12-01

GNSS precise point positioning (PPP) is capable of measuring centimeter-level positions epoch by epoch at a single station, and is thus treasured in tsunami/earthquake early warning where static displacements in the near field are critical to rapidly and reliably determining the magnitude of destructive events. However, most operational real-time PPP systems at present rely on only GPS data. The deficiency of such systems is that the high reliability and availability of precise displacements cannot be maintained continuously in real time, which is however a crucial requirement for disaster resistance and response. Multi-GNSS, including GLONASS, BeiDou, Galileo and QZSS other than only GPS, can be a solution to this problem because much more satellites per epoch (e.g. 30-40) will be available. In this case, positioning failure due to data loss or blunders can be minimized, and on the other hand, positioning initializations can be accelerated to a great extent since the satellite geometry for each epoch will be enhanced enormously. We established a prototype real-time multi-GNSS PPP service based on Asia-Pacific real-time network which can collect and stream high-rate data from all five navigation systems above. We estimated high-rate satellite clock corrections and enabled undifferenced ambiguity fixing for multi-GNSS, which therefore ensures high availability and reliability of precise displacement estimates in contrast to GPS-only systems. We will report how we can benefit from multi-GNSS for seismology, especially the noise characteristics of high-rate and sub-daily displacements. We will also use storm surge loading events to demonstrate the contribution of multi-GNSS to sub-daily transient signals.

Contribution of GNSS CORS Infrastructure to the Mission of Modern Geodesy and Status of GNSS CORS in Thailand

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Chalermchon Satirapod

2011-01-01

Full Text Available Geodesy is the science of measuring and mapping the geometry, orientation and gravity field of the Earth including the associated variations with time. Geodesy has also provided the foundation for high accuracy surveying and mapping. Modern Geodesy involves a range of space and terrestrial technologies that contribute to our knowledge of the solid earth, atmosphere and oceans. These technologies include: Global Positioning System/Global Navigation Satellite Systems (GPS/GNSS, Satellite Laser Ranging (SLR, Very Long Baseline Interferometry (VLBI, Satellite Altimetry, Gravity Mapping Missions such as GRACE, CHAMP and GOCE, satelliteborne Differential Interferometric Synthetic Aperture Radar (DInSAR, Absolute and Relative Gravimetry, and Precise Terrestrial Surveying (Levelling and Traversing. A variety of services have been established in recent years to ensure high accuracy and reliable geodetic products to support geoscientific research. The reference frame defined by Modern Geodesy is now the basis for most national and regional datums. Furthermore, the GPS/GNSS technology is a crucial geopositioning tool for both Geodesy and Surveying. There is therefore a blurring of the distinction between geodetic and surveying GPS/GNSS techniques, and increasingly the ground infrastructure of continuously operating reference stations (CORS receivers attempts to address the needs of both geodesists and other positioning professionals. Yet Geodesy is also striving to increase the level of accuracy by a factor of ten over the next decade in order to address the demands of “global change” studies. The Global Geodetic Observing System (GGOS is an important component of the International Association of Geodesy. GGOS aims to integrate all geodetic observations in order to generate a consistent high quality set of geodetic parameters for monitoring the phenomena and processes within the “System Earth”. Integration implies the inclusion of all relevant

Study on a High-frequency Multi-GNSS Real-time Precise Clock Estimation Algorithm and Application in GNSS Augment System

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CHEN Liang

2017-05-01

Full Text Available GNSS satellite-based differential augment system is based on real-time orbit and clock augment message. The multi-GNSS real-time precise clock error estimation model is studied, and then the parameters estimated in traditional un-difference model are optimized and a high-efficient real-time clock simplified model is proposed and realized. The real-time orbit data processing based on PANDA is also analyzed. The results indicate that the real-time orbit radial accuracy of GPS, BeiDou MEO and Galileo is 1~5 cm, and the radial accuracy of the BeiDou GEO/IGSO satellite is about 10 cm. It is found that the optimized real-time clock simplified model is more efficient in one epoch than un-difference model and can be applied to high-frequency (such as 1 Hz updating of real-time clock augment message. The results show that the real-time clock error obtained by this model is absolute value and there is no constant bias. Based on the real-time orbit, the GPS real-time clock precision of the simplified model is about 0.24 ns, BeiDou GEO is about 0.50 ns, IGSO/MEO is about 0.22 ns and Galileo is about 0.32 ns. Using the multi-GNSS real-time data stream in GFZ, a multi-GNSS real-time augment prototype system is built and the real-time augment message is being broadcasted on the Internet. The real-time PPP centimeter-level service and meter-level navigation service based on pseudorange are realized based on this prototype system.

Prediction of GNSS satellite clocks

International Nuclear Information System (INIS)

Broederbauer, V.

2010-01-01

This thesis deals with the characterisation and prediction of GNSS-satellite-clocks. A prerequisite to develop powerful algorithms for the prediction of clock-corrections is the thorough study of the behaviour of the different clock-types of the satellites. In this context the predicted part of the IGU-clock-corrections provided by the Analysis Centers (ACs) of the IGS was compared to the IGS-Rapid-clock solutions to determine reasonable estimates of the quality of already existing well performing predictions. For the shortest investigated interval (three hours) all ACs obtain almost the same accuracy of 0,1 to 0,4 ns. For longer intervals the individual predictions results start to diverge. Thus, for a 12-hours- interval the differences range from nearly 10 ns (GFZ, CODE) until up to some 'tens of ns'. Based on the estimated clock corrections provided via the IGS Rapid products a simple quadratic polynomial turns out to be sufficient to describe the time series of Rubidium-clocks. On the other hand Cesium-clocks show a periodical behaviour (revolution period) with an amplitude of up to 6 ns. A clear correlation between these amplitudes and the Sun elevation angle above the orbital planes can be demonstrated. The variability of the amplitudes is supposed to be caused by temperature-variations affecting the oscillator. To account for this periodical behaviour a quadratic polynomial with an additional sinus-term was finally chosen as prediction model both for the Cesium as well as for the Rubidium clocks. The three polynomial-parameters as well as amplitude and phase shift of the periodic term are estimated within a least-square-adjustment by means of program GNSS-VC/static. Input-data are time series of the observed part of the IGU clock corrections. With the estimated parameters clock-corrections are predicted for various durations. The mean error of the prediction of Rubidium-clock-corrections for an interval of six hours reaches up to 1,5 ns. For the 12-hours

New Quality Control Algorithm Based on GNSS Sensing Data for a Bridge Health Monitoring System

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Jae Kang Lee

2016-05-01

Full Text Available This research introduces an improvement plan for the reliability of Global Navigation Satellite System (GNSS positioning solutions. It should be considered the most suitable methodology in terms of the adjustment and positioning of GNSS in order to maximize the utilization of GNSS applications. Though various studies have been conducted with regards to Bridge Health Monitoring System (BHMS based on GNSS, the outliers which depend on the signal reception environment could not be considered until now. Since these outliers may be connected to GNSS data collected from major bridge members, which can reduce the reliability of a whole monitoring system through the delivery of false information, they should be detected and eliminated in the previous adjustment stage. In this investigation, the Detection, Identification, Adaptation (DIA technique was applied and implemented through an algorithm. Moreover, it can be directly applied to GNSS data collected from long span cable stayed bridges and most of outliers were efficiently detected and eliminated simultaneously. By these effects, the reliability of GNSS should be enormously improved. Improvement on GNSS positioning accuracy is directly linked to the safety of bridges itself, and at the same time, the reliability of monitoring systems in terms of the system operation can also be increased.

Detection of GNSS Signals Propagation in Urban Canyos Using 3D City Models

Directory of Open Access Journals (Sweden)

Petra Pisova

2015-01-01

Full Text Available This paper presents one of the solutions to the problem of multipath propagation and effects on Global Navigation Satellite Systems (GNSS signals in urban canyons. GNSS signals may reach a receiver not only through Line-of-Sight (LOS paths, but they are often blocked, reflected or diffracted from tall buildings, leading to unmodelled GNSS errors in position estimation. Therefore in order to detect and mitigate the impact of multipath, a new ray-tracing model for simulation of GNSS signals reception in urban canyons is proposed - based on digital 3D maps information, known positions of GNSS satellites and an assumed position of a receiver. The model is established and validated using experimental, as well as real data. It is specially designed for complex environments and situations where positioning with highest accuracy is required - a typical example is navigation for blind people.

Multi-frequency GNSS robust carrier tracking for ionospheric scintillation mitigation

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Vilà-Valls Jordi

2017-01-01

Full Text Available Ionospheric scintillation is the physical phenomena affecting radio waves propagating from the space through the ionosphere to earth. The signal distortion induced by scintillation can pose a major threat to some GNSS application. Scintillation is one of the more challenging propagation scenarios, particularly affecting high-precision GNSS receivers which require high quality carrier phase measurements; and safety critical applications which have strict accuracy, availability and integrity requirements. Under ionospheric scintillation conditions, GNSS signals are affected by fast amplitude and phase variations, which can compromise the receiver synchronization. To take into account the underlying correlation among different frequency bands, we propose a new multivariate autoregressive model (MAR for the multi-frequency ionospheric scintillation process. Multi-frequency GNSS observations and the scintillation MAR are modeled in state-space, allowing independent tracking of both line-of-sight phase variations and complex gain scintillation components. The resulting joint synchronization and scintillation mitigation problem is solved using a robust nonlinear Kalman filter, validated using real multi-frequency scintillation data with encouraging results.

The Impact of Eclipsing GNSS Satellites on the Precise Point Positioning

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Xinyun Cao

2018-01-01

Full Text Available When satellites enter into the noon maneuver or the shadow crossing regimes, the actual attitudes will depart from their nominal values. If improper attitude models are used, the induced-errors due to the wind-up effect and satellite antenna PCO (Phase Center Offset will deteriorate the positioning accuracy. Because different generations of satellites adopt different attitude control models, the influences on the positioning performances deserve further study. Consequently, the impact of three eclipsing strategies on the single-system and multi-GNSS (Global Navigation Satellite System Precise Point Positioning (PPP are analyzed. According to the results of the eclipsing monitor, 65 globally distributed MGEX (Multi-GNSS EXperiment stations for 31-day period in July 2017 are selected to perform G/R/E/C/GR/GREC PPP in both static and kinematic modes. The results show that the influences of non-nominal attitudes are related to the magnitude of the PCO values, maximum yaw angle differences, the duration of maneuver, the value of the sun angle and the satellite geometric strength. For single-system, using modeled attitudes rather than the nominal ones will greatly improve the positioning accuracy of GLONASS-only and BDS-only PPP while slightly contributions to the GPS-only and GALILEO-only PPP. Deleting the eclipsing satellites may sometimes induce a longer convergence time and a worse solution due to the poor satellite geometry, especially for GLONASS kinematic PPP when stations are located in the low latitude and BDS kinematic PPP. When multi-GNSS data are available, especially four navigation systems, the accuracy improvements of using the modeled attitudes or deleting eclipsing satellites are non-significant.

Seymour Benzer and T4 rII

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 13; Issue 10. Seymour Benzer and T4 rII - Running the Map into the Ground. R Jayaraman. General Article Volume 13 Issue 10 October 2008 pp 898-908. Fulltext. Click here to view fulltext PDF. Permanent link:

Glutamate Ligation in the Ni(II)- and Co(II)-Responsive Escherichia coli Transcriptional Regulator, RcnR

Energy Technology Data Exchange (ETDEWEB)

Carr, Carolyn E. [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States; Musiani, Francesco [Laboratory; Huang, Hsin-Ting [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States; Chivers, Peter T. [Departments of Biosciences and Chemistry, Durham University, Durham DH1 3LE, United Kingdom; Ciurli, Stefano [Laboratory; Maroney, Michael J. [Department of Chemistry, University of Massachusetts, Amherst, Massachusetts 01003, United States

2017-05-18

Escherichia coli RcnR (resistance to cobalt and nickel regulator, EcRcnR) is a metal-responsive repressor of the genes encoding the Ni(II) and Co(II) exporter proteins RcnAB by binding to PRcnAB. The DNA binding affinity is weakened when the cognate ions Ni(II) and Co(II) bind to EcRcnR in a six-coordinate site that features a (N/O)5S ligand donor-atom set in distinct sites: while both metal ions are bound by the N terminus, Cys35, and His64, Co(II) is additionally bound by His3. On the other hand, the noncognate Zn(II) and Cu(I) ions feature a lower coordination number, have a solvent-accessible binding site, and coordinate protein ligands that do not include the N-terminal amine. A molecular model of apo-EcRcnR suggested potential roles for Glu34 and Glu63 in binding Ni(II) and Co(II) to EcRcnR. The roles of Glu34 and Glu63 in metal binding, metal selectivity, and function were therefore investigated using a structure/function approach. X-ray absorption spectroscopy was used to assess the structural changes in the Ni(II), Co(II), and Zn(II) binding sites of Glu → Ala and Glu → Cys variants at both positions. The effect of these structural alterations on the regulation of PrcnA by EcRcnR in response to metal binding was explored using LacZ reporter assays. These combined studies indicate that while Glu63 is a ligand for both metal ions, Glu34 is a ligand for Co(II) but possibly not for Ni(II). The Glu34 variants affect the structure of the cognate metal sites, but they have no effect on the transcriptional response. In contrast, the Glu63 variants affect both the structure and transcriptional response, although they do not completely abolish the function of EcRcnR. The structure of the Zn(II) site is not significantly perturbed by any of the glutamic acid variations. The spectroscopic and functional data obtained on the mutants were used to calculate models of the metal-site structures of EcRcnR bound to Ni(II), Co(II), and Zn(II). The results are interpreted

Ubiquitous and Seamless Localization: Fusing GNSS Pseudoranges and WLAN Signal Strengths

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Philipp Richter

2017-01-01

Full Text Available Ubiquitous global positioning is not feasible by GNSS alone, as it lacks accurate position fixes in dense urban centres and indoors. Hybrid positioning methods have been developed to aid GNSS in those environments. Fingerprinting localization in wireless local area networks (WLANs is a promising aiding system because of its availability, accuracy, and error mechanisms opposed to that of GNSS. This article presents a low-cost approach to ubiquitous, seamless positioning based on a particle filter integrating GNSS pseudoranges and WLAN received signal strength indicators (RSSIs. To achieve accurate location estimates indoors/outdoors and in the transition zones, appropriate likelihood functions are essential as they determine the influence of each sensor information on the position estimate. We model the spatial RSSI distributions with Gaussian processes and use these models to predict RSSIs at the particle’s positions to obtain point estimates of the RSSI likelihood function. The particle filter’s performance is assessed with real data of two test trajectories in an environment challenging for GNSS and WLAN fingerprinting localization. Outcomes of an extended Kalman filter using pseudoranges and a WLAN position as observation is included as benchmark. The proposed algorithm achieves accurate and robust seamless localization with a median accuracy of five meters.

Comparing Global Positioning System (GPS) and Global Navigation Satellite System (GNSS) Measures of Team Sport Movements.

Science.gov (United States)

Jackson, Benjamin M; Polglaze, Ted; Dawson, Brian; King, Trish; Peeling, Peter

2018-02-21

To compare data from conventional GPS and new GNSS-enabled tracking devices, and to examine the inter-unit reliability of GNSS devices. Inter-device differences between 10 Hz GPS and GNSS devices were examined during laps (n=40) of a simulated game circuit (SGC) and during elite hockey matches (n=21); GNSS inter-unit reliability was also examined during the SGC laps. Differences in distance values and measures in three velocity categories (low 5 m.s -1 ) and acceleration/deceleration counts (>1.46 m.s -2 and GPS devices in all conditions. These findings suggest that GNSS devices may be more sensitive than GPS in quantifying the physical demands of team sport movements, but further study into the accuracy of GNSS devices is required.

Performance Improvement of Receivers Based on Ultra-Tight Integration in GNSS-Challenged Environments

Directory of Open Access Journals (Sweden)

Feng Qin

2013-12-01

Full Text Available Ultra-tight integration was first proposed by Abbott in 2003 with the purpose of integrating a global navigation satellite system (GNSS and an inertial navigation system (INS. This technology can improve the tracking performances of a receiver by reconfiguring the tracking loops in GNSS-challenged environments. In this paper, the models of all error sources known to date in the phase lock loops (PLLs of a standard receiver and an ultra-tightly integrated GNSS/INS receiver are built, respectively. Based on these models, the tracking performances of the two receivers are compared to verify the improvement due to the ultra-tight integration. Meanwhile, the PLL error distributions of the two receivers are also depicted to analyze the error changes of the tracking loops. These results show that the tracking error is significantly reduced in the ultra-tightly integrated GNSS/INS receiver since the receiver’s dynamics are estimated and compensated by an INS. Moreover, the mathematical relationship between the tracking performances of the ultra-tightly integrated GNSS/INS receiver and the quality of the selected inertial measurement unit (IMU is derived from the error models and proved by the error comparisons of four ultra-tightly integrated GNSS/INS receivers aided by different grade IMUs.

Deriving surface soil moisture from reflected GNSS signal observations from a grassland site in southwestern France

Science.gov (United States)

Zhang, Sibo; Calvet, Jean-Christophe; Darrozes, José; Roussel, Nicolas; Frappart, Frédéric; Bouhours, Gilles

2018-03-01

This work assesses the estimation of surface volumetric soil moisture (VSM) using the global navigation satellite system interferometric reflectometry (GNSS-IR) technique. Year-round observations were acquired from a grassland site in southwestern France using an antenna consecutively placed at two contrasting heights above the ground surface (3.3 and 29.4 m). The VSM retrievals are compared with two independent reference datasets: in situ observations of soil moisture, and numerical simulations of soil moisture and vegetation biomass from the ISBA (Interactions between Soil, Biosphere and Atmosphere) land surface model. Scaled VSM estimates can be retrieved throughout the year removing vegetation effects by the separation of growth and senescence periods and by the filtering of the GNSS-IR observations that are most affected by vegetation. Antenna height has no significant impact on the quality of VSM estimates. Comparisons between the VSM GNSS-IR retrievals and the in situ VSM observations at a depth of 5 cm show good agreement (R2 = 0.86 and RMSE = 0.04 m3 m-3). It is shown that the signal is sensitive to the grass litter water content and that this effect triggers differences between VSM retrievals and in situ VSM observations at depths of 1 and 5 cm, especially during light rainfall events.

GNSS Precise Kinematic Positioning for Multiple Kinematic Stations Based on A Priori Distance Constraints

Science.gov (United States)

He, Kaifei; Xu, Tianhe; Förste, Christoph; Petrovic, Svetozar; Barthelmes, Franz; Jiang, Nan; Flechtner, Frank

2016-01-01

When applying the Global Navigation Satellite System (GNSS) for precise kinematic positioning in airborne and shipborne gravimetry, multiple GNSS receiving equipment is often fixed mounted on the kinematic platform carrying the gravimetry instrumentation. Thus, the distances among these GNSS antennas are known and invariant. This information can be used to improve the accuracy and reliability of the state estimates. For this purpose, the known distances between the antennas are applied as a priori constraints within the state parameters adjustment. These constraints are introduced in such a way that their accuracy is taken into account. To test this approach, GNSS data of a Baltic Sea shipborne gravimetric campaign have been used. The results of our study show that an application of distance constraints improves the accuracy of the GNSS kinematic positioning, for example, by about 4 mm for the radial component. PMID:27043580

Continuous Fine-Fault Estimation with Real-Time GNSS

Science.gov (United States)

Norford, B. B.; Melbourne, T. I.; Szeliga, W. M.; Santillan, V. M.; Scrivner, C.; Senko, J.; Larsen, D.

2017-12-01

Thousands of real-time telemetered GNSS stations operate throughout the circum-Pacific that may be used for rapid earthquake characterization and estimation of local tsunami excitation. We report on the development of a GNSS-based finite-fault inversion system that continuously estimates slip using real-time GNSS position streams from the Cascadia subduction zone and which is being expanded throughout the circum-Pacific. The system uses 1 Hz precise point position streams computed in the ITRF14 reference frame using clock and satellite orbit corrections from the IGS. The software is implemented as seven independent modules that filter time series using Kalman filters, trigger and estimate coseismic offsets, invert for slip using a non-negative least squares method developed by Lawson and Hanson (1974) and elastic half-space Green's Functions developed by Okada (1985), smooth the results temporally and spatially, and write the resulting streams of time-dependent slip to a RabbitMQ messaging server for use by downstream modules such as tsunami excitation modules. Additional fault models can be easily added to the system for other circum-Pacific subduction zones as additional real-time GNSS data become available. The system is currently being tested using data from well-recorded earthquakes including the 2011 Tohoku earthquake, the 2010 Maule earthquake, the 2015 Illapel earthquake, the 2003 Tokachi-oki earthquake, the 2014 Iquique earthquake, the 2010 Mentawai earthquake, the 2016 Kaikoura earthquake, the 2016 Ecuador earthquake, the 2015 Gorkha earthquake, and others. Test data will be fed to the system and the resultant earthquake characterizations will be compared with published earthquake parameters. Seismic events will be assumed to occur on major faults, so, for example, only the San Andreas fault will be considered in Southern California, while the hundreds of other faults in the region will be ignored. Rake will be constrained along each subfault to be

Seismic displacements monitoring for 2015 Mw 7.8 Nepal earthquake with GNSS data

Science.gov (United States)

Geng, T.; Su, X.; Xie, X.

2017-12-01

The high-rate Global Positioning Satellite System (GNSS) has been recognized as one of the powerful tools for monitoring ground motions generated by seismic events. The high-rate GPS and BDS data collected during the 2015 Mw 7.8 Nepal earthquake have been analyzed using two methods, that are the variometric approach and Precise point positioning (PPP). The variometric approach is based on time differenced technique using only GNSS broadcast products to estimate velocity time series from tracking observations in real time, followed by an integration procedure on the velocities to derive the seismic event induced displacements. PPP is a positioning method to calculate precise positions at centimeter- or even millimeter-level accuracy with a single GNSS receiver using precise satellite orbit and clock products. The displacement motions with accuracy of 2 cm at far-field stations and 5 cm at near-field stations with great ground motions and static offsets up to 1-2 m could be achieved. The multi-GNSS, GPS + BDS, could provide higher accuracy displacements with the increasing of satellite numbers and the improvement of the Position Dilution of Precision (PDOP) values. Considering the time consumption of clock estimates and the precision of PPP solutions, 5 s GNSS satellite clock interval is suggested. In addition, the GNSS-derived displacements are in good agreement with those from strong motion data. These studies demonstrate the feasibility of real-time capturing seismic waves with multi-GNSS observations, which is of great promise for the purpose of earthquake early warning and rapid hazard assessment.

Development of GNSS PWV information management system for very short-term weather forecast in the Korean Peninsula

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Park, Han-Earl; Yoon, Ha Su; Yoo, Sung-Moon; Cho, Jungho

2017-04-01

Over the past decade, Global Navigation Satellite System (GNSS) was in the spotlight as a meteorological research tool. The Korea Astronomy and Space Science Institute (KASI) developed a GNSS precipitable water vapor (PWV) information management system to apply PWV to practical applications, such as very short-term weather forecast. The system consists of a DPR, DRS, and TEV, which are divided functionally. The DPR processes GNSS data using the Bernese GNSS software and then retrieves PWV from zenith total delay (ZTD) with the optimized mean temperature equation for the Korean Peninsula. The DRS collects data from eighty permanent GNSS stations in the southern part of the Korean Peninsula and provides the PWV retrieved from GNSS data to a user. The TEV is in charge of redundancy of the DPR. The whole process is performed in near real-time where the delay is ten minutes. The validity of the GNSS PWV was proved by means of a comparison with radiosonde data. In the experiment of numerical weather prediction model, the GNSS PWV was utilized as the initial value of the Weather Research & Forecasting (WRF) model for heavy rainfall event. As a result, we found that the forecasting capability of the WRF is improved by data assimilation of GNSS PWV.

Review of crop growth and soil moisture monitoring from a ground-based instrument implementing the Interference Pattern GNSS-R Technique

Science.gov (United States)

Rodriguez-Alvarez, N.; Bosch-Lluis, X.; Camps, A.; Aguasca, A.; Vall-Llossera, M.; Valencia, E.; Ramos-Perez, I.; Park, H.

2011-12-01

Reflectometry using Global Navigation Satellite Systems signals (GNSSR) has been the focus of many studies during the past few years for a number of applications over different scenarios as land, ocean or snow and ice surfaces. In the past decade, its potential has increased yearly, with improved receivers and signal processors, from generic GNSS receivers whose signals were recorded in magnetic tapes to instruments that measure full Delay Doppler Maps (the power distribution of the reflected GNSS signal over the 2-D space of delay offsets and Doppler shifts) in real time. At present, these techniques are considered to be promising tools to retrieve geophysical parameters such as soil moisture, vegetation height, topography, altimetry, sea state and ice and snow thickness, among others. This paper focuses on the land geophysical retrievals (topography, vegetation height and soil moisture) performed from a ground-based instrument using the Interference Pattern Technique (IPT). This technique consists of the measurement of the power fluctuations of the interference signal resulting from the simultaneous reception of the direct and the reflected GNSS signals. The latest experiment performed using this technique over a maize field is shown in this paper. After a review of the previous results, this paper presents the latest experiment performed using this technique over a maize field. This new study provides a deeper analysis on the soil moisture retrieval by observing three irrigation-drying cycles and comparing them to different depths soil moisture probes. Furthermore, the height of the maize, almost 300 cm, has allowed testing the capabilities of the technique over dense and packed vegetation layers, with high vegetation water content.

Combination of precise GNSS orbit and clock solutions in a multi-constellation, multi-frequency environment

Science.gov (United States)

Ortiz Geist, Estefania

2015-04-01

Precise GNSS orbit and clock solutions are essential for the generation of the Terrestrial Reference Frame (TRF) and required for a broad variety of applications. Over the last decades the combination products of the International GNSS Service (IGS) have become the standard for all kinds of GNSS applications requiring highest accuracy. The emerging new GNSS constellations Galileo, BeiDou and the QZSS as well as the modernization of the already established GPS and GLONASS constellations will stimulate a new development in the GNSS data processing in order to gain be best benefit from the new signals and systems for geodetic and geodynamic applications. This introduces the question regarding the influence of this development on the orbit and clock products. What are the consequences for the consistency of the contributions from the Analysis Centres (ACs) of the IGS and how does the combination procedure need to react on his development? Another set of questions is related to the expected scenario in which not all IGS ACs will likely include all GNSS. The algorithm for the orbit and clock combination needs to be adapted for a multi-system combination to keep on one hand the internal consistency between the GNSS during the combination procedure but also consider the differences in the expected orbit qualities between the satellite systems (e.g., due to the number of satellites or network coverage). To investigate these questions ESOC and AIUB have agreed on a joint research fellowship for three years. The objective of this research is to analyse the capabilities and challenges when combining hybrid multi-GNSS solutions and to develop a concept, which compares and combines orbit and clock contributions to come up with a consistent, reliable, truly combined multi-GNSS combination product. Well-defined test scenarios shall be constructed and analysed based on the GNSS data processing software packages in the two institutions, namely "NAPEOS" and "Bernese GNSS Software

What is the cost per millimetre? Challenging traditional GNSS equipment for precise geosciences and engineering applications

Science.gov (United States)

Hogg, William; Boreham, Nicholas; Benedetti, Elisa; Roberts, William

2017-04-01

Surveyors, civil and geotechnical engineers are the typical users of professional grade GNSS receiver that is capable of achieving positioning accuracies of sub-centimetre and navigation accuracies of 1-2cm. When choosing the equipment for their needs, they are often faced with a dilemma with each additional frequency, constellation and feature coming at a cost, resulting in professional GNSS equipment being regarded as high-priced specialist equipment. Indeed there are many users that have discounted GNSS on the grounds that it is too expensive and too operationally complex to warrant purchase. Having identified this situation, Nottingham Scientific Ltd (NSL) set about the development of equipment that would break down this barrier making high accuracy GNSS affordable to new users and applications and more cost effective to existing users. NSL created "STICK" which is a single frequency, multi-constellation, IMU-integrated GNSS sensor for precise movement detection of the natural and built environments and infrastructures, at approximately 1/20th of the price of a professional grade GNSS system. STICK has been developed within the context of three European Space Agency (ESA) Integrated Applications Programme Demonstration projects that use space assets to monitor the land stability and the status of different types of infrastructure, each with its own operational challenges. However through the careful selection of components, the implementation of certain operational constraints and the use of advanced statistical data processing, sub-centimetre positioning can be achieved for monitoring purposes. This paper describes STICK, the applications for which it has been developed, and the environments within which it is operating. We then explore the performance by directly comparing STICK to geodetic GNSS receivers setup in an operational, test bed environment. This test bed allows the receivers/antennas to be subjected to a three-dimensional displacement in the order

Single-baseline RTK GNSS Positioning for Hydrographic Surveying

Science.gov (United States)

Metin Alkan, Reha; Murat Ozulu, I.; Ilçi, Veli; Kahveci, Muzaffer

2015-04-01

Positioning with GNSS technique can be carried out in two ways, absolute and relative. It has been possible to reach a few meters absolute point positioning accuracies in real time after disabling SA permanently in May 2000. Today, accuracies obtainable from absolute point positioning using code observations are not sufficient for most surveying applications. Thus to meet higher accuracy requirements, differential methods using single or dual frequency geodetic-grade GNSS receivers that measure carrier phase have to be used. However, this method requires time-cost field and office works and if the measurement is not carried out with conventional RTK method, user needs a GNSS data processing software to estimate the coordinates. If RTK is used, at least two or more GNSS receivers are required, one as a reference and the other as a rover. Moreover, the distance between the receivers must not exceed 15-20 km in order to be able to rapidly and reliably resolve the carrier phase ambiguities. On the other hand, based on the innovations and improvements in satellite geodesy and GNSS modernization studies occurred within the last decade, many new positioning methods and new approaches have been developed. One of them is Network-RTK (or commonly known as CORS) and the other is Single-baseline RTK. These methods are widely used for many surveying applications in many countries. The user of the system can obtain his/her position within a few cm level of accuracy in real-time with only a single GNSS receiver that has Network RTK (CORS) capability. When compared with the conventional differential and RTK methods, this technique has several significant advantages as it is easy to use and it produces accurate, cost-effective and rapid solutions. In Turkey, establishment of a multi-base RTK network was completed and opened for civilian use in 2009. This network is called CORS-TR and consists of 146 reference stations having about 80-100 km interstation distances. It is possible

Applying the GNSS Volcanic Ash Plume Detection Technique to Consumer Navigation Receivers

Science.gov (United States)

Rainville, N.; Palo, S.; Larson, K. M.

2017-12-01

Global Navigation Satellite Systems (GNSS) such as the Global Positioning System (GPS) rely on predictably structured and constant power RF signals to fulfill their primary use for navigation and timing. When the received strength of GNSS signals deviates from the expected baseline, it is typically due to a change in the local environment. This can occur when signal reflections from the ground are modified by changes in snow or soil moisture content, as well as by attenuation of the signal from volcanic ash. This effect allows GNSS signals to be used as a source for passive remote sensing. Larson et al. (2017) have developed a detection technique for volcanic ash plumes based on the attenuation seen at existing geodetic GNSS sites. Since these existing networks are relatively sparse, this technique has been extended to use lower cost consumer GNSS receiver chips to enable higher density measurements of volcanic ash. These low-cost receiver chips have been integrated into a fully stand-alone sensor, with independent power, communications, and logging capabilities as part of a Volcanic Ash Plume Receiver (VAPR) network. A mesh network of these sensors transmits data to a local base-station which then streams the data real-time to a web accessible server. Initial testing of this sensor network has uncovered that a different detection approach is necessary when using consumer GNSS receivers and antennas. The techniques to filter and process the lower quality data from consumer receivers will be discussed and will be applied to initial results from a functioning VAPR network installation.

Multi-GNSS Opportunities and Challenges

Science.gov (United States)

Al-Shaery, A.; Zhang, S.; Lim, S.; Rizos, C.

2012-04-01

The multi-GNSS era has began attracting more attention with the declaration of full operational capability of GLONASS , with a 24 satellites being set to 'healthy' on December 8th 2011 (IAC, 2011). This means that GPS is no longer the only GNSS that provides global positioning coverage. This status brings benefits for GNSS users in areas (e.g. 'urban canyon' environments or in deep open cut mines) where the number of visible satellites is limited because of shadowing effects. In such areas adding more functioning satellites, which is one of the aiding solutions, becomes easier, at no extra cost. The inclusion of GLONASS observations in positioning solutions will increase the available number of satellites and thus positioning accuracy may improve as a result of enhanced overall satellite geometry. Such an aiding solution is increasingly attractive due to the successful revitalisation of GLONASS. Another motivation is the availability of improved GLONASS orbits from the IGS and individual analysis centres of the IGS. The increasing availability of receivers with GPS/GLONASS tracking capability on the market is an additional motive. Consequently, most networks of continuously operating reference stations (CORS) are now equipped with receivers that can track both GPS and GLONASS satellite signals, and therefore network-based positioning with combined GPS and GLONASS observations is possible. However, adding GLONASS observations to GPS is not a straight forward process. This is attributable to a few system differences in reference frames for time and coordinates, and in signal structures. The first two differences are easy to deal with using well-defined conversion and transformation parameters (El-Mowafy, 2001). However, signal structure differences have some implications. The mathematical modelling of combined GPS/GLONASS observations is not performed as in the case of GPS-alone. Special care should be paid to such integration. Not only is the software part affected

The Location GNSS Modules for the Components of Proteus System

Science.gov (United States)

Brzostowski, K.; Darakchiev, R.; Foks-Ryznar, A.; Sitek, P.

2012-01-01

The Proteus system - the Integrated Mobile System for Counterterrorism and Rescue Operations is a complex innovative project. To assure the best possible localization of mobile components of the system, many different Global Navigation Satellite System (GNSS) modules were taken into account. In order to chose the best solution many types of tests were done. Full results and conclusions are presented in this paper. The idea of measurements was to test modules in GPS Standard Positioning Service (SPS) with EGNOS system specification according to certain algorithms. The tests had to answer the question: what type of GNSS modules should be used on different components with respect to specific usage of Proteus system. The second goal of tests was to check the solution quality of integrated GNSS/INS (Inertial Navigation System) and its possible usage in some Proteus system components.

Review of the state of the art and future prospects of the ground-based GNSS meteorology in Europe

Directory of Open Access Journals (Sweden)

G. Guerova

2016-11-01

Full Text Available Global navigation satellite systems (GNSSs have revolutionised positioning, navigation, and timing, becoming a common part of our everyday life. Aside from these well-known civilian and commercial applications, GNSS is now an established atmospheric observing system, which can accurately sense water vapour, the most abundant greenhouse gas, accounting for 60–70 % of atmospheric warming. In Europe, the application of GNSS in meteorology started roughly two decades ago, and today it is a well-established field in both research and operation. This review covers the state of the art in GNSS meteorology in Europe. The advances in GNSS processing for derivation of tropospheric products, application of GNSS tropospheric products in operational weather prediction and application of GNSS tropospheric products for climate monitoring are discussed. The GNSS processing techniques and tropospheric products are reviewed. A summary of the use of the products for validation and impact studies with operational numerical weather prediction (NWP models as well as very short weather prediction (nowcasting case studies is given. Climate research with GNSSs is an emerging field of research, but the studies so far have been limited to comparison with climate models and derivation of trends. More than 15 years of GNSS meteorology in Europe has already achieved outstanding cooperation between the atmospheric and geodetic communities. It is now feasible to develop next-generation GNSS tropospheric products and applications that can enhance the quality of weather forecasts and climate monitoring. This work is carried out within COST Action ES1206 advanced global navigation satellite systems tropospheric products for monitoring severe weather events and climate (GNSS4SWEC, http://gnss4swec.knmi.nl.

An efficient solution of real-time data processing for multi-GNSS network

Science.gov (United States)

Gong, Xiaopeng; Gu, Shengfeng; Lou, Yidong; Zheng, Fu; Ge, Maorong; Liu, Jingnan

2017-12-01

Global navigation satellite systems (GNSS) are acting as an indispensable tool for geodetic research and global monitoring of the Earth, and they have been rapidly developed over the past few years with abundant GNSS networks, modern constellations, and significant improvement in mathematic models of data processing. However, due to the increasing number of satellites and stations, the computational efficiency becomes a key issue and it could hamper the further development of GNSS applications. In this contribution, this problem is overcome from the aspects of both dense linear algebra algorithms and GNSS processing strategy. First, in order to fully explore the power of modern microprocessors, the square root information filter solution based on the blocked QR factorization employing as many matrix-matrix operations as possible is introduced. In addition, the algorithm complexity of GNSS data processing is further decreased by centralizing the carrier-phase observations and ambiguity parameters, as well as performing the real-time ambiguity resolution and elimination. Based on the QR factorization of the simulated matrix, we can conclude that compared to unblocked QR factorization, the blocked QR factorization can greatly improve processing efficiency with a magnitude of nearly two orders on a personal computer with four 3.30 GHz cores. Then, with 82 globally distributed stations, the processing efficiency is further validated in multi-GNSS (GPS/BDS/Galileo) satellite clock estimation. The results suggest that it will take about 31.38 s per epoch for the unblocked method. While, without any loss of accuracy, it only takes 0.50 and 0.31 s for our new algorithm per epoch for float and fixed clock solutions, respectively.

Deriving surface soil moisture from reflected GNSS signal observations from a grassland site in southwestern France

Directory of Open Access Journals (Sweden)

S. Zhang

2018-03-01

Full Text Available This work assesses the estimation of surface volumetric soil moisture (VSM using the global navigation satellite system interferometric reflectometry (GNSS-IR technique. Year-round observations were acquired from a grassland site in southwestern France using an antenna consecutively placed at two contrasting heights above the ground surface (3.3 and 29.4 m. The VSM retrievals are compared with two independent reference datasets: in situ observations of soil moisture, and numerical simulations of soil moisture and vegetation biomass from the ISBA (Interactions between Soil, Biosphere and Atmosphere land surface model. Scaled VSM estimates can be retrieved throughout the year removing vegetation effects by the separation of growth and senescence periods and by the filtering of the GNSS-IR observations that are most affected by vegetation. Antenna height has no significant impact on the quality of VSM estimates. Comparisons between the VSM GNSS-IR retrievals and the in situ VSM observations at a depth of 5 cm show good agreement (R2 =  0.86 and RMSE  =  0.04 m3 m−3. It is shown that the signal is sensitive to the grass litter water content and that this effect triggers differences between VSM retrievals and in situ VSM observations at depths of 1 and 5 cm, especially during light rainfall events.

Biases in GNSS-Data Processing

Science.gov (United States)

Schaer, S. C.; Dach, R.; Lutz, S.; Meindl, M.; Beutler, G.

2010-12-01

Within the Global Positioning System (GPS) traditionally different types of pseudo-range measurements (P-code, C/A-code) are available on the first frequency that are tracked by the receivers with different technologies. For that reason, P1-C1 and P1-P2 Differential Code Biases (DCB) need to be considered in a GPS data processing with a mix of different receiver types. Since the Block IIR-M series of GPS satellites also provide C/A-code on the second frequency, P2-C2 DCB need to be added to the list of biases for maintenance. Potential quarter-cycle biases between different phase observables (specifically L2P and L2C) are another issue. When combining GNSS (currently GPS and GLONASS), careful consideration of inter-system biases (ISB) is indispensable, in particular when an adequate combination of individual GLONASS clock correction results from different sources (using, e.g., different software packages) is intended. Facing the GPS and GLONASS modernization programs and the upcoming GNSS, like the European Galileo and the Chinese Compass, an increasing number of types of biases is expected. The Center for Orbit Determination in Europe (CODE) is monitoring these GPS and GLONASS related biases for a long time based on RINEX files of the tracking network of the International GNSS Service (IGS) and in the frame of the data processing as one of the global analysis centers of the IGS. Within the presentation we give an overview on the stability of the biases based on the monitoring. Biases derived from different sources are compared. Finally, we give an outlook on the potential handling of such biases with the big variety of signals and systems expected in the future.

A High-Level Functional Architecture for GNSS-Based Road Charging Systems

DEFF Research Database (Denmark)

Zabic, Martina

2011-01-01

, a short introduction is provided followed by a presentation of the system engineering methodology to illustrate how and why system architectures can be beneficial for GNSS-based road charging systems. Hereafter, a basic set of system functions is determined based on functional system requirements, which...... charging systems, it is important to highlight the overall system architecture which is the framework that defines the basic functions and important concepts of the system. This paper presents a functional architecture for GNSS-based road charging systems based on the concepts of system engineering. First...... defines the necessary tasks that these systems must accomplish. Finally, this paper defines the system functionalities; and provides a generic high-level functional architecture for GNSS-based road charging systems....

Tightly-Coupled GNSS/Vision Using a Sky-Pointing Camera for Vehicle Navigation in Urban Areas.

Science.gov (United States)

Gakne, Paul Verlaine; O'Keefe, Kyle

2018-04-17

This paper presents a method of fusing the ego-motion of a robot or a land vehicle estimated from an upward-facing camera with Global Navigation Satellite System (GNSS) signals for navigation purposes in urban environments. A sky-pointing camera is mounted on the top of a car and synchronized with a GNSS receiver. The advantages of this configuration are two-fold: firstly, for the GNSS signals, the upward-facing camera will be used to classify the acquired images into sky and non-sky (also known as segmentation). A satellite falling into the non-sky areas (e.g., buildings, trees) will be rejected and not considered for the final position solution computation. Secondly, the sky-pointing camera (with a field of view of about 90 degrees) is helpful for urban area ego-motion estimation in the sense that it does not see most of the moving objects (e.g., pedestrians, cars) and thus is able to estimate the ego-motion with fewer outliers than is typical with a forward-facing camera. The GNSS and visual information systems are tightly-coupled in a Kalman filter for the final position solution. Experimental results demonstrate the ability of the system to provide satisfactory navigation solutions and better accuracy than the GNSS-only and the loosely-coupled GNSS/vision, 20 percent and 82 percent (in the worst case) respectively, in a deep urban canyon, even in conditions with fewer than four GNSS satellites.

PEP-II design update and R ampersand D results

International Nuclear Information System (INIS)

Zisman, M.S.

1993-01-01

We describe the present status of the PEP-II asymmetric β factory design undertaken by SLAC, LBL, and LLNL. Design optimization during the past year and changes from the original CDR design are described. R ampersand D activities have focused primarily on the key technology areas of vacuum, RF, and feedback system design. Recent progress in these areas is described. The R ampersand D results have verified our design assumptions and provide further confidence in the design of PEP-II

Tsunami Amplitude Estimation from Real-Time GNSS.

Science.gov (United States)

Jeffries, C.; MacInnes, B. T.; Melbourne, T. I.

2017-12-01

Tsunami early warning systems currently comprise modeling of observations from the global seismic network, deep-ocean DART buoys, and a global distribution of tide gauges. While these tools work well for tsunamis traveling teleseismic distances, saturation of seismic magnitude estimation in the near field can result in significant underestimation of tsunami excitation for local warning. Moreover, DART buoy and tide gauge observations cannot be used to rectify the underestimation in the available time, typically 10-20 minutes, before local runup occurs. Real-time GNSS measurements of coseismic offsets may be used to estimate finite faulting within 1-2 minutes and, in turn, tsunami excitation for local warning purposes. We describe here a tsunami amplitude estimation algorithm; implemented for the Cascadia subduction zone, that uses continuous GNSS position streams to estimate finite faulting. The system is based on a time-domain convolution of fault slip that uses a pre-computed catalog of hydrodynamic Green's functions generated with the GeoClaw shallow-water wave simulation software and maps seismic slip along each section of the fault to points located off the Cascadia coast in 20m of water depth and relies on the principle of the linearity in tsunami wave propagation. The system draws continuous slip estimates from a message broker, convolves the slip with appropriate Green's functions which are then superimposed to produce wave amplitude at each coastal location. The maximum amplitude and its arrival time are then passed into a database for subsequent monitoring and display. We plan on testing this system using a suite of synthetic earthquakes calculated for Cascadia whose ground motions are simulated at 500 existing Cascadia GPS sites, as well as real earthquakes for which we have continuous GNSS time series and surveyed runup heights, including Maule, Chile 2010 and Tohoku, Japan 2011. This system has been implemented in the CWU Geodesy Lab for the Cascadia

A comparison of methods to estimate vertical land motion trends from GNSS and altimetry at tide gauge stations

Science.gov (United States)

Kleinherenbrink, Marcel; Riva, Riccardo; Frederikse, Thomas

2018-03-01

Tide gauge (TG) records are affected by vertical land motion (VLM), causing them to observe relative instead of geocentric sea level. VLM can be estimated from global navigation satellite system (GNSS) time series, but only a few TGs are equipped with a GNSS receiver. Hence, (multiple) neighboring GNSS stations can be used to estimate VLM at the TG. This study compares eight approaches to estimate VLM trends at 570 TG stations using GNSS by taking into account all GNSS trends with an uncertainty smaller than 1 mm yr-1 within 50 km. The range between the methods is comparable with the formal uncertainties of the GNSS trends. Taking the median of the surrounding GNSS trends shows the best agreement with differenced altimetry-tide gauge (ALT-TG) trends. An attempt is also made to improve VLM trends from ALT-TG time series. Only using highly correlated along-track altimetry and TG time series reduces the SD of ALT-TG time series by up to 10 %. As a result, there are spatially coherent changes in the trends, but the reduction in the root mean square (RMS) of differences between ALT-TG and GNSS trends is insignificant. However, setting correlation thresholds also acts like a filter to remove problematic TG time series. This results in sets of ALT-TG VLM trends at 344-663 TG locations, depending on the correlation threshold. Compared to other studies, we decrease the RMS of differences between GNSS and ALT-TG trends (from 1.47 to 1.22 mm yr-1), while we increase the number of locations (from 109 to 155), Depending on the methods the mean of differences between ALT-TG and GNSS trends vary between 0.1 and 0.2 mm yr-1. We reduce the mean of the differences by taking into account the effect of elastic deformation due to present-day mass redistribution. At varying ALT-TG correlation thresholds, we provide new sets of trends for 759 to 939 different TG stations. If both GNSS and ALT-TG trend estimates are available, we recommend using the GNSS trend estimates because residual

LATENCY DETERMINATION AND COMPENSATION IN REAL-TIME GNSS/INS INTEGRATED NAVIGATION SYSTEMS

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P. D. Solomon

2012-09-01

Full Text Available Unmanned Aerial Vehicle (UAV technology is now commonplace in many defence and civilian environments. However, the high cost of owning and operating a sophisticated UAV has slowed their adoption in many commercial markets. Universities and research groups are actively experimenting with UAVs to further develop the technology, particularly for automated flying operations. The two main UAV platforms used are fixed-wing and helicopter. Helicopter-based UAVs offer many attractive features over fixed-wing UAVs, including vertical take-off, the ability to loiter, and highly dynamic flight. However the control and navigation of helicopters are significantly more demanding than those of fixed-wing UAVs and as such require a high bandwidth real-time Position, Velocity, Attitude (PVA navigation system. In practical Real-Time Navigation Systems (RTNS there are delays in the processing of the GNSS data prior to the fusion of the GNSS data with the INS measurements. This latency must be compensated for otherwise it degrades the solution of the navigation filter. This paper investigates the effect of latency in the arrival time of the GNSS data in a RTNS. Several test drives and flights were conducted with a low-cost RTNS, and compared with a high quality GNSS/INS solution. A technique for the real-time, automated and accurate estimation of the GNSS latency in low-cost systems was developed and tested. The latency estimates were then verified through cross-correlation with the time-stamped measurements from the reference system. A delayed measurement Extended Kalman Filter was then used to allow for the real-time fusing of the delayed measurements, and then a final system developed for on-the-fly measurement and compensation of GNSS latency in a RTNS.

Latency Determination and Compensation in Real-Time Gnss/ins Integrated Navigation Systems

Science.gov (United States)

Solomon, P. D.; Wang, J.; Rizos, C.

2011-09-01

Unmanned Aerial Vehicle (UAV) technology is now commonplace in many defence and civilian environments. However, the high cost of owning and operating a sophisticated UAV has slowed their adoption in many commercial markets. Universities and research groups are actively experimenting with UAVs to further develop the technology, particularly for automated flying operations. The two main UAV platforms used are fixed-wing and helicopter. Helicopter-based UAVs offer many attractive features over fixed-wing UAVs, including vertical take-off, the ability to loiter, and highly dynamic flight. However the control and navigation of helicopters are significantly more demanding than those of fixed-wing UAVs and as such require a high bandwidth real-time Position, Velocity, Attitude (PVA) navigation system. In practical Real-Time Navigation Systems (RTNS) there are delays in the processing of the GNSS data prior to the fusion of the GNSS data with the INS measurements. This latency must be compensated for otherwise it degrades the solution of the navigation filter. This paper investigates the effect of latency in the arrival time of the GNSS data in a RTNS. Several test drives and flights were conducted with a low-cost RTNS, and compared with a high quality GNSS/INS solution. A technique for the real-time, automated and accurate estimation of the GNSS latency in low-cost systems was developed and tested. The latency estimates were then verified through cross-correlation with the time-stamped measurements from the reference system. A delayed measurement Extended Kalman Filter was then used to allow for the real-time fusing of the delayed measurements, and then a final system developed for on-the-fly measurement and compensation of GNSS latency in a RTNS.

Debris flow cartography using differential GNSS and Theodolite measurements

Science.gov (United States)

Khazaradze, Giorgi; Guinau, Marta; Calvet, Jaume; Furdada, Gloria; Victoriano, Ane; Génova, Mar; Suriñach, Emma

2016-04-01

, limits the visibility of the satellites and thus, can result in meter-level errors while estimating the positions. We have conducted 2 measurements using various differential GNSS systems in March and in September of 2015. During these measurements we used Leica Viva GS14 receiver as a rover station, which was equipped with a GSM card to establish an internet connection in order to receive differential corrections from continuous GNSS networks. During the first campaign we have used the RTK positioning method using the SmartNet network (http://es.smartnet-eu.com) operated by Leica. This system had the advantage of transmitting differential corrections for GPS and GLONASS systems. During the second campaign, we have had an access to the ICGC (http://www.icc.cat) CatNet permanent GPS network, which only provides GPS satellite corrections. Here we present the analysis of the obtained precisions from these two RTK systems. Additionally, we have analyzed the geodetic data in a post-processing mode using the Leica Geo Office 8.4 software with IGS estimated final orbits. For this procedure, in addition to using the data from nearby CatNet CGPS stations, we have also used data from the base station(s) specifically setup near the study area during the campaign period. The work has been supported by the Spanish Ministry of Science and Innovation project CHARMA: CHAracterization and ContRol of MAss Movements. A Challenge for Geohazard Mitigation (CGL2013-40828-R) and RISKNAT group (2014GR/1243).

EFFECTS OF OCEAN TIDE MODELS ON GNSS-ESTIMATED ZTD AND PWV IN TURKEY

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G. Gurbuz

2015-12-01

Full Text Available Global Navigation Satellite System (GNSS observations can precisely estimate the total zenith tropospheric delay (ZTD and precipitable water vapour (PWV for weather prediction and atmospheric research as a continuous and all-weather technique. However, apart from GNSS technique itself, estimations of ZTD and PWV are subject to effects of geophysical models with large uncertainties, particularly imprecise ocean tide models in Turkey. In this paper, GNSS data from Jan. 1st to Dec. 31st of 2014 are processed at 4 co-located GNSS stations (GISM, DIYB, GANM, and ADAN with radiosonde from Turkish Met-Office along with several nearby IGS stations. The GAMIT/GLOBK software has been used to process GNSS data of 30-second sample using the Vienna Mapping Function and 10° elevation cut-off angle. Also tidal and non-tidal atmospheric pressure loadings (ATML at the observation level are also applied in GAMIT/GLOBK. Several widely used ocean tide models are used to evaluate their effects on GNSS-estimated ZTD and PWV estimation, such as IERS recommended FES2004, NAO99b from a barotropic hydrodynamic model, CSR4.0 obtained from TOPEX/Poseidon altimetry with the model FES94.1 as the reference model and GOT00 which is again long wavelength adjustments of FES94.1 using TOPEX/Poseidon data at 0.5 by 0.5 degree grid. The ZTD and PWV computed from radiosonde profile observations are regarded as reference values for the comparison and validation. In the processing phase, five different strategies are taken without ocean tide model and with four aforementioned ocean tide models, respectively, which are used to evaluate ocean tide models effects on GNSS-estimated ZTD and PWV estimation through comparing with co-located Radiosonde. Results showed that ocean tide models have greatly affected the estimation of the ZTD in centimeter level and thus the precipitable water vapour in millimeter level, respectively at stations near coasts. The ocean tide model FES2004 that is

Ionospheric Modeling for Precise GNSS Applications

NARCIS (Netherlands)

Memarzadeh, Y.

2009-01-01

The main objective of this thesis is to develop a procedure for modeling and predicting ionospheric Total Electron Content (TEC) for high precision differential GNSS applications. As the ionosphere is a highly dynamic medium, we believe that to have a reliable procedure it is necessary to transfer

Rapid kinematic finite source inversion for Tsunamic Early Warning using high rate GNSS data

Science.gov (United States)

Chen, K.; Liu, Z.; Song, Y. T.

2017-12-01

Recently, Global Navigation Satellite System (GNSS) has been used for rapid earthquake source inversion towards tsunami early warning. In practice, two approaches, i.e., static finite source inversion based on permanent co-seismic offsets and kinematic finite source inversion using high-rate (>= 1 Hz) co-seismic displacement waveforms, are often employed to fulfill the task. The static inversion is relatively easy to be implemented and does not require additional constraints on rupture velocity, duration, and temporal variation. However, since most GNSS receivers are deployed onshore locating on one side of the subduction fault, there is very limited resolution on near-trench fault slip using GNSS in static finite source inversion. On the other hand, the high-rate GNSS displacement waveforms, which contain the timing information of earthquake rupture explicitly and static offsets implicitly, have the potential to improve near-trench resolution by reconciling with the depth-dependent megathrust rupture behaviors. In this contribution, we assess the performance of rapid kinematic finite source inversion using high-rate GNSS by three selected historical tsunamigenic cases: the 2010 Mentawai, 2011 Tohoku and 2015 Illapel events. With respect to the 2010 Mentawai case, it is a typical tsunami earthquake with most slip concentrating near the trench. The static inversion has little resolution there and incorrectly puts slip at greater depth (>10km). In contrast, the recorded GNSS displacement waveforms are deficit in high-frequency energy, the kinematic source inversion recovers a shallow slip patch (depth less than 6 km) and tsunami runups are predicted quite reasonably. For the other two events, slip from kinematic and static inversion show similar characteristics and comparable tsunami scenarios, which may be related to dense GNSS network and behavior of the rupture. Acknowledging the complexity of kinematic source inversion in real-time, we adopt the back

GNSS Derived Ionospheric TEC Observed Through Different TEC Calibration Techniques in the Brazilian Sector

Science.gov (United States)

Becker-Guedes, F.; Carmo, C. S.; Camargo, P. O.; Monico, J. F. G.; Nicoli Candido, C. M.

2017-12-01

Global Navigation Satellite System (GNSS) is becoming a reliable tool for use in air navigation systems. Its use as the main technology for determination of airplanes positioning has various economic and logistic benefits but it depends strongly on the ionospheric layer influences. The Brazilian sector ionosphere, mainly over the equatorial ionization anomaly (EIA), presents remarkable errors in the GNSS signal as compared to North America and Europe. In order to study the total electron content latitudinal variation of the Brazilian ionosphere we used a pair of GNSS receivers on the ground, one located in the equatorial region (Sao Luis) and other in the southern crest of the EIA (Cachoeira Paulista), to collect the GNSS observables and calculate the vertical TEC using different methods that has proven to work well to describe the ionospheric behavior in the North America and in Europe. We compared this results with a modified Nagoya TEC calculation method used by the EMBRACE (Estudo e Monitoramento BRAsileiro do Clima Espacial - Brazilian Study and Monitoring of Space Weather) program. This work intends to follow the performance of different TEC tuning methods to evaluate the spurious effects of the ionospheric EIA gradients in the TEC determination under typical conditions of the low-latitudes ionosphere in the Brazilian sector. The calculated TEC under different solar cycle conditions, geomagnetic activity, and seasonal variations show deviations in the performance of each method and stress the importance of well adjust the GNSS observations to local conditions in order to optimize the TEC evaluation. This study contributes to a better understanding of local GNSS signal errors in the global intent of offering conditions to improve the accuracy, integrity, availability, and continuity requirements for the use of GNSS for air navigation in South America.

Flicker Noise in GNSS Station Position Time Series: How much is due to Crustal Loading Deformations?

Science.gov (United States)

Rebischung, P.; Chanard, K.; Metivier, L.; Altamimi, Z.

2017-12-01

The presence of colored noise in GNSS station position time series was detected 20 years ago. It has been shown since then that the background spectrum of non-linear GNSS station position residuals closely follows a power-law process (known as flicker noise, 1/f noise or pink noise), with some white noise taking over at the highest frequencies. However, the origin of the flicker noise present in GNSS station position time series is still unclear. Flicker noise is often described as intrinsic to the GNSS system, i.e. due to errors in the GNSS observations or in their modeling, but no such error source has been identified so far that could explain the level of observed flicker noise, nor its spatial correlation.We investigate another possible contributor to the observed flicker noise, namely real crustal displacements driven by surface mass transports, i.e. non-tidal loading deformations. This study is motivated by the presence of power-law noise in the time series of low-degree (≤ 40) and low-order (≤ 12) Stokes coefficients observed by GRACE - power-law noise might also exist at higher degrees and orders, but obscured by GRACE observational noise. By comparing GNSS station position time series with loading deformation time series derived from GRACE gravity fields, both with their periodic components removed, we therefore assess whether GNSS and GRACE both plausibly observe the same flicker behavior of surface mass transports / loading deformations. Taking into account GRACE observability limitations, we also quantify the amount of flicker noise in GNSS station position time series that could be explained by such flicker loading deformations.

Outlier Detection in GNSS Pseudo-Range/Doppler Measurements for Robust Localization

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Salim Zair

2016-04-01

Full Text Available In urban areas or space-constrained environments with obstacles, vehicle localization using Global Navigation Satellite System (GNSS data is hindered by Non-Line Of Sight (NLOS and multipath receptions. These phenomena induce faulty data that disrupt the precise localization of the GNSS receiver. In this study, we detect the outliers among the observations, Pseudo-Range (PR and/or Doppler measurements, and we evaluate how discarding them improves the localization. We specify a contrario modeling for GNSS raw data to derive an algorithm that partitions the dataset between inliers and outliers. Then, only the inlier data are considered in the localization process performed either through a classical Particle Filter (PF or a Rao-Blackwellization (RB approach. Both localization algorithms exclusively use GNSS data, but they differ by the way Doppler measurements are processed. An experiment has been performed with a GPS receiver aboard a vehicle. Results show that the proposed algorithms are able to detect the ‘outliers’ in the raw data while being robust to non-Gaussian noise and to intermittent satellite blockage. We compare the performance results achieved either estimating only PR outliers or estimating both PR and Doppler outliers. The best localization is achieved using the RB approach coupled with PR-Doppler outlier estimation.

Accuracy improvement techniques in Precise Point Positioning method using multiple GNSS constellations

Science.gov (United States)

Vasileios Psychas, Dimitrios; Delikaraoglou, Demitris

2016-04-01

The future Global Navigation Satellite Systems (GNSS), including modernized GPS, GLONASS, Galileo and BeiDou, offer three or more signal carriers for civilian use and much more redundant observables. The additional frequencies can significantly improve the capabilities of the traditional geodetic techniques based on GPS signals at two frequencies, especially with regard to the availability, accuracy, interoperability and integrity of high-precision GNSS applications. Furthermore, highly redundant measurements can allow for robust simultaneous estimation of static or mobile user states including more parameters such as real-time tropospheric biases and more reliable ambiguity resolution estimates. This paper presents an investigation and analysis of accuracy improvement techniques in the Precise Point Positioning (PPP) method using signals from the fully operational (GPS and GLONASS), as well as the emerging (Galileo and BeiDou) GNSS systems. The main aim was to determine the improvement in both the positioning accuracy achieved and the time convergence it takes to achieve geodetic-level (10 cm or less) accuracy. To this end, freely available observation data from the recent Multi-GNSS Experiment (MGEX) of the International GNSS Service, as well as the open source program RTKLIB were used. Following a brief background of the PPP technique and the scope of MGEX, the paper outlines the various observational scenarios that were used in order to test various data processing aspects of PPP solutions with multi-frequency, multi-constellation GNSS systems. Results from the processing of multi-GNSS observation data from selected permanent MGEX stations are presented and useful conclusions and recommendations for further research are drawn. As shown, data fusion from GPS, GLONASS, Galileo and BeiDou systems is becoming increasingly significant nowadays resulting in a position accuracy increase (mostly in the less favorable East direction) and a large reduction of convergence

The GNSS-based component for the new Indonesian tsunami early warning centre provided by GITEWS

Science.gov (United States)

Falck, C.; Ramatschi, M.; Bartsch, M.; Merx, A.; Hoeberechts, J.; Rothacher, M.

2009-04-01

Introduction Nowadays GNSS technologies are used for a large variety of precise positioning applications. The accuracy can reach the mm level depending on the data analysis methods. GNSS technologies thus offer a high potential to support tsunami early warning systems, e.g., by detection of ground motions due to earthquakes and of tsunami waves on the ocean by GNSS instruments on a buoy. Although GNSS-based precise positioning is a standard method, it is not yet common to apply this technique under tight time constraints and, hence, in the absence of precise satellite orbits and clocks. The new developed GNSS-based component utilises on- and offshore measured GNSS data and is the first system of its kind that was integrated into an operational early warning system. (Indonesian Tsunami Early Warning Centre INATEWS, inaugurated at BMKG, Jakarta on November, 11th 2008) Motivation After the Tsunami event of 26th December 2004 the German government initiated the GITEWS project (German Indonesian Tsunami Early Warning System) to develop a tsunami early warning system for Indonesia. The GFZ Potsdam (German Research Centre for Geosciences) as the consortial leader of GITEWS also covers several work packages, most of them related to sensor systems. The geodetic branch (Department 1) of the GFZ was assigned to develop a GNSS-based component. Brief system description The system covers all aspects from sensor stations with new developed hard- and software designs, manufacturing and installation of stations, real-time data transfer issues, a new developed automatic near real-time data processing and a graphical user interface for early warning centre operators including training on the system. GNSS sensors are installed on buoys, at tide gauges and as real-time reference stations (RTR stations), either stand-alone or co-located with seismic sensors. The GNSS data are transmitted to the warning centre where they are processed in a near real-time data processing chain. For

Precise Point Positioning Using Triple GNSS Constellations in Various Modes

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Akram Afifi

2016-05-01

Full Text Available This paper introduces a new dual-frequency precise point positioning (PPP model, which combines the observations from three different global navigation satellite system (GNSS constellations, namely GPS, Galileo, and BeiDou. Combining measurements from different GNSS systems introduces additional biases, including inter-system bias and hardware delays, which require rigorous modelling. Our model is based on the un-differenced and between-satellite single-difference (BSSD linear combinations. BSSD linear combination cancels out some receiver-related biases, including receiver clock error and non-zero initial phase bias of the receiver oscillator. Forming the BSSD linear combination requires a reference satellite, which can be selected from any of the GPS, Galileo, and BeiDou systems. In this paper three BSSD scenarios are tested; each considers a reference satellite from a different GNSS constellation. Natural Resources Canada’s GPSPace PPP software is modified to enable a combined GPS, Galileo, and BeiDou PPP solution and to handle the newly introduced biases. A total of four data sets collected at four different IGS stations are processed to verify the developed PPP model. Precise satellite orbit and clock products from the International GNSS Service Multi-GNSS Experiment (IGS-MGEX network are used to correct the GPS, Galileo, and BeiDou measurements in the post-processing PPP mode. A real-time PPP solution is also obtained, which is referred to as RT-PPP in the sequel, through the use of the IGS real-time service (RTS for satellite orbit and clock corrections. However, only GPS and Galileo observations are used for the RT-PPP solution, as the RTS-IGS satellite products are not presently available for BeiDou system. All post-processed and real-time PPP solutions are compared with the traditional un-differenced GPS-only counterparts. It is shown that combining the GPS, Galileo, and BeiDou observations in the post-processing mode improves the

Kilometer-Spaced GNSS Array for Ionospheric Irregularity Monitoring

Science.gov (United States)

Su, Yang

This dissertation presents automated, systematic data collection, processing, and analysis methods for studying the spatial-temporal properties of Global Navigation Satellite Systems (GNSS) scintillations produced by ionospheric irregularities at high latitudes using a closely spaced multi-receiver array deployed in the northern auroral zone. The main contributions include 1) automated scintillation monitoring, 2) estimation of drift and anisotropy of the irregularities, 3) error analysis of the drift estimates, and 4) multi-instrument study of the ionosphere. A radio wave propagating through the ionosphere, consisting of ionized plasma, may suffer from rapid signal amplitude and/or phase fluctuations known as scintillation. Caused by non-uniform structures in the ionosphere, intense scintillation can lead to GNSS navigation and high-frequency (HF) communication failures. With specialized GNSS receivers, scintillation can be studied to better understand the structure and dynamics of the ionospheric irregularities, which can be parameterized by altitude, drift motion, anisotropy of the shape, horizontal spatial extent and their time evolution. To study the structuring and motion of ionospheric irregularities at the sub-kilometer scale sizes that produce L-band scintillations, a closely-spaced GNSS array has been established in the auroral zone at Poker Flat Research Range, Alaska to investigate high latitude scintillation and irregularities. Routinely collecting low-rate scintillation statistics, the array database also provides 100 Hz power and phase data for each channel at L1/L2C frequency. In this work, a survey of seasonal and hourly dependence of L1 scintillation events over the course of a year is discussed. To efficiently and systematically study scintillation events, an automated low-rate scintillation detection routine is established and performed for each day by screening the phase scintillation index. The spaced-receiver technique is applied to cross

GNSS remote sensing theory, methods and applications

CERN Document Server

Jin, Shuanggen; Xie, Feiqin

2014-01-01

This book presents the theory and methods of GNSS remote sensing as well as its applications in the atmosphere, oceans, land and hydrology. It contains detailed theory and study cases to help the reader put the material into practice.

Hazard Monitoring in a Spectrum-Challenged Future: US Department of Transportation Adjacent Band Compatibility Assessment of Interference on High-Precision GNSS Receivers

Science.gov (United States)

Blume, F.; Berglund, H. T.

2016-12-01

In 2012 the Federal Communications Commission (FCC) reversed its decision to allow communications company LightSquared to use GPS-adjacent spectrum for a ground based network after testing demonstrated harmful interference to GPS receivers. Now rebranded as Ligado, they have submitted modified application to use a smaller portion of the L-band spectrum at much lower power. Many GPS community stakeholders, including the hazard monitoring and EEW communities remain concerned that Ligado's proposed use could still cause harmful interference, causing signal degradation, real-time positioning errors, and total failure of GNSS hardware in widespread use in hazard monitoring networks. The Department of Transportation (DoT) has conducted hardware tests to determine adjacent-band transmitter power limit criteria that would prevent harmful interference from Ligado's operations. We present preliminary results produced from the data collected by the three UNAVCO receiver types tested: Trimble NetRS, Trimble NetR9, and Septentrio PolaRx5. In the first round of testing, simulated GNSS signals were broadcast in an anechoic chamber (pictured below) while interfering signals are broadcast simultaneously with varying amplitude and frequency. The older GPS-only NetRS receiver showed smaller reductions in SNR at frequencies adjacent to GPS L1 as compared to the other receivers, suggesting narrower L1 filter bandwidth in the RF frontend. The NetR9 showed greater decreases in observed SNR in the 1615 to 1625 MHz range when compared to the other two receivers. This suggests that the NetR9's L1 filter bandwidth has been increased to accommodate GNSS signals. Linearity tests were conducted to better relate SNR measurements between receiver types. The PolaRx5 receiver showed less SNR variation between tracking channels than both Trimble receivers. Our results show the power levels at which adjacent-band interference begins degrading receiver performance and eventually disables tracking. As

Impact and Implementation of Higher-Order Ionospheric Effects on Precise GNSS Applications

Science.gov (United States)

Hadas, T.; Krypiak-Gregorczyk, A.; Hernández-Pajares, M.; Kaplon, J.; Paziewski, J.; Wielgosz, P.; Garcia-Rigo, A.; Kazmierski, K.; Sosnica, K.; Kwasniak, D.; Sierny, J.; Bosy, J.; Pucilowski, M.; Szyszko, R.; Portasiak, K.; Olivares-Pulido, G.; Gulyaeva, T.; Orus-Perez, R.

2017-11-01

High precision Global Navigation Satellite Systems (GNSS) positioning and time transfer require correcting signal delays, in particular higher-order ionospheric (I2+) terms. We present a consolidated model to correct second- and third-order terms, geometric bending and differential STEC bending effects in GNSS data. The model has been implemented in an online service correcting observations from submitted RINEX files for I2+ effects. We performed GNSS data processing with and without including I2+ corrections, in order to investigate the impact of I2+ corrections on GNSS products. We selected three time periods representing different ionospheric conditions. We used GPS and GLONASS observations from a global network and two regional networks in Poland and Brazil. We estimated satellite orbits, satellite clock corrections, Earth rotation parameters, troposphere delays, horizontal gradients, and receiver positions using global GNSS solution, Real-Time Kinematic (RTK), and Precise Point Positioning (PPP) techniques. The satellite-related products captured most of the impact of I2+ corrections, with the magnitude up to 2 cm for clock corrections, 1 cm for the along- and cross-track orbit components, and below 5 mm for the radial component. The impact of I2+ on troposphere products turned out to be insignificant in general. I2+ corrections had limited influence on the performance of ambiguity resolution and the reliability of RTK positioning. Finally, we found that I2+ corrections caused a systematic shift in the coordinate domain that was time- and region-dependent and reached up to -11 mm for the north component of the Brazilian stations during the most active ionospheric conditions.

Understanding Transient Forcing with Plasma Instability Model, Ionospheric Propagation Model and GNSS Observations

Science.gov (United States)

Deshpande, K.; Zettergren, M. D.; Datta-Barua, S.

2017-12-01

Fluctuations in the Global Navigation Satellite Systems (GNSS) signals observed as amplitude and phase scintillations are produced by plasma density structures in the ionosphere. Phase scintillation events in particular occur due to structures at Fresnel scales, typically about 250 meters at ionospheric heights and GNSS frequency. Likely processes contributing to small-scale density structuring in auroral and polar regions include ionospheric gradient-drift instability (GDI) and Kelvin-Helmholtz instability (KHI), which result, generally, from magnetosphere-ionosphere interactions (e.g. reconnection) associated with cusp and auroral zone regions. Scintillation signals, ostensibly from either GDI or KHI, are frequently observed in the high latitude ionosphere and are potentially useful diagnostics of how energy from the transient forcing in the cusp or polar cap region cascades, via instabilities, to small scales. However, extracting quantitative details of instabilities leading to scintillation using GNSS data drastically benefits from both a model of the irregularities and a model of GNSS signal propagation through irregular media. This work uses a physics-based model of the generation of plasma density irregularities (GEMINI - Geospace Environment Model of Ion-Neutral Interactions) coupled to an ionospheric radio wave propagation model (SIGMA - Satellite-beacon Ionospheric-scintillation Global Model of the upper Atmosphere) to explore the cascade of density structures from medium to small (sub-kilometer) scales. Specifically, GEMINI-SIGMA is used to simulate expected scintillation from different instabilities during various stages of evolution to determine features of the scintillation that may be useful to studying ionospheric density structures. Furthermore we relate the instabilities producing GNSS scintillations to the transient space and time-dependent magnetospheric phenomena and further predict characteristics of scintillation in different geophysical

Trusted Data Communication and Security Issues in Gnss Network of Turkey

Science.gov (United States)

Bakici, S.; Erkek, B.; Manti, V.; Altekin, A.

2017-11-01

There are three main activities of General Directorate of Land Registry and Cadastre. These are Mapping, Land Registry and Cadastre. Geomatic Department is responsible for mapping activities. The most important projects like TUSAGA-Aktif (CORS-Tr), Metadata Geoportal, Orthophoto Production and orthophoto web services and preparation of Turkish NSDI Feasibility Report have been conducted and completed by this department's specialists since 2005. TUSAGA-Aktif (CORS-Tr) System, serves location information at cm level accuracy in Turkey and TR Nortern Cyprus in few seconds, where adequate numbers of GNSS satellites are observed and communication possibilities are present. No ground control points and benchmarks are necessary. There are 146 permanent GNSS stations within the CORS-Tr System. Station data are transferred online to the main control center located in the Mapping Department of the General Directorate of Land Registry and Cadastre and to the control center located in the General Command of Mapping. Currently CORS-Tr has more than 9000 users. Most of them are private companies working for governmental organization. Providing data communication between control center and both GNSS station and users via trusted and good substructure is important. Additionally, protection of the system and data against cyber attacks from domestic and foreign sources is important. This paper focuses on data communication and security issues of GNSS network named TUSAGA-Aktif.

TRUSTED DATA COMMUNICATION AND SECURITY ISSUES IN GNSS NETWORK OF TURKEY

Directory of Open Access Journals (Sweden)

S. Bakici

2017-11-01

Full Text Available There are three main activities of General Directorate of Land Registry and Cadastre. These are Mapping, Land Registry and Cadastre. Geomatic Department is responsible for mapping activities. The most important projects like TUSAGA-Aktif (CORS-Tr, Metadata Geoportal, Orthophoto Production and orthophoto web services and preparation of Turkish NSDI Feasibility Report have been conducted and completed by this department’s specialists since 2005. TUSAGA-Aktif (CORS-Tr System, serves location information at cm level accuracy in Turkey and TR Nortern Cyprus in few seconds, where adequate numbers of GNSS satellites are observed and communication possibilities are present. No ground control points and benchmarks are necessary. There are 146 permanent GNSS stations within the CORS-Tr System. Station data are transferred online to the main control center located in the Mapping Department of the General Directorate of Land Registry and Cadastre and to the control center located in the General Command of Mapping. Currently CORS-Tr has more than 9000 users. Most of them are private companies working for governmental organization. Providing data communication between control center and both GNSS station and users via trusted and good substructure is important. Additionally, protection of the system and data against cyber attacks from domestic and foreign sources is important. This paper focuses on data communication and security issues of GNSS network named TUSAGA-Aktif.

First results of the Nordic and Baltic GNSS Analysis Centre

Science.gov (United States)

Lahtinen, Sonja; Pasi, Häkli; Jivall, Lotti; Kempe, Christina; Kollo, Karin; Kosenko, Ksenija; Pihlak, Priit; Prizginiene, Dalia; Tangen, Oddvar; Weber, Mette; Paršeliūnas, Eimuntas; Baniulis, Rimvydas; Galinauskas, Karolis

2018-03-01

The Nordic Geodetic Commission (NKG) has launched a joint NKG GNSS Analysis Centre that aims to routinely produce high qualityGNSS solutions for the common needs of the NKG and the Nordic and Baltic countries. A consistent and densified velocity field is needed for the constraining of the gla-cial isostatic adjustment (GIA) modelling that is a key component of maintaining the national reference frame realisations in the area. We described the methods of the NKG GNSS Analysis Centre including the defined processing setup for the local analysis centres (LAC) and for the combination centres.We analysed the results of the first 2.5 years (2014.5-2016). The results showed that different subnets were consistent with the combined solution within 1-2 mm level. We observed the so called network effect affecting our reference frame alignment. However, the accuracy of the reference frame alignment was on a few millimetre level in the area of the main interest (Nordic and Baltic Countries). TheNKGGNSS AC was declared fully operational in April 2017.

On Chinese National Continuous Operating Reference Station System of GNSS

Directory of Open Access Journals (Sweden)

CHEN Junyong

2007-11-01

Full Text Available Objective: Global navigation satellite system (GNSS Continuous Operating Reference Station (CORS System can maintain a accurate, 3D, geocentric and dynamic reference coordinate frame in the corresponding area, can provide positioning and navigation service. It can also serve for the meteorology, geodynamics, earthquake monitoring and Location Based services (LBS etc in the same area. Until now, our country can’t provide a facing National CORS System serving for every profession and trade, and the national sharing platform of CORS System resources has not been established. So this paper discusses some valuable insight how to construct the National CORS System in China. Method: Constructing goal、Service object、CORS distribution、CORS geographic、geology and communication environment and other factors, are major considerations for the Constructing the National CORS System. Moreover, constructing GNSS CORS is more specific, mainly from four aspects, namely site-selection、civil construction、security measures and equipment-selection for consideration. Outcome: The project of the Constructing Global navigation satellite system (GNSS Continuous Operating Reference Station (CORS System in china is put forward, and is discussed from goal、principle、project and other for construction. Some meaning thought how to construct the National CORS System is submitted Conclusion: The Global navigation satellite system (GNSS Continuous Operating Reference Station (CORS System in china is the lack of a unified planning and design in the national level. So far, the national CORS system serving all walks of life has not been provided, and the national sharing platform of CORS System resources has not been established The primary mission of the Global navigation satellite system (GNSS Continuous Operating Reference Station (CORS System in china is as follows: using data set of GNSS and receiving, transport, process, integration, transmit information and

Status and Perspective of the IGS Multi-GNSS Experiment (MGEX)

Science.gov (United States)

Steigenberger, Peter; Montenbruck, Oliver; Weber, Robert; Hugentobler, Urs

2013-04-01

Following three decades, during which the Global Positioning System GPS has evolved from a military navigation system into an indispensable tool for geodetic research and global monitoring of the Earth, the world of satellite navigation has experienced dramatic changes over the past years. With GLONASS, a second global navigation system has achieved a fully operational status, GPS is introducing modernized civil and encrypted navigation signals, and a variety of new navigation constellations are being built-up in Asia and Europe. These include BeiDou, which has recently opened a regional navigation service in the Asia-Pacific region, Galileo, which now has four satellites in orbit, as well as QZSS, which offers a unique set of signals and service features. In recognition of a rapidly changing GNSS landscape, the International GNSS Service (IGS) has initiated the Multi-GNSS Experiment (MGEX - http://igs.org/mgex) as a platform for early familiarization with emerging navigation systems and to pave the way for a full-featured use thereof in a future multi-GNSS service. As a first step, MGEX has promoted the build-up of a new global network of GNSS monitoring stations, each tracking at least one new constellation (Galileo, BeiDou, or QZSS) on top of GPS, GLONASS and SBAS. By the end of 2012, approximately 50 stations contribute offline and/or real-time data to the MGEX network. To facilitate introduction of new standards (specifically RINEX3 observation and navigation data formats), distinct data archives are used even for those MGEX stations jointly contributing to the legacy IGS. Building-up on the new multi-GNSS network, the generation of associated orbit and clock products has started in the second quarter of 2012. At this stage, only Galileo and QZSS products are offered by selected MGEX Analysis Centers, but the addition of BeiDou is expected in 2013 as the MGEX network expands and new Analysis Centers join the data processing effort. Despite remarkable progress

High Precision Positioning at Field Camp: Using GNSS as the primary data source to answer geologic questions

Science.gov (United States)

Crosby, B. T.; Lauer, I. H.; Pratt-Sitaula, B.

2017-12-01

Thanks to the availability and accessibility of GPS/GNSS enabled consumer grade positioning devices, GNSS are nearly ubiquitous in both geologic field research and education. Though the devices offer sufficient precision to geotag images, digital field book entries or measurements, positions themselves are not precise enough to accomplish independent geodetic analysis. As a consequence, most students learn about GNSS at a tool that aids other forms of geologic data acquisition rather serving as the primary source itself. To resolve this, we developed and tested a three-unit teaching module within the GETSI - SERC curriculum framework that reinforces high precision positioning as a primary source of geologic data. Units focus on three core topics: GNSS Fundamentals, Kinematic GNSS and Static GNSS Methods. Module goals enable students to (a) design and conduct a GNSS survey to answer a geologic question, (b) justify why their GNSS technique is appropriate to their question and (c) to articulate how answering their question benefits society. Skill building is via quantitative and qualitative analysis, concept sketches, and both field and office based data acquisition and interrogation. Exercises are site-independent and include example datasets for those unable to travel. In the summer of 2017, we tested the module with 20 undergraduate students over two days at the ISU field geology course. Located in the Lost River Range of Idaho, positioned among active normal faults, we not only explored the use of static GNSS data for active tectonics but visited a station in person. For a summative assessment, we focused on kinematic GNSS, using RTK rovers to reoccupy leveling monuments spanning the active Lost River fault that ruptured in 1983 (M 7.0). The data collected by our class quantified aseismic deformation occurring in the 30+ years since that event. Displacements were significantly larger than the instrumental uncertainty, confirming that RTK was an appropriate tool

An Integrated GNSS/INS/LiDAR-SLAM Positioning Method for Highly Accurate Forest Stem Mapping

Directory of Open Access Journals (Sweden)

Chuang Qian

2016-12-01

Full Text Available Forest mapping, one of the main components of performing a forest inventory, is an important driving force in the development of laser scanning. Mobile laser scanning (MLS, in which laser scanners are installed on moving platforms, has been studied as a convenient measurement method for forest mapping in the past several years. Positioning and attitude accuracies are important for forest mapping using MLS systems. Inertial Navigation Systems (INSs and Global Navigation Satellite Systems (GNSSs are typical and popular positioning and attitude sensors used in MLS systems. In forest environments, because of the loss of signal due to occlusion and severe multipath effects, the positioning accuracy of GNSS is severely degraded, and even that of GNSS/INS decreases considerably. Light Detection and Ranging (LiDAR-based Simultaneous Localization and Mapping (SLAM can achieve higher positioning accuracy in environments containing many features and is commonly implemented in GNSS-denied indoor environments. Forests are different from an indoor environment in that the GNSS signal is available to some extent in a forest. Although the positioning accuracy of GNSS/INS is reduced, estimates of heading angle and velocity can maintain high accurate even with fewer satellites. GNSS/INS and the LiDAR-based SLAM technique can be effectively integrated to form a sustainable, highly accurate positioning and mapping solution for use in forests without additional hardware costs. In this study, information such as heading angles and velocities extracted from a GNSS/INS is utilized to improve the positioning accuracy of the SLAM solution, and two information-aided SLAM methods are proposed. First, a heading angle-aided SLAM (H-aided SLAM method is proposed that supplies the heading angle from GNSS/INS to SLAM. Field test results show that the horizontal positioning accuracy of an entire trajectory of 800 m is 0.13 m and is significantly improved (by 70% compared to that

GNSS reflectometry aboard the International Space Station: phase-altimetry simulation to detect ocean topography anomalies

Science.gov (United States)

Semmling, Maximilian; Leister, Vera; Saynisch, Jan; Zus, Florian; Wickert, Jens

2016-04-01

An ocean altimetry experiment using Earth reflected GNSS signals has been proposed to the European Space Agency (ESA). It is part of the GNSS Reflectometry Radio Occultation Scatterometry (GEROS) mission that is planned aboard the International Space Station (ISS). Altimetric simulations are presented that examine the detection of ocean topography anomalies assuming GNSS phase delay observations. Such delay measurements are well established for positioning and are possible due to a sufficient synchronization of GNSS receiver and transmitter. For altimetric purpose delays of Earth reflected GNSS signals can be observed similar to radar altimeter signals. The advantage of GNSS is the synchronized separation of transmitter and receiver that allow a significantly increased number of observation per receiver due to more than 70 GNSS transmitters currently in orbit. The altimetric concept has already been applied successfully to flight data recorded over the Mediterranean Sea. The presented altimetric simulation considers anomalies in the Agulhas current region which are obtained from the Region Ocean Model System (ROMS). Suitable reflection events in an elevation range between 3° and 30° last about 10min with ground track's length >3000km. Typical along-track footprints (1s signal integration time) have a length of about 5km. The reflection's Fresnel zone limits the footprint of coherent observations to a major axis extention between 1 to 6km dependent on the elevation. The altimetric performance depends on the signal-to-noise ratio (SNR) of the reflection. Simulation results show that precision is better than 10cm for SNR of 30dB. Whereas, it is worse than 0.5m if SNR goes down to 10dB. Precision, in general, improves towards higher elevation angles. Critical biases are introduced by atmospheric and ionospheric refraction. Corresponding correction strategies are still under investigation.

Generation of Unbiased Ionospheric Corrections in Brazilian Region for GNSS positioning based on SSR concept

Science.gov (United States)

Monico, J. F. G.; De Oliveira, P. S., Jr.; Morel, L.; Fund, F.; Durand, S.; Durand, F.

2017-12-01

Mitigation of ionospheric effects on GNSS (Global Navigation Satellite System) signals is very challenging, especially for GNSS positioning applications based on SSR (State Space Representation) concept, which requires the knowledge of spatial correlated errors with considerable accuracy level (centimeter). The presence of satellite and receiver hardware biases on GNSS measurements difficult the proper estimation of ionospheric corrections, reducing their physical meaning. This problematic can lead to ionospheric corrections biased of several meters and often presenting negative values, which is physically not possible. In this contribution, we discuss a strategy to obtain SSR ionospheric corrections based on GNSS measurements from CORS (Continuous Operation Reference Stations) Networks with minimal presence of hardware biases and consequently physical meaning. Preliminary results are presented on generation and application of such corrections for simulated users located in Brazilian region under high level of ionospheric activity.

A data-driven approach for denoising GNSS position time series

Science.gov (United States)

Li, Yanyan; Xu, Caijun; Yi, Lei; Fang, Rongxin

2017-12-01

Global navigation satellite system (GNSS) datasets suffer from common mode error (CME) and other unmodeled errors. To decrease the noise level in GNSS positioning, we propose a new data-driven adaptive multiscale denoising method in this paper. Both synthetic and real-world long-term GNSS datasets were employed to assess the performance of the proposed method, and its results were compared with those of stacking filtering, principal component analysis (PCA) and the recently developed multiscale multiway PCA. It is found that the proposed method can significantly eliminate the high-frequency white noise and remove the low-frequency CME. Furthermore, the proposed method is more precise for denoising GNSS signals than the other denoising methods. For example, in the real-world example, our method reduces the mean standard deviation of the north, east and vertical components from 1.54 to 0.26, 1.64 to 0.21 and 4.80 to 0.72 mm, respectively. Noise analysis indicates that for the original signals, a combination of power-law plus white noise model can be identified as the best noise model. For the filtered time series using our method, the generalized Gauss-Markov model is the best noise model with the spectral indices close to - 3, indicating that flicker walk noise can be identified. Moreover, the common mode error in the unfiltered time series is significantly reduced by the proposed method. After filtering with our method, a combination of power-law plus white noise model is the best noise model for the CMEs in the study region.

Multi-GNSS PPP-RTK: From Large- to Small-Scale Networks

Directory of Open Access Journals (Sweden)

Nandakumaran Nadarajah

2018-04-01

Full Text Available Precise point positioning (PPP and its integer ambiguity resolution-enabled variant, PPP-RTK (real-time kinematic, can benefit enormously from the integration of multiple global navigation satellite systems (GNSS. In such a multi-GNSS landscape, the positioning convergence time is expected to be reduced considerably as compared to the one obtained by a single-GNSS setup. It is therefore the goal of the present contribution to provide numerical insights into the role taken by the multi-GNSS integration in delivering fast and high-precision positioning solutions (sub-decimeter and centimeter levels using PPP-RTK. To that end, we employ the Curtin PPP-RTK platform and process data-sets of GPS, BeiDou Navigation Satellite System (BDS and Galileo in stand-alone and combined forms. The data-sets are collected by various receiver types, ranging from high-end multi-frequency geodetic receivers to low-cost single-frequency mass-market receivers. The corresponding stations form a large-scale (Australia-wide network as well as a small-scale network with inter-station distances less than 30 km. In case of the Australia-wide GPS-only ambiguity-float setup, 90% of the horizontal positioning errors (kinematic mode are shown to become less than five centimeters after 103 min. The stated required time is reduced to 66 min for the corresponding GPS + BDS + Galieo setup. The time is further reduced to 15 min by applying single-receiver ambiguity resolution. The outcomes are supported by the positioning results of the small-scale network.

Analysis of seasonal position variation for selected GNSS sites in Poland using loading modelling and GRACE data

Directory of Open Access Journals (Sweden)

Marcin Rajner

2017-07-01

Full Text Available In this study we compared weekly GNSS position time series with modelled values of crustal deformations on the basis of Gravity Recovery and Climate Experiment (GRACE data. The Global Navigation Satellite Systems (GNSS time series were taken from homogeneously reprocessed global network solutions within the International GNSS Service (IGS Reprocessing 1 project and from regional solutions performed by Warsaw University of Technology (WUT European Permanent Network (EPN Local Analysis Center (LAC within the EPN reprocessing project. Eight GNSS sites from the territory of Poland with observation timespans between 2.5 and 13 years were selected for this study. The Total Water Equivalent (TWE estimation from GRACE data was used to compute deformations using the Green's function formalism. High frequency components were removed from GRACE data to avoid aliasing problems. Since GRACE observes mainly the mass transport in continental storage of water, we also compared GRACE deformations and the GNSS position time series, with the deformations computed on the basis of a hydrosphere model. We used the output of Water GAP Hydrology Model (WGHM to compute deformations in the same manner as for the GRACE data. The WGHM gave slightly larger amplitudes than GNSS and GRACE. The atmospheric non-tidal loading effect was removed from GNSS position time series before comparing them with modelled deformations. The results confirmed that the major part of observed seasonal variations for GNSS vertical components can be attributed to the hydrosphere loading. The results for these components agree very well both in the amplitude and phase. The decrease in standard deviation of the residual GNSS position time series for vertical components corrected for the hydrosphere loading reached maximally 36% and occurred for all but one stations for both global and regional solutions. For horizontal components the amplitudes are about three times smaller than for vertical

Real-time Inversion of Tsunami Source from GNSS Ground Deformation Observations and Tide Gauges.

Science.gov (United States)

Arcas, D.; Wei, Y.

2017-12-01

Over the last decade, the NOAA Center for Tsunami Research (NCTR) has developed an inversion technique to constrain tsunami sources based on the use of Green's functions in combination with data reported by NOAA's Deep-ocean Assessment and Reporting of Tsunamis (DART®) systems. The system has consistently proven effective in providing highly accurate tsunami forecasts of wave amplitude throughout an entire basin. However, improvement is necessary in two critical areas: reduction of data latency for near-field tsunami predictions and reduction of maintenance cost of the network. Two types of sensors have been proposed as supplementary to the existing network of DART®systems: Global Navigation Satellite System (GNSS) stations and coastal tide gauges. The use GNSS stations to provide autonomous geo-spatial positioning at specific sites during an earthquake has been proposed in recent years to supplement the DART® array in tsunami source inversion. GNSS technology has the potential to provide substantial contributions in the two critical areas of DART® technology where improvement is most necessary. The present study uses GNSS ground displacement observations of the 2011 Tohoku-Oki earthquake in combination with NCTR operational database of Green's functions, to produce a rapid estimate of tsunami source based on GNSS observations alone. The solution is then compared with that obtained via DART® data inversion and the difficulties in obtaining an accurate GNSS-based solution are underlined. The study also identifies the set of conditions required for source inversion from coastal tide-gauges using the degree of nonlinearity of the signal as a primary criteria. We then proceed to identify the conditions and scenarios under which a particular gage could be used to invert a tsunami source.

Recognition elements in rRNA for the tylosin resistance methyltransferase RlmA(II)

DEFF Research Database (Denmark)

Lebars, Isabelle; Husson, Clotilde; Yoshizawa, Satoko

2007-01-01

The methyltransferase RlmA(II) (formerly TlrB) is found in many Gram-positive bacteria, and methylates the N-1 position of nucleotide G748 within the loop of hairpin 35 in 23S rRNA. Methylation of the rRNA by RlmA(II) confers resistance to tylosin and other mycinosylated 16-membered ring macrolide......RNA substrate indicated that multiple contacts occur between RlmA(II) and nucleotides in stem-loops 33, 34 and 35. RlmA(II) appears to recognize its rRNA target through specific surface shape complementarity at the junction formed by these three helices. This means of recognition is highly similar...

Characterisation of current and future GNSS performance in urban canyons using a high quality 3-D urban model of Melbourne, Australia

Science.gov (United States)

Gang-jun, Liu; Kefei, Zhang; Falin, Wu; Liam, Densley; Retscher, Günther

2009-03-01

Global Navigation Satellite System (GNSS) is a critical space-borne geospatial infrastructure providing essential positioning supports to a range of location-sensitive applications. GNSS is currently dominated by the US Global Positioning System (GPS) constellation. The next generation GNSS is expected to offer more satellites, better positioning provision, and improved availability and continuity of navigation support. However, GNSS performance in 3-D urban environments is problematic because GNSS signals are either completely blocked or severely degraded by high-rising geographic features like buildings. The aim of this study is to gain an in-depth understanding of the changing spatial patterns of GNSS performance, measured by the number of visible satellites (NVS) and position dilution-of-precision (PDOP), in the urban canyons of Melbourne, Australia. The methodology used includes the following steps: (1) determination of the dynamic orbital positions of current and future GNSS satellites; (2) development of a 3-D urban model of high geometric quality for Melbourne Central Business District (CBD); (3) evaluation of GNSS performance for every specified location in the urban canyons; and (4) visualisation and characterisation of the dynamic spatial patterns of GNSS performances in the urban canyons. As expected, the study shows that the integration of the GPS and Galileo constellations results in higher availability and stronger geometry, leading to significant improvement of GNSS performance in urban canyons of Melbourne CBD. Some conclusions are drawn and further research currently undertaken is also outlined.

GNSS, Satellite Altimetry and Formosat-3/COSMIC for Determination of Ionosphere Parameters

Science.gov (United States)

Mahdi Alizadeh Elizei, M.; Schuh, Harald; Schmidt, Michael; Todorova, Sonya

The dispersion of ionosphere with respect to the microwave signals allows gaining information about the parameters of this medium in terms of the electron density (Ne), or the Total Elec-tron Content (TEC). In the last decade space geodetic techniques, such as Global Navigation Satellite System (GNSS), satellite altimetry missions, and Low Earth Orbiting (LEO) satel-lites have turned into a promising tool for remote sensing the ionosphere. The dual-frequency GNSS observations provide the main input data for development of Global Ionosphere Maps (GIM). However, the GNSS stations are heterogeneously distributed, with large gaps particu-larly over the sea surface, which lowers the precision of the GIM over these areas. Conversely, dual-frequency satellite altimetry missions provide information about the ionosphere precisely above the sea surface. In addition, LEO satellites such as Formosat-3/COSMIC (F-3/C) pro-vide well-distributed information of ionosphere around the world. In this study we developed GIMs of VTEC from combination of GNSS, satellite altimetry and F-3/C data with temporal resolution of 2 hours and spatial resolution of 5 degree in longitude and 2.5 degree in latitude. The combined GIMs provide a more homogeneous global coverage and higher precision and reliability than results of each individual technique.

PROPOSTA DE MÉTODO DE REDE GNSS POR PPP E ANÁLISE DE CONFIABILIDADE

Directory of Open Access Journals (Sweden)

Carolina Collischonn

Full Text Available Embora o método de posicionamento GNSS tradicionalmente utilizado em redes geodésicas seja o relativo. O nível de acurácia obtido com o método de Posicionamento por Ponto Preciso (PPP abre uma nova perspectiva. No PPP são utilizados dados de apenas um receptor GNSS e é fundamental o uso de efemérides e correções dos relógios dos satélites, ambas com alta precisão. Neste artigo é apresentada uma metodologia de desenvolvimento de rede utilizando dados GNSS processados pelo método de PPP e a verificação da sua potencialidade em aplicações geodésicas. Os dados utilizados são de estações GNSS pertencentes à RBMC/IBGE. O serviço de processamento de PPP utilizado é o fornecido pelo IBGE. A partir dos resultados foram feitas análises para verificar a aplicabilidade da metodologia descrita em rede com dados GNSS de 24, 6 e 4 horas de rastreio. Após o ajustamento, os testes global e data snooping foram aplicados e também foi analisada a confiabilidade da rede com o objetivo de avaliar o método proposto, além de verificar a influência do tempo de rastreio nos resultados.

AMIGHO: Automated Metadata Ingest for GNSS Hydrology within OODT

Data.gov (United States)

National Aeronautics and Space Administration — GNSS sites installed by surveyors and geophysicists to measure land motions can also provide valuable and cost-efficient information about three critical hydrologic...

Evaluation of spatial and temporal characteristics of GNSS-derived ZTD estimates in Nigeria

Science.gov (United States)

Isioye, Olalekan Adekunle; Combrinck, Ludwig; Botai, Joel

2018-05-01

This study presents an in-depth analysis to comprehend the spatial and temporal variability of zenith tropospheric delay (ZTD) over Nigeria during the period 2010-2014, using estimates from Global Navigation Satellite Systems (GNSS) data. GNSS data address the drawbacks in traditional techniques (e.g. radiosondes) by means of observing periodicities in ZTD. The ZTD estimates show weak spatial dependence among the stations, though this can be attributed to the density of stations in the network. Tidal oscillations are noticed at the GNSS stations. These oscillations have diurnal and semi-diurnal components. The diurnal components as seen from the ZTD are the principal source of the oscillations. This upshot may perhaps be ascribed to temporal variations in atmospheric water vapour on a diurnal scale. In addition, the diurnal ZTD cycles exhibited noteworthy seasonal dependence, with larger amplitudes in the rainy (wet) season and smaller ones in the harmattan (dry) season. Notably, the stations in the northern part of the country reach very high amplitudes in the months of June, July and August at the peak of the wet season, characterized by very high rainfall. This pinpoints the fact that in view of the small amount of atmospheric water vapour in the atmosphere, usually around 10%, its variations greatly influence the corresponding diurnal and seasonal discrepancies of ZTD. This study further affirms the prospective relevance of ground-based GNSS data to atmospheric studies. GNSS data analysis is therefore recommended as a tool for future exploration of Nigerian weather and climate.

Resolving Peak Ground Displacements in Real-Time GNSS PPP Solutions

Science.gov (United States)

Hodgkinson, K. M.; Mencin, D.; Mattioli, G. S.; Sievers, C.; Fox, O.

2017-12-01

The goal of early earthquake warning (EEW) systems is to provide warning of impending ground shaking to the public, infrastructure managers, and emergency responders. Shaking intensity can be estimated using Ground Motion Prediction Equations (GMPEs), but only if site characteristics, hypocentral distance and event magnitude are known. In recent years work has been done analyzing the first few seconds of the seismic P wave to derive event location and magnitude. While initial rupture locations seem to be sufficiently constrained, it has been shown that P-wave magnitude estimates tend to saturate at M>7. Regions where major and great earthquakes occur may therefore be vulnerable to an underestimation of shaking intensity if only P waves magnitudes are used. Crowell et al., (2013) first demonstrated that Peak Ground Displacement (PGD) from long-period surface waves recorded by GNSS receivers could provide a source-scaling relation that does not saturate with event magnitude. GNSS PGD derived magnitudes could improve the accuracy of EEW GMPE calculations. If such a source-scaling method were to be implemented in EEW algorithms it is critical that the noise levels in real-time GNSS processed time-series are low enough to resolve long-period surface waves. UNAVCO currently operates 770 real-time GNSS sites, most of which are located along the North American-Pacific Plate Boundary. In this study, we present an analysis of noise levels observed in the GNSS Precise Point Positioning (PPP) solutions generated and distributed in real-time by UNAVCO for periods from seconds to hours. The analysis is performed using the 770 sites in the real-time network and data collected through July 2017. We compare noise levels determined from various monument types and receiver-antenna configurations. This analysis gives a robust estimation of noise levels in PPP solutions because the solutions analyzed are those that were generated in real-time and thus contain all the problems observed

PROPOSAL OF A TABLE TO CLASSIFY THE RELIABILITY OF BASELINES OBTAINED BY GNSS TECHNOLOGY

Directory of Open Access Journals (Sweden)

Paulo Cesar Lima Segantine

Full Text Available The correct data processing of GNSS measurements, as well as a correct interpretation of the results are fundamental factors for analysis of quality of land surveying works. In that sense, it is important to keep in mind that, although, the statistical data provided by the majority of commercials software used for GNSS data processing, describes the credibility of the work, they do not have consistent information about the reliability of the processed coordinates. Based on that assumption, this paper proposes a classification table to classify the reliability of baselines obtained through GNSS data processing. As data input, the GNSS measurements were performed during the years 2006 and 2008, considering different seasons of the year, geometric configurations of RBMC stations and baseline lengths. As demonstrated in this paper, parameters as baseline length, ambiguity solution, PDOP value and the precision of horizontal and vertical values of coordinates can be used as reliability parameters. The proposed classification guarantees the requirements of the Brazilian Law N( 10.267/2001 of the National Institute of Colonization and Agrarian Reform (INCRA

Monitoraggio in continuo di strutture e del territorio mediante la tecnologia GNSS

OpenAIRE

Poluzzi, Luca

2016-01-01

Al giorno d’oggi, la tecnologia GNSS può essere uno strumento utile, non solo in ambito di navigazione, ma anche per applicazioni di posizionamento di precisione come il monitoraggio di strutture o del territorio. Questa tecnica permette un controllo in continuo, anche da remoto, e ha un costo relativamente basso sia per quanto riguarda le strumentazioni che per gli aspetti di materializzazione e mantenimento. Nell’ottica di utilizzare la tecnologia GNSS per applicazioni di monitoraggio, il p...

LiDAR Scan Matching Aided Inertial Navigation System in GNSS-Denied Environments

OpenAIRE

Tang, Jian; Chen, Yuwei; Niu, Xiaoji; Wang, Li; Chen, Liang; Liu, Jingbin; Shi, Chuang; Hyyppä, Juha

2015-01-01

A new scan that matches an aided Inertial Navigation System (INS) with a low-cost LiDAR is proposed as an alternative to GNSS-based navigation systems in GNSS-degraded or -denied environments such as indoor areas, dense forests, or urban canyons. In these areas, INS-based Dead Reckoning (DR) and Simultaneous Localization and Mapping (SLAM) technologies are normally used to estimate positions as separate tools. However, there are critical implementation problems with each standalone system. Th...

Improvement of Klobuchar model for GNSS single-frequency ionospheric delay corrections

Science.gov (United States)

Wang, Ningbo; Yuan, Yunbin; Li, Zishen; Huo, Xingliang

2016-04-01

Broadcast ionospheric model is currently an effective approach to mitigate the ionospheric time delay for real-time Global Navigation Satellite System (GNSS) single-frequency users. Klobuchar coefficients transmitted in Global Positioning System (GPS) navigation message have been widely used in various GNSS positioning and navigation applications; however, this model can only reduce the ionospheric error by approximately 50% in mid-latitudes. With the emerging BeiDou and Galileo, as well as the modernization of GPS and GLONASS, more precise ionospheric correction models or algorithms are required by GNSS single-frequency users. Numerical analysis of the initial phase and nighttime term in Klobuchar algorithm demonstrates that more parameters should be introduced to better describe the variation of nighttime ionospheric total electron content (TEC). In view of this, several schemes are proposed for the improvement of Klobuchar algorithm. Performance of these improved Klobuchar-like models are validated over the continental and oceanic regions during high (2002) and low (2006) levels of solar activities, respectively. Over the continental region, GPS TEC generated from 35 International GNSS Service (IGS) and the Crust Movement Observation Network of China (CMONOC) stations are used as references. Over the oceanic region, TEC data from TOPEX/Poseidon and JASON-1 altimeters are used for comparison. A ten-parameter Klobuchar-like model, which describes the nighttime term as a linear function of geomagnetic latitude, is finally proposed for GNSS single-frequency ionospheric corrections. Compared to GPS TEC, while GPS broadcast model can correct for 55.0% and 49.5% of the ionospheric delay for the year 2002 and 2006, respectively, the proposed ten-parameter Klobuchar-like model can reduce the ionospheric error by 68.4% and 64.7% for the same period. Compared to TOPEX/Poseidon and JASON-1 TEC, the improved ten-parameter Klobuchar-like model can mitigate the ionospheric

Complete Element Abundances of Nine Stars in the r-process Galaxy Reticulum II

Science.gov (United States)

Ji, Alexander P.; Frebel, Anna; Simon, Joshua D.; Chiti, Anirudh

2016-10-01

We present chemical abundances derived from high-resolution Magellan/Magellan Inamori Kyocera Echelle spectra of the nine brightest known red giant members of the ultra-faint dwarf galaxy Reticulum II (Ret II). These stars span the full metallicity range of Ret II (-3.5 contaminated known r-process pattern. The abundances of lighter elements up to the iron peak are otherwise similar to abundances of stars in the halo and in other ultra-faint dwarf galaxies. However, the scatter in abundance ratios is large enough to suggest that inhomogeneous metal mixing is required to explain the chemical evolution of this galaxy. The presence of low amounts of neutron-capture elements in other ultra-faint dwarf galaxies may imply the existence of additional r-process sites besides the source of r-process elements in Ret II. Galaxies like Ret II may be the original birth sites of r-process enhanced stars now found in the halo. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

A Hands-on Physical Analog Demonstration of Real-Time Volcano Deformation Monitoring with GNSS/GPS

Science.gov (United States)

Jones, J. R.; Schobelock, J.; Nguyen, T. T.; Rajaonarison, T. A.; Malloy, S.; Njinju, E. A.; Guerra, L.; Stamps, D. S.; Glesener, G. B.

2017-12-01

Teaching about volcano deformation and how scientists study these processes using GNSS/GPS may present some challenge since the volcanoes and/or GNSS/GPS equipment are not quite accessible to most teachers. Educators and curriculum materials specialists have developed and shared a number of activities and demonstrations to help students visualize volcanic processes and ways scientist use GNSS/GPS in their research. From resources provided by MEDL (the Modeling and Educational Demonstrations Laboratory) in the Department of Geosciences at Virginia Tech, we combined multiple materials and techniques from these previous works to produce a hands-on physical analog model from which students can learn about GNSS/GPS studies of volcano deformation. The model functions as both a qualitative and quantitative learning tool with good analogical affordances. In our presentation, we will describe multiple ways of teaching with the model, what kinds of materials can be used to build it, and ways we think the model could be enhanced with the addition of Vernier sensors for data collection.

Analysis strategies for combining continuous and episodic GNSS for studies of neo-tectonics in Northern-Norway

Science.gov (United States)

Kierulf, Halfdan Pascal

2017-09-01

Crustal deformation in the seismically active Nordland area in Northern Norway is estimated based on a combination of data from local episodic epGNSS campaigns (three 5-day campaigns in 1999, 2008 and 2015) and continuously operating cGNSS stations in the area that were mainly established in 2008 and in 2009. To establish a local long-term stable reference frame, which is consistent both with the epGNSS network and the network of newer cGNSS, a three-step procedure for reference frame realization is used to get consistent results from all the stations in the area. Analysis of the main error sources shows that uncertainties for the episodic epGNSS stations are around 0.2 mm/yr in the horizontal components and 0.5 mm/yr in the vertical component. The results support earlier findings that Ranafjord area of the Nordland is undergoing crustal spreading with horizontal displacement velocities of ca. 1.0 ± 0.2 mm/yr, predominantly in the east-west direction. The results also show a gradient in the uplift along the coast of Nordland that is larger than predicted by existing glacial isostatic adjustment models.

by monitoring microgravity and GPS/GNSS methods

Indian Academy of Sciences (India)

Dokuz Eylul University, Department of Geophysical Engineering, Tınaztepe Campus, Buca, Izmir, Turkey. ∗. Corresponding author. e-mail: .... For processing GPS/GNSS data, the software, which is called GAMIT/GLOBK (Herring 2009; .... trend for DEU6, DEU7, DEU8, DEU5, DEU11 measurement points (uplift), stable for ...

An SINS/GNSS Ground Vehicle Gravimetry Test Based on SGA-WZ02

Directory of Open Access Journals (Sweden)

Ruihang Yu

2015-09-01

Full Text Available In March 2015, a ground vehicle gravimetry test was implemented in eastern Changsha to assess the repeatability and accuracy of ground vehicle SINS/GNSS gravimeter—SGA-WZ02. The gravity system developed by NUDT consisted of a Strapdown Inertial Navigation System (SINS, a Global Navigation Satellite System (GNSS remote station on test vehicle, a GNSS static master station on the ground, and a data logging subsystem. A south-north profile of 35 km along the highway in eastern Changsha was chosen and four repeated available measure lines were obtained. The average speed of a vehicle is 40 km/h. To assess the external ground gravity disturbances, precise ground gravity data was built by CG-5 precise gravimeter as the reference. Under relative smooth conditions, internal accuracy among repeated lines shows an average agreement at the level of 1.86 mGal for half wavelengths about 1.1 km, and 1.22 mGal for 1.7 km. The root-mean-square (RMS of difference between calculated gravity data and reference data is about 2.27 mGal/1.1 km, and 1.74 mGal/1.7 km. Not all of the noises caused by vehicle itself and experiments environments were eliminated in the primary results. By means of selecting reasonable filters and improving the GNSS observation conditions, further developments in ground vehicle gravimetry are promising.

Influence of Ionospheric Weather on GNSS Radio Occultation Signals

Science.gov (United States)

Yue, X.; Schreiner, W. S.; Pedatella, N. M.; Kuo, Y. H.

2016-12-01

Transient loss of lock (LOL) is one of the key space weather effects on the Global Navigation Satellite System (GNSS). Based on the Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) Global Positioning System (GPS) radio occultation (RO) observations during 2007-2011, we have analyzed the signal cycle slip (CS) occurrence comprehensively and its correlation to the ionospheric weather phenomena such as sporadic E (Es), equatorial F region irregularity (EFI), and the ionospheric equatorial ionization anomaly (EIA). The high vertical resolution of RO observations enables us to distinguish the CS resulting from different ionospheric layers clearly on a global scale. In the E layer, the CS is dominated by the Es occurrence, while in the F layer, the CS is mainly related to the EIA and EFI at low and equatorial latitudes. In the polar region, the CS is primarily related to polar cap electron density gradients. The overall average CS (> 6 cycles) occurrence is 23% per occultation, with the E (50-150 km) and F (150-600 km) layers contributing 8.3% and 14.7%, respectively. Awareness of the effect of the ionospheric weather on the CS of the low-Earth-orbit (LEO)-based GNSS signal could be beneficial to a variety of applications, including the LEO-based GNSS data processing and the corresponding hardware/firmware design.

MAPPING GNSS RESTRICTED ENVIRONMENTS WITH A DRONE TANDEM AND INDIRECT POSITION CONTROL

Directory of Open Access Journals (Sweden)

E. Cledat

2017-08-01

Full Text Available The problem of autonomously mapping highly cluttered environments, such as urban and natural canyons, is intractable with the current UAV technology. The reason lies in the absence or unreliability of GNSS signals due to partial sky occlusion or multi-path effects. High quality carrier-phase observations are also required in efficient mapping paradigms, such as Assisted Aerial Triangulation, to achieve high ground accuracy without the need of dense networks of ground control points. In this work we consider a drone tandem in which the first drone flies outside the canyon, where GNSS constellation is ideal, visually tracks the second drone and provides an indirect position control for it. This enables both autonomous guidance and accurate mapping of GNSS restricted environments without the need of ground control points. We address the technical feasibility of this concept considering preliminary real-world experiments in comparable conditions and we perform a mapping accuracy prediction based on a simulation scenario.

A regional GNSS-VTEC model over Nigeria using neural networks: A novel approach

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Daniel Okoh

2016-01-01

Full Text Available A neural network model of the Global Navigation Satellite System – vertical total electron content (GNSS-VTEC over Nigeria is developed. A new approach that has been utilized in this work is the consideration of the International Reference Ionosphere's (IRI's critical plasma frequency (foF2 parameter as an additional neuron for the network's input layer. The work also explores the effects of using various other input layer neurons like disturbance storm time (DST and sunspot number. All available GNSS data from the Nigerian Permanent GNSS Network (NIGNET were used, and these cover the period from 2011 to 2015, for 14 stations. Asides increasing the learning accuracy of the networks, the inclusion of the IRI's foF2 parameter as an input neuron is ideal for making the networks to learn long-term solar cycle variations. This is important especially for regions, like in this work, where the GNSS data is available for less than the period of a solar cycle. The neural network model developed in this work has been tested for time-varying and spatial performances. The latest 10% of the GNSS observations from each of the stations were used to test the forecasting ability of the networks, while data from 2 of the stations were entirely used for spatial performance testing. The results show that root-mean-squared-errors were generally less than 8.5 TEC units for all modes of testing performed using the optimal network. When compared to other models, the model developed in this work was observed to reduce the prediction errors to about half those of the NeQuick and the IRI model.

GEROS-ISS: Ocean Remote Sensing with GNSS Reflectometry from the International Space Station

DEFF Research Database (Denmark)

Wickert, Jens; Andersen, Ole Baltazar; Camps, Adriano

on exploiting reflected signals of opportunity from Global Navigation Satellite Systems (GNSS) at L-band to measure key parameters of ocean surfaces. GEROS will utilize the U.S. American GPS (Global Positioning System) and pioneer the exploitation of signals from Galileo and possibly other GNSS systems (GLONASS......, QZSS, BeiDou), for reflectometry and occultation, thereby improving the accuracy as well as the spatio-temporal resolution of the derived geophysical properties. The primary mission objectives of GEROS are: (1) to measure the altimetric sea surface height of the ocean using reflected GNSS signals...... the oceanographic significance of the expected measurements and to demonstrate the usefulness of the GEROS concept. The presentation will give an overview on the current status of the GEROS experiment, review the science activities within the international GARCA study and related ESA-supported science activities....

Evaluation of RTKLIB's Positioning Accuracy Using low-cost GNSS Receiver and ASG-EUPOS

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Bartosz Wisniewski

2013-03-01

Full Text Available The paper focuses on a comparison of different positioning methods provided by free and open source software (FOSS package called RTKLIB. The RTKLIB supports real-time and post-processed positioning. The most important modes of operation tested by the authors are Kinematic, Static, Fixed and Precise Point Positioning (PPP. The data for evaluation were obtained from low-cost Global Navigation Satellite System (GNSS receiver. The tested receiver was based on the u-blox's LEA-6T GNSS module. This receiver provides different types of information including raw carrier phase measurements. It gives the possibility for centimeter-level precision of positioning. As the supporting source of data ASG-EUPOS system was used. ASG-EUPOS is a Polish network of GNSS reference stations providing the real-time corrections and post processing services for the entire territory of Poland.

Impacts of GNSS position offsets on global frame stability

Science.gov (United States)

Griffiths, Jake; Ray, Jim

2014-05-01

Positional offsets appear in Global Navigation Satellite System (GNSS) time series for a variety of reasons. Antenna or radome changes are the most common cause for these discontinuities. Many others are from earthquakes, receiver changes, and different anthropogenic modifications at or near the stations. Some jumps appear for unknown or undocumented reasons. The accurate determination of station velocities, and therefore geophysical parameters and terrestrial reference frames, requires that positional offsets be correctly found and compensated. Williams (2003) found that undetected offsets introduce a random walk error component in individual station time series. The topic of detecting positional offsets has received considerable attention in recent years (e.g., Detection of Offsets in GPS Experiment; DOGEx), and most research groups using GNSS have adopted a combination of manual and automated methods for finding them. The removal of a positional offset is usually handled by estimating the average station position on both sides of the discontinuity, assuming a constant, continuous velocity. This is sufficient in the absence of time-correlated errors. However, GNSS time series contain systematic and power-law errors (white to random walk noise). In this paper, we aim to evaluate the impact to both individual station results and the overall stability of the global reference frame from adding increasing numbers of positional discontinuities. We use the International GNSS Service (IGS) weekly SINEX files, and iteratively insert positional offset parameters at the midpoint of each data segment. Each iteration includes a restacking of the modified SINEX files using the CATREF software from Institut National de l'Information Géographique et Forestière (IGN) to estimate: regularized station positions, secular velocities, Earth orientation parameters, Helmert frame alignment parameters, and the empirical shifts across all positional discontinuities. A comparison of the

Tightly-Coupled Integration of Multi-GNSS Single-Frequency RTK and MEMS-IMU for Enhanced Positioning Performance.

Science.gov (United States)

Li, Tuan; Zhang, Hongping; Niu, Xiaoji; Gao, Zhouzheng

2017-10-27

Dual-frequency Global Positioning System (GPS) Real-time Kinematics (RTK) has been proven in the past few years to be a reliable and efficient technique to obtain high accuracy positioning. However, there are still challenges for GPS single-frequency RTK, such as low reliability and ambiguity resolution (AR) success rate, especially in kinematic environments. Recently, multi-Global Navigation Satellite System (multi-GNSS) has been applied to enhance the RTK performance in terms of availability and reliability of AR. In order to further enhance the multi-GNSS single-frequency RTK performance in terms of reliability, continuity and accuracy, a low-cost micro-electro-mechanical system (MEMS) inertial measurement unit (IMU) is adopted in this contribution. We tightly integrate the single-frequency GPS/BeiDou/GLONASS and MEMS-IMU through the extended Kalman filter (EKF), which directly fuses the ambiguity-fixed double-differenced (DD) carrier phase observables and IMU data. A field vehicular test was carried out to evaluate the impacts of the multi-GNSS and IMU on the AR and positioning performance in different system configurations. Test results indicate that the empirical success rate of single-epoch AR for the tightly-coupled single-frequency multi-GNSS RTK/INS integration is over 99% even at an elevation cut-off angle of 40°, and the corresponding position time series is much more stable in comparison with the GPS solution. Besides, GNSS outage simulations show that continuous positioning with certain accuracy is possible due to the INS bridging capability when GNSS positioning is not available.

Precise orbit determination of Multi-GNSS constellation including GPS GLONASS BDS and GALIEO

Science.gov (United States)

Dai, Xiaolei

2014-05-01

In addition to the existing American global positioning system (GPS) and the Russian global navigation satellite system (GLONASS), the new generation of GNSS is emerging and developing, such as the Chinese BeiDou satellite navigation system (BDS) and the European GALILEO system. Multi-constellation is expected to contribute to more accurate and reliable positioning and navigation service. However, the application of multi-constellation challenges the traditional precise orbit determination (POD) strategy that was designed usually for single constellation. In this contribution, we exploit a more rigorous multi-constellation POD strategy for the ongoing IGS multi-GNSS experiment (MGEX) where the common parameters are identical for each system, and the frequency- and system-specified parameters are employed to account for the inter-frequency and inter-system biases. Since the authorized BDS attitude model is not yet released, different BDS attitude model are implemented and their impact on orbit accuracy are studied. The proposed POD strategy was implemented in the PANDA (Position and Navigation Data Analyst) software and can process observations from GPS, GLONASS, BDS and GALILEO together. The strategy is evaluated with the multi-constellation observations from about 90 MGEX stations and BDS observations from the BeiDou experimental tracking network (BETN) of Wuhan University (WHU). Of all the MGEX stations, 28 stations record BDS observation, and about 80 stations record GALILEO observations. All these data were processed together in our software, resulting in the multi-constellation POD solutions. We assessed the orbit accuracy for GPS and GLONASS by comparing our solutions with the IGS final orbit, and for BDS and GALILEO by overlapping our daily orbit solution. The stability of inter-frequency bias of GLONASS and inter-system biases w.r.t. GPS for GLONASS, BDS and GALILEO were investigated. At last, we carried out precise point positioning (PPP) using the multi

CODE's new solar radiation pressure model for GNSS orbit determination

Science.gov (United States)

Arnold, D.; Meindl, M.; Beutler, G.; Dach, R.; Schaer, S.; Lutz, S.; Prange, L.; Sośnica, K.; Mervart, L.; Jäggi, A.

2015-08-01

The Empirical CODE Orbit Model (ECOM) of the Center for Orbit Determination in Europe (CODE), which was developed in the early 1990s, is widely used in the International GNSS Service (IGS) community. For a rather long time, spurious spectral lines are known to exist in geophysical parameters, in particular in the Earth Rotation Parameters (ERPs) and in the estimated geocenter coordinates, which could recently be attributed to the ECOM. These effects grew creepingly with the increasing influence of the GLONASS system in recent years in the CODE analysis, which is based on a rigorous combination of GPS and GLONASS since May 2003. In a first step we show that the problems associated with the ECOM are to the largest extent caused by the GLONASS, which was reaching full deployment by the end of 2011. GPS-only, GLONASS-only, and combined GPS/GLONASS solutions using the observations in the years 2009-2011 of a global network of 92 combined GPS/GLONASS receivers were analyzed for this purpose. In a second step we review direct solar radiation pressure (SRP) models for GNSS satellites. We demonstrate that only even-order short-period harmonic perturbations acting along the direction Sun-satellite occur for GPS and GLONASS satellites, and only odd-order perturbations acting along the direction perpendicular to both, the vector Sun-satellite and the spacecraft's solar panel axis. Based on this insight we assess in the third step the performance of four candidate orbit models for the future ECOM. The geocenter coordinates, the ERP differences w. r. t. the IERS 08 C04 series of ERPs, the misclosures for the midnight epochs of the daily orbital arcs, and scale parameters of Helmert transformations for station coordinates serve as quality criteria. The old and updated ECOM are validated in addition with satellite laser ranging (SLR) observations and by comparing the orbits to those of the IGS and other analysis centers. Based on all tests, we present a new extended ECOM which

The Analysis of Height System Definition and the High Precision GNSS Replacing Leveling Method

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ZHANG Chuanyin

2017-08-01

Full Text Available Based on the definition of height system, the gravitational equipotential property of height datum surface is discussed in this paper, differences of the heights at ground points that defined in different height systems are tested and analyzed as well. A new method for replacing leveling using GNSS is proposed to ensure the consistency between GNSS replacing leveling and spirit leveling at mm accuracy level. The main conclusions include:①For determining normal height at centimeter accuracy level, the datum surface of normal height should be the geoid. The 1985 national height datum of China adopts normal height system, its datum surface is the geoid passing the Qingdao zero point.②The surface of equi-orthometric height in the near earth space is parallel to the geoid. The combination of GNSS precise positioning and geoid model can be directly used for orthometric height determination. However, the normal height system is more advantageous for describing the terrain and relief.③Based on the proposed method of GNSS replacing leveling, the errors in geodetic height affect more on normal height result than the errors of geoid model, the former is about 1.5 times of the latter.

NUVEM - New methods to Use gnss water Vapor Estimates for Meteorology of Portugal

Science.gov (United States)

Fernandes, R. M. S.; Viterbo, P.; Bos, M. S.; Martins, J. P.; Sá, A. G.; Valentim, H.; Jones, J.

2014-12-01

NUVEM (New methods to Use gnss water Vapor Estimates for Meteorology of Portugal) is a collaborative project funded by the Portuguese National Science Foundation (FCT) aiming to implement a multi-disciplinary approach in order to operationalize the inclusion of GNSS-PWV estimates for nowcasting in Portugal, namely for the preparation of warnings of severe weather. To achieve such goal, the NUVEM project is divided in two major components: a) Development and implementation of methods to compute accurate estimates of PWV (Precipitable Water Vapor) in NRT (Near Real-Time); b) Integration of such estimates in nowcasting procedures in use at IPMA (Portuguese Meteorological Service). Methodologies will be optimized at SEGAL to passive and actively access to the data; the PWV estimations will be computed using PPP (Precise Point Positioning), which permits the estimation of each individual station separately; solutions will be validated using internal and external values; and computed solutions will be transferred timely to the IPMA Operational Center. Validation of derived estimations using robust statistics is an important component of the project. The need for sending computed values as soon as possible to IPMA requires fast but reliable internal (e.g., noise estimation) and external (e.g., feedback from IPMA using other sensors like radiosondes) assessment of the quality of the PWV estimates. At IPMA, the goal is to implement the operational use of GNSS-PWV to assist weather nowcasting in Portugal. This will be done with the assistance of the Meteo group of IDL. Maps of GNSS-PWV will be automatically created and compared with solutions provided by other operational systems in order to help IPMA to detect suspicious patterns at near real time. This will be the first step towards the assimilation of GNSS-PWV estimates at IPMA nowcasting models. The NUVEM (EXPL/GEO-MET/0413/2013) project will also contribute to the active participation of Portugal at the COST Action ES

An adaptive deep-coupled GNSS/INS navigation system with hybrid pre-filter processing

Science.gov (United States)

Wu, Mouyan; Ding, Jicheng; Zhao, Lin; Kang, Yingyao; Luo, Zhibin

2018-02-01

The deep-coupling of a global navigation satellite system (GNSS) with an inertial navigation system (INS) can provide accurate and reliable navigation information. There are several kinds of deeply-coupled structures. These can be divided mainly into coherent and non-coherent pre-filter based structures, which have their own strong advantages and disadvantages, especially in accuracy and robustness. In this paper, the existing pre-filters of the deeply-coupled structures are analyzed and modified to improve them firstly. Then, an adaptive GNSS/INS deeply-coupled algorithm with hybrid pre-filters processing is proposed to combine the advantages of coherent and non-coherent structures. An adaptive hysteresis controller is designed to implement the hybrid pre-filters processing strategy. The simulation and vehicle test results show that the adaptive deeply-coupled algorithm with hybrid pre-filters processing can effectively improve navigation accuracy and robustness, especially in a GNSS-challenged environment.

Clarifying the interplate main tectonic elements of Western Anatolia, Turkey by using GNSS velocities and Bouguer gravity anomalies

Science.gov (United States)

Çırmık, Ayça; Pamukçu, Oya

2017-10-01

In this study, the GNSS and gravity data were processed and compared together for examining the continental structures of the Western Anatolia region which has very complicated tectonism. The GNSS data of three national projects were processed and GNSS velocities were found as approximately 25 mm per year towards southwest with respect to the Eurasia fixed frame. In order to investigate the interplate motions of the region, the Anatolian and Aegean block solutions were calculated and the differences in directions and amplitudes of velocities were observed particularly in the Anatolian block solution. Due to the Anatolian block solutions, the study area was grouped into three regions and compared with the tectonic structures as the first time for Western Anatolia by this study. Additionally, W-E and N-S relative GNSS solutions were obtained for observing the possible tectonic borders of the study area. Besides, 2nd order horizontal derivative and low-pass filter methods were applied to Bouguer gravity anomalies and the results of the gravity applications and the changes on crustal-mantle interface were compared with the GNSS horizontal velocities.

A Filtering of Incomplete GNSS Position Time Series with Probabilistic Principal Component Analysis

Science.gov (United States)

Gruszczynski, Maciej; Klos, Anna; Bogusz, Janusz

2018-04-01

For the first time, we introduced the probabilistic principal component analysis (pPCA) regarding the spatio-temporal filtering of Global Navigation Satellite System (GNSS) position time series to estimate and remove Common Mode Error (CME) without the interpolation of missing values. We used data from the International GNSS Service (IGS) stations which contributed to the latest International Terrestrial Reference Frame (ITRF2014). The efficiency of the proposed algorithm was tested on the simulated incomplete time series, then CME was estimated for a set of 25 stations located in Central Europe. The newly applied pPCA was compared with previously used algorithms, which showed that this method is capable of resolving the problem of proper spatio-temporal filtering of GNSS time series characterized by different observation time span. We showed, that filtering can be carried out with pPCA method when there exist two time series in the dataset having less than 100 common epoch of observations. The 1st Principal Component (PC) explained more than 36% of the total variance represented by time series residuals' (series with deterministic model removed), what compared to the other PCs variances (less than 8%) means that common signals are significant in GNSS residuals. A clear improvement in the spectral indices of the power-law noise was noticed for the Up component, which is reflected by an average shift towards white noise from - 0.98 to - 0.67 (30%). We observed a significant average reduction in the accuracy of stations' velocity estimated for filtered residuals by 35, 28 and 69% for the North, East, and Up components, respectively. CME series were also subjected to analysis in the context of environmental mass loading influences of the filtering results. Subtraction of the environmental loading models from GNSS residuals provides to reduction of the estimated CME variance by 20 and 65% for horizontal and vertical components, respectively.

Implementing real-time GNSS monitoring to investigate continental rift initiation processes

Science.gov (United States)

Jones, J. R.; Stamps, D. S.; Wauthier, C.; Daniels, M. D.; Saria, E.; Ji, K. H.; Mencin, D.; Ntambila, D.

2017-12-01

Continental rift initiation remains an elusive, yet fundamental, process in the context of plate tectonic theory. Our early work in the Natron Rift, Tanzania, the Earth's archetype continental rift initiation setting, indicates feedback between volcanic deformation and fault slip play a key role in the rift initiation process. We found evidence that fault slip on the Natron border fault during active volcanism at Ol Doniyo Lengai in 2008 required only 0.01 MPa of Coulomb stress change. This previous study was limited by GPS constraints 18 km from the volcano, rather than immediately adjacent on the rift shoulder. We hypothesize that fault slip adjacent to the volcano creeps, and without the need for active eruption. We also hypothesize silent slip events may occur over time-scales less than 1 day. To test our hypotheses we designed a GNSS network with 4 sites on the flanks of Ol Doinyo Lengai and 1 site on the adjacent Natron border fault with the capability to calculate 1 second, 3-5 cm precision positions. Data is transmitted to UNAVCO in real-time with remote satellite internet, which we automatically import to the EarthCube building block CHORDS (Cloud Hosted Real-time Data Services for the Geosciences) using our newly developed method. We use CHORDS to monitor and evaluate the health of our network while visualizing the GNSS data in real-time. In addition to our import method we have also developed user-friendly capabilities to export GNSS positions (longitude, latitude, height) with CHORDS assuming the data are available at UNAVCO in NMEA standardized format through the Networked Transport of RTCM via Internet Protocol (NTRIP). The ability to access the GNSS data that continuously monitors volcanic deformation, tectonics, and their interactions on and around Ol Doinyo Lengai is a crucial component in our investigation of continental rift initiation in the Natron Rift, Tanzania. Our new user-friendly methods developed to access and post-process real-time GNSS

Advanced algorithms for ionosphere modelling in GNSS applications within AUDITOR project

Science.gov (United States)

Goss, Andreas; Erdogan, Eren; Schmidt, Michael; Garcia-Rigo, Alberto; Hernandez-Pajares, Manuel; Lyu, Haixia; Nohutcu, Metin

2017-04-01

The H2020 project AUDITOR of the European Union started on January 1st 2016, with the participation of several European institutions and universities. The goal of the project is the implementation of a novel precise positioning technique, based on augmentation data in a customized GNSS receiver. Therefore more sophisticated ionospheric models have to be developed and implemented to increase the accuracy in real-time at the user side. Since the service should be available for the public, we use public data from GNSS networks (e.g. IGS, EUREF). The contributions of DGFI-TUM and UPC are focusing on the development of high accuracy GNSS algorithms to provide enhanced ionospheric corrections. This includes two major issues: 1. The existing mapping function to convert the slant total electron content (STEC) measurable by GNSS into the vertical total electron content (VTEC) is based on a so called single layer model (SLM), where all electrons are concentrated on an infinitesimal thin layer with fixed height (between 350 and 450 kilometers). This quantity is called the effective ionospheric height (EIH). An improvement of the mapping function shall be achieved by estimating more realistic numerical values for the EIH by means of a voxel-based tomographic model (TOMION). 2. The ionospheric observations are distributed rather unevenly over the globe and within specific regions. This inhomogeneous distribution is handled by data adaptive B-Spline approaches, with polynomial and trigonometric functions used for the latitude and longitude representations to provide high resolution VTEC maps for global and regional purposes. A Kalman filter is used as sequential estimator. The unknown parameters of the filter state vector are composed of the B-spline coefficients as well as the satellite and receiver DCBs. The resulting high accuracy ionosphere products will be disseminated to the users via downlink from a dedicated server to a receiver site. In this context, an appropriate

MONITORING HIGH-FREQUENCY OCEAN SIGNALS USING LOW-COST GNSS/IMU BUOYS

Directory of Open Access Journals (Sweden)

Y.-L. Huang

2016-06-01

Full Text Available In oceans there are different ocean signals covering the multi-frequencies including tsunami, meteotsunami, storm surge, as sea level change, and currents. These signals have the direct and significant impact on the economy and life of human-beings. Therefore, measuring ocean signals accurately becomes more and more important and necessary. Nowadays, there are many techniques and methods commonly used for monitoring oceans, but each has its limitation. For example, tide gauges only measure sea level relative to benchmarks and are disturbed unevenly, and satellite altimeter measurements are not continuous and inaccurate near coastal oceans. In addition, high-frequency ocean signals such as tsunami and meteotsunami cannot be sufficiently detected by 6-minutes tide gauge measurements or 10-day sampled altimetry data. Moreover, traditional accelerometer buoy is heavy, expensive and the low-frequency noise caused by the instrument is unavoidable. In this study, a small, low-cost and self-assembly autonomous Inertial Measurement Unit (IMU that independently collects continuous acceleration and angular velocity data is mounted on a GNSS buoy to provide the positions and tilts of the moving buoy. The main idea is to integrate the Differential GNSS (DGNSS or Precise Point Positioning (PPP solutions with IMU data, and then evaluate the performance by comparing with in situ tide gauges. The validation experiments conducted in the NCKU Tainan Hydraulics Laboratory showed that GNSS and IMU both can detect the simulated regular wave frequency and height, and the field experiments in the Anping Harbor, Tainan, Taiwan showed that the low-cost GNSS buoy has an excellent ability to observe significant wave heights in amplitude and frequency.

Preliminary results from the Arecibo Heating Experiment (HEX): HF to GNSS

Science.gov (United States)

Jackson-Booth, N.; Penney, R.; Bernhardt, P. A.; Martin, P. L.; Buckland, R.; Morton-Orr, T.; Nossa, E.; Buckland, R.

2017-12-01

The ionosphere is subject to many solar and terrestrial influences that can generate disturbances, causing degradation to modern communication and navigational systems. Whilst the disturbances are normally caused by natural phenomena such as hurricanes, earthquakes and solar storms; they can also be generated by artificially modifying the ionosphere. Artificial Ionospheric Modification (AIM) attempts to alter a small region of the ionosphere in order to perturb the RF propagation environment. This can be achieved through injecting the ionosphere with aerosols, chemicals or radio signals. The effects of any such modification can be detected through the deployment of sensors, including ground based high-frequency (HF) sounders and dual-band Global Navigation Satellite System (GNSS) receivers. HF sounders allow measurements of the bottom-side of the ionosphere. GNSS receivers offer a convenient means of obtaining information about the ionosphere, including ionospheric disturbances through changes in the derived total electron content information. The Heating EXperiment (HEX), which took place in March and May 2017, was designed to further our understanding of the phenomena caused by artificially heating a small region of the ionosphere, using the Arecibo facility in Puerto Rico. This was achieved by utilizing a HF measurement experiment spread between Texas and Trinidad and the deployment of a small scale travelling ionospheric disturbance (TID) network near the heater. The TID network comprised three GNSS receivers along baselines of approximately 4 km, located 20 km north of the heater. This paper presents preliminary results from the HEX campaign, including evidence of heating-induced disturbances enhancing propagation between Virginia and Trinidad. The implications of generated irregularities on GNSS will also be discussed.

Validating and comparing GNSS antenna calibrations

Science.gov (United States)

Kallio, Ulla; Koivula, Hannu; Lahtinen, Sonja; Nikkonen, Ville; Poutanen, Markku

2018-03-01

GNSS antennas have no fixed electrical reference point. The variation of the phase centre is modelled and tabulated in antenna calibration tables, which include the offset vector (PCO) and phase centre variation (PCV) for each frequency according to the elevations and azimuths of the incoming signal. Used together, PCV and PCO reduce the phase observations to the antenna reference point. The remaining biases, called the residual offsets, can be revealed by circulating and rotating the antennas on pillars. The residual offsets are estimated as additional parameters when combining the daily GNSS network solutions with full covariance matrix. We present a procedure for validating the antenna calibration tables. The dedicated test field, called Revolver, was constructed at Metsähovi. We used the procedure to validate the calibration tables of 17 antennas. Tables from the IGS and three different calibration institutions were used. The tests show that we were able to separate the residual offsets at the millimetre level. We also investigated the influence of the calibration tables from the different institutions on site coordinates by performing kinematic double-difference baseline processing of the data from one site with different antenna tables. We found small but significant differences between the tables.

Assessment of Measurement Distortions in GNSS Antenna Array Space-Time Processing

Directory of Open Access Journals (Sweden)

Thyagaraja Marathe

2016-01-01

Full Text Available Antenna array processing techniques are studied in GNSS as effective tools to mitigate interference in spatial and spatiotemporal domains. However, without specific considerations, the array processing results in biases and distortions in the cross-ambiguity function (CAF of the ranging codes. In space-time processing (STP the CAF misshaping can happen due to the combined effect of space-time processing and the unintentional signal attenuation by filtering. This paper focuses on characterizing these degradations for different controlled signal scenarios and for live data from an antenna array. The antenna array simulation method introduced in this paper enables one to perform accurate analyses in the field of STP. The effects of relative placement of the interference source with respect to the desired signal direction are shown using overall measurement errors and profile of the signal strength. Analyses of contributions from each source of distortion are conducted individually and collectively. Effects of distortions on GNSS pseudorange errors and position errors are compared for blind, semi-distortionless, and distortionless beamforming methods. The results from characterization can be useful for designing low distortion filters that are especially important for high accuracy GNSS applications in challenging environments.

The R-Process Alliance: 2MASS J09544277+5246414, the Most Actinide-enhanced R-II Star Known

Science.gov (United States)

Holmbeck, Erika M.; Beers, Timothy C.; Roederer, Ian U.; Placco, Vinicius M.; Hansen, Terese T.; Sakari, Charli M.; Sneden, Christopher; Liu, Chao; Lee, Young Sun; Cowan, John J.; Frebel, Anna

2018-06-01

We report the discovery of a new actinide-boost star, 2MASS J09544277+5246414, originally identified as a very bright (V = 10.1), extremely metal-poor ([Fe/H] = ‑2.99) K giant in the LAMOST survey, and found to be highly r-process-enhanced (r-II; [Eu/Fe] = +1.28]), during the snapshot phase of the R-Process Alliance (RPA). Based on a high signal-to-noise ratio (S/N), high-resolution spectrum obtained with the Harlan J. Smith 2.7 m telescope, this star is the first confirmed actinide-boost star found by RPA efforts. With an enhancement of [Th/Eu] = +0.37, 2MASS J09544277+5246414 is also the most actinide-enhanced r-II star yet discovered, and only the sixth metal-poor star with a measured uranium abundance ([U/Fe] = +1.40). Using the Th/U chronometer, we estimate an age of 13.0 ± 4.7 Gyr for this star. The unambiguous actinide-boost signature of this extremely metal-poor star, combined with additional r-process-enhanced and actinide-boost stars identified by the RPA, will provide strong constraints on the nature and origin of the r-process at early times.

Efficiency Improvement of Kalman Filter for GNSS/INS through One-Step Prediction of P Matrix

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Qingli Li

2015-01-01

Full Text Available To meet the real-time and low power consumption demands in MEMS navigation and guidance field, an improved Kalman filter algorithm for GNSS/INS was proposed in this paper named as one-step prediction of P matrix. Quantitative analysis of field test datasets was made to compare the navigation accuracy with the standard algorithm, which indicated that the degradation caused by the simplified algorithm is small enough compared to the navigation errors of the GNSS/INS system itself. Meanwhile, the computation load and time consumption of the algorithm decreased over 50% by the improved algorithm. The work has special significance for navigation applications that request low power consumption and strict real-time response, such as cellphone, wearable devices, and deeply coupled GNSS/INS systems.

Contribution of BeiDou satellite system for long baseline GNSS measurement in Indonesia

Science.gov (United States)

Gumilar, I.; Bramanto, B.; Kuntjoro, W.; Abidin, H. Z.; Trihantoro, N. F.

2018-05-01

The demand for more precise positioning method using GNSS (Global Navigation Satellite System) in Indonesia continue to rise. The accuracy of GNSS positioning depends on the length of baseline and the distribution of observed satellites. BeiDou Navigation Satellite System (BDS) is a positioning system owned by China that operating in Asia-Pacific region, including Indonesia. This research aims to find out the contribution of BDS in increasing the accuracy of long baseline static positioning in Indonesia. The contributions are assessed by comparing the accuracy of measurement using only GPS (Global Positioning System) and measurement using the combination of GPS and BDS. The data used is 5 days of GPS and BDS measurement data for baseline with 120 km in length. The software used is open-source RTKLIB and commercial software Compass Solution. This research will explain in detail the contribution of BDS to the accuracy of position in long baseline static GNSS measurement.

Distributed Arithmetic for Efficient Base-Band Processing in Real-Time GNSS Software Receivers

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Grégoire Waelchli

2010-01-01

Full Text Available The growing market of GNSS capable mobile devices is driving the interest of GNSS software solutions, as they can share many system resources (processor, memory, reducing both the size and the cost of their integration. Indeed, with the increasing performance of modern processors, it becomes now feasible to implement in software a multichannel GNSS receiver operating in real time. However, a major issue with this approach is the large computing resources required for the base-band processing, in particular for the correlation operations. Therefore, new algorithms need to be developed in order to reduce the overall complexity of the receiver architecture. Towards that aim, this paper first introduces the challenges of the software implementation of a GPS receiver, with a main focus given to the base-band processing and correlation operations. It then describes the already existing solutions and, from this, introduces a new algorithm based on distributed arithmetic.

Mutations in domain II of 23 S rRNA facilitate translation of a 23 S rRNA-encoded pentapeptide conferring erythromycin resistance

DEFF Research Database (Denmark)

Dam, M; Douthwaite, S; Tenson, T

1996-01-01

Mutations in domain II of Escherichia coli 23 S rRNA that cause resistance to erythromycin do so in a manner fundamentally different from mutations at the drug binding site in domain V of the 23 S rRNA. The domain II mutations are located in a hairpin structure between nucleotides 1198 and 1247...... this hypothesis, a range of point mutations was generated in domain II of 23 S rRNA in the vicinity of the E-peptide open reading frame. We find a correlation between erythromycin resistance of the mutant clones and increased accessibility of the ribosome binding site of the E-peptide gene. Furthermore......, the erythromycin resistance determinant in the mutants was shown to be confined to a small 23 S rRNA segment containing the coding region and the ribosome binding site of the E-peptide open reading frame. It thus appears that the domain II mutations mediate erythromycin resistance by increasing expression...

A procedure for the significance testing of unmodeled errors in GNSS observations

Science.gov (United States)

Li, Bofeng; Zhang, Zhetao; Shen, Yunzhong; Yang, Ling

2018-01-01

It is a crucial task to establish a precise mathematical model for global navigation satellite system (GNSS) observations in precise positioning. Due to the spatiotemporal complexity of, and limited knowledge on, systematic errors in GNSS observations, some residual systematic errors would inevitably remain even after corrected with empirical model and parameterization. These residual systematic errors are referred to as unmodeled errors. However, most of the existing studies mainly focus on handling the systematic errors that can be properly modeled and then simply ignore the unmodeled errors that may actually exist. To further improve the accuracy and reliability of GNSS applications, such unmodeled errors must be handled especially when they are significant. Therefore, a very first question is how to statistically validate the significance of unmodeled errors. In this research, we will propose a procedure to examine the significance of these unmodeled errors by the combined use of the hypothesis tests. With this testing procedure, three components of unmodeled errors, i.e., the nonstationary signal, stationary signal and white noise, are identified. The procedure is tested by using simulated data and real BeiDou datasets with varying error sources. The results show that the unmodeled errors can be discriminated by our procedure with approximately 90% confidence. The efficiency of the proposed procedure is further reassured by applying the time-domain Allan variance analysis and frequency-domain fast Fourier transform. In summary, the spatiotemporally correlated unmodeled errors are commonly existent in GNSS observations and mainly governed by the residual atmospheric biases and multipath. Their patterns may also be impacted by the receiver.

EPOS-IP WP10: services and data provision for the GNSS community

Science.gov (United States)

Fernandes, Rui

2016-04-01

The EPOS-IP WP10 - "GNSS Data & Products" is the Working Package of the EPOS-IP project in charge of implementing the necessary services in order that the geo-sciences community can access the existing Pan-European Geodetic Infrastructures. The WP10 is formed by representatives of the participating institutions (10) but it is also open to the entire geodetic community. In fact, WP10 also includes members from other institutions/countries that formally are not participating in the EPOS-IP. During the EPOS-IP project, the geodetic component of EPOS (WP10) is dealing essentially with Research Infrastructures focused on continuous operating GNSS (cGNSS). The option of concentrating the efforts on the presently most generalized geodetic tool supporting research on Solid Earth was decided in order to optimize the existing resources. Furthermore, although the focus is on Solid Earth applications, other research and technical applications (e.g., reference frames, meteorology, space weather) can also benefit from the efforts of WP10 towards the optimization of the geodetic resources in Europe. We will present and discuss the plans for the implementation of the thematic and core services (TCS) for GNSS data within EPOS and the related business plan. We will focus on strategies towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the geodetic data, derived solutions, and associated metadata using transparent and uniform processes. The collaboration with EUREF is also an essential component of the implementation plan.

Integration of Kinect and Low-Cost Gnss for Outdoor Navigation

Science.gov (United States)

Pagliaria, D.; Pinto, L.; Reguzzoni, M.; Rossi, L.

2016-06-01

Since its launch on the market, Microsoft Kinect sensor has represented a great revolution in the field of low cost navigation, especially for indoor robotic applications. In fact, this system is endowed with a depth camera, as well as a visual RGB camera, at a cost of about 200. The characteristics and the potentiality of the Kinect sensor have been widely studied for indoor applications. The second generation of this sensor has been announced to be capable of acquiring data even outdoors, under direct sunlight. The task of navigating passing from an indoor to an outdoor environment (and vice versa) is very demanding because the sensors that work properly in one environment are typically unsuitable in the other one. In this sense the Kinect could represent an interesting device allowing bridging the navigation solution between outdoor and indoor. In this work the accuracy and the field of application of the new generation of Kinect sensor have been tested outdoor, considering different lighting conditions and the reflective properties of the emitted ray on different materials. Moreover, an integrated system with a low cost GNSS receiver has been studied, with the aim of taking advantage of the GNSS positioning when the satellite visibility conditions are good enough. A kinematic test has been performed outdoor by using a Kinect sensor and a GNSS receiver and it is here presented.

Design of GNSS Performance Analysis and Simulation Tools as a Web Portal

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S. Tadic

2014-11-01

Full Text Available This paper considers design of a web-portal for the validation of behavior of GNSS applications in different environments. The tool provides the positioning performance analysis and a comparison to benchmark devices. Web-portal incorporates a 3D synthetic data generator to compute the propagation and the reception of radio-navigation signals in a 3D virtual environment. This radio propagation simulator uses ray-tracing to calculate interactions between the GNSS signal and the local environment. For faster execution on a GPU platform, the simulator uses BVH optimization. The work is verified in field trials and by using reference software.

GNSS global navigation satellite systems : GPS, GLONASS, Galileo, and more

CERN Document Server

Hofmann-Wellenhof, Bernhard; Wasle, Elmar

2008-01-01

This book is an extension to the acclaimed scientific bestseller "GPS - Theory and Practice". It covers Global Navigation Satellite Systems (GNSS) and includes the Russian GLONASS, the European system Galileo, and additional systems.

The study of key issues about integration of GNSS and strong-motion records for real-time earthquake monitoring

Science.gov (United States)

Tu, Rui; Zhang, Pengfei; Zhang, Rui; Liu, Jinhai

2016-08-01

This paper has studied the key issues about integration of GNSS and strong-motion records for real-time earthquake monitoring. The validations show that the consistence of the coordinate system must be considered firstly to exclude the system bias between GNSS and strong-motion. The GNSS sampling rate is suggested about 1-5 Hz, and we should give the strong-motion's baseline shift with a larger dynamic noise as its variation is very swift. The initialization time of solving the baseline shift is less than one minute, and ambiguity resolution strategy is not greatly improved the solution. The data quality is very important for the solution, we advised to use multi-frequency and multi-system observations. These ideas give an important guide for real-time earthquake monitoring and early warning by the tight integration of GNSS and strong-motion records.

Validation and Assessment of Multi-GNSS Real-Time Precise Point Positioning in Simulated Kinematic Mode Using IGS Real-Time Service

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Liang Wang

2018-02-01

Full Text Available Precise Point Positioning (PPP is a popular technology for precise applications based on the Global Navigation Satellite System (GNSS. Multi-GNSS combined PPP has become a hot topic in recent years with the development of multiple GNSSs. Meanwhile, with the operation of the real-time service (RTS of the International GNSS Service (IGS agency that provides satellite orbit and clock corrections to broadcast ephemeris, it is possible to obtain the real-time precise products of satellite orbits and clocks and to conduct real-time PPP. In this contribution, the real-time multi-GNSS orbit and clock corrections of the CLK93 product are applied for real-time multi-GNSS PPP processing, and its orbit and clock qualities are investigated, first with a seven-day experiment by comparing them with the final multi-GNSS precise product ‘GBM’ from GFZ. Then, an experiment involving real-time PPP processing for three stations in the Multi-GNSS Experiment (MGEX network with a testing period of two weeks is conducted in order to evaluate the convergence performance of real-time PPP in a simulated kinematic mode. The experimental result shows that real-time PPP can achieve a convergence performance of less than 15 min for an accuracy level of 20 cm. Finally, the real-time data streams from 12 globally distributed IGS/MGEX stations for one month are used to assess and validate the positioning accuracy of real-time multi-GNSS PPP. The results show that the simulated kinematic positioning accuracy achieved by real-time PPP on different stations is about 3.0 to 4.0 cm for the horizontal direction and 5.0 to 7.0 cm for the three-dimensional (3D direction.

Can space ties on board GNSS satellites replace terrestrial ties in the implementation of Terrestrial Reference Frames?

Science.gov (United States)

Bruni, Sara; Zerbini, Susanna; Altamimi, Zuheir; Rebischung, Paul; Errico, Maddalena; Santi, Efisio

2016-04-01

The realization of Terrestrial Reference Frames (TRFs) must be periodically updated in order to account for newly acquired observations and for upgrades in data analysis procedures and/or combination techniques. Any innovative computation strategy should ameliorate the definition of the frame physical parameters, upon which a number of scientific applications critically rely. On the basis of the requirements of scientific cutting edge studies, the geodetic community has estimated that the present day challenge in the determination of TRFs is to provide a frame that is accurate and long-term stable at the level of 1 mm and 0.1 mm/y respectively. This work aims at characterizing the frame realized by a combination of Satellite Laser Ranging (SLR) and Global Navigation Satellite Systems (GNSS) observations via their co-location on board GNSS spacecrafts. In particular, it is established how such a frame compares to the traditional ITRF computation and what is the impact on the realization of the frame origin and scale. Four years of data from a global network encompassing about one hundred GNSS stations and all SLR sites have been analyzed. In order to ensure the highest possible consistency, the raw data of both techniques are treated with the same analysis Software (Bernese GNSS Software 5.2) following IERS2010 Conventions. Both weekly and long term solutions are carried out exploiting either the Bernese or the Combination and Analysis of Terrestrial Reference Frames (CATREF) Software packages. We present the results of a combination study involving GNSS data and SLR observations to the two LAGEOS and to the GNSS satellites equipped with retroreflector arrays. The latter type of measurements is currently not included in the computation of the official ITRF solutions. The assessment of the benefit that they could provide to the definition of the origin and scale of the ITRF is however worth investigating, as such data provide the potential for linking the GNSS and

Precise GNSS Positioning Using Smart Devices

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Eugenio Realini

2017-10-01

Full Text Available The recent access to GNSS (Global Navigation Satellite System phase observations on smart devices, enabled by Google through its Android operating system, opens the possibility to apply precise positioning techniques using off-the-shelf, mass-market devices. The target of this work is to evaluate whether this is feasible, and which positioning accuracy can be achieved by relative positioning of the smart device with respect to a base station. Positioning of a Google/HTC Nexus 9 tablet was performed by means of batch least-squares adjustment of L1 phase double-differenced observations, using the open source goGPS software, over baselines ranging from approximately 10 m to 8 km, with respect to both physical (geodetic or low-cost and virtual base stations. The same positioning procedure was applied also to a co-located u-blox low-cost receiver, to compare the performance between the receiver and antenna embedded in the Nexus 9 and a standard low-cost single-frequency receiver with external patch antenna. The results demonstrate that with a smart device providing raw GNSS phase observations, like the Nexus 9, it is possible to reach decimeter-level accuracy through rapid-static surveys, without phase ambiguity resolution. It is expected that sub-centimeter accuracy could be achieved, as demonstrated for the u-blox case, if integer phase ambiguities were correctly resolved.

Precise GNSS Positioning Using Smart Devices.

Science.gov (United States)

Realini, Eugenio; Caldera, Stefano; Pertusini, Lisa; Sampietro, Daniele

2017-10-24

The recent access to GNSS (Global Navigation Satellite System) phase observations on smart devices, enabled by Google through its Android operating system, opens the possibility to apply precise positioning techniques using off-the-shelf, mass-market devices. The target of this work is to evaluate whether this is feasible, and which positioning accuracy can be achieved by relative positioning of the smart device with respect to a base station. Positioning of a Google/HTC Nexus 9 tablet was performed by means of batch least-squares adjustment of L1 phase double-differenced observations, using the open source goGPS software, over baselines ranging from approximately 10 m to 8 km, with respect to both physical (geodetic or low-cost) and virtual base stations. The same positioning procedure was applied also to a co-located u-blox low-cost receiver, to compare the performance between the receiver and antenna embedded in the Nexus 9 and a standard low-cost single-frequency receiver with external patch antenna. The results demonstrate that with a smart device providing raw GNSS phase observations, like the Nexus 9, it is possible to reach decimeter-level accuracy through rapid-static surveys, without phase ambiguity resolution. It is expected that sub-centimeter accuracy could be achieved, as demonstrated for the u-blox case, if integer phase ambiguities were correctly resolved.

GEROS-ISS: GNSS REflectometry, Radio Occultation and Scatterometry onboard the International Space Station

DEFF Research Database (Denmark)

Wickert, Jens; Cardellach, Estel; Bandeiras, Jorge

2016-01-01

GEROS-ISS stands for GNSS REflectometry, radio occultation, and scatterometry onboard the International Space Station (ISS). It is a scientific experiment, successfully proposed to the European Space Agency in 2011. The experiment as the name indicates will be conducted on the ISS. The main focus...... of GEROS-ISS is the dedicated use of signals from the currently available Global Navigation Satellite Systems (GNSS) in L-band for remote sensing of the Earth with a focus to study climate change. Prime mission objectives are the determination of the altimetric sea surface height of the oceans...

Multi-GNSS orbit determination using satellite laser ranging

Science.gov (United States)

Bury, Grzegorz; Sośnica, Krzysztof; Zajdel, Radosław

2018-04-01

Galileo, BeiDou, QZSS, and NavIC are emerging global navigation satellite systems (GNSSs) and regional navigation satellite systems all of which are equipped with laser retroreflector arrays for range measurements. This paper summarizes the GNSS-intensive tracking campaigns conducted by the International Laser Ranging Service and provides results from multi-GNSS orbit determination using solely SLR observations. We consider the whole constellation of GLONASS, all active Galileo, four BeiDou satellites: 1 MEO, 3 IGSO, and one QZSS. We analyze the influence of the number of SLR observations on the quality of the 3-day multi-GNSS orbit solution. About 60 SLR observations are needed for obtaining MEO orbits of sufficient quality with the root mean square (RMS) of 3 cm for the radial component when compared to microwave-based orbits. From the analysis of a minimum number of tracking stations, when considering the 3-day arcs, 5 SLR stations do not provide a sufficient geometry of observations. The solution obtained using ten stations is characterized with RMS of 4, 9, and 18 cm in the radial, along-track, and cross-track direction, respectively, for MEO satellites. We also investigate the impact of the length of orbital arc on the quality of SLR-derived orbits. Hence, 5- and 7-day arcs constitute the best solution, whereas 3-day arcs are of inferior quality due to an insufficient number of SLR observations and 9-day arcs deteriorate the along-track component. The median RMS from the comparison between 7-day orbital arcs determined using SLR data with microwave-based orbits assumes values in the range of 3-4, 11-16, and 15-27 cm in radial, along-track, and cross-track, respectively, for MEO satellites. BeiDou IGSO and QZSS are characterized by RMS values higher by a factor of 8 and 24, respectively, than MEO orbits.

3D-RTK Capability of Single Gnss Receivers

Science.gov (United States)

Stempfhuber, W.

2013-08-01

Small, aerial objects are now being utilised in many areas of civil object capture and monitoring. As a rule, the standard application of a simple GPS receiver with code solutions serves the 3D-positioning of the trajectories or recording positions. Without GPS correction information, these can be calculated at an accuracy of 10-20 metres. Corrected code solutions (DGPS) generally lie in the metre range. A precise 3D-positioning of the UAV (unmanned aerial vehicle) trajectories in the centimetre range provides significant improvements. In addition, the recording time of each sensor can be synchronized with the exact time stamp of the GNSS low-cost system. In recent years, increasing works on positioning from L1 GPS raw data have been published. Along with this, the carrier phase measurements with the established evaluation algorithms are analysed in the post processing method to centimetre-exact positions or to high-precision 3D trajectories [e.g. Schwieger and Gläser, 2005 or Korth and Hofmann 20011]. The use of reference information from local reference stations or a reference network serves the purpose of carrier phase ambiguity resolution. Furthermore, there are many activities worldwide in the area of PPP techniques (Precise Point Positioning). However, dual frequency receivers are primarily used in this instance. Moreover, very long initialisation times must be scheduled for this. A research project on the subject of low-cost RTK GNSS was developed for real-time applications at the Beuth Hochschule für Technik Berlin University of Applied Sciences [Stempfhuber 2012]. The overall system developed for the purpose of real-time applications with centimetre accuracy is modularly constructed and can be used for various applications (http://prof.beuthhochschule.de/stempfhuber/seite-publikation/). With hardware costing a few hundred Euro and a total weight of 500-800 g (including the battery), this system is ideally suited for UAV applications. In addition, the

E-st@r-I experience: Valuable knowledge for improving the e-st@r-II design

Science.gov (United States)

Corpino, S.; Obiols-Rabasa, G.; Mozzillo, R.; Nichele, F.

2016-04-01

Many universities all over the world have now established hands-on education programs based on CubeSats. These small and cheap platforms are becoming more and more attractive also for other-than-educational missions, such as technology demonstration, science applications, and Earth observation. This new paradigm requires the development of adequate technology to increase CubeSat performance and mission reliability, because educationally-driven missions have often failed. In 2013 the ESA Education Office launched the Fly Your Satellite! Programme which aims at increasing CubeSat mission reliability through several actions: to improve design implementation, to define best practices for conducting the verification process, and to make the CubeSat community aware of the importance of verification. Within this framework, the CubeSat team at Politecnico di Torino developed the e-st@r-II CubeSat as follow-on of the e-st@r-I satellite, launched in 2012 on the VEGA Maiden Flight. E-st@r-I and e-st@r-II are both 1U satellites with educational and technology demonstration objectives: to give hands-on experience to university students and to test an active attitude determination and control system based on inertial and magnetic measurements with magnetic actuation. This paper describes the know-how gained thanks to the e-st@r-I mission, and how this heritage has been translated into the improvement of the new CubeSat in several areas and lifecycle phases. The CubeSat design has been reviewed to reduce the complexity of the assembly procedure and to deal with possible failures of the on-board computer, for example re-coding the software in the communications subsystem. New procedures have been designed and assessed for the verification campaign accordingly to ECSS rules and with the support of ESA specialists. Different operative modes have been implemented to handle some anomalies observed during the operations of the first satellite. A new version of the on-board software is

Noise Characteristics of High-Rate Multi-GNSS for Subdaily Crustal Deformation Monitoring

Science.gov (United States)

Geng, Jianghui; Pan, Yuanxin; Li, Xiaotao; Guo, Jiang; Liu, Jingnan; Chen, Xianchun; Zhang, Yong

2018-02-01

High-rate GPS (Global Positioning System) has the potential to record crustal motions on a wide subdaily timescale from seconds to hours but usually fails to capture subtle deformations which are often overwhelmed by the centimeter noise of epoch-wise GPS displacements. We hence investigated high-rate multi-GNSS (Global Navigation Satellite System) by processing 1 Hz GPS/GLONASS/BeiDou data at 15 static stations over 24 days and also those from the 8 August 2017 Jiuzhaigou Mw 6.5 earthquake. In contrast to high-rate GPS, its further integration with GLONASS/BeiDou reduces near uniformly the power spectral densities (PSDs) of 1 Hz displacement noise by 4-6 dB over the periods from a few seconds to half of a day, and orbital repeat time (ORT) filtering on all GNSS further again leads to a 2 more decibel decline of the PSDs over the periods of a few tens of seconds to minutes. BeiDou ORT filtering, however, takes effect mainly on the periods of over 2,000 s due to the high altitudes of Inclined Geosynchronous Satellite Orbiters/Geosynchronous Earth Orbiters. Multi-GNSS integration is on average as effective as GPS ORT filtering in reducing PSDs for the periods of a few tens of seconds to minutes while desirably can further decrease the PSDs on almost all other periods by 3-4 dB thanks to the enhanced satellite geometry. We conclude that the introduction of more GNSS into high-rate solutions and its augmentation by ORT filtering benefit the discrimination of slight deformations over a broad subdaily frequency band.

GNSS Wave Glider: First results from Loch Ness and demonstration of its suitability for determining the marine geoid

Science.gov (United States)

Penna, N. T.; Morales Maqueda, M.; Williams, S. D.; Foden, P.; Martin, I.; Pugh, J.

2013-12-01

We report on a first deployment of a GNSS Wave Glider designed for precise, unmanned, autonomous, mobile self-propelled sea level and sea state measurement in the open ocean. The Wave Glider, equipped with a dual frequency GPS+GLONASS receiver, was deployed in Loch Ness, Scotland, autonomously travelling 32 km in a north-easterly direction along the length of the loch in 26 hours, propelled by energy generated from waves of typical amplitude only 100-150 mm and frequency on the order 0.5-1 Hz. The Wave Glider GNSS data were analysed using a post-processed kinematic GPS+GLONASS precise point positioning (PPP) approach, which were quality controlled using double difference GPS kinematic processing with respect to onshore reference stations at either end of the loch. The PPP heights of the loch's surface revealed a clear geoid gradient of about 30 mm/km (i.e. just under 1 m over the whole length of the loch), very similar to both the EGM2008 and OSGM02 geoid models, demonstrating the potential use of a GNSS Wave Glider for marine geoid determination. After applying a low pass filter, the GNSS heights showed local deviations from both EGM2008 and OSGM02, potentially caused by omission errors or a lack of gravity data over Loch Ness. In addition to dual frequency GNSS data, the Wave Glider also recorded inclinometer data, bathymetry, and surface currents, which, in combination with tide gauge and wind data, were used to further control and interpret the GNSS time series.

Mitigation of multipath effect in GNSS short baseline positioning by the multipath hemispherical map

Science.gov (United States)

Dong, D.; Wang, M.; Chen, W.; Zeng, Z.; Song, L.; Zhang, Q.; Cai, M.; Cheng, Y.; Lv, J.

2016-03-01

Multipath is one major error source in high-accuracy GNSS positioning. Various hardware and software approaches are developed to mitigate the multipath effect. Among them the MHM (multipath hemispherical map) and sidereal filtering (SF)/advanced SF (ASF) approaches utilize the spatiotemporal repeatability of multipath effect under static environment, hence they can be implemented to generate multipath correction model for real-time GNSS data processing. We focus on the spatial-temporal repeatability-based MHM and SF/ASF approaches and compare their performances for multipath reduction. Comparisons indicate that both MHM and ASF approaches perform well with residual variance reduction (50 %) for short span (next 5 days) and maintains roughly 45 % reduction level for longer span (next 6-25 days). The ASF model is more suitable for high frequency multipath reduction, such as high-rate GNSS applications. The MHM model is easier to implement for real-time multipath mitigation when the overall multipath regime is medium to low frequency.

A comparison of methods to estimate vertical land motion trends from GNSS and altimetry at tide gauge stations

NARCIS (Netherlands)

Kleinherenbrink, M.; Riva, R.E.M.; Frederikse, T.

2018-01-01

Tide gauge (TG) records are affected by vertical land motion (VLM), causing them to observe relative instead of geocentric sea level. VLM can be estimated from global navigation satellite system (GNSS) time series, but only a few TGs are equipped with a GNSS receiver. Hence, (multiple)

The GNSS data processing component within the Indonesian tsunami early warning centre provided by GITEWS

Science.gov (United States)

Bartsch, M.; Merx, A.; Falck, C.; Ramatschi, M.

2010-05-01

Introduction Within the GITEWS (German Indonesian Tsunami Early Warning System) project a near real-time GNSS processing system has been developed, which analizes on- and offshore measured GNSS data. It is the first system of its kind that was integrated into an operational tsunami early warning system. (Indonesian Tsunami Early Warning Centre INATEWS, inaugurated at BMKG Jakarta on November, 11th 2008) Brief system description The GNSS data to be processed are received from sensors (GNSS antenna and receiver) installed on buoys, at tide gauges and as real-time reference stations (RTR stations), either stand-alone or co-located with seismic sensors. The GNSS data are transmitted to the warning centre in real-time as a stream (RTR stations) or file-based and are processed in a near real-time data processing chain. The fully automatized system uses the BERNESE GPS software as processing core. Kinematic coordinate timeseries with a resolution of 1 Hz (landbased stations) and 1/3 Hz (buoys) are estimated every five minutes. In case of a recently occured earthquake the processing interval decreases from five to two minutes. All stations are processed with the relative technique (baseline-technique) using GITEWS-stations and stations available via IGS as reference. The most suitable reference stations are choosen by querying a database where continiously monitored quality data of GNSS observations are stored. In case of an earthquake at least one reference station should be located on a different tectonic plate to ensure that relative movements can be detected. The primary source for satellite orbit information is the IGS IGU product. If this source is not available for any reason, the system switches automatically to other orbit sources like CODE products or broadcast ephemeris data. For sensors on land the kinematic coordinates are used to detect deviations from their normal, mean coordinates. The deviations or so called displacements are indicators for land mass

Evaluation of Low-Cost, Centimeter-Level Accuracy OEM GNSS Receivers

Science.gov (United States)

2018-02-02

This report discusses the results of a study to quantify the performance of low-cost, centimeter-level accurate Global Navigation Satellite Systems (GNSS) receivers that have appeared on the market in the last few years. Centimeter-level accuracy is ...

Comparison of total water vapour content in the Arctic derived from GNSS, AIRS, MODIS and SCIAMACHY

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Alraddawi, Dunya; Sarkissian, Alain; Keckhut, Philippe; Bock, Olivier; Noël, Stefan; Bekki, Slimane; Irbah, Abdenour; Meftah, Mustapha; Claud, Chantal

2018-05-01

Atmospheric water vapour plays a key role in the Arctic radiation budget, hydrological cycle and hence climate, but its measurement with high accuracy remains an important challenge. Total column water vapour (TCWV) datasets derived from ground-based GNSS measurements are used to assess the quality of different existing satellite TCWV datasets, namely from the Moderate Resolution Imaging Spectroradiometer (MODIS), the Atmospheric Infrared Sounder (AIRS) and the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY). The comparisons between GNSS and satellite data are carried out for three reference Arctic observation sites (Sodankylä, Ny-Ålesund and Thule) where long homogeneous GNSS time series of more than a decade (2001-2014) are available. We select hourly GNSS data that are coincident with overpasses of the different satellites over the three sites and then average them into monthly means that are compared with monthly mean satellite products for different seasons. The agreement between GNSS and satellite time series is generally within 5 % at all sites for most conditions. The weakest correlations are found during summer. Among all the satellite data, AIRS shows the best agreement with GNSS time series, though AIRS TCWV is often slightly too high in drier atmospheres (i.e. high-latitude stations during autumn and winter). SCIAMACHY TCWV data are generally drier than GNSS measurements at all the stations during the summer. This study suggests that these biases are associated with cloud cover, especially at Ny-Ålesund and Thule. The dry biases of MODIS and SCIAMACHY observations are most pronounced at Sodankylä during the snow season (from October to March). Regarding SCIAMACHY, this bias is possibly linked to the fact that the SCIAMACHY TCWV retrieval does not take accurately into account the variations in surface albedo, notably in the presence of snow with a nearby canopy as in Sodankylä. The MODIS bias at Sodankylä is found

Cloning and primary immunological study of TGF-β1 and its receptors TβR I /TβR II in tilapia(Oreochromis niloticus).

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Zhan, Xu-liang; Ma, Tai-yang; Wu, Jin-ying; Yi, Li-yuan; Wang, Jing-yuan; Gao, Xiao-ke; Li, Wen-sheng

2015-07-01

The transforming growth factor β (TGF-β) superfamily plays critical roles in tumor suppression, cell proliferation and differentiation, tissue morphogenesis, lineage determination, cell migration and apoptosis. Recently, TGF-β1, one important member of TGF-β superfamily, is suggested as an immune regulator in the teleost. In this study, we cloned the cDNAs of TGF-β1 and its receptors, TβR I and TβR II (including three isoforms) from tilapia (Genbank accession numbers: KP754231- KP754235). A tissue distribution profile analysis indicated that TGF-β1 was highly expressed in the head kidney, gill, spleen, kidney and PBLs (peripheral blood leukocytes); TβR I only showed considerable expression in the liver; and TβR II-2 was highly expressed in the kidney, gill, liver, head kidney and heart. We determined that the mRNA expressions of TGF-β and TβR I /TβR II-2 were significantly increased in tilapia head kidney and spleen leukocytes by the stimulation of Lipopolysaccharide (LPS) or Poly I: C. We also examined their expressions in the spleen and head kidney of tilapia after IP injection of streptococcus agalactiae. The results showed that the mRNA expressions of these three genes all increased in the head kidney as early as 6 h post infection, and in the spleen 3 d post infection. In addition, the protein level of TGF-β1 was also up-regulated in the head kidney and the spleen after infection. Taken together, our data indicate that the TGF-β1-TβR I /TβR II-2 system functions potentially in tilapia immune system. Copyright © 2015 Elsevier Ltd. All rights reserved.

Rotation Matrix Method Based on Ambiguity Function for GNSS Attitude Determination.

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Yang, Yingdong; Mao, Xuchu; Tian, Weifeng

2016-06-08

Global navigation satellite systems (GNSS) are well suited for attitude determination. In this study, we use the rotation matrix method to resolve the attitude angle. This method achieves better performance in reducing computational complexity and selecting satellites. The condition of the baseline length is combined with the ambiguity function method (AFM) to search for integer ambiguity, and it is validated in reducing the span of candidates. The noise error is always the key factor to the success rate. It is closely related to the satellite geometry model. In contrast to the AFM, the LAMBDA (Least-squares AMBiguity Decorrelation Adjustment) method gets better results in solving the relationship of the geometric model and the noise error. Although the AFM is more flexible, it is lack of analysis on this aspect. In this study, the influence of the satellite geometry model on the success rate is analyzed in detail. The computation error and the noise error are effectively treated. Not only is the flexibility of the AFM inherited, but the success rate is also increased. An experiment is conducted in a selected campus, and the performance is proved to be effective. Our results are based on simulated and real-time GNSS data and are applied on single-frequency processing, which is known as one of the challenging case of GNSS attitude determination.

Rotation Matrix Method Based on Ambiguity Function for GNSS Attitude Determination

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Yingdong Yang

2016-06-01

Full Text Available Global navigation satellite systems (GNSS are well suited for attitude determination. In this study, we use the rotation matrix method to resolve the attitude angle. This method achieves better performance in reducing computational complexity and selecting satellites. The condition of the baseline length is combined with the ambiguity function method (AFM to search for integer ambiguity, and it is validated in reducing the span of candidates. The noise error is always the key factor to the success rate. It is closely related to the satellite geometry model. In contrast to the AFM, the LAMBDA (Least-squares AMBiguity Decorrelation Adjustment method gets better results in solving the relationship of the geometric model and the noise error. Although the AFM is more flexible, it is lack of analysis on this aspect. In this study, the influence of the satellite geometry model on the success rate is analyzed in detail. The computation error and the noise error are effectively treated. Not only is the flexibility of the AFM inherited, but the success rate is also increased. An experiment is conducted in a selected campus, and the performance is proved to be effective. Our results are based on simulated and real-time GNSS data and are applied on single-frequency processing, which is known as one of the challenging case of GNSS attitude determination.

Angiotensin II reduces cardiac AdipoR1 expression through AT1 receptor/ROS/ERK1/2/c-Myc pathway.

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Li Li

Full Text Available Adiponectin, an abundant adipose tissue-derived protein, exerts protective effect against cardiovascular disease. Adiponectin receptors (AdipoR1 and AdipoR2 mediate the beneficial effects of adiponectin on the cardiovascular system. However, the alteration of AdipoRs in cardiac remodeling is not fully elucidated. Here, we investigated the effect of angiotensin II (AngII on cardiac AdipoRs expression and explored the possible molecular mechanism. AngII infusion into rats induced cardiac hypertrophy, reduced AdipoR1 but not AdipoR2 expression, and attenuated the phosphorylations of adenosine monophosphate-activated protein kinase and acetyl coenzyme A carboxylase, and those effects were all reversed by losartan, an AngII type 1 (AT1 receptor blocker. AngII reduced expression of AdipoR1 mRNA and protein in cultured neonatal rat cardiomyocytes, which was abolished by losartan, but not by PD123319, an AT2 receptor antagonist. The antioxidants including reactive oxygen species (ROS scavenger NAC, NADPH oxidase inhibitor apocynin, Nox2 inhibitor peptide gp91 ds-tat, and mitochondrial electron transport chain complex I inhibitor rotenone attenuated AngII-induced production of ROS and phosphorylation of extracellular signal-regulated kinase (ERK 1/2. AngII-reduced AdipoR1 expression was reversed by pretreatment with NAC, apocynin, gp91 ds-tat, rotenone, and an ERK1/2 inhibitor PD98059. Chromatin immunoprecipitation assay demonstrated that AngII provoked the recruitment of c-Myc onto the promoter region of AdipoR1, which was attenuated by PD98059. Moreover, AngII-induced DNA binding activity of c-Myc was inhibited by losartan, NAC, apocynin, gp91 ds-tat, rotenone, and PD98059. c-Myc small interfering RNA abolished the inhibitory effect of AngII on AdipoR1 expression. Our results suggest that AngII inhibits cardiac AdipoR1 expression in vivo and in vitro and AT1 receptor/ROS/ERK1/2/c-Myc pathway is required for the downregulation of AdipoR1 induced by AngII.

GNSS-SLR satellite co-location for the estimate of local ties

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Bruni, Sara; Zerbini, Susanna; Errico, Maddalena; Santi, Efisio

2013-04-01

The current realization of the International Terrestrial Reference Frame (ITRF) is based on four different space-geodetic techniques, so that the benefits brought by each observing system to the definition of the frame can compensate for the drawbacks of the others and technique-specific systematic errors might be identified. The strategy used to combine the observations from the different techniques is then of prominent importance for the realization of a precise and stable reference frame. This study concentrates, in particular, on the combination of Satellite Laser Ranging (SLR) and Global Navigation Satellite System (GNSS) observations by exploiting satellite co-locations. This innovative approach is based on the fact that laser tracking of GNSS satellites, carrying on board laser reflector arrays, allows for the combination of optical and microwave signals in the determination of the spacecraft orbit. Besides, the use of satellite co-locations differs quite significantly from the traditional combination method in which each single technique solution is carried out autonomously and is interrelated in a second step. One of the benefits of the approach adopted in this study is that it allows for an independent validation of the local tie, i.e. of the vector connecting the SLR and GNSS reference points in a multi-techniques station. Typically, local ties are expressed by a single value, measured with ground-based geodetic techniques and taken as constant. In principle, however, local ties might show time variations likely caused by the different monumentation characteristics of the GNSS antennas with respect to those of a SLR system. This study evaluates the possibility of using the satellite co-location approach to generate local-ties time series by means of observations available for a selected network of ILRS stations. The data analyzed in this study were acquired as part of the NASA's Earth Science Data Systems and are archived and distributed by the Crustal

Evaluation of gravity field model EIGEN-6C4 by means of various functions of gravity potential, and by GNSS/levelling

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Jan Kostelecký

2015-06-01

Full Text Available The combined gravity field model EIGEN-6C4 (Förste et al., 2014 is the latest combined global gravity field model of GFZ Potsdam and GRGS Toulouse. EIGEN-6C4 has been generated including the satellite gravity gradiometry data of the entire GOCE mission (November 2009 till October 2013 and is of maximum spherical degree and order 2190. In this study EIGEN-6C4 has been compared with EGM2008 to its maximum degree and order via gravity disturbances and Tzz part of the Marussi tensor of the second derivatives of the disturbing potential. The emphasis is put on such areas where GOCE data (complete set of gradiometry measurements after reductions in EIGEN-6C4 obviously contributes to an improvement of the gravity field description. GNSS/levelling geoid heights are independent data source for the evaluation of gravity field models. Therefore, we use the GNSS/levelling data sets over the territories of Europe, Czech Republic and Slovakia for the evaluation of EIGEN-6C4 w.r.t. EGM2008.

PERFORMANCE ASSESSMENT OF INTEGRATED SENSOR ORIENTATION WITH A LOW-COST GNSS RECEIVER

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M. Rehak

2017-08-01

Full Text Available Mapping with Micro Aerial Vehicles (MAVs whose weight does not exceed 5 kg is gaining importance in applications such as corridor mapping, road and pipeline inspections, or mapping of large areas with homogeneous surface structure, e.g. forest or agricultural fields. In these challenging scenarios, integrated sensor orientation (ISO improves effectiveness and accuracy. Furthermore, in block geometry configurations, this mode of operation allows mapping without ground control points (GCPs. Accurate camera positions are traditionally determined by carrier-phase GNSS (Global Navigation Satellite System positioning. However, such mode of positioning has strong requirements on receiver’s and antenna’s performance. In this article, we present a mapping project in which we employ a single-frequency, low-cost (< $100 GNSS receiver on a MAV. The performance of the low-cost receiver is assessed by comparing its trajectory with a reference trajectory obtained by a survey-grade, multi-frequency GNSS receiver. In addition, the camera positions derived from these two trajectories are used as observations in bundle adjustment (BA projects and mapping accuracy is evaluated at check points (ChP. Several BA scenarios are considered with absolute and relative aerial position control. Additionally, the presented experiments show the possibility of BA to determine a camera-antenna spatial offset, so-called lever-arm.

Study on individual stochastic model of GNSS observations for precise kinematic applications

Science.gov (United States)

Próchniewicz, Dominik; Szpunar, Ryszard

2015-04-01

The proper definition of mathematical positioning model, which is defined by functional and stochastic models, is a prerequisite to obtain the optimal estimation of unknown parameters. Especially important in this definition is realistic modelling of stochastic properties of observations, which are more receiver-dependent and time-varying than deterministic relationships. This is particularly true with respect to precise kinematic applications which are characterized by weakening model strength. In this case, incorrect or simplified definition of stochastic model causes that the performance of ambiguity resolution and accuracy of position estimation can be limited. In this study we investigate the methods of describing the measurement noise of GNSS observations and its impact to derive precise kinematic positioning model. In particular stochastic modelling of individual components of the variance-covariance matrix of observation noise performed using observations from a very short baseline and laboratory GNSS signal generator, is analyzed. Experimental test results indicate that the utilizing the individual stochastic model of observations including elevation dependency and cross-correlation instead of assumption that raw measurements are independent with the same variance improves the performance of ambiguity resolution as well as rover positioning accuracy. This shows that the proposed stochastic assessment method could be a important part in complex calibration procedure of GNSS equipment.

Operational space weather service for GNSS precise positioning

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N. Jakowski

2005-11-01

Full Text Available The ionospheric plasma can significantly influence the propagation of radio waves and the ionospheric disturbances are capable of causing range errors, rapid phase and amplitude fluctuations (radio scintillations of satellite signals that may lead to degradation of the system performance, its accuracy and reliability. The cause of such disturbances should be sought in the processes originating in the Sun. Numerous studies on these phenomena have been already carried out at a broad international level, in order to measure/estimate these space weather induced effects, to forecast them, and to understand and mitigate their impact on present-day technological systems. SWIPPA (Space Weather Impact on Precise Positioning Applications is a pilot project jointly supported by the German Aerospace Centre (DLR and the European Space Agency (ESA. The project aims at establishing, operating, and evaluating a specific space-weather monitoring service that can possibly lead to improving current positioning applications based on Global Navigation Satellite Systems (GNSS. This space weather service provides GNSS users with essential expert information delivered in the form of several products - maps of TEC values, TEC spatial and temporal gradients, alerts for ongoing/oncoming ionosphere disturbances, etc.

Operational space weather service for GNSS precise positioning

Directory of Open Access Journals (Sweden)

N. Jakowski

2005-11-01

Full Text Available The ionospheric plasma can significantly influence the propagation of radio waves and the ionospheric disturbances are capable of causing range errors, rapid phase and amplitude fluctuations (radio scintillations of satellite signals that may lead to degradation of the system performance, its accuracy and reliability. The cause of such disturbances should be sought in the processes originating in the Sun. Numerous studies on these phenomena have been already carried out at a broad international level, in order to measure/estimate these space weather induced effects, to forecast them, and to understand and mitigate their impact on present-day technological systems.

SWIPPA (Space Weather Impact on Precise Positioning Applications is a pilot project jointly supported by the German Aerospace Centre (DLR and the European Space Agency (ESA. The project aims at establishing, operating, and evaluating a specific space-weather monitoring service that can possibly lead to improving current positioning applications based on Global Navigation Satellite Systems (GNSS. This space weather service provides GNSS users with essential expert information delivered in the form of several products - maps of TEC values, TEC spatial and temporal gradients, alerts for ongoing/oncoming ionosphere disturbances, etc.

Improved methods for reprocessing of GNSS data for climate monitoring over Poland

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Stepniak, Katarzyna; Bock, Olivier; Wielgosz, Pawel

2016-04-01

The goal of this work is to determine the most accurate and homogeneous processing strategy to reprocess ground-based GNSS data for climate monitoring applications (analysis of trends and variability of Zenith Total Delay, ZTD, and Integrated Water Vapor, IWV). Namely, we investigate the impact of network design strategy and tropospheric modeling approach on the quality and homogeneity of both relative (double difference) and absolute (PPP) solutions. A network of 138 GNSS stations (including 33 stations from the EUREF Permanent Network, EPN, and 105 stations from ASG-EUPOS in Poland) is reprocessed for year 2014 using Bernese 5.2 GNSS software with the final IGS (International GNSS Service) orbits and clocks. First a standard (the shortest) "star" baseline design strategy is used in which the EPN stations are connected together defining a reference network and every ASG-EUPOS station is connected to the nearest EPN station. The initial network is modified automatically by the Bernese software every day depending on the availability of observations at the EPN stations. We show that in case of sub-daily gaps in the measurements of the reference stations, small clusters of stations can be disconnected from the main reference network. As a result, offsets of a few centimeters in ZTD estimates and spikes in formal errors can appear. These offsets and spikes cannot always be detected. This phenomenon is quite frequent in a large network such as considered in this study. It is also responsible for significant discontinuities in the estimated ZTD series which are detrimental to climate monitoring applications. We developed a new baseline design strategy algorithm to circumvent this event and assure that all the stations remain connected to the main reference network. It is shown that using this strategy, the reprocessed ZTD series are much more continuous and homogeneous in comparison to the standard strategy. The results are further validated against a Precise Point

AVALIAÇÃO DA ACURÁCIA DO CÁLCULO DE VOLUME DE PILHAS DE REJEITO UTILIZANDO VANT, GNSS E LiDAR

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Cristiano Alves da Silva

Full Text Available Dentre as diversas tecnologias utilizadas para cálculo do volume de materiais na mineração, o Veículo Aéreo Não Tripulado (VANT e o Light Detecting And Ranging (LiDAR, surgem como alternativas rápidas e precisas, em comparação com as técnicas de topografia tradicionais como estação total e Global Navigation Satellite System (GNSS. Diante destas novas tecnologias, este estudo avaliou a acurácia do cálculo de volume, realizado por meio de Modelos Digitais de Terreno (MDTs, gerados a partir das tecnologias VANT, LiDAR e GNSS, em uma pilha de rejeito da extração de calcário laminado, explorado para fabricação de lajotas in natura, comercializado com o nome de "Pedra Cariri", no município de Santana do Cariri, no Estado do Ceará. A avaliação da acurácia foi realizada com base no método de testes de hipóteses, a partir da análise de tendência e precisão, sendo os resultados classificados de acordo com o Padrão de Exatidão Cartográfica dos Produtos Cartográficos Digitais (PEC-PCD. Como resultado, o modelo gerado a partir do VANT apresentou a melhor acurácia no cálculo de volume da pilha de rejeito, objeto deste estudo, seguido pela modelagem obtida pelos levantamentos GNSS e LiDAR.

Methods of practice and guidelines for using survey-grade global navigation satellite systems (GNSS) to establish vertical datum in the United States Geological Survey

Science.gov (United States)

Rydlund, Jr., Paul H.; Densmore, Brenda K.

2012-01-01

flexibility regarding efficiency and quality of data collection. Quality assurance of survey-grade global positioning is often overlooked or not understood and perceived uncertainties can be misleading. GNSS users can benefit from a blueprint of data collection standards used to ensure consistency among USGS mission areas. A classification of GNSS survey qualities provide the user with the ability to choose from the highest quality survey used to establish objective points with low uncertainties, identified as a Level I, to a GNSS survey for general topographic control without quality assurance, identified as a Level IV. A Level I survey is strictly limited to post-processed methods, whereas Level II, Level III, and Level IV surveys integrate variations of a RT approach. Among these classifications, techniques involving blunder checks and redundancy are important, and planning that involves the assessment of the overall satellite configuration, as well as terrestrial and space weather, are necessary to ensure an efficient and quality campaign. Although quality indicators and uncertainties are identified in post-processed methods using CORS, the accuracy of a GNSS survey is most effectively expressed as a comparison to a local benchmark that has a high degree of confidence. Real-time and post-processed methods should incorporate these "trusted" benchmarks as a check during any campaign. Global positioning surveys are expected to change rapidly in the future. The expansion of continuously operating reference stations, combined with newly available satellite signals, and enhancements to the conterminous geoid, are all sufficient indicators for substantial growth in real-time positioning and quality thereof.

Precision and accuracy of the static GNSS system for surveying networks used in Civil Engineering

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Nixon Alexander Correa Muñoz

2018-01-01

Full Text Available A field check was implemented for calibrating surveying equipment. It was geo-referenced with a Total Station Theodolite and by implementing procedures concerning repeatability and reproducibility. We carried out GNSS (Global Navigation Satellite System static positioning with double frequency equipment, sensitizing occupation times, day times, uncorrected coordinates subjected to a differential correction procedure and type of coordinates obtained. This facilitated an evaluation of precision and accuracy for the GNSS positioning with the static method, which gave a global RMSE (root mean square error of 1 cm for conditions with no multipath effect and 4 cm for field calibration points close to buildings. Additionally, optimal results for occupation times of 30 minutes were found, and the need to use planar Cartesian coordinates to ensure compatibility with the surveys using electronic measurement of distances, which allows the use of the static GNSS positioning for geo-referencing precise surveying networks, and can be used in different applications in Civil Engineering.

A Multiple-Model Particle Filter Fusion Algorithm for GNSS/DR Slide Error Detection and Compensation

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Rafael Toledo-Moreo

2018-03-01

Full Text Available Continuous accurate positioning is a key element for the deployment of many advanced driver assistance systems (ADAS and autonomous vehicle navigation. To achieve the necessary performance, global navigation satellite systems (GNSS must be combined with other technologies. A common onboard sensor-set that allows keeping the cost low, features the GNSS unit, odometry, and inertial sensors, such as a gyro. Odometry and inertial sensors compensate for GNSS flaws in many situations and, in normal conditions, their errors can be easily characterized, thus making the whole solution not only more accurate but also with more integrity. However, odometers do not behave properly when friction conditions make the tires slide. If not properly considered, the positioning perception will not be sound. This article introduces a hybridization approach that takes into consideration the sliding situations by means of a multiple model particle filter (MMPF. Tests with real datasets show the goodness of the proposal.

Using GNSS-R techniques to investigate the near sub-surface of Mars with the Deep Space Network

Science.gov (United States)

Elliott, H. M.; Bell, D. J.; Jin, C.; Decrossas, E.; Asmar, S.; Lazio, J.; Preston, R. A.; Ruf, C. S.; Renno, N. O.

2017-12-01

Global Navigation Satellite Systems Reflectometry (GNSS-R) has shown that passive measurements using separate active sources can infer the soil moisture, snow pack depth and other quantities of scientific interest. Here, we expand upon this method and propose that a passive measurement of the sub-surface dielectric profile of Mars can be made by using multipath interference between reflections off the surface and subsurface dielectric discontinuities. This measurement has the ability to reveal changes in the soil water content, the depth of a layer of sand, thickness of a layer of ice, and even identify centimeter-scale layering which may indicate the presence of a sedimentary bed. We have created a numerical ray tracing model to understand the potential of using multipath interference techniques to investigate the sub-surface dielectric properties and structure of Mars. We have further verified this model using layered beds of sand and concrete in laboratory experiments and then used the model to extrapolate how this technique may be applied to future Mars missions. We will present new results demonstrating how to characterize a multipath interference patterns as a function of frequency and/or incidence angle to measure the thickness of a dielectric layer of sand or ice. Our results demonstrate that dielectric discontinuities in the subsurface can be measured using this passive sensing technique and it could be used to effectively measure the thickness of a dielectric layer in the proximity of a landed spacecraft. In the case of an orbiter, we believe this technique would be effective at measuring the seasonal thickness of CO2 ice in the Polar Regions. This is exciting because our method can produce similar results to traditional ground penetrating radars without the need to have an active radar transmitter in-situ. Therefore, it is possible that future telecommunications systems can serve as both a radio and a scientific instrument when used in conjunction with

The Behavioural Responses of Beef Cattle (Bos taurus to Declining Pasture Availability and the Use of GNSS Technology to Determine Grazing Preference

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Jaime Manning

2017-05-01

Full Text Available Combining technologies for monitoring spatial behaviour of livestock with technologies that monitor pasture availability, offers the opportunity to improve the management and welfare of extensively produced beef cattle. The aims of the study were to investigate changes to beef cattle behaviour as pasture availability changed, and to determine whether Global Navigation Satellite System (GNSS technology could determine livestock grazing preference and hence improve pasture management and paddock utilisation. Data derived from GNSS collars included distance travelled and location in the paddock. The latter enabled investigation of individual animal interactions with the underlying Normalised Difference Vegetation Index (NDVI and pasture biomass of the paddock. As expected, there was a significant temporal decrease in NDVI during the study and an increase in distance travelled by cattle (P < 0.001; r2 = 0.88. The proportion of time budget occupied in grazing behaviour also increased (P < 0.001; r2 = 0.71. Cattle showed a partial preference for areas of higher pasture biomass/NDVI, although there was a large amount of variation over the course of the study. In conclusion, cattle behaviour changed in response to declining NDVI, highlighting how technologies that monitor these two variables may be used in the future as management tools to assist producers better manage cattle, to manipulate grazing intensity and paddock utilisation.

Recent Korean R&D in Satellite Communications

Science.gov (United States)

Lee, Ho-Jin; Kim, Jae Moung; Lee, Byung-Seub; Lee, Han; Ryoo, Jang-Soo

The R&D in satellite communications in Korea has been driven mainly by KCC (Korea Communications Commission) but in a small scale compared to Korea space development program organized by MEST (Ministry of Education, Science and Technology). Public and civilian satcom sector R&D has been led mainly by ETRI with small/medium companies contrary to rare investment in private sector while military sector R&D has been orchestrated by ADD with defense industry. By the COMS (Communication, Ocean and Meteorological Satellite) experimental Ka-band payload, Korea pursues a space qualification of own technology for national infrastructure evolution as well as industrialization of space R&D results. Once COMS launched and space qualified in 2009, subsequent application experiments and new technology R&D like UHDTV will entail service and industry promotion. The payload technology is expected for the next Korean commercial satellites or for new OBP satellites. The COMS ground control system and GNSS ground station technologies are under development for COMS operation and enhanced GNSS services along with advent of Galileo respectively. Satellite broadband mobile VSAT based on DVB-S2/RCS (+M) and low profile tracking antennas have been developed for trains, ships, and planes. While APSI is developing GMR-1 based Thuraya handset functions, ETRI is designing IMT-Advanced satellite radio interface for satellite and terrestrial dual-mode handheld communication system like Japanese STICS, with universities' satellite OFDM researches. A 21GHz Ka-band higher-availability scalable HD broadcasting technology and SkyLife's hybrid satellite IPTV technology are being developed. In near term Korea will extend R&D programs to upgrade the space communication infrastructure for universal access to digital opportunity and safer daily life from disaster, and to promote space green IT industrialization, national security, and space resources sovereign. Japanese stakeholders are invited to establish

Real-time monitoring for fast deformations using GNSS low-cost receivers

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T. Bellone

2016-03-01

Full Text Available Landslides are one of the major geo-hazards which have constantly affected Italy especially over the last few years. In fact 82% of the Italian territory is affected by this phenomenon which destroys the environment and often causes deaths: therefore it is necessary to monitor these effects in order to detect and prevent these risks. Nowadays, most of this type of monitoring is carried out by using traditional topographic instruments (e.g. total stations or satellite techniques such as global navigation satellite system (GNSS receivers. The level of accuracy obtainable with these instruments is sub-centimetrical in post-processing and centimetrical in real-time; however, the costs are very high (many thousands of euros. The rapid diffusion of GNSS networks has led to an increase of using mass-market receivers for real-time positioning. In this paper, the performances of GNSS mass-market receiver are reported with the aim of verifying if this type of sensor can be used for real-time landslide monitoring: for this purpose a special slide was used for simulating a landslide, since it enabled us to give manual displacements thanks to a micrometre screw. These experiments were also carried out by considering a specific statistical test (a modified Chow test which enabled us to understand if there were any displacements from a statistical point of view in real time. The tests, the algorithm and results are reported in this paper.

Simulation Tool for GNSS Ocean Surface Reflections

DEFF Research Database (Denmark)

Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

2015-01-01

GNSS coherent and incoherent reflected signals have the potential of deriving large scale parameters of ocean surfaces, as barotropic variability, eddy currents and fronts, Rossby waves, coastal upwelling, mean ocean surfaceheights, and patterns of the general ocean circulation. In the reflection...... zone the measurements may deriveparameters as sea surface roughness, winds, waves, heights and tilts from the spectral measurements. Previous measurements from the top of mountains and airplanes have shown such results leading.The coming satellite missions, CYGNSS, COSMIC-2, and GEROS...

DORIS and GNSS processing at CNES/CLS for the contribution to the next ITRF2013

Science.gov (United States)

Loyer, Sylvain; Capdeville, Hugues; Soudarin, Laurent; Mezerette, Adrien; Lemoine, Jean-Michel; Mercier, Flavien; Perosanz, Felix

2014-05-01

CNES serves as Analysis Center in the International DORIS Service (IDS) and the International GNSS Service (IGS). DORIS and GNSS data are processed by its subsidiary CLS with the GRGS package software GINS/DYNAMO. For the contribution to the next release of the International Terrestrial Reference Frame planned this year (ITRF2013), two decades of data were analyzed (1993-2013 for DORIS, 1998-2013 for GPS, and 2009-2013 for GLONASS). In this context, the CNES/CLS Analysis Centers provided SINEX solutions to the IDS and IGS Combination Centers, respectively multi-satellite weekly solutions and daily solutions. Normal equations derived from this analysis are also made available to the GRGS Combination Center for the combination at the observation level of the geodetic parameters measured by DORIS, GPS, SLR and VLBI techniques. The purpose of this presentation is to point out how the overall quality of the DORIS and GNSS data processing benefits from the use of the same software and a common basis of models. Here, we present the modeling standards, the networks and the processing strategies. Assessments of some models are also discussed. The quality and the homogeneity of the products (orbits, station coordinates and Earth Orientation Parameters) over the complete period are shown, as well as the temporal variations of some parameters (dynamical parameters, orbit residuals, internal orbit overlaps ...). Some examples of time series of DORIS and GNSS station positions at collocated sites complete this presentation.

Comparison of shipborne GNSS-derived precipitable water vapor with radiosonde in the western North Pacific and in the seas adjacent to Japan

Science.gov (United States)

Shoji, Yoshinori; Sato, Kazutoshi; Yabuki, Masanori; Tsuda, Toshitaka

2017-11-01

We installed two global navigation satellite system (GNSS) antennas on a research vessel, the RYOFU MARU of the Japan Meteorological Agency, and conducted experimental observations to assess the GNSS-derived precipitable water vapor (PWV) from October 19, 2016, to August 6, 2017. One antenna was set on the mast (MAST), while another antenna was set on the upper deck (DECK). The GNSS analysis was conducted using the precise point positioning procedure with a real-time GNSS orbit. A quality control (QC) procedure based on the amount of zenith tropospheric delay (ZTD) time variation was proposed. After the QC was applied, the retrieved PWVs were compared to 77 radiosonde observations. The PWVs of MAST agreed with the radiosonde observations with a 1.7 mm root mean square (RMS) difference, a - 0.7-mm bias, and 3.6% rejection rate, while that of DECK showed a 3.2, - 0.8 mm, and 15.7%. The larger RMS and higher rejection rate of DECK imply a stronger multi-path effect on the deck. The differences in the GNSS PWV versus radiosonde observations were compared to the atmospheric delay, the estimated altitude of the GNSS antenna, the vessel's moving speed, the wind speed, and the wave height. The atmospheric delay and GNSS antenna altitude showed moderate correlation with the differences. The results suggest the kinematic PPP's potential for practical water vapor monitoring over oceans worldwide. At the same time, from the growing negative biases with the PWV value and with estimated antenna altitude, it could be inferred that the difficulty grows in separating the signal delay from the vertical coordinate under high-humidity conditions.[Figure not available: see fulltext.

Real-time positioning in logging: Effects of forest stand characteristics, topography, and line-of-sight obstructions on GNSS-RF transponder accuracy and radio signal propagation.

Directory of Open Access Journals (Sweden)

Eloise G Zimbelman

Full Text Available Real-time positioning on mobile devices using global navigation satellite system (GNSS technology paired with radio frequency (RF transmission (GNSS-RF may help to improve safety on logging operations by increasing situational awareness. However, GNSS positional accuracy for ground workers in motion may be reduced by multipath error, satellite signal obstruction, or other factors. Radio propagation of GNSS locations may also be impacted due to line-of-sight (LOS obstruction in remote, forested areas. The objective of this study was to characterize the effects of forest stand characteristics, topography, and other LOS obstructions on the GNSS accuracy and radio signal propagation quality of multiple Raveon Atlas PT GNSS-RF transponders functioning as a network in a range of forest conditions. Because most previous research with GNSS in forestry has focused on stationary units, we chose to analyze units in motion by evaluating the time-to-signal accuracy of geofence crossings in 21 randomly-selected stands on the University of Idaho Experimental Forest. Specifically, we studied the effects of forest stand characteristics, topography, and LOS obstructions on (1 the odds of missed GNSS-RF signals, (2 the root mean squared error (RMSE of Atlas PTs, and (3 the time-to-signal accuracy of safety geofence crossings in forested environments. Mixed-effects models used to analyze the data showed that stand characteristics, topography, and obstructions in the LOS affected the odds of missed radio signals while stand variables alone affected RMSE. Both stand characteristics and topography affected the accuracy of geofence alerts.

Real-time positioning in logging: Effects of forest stand characteristics, topography, and line-of-sight obstructions on GNSS-RF transponder accuracy and radio signal propagation.

Science.gov (United States)

Zimbelman, Eloise G; Keefe, Robert F

2018-01-01

Real-time positioning on mobile devices using global navigation satellite system (GNSS) technology paired with radio frequency (RF) transmission (GNSS-RF) may help to improve safety on logging operations by increasing situational awareness. However, GNSS positional accuracy for ground workers in motion may be reduced by multipath error, satellite signal obstruction, or other factors. Radio propagation of GNSS locations may also be impacted due to line-of-sight (LOS) obstruction in remote, forested areas. The objective of this study was to characterize the effects of forest stand characteristics, topography, and other LOS obstructions on the GNSS accuracy and radio signal propagation quality of multiple Raveon Atlas PT GNSS-RF transponders functioning as a network in a range of forest conditions. Because most previous research with GNSS in forestry has focused on stationary units, we chose to analyze units in motion by evaluating the time-to-signal accuracy of geofence crossings in 21 randomly-selected stands on the University of Idaho Experimental Forest. Specifically, we studied the effects of forest stand characteristics, topography, and LOS obstructions on (1) the odds of missed GNSS-RF signals, (2) the root mean squared error (RMSE) of Atlas PTs, and (3) the time-to-signal accuracy of safety geofence crossings in forested environments. Mixed-effects models used to analyze the data showed that stand characteristics, topography, and obstructions in the LOS affected the odds of missed radio signals while stand variables alone affected RMSE. Both stand characteristics and topography affected the accuracy of geofence alerts.

The combined geodetic network adjusted on the reference ellipsoid – a comparison of three functional models for GNSS observations

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Kadaj Roman

2016-12-01

Full Text Available The adjustment problem of the so-called combined (hybrid, integrated network created with GNSS vectors and terrestrial observations has been the subject of many theoretical and applied works. The network adjustment in various mathematical spaces was considered: in the Cartesian geocentric system on a reference ellipsoid and on a mapping plane. For practical reasons, it often takes a geodetic coordinate system associated with the reference ellipsoid. In this case, the Cartesian GNSS vectors are converted, for example, into geodesic parameters (azimuth and length on the ellipsoid, but the simple form of converted pseudo-observations are the direct differences of the geodetic coordinates. Unfortunately, such an approach may be essentially distorted by a systematic error resulting from the position error of the GNSS vector, before its projection on the ellipsoid surface. In this paper, an analysis of the impact of this error on the determined measures of geometric ellipsoid elements, including the differences of geodetic coordinates or geodesic parameters is presented. Assuming that the adjustment of a combined network on the ellipsoid shows that the optimal functional approach in relation to the satellite observation, is to create the observational equations directly for the original GNSS Cartesian vector components, writing them directly as a function of the geodetic coordinates (in numerical applications, we use the linearized forms of observational equations with explicitly specified coefficients. While retaining the original character of the Cartesian vector, one avoids any systematic errors that may occur in the conversion of the original GNSS vectors to ellipsoid elements, for example the vector of the geodesic parameters. The problem is theoretically developed and numerically tested. An example of the adjustment of a subnet loaded from the database of reference stations of the ASG-EUPOS system was considered for the preferred functional

Reduction of ZTD outliers through improved GNSS data processing and screening strategies

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Stepniak, Katarzyna; Bock, Olivier; Wielgosz, Pawel

2018-03-01

Though Global Navigation Satellite System (GNSS) data processing has been significantly improved over the years, it is still commonly observed that zenith tropospheric delay (ZTD) estimates contain many outliers which are detrimental to meteorological and climatological applications. In this paper, we show that ZTD outliers in double-difference processing are mostly caused by sub-daily data gaps at reference stations, which cause disconnections of clusters of stations from the reference network and common mode biases due to the strong correlation between stations in short baselines. They can reach a few centimetres in ZTD and usually coincide with a jump in formal errors. The magnitude and sign of these biases are impossible to predict because they depend on different errors in the observations and on the geometry of the baselines. We elaborate and test a new baseline strategy which solves this problem and significantly reduces the number of outliers compared to the standard strategy commonly used for positioning (e.g. determination of national reference frame) in which the pre-defined network is composed of a skeleton of reference stations to which secondary stations are connected in a star-like structure. The new strategy is also shown to perform better than the widely used strategy maximizing the number of observations available in many GNSS programs. The reason is that observations are maximized before processing, whereas the final number of used observations can be dramatically lower because of data rejection (screening) during the processing. The study relies on the analysis of 1 year of GPS (Global Positioning System) data from a regional network of 136 GNSS stations processed using Bernese GNSS Software v.5.2. A post-processing screening procedure is also proposed to detect and remove a few outliers which may still remain due to short data gaps. It is based on a combination of range checks and outlier checks of ZTD and formal errors. The accuracy of the

Improving GNSS time series for volcano monitoring: application to Canary Islands (Spain)

Science.gov (United States)

García-Cañada, Laura; Sevilla, Miguel J.; Pereda de Pablo, Jorge; Domínguez Cerdeña, Itahiza

2017-04-01

The number of permanent GNSS stations has increased significantly in recent years for different geodetic applications such as volcano monitoring, which require a high precision. Recently we have started to have coordinates time series long enough so that we can apply different analysis and filters that allow us to improve the GNSS coordinates results. Following this idea we have processed data from GNSS permanent stations used by the Spanish Instituto Geográfico Nacional (IGN) for volcano monitoring in Canary Islands to obtained time series by double difference processing method with Bernese v5.0 for the period 2007-2014. We have identified the characteristics of these time series and obtained models to estimate velocities with greater accuracy and more realistic uncertainties. In order to improve the results we have used two kinds of filters to improve the time series. The first, a spatial filter, has been computed using the series of residuals of all stations in the Canary Islands without an anomalous behaviour after removing a linear trend. This allows us to apply this filter to all sets of coordinates of the permanent stations reducing their dispersion. The second filter takes account of the temporal correlation in the coordinate time series for each station individually. A research about the evolution of the velocity depending on the series length has been carried out and it has demonstrated the need for using time series of at least four years. Therefore, in those stations with more than four years of data, we calculated the velocity and the characteristic parameters in order to have time series of residuals. This methodology has been applied to the GNSS data network in El Hierro (Canary Islands) during the 2011-2012 eruption and the subsequent magmatic intrusions (2012-2014). The results show that in the new series it is easier to detect anomalous behaviours in the coordinates, so they are most useful to detect crustal deformations in volcano monitoring.

Innovative Sea Surface Monitoring with GNSS-Reflectometry aboard ISS: Overview and Recent Results from GEROS-ISS

DEFF Research Database (Denmark)

Wickert, Jens; Andersen, Ole Baltazar; Bandeiras, J.

GEROS-ISS (GEROS hereafter) stands for GNSS REflectometry, Radio Occultation and Scatterometry onboard the International Space Station. It is a scientific experiment, proposed to the European Space Agency (ESA)in 2011 for installation aboard the ISS. The main focus of GEROS is the dedicated use o...... of signals from the currently available Global Navigation Satellite Systems (GNSS) for remote sensing of the System Earth with focus to Climate Change characterisation. The GEROS mission idea and the current status are briefly reviewed....

Testing Accuracy and Repeatability of UAV Blocks Oriented with GNSS-Supported Aerial Triangulation

Directory of Open Access Journals (Sweden)

Francesco Benassi

2017-02-01

Full Text Available UAV Photogrammetry today already enjoys a largely automated and efficient data processing pipeline. However, the goal of dispensing with Ground Control Points looks closer, as dual-frequency GNSS receivers are put on board. This paper reports on the accuracy in object space obtained by GNSS-supported orientation of four photogrammetric blocks, acquired by a senseFly eBee RTK and all flown according to the same flight plan at 80 m above ground over a test field. Differential corrections were sent to the eBee from a nearby ground station. Block orientation has been performed with three software packages: PhotoScan, Pix4D and MicMac. The influence on the checkpoint errors of the precision given to the projection centers has been studied: in most cases, values in Z are critical. Without GCP, the RTK solution consistently achieves a RMSE of about 2–3 cm on the horizontal coordinates of checkpoints. In elevation, the RMSE varies from flight to flight, from 2 to 10 cm. Using at least one GCP, with all packages and all test flights, the geocoding accuracy of GNSS-supported orientation is almost as good as that of a traditional GCP orientation in XY and only slightly worse in Z.

Techniques and methods to guarantee Bologna-conform higher education in GNSS

Science.gov (United States)

Mayer, M.

2012-04-01

The Bologna Declaration is aiming for student-centered, outcome-related, and competence-based teaching. In order to fulfill these demands, deep level learning techniques should be used to meet the needs of adult-compatible and self-determined learning. The presentation will summarize selected case studies carried out in the framework of the lecture course "Introduction into GNSS positioning" of the Geodetic Institute of the Karlsruhe Institute of Technology (Karlsruhe, Germany). The lecture course "Introduction into GNSS positioning" is a compulsory part of the Bachelor study course "Geodesy and Geoinformatics" and also a supplementary module of the Bachelor study course "Geophysics". Within the lecture course, basic knowledge and basic principles of Global Navigation Satellite Systems, like GPS, are imparted. The lecture course was migrated starting from a classically designed geodetic lecture course, which consisted of a well-adapted combination of teacher-centered classroom lectures and practical training (e.g., field exercises). The recent Bologna-conform blended learning concepts supports and motivates students to learn more sustainable using online and classroom learning methods. Therefore, an appropriate combination of - classroom lectures: Students and teacher give lectures - practical training: Students select topics individually - online learning: ILIAS (learning management system) is used as data, result, and communication platform. The framing didactical method is based on the so-called anchored instruction approach. Within this approach, an up-to-date scientific GNSS-related paper dealing with the large-scale geodetic project "Fehmarn Belt Fixed Link" is used as anchor. The students have to read the paper individually in the beginning of the semester. This enables them to realize a lot of not-known GNSS-related facts. Therefore, questions can be formulated. The lecture course deals with these questions, in order to answer them. At the end of the

Syntheses, characterization and antifungal activity of tris(1,10-phenanthroline)iron(II) bis(n-r-sulfonyldithiocarbimate)zincate(II)

Energy Technology Data Exchange (ETDEWEB)

Bottega, Fernanda C.; Oliveira, Marcelo R. L.; Garcia, Camila V.; Menezes, Daniele C.; Rubinger, Mayura M.M., E-mail: marcelor@ufv.br [Departamento de Quimica, Universidade Federal de Vicosa, MG (Brazil); Zambolim, Laercio [Departamento de Fitopatologia, Universidade Federal de Vicosa, MG (Brazil)

2013-09-01

Four new compounds with the general formula [Fe(phen){sub 3}][Zn(RSO{sub 2}N=CS{sub 2}){sub 2}], where phen = 1,10-phenanthroline, R = 4-FC{sub 6}H{sub 4}(1), 4-ClC{sub 6}H{sub 4} (2), 4-BrC{sub 6}H{sub 4} (3) and 4-IC{sub 6}H{sub 4} (4), respectively, were obtained by the reaction of the appropriate potassium N-R-sulfonyldithiocarbimate (RSO{sub 2}N=CS{sub 2}K{sub 2}) and tris(1,10-phenanthroline)iron(II) sulfate, with zinc(II) acetate dihydrate in dimethylformamide. The elemental analyses and the IR data were consistent with the formation of the expected complexes salts. The {sup 1}H and {sup 13}C NMR spectra showed the signals for the cationic iron(II) complex and dithiocarbamate moieties. The molar conductance data were consistent with the 1:1 cation:anion complexes in 1-4. The antifungal activities of the compounds were tested in vitro against Candida albicans, Candida tropicalis and Colletotrichum gloeosporioides. (author)

GNSS Transpolar Earth Reflectometry exploriNg System (G-TERN): Mission Concept

DEFF Research Database (Denmark)

Cardellach, Estel; Wickert, Jens; Baggen, Rens

2018-01-01

. Over polar areas, the G-TERN will measure sea ice surface elevation (polarimetry aspects at 30-km resolution and 3-days full coverage. G-TERN will implement the interferometric GNSS reflectometry concept, from a single satellite in near-polar orbit with capability...

COMPARISON BETWEEN RGB AND RGB-D CAMERAS FOR SUPPORTING LOW-COST GNSS URBAN NAVIGATION

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L. Rossi

2018-05-01

Full Text Available A pure GNSS navigation is often unreliable in urban areas because of the presence of obstructions, thus preventing a correct reception of the satellite signal. The bridging between GNSS outages, as well as the vehicle attitude reconstruction, can be recovered by using complementary information, such as visual data acquired by RGB-D or RGB cameras. In this work, the possibility of integrating low-cost GNSS and visual data by means of an extended Kalman filter has been investigated. The focus is on the comparison between the use of RGB-D or RGB cameras. In particular, a Microsoft Kinect device (second generation and a mirrorless Canon EOS M RGB camera have been compared. The former is an interesting RGB-D camera because of its low-cost, easiness of use and raw data accessibility. The latter has been selected for the high-quality of the acquired images and for the possibility of mounting fixed focal length lenses with a lower weight and cost with respect to a reflex camera. The designed extended Kalman filter takes as input the GNSS-only trajectory and the relative orientation between subsequent pairs of images. Depending on the visual data acquisition system, the filter is different because RGB-D cameras acquire both RGB and depth data, allowing to solve the scale problem, which is instead typical of image-only solutions. The two systems and filtering approaches were assessed by ad-hoc experimental tests, showing that the use of a Kinect device for supporting a u-blox low-cost receiver led to a trajectory with a decimeter accuracy, that is 15 % better than the one obtained when using the Canon EOS M camera.

Synthesis of carbon-14 labelled cis-malonato [(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolane] platinum(II) (SKI 2053R)

International Nuclear Information System (INIS)

Kim, Dae-Kee; Kim, Youngseok; Rim, Jonggill; Kim, Ganghyeok; Gam, Jongsik; Song, Sungkun; Yoo, Kwanghee; Kim, Key H.

1994-01-01

The synthesis of 14 C-labelled cis-malonato[(4R,5R)-4,5-bis(aminomethyl)-2-isopropyl-1,3-dioxolan e]platinum(II) from [1,4- 14 C] D-tartaric acid is described. The overall radiochemical yield of the product in a eight-step sequence was 23.8% and radiochemical purity was 98.5%. (author)

Assessment of the Impact of GNSS Processing Strategies on the Long-Term Parameters of 20 Years IWV Time Series

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Zofia Baldysz

2018-03-01

Full Text Available Advanced processing of collected global navigation satellite systems (GNSS observations allows for the estimation of zenith tropospheric delay (ZTD, which in turn can be converted to the integrated water vapour (IWV. The proper estimation of GNSS IWV can be affected by the adopted GNSS processing strategy. To verify which of its elements cause deterioration and which improve the estimated GNSS IWV, we conducted eight reprocessings of 20 years of GPS observations (01.1996–12.2015. In each of them, we applied a different mapping function, the zenith hydrostatic delay (ZHD a priori value, the cut-off angle, software, and the positioning method. Obtained in such a way, the ZTD time series were converted to the IWV using the meteorological parameters sourced from the ERA-Interim. Then, based on them, the long-term parameters were estimated and compared to those obtained from the IWV derived from the radio sounding (RS observations. In this paper, we analyzed long-term parameters such as IWV mean values, linear trends, and amplitudes of annual and semiannual oscillations. A comparative analysis showed, inter alia, that in terms of the investigation of the IWV linear trend the precise point positioning (PPP method is characterized by higher accuracy than the differential one. It was also found that using the GPT2 model and the higher elevation mask brings benefits to the GNSS IWV linear trend estimation.

Multi-GNSS signal-in-space range error assessment - Methodology and results

Science.gov (United States)

Montenbruck, Oliver; Steigenberger, Peter; Hauschild, André

2018-06-01

The positioning accuracy of global and regional navigation satellite systems (GNSS/RNSS) depends on a variety of influence factors. For constellation-specific performance analyses it has become common practice to separate a geometry-related quality factor (the dilution of precision, DOP) from the measurement and modeling errors of the individual ranging measurements (known as user equivalent range error, UERE). The latter is further divided into user equipment errors and contributions related to the space and control segment. The present study reviews the fundamental concepts and underlying assumptions of signal-in-space range error (SISRE) analyses and presents a harmonized framework for multi-GNSS performance monitoring based on the comparison of broadcast and precise ephemerides. The implications of inconsistent geometric reference points, non-common time systems, and signal-specific range biases are analyzed, and strategies for coping with these issues in the definition and computation of SIS range errors are developed. The presented concepts are, furthermore, applied to current navigation satellite systems, and representative results are presented along with a discussion of constellation-specific problems in their determination. Based on data for the January to December 2017 time frame, representative global average root-mean-square (RMS) SISRE values of 0.2 m, 0.6 m, 1 m, and 2 m are obtained for Galileo, GPS, BeiDou-2, and GLONASS, respectively. Roughly two times larger values apply for the corresponding 95th-percentile values. Overall, the study contributes to a better understanding and harmonization of multi-GNSS SISRE analyses and their use as key performance indicators for the various constellations.

Inhibition of B cell proliferation by antisense DNA to both alpha and beta forms of Fc epsilon R II.

Science.gov (United States)

Bhatti, L; Behle, K; Stevens, R H

1992-10-01

Epstein-Barr Virus (EBV) infection activates B lymphocyte proliferation through partially understood mechanisms, resulting in phenotypic changes, including the appearance of new antigens. One such antigen is Fc epsilon R II/CD-23 which may be relevant for B cell proliferation. We have used anti-sense oligonucleotides to study the importance of the two forms of this molecule for proliferation in the EBV-transformed, Fc epsilon R II +ve lymphoblastoid B cell line, RPMI 8866. Anti-sense oligodeoxynucleotides were generated to the two forms of Fc epsilon R II; Fc epsilon R IIa (alpha) and IIb (beta) which differ only in their intracytoplasmic domains. Addition of increasing concentrations of anti-sense oligonucleotides, ranging from 1 to 30 microM, significantly decreased cellular proliferation as measured by the incorporation of [3H]thymidine (inhibition range 8-88%). Optimum inhibition of cellular proliferation was apparent at 15 microM concentration of both anti-sense Fc epsilon R IIa and IIb (Fc epsilon R IIa, mean +/- SE = 75 +/- 7% inhibition, p less than 0.001; Fc epsilon R IIb, mean +/- SE = 71 +/- 7% inhibition, p less than 0.001). Anti-sense oligonucleotides complementary to the common part of Fc epsilon R II resulted in a similar inhibition of proliferation. Sense oligonucleotides did not induce significant inhibition. Preincubation of sense and anti-sense oligonucleotides resulted in an abrogation of proliferation inhibition. Moreover, none of these oligonucleotides had any effect on a Fc epsilon R II -ve cell line. Incubation with both anti-sense IIa and IIb resulted in additive, but not synergistic inhibition of proliferation. Addition of soluble Fc epsilon R II did not reverse inhibition of proliferation, suggesting that membrane-bound or intracellular rather than soluble Fc epsilon R II was important for the induced proliferation. Analysis of cell surface expression for Fc epsilon II indicated that while there was a pronounced effect on cell number

Analysis of the dynamic behavior of structures using the high-rate GNSS-PPP method combined with a wavelet-neural model: Numerical simulation and experimental tests

Science.gov (United States)

Kaloop, Mosbeh R.; Yigit, Cemal O.; Hu, Jong W.

2018-03-01

Recently, the high rate global navigation satellite system-precise point positioning (GNSS-PPP) technique has been used to detect the dynamic behavior of structures. This study aimed to increase the accuracy of the extraction oscillation properties of structural movements based on the high-rate (10 Hz) GNSS-PPP monitoring technique. A developmental model based on the combination of wavelet package transformation (WPT) de-noising and neural network prediction (NN) was proposed to improve the dynamic behavior of structures for GNSS-PPP method. A complicated numerical simulation involving highly noisy data and 13 experimental cases with different loads were utilized to confirm the efficiency of the proposed model design and the monitoring technique in detecting the dynamic behavior of structures. The results revealed that, when combined with the proposed model, GNSS-PPP method can be used to accurately detect the dynamic behavior of engineering structures as an alternative to relative GNSS method.

Near real-time estimation of water vapour in the troposphere using ground GNSS and the meteorological data

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J. Bosy

2012-09-01

Full Text Available The near real-time (NRT high resolution water vapour distribution models can be constructed based on GNSS observations delivered from Ground Base Augmentation Systems (GBAS and ground meteorological data. Since 2008 in the territory of Poland, a GBAS system called ASG-EUPOS (Active Geodetic Network has been operating. This paper addresses the problems concerning construction of the NRT model of water vapour distribution in the troposphere near Poland. The first section presents all available GNSS and ground meteorological stations in the area of Poland and neighbouring countries. In this section, data feeding scheme is discussed, together with timeline and time resolution. The high consistency between measured and interpolated temperature value is shown, whereas some discrepancy in the pressure is observed. In the second section, the NRT GNSS data processing strategy of ASG-EUPOS network is discussed. Preliminary results show fine alignment of the obtained Zenith Troposphere Delays (ZTDs with reference data from European Permanent Network (EPN processing center. The validation of NRT troposphere products against daily solution shows 15 mm standard deviation of obtained ZTD differences. The last section presents the first results of 2-D water vapour distribution above the GNSS network and application of the tomographic model to 3-D distribution of water vapour in the atmosphere. The GNSS tomography model, working on the simulated data from numerical forecast model, shows high consistency with the reference data (by means of standard deviation 4 mm km−1 or 4 ppm, however, noise analysis shows high solution sensitivity to errors in observations. The discrepancy for real data preliminary solution (measured as a mean standard deviation between reference NWP data and tomography data was on the level of 9 mm km−1 (or 9 ppm in terms of wet refractivity.

The GNSS network at Piton de la Fournaise

Science.gov (United States)

Staudacher, Thomas; Peltier, Aline; Boissier, Patrice; Di Muro, Andrea; Kowalski, Philippe; Lauret, Frederic

2013-04-01

The Piton de la Fournaise volcano at La Réunion Island in the western Indian Ocean is amongst the most active volcanoes in the world with a mean over 2 centuries of one eruption every 9 month. Since 1998 up to 4 eruptions occurred per year. The volcanological observatory, which is a branch of the Institut de Physique du Globe de Paris, is in charge of the monitoring of the volcanic activity and the prediction of eruptions by means of several networks: deformation, seismicity and gas emission. We will focus here on the GNSS network. The permanent GNSS network consist in 25 stations, 5 stations around the summit craters "Bory" and "Dolomieu", 5 stations at the base of the central cone at about 2 km away from the summit, 6 stations on the eastern flank in the Grandes Pentes and Grand Brûlé area. Two stations are situated north and south outside of the Enclos Fouqué Caldera. Four basis stations are situated farther away outside of the caldera Fouqué at high and low elevation. Very first GPS measurements at Piton de la Fournaise were attempted since 1994 between Bory (BORG) and "Enclos Zéro" (ENCG). The present permanent network was built up since 2004; the central network, covering the volcanic cone was upgraded till 2006. Between end 2009 and early 2010 the eastern flank, which is difficult to access, was equipped in the frame of the "Undervolc program". Data acquisition is usually done every 30 seconds, but can be incremented to 1Hz and even to 20 Hz for the most recent NetR9 receivers. Data files were transmitted by radio every day and evaluated. Presently we move the daily evaluation of the data from Winprism to Gamit, which shows in some cases more precise results, in particular when we compare stations at low and high elevation. The cinematic GPS network consist today in 78 sites, equipped with stainless steel rods cemented in the rock or fixed on metallic tripods. These sites are measured routinely one or two times per year, or more often in case of

The management of scarce water resources using GNSS, InSAR ...

African Journals Online (AJOL)

GNSS receivers were run continuously for a period of 133 days between March and August 2014 to detect possible surface subsidence during pumping and artesian free flow extraction of water in the wellfield. Two InSAR scenes were processed, one during the peak period of water extraction from the wellfield and the other ...

Real-time capture of seismic waves using high-rate multi-GNSS observations: Application to the 2015 Mw 7.8 Nepal earthquake

Science.gov (United States)

Geng, Tao; Xie, Xin; Fang, Rongxin; Su, Xing; Zhao, Qile; Liu, Gang; Li, Heng; Shi, Chuang; Liu, Jingnan

2016-01-01

The variometric approach is investigated to measure real-time seismic waves induced by the 2015 Mw 7.8 Nepal earthquake with high-rate multi-GNSS observations, especially with the contribution of newly available BDS. The velocity estimation using GPS + BDS shows an additional improvement of around 20% with respect to GPS-only solutions. We also reconstruct displacements by integrating GNSS-derived velocities after a linear trend removal (IGV). The displacement waveforms with accuracy of better than 5 cm are derived when postprocessed GPS precise point positioning results are used as ground truth, even if those stations have strong ground motions and static offsets of up to 1-2 m. GNSS-derived velocity and displacement waveforms with the variometric approach are in good agreement with results from strong motion data. We therefore conclude that it is feasible to capture real-time seismic waves with multi-GNSS observations using the IGV-enhanced variometric approach, which has critical implications for earthquake early warning, tsunami forecasting, and rapid hazard assessment.

The Impact of Interference on GNSS Receiver Observables – A Running Digital Sum Based Simple Jammer Detector

Directory of Open Access Journals (Sweden)

M. Z. H. Bhuiyan

2014-09-01

Full Text Available A GNSS-based navigation system relies on externally received information via a space-based Radio Frequency (RF link. This poses susceptibility to RF Interference (RFI and may initiate failure states ranging from degraded navigation accuracy to a complete signal loss condition. To guarantee the integrity of the received GNSS signal, the receiver should either be able to function in the presence of RFI without generating misleading information (i.e., offering a navigation solution within an accuracy limit, or the receiver must detect RFI so that some other means could be used as a countermeasure in order to ensure robust and accurate navigation. Therefore, it is of utmost importance to identify an interference occurrence and not to confuse it with other signal conditions, for example, indoor or deep urban canyon, both of which have somewhat similar impact on the navigation performance. Hence, in this paper, the objective is to investigate the effect of interference on different GNSS receiver observables in two different environments: i. an interference scenario with an inexpensive car jammer, and ii. an outdoor-indoor scenario without any intentional interference. The investigated observables include the Automatic Gain Control (AGC measurements, the digitized IF (Intermediate Frequency signal levels, the Delay Locked Loop and the Phase Locked Loop discriminator variances, and the Carrier-to-noise density ratio (C/N0 measurements. The behavioral pattern of these receiver observables is perceived in these two different scenarios in order to comprehend which of those observables would be able to separate an interference situation from an indoor scenario, since in both the cases, the resulting positioning accuracy and/or availability are affected somewhat similarly. A new Running Digital Sum (RDS -based interference detection method is also proposed herein that can be used as an alternate to AGC-based interference detection. It is shown in this paper

Receptor GNSS multiantena para aplicaciones aeroespaciales

OpenAIRE

Cogo, Jorge; López La Valle, Ramón G.; Puga, Gerardo L.; Smidt, Javier A.; Díaz, Juan G.; García, Javier Gonzalo; Roncagliolo, Pedro Agustín; Muravchik, Carlos Horacio

2013-01-01

La determinación de la posición y velocidad del vehículo es una de las tareas críticas en las aplicaciones aeroespaciales como es el caso de aviones, satélites o cohetes. En los últimos años esta tarea se ha visto favorecida por el despliegue de los Sistemas de Navegación Global por Satélite (GNSS). Estos sistemas, utilizando como base una constelación de satélites que envían señales a la superficie terrestre, permiten que un usuario que cuente con un receptor adecuado pueda obtener esta info...

GNSS monitoring of the ionosphere for Space Weather services

Science.gov (United States)

Krankowski, A.; Sieradzki, R.; Zakharenkova, I. E.; Cherniak, I. V.

2012-04-01

The International GNSS Service (IGS) Ionosphere Working Group routinely provides the users global ionosphere maps (GIMs) of vertical total electron content (vTEC). The IGS GIMs are provided with spatial resolution of 5.0 degrees x 2.5 degrees in longitude and latitude, respectively. The current temporal resolution is 2 hours, however, 1-hour maps are delivered as a pilot project. There are three types IGS GIMs: the final, rapid and predicted. The latencies of the IGS ionospheric final and rapid products are 10 days and 1 day, respectively. The predicted GIMs are generated for 1 and 2 days in advance. There are four IGS Associate Analysis Centres (IAACs) that provide ionosphere maps computed with independent methodologies using GNSS data. These maps are uploaded to the IGS Ionosphere Combination and Validation Center at the GRL/UWM (Geodynamics Research Laboratory of the University of Warmia and Mazury in Olsztyn, Poland) that produces the IGS official ionospheric products, which are published online via ftp and www. On the other hand, the increasing number of permanently tracking GNSS stations near the North Geomagnetic Pole allow for using satellite observations to detect the ionospheric disturbances at high latitudes with even higher spatial resolution. In the space weather service developed at GRL/UWM, the data from the Arctic stations belonging to IGS/EPN/POLENET networks were used to study TEC fluctuations and scintillations. Since the beginning of 2011, a near real-time service presenting the conditions in the ionosphere have been operational at GRL/UWM www site. The rate of TEC index (ROTI) expressed in TECU/min is used as a measure of TEC fluctuations. The service provides 2-hour maps of the TEC variability. In addition, for each day the daily map of the ionospheric fluctuations as a function geomagnetic local time is also created. This presentation shows the architecture, algorithms, performance and future developments of the IGS GIMs and this new space

Using GNSS for Assessment Recent Sea Level Rise in the Northwestern Part of the Arabian Gulf

Science.gov (United States)

Alothman, A. O.; Bos, M. S.; Fernandes, R.

2017-12-01

Due to the global warming acting recently (in the 21st century) on the planet Earth, an associated sea level rise is predicted to reach up to 30 cm to 60 cm in some regions. Sea level monitoring is important for the Kingdom of Saudi Arabia, since it is surrounded by very long cost of about 3400 km in length and hundreds of isolated islands. The eastern coast line of KSA, in the Arabian Gulf, needs some monitoring in the long term, due to low land nature of the region. Also, the ongoing oil withdrawal activities in the area, may affect the regional sea level rise. In addition to these two facts, the tectonic structure of the Arabian Peninsula is one factor. The Regional Relative sea level in the eastern cost of Saudi Arabia has been estimated in the past using tide gauge data of more than 28 years using the vertical displacement of permanent Global Navigation Satellite System GNSS stations having time span of only about 3 years. In this paper, we discuss and update the methodology and results from Alothman et al. (2014), particularly by checking and extending the GNSS solutions. Since 3 of the 6 GPS stations used only started observing in the end of 2011, the longer time series have now significantly lower uncertainties in the estimated vertical rate. Longer time span of GNSS observations were included and 500 synthetic time series were estimated and seasonal signals were analysed. it is concluded that the varying seasonal signal present in the GNSS time series causes an underestimation of 0.1 mm/yr for short time series of 3 years. In addition to the implications of using short time series to estimate the vertical land motion, we found that if the varying seasonal signals are present in the data, the problem is aggravated. This finding can be useful for other studies analyzing short GNSS time series.

Deformation integrity monitoring for GNSS positioning services including local, regional and large scale hazard monitoring - the Karlsruhe approach and software(MONIKA)

Science.gov (United States)

Jaeger, R.

2007-05-01

GNSS-positioning services like SAPOS/ascos in Germany and many others in Europe, America and worldwide, usually yield in a short time their interdisciplinary and country-wide use for precise geo-referencing, replacing traditional low order geodetic networks. So it becomes necessary that possible changes of the reference stations' coordinates are detected ad hoc. The GNSS-reference-station MONitoring by the KArlsruhe approach and software (MONIKA) are designed for that task. The developments at Karlsruhe University of Applied Sciences in cooperation with the State Survey of Baden-Württemberg are further motivated by a the official resolution of the German state survey departments' association (Arbeitsgemeinschaft der Vermessungsverwaltungen Deutschland (AdV)) 2006 on coordinate monitoring as a quality-control duty of the GNSS-positioning service provider. The presented approach can - besides the coordinate control of GNSS-positioning services - also be used to set up any GNSS-service for the tasks of an area-wide geodynamical and natural disaster-prevention service. The mathematical model of approach, which enables a multivariate and multi-epochal design approach, is based on the GNSS-observations input of the RINEX-data of the GNSS service, followed by fully automatic processing of baselines and/or session, and a near-online setting up of epoch-state vectors and their covariance-matrices in a rigorous 3D network adjustment. In case of large scale and long-term monitoring situations, geodynamical standard trends (datum-drift, plate-movements etc.) are accordingly considered and included in the mathematical model of MONIKA. The coordinate-based deformation monitoring approach, as third step of the stepwise adjustments, is based on the above epoch-state vectors, and - splitting off geodynamics trends - hereby on a multivariate and multi-epochal congruency testing. So far, that no other information exists, all points are assumed as being stable and congruent reference

Estimation and analysis of the short-term variations of multi-GNSS receiver differential code biases using global ionosphere maps

Science.gov (United States)

Li, Min; Yuan, Yunbin; Wang, Ningbo; Liu, Teng; Chen, Yongchang

2017-12-01

Care should be taken to minimize the adverse impact of differential code biases (DCBs) on global navigation satellite systems (GNSS)-derived ionospheric information determinations. For the sake of convenience, satellite and receiver DCB products provided by the International GNSS Service (IGS) are treated as constants over a period of 24 h (Li et al. (2014)). However, if DCB estimates show remarkable intra-day variability, the DCBs estimated as constants over 1-day period will partially account for ionospheric modeling error; in this case DCBs will be required to be estimated over shorter time period. Therefore, it is important to further gain insight into the short-term variation characteristics of receiver DCBs. In this contribution, the IGS combined global ionospheric maps and the German Aerospace Center (DLR)-provided satellite DCBs are used in the improved method to determine the multi-GNSS receiver DCBs with an hourly time resolution. The intra-day stability of the receiver DCBs is thereby analyzed in detail. Based on 1 month of data collected within the multi-GNSS experiment of the IGS, a good agreement within the receiver DCBs is found between the resulting receiver DCB estimates and multi-GNSS DCB products from the DLR at a level of 0.24 ns for GPS, 0.28 ns for GLONASS, 0.28 ns for BDS, and 0.30 ns for Galileo. Although most of the receiver DCBs are relatively stable over a 1-day period, large fluctuations (more than 9 ns between two consecutive hours) within the receiver DCBs can be found. We also demonstrate the impact of the significant short-term variations in receiver DCBs on the extraction of ionospheric total electron content (TEC), at a level of 12.96 TECu (TEC unit). Compared to daily receiver DCB estimates, the hourly DCB estimates obtained from this study can reflect the short-term variations of the DCB estimates more dedicatedly. The main conclusion is that preliminary analysis of characteristics of receiver DCB variations over short

An inductorless multi-mode RF front end for GNSS receiver in 55 nm CMOS

Science.gov (United States)

Yanbin, Luo; Chengyan, Ma; Yebing, Gan; Min, Qian; Tianchun, Ye

2015-10-01

An inductorless multi-mode RF front end for a global navigation satellite system (GNSS) receiver is presented. Unlike the traditional topology of a low noise amplifier (LNA), the inductorless current-mode noise-canceling LNA is applied in this design. The high-impedance-input radio frequency amplifier (RFA) further amplifies the GNSS signals and changes the single-end signal path into fully differential. The passive mixer down-converts the signals to the intermediate frequency (IF) band and conveys the signals to the analogue blocks. The local oscillator (LO) buffer divides the output frequency of the voltage controlled oscillator (VCO) and generates 25%-duty-cycle quadrature square waves to drive the mixer. Our measurement results display that the implemented RF front end achieves good overall performance while consuming only 6.7 mA from 1.2 V supply. The input return loss is better than -26 dB and the ultra low noise figure of 1.43 dB leads to high sensitivity of the GNSS receiver. The input 1 dB compression point is -43 dBm at the high gain of 48 dB. The designed circuit is fabricated in 55 nm CMOS technology and the die area, which is much smaller than traditional circuit, is around 220 × 280 μm2.

The case for a Supersite for real-time GNSS hazard monitoring on a global scale

Science.gov (United States)

Bar-Sever, Y. E.

2017-12-01

Real-time measurements from many hundreds of GNSS tracking sites around the world are publicly available today, and the amount of streaming data is steadily increasing as national agencies densify their local and global infrastructure for natural hazard monitoring and a variety of geodetic, cadastral, and other civil applications. Thousands of such sites can soon be expected on a global scale. It is a challenge to manage and make optimal use of this massive amount of real-time data. We advocate the creation of Supersite(s), in the parlance of the U.N. Global Earth Observation System of Systems (https://www.earthobservations.org/geoss.php), to generate high level real-time data products from the raw GNSS measurements from all available sources (many thousands of sites). These products include: • High rate, real-time positioning time series for assessing rapid crustal motion due to Earthquakes, volcanic activities, land slides, etc. • Co-seismic displacement to help resolve earthquake mechanism and moment magnitude • Real-time total electron content (TEC) fluctuations to augment Dart buoy in detecting and tracking tsunamis • Aggregation of the many disparate raw data dispensation servers (Casters)Recognizing that natural hazards transcend national boundaries in terms of direct and indirect (e.g., economical, security) impact, the benefits from centralized, authoritative processing of GNSS measurements is manifold: • Offers a one-stop shop to less developed nations and institutions for raw and high-level products, in support of research and applications • Promotes the installation of tracking sites and the contribution of data from nations without the ability to process the data • Reduce dependency on local responsible agencies impacted by a natural disaster • Reliable 24/7 operations, independent of voluntary, best effort contributions from good-willing scientific organizationsThe JPL GNSS Real-Time Earthquake and Tsunami (GREAT) Alert has been

Developmental Decline in the MicroRNA 199a (miR-199a)/miR-214 Cluster in Human Fetal Lung Promotes Type II Cell Differentiation by Upregulating Key Transcription Factors.

Science.gov (United States)

Mishra, Ritu; Benlhabib, Houda; Guo, Wei; Lerma Cervantes, Connie B; Mendelson, Carole R

2018-06-01

The major surfactant protein, SP-A (a product of the SFTPA gene), serves as a marker of type II pneumocyte differentiation and surfactant synthesis. SFTPA expression in cultured human fetal lung (HFL) epithelial cells is upregulated by hormones that increase cyclic AMP (cAMP) and activate TTF-1/NKX2.1 and NF-κB. To further define mechanisms for type II cell differentiation and induction of SP-A, we investigated roles of microRNAs (miRNAs). Using microarray to identify differentially expressed miRNAs in HFL epithelial cells during type II cell differentiation in culture, we observed that members of the miRNA 199a (miR-199a)/miR-214 cluster were significantly downregulated during differentiation. Validated and predicted targets of miR-199a-3p/miR-199a-5p and miR-214, which serve roles in type II cell differentiation (COX-2, NF-κB p50/p65, and CREB1), and the CREB1 target, C/EBPβ, were coordinately upregulated. Accordingly, overexpression of miR-199a-5p, miR-199a-3p, or miR-214 mimics in cultured HFL epithelial cells decreased COX-2, NF-κB p50/p65, CREB1, and C/EBPβ proteins, with an associated inhibition of SP-A expression. Interestingly, overexpression of the EMT factor, ZEB1, which declines during cAMP-induced type II cell differentiation, increased pri-miR-199a and reduced the expression of the targets NF-κB/p50 and COX-2. Collectively, these findings suggest that the developmental decline in miR-199a/miR-214 in HFL causes increased expression of critical targets that enhance type II cell differentiation and SP-A expression. Copyright © 2018 American Society for Microbiology.

Molecular organization of the 5S rDNA gene type II in elasmobranchs.

Science.gov (United States)

Castro, Sergio I; Hleap, Jose S; Cárdenas, Heiber; Blouin, Christian

2016-01-01

The 5S rDNA gene is a non-coding RNA that can be found in 2 copies (type I and type II) in bony and cartilaginous fish. Previous studies have pointed out that type II gene is a paralog derived from type I. We analyzed the molecular organization of 5S rDNA type II in elasmobranchs. Although the structure of the 5S rDNA is supposed to be highly conserved, our results show that the secondary structure in this group possesses some variability and is different than the consensus secondary structure. One of these differences in Selachii is an internal loop at nucleotides 7 and 112. These mutations observed in the transcribed region suggest an independent origin of the gene among Batoids and Selachii. All promoters were highly conserved with the exception of BoxA, possibly due to its affinity to polymerase III. This latter enzyme recognizes a dT4 sequence as stop signal, however in Rajiformes this signal was doubled in length to dT8. This could be an adaptation toward a higher efficiency in the termination process. Our results suggest that there is no TATA box in elasmobranchs in the NTS region. We also provide some evidence suggesting that the complexity of the microsatellites present in the NTS region play an important role in the 5S rRNA gene since it is significantly correlated with the length of the NTS.

Assessment of the NeQuick-2 and IRI-Plas 2017 models using global and long-term GNSS measurements

Science.gov (United States)

Okoh, Daniel; Onwuneme, Sylvester; Seemala, Gopi; Jin, Shuanggen; Rabiu, Babatunde; Nava, Bruno; Uwamahoro, Jean

2018-05-01

The global ionospheric models NeQuick and IRI-Plas have been widely used. However, their uncertainties are not clear at global scale and long term. In this paper, a climatologic assessment of the NeQuick and IRI-Plas models is investigated at a global scale from global navigation satellite system (GNSS) observations. GNSS observations from 36 globally distributed locations were used to evaluate performances of both NeQuick-2 and IRI-Plas 2017 models from January 2006 to July 2017, covering more than the 11-year period of a solar cycle. An hourly interval of diurnal profiles computed on monthly basis was used to measure deviations of the model estimations from corresponding GNSS VTEC observations. Results show that both models are fairly accurate in trends with the GNSS measurements. The NeQuick predictions were generally better than the IRI-Plas predictions in most of the stations and the times. The mean annual prediction errors for the IRI-Plas model typically varied from about 3 TECU at the high latitude stations to about 12 TECU at the low latitude stations, while for the NeQuick the values are respectively about 2-7 TECU. Out of a total 4497 months in which GNSS data were available for all the stations put together for the entire period covered in this work, the NeQuick model was observed to perform better in about 83% of the months while the IRI-Plas performed better in about 17% of the months. The IRI-Plas generally performed better than the NeQuick at certain locations (e.g. DAV1, KERG, and ADIS). For both models, the most of the deviations were witnessed during local daytimes and during seasons that receive maximum solar radiation for various locations. In particular, the IRI-Plas model predictions were improved during periods of increased solar activity at the low latitude stations. The IRI-Plas model overestimates the GNSS VTEC values, except during high solar activity years at some high latitude stations. The NeQuick underestimates the TEC values during

Estimating absolute sea level variations by combining GNSS and Tide gauge data

Digital Repository Service at National Institute of Oceanography (India)

Bos, M.S.; Fernandes, R.M.S; Vethamony, P.; Mehra, P.

Indian tide gauges can be used to estimate sea level rise. To separate relative sea level rise from vertical land motion at the tide gauges, various GNSS stations have been installed in the last years at, or nearby, tide gauges. Using the PSMSL...

The Total Electron Content From InSAR and GNSS: A Midlatitude Study

DEFF Research Database (Denmark)

Musico, Elvira; Cesaroni, Claudio; Spogli, Luca

2018-01-01

The total electron content (TEC) measured from the interferometric synthetic aperture radar (InSAR) and froma dense network of global navigation satellite system (GNSS) receivers are used to assess the capability of InSAR to retrieve ionospheric information, when the tropospheric contribution...

Status of Core Products of the International GNSS Service

Science.gov (United States)

Choi, K. K.

2014-12-01

The International GNSS Service (IGS) has been providing high accuracy GNSS orbits, clocks and Earth Rotation Parameters (ERP) in three different time intervals. The quality of the IGS core products are regularly monitored since 2010, and the level of accuracies has not been changed noticeably. The Final and Rapid orbit's accuracies are known to be about ~2.5 cm and the near-real time (observed) Ultra-rapid orbit is about 3 cm. The real-time orbits obtained by propagating the Ultra-rapid orbits shows an accuracy of about 5 cm. The most significant error source of the real-time orbit is the sub-daily variation of the Earth orientation. Number of IGS08 core sites has been decreasing with the rate of ~0.13 stations per week due to equipment changes and natural disasters such as Earthquakes. This paper summarizes the quality state of the IGS core products for 2014, and the upcoming new official product IGV, Glonass Ultra-rapid orbit product which have been experimental for last 4 years. Eight IGS Analysis Centers (ACs) have completed their efforts to participate in the second reprocessing campaign (repro2). Based on their input, this paper summarizes the models and methodologies each AC have adopted for this campaign.

A REDUNDANT GNSS-INS LOW-COST UAV NAVIGATION SOLUTION FOR PROFESSIONAL APPLICATIONS

Directory of Open Access Journals (Sweden)

J. Navarro

2015-08-01

Full Text Available This paper presents the current results for the FP7 GINSEC project. Its goal is to build a pre-commercial prototype of a low-cost, accurate and reliable system for the professional UAV market. Low-cost, in this context, stands for the use of sensors in the most affordable segment of the market, especially MEMS IMUs and GNSS receivers. Reliability applies to the ability of the autopilot to cope with situations where unfavourable GNSS reception conditions or strong electromagnetic fields make the computation of the position and / or attitude of the UAV difficult. Professional and accurate mean that, at least using post-processing techniques as PPP, it will be possible to reach cm-level precisions that open the door to a range of applications demanding high levels of quality in positioning, as precision agriculture or mapping. To achieve such goal, a rigorous sensor error modelling approach, the use of redundant IMUs and a dual-GNSS receiver setup, together with close-coupling techniques and an extended Kalman filter with self-analysis capabilities have been used. Although the project is not yet complete, the results obtained up to now prove the feasibility of the aforementioned goal, especially in those aspects related to position determination. Research work is still undergoing to estimate the heading using a dual-GNNS receiver setup; preliminary results prove the validity of this approach for relatively long baselines, although positive results are expected when these are shorter than 1 m – which is a necessary requisite for small-sized UAVs.

a Redundant Gnss-Ins Low-Cost Uav Navigation Solution for Professional Applications

Science.gov (United States)

Navarro, J.; Parés, M. E.; Colomina, I.; Bianchi, G.; Pluchino, S.; Baddour, R.; Consoli, A.; Ayadi, J.; Gameiro, A.; Sekkas, O.; Tsetsos, V.; Gatsos, T.; Navoni, R.

2015-08-01

This paper presents the current results for the FP7 GINSEC project. Its goal is to build a pre-commercial prototype of a low-cost, accurate and reliable system for the professional UAV market. Low-cost, in this context, stands for the use of sensors in the most affordable segment of the market, especially MEMS IMUs and GNSS receivers. Reliability applies to the ability of the autopilot to cope with situations where unfavourable GNSS reception conditions or strong electromagnetic fields make the computation of the position and / or attitude of the UAV difficult. Professional and accurate mean that, at least using post-processing techniques as PPP, it will be possible to reach cm-level precisions that open the door to a range of applications demanding high levels of quality in positioning, as precision agriculture or mapping. To achieve such goal, a rigorous sensor error modelling approach, the use of redundant IMUs and a dual-GNSS receiver setup, together with close-coupling techniques and an extended Kalman filter with self-analysis capabilities have been used. Although the project is not yet complete, the results obtained up to now prove the feasibility of the aforementioned goal, especially in those aspects related to position determination. Research work is still undergoing to estimate the heading using a dual-GNNS receiver setup; preliminary results prove the validity of this approach for relatively long baselines, although positive results are expected when these are shorter than 1 m - which is a necessary requisite for small-sized UAVs.

Assessment of the possible contribution of space ties on-board GNSS satellites to the terrestrial reference frame

Science.gov (United States)

Bruni, Sara; Rebischung, Paul; Zerbini, Susanna; Altamimi, Zuheir; Errico, Maddalena; Santi, Efisio

2018-04-01

The realization of the international terrestrial reference frame (ITRF) is currently based on the data provided by four space geodetic techniques. The accuracy of the different technique-dependent materializations of the frame physical parameters (origin and scale) varies according to the nature of the relevant observables and to the impact of technique-specific errors. A reliable computation of the ITRF requires combining the different inputs, so that the strengths of each technique can compensate for the weaknesses of the others. This combination, however, can only be performed providing some additional information which allows tying together the independent technique networks. At present, the links used for that purpose are topometric surveys (local/terrestrial ties) available at ITRF sites hosting instruments of different techniques. In principle, a possible alternative could be offered by spacecrafts accommodating the positioning payloads of multiple geodetic techniques realizing their co-location in orbit (space ties). In this paper, the GNSS-SLR space ties on-board GPS and GLONASS satellites are thoroughly examined in the framework of global reference frame computations. The investigation focuses on the quality of the realized physical frame parameters. According to the achieved results, the space ties on-board GNSS satellites cannot, at present, substitute terrestrial ties in the computation of the ITRF. The study is completed by a series of synthetic simulations investigating the impact that substantial improvements in the volume and quality of SLR observations to GNSS satellites would have on the precision of the GNSS frame parameters.

On the occurrence and strength of multi-frequency multi-GNSS Ionospheric Scintillations in Indian sector during declining phase of solar cycle 24

Science.gov (United States)

Srinivasu, V. K. D.; Dashora, N.; Prasad, D. S. V. V. D.; Niranjan, K.; Gopi Krishna, S.

2018-04-01

This study presents unique perspectives of occurrence and strength of low latitude ionospheric scintillations on multiple signals of Global Navigation Satellite System (GNSS) and its frequency dependence using continuous observation records of 780 nights. A robust comparative analysis is performed using scintillation index, S4 and its variation during pre-midnight and post-midnight duration from a GNSS receiver located at Waltair (17.7°N, 83.3°E), India, covering period from July 2014 to August 2016. The results, generally exhibit the impact of declining phase of solar cycle 24 on occurrence and strength of scintillations, which, however, is evidently different over different frequencies transmitted from different GNSS systems. A deeper quantitative analysis uniquely reveals that apart from the solar cycle and seasonal effects, the number of visible satellites of a selected GNSS markedly affect the occurrence and also the strength. Processing scheme of adopting 6 hourly time windows of pre-midnight and post-midnight brought a novel result that the strength and occurrence of strong scintillations decrease with declining solar activity during pre-midnight hours but remarkably increase for moderate and weak scintillations during post-midnight. The physical processes that dominate the post-midnight equatorial ionosphere are invoked to explain such variations that are special during declining solar activity. Finally, inter-GNSS signal analysis in terms of the effect of strong, moderate and weak scintillations is presented with due consideration of number of satellite passes affected and frequency dependence of mean S4. The quantitative results of this study emphasize for the first time effect of low latitude scintillation on GNSS signals in Indian zone under changing background solar and seasonal conditions.

Low-cost precise measurement of oscillator frequency instability based on GNSS carrier observation

Science.gov (United States)

Kou, Yanhong; Jiao, Yue; Xu, Dongyang; Zhang, Meng; Liu, Ya; Li, Xiaohui

2013-03-01

Global navigation satellite systems (GNSS) receivers can be used in time and frequency metrology by exploiting stable GNSS time scales. This paper proposes a low-cost method for precise measurement of oscillator frequency instability using a single-frequency software GNSS receiver. The only required hardware is a common radio frequency (RF) data collection device driven by the oscillator under test (OUT). The receiver solves the oscillator frequency error in high time resolution using the carrier Doppler observation and the broadcast ephemeris from one of the available satellites employing the onboard reference atomic frequency standard that is more stable than the OUT. Considering the non-stable and non-Gaussian properties of the frequency error measurement, an unbiased finite impulse response (FIR) filter is employed to obtain robust estimation and filter out measurement noise. The effects of different filter orders and convolution lengths are further discussed. The frequency error of an oven controlled oscillator (OCXO) is measured using live Beidou-2/Compass signals. The results are compared with the synchronous measurement using a specialized phase comparator with the standard coordinated universal time (UTC) signal from the master clock H226 in the national time service center (NTSC) of China as its reference. The Allan deviation (ADEV) estimates using the two methods have a 99.9% correlation coefficient and a 0.6% mean relative difference over 1-1000 s intervals. The experiment demonstrates the effectiveness and high precision of the software receiver method.

Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies

Science.gov (United States)

Mendoza, Luciano; Bianchi, Clara; Fernández, Laura; Natali, María Paula; Meza, Amalia; Moirano, Juan

2017-04-01

Atmospheric water vapour has been acknowledged as an essential climate variable. Weather prediction and hazard assessment systems benefit from real-time observations, whereas long-term records contribute to climate studies. Nowadays, ground-based GNSS products have become widely employed, complementing satellite observations over the oceans. Although the past decade has seen a significant development of the GNSS infrastructure in Central and South America, its potential for atmospheric water vapour monitoring has not been fully exploited. With this in mind, we have performed a regional, seven-year long and homogeneous analysis, comprising 136 GNSS tracking stations, obtaining high-rate and continuous observations of column integrated water vapour and troposphere zenith total delay (Bianchi et al. 2016). As preliminary application for this data set, we have estimated local water vapour trends, their significance, and their relation with specific climate regimes. We have found evidence of drying at temperate regions in South America, at a rate of about 2% per decade, while a slow moistening of the troposphere over tropical regions is also weakly suggested by our results. Furthermore, we have assessed the regional performance of the empirical model GPT2w to blindly estimate troposphere delays. The model fairly reproduces the observed mean delays, including their annual and semi-annual variations. Nevertheless, a long-term evaluation has shown systematical biases, up to 20 mm, probably inherited form the underling atmospheric reanalysis. Additionally, the complete data set has been made openly available at a scientific repository (doi:10.1594/PANGAEA.858234). References: C. Bianchi, L. Mendoza, L. Fernandez, M. P. Natali, A. Meza, J. F. Moirano, Multi-year GNSS monitoring of atmospheric IWV over Central and South America for climate studies, Ann. Geophys., ISSN 0992-7689, eISSN 1432-0576, 34 (7), 623-639 (doi:10.5194/angeo-34-623-2016).

GNSS Signal Tracking Performance Improvement for Highly Dynamic Receivers by Gyroscopic Mounting Crystal Oscillator.

Science.gov (United States)

Abedi, Maryam; Jin, Tian; Sun, Kewen

2015-08-31

In this paper, the efficiency of the gyroscopic mounting method is studied for a highly dynamic GNSS receiver's reference oscillator for reducing signal loss. Analyses are performed separately in two phases, atmospheric and upper atmospheric flights. Results show that the proposed mounting reduces signal loss, especially in parts of the trajectory where its probability is the highest. This reduction effect appears especially for crystal oscillators with a low elevation angle g-sensitivity vector. The gyroscopic mounting influences frequency deviation or jitter caused by dynamic loads on replica carrier and affects the frequency locked loop (FLL) as the dominant tracking loop in highly dynamic GNSS receivers. In terms of steady-state load, the proposed mounting mostly reduces the frequency deviation below the one-sigma threshold of FLL (1σ(FLL)). The mounting method can also reduce the frequency jitter caused by sinusoidal vibrations and reduces the probability of signal loss in parts of the trajectory where the other error sources accompany this vibration load. In the case of random vibration, which is the main disturbance source of FLL, gyroscopic mounting is even able to suppress the disturbances greater than the three-sigma threshold of FLL (3σ(FLL)). In this way, signal tracking performance can be improved by the gyroscopic mounting method for highly dynamic GNSS receivers.

An inductorless multi-mode RF front end for GNSS receiver in 55 nm CMOS

International Nuclear Information System (INIS)

Luo Yanbin; Ma Chengyan; Gan Yebing; Qian Min; Ye Tianchun

2015-01-01

An inductorless multi-mode RF front end for a global navigation satellite system (GNSS) receiver is presented. Unlike the traditional topology of a low noise amplifier (LNA), the inductorless current-mode noise-canceling LNA is applied in this design. The high-impedance-input radio frequency amplifier (RFA) further amplifies the GNSS signals and changes the single-end signal path into fully differential. The passive mixer down-converts the signals to the intermediate frequency (IF) band and conveys the signals to the analogue blocks. The local oscillator (LO) buffer divides the output frequency of the voltage controlled oscillator (VCO) and generates 25%-duty-cycle quadrature square waves to drive the mixer. Our measurement results display that the implemented RF front end achieves good overall performance while consuming only 6.7 mA from 1.2 V supply. The input return loss is better than −26 dB and the ultra low noise figure of 1.43 dB leads to high sensitivity of the GNSS receiver. The input 1 dB compression point is −43 dBm at the high gain of 48 dB. The designed circuit is fabricated in 55 nm CMOS technology and the die area, which is much smaller than traditional circuit, is around 220 × 280 μm 2 . (paper)

Merged Real Time GNSS Solutions for the READI System

Science.gov (United States)

Santillan, V. M.; Geng, J.

2014-12-01

Real-time measurements from increasingly dense Global Navigational Satellite Systems (GNSS) networks located throughout the western US offer a substantial, albeit largely untapped, contribution towards the mitigation of seismic and other natural hazards. Analyzed continuously in real-time, currently over 600 instruments blanket the San Andreas and Cascadia fault systems of the North American plate boundary and can provide on-the-fly characterization of transient ground displacements highly complementary to traditional seismic strong-motion monitoring. However, the utility of GNSS systems depends on their resolution, and merged solutions of two or more independent estimation strategies have been shown to offer lower scatter and higher resolution. Towards this end, independent real time GNSS solutions produced by Scripps Inst. of Oceanography and Central Washington University (PANGA) are now being formally combined in pursuit of NASA's Real-Time Earthquake Analysis for Disaster Mitigation (READI) positioning goals. CWU produces precise point positioning (PPP) solutions while SIO produces ambiguity resolved PPP solutions (PPP-AR). The PPP-AR solutions have a ~5 mm RMS scatter in the horizontal and ~10mm in the vertical, however PPP-AR solutions can take tens of minutes to re-converge in case of data gaps. The PPP solutions produced by CWU use pre-cleaned data in which biases are estimated as non-integer ambiguities prior to formal positioning with GIPSY 6.2 using a real time stream editor developed at CWU. These solutions show ~20mm RMS scatter in the horizontal and ~50mm RMS scatter in the vertical but re-converge within 2 min. or less following cycle-slips or data outages. We have implemented the formal combination of the CWU and SCRIPPS ENU displacements using the independent solutions as input measurements to a simple 3-element state Kalman filter plus white noise. We are now merging solutions from 90 stations, including 30 in Cascadia, 39 in the Bay Area, and 21

Multi-GNSS high-rate RTK, PPP and novel direct phase observation processing method: application to precise dynamic displacement detection

Science.gov (United States)

Paziewski, Jacek; Sieradzki, Rafal; Baryla, Radoslaw

2018-03-01

This paper provides the methodology and performance assessment of multi-GNSS signal processing for the detection of small-scale high-rate dynamic displacements. For this purpose, we used methods of relative (RTK) and absolute positioning (PPP), and a novel direct signal processing approach. The first two methods are recognized as providing accurate information on position in many navigation and surveying applications. The latter is an innovative method for dynamic displacement determination with the use of GNSS phase signal processing. This method is based on the developed functional model with parametrized epoch-wise topocentric relative coordinates derived from filtered GNSS observations. Current regular kinematic PPP positioning, as well as medium/long range RTK, may not offer coordinate estimates with subcentimeter precision. Thus, extended processing strategies of absolute and relative GNSS positioning have been developed and applied for displacement detection. The study also aimed to comparatively analyze the developed methods as well as to analyze the impact of combined GPS and BDS processing and the dependence of the results of the relative methods on the baseline length. All the methods were implemented with in-house developed software allowing for high-rate precise GNSS positioning and signal processing. The phase and pseudorange observations collected with a rate of 50 Hz during the field test served as the experiment’s data set. The displacements at the rover station were triggered in the horizontal plane using a device which was designed and constructed to ensure a periodic motion of GNSS antenna with an amplitude of ~3 cm and a frequency of ~4.5 Hz. Finally, a medium range RTK, PPP, and direct phase observation processing method demonstrated the capability of providing reliable and consistent results with the precision of the determined dynamic displacements at the millimeter level. Specifically, the research shows that the standard deviation of

Detection of Traveling Ionospheric Disturbances (TIDs) from various man-made sources using Global Navigation Satellite System (GNSS)

Science.gov (United States)

Helmboldt, J.; Park, J.; von Frese, R. R. B.; Grejner-Brzezinska, D. A.

2016-12-01

Traveling ionospheric disturbance (TID) is generated by various sources and detectable by observing the spatial and temporal change of electron contents in the ionosphere. This study focused on detecting and analyzing TIDs generated by acoustic-gravity waves from man-made events including underground nuclear explosions (UNEs), mine collapses, mine blasts, and large chemical explosions (LCEs) using Global Navigation Satellite System (GNSS). In this study we selected different types of events for case study which covers two US and three North Korean UNEs, two large US mine collapses, three large US mine blasts, and a LCE in northern China and a second LCE at the Nevada Test Site. In most cases, we successfully detected the TIDs as array signatures from the multiple nearby GNSS stations. The array-based TID signatures from these studies were found to yield event-appropriate TID propagation speeds ranging from about a few hundred m/s to roughly a km/s. In addition, the event TID waveforms, and propagation angles and directions were established. The TID waveforms and the maximum angle between each event and the IPP of its TID with the longest travel distance from the source may help differentiate UNEs and LCEs, but the uneven distributions of the observing GNSS stations complicates these results. Thus, further analysis is required of the utility of the apertures of event signatures in the ionosphere for discriminating these events. In general, the results of this study show the potential utility of GNSS observations for detecting and mapping the ionospheric signatures of large-energy anthropological explosions and subsurface collapses.

The effect of solar radio bursts on the GNSS radio occultation signals

Science.gov (United States)

Yue, Xinan; Schreiner, William S.; Kuo, Ying-Hwa; Zhao, Biqiang; Wan, Weixing; Ren, Zhipeng; Liu, Libo; Wei, Yong; Lei, Jiuhou; Solomon, Stan; Rocken, Christian

2013-09-01

radio burst (SRB) is the radio wave emission after a solar flare, covering a broad frequency range, originated from the Sun's atmosphere. During the SRB occurrence, some specific frequency radio wave could interfere with the Global Navigation Satellite System (GNSS) signals and therefore disturb the received signals. In this study, the low Earth orbit- (LEO-) based high-resolution GNSS radio occultation (RO) signals from multiple satellites (COSMIC, CHAMP, GRACE, SAC-C, Metop-A, and TerraSAR-X) processed in University Corporation for Atmospheric Research (UCAR) were first used to evaluate the effect of SRB on the RO technique. The radio solar telescope network (RSTN) observed radio flux was used to represent SRB occurrence. An extreme case during 6 December 2006 and statistical analysis during April 2006 to September 2012 were studied. The LEO RO signals show frequent loss of lock (LOL), simultaneous decrease on L1 and L2 signal-to-noise ratio (SNR) globally during daytime, small-scale perturbations of SNR, and decreased successful retrieval percentage (SRP) for both ionospheric and atmospheric occultations during SRB occurrence. A potential harmonic band interference was identified. Either decreased data volume or data quality will influence weather prediction, climate study, and space weather monitoring by using RO data during SRB time. Statistically, the SRP of ionospheric and atmospheric occultation retrieval shows ~4% and ~13% decrease, respectively, while the SNR of L1 and L2 show ~5.7% and ~11.7% decrease, respectively. A threshold value of ~1807 SFU of 1415 MHz frequency, which can result in observable GNSS SNR decrease, was derived based on our statistical analysis.

Loose and Tight GNSS/INS Integrations: Comparison of Performance Assessed in Real Urban Scenarios.

Science.gov (United States)

Falco, Gianluca; Pini, Marco; Marucco, Gianluca

2017-01-29

Global Navigation Satellite Systems (GNSSs) remain the principal mean of positioning in many applications and systems, but in several types of environment, the performance of standalone receivers is degraded. Although many works show the benefits of the integration between GNSS and Inertial Navigation Systems (INSs), tightly-coupled architectures are mainly implemented in professional devices and are based on high-grade Inertial Measurement Units (IMUs). This paper investigates the performance improvements enabled by the tight integration, using low-cost sensors and a mass-market GNSS receiver. Performance is assessed through a series of tests carried out in real urban scenarios and is compared against commercial modules, operating in standalone mode or featuring loosely-coupled integrations. The paper describes the developed tight-integration algorithms with a terse mathematical model and assesses their efficacy from a practical perspective.

The Lithium-, r- and s-Enhanced Metal-Poor Giant HK-II 17435-00532

International Nuclear Information System (INIS)

Roederer, Ian U.; Prieto, Carlos Allende; Sneden, Christopher; Frebel, Anna; Shetrone, Matthew; Rhee, Jaehyon; Gallino, Roberto; Bisterzo, Sara; Beers, Timothy C.; Cowan, John J.

2008-01-01

We present the first detailed abundance analysis of the metal-poor giant HK-II 17435-00532. This star was observed as part of the University of Texas Long-Term Chemical Abundances of Stars in the Halo (CASH) Project. A spectrum was obtained with the High Resolution Spectrograph (HRS) on the Hobby-Eberly Telescope with a resolving power of R∼15000. Our analysis reveals that this star may be located on the red giant branch, red horizontal branch, or early asymptotic giant branch. We find that this metal-poor ([Fe/H] = -2.2) star has an unusually high lithium abundance (logε(Li) = +2.1), mild carbon ([C/Fe] = +0.7) and sodium ([Na/Fe] = +0.6) enhancement, as well as enhancement of both s-process ([Ba/Fe] = +0.8) and r-process ([Eu/Fe] = +0.5) material. The high Li abundance can be explained by self-enrichment through extra mixing mechanisms that connect the convective envelope with the outer regions of the H-burning shell. If so, HK-II 17435-00532 is the most metal-poor starin which this short-lived phase of Li enrichment has been observed. The r- and s-process material was not produced in this star but was either present in the gas from which HK-II 17435-00532 formed or was transferred to it from a more massive binary companion. Despite the current non-detection of radial velocity variations (over a time span of ∼180 days), it is possible that HK-II 17435-00532 is in a long-period binary system, similar to other stars with both r and s enrichment

GLORI (GLObal navigation satellite system Reflectometry Instrument): A New Airborne GNSS-R receiver for land surface applications

Science.gov (United States)

Motte, Erwan; Zribi, Mehrez; Fanise, Pascal

2015-04-01

collocated measurement of biomass and soil moisture ground truth in order to better characterize the instrument sensitivity to geophysical parameters. The instrument will be improved in the meanwhile including the optimization of data processing and the better integration of external data (GPS commercial receiver, Attitude) into the receiver. M.Martin-Neira. A Passive reflectometry and interferometry system (PARIS): Application to ocean altimetry. ESA J., 17:331-355, 1993 Hauser, D.; Caudal, G.; Le Gac, C.; Valentin, R.; Delaye, L.; Tison, C., "KuROS: A new airborne Ku-band Doppler radar for observation of the ocean surface," Geoscience and Remote Sensing Symposium (IGARSS), 2014 IEEE International , vol., no., pp.282,285, 13-18 July 2014 Egido, A.; Paloscia, S.; Motte, E.; Guerriero, L.; Pierdicca, N.; Caparrini, M.; Santi, E.; Fontanelli, G.; Floury, N., "Airborne GNSS-R Polarimetric Measurements for Soil Moisture and Above-Ground Biomass Estimation," Selected Topics in Applied Earth Observations and Remote Sensing, IEEE Journal of , vol.7, no.5, pp.1522,1532, May 2014

VizieR Online Data Catalog: R-band light curves of type II supernovae (Rubin+, 2016)

Science.gov (United States)

Rubin, A.; Gal-Yam, A.; De Cia, A.; Horesh, A.; Khazov, D.; Ofek, E. O.; Kulkarni, S. R.; Arcavi, I.; Manulis, I.; Yaron, O.; Vreeswijk, P.; Kasliwal, M. M.; Ben-Ami, S.; Perley, D. A.; Cao, Y.; Cenko, S. B.; Rebbapragada, U. D.; Wozniak, P. R.; Filippenko, A. V.; Clubb, K. I.; Nugent, P. E.; Pan, Y.-C.; Badenes, C.; Howell, D. A.; Valenti, S.; Sand, D.; Sollerman, J.; Johansson, J.; Leonard, D. C.; Horst, J. C.; Armen, S. F.; Fedrow, J. M.; Quimby, R. M.; Mazzali, P.; Pian, E.; Sternberg, A.; Matheson, T.; Sullivan, M.; Maguire, K.; Lazarevic, S.

2016-05-01

Our sample consists of 57 SNe from the PTF (Law et al. 2009PASP..121.1395L; Rau et al. 2009PASP..121.1334R) and the intermediate Palomar Transient Factory (iPTF; Kulkarni 2013ATel.4807....1K) surveys. Data were routinely collected by the Palomar 48-inch survey telescope in the Mould R-band. Follow-up observations were conducted mainly with the robotic 60-inch telescope using an SDSS r-band filter, with additional telescopes providing supplementary photometry and spectroscopy (see Gal-Yam et al. 2011, J/ApJ/736/159). The full list of SNe, their coordinates, and classification spectra are presented in Table 1. Most of the spectra were obtained with the Double Spectrograph on the 5m Hale telescope at Palomar Observatory, the Kast spectrograph on the Shane 3m telescope at Lick Observatory, the Low Resolution Imaging Spectrometer (LRIS) on the Keck I 10m telescope, and the DEep Imaging Multi-Object Spectrograph (DEIMOS) on the Keck II 10m telescope. (2 data files).

A satellite constellation optimization for a regional GNSS remote sensing mission

Science.gov (United States)

Gavili Kilaneh, Narin; Mashhadi Hossainali, Masoud

2017-04-01

Due to the recent advances in the Global Navigation Satellite System Remote sensing (GNSS¬R) applications, optimization of a satellite orbit to investigate the Earth's properties seems significant. The comparison of the GNSS direct and reflected signals received by a Low Earth Orbit (LEO) satellite introduces a new technique to remotely sense the Earth. Several GNSS¬R missions including Cyclone Global Navigation Satellite System (CYGNSS) have been proposed for different applications such as the ocean wind speed and height monitoring. The geometric optimization of the satellite orbit before starting the mission is a key step for every space mission. Since satellite constellation design varies depending on the application, we have focused on the required geometric criteria for oceanography applications in a specified region. Here, the total number of specular points, their spatial distribution and the accuracy of their position are assumed to be sufficient for oceanography applications. Gleason's method is used to determine the position of specular points. We considered the 2-D lattice and 3-D lattice theory of flower constellation to survey whether a circular orbit or an elliptical one is suitable to improve the solution. Genetic algorithm is implemented to solve the problem. To check the visibility condition between the LEO and GPS satellites, the satellite initial state is propagated by a variable step size numerical integration method. Constellation orbit parameters achieved by optimization provide a better resolution and precession for the specular points in the study area of this research.

Intracellular Zn(II) Intoxication Leads to Dysregulation of the PerR Regulon Resulting in Heme Toxicity in Bacillus subtilis

Science.gov (United States)

2016-01-01

Transition metal ions (Zn(II), Cu(II)/(I), Fe(III)/(II), Mn(II)) are essential for life and participate in a wide range of biological functions. Cellular Zn(II) levels must be high enough to ensure that it can perform its essential roles. Yet, since Zn(II) binds to ligands with high avidity, excess Zn(II) can lead to protein mismetallation. The major targets of mismetallation, and the underlying causes of Zn(II) intoxication, are not well understood. Here, we use a forward genetic selection to identify targets of Zn(II) toxicity. In wild-type cells, in which Zn(II) efflux prevents intoxication of the cytoplasm, extracellular Zn(II) inhibits the electron transport chain due to the inactivation of the major aerobic cytochrome oxidase. This toxicity can be ameliorated by depression of an alternate oxidase or by mutations that restrict access of Zn(II) to the cell surface. Conversely, efflux deficient cells are sensitive to low levels of Zn(II) that do not inhibit the respiratory chain. Under these conditions, intracellular Zn(II) accumulates and leads to heme toxicity. Heme accumulation results from dysregulation of the regulon controlled by PerR, a metal-dependent repressor of peroxide stress genes. When metallated with Fe(II) or Mn(II), PerR represses both heme biosynthesis (hemAXCDBL operon) and the abundant heme protein catalase (katA). Metallation of PerR with Zn(II) disrupts this coordination, resulting in depression of heme biosynthesis but continued repression of catalase. Our results support a model in which excess heme partitions to the membrane and undergoes redox cycling catalyzed by reduced menaquinone thereby resulting in oxidative stress. PMID:27935957

CISG DEL II og Værneting i UfR 1998.1092 ØLK

DEFF Research Database (Denmark)

Lookofsky, Joseph

1998-01-01

I UfR 1998.1092 ØLK anvender en dansk domstol reglerne om købsaftalers indgåelse i CISG-konventionens del II. Det sker for at afgøre, om der er værneting i Danmark efter EF-domskonventionens artikel 5, nr. 1, når sagsøgte bestrider, at der er indgået en købsaftale. Sagen sætter fokus på behovet...

Near-real-time regional troposphere models for the GNSS precise point positioning technique

International Nuclear Information System (INIS)

Hadas, T; Kaplon, J; Bosy, J; Sierny, J; Wilgan, K

2013-01-01

The GNSS precise point positioning (PPP) technique requires high quality product (orbits and clocks) application, since their error directly affects the quality of positioning. For real-time purposes it is possible to utilize ultra-rapid precise orbits and clocks which are disseminated through the Internet. In order to eliminate as many unknown parameters as possible, one may introduce external information on zenith troposphere delay (ZTD). It is desirable that the a priori model is accurate and reliable, especially for real-time application. One of the open problems in GNSS positioning is troposphere delay modelling on the basis of ground meteorological observations. Institute of Geodesy and Geoinformatics of Wroclaw University of Environmental and Life Sciences (IGG WUELS) has developed two independent regional troposphere models for the territory of Poland. The first one is estimated in near-real-time regime using GNSS data from a Polish ground-based augmentation system named ASG-EUPOS established by Polish Head Office of Geodesy and Cartography (GUGiK) in 2008. The second one is based on meteorological parameters (temperature, pressure and humidity) gathered from various meteorological networks operating over the area of Poland and surrounding countries. This paper describes the methodology of both model calculation and verification. It also presents results of applying various ZTD models into kinematic PPP in the post-processing mode using Bernese GPS Software. Positioning results were used to assess the quality of the developed models during changing weather conditions. Finally, the impact of model application to simulated real-time PPP on precision, accuracy and convergence time is discussed. (paper)

High-Precision and Low Latency RT-GNSS Processed Data for Diverse Geophysical and Natural Hazard Communities.

Science.gov (United States)

Mencin, David; Hodgkinson, Kathleen; Sievers, Charlie; David, Phillips; Charles, Meertens; Glen, Mattioli

2017-04-01

UNAVCO has been providing infrastructure and support for solid-earth sciences and earthquake natural hazards for the past two decades. Recent advances in GNSS technology and data processing are now providing position solutions with centimeter-level precision at high-rate (>1 Hz) and low latency (i.e. the time required for data to arrive for analysis, in this case less than 1 second). These data have the potential to improve our understanding in diverse areas of geophysics including properties of seismic, volcanic, magmatic and tsunami sources, and thus profoundly transform rapid event characterization and warning. Scientific and operational applications also include glacier and ice sheet motions; tropospheric modeling; and space weather. These areas of geophysics represent a spectrum of research fields, including geodesy, seismology, tropospheric weather, space weather and natural hazards. Processed Real-Time GNSS (RT-GNSS) data will require formats and standards that allow this broad and diverse community to use these data and associated meta-data in existing research infrastructure. These advances have critically highlighted the difficulties associated with merging data and metadata between scientific disciplines. Even seemingly very closely related fields such as geodesy and seismology, which both have rich histories of handling large volumes of data and metadata, do not go together well in any automated way. Community analysis strategies, or lack thereof, such as treatment of error prove difficult to address and are reflected in the data and metadata. In addition, these communities have differing security, accessibility and reliability requirements. We propose some solutions to the particular problem of making RT-GNSS processed solution data and metadata accessible to multiply scientific and natural hazard communities. Importantly, we discuss the roadblocks encounter and solved and those that remain to be addressed.

Combination of High Rate, Real-time GNSS and Accelerometer Observations - Preliminary Results Using a Shake Table and Historic Earthquake Events.

Science.gov (United States)

Jackson, Michael; Passmore, Paul; Zimakov, Leonid; Raczka, Jared

2014-05-01

One of the fundamental requirements of an Earthquake Early Warning (EEW) system (and other mission critical applications) is to quickly detect and process the information from the strong motion event, i.e. event detection and location, magnitude estimation, and the peak ground motion estimation at the defined targeted site, thus allowing the civil protection authorities to provide pre-programmed emergency response actions: Slow down or stop rapid transit trains and high-speed trains; shutoff of gas pipelines and chemical facilities; stop elevators at the nearest floor; send alarms to hospitals, schools and other civil institutions. An important question associated with the EEW system is: can we measure displacements in real time with sufficient accuracy? Scientific GNSS networks are moving towards a model of real-time data acquisition, storage integrity, and real-time position and displacement calculations. This new paradigm allows the integration of real-time, high-rate GNSS displacement information with acceleration and velocity data to create very high-rate displacement records. The mating of these two instruments allows the creation of a new, very high-rate (200 Hz) displacement observable that has the full-scale displacement characteristics of GNSS and high-precision dynamic motions of seismic technologies. It is envisioned that these new observables can be used for earthquake early warning studies and other mission critical applications, such as volcano monitoring, building, bridge and dam monitoring systems. REF TEK a Division of Trimble has developed the integrated GNSS/Accelerograph system, model 160-09SG, which consists of REF TEK's fourth generation electronics, a 147-01 high-resolution ANSS Class A accelerometer, and Trimble GNSS receiver and antenna capable of real time, on board Precise Point Positioning (PPP) techniques with satellite clock and orbit corrections delivered to the receiver directly via L-band satellite communications. The test we

Assessment calculation of MARS-LMR using EBR-II SHRT-45R

Energy Technology Data Exchange (ETDEWEB)

Choi, C.; Ha, K.S.

2016-10-15

Highlights: • Neutronic and thermal-hydraulic behavior predicted by MARS-LMR is validated with EBR-II SHRT-45R test data. • Decay heat model of ANS-94 give better prediction of the fission power. • The core power is well predicted by reactivity feedback during initial transient, however, the predicted power after approximately 200 s is over-estimated. The study of the reactivity feedback model of the EBR-II is necessary for the better calculation of the power. • Heat transfer between inter-subassemblies is the most important parameter, especially, a low flow and power subassembly, like non-fueled subassembly. - Abstract: KAERI has designed a prototype Gen-IV SFR (PGSFR) with metallic fuel. And the safety analysis code for the PGSFR, MARS-LMR, is based on the MARS code, and supplemented with various liquid metal related features including sodium properties, heat transfer, pressure drop, and reactivity feedback models. In order to validate the newly developed MARS-LMR, KAERI has joined the International Atomic Energy Agency (IAEA) coordinated research project (CRP) on “Benchmark Analysis of an EBR-II Shutdown Heat Removal Test (SHRT)”. Argonne National Laboratory (ANL) has technically supported and participated in this program. One of benchmark analysis tests is SHRT-45R, which is an unprotected loss of flow test in an EBR-II. So, sodium natural circulation and reactivity feedbacks are major phenomena of interest. A benchmark analysis was conducted using MARS-LMR with original input data provided by ANL. MARS-LMR well predicts the core flow and power change by reactivity feedbacks in the core. Except the results of the XX10, the temperature and flow in the XX09 agreed well with the experiments. Moreover, sensitivity tests were carried out for a decay heat model, reactivity feedback model, inter-subassembly heat transfer, internal heat structures and so on, to evaluate their sensitivity and get a better prediction. The decay heat model of ANS-94 shows

Assessment calculation of MARS-LMR using EBR-II SHRT-45R

International Nuclear Information System (INIS)

Choi, C.; Ha, K.S.

2016-01-01

Highlights: • Neutronic and thermal-hydraulic behavior predicted by MARS-LMR is validated with EBR-II SHRT-45R test data. • Decay heat model of ANS-94 give better prediction of the fission power. • The core power is well predicted by reactivity feedback during initial transient, however, the predicted power after approximately 200 s is over-estimated. The study of the reactivity feedback model of the EBR-II is necessary for the better calculation of the power. • Heat transfer between inter-subassemblies is the most important parameter, especially, a low flow and power subassembly, like non-fueled subassembly. - Abstract: KAERI has designed a prototype Gen-IV SFR (PGSFR) with metallic fuel. And the safety analysis code for the PGSFR, MARS-LMR, is based on the MARS code, and supplemented with various liquid metal related features including sodium properties, heat transfer, pressure drop, and reactivity feedback models. In order to validate the newly developed MARS-LMR, KAERI has joined the International Atomic Energy Agency (IAEA) coordinated research project (CRP) on “Benchmark Analysis of an EBR-II Shutdown Heat Removal Test (SHRT)”. Argonne National Laboratory (ANL) has technically supported and participated in this program. One of benchmark analysis tests is SHRT-45R, which is an unprotected loss of flow test in an EBR-II. So, sodium natural circulation and reactivity feedbacks are major phenomena of interest. A benchmark analysis was conducted using MARS-LMR with original input data provided by ANL. MARS-LMR well predicts the core flow and power change by reactivity feedbacks in the core. Except the results of the XX10, the temperature and flow in the XX09 agreed well with the experiments. Moreover, sensitivity tests were carried out for a decay heat model, reactivity feedback model, inter-subassembly heat transfer, internal heat structures and so on, to evaluate their sensitivity and get a better prediction. The decay heat model of ANS-94 shows

Stability and Unimolecular Reactivity of Palladate(II) Complexes [Ln PdR3 ]- (L=Phosphine, R=Organyl, n=0 and 1).

Science.gov (United States)

Kolter, Marlene; Koszinowski, Konrad

2016-10-24

The reduction of Pd II precatalysts to catalytically active Pd 0 species is a key step in many palladium-mediated cross-coupling reactions. Besides phosphines, the stoichiometrically used organometallic reagents can afford this reduction, but do so in a poorly understood way. To elucidate the mechanism of this reaction, we have treated solutions of Pd(OAc) 2 and a phosphine ligand L in tetrahydrofuran with RMgCl (R=Ph, Bn, Bu) as well as other organometallic reagents. Analysis of these model systems by electrospray- ionization mass spectrometry found palladate(II) complexes [L n PdR 3 ] - (n=0 and 1), thus pointing to the occurrence of transmetallation reactions. Upon gas-phase fragmentation, the [L n PdR 3 ] - anions preferentially underwent a reductive elimination to yield Pd 0 species. The sequence of the transmetallation and reductive elimination, thus, constitutes a feasible mechanism for the reduction of the Pd(OAc) 2 precatalyst. Other species of interest observed include the Pd IV complex [PdBn 5 ] - , which did not fragment via a reductive elimination but lost BnH instead. © 2016 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Accuracy assessment of Precise Point Positioning with multi-constellation GNSS data under ionospheric scintillation effects

Directory of Open Access Journals (Sweden)

Marques Haroldo Antonio

2018-01-01

Full Text Available GPS and GLONASS are currently the Global Navigation Satellite Systems (GNSS with full operational capacity. The integration of GPS, GLONASS and future GNSS constellations can provide better accuracy and more reliability in geodetic positioning, in particular for kinematic Precise Point Positioning (PPP, where the satellite geometry is considered a limiting factor to achieve centimeter accuracy. The satellite geometry can change suddenly in kinematic positioning in urban areas or under conditions of strong atmospheric effects such as for instance ionospheric scintillation that may degrade satellite signal quality, causing cycle slips and even loss of lock. Scintillation is caused by small scale irregularities in the ionosphere and is characterized by rapid changes in amplitude and phase of the signal, which are more severe in equatorial and high latitudes geomagnetic regions. In this work, geodetic positioning through the PPP method was evaluated with integrated GPS and GLONASS data collected in the equatorial region under varied scintillation conditions. The GNSS data were processed in kinematic PPP mode and the analyses show accuracy improvements of up to 60% under conditions of strong scintillation when using multi-constellation data instead of GPS data alone. The concepts and analyses related to the ionospheric scintillation effects, the mathematical model involved in PPP with GPS and GLONASS data integration as well as accuracy assessment with data collected under ionospheric scintillation effects are presented.

A Low-Cost Collaborative Location Scheme with GNSS and RFID for the Internet of Things

Directory of Open Access Journals (Sweden)

Changfeng Jing

2018-05-01

Full Text Available The emergence and development of the Internet of Things (IoT has attracted growing attention to low-cost location systems when facing the dramatically increased number of public infrastructure assets in smart cities. Various radio frequency identification (RFID-based locating systems have been developed. However, most of them are impractical for infrastructure asset inspection and management on a large scale due to their high cost, inefficient deployment, and complex environments such as emergencies or high-rise buildings. In this paper, we proposed a novel locating system by combing the Global Navigation Satellite System (GNSS with RFID, in which a target tag was located with one RFID reader and one GNSS receiver with sufficient accuracy for infrastructure asset management. To overcome the cost challenge, one mobile RFID reader-mounted GNSS receiver is used to simulate multiple location known reference tags. A vast number of reference tags are necessary for current RFID-based locating systems, which means higher cost. To achieve fine-grained location accuracy, we utilize a distance-based power law weight algorithm to estimate the exact coordinates. Our experiment demonstrates the effectiveness and advantages of the proposed scheme with sufficient accuracy, low cost and easy deployment on a large scale. The proposed scheme has potential applications for location-based services in smart cities.

Accuracy assessment of Precise Point Positioning with multi-constellation GNSS data under ionospheric scintillation effects

Science.gov (United States)

Marques, Haroldo Antonio; Marques, Heloísa Alves Silva; Aquino, Marcio; Veettil, Sreeja Vadakke; Monico, João Francisco Galera

2018-02-01

GPS and GLONASS are currently the Global Navigation Satellite Systems (GNSS) with full operational capacity. The integration of GPS, GLONASS and future GNSS constellations can provide better accuracy and more reliability in geodetic positioning, in particular for kinematic Precise Point Positioning (PPP), where the satellite geometry is considered a limiting factor to achieve centimeter accuracy. The satellite geometry can change suddenly in kinematic positioning in urban areas or under conditions of strong atmospheric effects such as for instance ionospheric scintillation that may degrade satellite signal quality, causing cycle slips and even loss of lock. Scintillation is caused by small scale irregularities in the ionosphere and is characterized by rapid changes in amplitude and phase of the signal, which are more severe in equatorial and high latitudes geomagnetic regions. In this work, geodetic positioning through the PPP method was evaluated with integrated GPS and GLONASS data collected in the equatorial region under varied scintillation conditions. The GNSS data were processed in kinematic PPP mode and the analyses show accuracy improvements of up to 60% under conditions of strong scintillation when using multi-constellation data instead of GPS data alone. The concepts and analyses related to the ionospheric scintillation effects, the mathematical model involved in PPP with GPS and GLONASS data integration as well as accuracy assessment with data collected under ionospheric scintillation effects are presented.

Ground-Based Global Navigation Satellite System (GNSS) GLONASS Broadcast Ephemeris Data (hourly files) from NASA CDDIS

Data.gov (United States)

National Aeronautics and Space Administration — This dataset consists of ground-based Global Navigation Satellite System (GNSS) GLObal NAvigation Satellite System (GLONASS) Broadcast Ephemeris Data (hourly files)...

Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

Directory of Open Access Journals (Sweden)

Yeqing Zhang

2018-02-01

Full Text Available For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully.

Low Computational Signal Acquisition for GNSS Receivers Using a Resampling Strategy and Variable Circular Correlation Time

Science.gov (United States)

Zhang, Yeqing; Wang, Meiling; Li, Yafeng

2018-01-01

For the objective of essentially decreasing computational complexity and time consumption of signal acquisition, this paper explores a resampling strategy and variable circular correlation time strategy specific to broadband multi-frequency GNSS receivers. In broadband GNSS receivers, the resampling strategy is established to work on conventional acquisition algorithms by resampling the main lobe of received broadband signals with a much lower frequency. Variable circular correlation time is designed to adapt to different signal strength conditions and thereby increase the operation flexibility of GNSS signal acquisition. The acquisition threshold is defined as the ratio of the highest and second highest correlation results in the search space of carrier frequency and code phase. Moreover, computational complexity of signal acquisition is formulated by amounts of multiplication and summation operations in the acquisition process. Comparative experiments and performance analysis are conducted on four sets of real GPS L2C signals with different sampling frequencies. The results indicate that the resampling strategy can effectively decrease computation and time cost by nearly 90–94% with just slight loss of acquisition sensitivity. With circular correlation time varying from 10 ms to 20 ms, the time cost of signal acquisition has increased by about 2.7–5.6% per millisecond, with most satellites acquired successfully. PMID:29495301

A Methodology to Assess Ionospheric Models for GNSS

Science.gov (United States)

Rovira-Garcia, Adria; Juan, José Miguel; Sanz, Jaume; González-Casado, Guillermo; Ibánez, Deimos

2015-04-01

Testing the accuracy of the ionospheric models used in the Global Navigation Satellite System (GNSS) is a long-standing issue. It is still a challenging problem due to the lack of accurate enough slant ionospheric determinations to be used as a reference. The present study proposes a methodology to assess any ionospheric model used in satellite-based applications and, in particular, GNSS ionospheric models. The methodology complements other analysis comparing the navigation based on different models to correct the code and carrier-phase observations. Specifically, the following ionospheric models are assessed: the operational models broadcast in the Global Positioning System (GPS), Galileo and the European Geostationary Navigation Overlay System (EGNOS), the post-process Global Ionospheric Maps (GIMs) from different analysis centers belonging to the International GNSS Service (IGS) and, finally, a new GIM computed by the gAGE/UPC research group. The methodology is based in the comparison between the predictions of the ionospheric model with actual unambiguous carrier-phase measurements from a global distribution of permanent receivers. The differences shall be separated into the hardware delays (a receiver constant plus a satellite constant) per data interval, e.g., a day. The condition that these Differential Code Biases (DCBs) are commonly shared throughout the world-wide network of receivers and satellites provides a global character to the assessment. This approach generalizes simple tests based on double differenced Slant Total Electron Contents (STECs) between pairs of satellites and receivers on a much local scale. The present study has been conducted during the entire 2014, i.e., the last Solar Maximum. The seasonal and latitudinal structures of the results clearly reflect the different strategies used by the different models. On one hand, ionospheric model corrections based on a grid (IGS-GIMs or EGNOS) are shown to be several times better than the models

A Robust Vehicle Localization Approach Based on GNSS/IMU/DMI/LiDAR Sensor Fusion for Autonomous Vehicles

Directory of Open Access Journals (Sweden)

Xiaoli Meng

2017-09-01

Full Text Available Precise and robust localization in a large-scale outdoor environment is essential for an autonomous vehicle. In order to improve the performance of the fusion of GNSS (Global Navigation Satellite System/IMU (Inertial Measurement Unit/DMI (Distance-Measuring Instruments, a multi-constraint fault detection approach is proposed to smooth the vehicle locations in spite of GNSS jumps. Furthermore, the lateral localization error is compensated by the point cloud-based lateral localization method proposed in this paper. Experiment results have verified the algorithms proposed in this paper, which shows that the algorithms proposed in this paper are capable of providing precise and robust vehicle localization.

A Robust Vehicle Localization Approach Based on GNSS/IMU/DMI/LiDAR Sensor Fusion for Autonomous Vehicles.

Science.gov (United States)

Meng, Xiaoli; Wang, Heng; Liu, Bingbing

2017-09-18

Precise and robust localization in a large-scale outdoor environment is essential for an autonomous vehicle. In order to improve the performance of the fusion of GNSS (Global Navigation Satellite System)/IMU (Inertial Measurement Unit)/DMI (Distance-Measuring Instruments), a multi-constraint fault detection approach is proposed to smooth the vehicle locations in spite of GNSS jumps. Furthermore, the lateral localization error is compensated by the point cloud-based lateral localization method proposed in this paper. Experiment results have verified the algorithms proposed in this paper, which shows that the algorithms proposed in this paper are capable of providing precise and robust vehicle localization.

Smart Device-Supported BDS/GNSS Real-Time Kinematic Positioning for Sub-Meter-Level Accuracy in Urban Location-Based Services.

Science.gov (United States)

Wang, Liang; Li, Zishen; Zhao, Jiaojiao; Zhou, Kai; Wang, Zhiyu; Yuan, Hong

2016-12-21

Using mobile smart devices to provide urban location-based services (LBS) with sub-meter-level accuracy (around 0.5 m) is a major application field for future global navigation satellite system (GNSS) development. Real-time kinematic (RTK) positioning, which is a widely used GNSS-based positioning approach, can improve the accuracy from about 10-20 m (achieved by the standard positioning services) to about 3-5 cm based on the geodetic receivers. In using the smart devices to achieve positioning with sub-meter-level accuracy, a feasible solution of combining the low-cost GNSS module and the smart device is proposed in this work and a user-side GNSS RTK positioning software was developed from scratch based on the Android platform. Its real-time positioning performance was validated by BeiDou Navigation Satellite System/Global Positioning System (BDS/GPS) combined RTK positioning under the conditions of a static and kinematic (the velocity of the rover was 50-80 km/h) mode in a real urban environment with a SAMSUNG Galaxy A7 smartphone. The results show that the fixed-rates of ambiguity resolution (the proportion of epochs of ambiguities fixed) for BDS/GPS combined RTK in the static and kinematic tests were about 97% and 90%, respectively, and the average positioning accuracies (RMS) were better than 0.15 m (horizontal) and 0.25 m (vertical) for the static test, and 0.30 m (horizontal) and 0.45 m (vertical) for the kinematic test.

Employing Tropospheric Numerical Weather Prediction Model for High-Precision GNSS Positioning

Science.gov (United States)

Alves, Daniele; Gouveia, Tayna; Abreu, Pedro; Magário, Jackes

2014-05-01

In the past few years is increasing the necessity of realizing high accuracy positioning. In this sense, the spatial technologies have being widely used. The GNSS (Global Navigation Satellite System) has revolutionized the geodetic positioning activities. Among the existent methods one can emphasize the Precise Point Positioning (PPP) and network-based positioning. But, to get high accuracy employing these methods, mainly in real time, is indispensable to realize the atmospheric modeling (ionosphere and troposphere) accordingly. Related to troposphere, there are the empirical models (for example Saastamoinen and Hopfield). But when highly accuracy results (error of few centimeters) are desired, maybe these models are not appropriated to the Brazilian reality. In order to minimize this limitation arises the NWP (Numerical Weather Prediction) models. In Brazil the CPTEC/INPE (Center for Weather Prediction and Climate Studies / Brazilian Institute for Spatial Researches) provides a regional NWP model, currently used to produce Zenithal Tropospheric Delay (ZTD) predictions (http://satelite.cptec.inpe.br/zenital/). The actual version, called eta15km model, has a spatial resolution of 15 km and temporal resolution of 3 hours. In this paper the main goal is to accomplish experiments and analysis concerning the use of troposphere NWP model (eta15km model) in PPP and network-based positioning. Concerning PPP it was used data from dozens of stations over the Brazilian territory, including Amazon forest. The results obtained with NWP model were compared with Hopfield one. NWP model presented the best results in all experiments. Related to network-based positioning it was used data from GNSS/SP Network in São Paulo State, Brazil. This network presents the best configuration in the country to realize this kind of positioning. Actually the network is composed by twenty stations (http://www.fct.unesp.br/#!/pesquisa/grupos-de-estudo-e-pesquisa/gege//gnss-sp-network2789/). The

Ground-Based Global Navigation Satellite System (GNSS) GPS Broadcast Ephemeris Data (daily files) from NASA CDDIS

Data.gov (United States)

National Aeronautics and Space Administration — This dataset consists of ground-based Global Navigation Satellite System (GNSS) GPS Broadcast Ephemeris Data (daily files) from the NASA Crustal Dynamics Data...

Stalled RNAP-II molecules bound to non-coding rDNA spacers are required for normal nucleolus architecture.

Science.gov (United States)

Freire-Picos, M A; Landeira-Ameijeiras, V; Mayán, María D

2013-07-01

The correct distribution of nuclear domains is critical for the maintenance of normal cellular processes such as transcription and replication, which are regulated depending on their location and surroundings. The most well-characterized nuclear domain, the nucleolus, is essential for cell survival and metabolism. Alterations in nucleolar structure affect nuclear dynamics; however, how the nucleolus and the rest of the nuclear domains are interconnected is largely unknown. In this report, we demonstrate that RNAP-II is vital for the maintenance of the typical crescent-shaped structure of the nucleolar rDNA repeats and rRNA transcription. When stalled RNAP-II molecules are not bound to the chromatin, the nucleolus loses its typical crescent-shaped structure. However, the RNAP-II interaction with Seh1p, or cryptic transcription by RNAP-II, is not critical for morphological changes. Copyright © 2013 John Wiley & Sons, Ltd.

AATR an ionospheric activity indicator specifically based on GNSS measurements

Science.gov (United States)

Juan, José Miguel; Sanz, Jaume; Rovira-Garcia, Adrià; González-Casado, Guillermo; Ibáñez, D.; Perez, R. Orus

2018-03-01

This work reviews an ionospheric activity indicator useful for identifying disturbed periods affecting the performance of Global Navigation Satellite System (GNSS). This index is based in the Along Arc TEC Rate (AATR) and can be easily computed from dual-frequency GNSS measurements. The AATR indicator has been assessed over more than one Solar Cycle (2002-2017) involving about 140 receivers distributed world-wide. Results show that it is well correlated with the ionospheric activity and, unlike other global indicators linked to the geomagnetic activity (i.e. DST or Ap), it is sensitive to the regional behaviour of the ionosphere and identifies specific effects on GNSS users. Moreover, from a devoted analysis of different Satellite Based Augmentation System (SBAS) performances in different ionospheric conditions, it follows that the AATR indicator is a very suitable mean to reveal whether SBAS service availability anomalies are linked to the ionosphere. On this account, the AATR indicator has been selected as the metric to characterise the ionosphere operational conditions in the frame of the European Space Agency activities on the European Geostationary Navigation Overlay System (EGNOS). The AATR index has been adopted as a standard tool by the International Civil Aviation Organization (ICAO) for joint ionospheric studies in SBAS. In this work we explain how the AATR is computed, paying special attention to the cycle-slip detection, which is one of the key issues in the AATR computation, not fully addressed in other indicators such as the Rate Of change of the TEC Index (ROTI). After this explanation we present some of the main conclusions about the ionospheric activity that can extracted from the AATR values during the above mentioned long-term study. These conclusions are: (a) the different spatial correlation related with the MOdified DIP (MODIP) which allows to clearly separate high, mid and low latitude regions, (b) the large spatial correlation in mid

The new DMT SAFEGUARD low-cost GNSS measuring system and its application in the field of geotechnical deformation and movement monitoring

Science.gov (United States)

Schröder, Daniel

2017-04-01

In the recent years an increasing awareness of geodetic measurement systems and their application for monitoring projects is clearly visible. With geodetic sensors it is possible to detect safety-related changes at monitoring objects with high temporal density, high accuracy and in a very reliable manner. Quality acquisitions, processing and storage of monitoring data as well as a professional on-site implementation are the most important requirements and challenges to contemporary systems in civil engineering, mining as well as oil and gas production. Monitoring measures provide important input for early warning, alarm, protection and verification of potential hazardous environments and therefore the risk management applied to projects have a significant influence. The implementation has to follow an optimization process incorporating necessary accuracy, reliability and economic efficiency. From the economical point of view the costs per observation point are crucial for most monitoring projects. Keeping in mind that the costs of classical high-end GNSS stations with a geodetic dual-frequency receiver is within the range of several 10,000 euro. Large monitoring networks with a high number of simultaneously observed points are very expensive and therefore eventually have to be cut back, substituted by compromising methods or totally withdrawn. A further development in the area of GNSS receivers could reduce this disadvantage. Within the last few years single-frequency receivers that record L1-signals of GPS/GLONASS and offer sub-centimeter positioning accuracies are increasingly offered on the market. The accuracy of GNSS measurements depends on many factors as the hardware itself as well as on external influences related to the measurement principals. The external influences can be strongly reduced or eliminated by appropriate measuring and processing methods. For a reliable monitoring system it is necessary that the results are comparable and consistent for each

Atucha II NPP full scope simulator modelling with the thermal hydraulic code TRAC{sub R}T

Energy Technology Data Exchange (ETDEWEB)

Alonso, Pablo Rey; Ruiz, Jose Antonio; Rivero, Norberto, E-mail: prey@tecnatom.e, E-mail: jaruiz@tecnatom.e, E-mail: nrivero@tecnatom.e [Tecnatom S.A., Madrid (Spain)

2011-07-01

In February 2010 NA-SA (Nucleoelectrica Argentina S.A.) awarded Tecnatom the Atucha II full scope simulator project. NA-SA is a public company owner of the Argentinean nuclear power plants. Atucha II is due to enter in operation shortly. Atucha II NPP is a PHWR type plant cooled by the water of the Parana River and has the same design as the Atucha I unit, doubling its power capacity. Atucha II will produce 745 MWe utilizing heavy water as coolant and moderator, and natural uranium as fuel. A plant singular feature is the permanent core refueling. TRAC{sub R}T is the first real time thermal hydraulic six-equations code used in the training simulation industry for NSSS modeling. It is the result from adapting to real time the best estimate code TRACG. TRAC{sub R}T is based on first principle conservation equations for mass, energy and momentum for liquid and steam phases, with two phase flows under non homogeneous and non equilibrium conditions. At present, it has been successfully implemented in twelve full scope replica simulators in different training centers throughout the world. To ease the modeling task, TRAC{sub R}T includes a graphical pre-processing tool designed to optimize this process and alleviate the burden of entering alpha numerical data in an input file. (author)

Smart Device-Supported BDS/GNSS Real-Time Kinematic Positioning for Sub-Meter-Level Accuracy in Urban Location-Based Services

Directory of Open Access Journals (Sweden)

Liang Wang

2016-12-01

Full Text Available Using mobile smart devices to provide urban location-based services (LBS with sub-meter-level accuracy (around 0.5 m is a major application field for future global navigation satellite system (GNSS development. Real-time kinematic (RTK positioning, which is a widely used GNSS-based positioning approach, can improve the accuracy from about 10–20 m (achieved by the standard positioning services to about 3–5 cm based on the geodetic receivers. In using the smart devices to achieve positioning with sub-meter-level accuracy, a feasible solution of combining the low-cost GNSS module and the smart device is proposed in this work and a user-side GNSS RTK positioning software was developed from scratch based on the Android platform. Its real-time positioning performance was validated by BeiDou Navigation Satellite System/Global Positioning System (BDS/GPS combined RTK positioning under the conditions of a static and kinematic (the velocity of the rover was 50–80 km/h mode in a real urban environment with a SAMSUNG Galaxy A7 smartphone. The results show that the fixed-rates of ambiguity resolution (the proportion of epochs of ambiguities fixed for BDS/GPS combined RTK in the static and kinematic tests were about 97% and 90%, respectively, and the average positioning accuracies (RMS were better than 0.15 m (horizontal and 0.25 m (vertical for the static test, and 0.30 m (horizontal and 0.45 m (vertical for the kinematic test.

An Adaptive Low-Cost INS/GNSS Tightly-Coupled Integration Architecture Based on Redundant Measurement Noise Covariance Estimation.

Science.gov (United States)

Li, Zheng; Zhang, Hai; Zhou, Qifan; Che, Huan

2017-09-05

The main objective of the introduced study is to design an adaptive Inertial Navigation System/Global Navigation Satellite System (INS/GNSS) tightly-coupled integration system that can provide more reliable navigation solutions by making full use of an adaptive Kalman filter (AKF) and satellite selection algorithm. To achieve this goal, we develop a novel redundant measurement noise covariance estimation (RMNCE) theorem, which adaptively estimates measurement noise properties by analyzing the difference sequences of system measurements. The proposed RMNCE approach is then applied to design both a modified weighted satellite selection algorithm and a type of adaptive unscented Kalman filter (UKF) to improve the performance of the tightly-coupled integration system. In addition, an adaptive measurement noise covariance expanding algorithm is developed to mitigate outliers when facing heavy multipath and other harsh situations. Both semi-physical simulation and field experiments were conducted to evaluate the performance of the proposed architecture and were compared with state-of-the-art algorithms. The results validate that the RMNCE provides a significant improvement in the measurement noise covariance estimation and the proposed architecture can improve the accuracy and reliability of the INS/GNSS tightly-coupled systems. The proposed architecture can effectively limit positioning errors under conditions of poor GNSS measurement quality and outperforms all the compared schemes.

The use of vertical and horizontal surface displacements at EPOS GNSS stations in Greenland to study ice sheet mass balance

DEFF Research Database (Denmark)

Khan, Shfaqat Abbas

2014-01-01

The European Plate Observing System (EPOS) includes e.g. seismic and geodetic permanent national monitoring networks on a European scale. The main purpose is to create data platforms for monitoring and study geophysics processes like earthquakes, volcanoes, surface dynamics and tectonics. Here we...... present data from arctic GNSS stations included in the EPOS network. The arctic EPOS GNSS network consists of 16 continuous GPS stations spread across Greenland. This network is able to map the velocity fields associated with, plate motion, postglacial rebound and improve our understanding of tectonic...

INS/GNSS Integration for Aerobatic Flight Applications and Aircraft Motion Surveying.

Science.gov (United States)

V Hinüber, Edgar L; Reimer, Christian; Schneider, Tim; Stock, Michael

2017-04-26

This paper presents field tests of challenging flight applications obtained with a new family of lightweight low-power INS/GNSS ( inertial navigation system/global satellite navigation system ) solutions based on MEMS ( micro-electro-mechanical- sensor ) machined sensors, being used for UAV ( unmanned aerial vehicle ) navigation and control as well as for aircraft motion dynamics analysis and trajectory surveying. One key is a 42+ state extended Kalman-filter-based powerful data fusion, which also allows the estimation and correction of parameters that are typically affected by sensor aging, especially when applying MEMS-based inertial sensors, and which is not yet deeply considered in the literature. The paper presents the general system architecture, which allows iMAR Navigation the integration of all classes of inertial sensors and GNSS ( global navigation satellite system ) receivers from very-low-cost MEMS and high performance MEMS over FOG ( fiber optical gyro ) and RLG ( ring laser gyro ) up to HRG ( hemispherical resonator gyro ) technology, and presents detailed flight test results obtained under extreme flight conditions. As a real-world example, the aerobatic maneuvers of the World Champion 2016 (Red Bull Air Race) are presented. Short consideration is also given to surveying applications, where the ultimate performance of the same data fusion, but applied on gravimetric surveying, is discussed.

Robust cubature Kalman filter for GNSS/INS with missing observations and colored measurement noise.

Science.gov (United States)

Cui, Bingbo; Chen, Xiyuan; Tang, Xihua; Huang, Haoqian; Liu, Xiao

2018-01-01

In order to improve the accuracy of GNSS/INS working in GNSS-denied environment, a robust cubature Kalman filter (RCKF) is developed by considering colored measurement noise and missing observations. First, an improved cubature Kalman filter (CKF) is derived by considering colored measurement noise, where the time-differencing approach is applied to yield new observations. Then, after analyzing the disadvantages of existing methods, the measurement augment in processing colored noise is translated into processing the uncertainties of CKF, and new sigma point update framework is utilized to account for the bounded model uncertainties. By reusing the diffused sigma points and approximation residual in the prediction stage of CKF, the RCKF is developed and its error performance is analyzed theoretically. Results of numerical experiment and field test reveal that RCKF is more robust than CKF and extended Kalman filter (EKF), and compared with EKF, the heading error of land vehicle is reduced by about 72.4%. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Pseudoknot in domain II of 23 S rRNA is essential for ribosome function

DEFF Research Database (Denmark)

Rosendahl, G; Hansen, L H; Douthwaite, S

1995-01-01

The structure of domain II in all 23 S (and 23 S-like) rRNAs is constrained by a pseudoknot formed between nucleotides 1005 and 1138, and between 1006 and 1137 (Escherichia coli numbering). These nucleotides are exclusively conserved as 1005C.1138G and 1006C.1137G pairs in all Bacteria, Archaea...... increased accessibility in the rRNA structure close to the sites of the mutations. The degree to which the mutations increase rRNA accessibility correlates with the severity of their phenotypic effects. Nucleotide 1131G is extremely reactive to dimethyl sulphate modification in wild-type subunits...

TYPE Ia SNe ALONG REDSHIFT: THE R(Si II) RATIO AND THE EXPANSION VELOCITIES IN INTERMEDIATE-z SUPERNOVAE

International Nuclear Information System (INIS)

Altavilla, G.; Ruiz-Lapuente, P.; Balastegui, A.; Mendez, J.; Espana-Bonet, C.; Irwin, M.; Ellis, R. S.; McMahon, R. M.; Walton, N. A.; Folatelli, G.; Goobar, A.; Nobili, S.; Stanishev, V.; Hillebrandt, W.

2009-01-01

We present a study of intermediate-z Type Ia supernovae (SNe Ia) using empirical physical diagrams which permit the investigation of those SNe explosions. This information can be very useful to reduce systematic uncertainties of the Hubble diagram of SNe Ia up to high z. The study of the expansion velocities and the measurement of the ratio R(Si II) allow subtyping of SNe Ia as done in nearby samples. The evolution of this ratio as seen in the diagram R(Si II)-(t) together with R(Si II) max versus (B - V) 0 indicates consistency of the properties at intermediate-z compared with the nearby SNe Ia. At intermediate-z, expansion velocities of Ca II and Si II are found similar to those of the nearby sample. This is found in a sample of six SNe Ia in the range 0.033 ≤z≤ 0.329 discovered within the International Time Programme of SNe Ia for Cosmology and Physics in the spring run of 2002. 7 The program run under Omega and Lambda from Supernovae and the Physics of Supernova Explosions within the International Time Programme at the telescopes of the European Northern Observatory (ENO) at La Palma (Canary Islands, Spain). Two SNe Ia at intermediate-z were of the cool FAINT type, one being an SN1986G-like object highly reddened. The R(Si II) ratio as well as subclassification of the SNe Ia beyond templates help to place SNe Ia in their sequence of brightness and to distinguish between reddened and intrinsically red supernovae. This test can be done with very high z SNe Ia and it will help to reduce systematic uncertainties due to extinction by dust. It should allow to map the high-z sample into the nearby one.

PROGRAMA CIENTÍFICO PARA O MONITORAMENTO EM TEMPO REAL OU PÓS-PROCESSADO DAS IRREGULARIDADES IONOSFÉRICAS E CINTILAÇÃO DOS SINAIS GNSS

Directory of Open Access Journals (Sweden)

Vinícius Amadeu Stuani Pereira

Full Text Available O Brasil é um dos países que mais sofrem os efeitos provocados pela ionosfera, principalmente os oriundos da Anomalia de Ionização Equatorial, irregularidades ionosféricas e cintilação dos sinais GNSS (Global Navigation Satellite System. Várias estratégias podem ser utilizadas para minimizar os efeitos, tais como: modelos ionosféricos, arquivos IONEX ou a combinação linear ion-free. Em se tratando do monitoramento da ionosfera a situação é diferente. A quantidade de instrumentos dedicados ao estudo da camada ionosférica é reduzida no âmbito brasileiro. Neste contexto foi desenvolvido o programa científico denominado Ion_Index, com objetivo de estimar indicadores dos níveis de irregularidades da ionosfera e de cintilação dos sinais GNSS em tempo real ou pós-processado, utilizando a infraestrutura já existente de dados GNSS de redes ativas públicas, como a RBMC, a GNSS-SP e a CALIBRA, transformando assim estações GNSS em estações monitoras da camada ionosférica. Dessa forma é proporcionado um aumento na resolução espacial das informações sobre o comportamento da ionosfera na região brasileira, permitindo um melhor entendimento e contribuindo para o desenvolvimento ou aprimoramento de modelos de mitigação. Experimentos utilizando dados de ionossondas digitais e de receptores PolaRxS-PRO da Septentrio (fontes externas comprovam a eficiência do programa

Micromegas R&D for ATLAS MUON PHASE II Upgrade

CERN Document Server

Farina, Edoardo Maria; The ATLAS collaboration

2017-01-01

In the framework of the ATLAS Phase II Upgrade, a proposal to extend the detector acceptance of the muon system to high η has been put forward (namely up to | η| ~ 4). Extension of the muon coverage has been demonstrated to enhance physics performance. The proposed location for the new detector is in between the end-cap calorimeter cryostat and the JD shielding; in this region there is no magnetic field applied, the aim of the new detector is therefore to only tag muons without performing any momentum measurement. The new η tagger should cope with extremely high particle rate, that has been calculated, by means of simulations, to be 9 MHz at R = 25 cm and 0.4 MHz at R = 60 cm for μ = 200, where μ stands for the number of pp collisions per bunch crossing. The required spatial resolution at the inner edge of the detector has been estimated in few hundreds micrometres. One of the most promising candidate technology for the new detector is the MicroMegaS one, which has already been adopted for the NSW upgrad...

Ang II-AT2R increases mesenchymal stem cell migration by signaling through the FAK and RhoA/Cdc42 pathways in vitro.

Science.gov (United States)

Xu, Xiu-Ping; He, Hong-Li; Hu, Shu-Ling; Han, Ji-Bin; Huang, Li-Li; Xu, Jing-Yuan; Xie, Jian-Feng; Liu, Ai-Ran; Yang, Yi; Qiu, Hai-Bo

2017-07-12

Mesenchymal stem cells (MSCs) migrate via the bloodstream to sites of injury and are possibly attracted by inflammatory factors. As a proinflammatory mediator, angiotensin II (Ang II) reportedly enhances the migration of various cell types by signaling via the Ang II receptor in vitro. However, few studies have focused on the effects of Ang II on MSC migration and the underlying mechanisms. Human bone marrow MSCs migration was measured using wound healing and Boyden chamber migration assays after treatments with different concentrations of Ang II, an AT1R antagonist (Losartan), and/or an AT2R antagonist (PD-123319). To exclude the effect of proliferation on MSC migration, we measured MSC proliferation after stimulation with the same concentration of Ang II. Additionally, we employed the focal adhesion kinase (FAK) inhibitor PF-573228, RhoA inhibitor C3 transferase, Rac1 inhibitor NSC23766, or Cdc42 inhibitor ML141 to investigate the role of cell adhesion proteins and the Rho-GTPase protein family (RhoA, Rac1, and Cdc42) in Ang II-mediated MSC migration. Cell adhesion proteins (FAK, Talin, and Vinculin) were detected by western blot analysis. The Rho-GTPase family protein activities were assessed by G-LISA and F-actin levels, which reflect actin cytoskeletal organization, were detected by using immunofluorescence. Human bone marrow MSCs constitutively expressed AT1R and AT2R. Additionally, Ang II increased MSC migration in an AT2R-dependent manner. Notably, Ang II-enhanced migration was not mediated by Ang II-mediated cell proliferation. Interestingly, Ang II-enhanced migration was mediated by FAK activation, which was critical for the formation of focal contacts, as evidenced by increased Talin and Vinculin expression. Moreover, RhoA and Cdc42 were activated by FAK to increase cytoskeletal organization, thus promoting cell contraction. Furthermore, FAK, Talin, and Vinculin activation and F-actin reorganization in response to Ang II were prevented by PD-123319 but

Autoregressive Processes in Homogenization of GNSS Tropospheric Data

Science.gov (United States)

Klos, A.; Bogusz, J.; Teferle, F. N.; Bock, O.; Pottiaux, E.; Van Malderen, R.

2016-12-01

Offsets due to changes in hardware equipment or any other artificial event are all a subject of a task of homogenization of tropospheric data estimated within a processing of Global Navigation Satellite System (GNSS) observables. This task is aimed at identifying exact epochs of offsets and estimate their magnitudes since they may artificially under- or over-estimate trend and its uncertainty delivered from tropospheric data and used in climate studies. In this research, we analysed a common data set of differences of Integrated Water Vapour (IWV) from GPS and ERA-Interim (1995-2010) provided for a homogenization group working within ES1206 COST Action GNSS4SWEC. We analysed daily IWV records of GPS and ERA-Interim in terms of trend, seasonal terms and noise model with Maximum Likelihood Estimation in Hector software. We found that this data has a character of autoregressive process (AR). Basing on this analysis, we performed Monte Carlo simulations of 25 years long data with two different noise types: white as well as combination of white and autoregressive and also added few strictly defined offsets. This synthetic data set of exactly the same character as IWV from GPS and ERA-Interim was then subjected to a task of manual and automatic/statistical homogenization. We made blind tests and detected possible epochs of offsets manually. We found that simulated offsets were easily detected in series with white noise, no influence of seasonal signal was noticed. The autoregressive series were much more problematic when offsets had to be determined. We found few epochs, for which no offset was simulated. This was mainly due to strong autocorrelation of data, which brings an artificial trend within. Due to regime-like behaviour of AR it is difficult for statistical methods to properly detect epochs of offsets, which was previously reported by climatologists.

Upper bounds of deformation in the Upper Rhine Graben from GPS data - First results from GURN (GNSS Upper Rhine Graben Network)

Science.gov (United States)

Masson, Frederic; Knoepfler, Andreas; Mayer, Michael; Ulrich, Patrice; Heck, Bernhard

2010-05-01

In September 2008, the Institut de Physique du Globe de Strasbourg (Ecole et Observatoire des Sciences de la Terre, EOST) and the Geodetic Institute (GIK) of Karlsruhe University (TH) established a transnational cooperation called GURN (GNSS Upper Rhine Graben Network). Within the GURN initiative these institutions are cooperating in order to establish a highly precise and highly sensitive network of permanently operating GNSS sites for the detection of crustal movements in the Upper Rhine Graben region. At the beginning, the network consisted of the permanently operating GNSS sites of SAPOS®-Baden-Württemberg, different data providers in France (e.g. EOST, Teria, RGP) and some further sites (e.g. IGS). In July 2009, the network was extended to the South when swisstopo (Switzerland) and to the North when SAPOS®-Rheinland-Pfalz joined GURN. Therefore, actually the GNSS network consists of approx. 80 permanently operating reference sites. The presentation will discuss the actual status of GURN, main research goals, and will present first results concerning the data quality as well as time series of a first reprocessing of all available data since 2002 using GAMIT/GLOBK (EOST working group) and the Bernese GPS Software (GIK working group). Based on these time series, the velocity as well as strain fields will be calculated in the future. The GURN initiative is also aiming for the estimation of the upper bounds of deformation in the Upper Rhine Graben region.

Studying the active deformation of distributed plate boundaries by integration of GNSS networks

Science.gov (United States)

D'Agostino, Nicola; Avallone, Antonio; Cecere, Gianpaolo; D'Anastasio, Elisabetta

2013-04-01

In the last decade GNSS networks installed for different purposes have proliferated in Italy and now provide a large amount of data available to geophysical studies. In addition to the existing regional and nation-wide scientific GNSS networks developed by ASI (http://geodaf.mt.asi.it), INGV (http://ring.gm.ingv.it) and OGS (http://crs.inogs.it/frednet), a large number (> 400) of continuously-operating GPS stations have been installed in the framework of regional and national networks, both publicly-operated and commercial, developed to provide real-time positioning capability to surveyors. Although the quality of the data and metadata associated to these stations is generally lower with respect to the "scientific" CGPS stations, the increased density and redundancy in crustal motion information, resulting in more than 500 stations with more than 2.5 years of observations, significantly increase the knowledge of the active deformation of the Italian territory and provides a unique image of the crustal deformation field. The obtained GPS velocity field is analysed and various features ranging from the definition of strain distribution and microplate kinematics within the plate boundary, to the evaluation of tectonic strain accumulation on active faults are presented in this work. Undeforming, aseismic regions (Sardinia, Southern Apulia) provide test sites to evaluate the lower bound on the accuracy achievable to measure tectonic deformation. Integration of GNSS networks significantly improves the resolution of the strain rate field in Central Italy showing that active deformation is concentrated in a narrow belt along the crest of the Apennines, consistently with the distribution of the largest historical and recent earthquakes. Products derived from dense GPS velocity and strain rate fields include map of earthquake potential developed under the assumption that the rate of seismic moment accumulation measured from geodesy distributes into earthquake sizes that

First results of registering ionospheric disturbances obtained with SibNet network of GNSS receivers in active space experiments

Science.gov (United States)

Ishin, Artem; Perevalova, Natalia; Voeykov, Sergey; Khakhinov, Vitaliy

2017-12-01

Global and regional networks of GNSS receivers have been successfully used for geophysical research for many years; the number of continuous GNSS stations in the world is steadily growing. The article presents the first results of the use of a new regional network of GNSS stations (SibNet) in active space experiments. The Institute of Solar-Terrestrial Physics of Siberian Branch of Russian Academy of Sciences (ISTP SB RAS) has established this network in the South Baikal region. We describe in detail SibNet, characteristics of receivers in use, parameters of antennas and methods of their installation. We also present the general structure of observation site and the plot of coverage of the receiver operating zone at 50-55° latitudes by radio paths. It is shown that the selected location of receivers allows us to detect ionospheric irregularities of various scales. The purpose of the active space experiments was to reveal and record parameters of the ionospheric irregu larities caused by effects from jet streams of Progress cargo spacecraft. The mapping technique enabled us to identify weak, vertically localized ionospheric irregularities and associate them with the Progress spacecraft engine impact. Thus, it has been shown that SibNet deployed in the Southern Baikal region is an effective instrument for monitoring ionospheric conditions.

Gasdynamics of H II regions. V. The interaction of weak R ionization fronts with dense clouds

Energy Technology Data Exchange (ETDEWEB)

Tenorio-Tagle, G; Bedijn, P J

1981-06-01

The interaction of weak R-type ionization fronts with a density enhancement is calculated numerically as a function of time within the framework of the champagne model of the evolution of H II regions. Calculations are performed under the assumption of plane-parallel geometry for various relative densities of the cloud in which the exciting star is formed and a second cloud with which an ionization front from the first cloud interacts. The supersonic ionization front representing the outer boundary of an H II region experiencing the champagne phase is found to either evolve into a D-type front or remain of type R, depending on the absolute number of photons leaving the H II region that undergoes the champagne phase. Recombinations in the ionized gas eventually slow the ionization front, however photon fluxes allow it to speed up again, resulting in oscillatory propagation of the front. Front-cloud interactions are also shown to lead to the development of a backward-facing shock, a forward-facing shock, and a density maximum in the ionized gas. The results can be used to explain the origin of bright rims in H II regions.

II Meeting of R and D in radioactive waste management, Madrid 14-16 June, 1995

International Nuclear Information System (INIS)

1995-01-01

The second meeting of R and D in radioactive waste management was organized by ENRESA on 14-16 June 1995 The main objective was to disseminate the most relevant works within the 2nd R and d plan, and to establish and adequate form involved for discussion R and D radioactive waste management. The meeting was articulated in 50 sessions: I.- Low and medium radioactive wastes. II.- High level radioactive wastes: activities of ENRESA III.- High level radioactive wastes: near field. IV.- Biosphere, radiological protection, behaviour evaluation. V.- Dismantling and decommissioning nuclear facilities VI.- Geosphere

Seizures induced in immature rats by homocysteic acid and the associated brain damage are prevented by group II metabotropic glutamate receptor agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate.

Science.gov (United States)

Folbergrová, Jaroslava; Druga, Rastislav; Otáhal, Jakub; Haugvicová, Renata; Mares, Pavel; Kubová, Hana

2005-04-01

The present study has examined the anticonvulsant and neuroprotective effect of group II metabotropic glutamate receptor (mGluR) agonist (2R,4R)-4-aminopyrrolidine-2,4-dicarboxylate (2R,4R-APDC) in the model of seizures induced in immature 12-day-old rats by bilateral intracerebroventricular infusion of dl-homocysteic acid (DL-HCA, 600 nmol/side). For biochemical analyses, rat pups were sacrificed during generalized clonic-tonic seizures, approximately 45-50 min after infusion. Comparable time intervals were used for sacrificing the pups which had received 2R,4R-APDC. Low doses of 2R,4R-APDC (0.05 nmol/side) provided a pronounced anticonvulsant effect which was abolished by pretreatment with a selective group II mGluR antagonist LY341495. Generalized clonic-tonic seizures were completely suppressed and cortical energy metabolite changes which normally accompany these seizures were either normalized (decrease of glucose and glycogen) or markedly reduced (an accumulation of lactate). EEG recordings support the marked anticonvulsant effect of 2R,4R-APDC, nevertheless, this was only partial. In spite of the absence of obvious motor phenomena, isolated spikes or even short periods of partial ictal activity could be observed. Isolated spikes could also be seen in some animals after application of 2R,4R-APDC alone, reflecting most likely subclinical proconvulsant activity of this agonist. The neuroprotective effect of 2R,4R-APDC was evaluated after 24 h and 6 days of survival following DL-HCA-induced seizures. Massive neuronal degeneration, as revealed by Fluoro-Jade B staining, was observed in a number of brain regions following infusion of DL-HCA alone (seizure group), whereas 2R,4R-APDC pretreatment provided substantial neuroprotection. The present findings support the possibility that group II mGluRs are a promising target for a novel approach to treating epilepsy.

Auto Guided Oil Palm Planter by using multi-GNSS

International Nuclear Information System (INIS)

Aini, I Nur; Aimrun W; Amin, M S M; Ezrin, M H; Shafri, H Z

2014-01-01

Planting is one of the most important operations in plantation because it could affect the total area of productivity since it is the starting point in cultivation. In oil palm plantation, lining and spacing of oil palm shall be laid out and coincided with the topographic area and a system of drains. Conventionally, planting of oil palm will require the polarization process in order to prevent and overcome the lack of influence of the sun rise and get a regular crop row. Polarization is done after the completion of the opening area by using the spike wood with 1 m length painted at the top and 100 m length of wire. This process will generally require at least five persons at a time to pull the wire and carry the spikes while the other two persons will act as observer and spikes craftsmen respectively with the ability of the team is 3ha/day. Therefore, the aim of this project is to develop the oil palm planting technique by using multi- GNSS (Global Navigation Satellite System). Generally, this project will involve five main steps mainly; design of planting pattern by using SOLIDWORKS software, determine the boundary coordinate of planting area, georeference process with ArcGIS, stakeout process with Tracy software and finally marking up the location with the wooden spikes. The results proved that the multi- GNSS is capable to provide the high accuracy with less than 1 m in precise positioning system without augmentation data. With the ability of one person, time taken to complete 70 m × 50 m planting area is 290 min, which is 25 min faster than using GPS (Global Positioning System) only

The Role of miR-330-3p/PKC-α Signaling Pathway in Low-Dose Endothelial-Monocyte Activating Polypeptide-II Increasing the Permeability of Blood-Tumor Barrier

Directory of Open Access Journals (Sweden)

Jiahui Liu

2017-12-01

Full Text Available This study was performed to determine whether EMAP II increases the permeability of the blood-tumor barrier (BTB by affecting the expression of miR-330-3p as well as its possible mechanisms. We determined the over-expression of miR-330-3p in glioma microvascular endothelial cells (GECs by Real-time PCR. Endothelial monocyte-activating polypeptide-II (EMAP-II significantly decreased the expression of miR-330-3p in GECs. Pre-miR-330-3p markedly decreased the permeability of BTB and increased the expression of tight junction (TJ related proteins ZO-1, occludin and claudin-5, however, anti-miR-330-3p had the opposite effects. Anti-miR-330-3p could enhance the effect of EMAP-II on increasing the permeability of BTB, however, pre-miR-330-3p partly reversed the effect of EMAP-II on that. Similarly, anti-miR-330-3p improved the effects of EMAP-II on increasing the expression levels of PKC-α and p-PKC-α in GECs and pre-miR-330-3p partly reversed the effects. MiR-330-3p could target bind to the 3′UTR of PKC-α. The results of in vivo experiments were similar to those of in vitro experiments. These suggested that EMAP-II could increase the permeability of BTB through inhibiting miR-330-3p which target negative regulation of PKC-α. Pre-miR-330-3p and PKC-α inhibitor decreased the BTB permeability and up-regulated the expression levels of ZO-1, occludin and claudin-5 while anti-miR-330-3p and PKC-α activator brought the reverse effects. Compared with EMAP-II, anti-miR-330-3p and PKC-α activator alone, the combination of the three combinations significantly increased the BTB permeability. EMAP-II combined with anti-miR-330-3p and PKCα activator could enhance the DOX’s effects on inhibiting the cell viabilities and increasing the apoptosis of U87 glioma cells. Our studies suggest that low-dose EMAP-II up-regulates the expression of PKC-α and increases the activity of PKC-α by inhibiting the expression of miR-330-3p, reduces the expression of ZO-1

LiDAR Scan Matching Aided Inertial Navigation System in GNSS-Denied Environments.

Science.gov (United States)

Tang, Jian; Chen, Yuwei; Niu, Xiaoji; Wang, Li; Chen, Liang; Liu, Jingbin; Shi, Chuang; Hyyppä, Juha

2015-07-10

A new scan that matches an aided Inertial Navigation System (INS) with a low-cost LiDAR is proposed as an alternative to GNSS-based navigation systems in GNSS-degraded or -denied environments such as indoor areas, dense forests, or urban canyons. In these areas, INS-based Dead Reckoning (DR) and Simultaneous Localization and Mapping (SLAM) technologies are normally used to estimate positions as separate tools. However, there are critical implementation problems with each standalone system. The drift errors of velocity, position, and heading angles in an INS will accumulate over time, and on-line calibration is a must for sustaining positioning accuracy. SLAM performance is poor in featureless environments where the matching errors can significantly increase. Each standalone positioning method cannot offer a sustainable navigation solution with acceptable accuracy. This paper integrates two complementary technologies-INS and LiDAR SLAM-into one navigation frame with a loosely coupled Extended Kalman Filter (EKF) to use the advantages and overcome the drawbacks of each system to establish a stable long-term navigation process. Static and dynamic field tests were carried out with a self-developed Unmanned Ground Vehicle (UGV) platform-NAVIS. The results prove that the proposed approach can provide positioning accuracy at the centimetre level for long-term operations, even in a featureless indoor environment.

Universality and Realistic Extensions to the Semi-Analytic Simulation Principle in GNSS Signal Processing

Directory of Open Access Journals (Sweden)

O. Jakubov

2012-06-01

Full Text Available Semi-analytic simulation principle in GNSS signal processing bypasses the bit-true operations at high sampling frequency. Instead, signals at the output branches of the integrate&dump blocks are successfully modeled, thus making extensive Monte Carlo simulations feasible. Methods for simulations of code and carrier tracking loops with BPSK, BOC signals have been introduced in the literature. Matlab toolboxes were designed and published. In this paper, we further extend the applicability of the approach. Firstly, we describe any GNSS signal as a special instance of linear multi-dimensional modulation. Thereby, we state universal framework for classification of differently modulated signals. Using such description, we derive the semi-analytic models generally. Secondly, we extend the model for realistic scenarios including delay in the feed back, slowly fading multipath effects, finite bandwidth, phase noise, and a combination of these. Finally, a discussion on connection of this semi-analytic model and position-velocity-time estimator is delivered, as well as comparison of theoretical and simulated characteristics, produced by a prototype simulator developed at CTU in Prague.

Jet Propellant (JP)-8 Fuel Evaluation Test Mk II - Reset (Mk II R) Bridge Erection Boat (BEB)

Science.gov (United States)

2008-10-01

diesel engines (fig. 2 and 3) equipped with Delphi rotary fuel injection pumps. Figure 1. Mk II R BEB pushing a two-bay IRB raft. TR No. WF-E-83 2... nozzles . The new pump (serial No. 08813K7B) and gasket were installed. 24 May 07 51.0 50.4 44.9 103 Port Fuel Pump and Injectors Replaced. At the...part No. 3909356) were installed on the injector nozzles . The new pump (serial No. 59640HZB) and gasket were installed. 31 May 07 51.5 50.5 44.9 104

Effects of the differences between the ITRF2000 and ITRF2005 models in GNSS data processing

Directory of Open Access Journals (Sweden)

Zhan Wei

2013-01-01

Full Text Available In comparison with the ITRF2000 model, the ITRF2005 model represents a significant improvement in solution generation, datum definition and realization. However, these improvements cause a frame difference between the ITRF2000 and ITRF2005 models, which may impact GNSS data processing. To quantify this impact, the differences of the GNSS results obtained using the two models, including station coordinates, baseline length and horizontal velocity field, were analyzed. After transformation, the differences in position were at the millimeter level, and the differences in baseline length were less than 1 mm. The differences in the horizontal velocity fields decreased with as the study area was reduced. For a large region, the differences in these value were less than 1 mm/a, with a systematic difference of approximately 2 degrees in direction, while for a medium-sized region, the differences in value and direction were not significant.

Spatiotemporal distribution of interplate slip following the 2003 Tokachi-oki earthquake deduced from ocean bottom pressure gauges and onland GNSS data

Science.gov (United States)

Itoh, Y.; Nishimura, T.; Ariyoshi, K.; Matsumoto, H.

2017-12-01

The 2003 Tokachi-oki earthquake (Mw 8.0) is an interplate earthquake along the Kurile trench. Its co- and post-seismic deformation has been observed by onland GNSS [e.g., Miyazaki et al. 2004] and modeled with afterslip and/or viscoelastic relaxation [e.g., Itoh and Nishimura 2016]. In the offshore region, two ocean bottom pressure gauges (OBPs) are operated by JAMSTEC since July 1999 [Hirata et al. 2002] and they have continuously observed the pre-, co- and post-seismic pressure change of the 2003 event [Baba et al. 2006]. The observed pressure change can be interpreted as vertical displacement, and the resolution of slip beneath the seafloor far from the land was improved by incorporating these pressure data into onland GNSS data [Baba et al. 2006]. However, no previous studies used postseismic pressure data for several years to estimate an interplate slip. Because, in this region, an M8 class event similar to the 2003 event has occurred in 1952, it is important to clarify a healing process of an interplate coupling which may lead to a next M8 class event in terms of the earthquake cycle. Itoh and Nishimura [2017, JpGU-AGU Joint Meeting] estimated it but used only onland GNSS data. In this study, we use both onland GNSS and OBP data. For OBP data analysis, we first removed the tidal component using BAYTAP08 [Tamura et al. 1991; Tamura and Agnew 2008]. Next, we corrected the temporal fluctuation of data correlating with temperature [Baba et al. 2006]. We estimated the linear trend before the 2003 event using the corrected time series from 2002 Jan. 1 to 2003 Sep. 1 and remove the estimated trend from the data after the 2003 event. Here, we assumed a non-linear drift could be ignored. Finally, we down-sampled the remained time series with an interval of 1 month. For the onland GNSS data, we used the same data set of Itoh and Nishimura [2017, JpGU-AGU Joint Meeting]. We constructed the model consisting of coseismic slip of the 2003 and M6-7 events in the postseismic

Improving multi-GNSS ultra-rapid orbit determination for real-time precise point positioning

Science.gov (United States)

Li, Xingxing; Chen, Xinghan; Ge, Maorong; Schuh, Harald

2018-03-01

Currently, with the rapid development of multi-constellation Global Navigation Satellite Systems (GNSS), the real-time positioning and navigation are undergoing dramatic changes with potential for a better performance. To provide more precise and reliable ultra-rapid orbits is critical for multi-GNSS real-time positioning, especially for the three merging constellations Beidou, Galileo and QZSS which are still under construction. In this contribution, we present a five-system precise orbit determination (POD) strategy to fully exploit the GPS + GLONASS + BDS + Galileo + QZSS observations from CDDIS + IGN + BKG archives for the realization of hourly five-constellation ultra-rapid orbit update. After adopting the optimized 2-day POD solution (updated every hour), the predicted orbit accuracy can be obviously improved for all the five satellite systems in comparison to the conventional 1-day POD solution (updated every 3 h). The orbit accuracy for the BDS IGSO satellites can be improved by about 80, 45 and 50% in the radial, cross and along directions, respectively, while the corresponding accuracy improvement for the BDS MEO satellites reaches about 50, 20 and 50% in the three directions, respectively. Furthermore, the multi-GNSS real-time precise point positioning (PPP) ambiguity resolution has been performed by using the improved precise satellite orbits. Numerous results indicate that combined GPS + BDS + GLONASS + Galileo (GCRE) kinematic PPP ambiguity resolution (AR) solutions can achieve the shortest time to first fix (TTFF) and highest positioning accuracy in all coordinate components. With the addition of the BDS, GLONASS and Galileo observations to the GPS-only processing, the GCRE PPP AR solution achieves the shortest average TTFF of 11 min with 7{°} cutoff elevation, while the TTFF of GPS-only, GR, GE and GC PPP AR solution is 28, 15, 20 and 17 min, respectively. As the cutoff elevation increases, the reliability and accuracy of GPS-only PPP AR solutions

Comparison of long-term SLR and GNSS solutions from selected stations in the frame of GGOS realization

Science.gov (United States)

Szafranek, K.; Schillak, S.; Araszkiewicz, A.; Figurski, M.; Lehmann, M.; Lejba, P.

2012-04-01

Up-to-date investigations concerning space geodesy are mostly aimed at data of various techniques joint processing. The poster presents solutions (North, East, Up components) of selected stations (McDonald, Yarragadee, Greenbelt, Monument Peak, Zimmerwald, Borowiec, Mt.Stromlo-Orroral, Potsdam, Graz, Herstmonceux and Wettzell), which adopted Satellite Laser Ranging (SLR) and Global Navigation Satellite System (GNSS) techniques and which were gathering the data in the same time (from 1994 to 2010). Processing of both types of data was made according to Global Geodetic Observing System (GGOS) recommendations, the same models and parameters from IERS Conventions 2010 were used in both processing strategies (if it was possible). The main goal was to obtain coordinates and their changes in time (velocities) basing on both techniques and to compare the results. The station coordinates were determined for the common reference epoch of both techniques - for first day of each month. Monthly orbital arcs for laser observations were created basing on solutions from several SLR sites (observations to LAGEOS-1 and LAGEOS-2 satellites) with the best solutions quality and the highest amount of observations. For GNSS coordinates determination about 130 sites belonging to International GNSS Service (IGS) were selected: 30 with local ties to SLR sites and others basing on their geolocalization (length of the baselines) and solutions time series analysis. Mainly, core IGS stations were used. Solutions of both techniques were analyzed in order to verify agreement of both techniques and for independent control of local ties.

rFN/Cad-11-Modified Collagen Type II Biomimetic Interface Promotes the Adhesion and Chondrogenic Differentiation of Mesenchymal Stem Cells

Science.gov (United States)

Guo, Hongfeng; Zhang, Yuan; Li, Zhengsheng; Kang, Fei; Yang, Bo; Kang, Xia; Wen, Can; Yan, Yanfei; Jiang, Bo; Fan, Yujiang

2013-01-01

Properties of the cell-material interface are determining factors in the successful function of cells for cartilage tissue engineering. Currently, cell adhesion is commonly promoted through the use of polypeptides; however, due to their lack of complementary or modulatory domains, polypeptides must be modified to improve their ability to promote adhesion. In this study, we utilized the principle of matrix-based biomimetic modification and a recombinant protein, which spans fragments 7–10 of fibronectin module III (heterophilic motif ) and extracellular domains 1–2 of cadherin-11 (rFN/Cad-11) (homophilic motif ), to modify the interface of collagen type II (Col II) sponges. We showed that the designed material was able to stimulate cell proliferation and promote better chondrogenic differentiation of rabbit mesenchymal stem cells (MSCs) in vitro than both the FN modified surfaces and the negative control. Further, the Col II/rFN/Cad-11-MSCs composite stimulated cartilage formation in vivo; the chondrogenic effect of Col II alone was much less significant. These results suggested that the rFN/Cad-11-modified collagen type II biomimetic interface has dual biological functions of promoting adhesion and stimulating chondrogenic differentiation. This substance, thus, may serve as an ideal scaffold material for cartilage tissue engineering, enhancing repair of injured cartilage in vivo. PMID:23919505

Tropospheric products of the second GOP European GNSS reprocessing (1996-2014)

Science.gov (United States)

Dousa, Jan; Vaclavovic, Pavel; Elias, Michal

2017-09-01

In this paper, we present results of the second reprocessing of all data from 1996 to 2014 from all stations in International Association of Geodesy (IAG) Reference Frame Sub-Commission for Europe (EUREF) Permanent Network (EPN) as performed at the Geodetic Observatory Pecný (GOP). While the original goal of this research was to ultimately contribute to the realization of a new European Terrestrial Reference System (ETRS), we also aim to provide a new set of GNSS (Global Navigation Satellite System) tropospheric parameter time series with possible applications to climate research. To achieve these goals, we improved a strategy to guarantee the continuity of these tropospheric parameters and we prepared several variants of troposphere modelling. We then assessed all solutions in terms of the repeatability of coordinates as an internal evaluation of applied models and strategies and in terms of zenith tropospheric delays (ZTDs) and horizontal gradients with those of the ERA-Interim numerical weather model (NWM) reanalysis. When compared to the GOP Repro1 (first EUREF reprocessing) solution, the results of the GOP Repro2 (second EUREF reprocessing) yielded improvements of approximately 50 and 25 % in the repeatability of the horizontal and vertical components, respectively, and of approximately 9 % in tropospheric parameters. Vertical repeatability was reduced from 4.14 to 3.73 mm when using the VMF1 mapping function, a priori ZHD (zenith hydrostatic delay), and non-tidal atmospheric loading corrections from actual weather data. Raising the elevation cut-off angle from 3 to 7° and then to 10° increased RMS from coordinates' repeatability, which was then confirmed by independently comparing GNSS tropospheric parameters with the NWM reanalysis. The assessment of tropospheric horizontal gradients with respect to the ERA-Interim revealed a strong sensitivity of estimated gradients to the quality of GNSS antenna tracking performance. This impact was demonstrated at the

Ground-Based Global Navigation Satellite System (GNSS) Compact Observation Data (1-second sampling, sub-hourly files) from NASA CDDIS

Data.gov (United States)

National Aeronautics and Space Administration — This dataset consists of ground-based Global Navigation Satellite System (GNSS) Observation Data (1-second sampling, sub-hourly files) from the NASA Crustal Dynamics...

Interaction of the tylosin-resistance methyltransferase RlmA II at its rRNA target differs from the orthologue RlmA I

DEFF Research Database (Denmark)

Douthwaite, Stephen; Jakobsen, Lene; Yoshizawa, Satoko

2008-01-01

of Gram-positive bacteria, including the tylosin-producer Streptomyces fradiae and the pathogen Streptococcus pneumoniae. Recombinant S. pneumoniae RlmA(II) was purified and shown to retain its activity and specificity in vitro when tested on unmethylated 23 S rRNA substrates. RlmA(II) makes multiple......RlmA(II) methylates the N1-position of nucleotide G748 in hairpin 35 of 23 S rRNA. The resultant methyl group extends into the peptide channel of the 50 S ribosomal subunit and confers resistance to tylosin and other mycinosylated macrolide antibiotics. Methylation at G748 occurs in several groups...

Average [O II] nebular emission associated with Mg II absorbers: dependence on Fe II absorption

Science.gov (United States)

Joshi, Ravi; Srianand, Raghunathan; Petitjean, Patrick; Noterdaeme, Pasquier

2018-05-01

We investigate the effect of Fe II equivalent width (W2600) and fibre size on the average luminosity of [O II] λλ3727, 3729 nebular emission associated with Mg II absorbers (at 0.55 ≤ z ≤ 1.3) in the composite spectra of quasars obtained with 3 and 2 arcsec fibres in the Sloan Digital Sky Survey. We confirm the presence of strong correlations between [O II] luminosity (L_{[O II]}) and equivalent width (W2796) and redshift of Mg II absorbers. However, we show L_{[O II]} and average luminosity surface density suffer from fibre size effects. More importantly, for a given fibre size, the average L_{[O II]} strongly depends on the equivalent width of Fe II absorption lines and found to be higher for Mg II absorbers with R ≡W2600/W2796 ≥ 0.5. In fact, we show the observed strong correlations of L_{[O II]} with W2796 and z of Mg II absorbers are mainly driven by such systems. Direct [O II] detections also confirm the link between L_{[O II]} and R. Therefore, one has to pay attention to the fibre losses and dependence of redshift evolution of Mg II absorbers on W2600 before using them as a luminosity unbiased probe of global star formation rate density. We show that the [O II] nebular emission detected in the stacked spectrum is not dominated by few direct detections (i.e. detections ≥3σ significant level). On an average, the systems with R ≥ 0.5 and W2796 ≥ 2 Å are more reddened, showing colour excess E(B - V) ˜ 0.02, with respect to the systems with R < 0.5 and most likely trace the high H I column density systems.

Searching for R-parity violation at run-II of the tevatron

International Nuclear Information System (INIS)

Allanach, B.; Banerjee, S.; Berger, E. L.; Chertok, M.; Diaz, M. A.; Dreiner, H.; Eboli, O. J. P.; Harris, B. W.; Hewett, J.; Magro, M. B.; Mondal, N. K.; Narasimham, V. S.; Navarro, L.; Parua, N.; Porod, W.; Restrepo, D. A.; Richardson, P.; Rizzo, T.; Seymour, M. H.; Sullivan, Z.; Valle, J. W. F.; Campos, F. de

1999-01-01

The authors present an outlook for possible discovery of supersymmetry with broken R-parity at Run II of the Tevatron. They first present a review of the literature and an update of the experimental bounds. In turn they then discuss the following processes: (1) resonant slepton production followed by R P decay, (a) via LQD c and (b) via LLE c ; (2) how to distinguish resonant slepton production from Zprime or Wprime production; (3) resonant slepton production followed by the decay to neutralino LSP, which decays via LQD c ; (4) resonant stop production followed by the decay to a chargino, which cascades to the neutralino LSP; (5) gluino pair production followed by the cascade decay to charm squarks which decay directly via L 1 Q 2 D 1 c ; (6) squark pair production followed by the cascade decay to the neutralino LSP which decays via L 1 Q 2 D 1 c ; (7) MSSM pair production followed by the cascade decay to the LSP which decays (a) via LLE c , (b) via LQD c , and (c) via U c D c D c , respectively; and (8) top quark and top squark decays in spontaneous R P

Sciences of geodesy II innovations and future developments

CERN Document Server

Xu, Guochang

2014-01-01

This series of reference books describes the sciences of different fields in and around geodesy. Each chapter, is written by experts in the respective fields and covers an individual field and describes the history, theory, the objective, the technology, and the development, the highlight of the research, the applications, the problems, as well as future directions. Contents of Volume II include: Geodetic LEO Satellite Missions, Satellite Altimetry, Airborne Lidar, GNSS Software Receiver, Geodetic Boundary Problem, GPS and INS, VLBI, Geodetic Reference Systems, Spectral Analysis, Earth Tide and Ocean Loading Tide, Remote Sensing, Photogrammetry, Occultation, Geopotential Determination, Geoid Determination, Local Gravity Field, Geopotential Determination, Magnet Field, Mobile Mapping, General Relativity, Wide-area Precise Positioning etc.

The GNSS-based Ground Tracking System (GTS) of GFZ; from GITEWS to PROTECTS and beyond

Science.gov (United States)

Falck, Carsten; Merx, Alexander; Ramatschi, Markus

2013-04-01

Introduction An automatic system for the near real-time determination and visualization of ground motions, respectively co-seismic deformations of the Earth's surface, was developed by GFZ (German Research Centre for Geosciences) within the project GITEWS (German Indonesian Tsunami Early Warning System). The system is capable to deliver 3D-displacement vectors for locations with appropriate GPS-equipment in the vicinity of an earthquake's epicenter with a delay of only a few minutes. These vectors can help to assess the earthquake causing tectonic movements, which must be known to make reliable early warning predictions, e.g., concerning the generation of tsunami waves. The GTS (Ground Tracking System) has been integrated into InaTEWS (Indonesian Tsunami Early Warning System) and is in operation at the national warning center in Jakarta since November 2008. After the end of the project GITEWS GFZ continues to support the GTS in Indonesia within the frame of PROTECTS (Project for Training, Education and Consulting for Tsunami Early Warning Systems) and recently some new developments have been introduced. We now aim to make further use of the achievements made, e.g., by developing a license model for the GTS software package. Motivation After the Tsunami of 26th December 2004 the German government initiated the GITEWS project to develop the main components for a tsunami early warning system in Indonesia. The GFZ, as the consortial leader of GITEWS, had several work packages, most of them related to sensor systems. The geodetic branch (Department 1) of GFZ was assigned to develop a GNSS-based component, which since then is known as the GTS (Ground Tracking System). System benefit The ground motion information delivered by the GTS is a valuable source for a fast understanding of an earthquake's mechanism with a high relevance to assess the probability and magnitude of a potentially following tsunami. The system may detect highest displacement vector values, where

Comparison of two methods for blood lead analysis in cattle: graphite-furnace atomic absorption spectrometry and LeadCare(R) II system.

Science.gov (United States)

Bischoff, Karyn; Gaskill, Cynthia; Erb, Hollis N; Ebel, Joseph G; Hillebrandt, Joseph

2010-09-01

The current study compared the LeadCare(R) II test kit system with graphite-furnace atomic absorption spectrometry for blood lead (Pb) analysis in 56 cattle accidentally exposed to Pb in the field. Blood Pb concentrations were determined by LeadCare II within 4 hr of collection and after 72 hr of refrigeration. Blood Pb concentrations were determined by atomic absorption spectrometry, and samples that were coagulated (n = 12) were homogenized before analysis. There was strong rank correlation (R(2) = 0.96) between atomic absorption and LeadCare II (within 4 hr of collection), and a conversion formula was determined for values within the observed range (3-91 mcg/dl, although few had values >40 mcg/dl). Median and mean blood pb concentrations for atomic absorption were 7.7 and 15.9 mcg/dl, respectively; for LeadCare II, medians were 5.2 mcg/dl at 4 hr and 4.9 mcg/dl at 72 hr, and means were 12.4 and 11.7, respectively. LeadCare II results at 4 hr strongly correlated with 72 hr results (R(2) = 0.96), but results at 72 hr were lower (P atomic absorption. Although there have been several articles that compared LeadCare with other analytical techniques, all were for the original system, not LeadCare II. The present study indicated that LeadCare II results correlated well with atomic absorption over a wide range of blood Pb concentrations and that refrigerating samples for up to 72 hr before LeadCare II analysis was acceptable for clinical purposes.

Use of real-time GNSS-RF data to characterize the swing movements of forestry equipment

Science.gov (United States)

Ryer M. Becker; Robert F. Keefe; Nathaniel M. Anderson

2017-01-01

The western United States faces significant forest management challenges after severe bark beetle infestations have led to substantial mortality. Minimizing costs is vital for increasing the feasibility of management operations in affected forests. Multi‐transmitter Global Navigation Satellite System (GNSS)‐radio frequencies (RF) technology has applications in the...

LiDAR Scan Matching Aided Inertial Navigation System in GNSS-Denied Environments

Directory of Open Access Journals (Sweden)

Jian Tang

2015-07-01

Full Text Available A new scan that matches an aided Inertial Navigation System (INS with a low-cost LiDAR is proposed as an alternative to GNSS-based navigation systems in GNSS-degraded or -denied environments such as indoor areas, dense forests, or urban canyons. In these areas, INS-based Dead Reckoning (DR and Simultaneous Localization and Mapping (SLAM technologies are normally used to estimate positions as separate tools. However, there are critical implementation problems with each standalone system. The drift errors of velocity, position, and heading angles in an INS will accumulate over time, and on-line calibration is a must for sustaining positioning accuracy. SLAM performance is poor in featureless environments where the matching errors can significantly increase. Each standalone positioning method cannot offer a sustainable navigation solution with acceptable accuracy. This paper integrates two complementary technologies—INS and LiDAR SLAM—into one navigation frame with a loosely coupled Extended Kalman Filter (EKF to use the advantages and overcome the drawbacks of each system to establish a stable long-term navigation process. Static and dynamic field tests were carried out with a self-developed Unmanned Ground Vehicle (UGV platform—NAVIS. The results prove that the proposed approach can provide positioning accuracy at the centimetre level for long-term operations, even in a featureless indoor environment.

Rigorous Combination of GNSS and VLBI: How it Improves Earth Orientation and Reference Frames

Science.gov (United States)

Lambert, S. B.; Richard, J. Y.; Bizouard, C.; Becker, O.

2017-12-01

Current reference series (C04) of the International Earth Rotation and Reference Systems Service (IERS) are produced by a weighted combination of Earth orientation parameters (EOP) time series built up by combination centers of each technique (VLBI, GNSS, Laser ranging, DORIS). In the future, we plan to derive EOP from a rigorous combination of the normal equation systems of the four techniques.We present here the results of a rigorous combination of VLBI and GNSS pre-reduced, constraint-free, normal equations with the DYNAMO geodetic analysis software package developed and maintained by the French GRGS (Groupe de Recherche en GeÌodeÌsie Spatiale). The used normal equations are those produced separately by the IVS and IGS combination centers to which we apply our own minimal constraints.We address the usefulness of such a method with respect to the classical, a posteriori, combination method, and we show whether EOP determinations are improved.Especially, we implement external validations of the EOP series based on comparison with geophysical excitation and examination of the covariance matrices. Finally, we address the potential of the technique for the next generation celestial reference frames, which are currently determined by VLBI only.

The prognostic importance of miR-21 in stage II colon cancer: a population-based study

DEFF Research Database (Denmark)

Kjaer-Frifeldt, S.; Hansen, T. F.; Nielsen, B. S.

2012-01-01

that increasing miR-21 expression levels were significantly correlated to decreasing RF-CSS. Further investigations of the clinical importance of miR-21 in the selection of high-risk stage II colon cancer patients are merited. British Journal of Cancer (2012) 107, 1169-1174. doi:10.1038/bjc.2012.365 www......BACKGROUND: Despite several years of research and attempts to develop prognostic models a considerable fraction of stage II colon cancer patients will experience relapse within few years from their operation. The aim of the present study was to investigate the prognostic importance of miRNA-21 (mi......-free cancer-specific survival (RF-CSS): HR = 1.26; 95% CI: 1.15-1.60; P importance and was found to be significantly related to poor RF-CSS: HR 1.41; 95% CI: 1.19-1.67; P

Detecting discontinuities in GNSS coordinate time series with STARS: case study, the Bologna and Medicina GPS sites

Science.gov (United States)

Bruni, S.; Zerbini, Susanna; Raicich, F.; Errico, M.; Santi, E.

2014-12-01

Global navigation satellite systems (GNSS) data are a fundamental source of information for achieving a better understanding of geophysical and climate-related phenomena. However, discontinuities in the coordinate time series might be a severe limiting factor for the reliable estimate of long-term trends. A methodological approach has been adapted from Rodionov (Geophys Res Lett 31:L09204, 2004; Geophys Res Lett 31:L12707, 2006) and from Rodionov and Overland (J Marine Sci 62:328-332, 2005) to identify both the epoch of occurrence and the magnitude of jumps corrupting GNSS data sets without any a priori information on these quantities. The procedure is based on the Sequential t test Analysis of Regime Shifts (STARS) (Rodionov in Geophys Res Lett 31:L09204, 2004). The method has been tested against a synthetic data set characterized by typical features exhibited by real GNSS time series, such as linear trend, seasonal cycle, jumps, missing epochs and a combination of white and flicker noise. The results show that the offsets identified by the algorithm are split into 48 % of true-positive, 28 % of false-positive and 24 % of false-negative events. The procedure has then been applied to GPS coordinate time series of stations located in the southeastern Po Plain, in Italy. The series span more than 15 years and are affected by offsets of different nature. The methodology proves to be effective, as confirmed by the comparison between the corrected GPS time series and those obtained by other observation techniques.

Generation of real-time global ionospheric map based on the global GNSS stations with only a sparse distribution

Science.gov (United States)

Li, Zishen; Wang, Ningbo; Li, Min; Zhou, Kai; Yuan, Yunbin; Yuan, Hong

2017-04-01

The Earth's ionosphere is part of the atmosphere stretching from an altitude of about 50 km to more than 1000 km. When the Global Navigation Satellite System (GNSS) signal emitted from a satellite travels through the ionosphere before reaches a receiver on or near the Earth surface, the GNSS signal is significantly delayed by the ionosphere and this delay bas been considered as one of the major errors in the GNSS measurement. The real-time global ionospheric map calculated from the real-time data obtained by global stations is an essential method for mitigating the ionospheric delay for real-time positioning. The generation of an accurate global ionospheric map generally depends on the global stations with dense distribution; however, the number of global stations that can produce the real-time data is very limited at present, which results that the generation of global ionospheric map with a high accuracy is very different when only using the current stations with real-time data. In view of this, a new approach is proposed for calculating the real-time global ionospheric map only based on the current stations with real-time data. This new approach is developed on the basis of the post-processing and the one-day predicted global ionospheric map from our research group. The performance of the proposed approach is tested by the current global stations with the real-time data and the test results are also compared with the IGS-released final global ionospheric map products.

Using residual stacking to mitigate site-specific errors in order to improve the quality of GNSS-based coordinate time series of CORS

Science.gov (United States)

Knöpfler, Andreas; Mayer, Michael; Heck, Bernhard

2014-05-01

Within the last decades, positioning using GNSS (Global Navigation Satellite Systems; e.g., GPS) has become a standard tool in many (geo-) sciences. The positioning methods Precise Point Positioning and differential point positioning based on carrier phase observations have been developed for a broad variety of applications with different demands for example on accuracy. In high precision applications, a lot of effort was invested to mitigate different error sources: the products for satellite orbits and satellite clocks were improved; the misbehaviour of satellite and receiver antennas compared to an ideal antenna is modelled by calibration values on absolute level, the modelling of the ionosphere and the troposphere is updated year by year. Therefore, within processing of data of CORS (continuously operating reference sites), equipped with geodetic hardware using a sophisticated strategy, the latest products and models nowadays enable positioning accuracies at low mm level. Despite the considerable improvements that have been achieved within GNSS data processing, a generally valid multipath model is still lacking. Therefore, site specific multipath still represents a major error source in precise GNSS positioning. Furthermore, the calibration information of receiving GNSS antennas, which is for instance derived by a robot or chamber calibration, is valid strictly speaking only for the location of the calibration. The calibrated antenna can show a slightly different behaviour at the CORS due to near field multipath effects. One very promising strategy to mitigate multipath effects as well as imperfectly calibrated receiver antennas is to stack observation residuals of several days, thereby, multipath-loaded observation residuals are analysed for example with respect to signal direction, to find and reduce systematic constituents. This presentation will give a short overview about existing stacking approaches. In addition, first results of the stacking approach

Determination of zenith hydrostatic delay and its impact on GNSS-derived integrated water vapor

Directory of Open Access Journals (Sweden)

X. Wang

2017-08-01

Full Text Available Surface pressure is a necessary meteorological variable for the accurate determination of integrated water vapor (IWV using Global Navigation Satellite System (GNSS. The lack of pressure observations is a big issue for the conversion of historical GNSS observations, which is a relatively new area of GNSS applications in climatology. Hence the use of the surface pressure derived from either a blind model (e.g., Global Pressure and Temperature 2 wet, GPT2w or a global atmospheric reanalysis (e.g., ERA-Interim becomes an important alternative solution. In this study, pressure derived from these two methods is compared against the pressure observed at 108 global GNSS stations at four epochs (00:00, 06:00, 12:00 and 18:00 UTC each day for the period 2000–2013. Results show that a good accuracy is achieved from the GPT2w-derived pressure in the latitude band between −30 and 30° and the average value of 6 h root-mean-square errors (RMSEs across all the stations in this region is 2.5 hPa. Correspondingly, an error of 5.8 mm and 0.9 kg m−2 in its resultant zenith hydrostatic delay (ZHD and IWV is expected. However, for the stations located in the mid-latitude bands between −30 and −60° and between 30 and 60°, the mean value of the RMSEs is 7.3 hPa, and for the stations located in the high-latitude bands from −60 to −90° and from 60 to 90°, the mean value of the RMSEs is 9.9 hPa. The mean of the RMSEs of the ERA-Interim-derived pressure across at the selected 100 stations is 0.9 hPa, which will lead to an equivalent error of 2.1 mm and 0.3 kg m−2 in the ZHD and IWV, respectively, determined from this ERA-Interim-derived pressure. Results also show that the monthly IWV determined using pressure from ERA-Interim has a good accuracy − with a relative error of better than 3 % on a global scale; thus, the monthly IWV resulting from ERA-Interim-derived pressure has the potential to be used for climate studies

Synthesis and Characterization of Cu(II), Co(II) and Ni(II) Complexes of Trithiocyanuric Acid: The Structure of {N,N'-Bis(3-Aminopropyl)-1,3-Propanediamine}-(Trithiocyanurato)Nickel(II)

Czech Academy of Sciences Publication Activity Database

Kopel, P.; Trávníček, Zdeněk; Kvítek, L.; Černošek, Z.; Wrzeszcz, G.; Marek, J.

2003-01-01

Roč. 56, č. 1 (2003), s. 1-11 ISSN 0095-8972 R&D Projects: GA ČR GA203/00/0152; GA AV ČR IBS5038351 Institutional research plan: CEZ:AV0Z5038910 Keywords : Copper(II) * cobalt(II) and nickel(II) complexes * Trithiocyanuric acid Subject RIV: CE - Biochemistry Impact factor: 0.841, year: 2003

Synthesis and characterization of nickel(II), cobalt(II), copper(II), manganese(II), zinc(II), zirconium(IV), dioxouranium(VI) and dioxomolybdenum(VI) complexes of a new Schiff base derived from salicylaldehyde and 5-methylpyrazole-3-carbohydrazide

International Nuclear Information System (INIS)

Syamal, A.; Maurya, M.R.

1986-01-01

Synthesis of a new Schiff base derived from salicylaldehyde and 5-methylpyrazole-3-carbohydrazide, and its coordination compounds with nickel(II), cobalt(II), copper(II), manganese(II), zinc(II), zirconium(IV), dioxouranium(VI) and dioxomolybdenum(VI) are described. The ligand and the complexes have been characterized on the basis of analytical, conductance, molecular weight, i.r., electronic and n.m.r. spectra and magnetic susceptibility measurements. The stoichiometries of the complexes are represented as NiL . 3H 2 O, CoL . 2H 2 O, CuL, MnL . 2H 2 O, ZnL . H 2 O, Zr(OH) 2 (LH) 2 , Zr(OH) 2 L . 2MeOH, UO 2 L . MeOH and MoO 2 L . MeOH (where LH 2 =Schiff base). The copper(II) complex shows a subnormal magnetic moment due to antiferromagnetic exchange interaction while the nickel(II), cobalt(II) and manganese(II) complexes show normal magnetic moments at room temperature. The i.r. and n.m.r. spectral studies show that the Schiff base behaves as a dibasic and tridentate ligand coordinating through the deprotonated phenolic oxygen, enolic oxygen and azomethine nitrogen. (orig.)

and copper(II)

Indian Academy of Sciences (India)

Unknown

(II) and copper(II)–zinc(II) complexes. SUBODH KUMAR1, R N PATEL1*, P V KHADIKAR1 and. K B PANDEYA2. 1 Department of Chemistry, APS University, Rewa 486 003, India. 2 CSJM University, Kanpur 208 016, India e-mail: (R N Patel) ...

INS/GNSS Tightly-Coupled Integration Using Quaternion-Based AUPF for USV

Directory of Open Access Journals (Sweden)

Guoqing Xia

2016-08-01

Full Text Available This paper addresses the problem of integration of Inertial Navigation System (INS and Global Navigation Satellite System (GNSS for the purpose of developing a low-cost, robust and highly accurate navigation system for unmanned surface vehicles (USVs. A tightly-coupled integration approach is one of the most promising architectures to fuse the GNSS data with INS measurements. However, the resulting system and measurement models turn out to be nonlinear, and the sensor stochastic measurement errors are non-Gaussian and distributed in a practical system. Particle filter (PF, one of the most theoretical attractive non-linear/non-Gaussian estimation methods, is becoming more and more attractive in navigation applications. However, the large computation burden limits its practical usage. For the purpose of reducing the computational burden without degrading the system estimation accuracy, a quaternion-based adaptive unscented particle filter (AUPF, which combines the adaptive unscented Kalman filter (AUKF with PF, has been proposed in this paper. The unscented Kalman filter (UKF is used in the algorithm to improve the proposal distribution and generate a posterior estimates, which specify the PF importance density function for generating particles more intelligently. In addition, the computational complexity of the filter is reduced with the avoidance of the re-sampling step. Furthermore, a residual-based covariance matching technique is used to adapt the measurement error covariance. A trajectory simulator based on a dynamic model of USV is used to test the proposed algorithm. Results show that quaternion-based AUPF can significantly improve the overall navigation accuracy and reliability.

Il posizionamento satellitare compie trent’anni: lo stato dell’arte del GNSS

Directory of Open Access Journals (Sweden)

Fulvio Bernardini

2008-03-01

Full Text Available Satellite Positioning 30th anniversary: GNSS state of the art This year marks the 30th anniversary of the Satellite Positioning system. In 1978 the United States launched the first ever experimental satellite which formed the basis for the first Global Positioning System, commonly referred to as GPS. The system has evolved over the years from strict military use to more commercial mainstream applications. Today GPS is used in varied independent projects in the GNSS universe.

Sensitivity Analysis of Uncertainty Parameter based on MARS-LMR Code on SHRT-45R of EBR II

Energy Technology Data Exchange (ETDEWEB)

Kang, Seok-Ju; Kang, Doo-Hyuk; Seo, Jae-Seung [System Engineering and Technology Co., Daejeon (Korea, Republic of); Bae, Sung-Won [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of); Jeong, Hae-Yong [Sejong University, Seoul (Korea, Republic of)

2016-10-15

In order to assess the uncertainty quantification of the MARS-LMR code, the code has been improved by modifying the source code to accommodate calculation process required for uncertainty quantification. In the present study, a transient of Unprotected Loss of Flow(ULOF) is selected as typical cases of as Anticipated Transient without Scram(ATWS) which belongs to DEC category. The MARS-LMR input generation for EBR II SHRT-45R and execution works are performed by using the PAPIRUS program. The sensitivity analysis is carried out with Uncertainty Parameter of the MARS-LMR code for EBR-II SHRT-45R. Based on the results of sensitivity analysis, dominant parameters with large sensitivity to FoM are picked out. Dominant parameters selected are closely related to the development process of ULOF event.

Dysregulated miR-127-5p contributes to type II collagen degradation by targeting matrix metalloproteinase-13 in human intervertebral disc degeneration.

Science.gov (United States)

Hua, Wen-Bin; Wu, Xing-Huo; Zhang, Yu-Kun; Song, Yu; Tu, Ji; Kang, Liang; Zhao, Kang-Cheng; Li, Shuai; Wang, Kun; Liu, Wei; Shao, Zeng-Wu; Yang, Shu-Hua; Yang, Cao

2017-08-01

Intervertebral disc degeneration (IDD) is a chronic disease associated with the degradation of extracellular matrix (ECM). Matrix metalloproteinase (MMP)-13 is a major enzyme that mediates the degradation of ECM components. MMP-13 has been predicted to be a potential target of miR-127-5p. However, the exact function of miR-127-5p in IDD is still unclear. We designed this study to evaluate the correlation between miR-127-5p level and the degeneration of human intervertebral discs and explore the potential mechanisms. miR-127-5p levels and MMP-13 mRNA levels were detected by quantitative real-time polymerase chain reaction (qPCR). To determine whether MMP-13 is a target of miR-127-5p, dual luciferase reporter assays were performed. miR-127-5p mimic and miR-127-5p inhibitor were used to overexpress or downregulate miR-127-5p expression in human NP cells, respectively. Small interfering RNA (siRNA) was used to knock down MMP-13 expression in human NP cells. Type II collagen expression in human NP cells was detected by qPCR, western blotting, and immunofluorescence staining. We confirmed that miR-127-5p was significantly downregulated in nucleus pulposus (NP) tissue of degenerative discs and its expression was inversely correlated with MMP-13 mRNA levels. We reveal that MMP-13 may act as a target of miR-127-5p. Expression of miR-127-5p was inversely correlated with type II collagen expression in human NP cells. Moreover, suppression of MMP-13 expression by siRNA blocked downstream signaling and increased type II collagen expression. Dysregulated miR-127-5p contributed to the degradation of type II collagen by targeting MMP-13 in human IDD. Our findings highlight that miR-127-5p may serve as a new therapeutic target in IDD. Copyright © 2017 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.

Loose and Tight GNSS/INS Integrations: Comparison of Performance Assessed in Real Urban Scenarios

OpenAIRE

Falco, Gianluca; Pini, Marco; Marucco, Gianluca

2017-01-01

Global Navigation Satellite Systems (GNSSs) remain the principal mean of positioning in many applications and systems, but in several types of environment, the performance of standalone receivers is degraded. Although many works show the benefits of the integration between GNSS and Inertial Navigation Systems (INSs), tightly-coupled architectures are mainly implemented in professional devices and are based on high-grade Inertial Measurement Units (IMUs). This paper investigates the performanc...

Synthesis and Characterization of Reduced Graphene Oxide-Supported Nanoscale Zero-Valent Iron (nZVI/rGO Composites Used for Pb(II Removal

Directory of Open Access Journals (Sweden)

Mingyi Fan

2016-08-01

Full Text Available Reduced graphene oxide-supported nanoscale zero-valent iron (nZVI/rGO composites were prepared by chemical deposition method and were characterized by scanning electron microscopy (SEM, X-ray diffraction (XRD, Raman spectroscopy, N2-sorption and X-ray photoelectron spectroscopy (XPS. Operating parameters for the removal process of Pb(II ions, such as temperature (20–40 °C, pH (3–5, initial concentration (400–600 mg/L and contact time (20–60 min, were optimized using a quadratic model. The coefficient of determination (R2 > 0.99 obtained for the mathematical model indicates a high correlation between the experimental and predicted values. The optimal temperature, pH, initial concentration and contact time for Pb(II ions removal in the present experiment were 21.30 °C, 5.00, 400.00 mg/L and 60.00 min, respectively. In addition, the Pb(II removal by nZVI/rGO composites was quantitatively evaluated by using adsorption isotherms, such as Langmuir and Freundlich isotherm models, of which Langmuir isotherm gave a better correlation, and the calculated maximum adsorption capacity was 910 mg/g. The removal process of Pb(II ions could be completed within 50 min, which was well described by the pseudo-second order kinetic model. Therefore, the nZVI/rGO composites are suitable as efficient materials for the advanced treatment of Pb(II-containing wastewater.

PEP-II asymmetric B Factory: Design update and R ampersand D results

International Nuclear Information System (INIS)

Zisman, M.S.; Bell, R.A.; Dorfan, J.; Schwarz, H.; Barletta, W.A.; Calderon, M.

1992-07-01

PEP-II, a 9 GeV x 3.1 GeV e + e - collider with a design luminosity of 3 x 10 33 cm -2 s -1 , was proposed jointly by SLAC, LBL, and LLNL. Recent efforts have continued towards an optimized design. In addition, an aggressive R ampersand D program is under way to validate our design choices. Fabrication of a low-power prototype RF cavity is complete, and impedance measurements are beginning. A 500-kW, 476-MHz klystron has been completed; it will be used for testing both high-power RF windows and a prototype high-power cavity (now under design in collaboration with Chalk River Laboratory). Vacuum studies have demonstrated that chambers with suitable photodesorption properties can be fabricated. A mockup of the two-ring arc area has been completed and used to investigate alignment and stability issues. The PEP-II project is ready to begin construction as soon as funds become available

Use of reflected GNSS SNR data to retrieve either soil moisture or vegetation height from a wheat crop

Directory of Open Access Journals (Sweden)

S. Zhang

2017-09-01

Full Text Available This work aims to estimate soil moisture and vegetation height from Global Navigation Satellite System (GNSS Signal to Noise Ratio (SNR data using direct and reflected signals by the land surface surrounding a ground-based antenna. Observations are collected from a rainfed wheat field in southwestern France. Surface soil moisture is retrieved based on SNR phases estimated by the Least Square Estimation method, assuming the relative antenna height is constant. It is found that vegetation growth breaks up the constant relative antenna height assumption. A vegetation-height retrieval algorithm is proposed using the SNR-dominant period (the peak period in the average power spectrum derived from a wavelet analysis of SNR. Soil moisture and vegetation height are retrieved at different time periods (before and after vegetation's significant growth in March. The retrievals are compared with two independent reference data sets: in situ observations of soil moisture and vegetation height, and numerical simulations of soil moisture, vegetation height and above-ground dry biomass from the ISBA (interactions between soil, biosphere and atmosphere land surface model. Results show that changes in soil moisture mainly affect the multipath phase of the SNR data (assuming the relative antenna height is constant with little change in the dominant period of the SNR data, whereas changes in vegetation height are more likely to modulate the SNR-dominant period. Surface volumetric soil moisture can be estimated (R2  =  0.74, RMSE  =  0.009 m3 m−3 when the wheat is smaller than one wavelength (∼ 19 cm. The quality of the estimates markedly decreases when the vegetation height increases. This is because the reflected GNSS signal is less affected by the soil. When vegetation replaces soil as the dominant reflecting surface, a wavelet analysis provides an accurate estimation of the wheat crop height (R2  =  0.98, RMSE  =  6

Short period sound speed oscillation measured by intensive XBT survey and its role on GNSS/acoustic positioning

Science.gov (United States)

Kido, M.; Matsui, R.; Imano, M.; Honsho, C.

2017-12-01

In the GNSS/acoustic measurement, sound speed in ocean plays a key role of accuracy of final positioning. We have shown than longer period sound speed undulation can be properly estimated from GNSS-A analysis itself in our previous work. In this work, we have carried out intensive XBT measurement to get temporal variation of sound speed in short period to be compared with GNSS-A derived one. In the individual temperature profile obtained by intensive XBT measurements (10 minutes interval up to 12 times of cast), clear vertical oscillation up to 20 m of amplitude in the shallow part were observed. These can be interpreted as gravitational internal wave with short-period and hence short wavelength anomaly. Kido et al. (2007) proposed that horizontal variation of the ocean structure can be considered employing five or more transponders at once if the structure is expressed by two quantities, i.e., horizontal gradient in x/y directions. However, this hypothesis requires that the variation must has a large spatial scale (> 2-5km) so that the horizontal variation can be regarded as linear within the extent of acoustic path to seafloor transponders. Therefore the wavelength of the above observed internal wave is getting important. The observed period of internal wave was 30-60 minute. However its wavelength cannot be directly measured. It must be estimate based on density profile of water column. In the comparison between sound speed change and positioning, the delay of their phases were 90 degree, which indicates that most steep horizontal slope of internal wave correspond to largest apparent positioning shift.

Synthesis and reactivity towards diiodine of palladium(II) and platinum(II) complexes with non-cyclic and cyclic ligands (C6H3{CH=NR1R2}2-2,6)-. End-on diiodine-platinum(II) bonding in macrocyclic [PtI(C6H3{CH2NMe(CH2)7MeNCH2}-2,6)(h1-I2)

NARCIS (Netherlands)

Koten, G. van; Beek, J.A.M. van; Dekker, G.P.C.M.; Wissing, E.; Zoutberg, M.C.; Stam, C.H.

1990-01-01

Several new organo-platinum(II) and -palladium(II) complexes [MX(C{6}H{3}{CH{2}NR}1{R}2{}{2}-2, 6)] (X = halide, M = Pt, Pd; R}1{ = R}2{ = Et; R}2{ = Me, R}1{ = }t{Bu, M = Pt: R}2{ = Me, R}1{ = Ph) have been synthesized from [PtCl{2}(SEt{2}){2}] or [PdCl{2}(COD)] (COD = 1, 5-cyclooctadiene) by

Progress on PEP-II injection R ampersand D

International Nuclear Information System (INIS)

Bloom, E.; Bulos, F.; Fieguth, T.; Godfrey, G.; Loew, G.; Miller, R.

1993-06-01

The R ampersand D program described in this paper focuses on an improvement of the SLAC linac designed to extract and study a 9 GeV electron beam under stringent control of energy, energy spread, emittance, optical parameters, and timing. The extraction system begins with an on-axis pulsed magnet, followed by a magnetic lattice and diagnostic equipment required for the measurement and optimization of the above beam qualities. Design, construction, and installation of this system is the first step in the development of the overall PEP-II e ± injection system. This system is required to fill 1658 bunches of 9 GeV electrons (0.99A stored) and 3.1 GeV positrons (2.14A stored) in two separate rings in a total of about 6 minutes from zero ring current (i.e., full-fill mode, 0 to 100%) or in about 3 minutes from 80% ring current (i.e., topping-off mode, 80 to 100%). This unprecedented rate of filling can be met by a judicious use of the SLC linac, damping rings, and positron source

Progress on PEP-II injection R ampersand D

International Nuclear Information System (INIS)

Bloom, E.; Bulos, F.; Fieguth, T.; Godfrey, G.; Loew, G.; Miller, R.

1993-01-01

The R ampersand D program described in this paper focuses on an improvement of the SLAC linac designed to extract and study a 9 GeV electron beam under stringent control of energy, energy spread, emittance, optical parameters, and timing. The extraction system begins with an on-axis pulsed magnet, followed by a magnetic lattice and diagnostic equipment required for the measurement and optimization of the above beam qualities. Design, construction, and installation of this system is the first step in the development of the overall PEP-II e ± injection system. This system is required to fill 1658 bunches of 9 GeV electrons (0.99A stored) and 3.1 GeV positrons (2.14A stored) in two separate rings in a total of about 6 minutes from zero ring current (i.e., full-fill mode, 0 to 100%) or in about 3 minutes from 80% ring current (i.e., topping-off mode, 80 to 100%). This unprecedented rate of filling can be met by a judicious use of the SLC linac, damping rings, and positron source

Error compensation of single-antenna attitude determination using GNSS for Low-dynamic applications

Science.gov (United States)

Chen, Wen; Yu, Chao; Cai, Miaomiao

2017-04-01

GNSS-based single-antenna pseudo-attitude determination method has attracted more and more attention from the field of high-dynamic navigation due to its low cost, low system complexity, and no temporal accumulated errors. Related researches indicate that this method can be an important complement or even an alternative to the traditional sensors for general accuracy requirement (such as small UAV navigation). The application of single-antenna attitude determining method to low-dynamic carrier has just started. Different from the traditional multi-antenna attitude measurement technique, the pseudo-attitude attitude determination method calculates the rotation angle of the carrier trajectory relative to the earth. Thus it inevitably contains some deviations comparing with the real attitude angle. In low-dynamic application, these deviations are particularly noticeable, which may not be ignored. The causes of the deviations can be roughly classified into three categories, including the measurement error, the offset error, and the lateral error. Empirical correction strategies for the formal two errors have been promoted in previous study, but lack of theoretical support. In this paper, we will provide quantitative description of the three type of errors and discuss the related error compensation methods. Vehicle and shipborne experiments were carried out to verify the feasibility of the proposed correction methods. Keywords: Error compensation; Single-antenna; GNSS; Attitude determination; Low-dynamic

The CuSPED Mission: CubeSat for GNSS Sounding of the Ionosphere-Plasmasphere Electron Density

Science.gov (United States)

Gross, Jason N.; Keesee, Amy M.; Christian, John A.; Gu, Yu; Scime, Earl; Komjathy, Attila; Lightsey, E. Glenn; Pollock, Craig J.

2016-01-01

The CubeSat for GNSS Sounding of Ionosphere-Plasmasphere Electron Density (CuSPED) is a 3U CubeSat mission concept that has been developed in response to the NASA Heliophysics program's decadal science goal of the determining of the dynamics and coupling of the Earth's magnetosphere, ionosphere, and atmosphere and their response to solar and terrestrial inputs. The mission was formulated through a collaboration between West Virginia University, Georgia Tech, NASA GSFC and NASA JPL, and features a 3U CubeSat that hosts both a miniaturized space capable Global Navigation Satellite System (GNSS) receiver for topside atmospheric sounding, along with a Thermal Electron Capped Hemispherical Spectrometer (TECHS) for the purpose of in situ electron precipitation measurements. These two complimentary measurement techniques will provide data for the purpose of constraining ionosphere-magnetosphere coupling models and will also enable studies of the local plasma environment and spacecraft charging; a phenomenon which is known to lead to significant errors in the measurement of low-energy, charged species from instruments aboard spacecraft traversing the ionosphere. This paper will provide an overview of the concept including its science motivation and implementation.

Selected properties of GPS and Galileo-IOV receiver intersystem biases in multi-GNSS data processing

International Nuclear Information System (INIS)

Paziewski, Jacek; Sieradzki, Rafał; Wielgosz, Paweł

2015-01-01

Two overlapping frequencies—L1/E1 and L5/E5a—in GPS and Galileo systems support the creation of mixed double-differences in a tightly combined relative positioning model. On the other hand, a tightly combined model makes it necessary to take into account receiver intersystem bias, which is the difference in receiver hardware delays. This bias is present in both carrier-phase and pseudorange observations. Earlier research showed that using a priori knowledge of earlier-calibrated ISB to correct GNSS observations has significant impact on ambiguity resolution and, therefore, precise positioning results. In previous research concerning ISB estimation conducted by the authors, small oscillations in phase ISB time series were detected. This paper investigates this effect present in the GPS–Galileo-IOV ISB time series. In particular, ISB short-term temporal stability and its dependence on the number of Galileo satellites used in the ISB estimation was examined. In this contribution we investigate the amplitude and frequency of the detected ISB time series oscillations as well as their potential source. The presented results are based on real observational data collected on a zero baseline with the use of different sets of GNSS receivers. (paper)

Selected properties of GPS and Galileo-IOV receiver intersystem biases in multi-GNSS data processing

Science.gov (United States)

Paziewski, Jacek; Sieradzki, Rafał; Wielgosz, Paweł

2015-09-01

Two overlapping frequencies—L1/E1 and L5/E5a—in GPS and Galileo systems support the creation of mixed double-differences in a tightly combined relative positioning model. On the other hand, a tightly combined model makes it necessary to take into account receiver intersystem bias, which is the difference in receiver hardware delays. This bias is present in both carrier-phase and pseudorange observations. Earlier research showed that using a priori knowledge of earlier-calibrated ISB to correct GNSS observations has significant impact on ambiguity resolution and, therefore, precise positioning results. In previous research concerning ISB estimation conducted by the authors, small oscillations in phase ISB time series were detected. This paper investigates this effect present in the GPS-Galileo-IOV ISB time series. In particular, ISB short-term temporal stability and its dependence on the number of Galileo satellites used in the ISB estimation was examined. In this contribution we investigate the amplitude and frequency of the detected ISB time series oscillations as well as their potential source. The presented results are based on real observational data collected on a zero baseline with the use of different sets of GNSS receivers.

VADASE: a new approach for real-time fast displacement detection - First application to Taiwan High-Rate GNSS Network

Science.gov (United States)

Hung, Huang-Kai; Rau, Ruey-Juin; Colosimo, Gabriele; Benedetti, Elisa; Branzanti, Mara; Crespi, Mattia; Mazzoni, Augusto

2014-05-01

The aim of this work is to show new possibilities for GNSS Permanent Network data processing offered by VADASE (Variometric Approach for Displacements Analysis Standalone Engine) to retrieve waveforms and coseismic displacements in real-time when an earthquake occurs. The main advantage of using GNSS receiver, in a complementary way with traditional seismic network, is that it can work without being affected by saturation, which commonly influence seismometers and accelerometers close to strong earthquake epicenters. VADASE was originally proposed in 2010 ([4],[5]) as the third way in GPS Seismology (in addition to Precise Point Positioning and Instantaneous Differential Positioning). The approach is based on time single differences of carrier phase observations continuously collected at high rate (1 Hz or higher) using a standalone GPS receiver and standard GPS broadcast products (orbits and clocks) that are available in real-time. Hence, one receiver works in standalone mode and the epoch-by-epoch displacements (equivalent to velocities) are estimated. Then, they are summed over the time interval when the earthquake occurred to retrieve coseismic displacements and waveforms. Considering time intervals limited to few minutes, the receiver displacements can be ascertained at a few centimeters accuracy level in real-time. The effectiveness of this approach was recognized by DLR (German Aerospace Agency), and VADASE was awarded the DLR Special Topic Prize and the Audience Award at the European Satellite Navigation Competition 2010. Moreover, VADASE potential was proven in the dramatic occasion of the Japanese earthquake occurred on March 11, 2011 ([3]-[6]); in fact VADASE was able to provide the first estimates of the displacements suffered at the IGS sites of MIZU and USUD [7], as soon as the data of these stations were available. The results were then confirmed by several other solutions based on the renown (DP, PPP) approaches. More recently, VADASE was applied

Local Tsunami Warnings using GNSS and Seismic Data.

Science.gov (United States)

Hirshorn, B. F.

2017-12-01

Tsunami warning Centers (TWC's) must issue warnings based on imperfect and limited data. Uncertainties increase in the near field, where a tsunami reaches the closest coastal populations to the causative earthquake in a half hour or less. In the absence of a warning, the usual advice is "When the ground shakes so severely that it's difficult to stand, move uphill and away from the coast." But, what if the shaking is not severe? If, for example, the earthquake ruptures slowly (producing very little perceived shaking) this advice will fail. Unfortunately these "Tsunami" earthquakes are not rare: tsunamis from slow earthquakes off of Nicaragua in 1992, and Java in 1994 and 2006, killed 179, 250 and 637 people, respectively, even though very few nearby coastal residents felt any strong ground shaking. TWC's must therefore warn the closest coastal populations to the causative earthquake, where over 80% of the Tsunami based casualties typically occur, as soon possible after earthquake rupture begins. The NWS Tsunami Warning Centers (TWCs) currently issue local Tsunami Warnings for the US West Coast, Hawaii, and the Puerto Rico - Virgin Island region within 2-4 minutes after origin time. However, our initial short period Magnitude estimates saturate over about Mw 6.5, and Mwp underestimates Mw for events larger than about Mw 7.5 when using data in the 0 to 3 degree epicentral distance range, severely underestimating the danger of a potential Tsunami in the near field. Coastal GNSS networks complement seismic monitoring networks, and enable unsaturated estimates of Mw within 2-3 minutes of earthquake origin time. NASA/JPL, SIO, USGS, CWU, UCB and UW, with funding and guidance from NASA, and leveraging the USGS funded ShakeAlert development, have been working with the National Weather Service TWC's to incorporate real-time GNSS and seismogeodetic data into their operations. These data will soon provide unsaturated estimates of moment magnitude, Centroid Moment Tensor

Adjustment and transformation strategies of ItalPoS Permanent GNSS Network

Directory of Open Access Journals (Sweden)

Alessandro Capra

2009-06-01

Full Text Available A private network of 133 Global Navigation Satellite Systems (GNSS permanent sites, named ItalPoS (Italian
Positioning Service and uniformly covering the entire Italian territory, was established in April 2006 by the Italian
Division of Leica Geosystems S.p.A. This network also involves several GPS stations of the INGV (Italian
National Institute of Geophysics and Volcanology RING (Real-time Integrated National Gps network and GPS
stations from other public and private bodies. Indeed Leica Geosystems contributed with its experience and its
products to these networks which currently fulfil the national coverage where there are no ItalPoS stations. For
instance, the purpose of the ItalPoS network is mainly GNSS data distribution in terms of real time corrections
and RINEX files for the post-processing.
In order to compute and distribute to private and scientific users a set of adjusted coordinates of the ItalPoS network
in the IGS05 and ETRF89-2000 reference frames, a dataset of RINEX of about 120 GPS permanent sites
was created and processed, using the distributed sessions approach, by means of Gamit/Globk 10.3 GPS data
processor, also using some SOPAC (Scripps Orbits and Permanent Array Center and EUREF (European Permanent
Network solutions to improve the reference frame definition and the internal constraints.
This paper describes all the strategies adopted to estimate coordinates and velocities of the ItalPoS Network in
IGS05 and in ETRF89-2000 reference frames in the whole Italian territory.

Adaptation of Dubins Paths for UAV Ground Obstacle Avoidance When Using a Low Cost On-Board GNSS Sensor

Directory of Open Access Journals (Sweden)

Ramūnas Kikutis

2017-09-01

Full Text Available Current research on Unmanned Aerial Vehicles (UAVs shows a lot of interest in autonomous UAV navigation. This interest is mainly driven by the necessity to meet the rules and restrictions for small UAV flights that are issued by various international and national legal organizations. In order to lower these restrictions, new levels of automation and flight safety must be reached. In this paper, a new method for ground obstacle avoidance derived by using UAV navigation based on the Dubins paths algorithm is presented. The accuracy of the proposed method has been tested, and research results have been obtained by using Software-in-the-Loop (SITL simulation and real UAV flights, with the measurements done with a low cost Global Navigation Satellite System (GNSS sensor. All tests were carried out in a three-dimensional space, but the height accuracy was not assessed. The GNSS navigation data for the ground obstacle avoidance algorithm is evaluated statistically.

Adaptation of Dubins Paths for UAV Ground Obstacle Avoidance When Using a Low Cost On-Board GNSS Sensor.

Science.gov (United States)

Kikutis, Ramūnas; Stankūnas, Jonas; Rudinskas, Darius; Masiulionis, Tadas

2017-09-28

Current research on Unmanned Aerial Vehicles (UAVs) shows a lot of interest in autonomous UAV navigation. This interest is mainly driven by the necessity to meet the rules and restrictions for small UAV flights that are issued by various international and national legal organizations. In order to lower these restrictions, new levels of automation and flight safety must be reached. In this paper, a new method for ground obstacle avoidance derived by using UAV navigation based on the Dubins paths algorithm is presented. The accuracy of the proposed method has been tested, and research results have been obtained by using Software-in-the-Loop (SITL) simulation and real UAV flights, with the measurements done with a low cost Global Navigation Satellite System (GNSS) sensor. All tests were carried out in a three-dimensional space, but the height accuracy was not assessed. The GNSS navigation data for the ground obstacle avoidance algorithm is evaluated statistically.

A numerical investigation on the eccentricity growth of GNSS disposal orbits

Science.gov (United States)

Alessi, E. M.; Deleflie, F.; Rosengren, A. J.; Rossi, A.; Valsecchi, G. B.; Daquin, J.; Merz, K.

2016-05-01

We present the results of an extensive numerical exploration performed on the eccentricity growth in MEO associated with two possible end-of-life disposal strategies for GNSS satellites. The study calls attention to the existence of values of initial inclination, longitude of ascending node, and argument of perigee that are more advantageous in terms of long-term stability of the orbit. The important role of the initial epoch and a corresponding periodicity are also shown. The present investigation is influential in view of recent analytical and numerical developments on the chaotic nature of the region due to lunisolar perturbations, but also for the upcoming Galileo and BeiDou constellations.

Benchmark analyses for EBR-II shutdown heat removal tests SHRT-17 and SHRT-45R

Energy Technology Data Exchange (ETDEWEB)

Mochizuki, Hiroyasu, E-mail: mochizki@u-fukui.ac.jp [Research Institute of Nuclear Engineering, University of Fukui (Japan); Muranaka, Kohmei; Asai, Takayuki [Graduate School of Engineering, University of Fukui (Japan); Rooijen, W.F.G. van, E-mail: rooijen@u-fukui.ac.jp [Research Institute of Nuclear Engineering, University of Fukui (Japan)

2014-08-15

Highlights: • The IAEA EBR-II benchmarks SHRT-17 and SHRT-45R are analyzed with a 1D system code. • The calculated result of SHRT-17 corresponds well to the measured results. • For SHRT-45R ERANOS is used for various core parameters and reactivity coefficients. • SHRT-45R peak temperature is overestimated with the ERANOS feedback coefficients. • The peak temperature is well predicted when the feedback coefficient is reduced. - Abstract: Benchmark problems of several experiments in EBR-II, proposed by ANL and coordinated by the IAEA, are analyzed using the plant system code NETFLOW++ and the neutronics code ERANOS. The SHRT-17 test conducted as a loss-of-flow test is calculated using only the NETFLOW++ code because it is a purely thermal–hydraulic problem. The measured data were made available to the benchmark participants after the results of the blind benchmark calculations were submitted. Our work shows that major parameters of the plant are predicted with good accuracy. The SHRT-45R test, an unprotected loss of flow test is calculated using the NETFLOW++ code with the aid of delayed neutron data and reactivity coefficients calculated by the ERANOS code. These parameters are used in the NETFLOW++ code to perform a semi-coupled analysis of the neutronics – thermal–hydraulic problem. The measured data are compared with our calculated results. In our work, the peak temperature is underestimated, indicating that the reactivity feedback coefficients are too strong. When the reactivity feedback coefficient for thermal expansion is adjusted, good agreement is obtained in general for the calculated plant parameters, with a few exceptions.

Multi-GNSS phase delay estimation and PPP ambiguity resolution: GPS, BDS, GLONASS, Galileo

Science.gov (United States)

Li, Xingxing; Li, Xin; Yuan, Yongqiang; Zhang, Keke; Zhang, Xiaohong; Wickert, Jens

2018-06-01

This paper focuses on the precise point positioning (PPP) ambiguity resolution (AR) using the observations acquired from four systems: GPS, BDS, GLONASS, and Galileo (GCRE). A GCRE four-system uncalibrated phase delay (UPD) estimation model and multi-GNSS undifferenced PPP AR method were developed in order to utilize the observations from all systems. For UPD estimation, the GCRE-combined PPP solutions of the globally distributed MGEX and IGS stations are performed to obtain four-system float ambiguities and then UPDs of GCRE satellites can be precisely estimated from these ambiguities. The quality of UPD products in terms of temporal stability and residual distributions is investigated for GPS, BDS, GLONASS, and Galileo satellites, respectively. The BDS satellite-induced code biases were corrected for GEO, IGSO, and MEO satellites before the UPD estimation. The UPD results of global and regional networks were also evaluated for Galileo and BDS, respectively. As a result of the frequency-division multiple-access strategy of GLONASS, the UPD estimation was performed using a network of homogeneous receivers including three commonly used GNSS receivers (TRIMBLE NETR9, JAVAD TRE_G3TH DELTA, and LEICA). Data recorded from 140 MGEX and IGS stations for a 30-day period in January in 2017 were used to validate the proposed GCRE UPD estimation and multi-GNSS dual-frequency PPP AR. Our results show that GCRE four-system PPP AR enables the fastest time to first fix (TTFF) solutions and the highest accuracy for all three coordinate components compared to the single and dual system. An average TTFF of 9.21 min with 7{°} cutoff elevation angle can be achieved for GCRE PPP AR, which is much shorter than that of GPS (18.07 min), GR (12.10 min), GE (15.36 min) and GC (13.21 min). With observations length of 10 min, the positioning accuracy of the GCRE fixed solution is 1.84, 1.11, and 1.53 cm, while the GPS-only result is 2.25, 1.29, and 9.73 cm for the east, north, and vertical

GNSS global real-time augmentation positioning: Real-time precise satellite clock estimation, prototype system construction and performance analysis

Science.gov (United States)

Chen, Liang; Zhao, Qile; Hu, Zhigang; Jiang, Xinyuan; Geng, Changjiang; Ge, Maorong; Shi, Chuang

2018-01-01

Lots of ambiguities in un-differenced (UD) model lead to lower calculation efficiency, which isn't appropriate for the high-frequency real-time GNSS clock estimation, like 1 Hz. Mixed differenced model fusing UD pseudo-range and epoch-differenced (ED) phase observations has been introduced into real-time clock estimation. In this contribution, we extend the mixed differenced model for realizing multi-GNSS real-time clock high-frequency updating and a rigorous comparison and analysis on same conditions are performed to achieve the best real-time clock estimation performance taking the efficiency, accuracy, consistency and reliability into consideration. Based on the multi-GNSS real-time data streams provided by multi-GNSS Experiment (MGEX) and Wuhan University, GPS + BeiDou + Galileo global real-time augmentation positioning prototype system is designed and constructed, including real-time precise orbit determination, real-time precise clock estimation, real-time Precise Point Positioning (RT-PPP) and real-time Standard Point Positioning (RT-SPP). The statistical analysis of the 6 h-predicted real-time orbits shows that the root mean square (RMS) in radial direction is about 1-5 cm for GPS, Beidou MEO and Galileo satellites and about 10 cm for Beidou GEO and IGSO satellites. Using the mixed differenced estimation model, the prototype system can realize high-efficient real-time satellite absolute clock estimation with no constant clock-bias and can be used for high-frequency augmentation message updating (such as 1 Hz). The real-time augmentation message signal-in-space ranging error (SISRE), a comprehensive accuracy of orbit and clock and effecting the users' actual positioning performance, is introduced to evaluate and analyze the performance of GPS + BeiDou + Galileo global real-time augmentation positioning system. The statistical analysis of real-time augmentation message SISRE is about 4-7 cm for GPS, whlile 10 cm for Beidou IGSO/MEO, Galileo and about 30 cm

Performance Assessment of a Gnss-Based Troposphere Path Delay Estimation Software

Science.gov (United States)

Mariotti, Gilles; Avanzi, Alessandro; Graziani, Alberto; Tortora, Paolo

2013-04-01

Error budgets of Deep Space Radio Science experiments are heavily affected by interplanetary and Earth transmission media, that corrupt, due to their non-unitary refraction index, the radiometric information of signals coming from the spacecraft. An effective removal of these noise sources is crucial to achieve the accuracy and signal stability levels required by radio science applications. Depending on the nature of these refractions, transmission media are divided into dispersive (that consists of ionized particles, i.e. Solar Wind and Ionosphere) and non-dispersive ones (the refraction is caused by neutral particles: Earth Troposphere). While dispersive noises are successfully removed by multifrequency combinations (as for GPS with the well-known ionofree combination), the most accurate estimation of tropospheric noise is obtained using microwave radiometers (MWR). As the use of MWRs suffers from strong operational limitations (rain and heavy clouds conditions), the GNSS-based processing is still widely adopted to provide a cost-effective, all-weather condition estimation of the troposphere path delay. This work describes the development process and reports the results of a GNSS analysis code specifically aimed to the estimation of the path delays introduced by the troposphere above deep space complexes, to be used for the calibration of Range and Doppler radiometric data. The code has been developed by the Radio Science Laboratory of the University of Bologna in Forlì, and is currently in the testing phase. To this aim, the preliminary output is compared to MWR measurements and IGS TropoSINEX products in order to assess the reliability of the estimate. The software works using ionofree carrier-phase observables and is based upon a double-difference approach, in which the GNSS receiver placed nearby the Deep Space receiver acts as the rover station. Several baselines are then created with various IGS and EUREF stations (master or reference stations) in order to

An SDR-Based Real-Time Testbed for GNSS Adaptive Array Anti-Jamming Algorithms Accelerated by GPU

Directory of Open Access Journals (Sweden)

Hailong Xu

2016-03-01

Full Text Available Nowadays, software-defined radio (SDR has become a common approach to evaluate new algorithms. However, in the field of Global Navigation Satellite System (GNSS adaptive array anti-jamming, previous work has been limited due to the high computational power demanded by adaptive algorithms, and often lack flexibility and configurability. In this paper, the design and implementation of an SDR-based real-time testbed for GNSS adaptive array anti-jamming accelerated by a Graphics Processing Unit (GPU are documented. This testbed highlights itself as a feature-rich and extendible platform with great flexibility and configurability, as well as high computational performance. Both Space-Time Adaptive Processing (STAP and Space-Frequency Adaptive Processing (SFAP are implemented with a wide range of parameters. Raw data from as many as eight antenna elements can be processed in real-time in either an adaptive nulling or beamforming mode. To fully take advantage of the parallelism resource provided by the GPU, a batched method in programming is proposed. Tests and experiments are conducted to evaluate both the computational and anti-jamming performance. This platform can be used for research and prototyping, as well as a real product in certain applications.

Precise Receiver Clock Offset Estimations According to Each Global Navigation Satellite Systems (GNSS) Timescales

Science.gov (United States)

Thongtan, Thayathip; Tirawanichakul, Pawit; Satirapod, Chalermchon

2017-12-01

Each GNSS constellation operates its own system times; namely, GPS system time (GPST), GLONASS system time (GLONASST), BeiDou system time (BDT) and Galileo system time (GST). They could be traced back to Coordinated Universal Time (UTC) scale and are aligned to GPST. This paper estimates the receiver clock offsets to three timescales: GPST, GLONASST and BDT. The two measurement scenarios use two identical multi-GNSS geodetic receivers connected to the same geodetic antenna through a splitter. One receiver is driven by its internal oscillators and another receiver is connected to the external frequency oscillators, caesium frequency standard, kept as the Thailand standard time scale at the National Institute of Metrology (Thailand) called UTC(NIMT). The three weeks data are observed at 30 seconds sample rate. The receiver clock offsets with respected to the three system time are estimated and analysed through the geodetic technique of static Precise Point Positioning (PPP) using a data processing software developed by Wuhan University - Positioning And Navigation Data Analyst (PANDA) software. The estimated receiver clock offsets are around 32, 33 and 18 nanoseconds from GPST, GLONASST and BDT respectively. This experiment is initially stated that each timescale is inter-operated with GPST and further measurements on receiver internal delay has to be determined for clock comparisons especially the high accuracy clock at timing laboratories.

On biases in precise point positioning with multi-constellation and multi-frequency GNSS data

International Nuclear Information System (INIS)

El-Mowafy, A; Deo, M; Rizos, C

2016-01-01

Various types of biases in Global Navigation Satellite System (GNSS) data preclude integer ambiguity fixing and degrade solution accuracy when not being corrected during precise point positioning (PPP). In this contribution, these biases are first reviewed, including satellite and receiver hardware biases, differential code biases, differential phase biases, initial fractional phase biases, inter-system receiver time biases, and system time scale offset. PPP models that take account of these biases are presented for two cases using ionosphere-free observations. The first case is when using primary signals that are used to generate precise orbits and clock corrections. The second case applies when using additional signals to the primary ones. In both cases, measurements from single and multiple constellations are addressed. It is suggested that the satellite-related code biases be handled as calibrated quantities that are obtained from multi-GNSS experiment products and the fractional phase cycle biases obtained from a network to allow for integer ambiguity fixing. Some receiver-related biases are removed using between-satellite single differencing, whereas other receiver biases such as inter-system biases are lumped with differential code and phase biases and need to be estimated. The testing results show that the treatment of biases significantly improves solution convergence in the float ambiguity PPP mode, and leads to ambiguity-fixed PPP within a few minutes with a small improvement in solution precision. (paper)

Seismo-ionospheric anomalies and implications from recent GNSS observations in India and South-East Asia

Directory of Open Access Journals (Sweden)

C.D. Reddy

2016-01-01

Full Text Available The lithosphere and the atmosphere/ionosphere, continuously exchange energy through various coupling mechanisms. Earthquake creates waves of energy, e.g. direct shock acoustic waves (SAWs and Rayleigh wave induced acoustic waves (RAWs. In the event of an earthquake occurring beneath the sea, atmospheric gravity waves (AGWs are also generated. If the earthquake is large enough (Mw > 6, SAWs, RAWs and AGWs induce detectable ionospheric plasma perturbations. Inferring the seismological information from these seismo-ionospheric manifestations is the subject that pertains to ionospheric seismology. Both ground and satellite based advanced radio techniques are being used in monitoring ionospheric plasma perturbations. In this study, seismo-ionospheric anomalies and implications from recent GNSS observations in India and South-East Asia are discussed, mainly pertaining to the following. (1 From the ionospheric plasma response to 2015 Nepal earthquake, the estimated group velocity for Andaman and Indian shield regions are 2100 ms−1 and 3900 ms−1 respectively and validated from ground measurements. (2 Atmospheric acoustic resonance at 4.0 mHz and a train of wave packet of TEC variation resulting from the beat phenomenon observed at the site ‘umlh’ and (3 GNSS-based tsunami warning which is going to be promising tool in augmenting the existing tsunami warning systems.

Time series of GNSS-derived ionospheric maps to detect anomalies as possible precursors of high magnitude earthquakes

Science.gov (United States)

Barbarella, M.; De Giglio, M.; Galeandro, A.; Mancini, F.

2012-04-01

The modification of some atmospheric physical properties prior to a high magnitude earthquake has been recently debated within the Lithosphere-Atmosphere-Ionosphere (LAI) Coupling model. Among this variety of phenomena the ionization of air at the higher level of the atmosphere, called ionosphere, is investigated in this work. Such a ionization occurrences could be caused by possible leaking of gases from earth crust and their presence was detected around the time of high magnitude earthquakes by several authors. However, the spatial scale and temporal domain over which such a disturbances come into evidence is still a controversial item. Even thought the ionospheric activity could be investigated by different methodologies (satellite or terrestrial measurements), we selected the production of ionospheric maps by the analysis of GNSS (Global Navigation Satellite Data) data as possible way to detect anomalies prior of a seismic event over a wide area around the epicentre. It is well known that, in the GNSS sciences, the ionospheric activity could be probed by the analysis of refraction phenomena occurred on the dual frequency signals along the satellite to receiver path. The analysis of refraction phenomena affecting data acquired by the GNSS permanent trackers is able to produce daily to hourly maps representing the spatial distribution of the ionospheric Total Electron Content (TEC) as an index of the ionization degree in the upper atmosphere. The presence of large ionospheric anomalies could be therefore interpreted in the LAI Coupling model like a precursor signal of a strong earthquake, especially when the appearance of other different precursors (thermal anomalies and/or gas fluxes) could be detected. In this work, a six-month long series of ionospheric maps produced from GNSS data collected by a network of 49 GPS permanent stations distributed within an area around the city of L'Aquila (Abruzzi, Italy), where an earthquake (M = 6.3) occurred on April 6, 2009

Jumps in GNSS coordinates time series, a simple and fast methodology to clean the data sets

Science.gov (United States)

Bruni, Sara; Zerbini, Susanna; Raicich, Fabio; Errico, Maddalena; Santi, Efisio

2014-05-01

GNSS coordinate time series often suffer from the presence of undesired offsets of different nature which may impair the reliable estimation of the long-period trend and that should be corrected in the original data sets. Examples of such discontinuities are those originated by earthquakes, monumentation problems, replacement/maintenance of the station equipment, change of the reference system and by a number of unforeseen events. We have developed an automated and fast data inspection procedure for estimating the time of occurrence and the magnitude of the jumps and for correcting the time series accordingly. These processing characteristics are important because many time series are now spanning almost two decades, and dense GNSS networks are becoming a reality. The procedure has been developed and tailored to GNSS data sets starting from the Sequential T-test Analysis of Regime Shifts (STARS) originally conceived by Rodionov (Geophys. Res. Lett., 31, L09204, 2004) in the context of climatic studies. This technique does not make any a priori assumption on the time of occurrence and on the magnitude of the discontinuities. A jump is detected and its magnitude estimated when, over two consecutive time windows of the same length, the mean value exhibits a statistically significant change. Three user-defined parameters are required: the cut-off length, L, representing the minimum time interval between two consecutive discontinuities, the significance level, p, of the exploited two-tailed Student t-test, and the Huber parameter, H, used to compute a weighted mean over the L-day intervals. The method has been tested on GPS coordinates time series of stations located in the southeastern Po Plain, in Italy. The series span more than 15 years and are affected by offsets of different nature. The methodology has proven to be effective, as confirmed by the comparison between the corrected GPS time series and those obtained by other co-located observation techniques such as

Integrating uncertainty propagation in GNSS radio occultation retrieval: from excess phase to atmospheric bending angle profiles

Science.gov (United States)

Schwarz, Jakob; Kirchengast, Gottfried; Schwaerz, Marc

2018-05-01

Global Navigation Satellite System (GNSS) radio occultation (RO) observations are highly accurate, long-term stable data sets and are globally available as a continuous record from 2001. Essential climate variables for the thermodynamic state of the free atmosphere - such as pressure, temperature, and tropospheric water vapor profiles (involving background information) - can be derived from these records, which therefore have the potential to serve as climate benchmark data. However, to exploit this potential, atmospheric profile retrievals need to be very accurate and the remaining uncertainties quantified and traced throughout the retrieval chain from raw observations to essential climate variables. The new Reference Occultation Processing System (rOPS) at the Wegener Center aims to deliver such an accurate RO retrieval chain with integrated uncertainty propagation. Here we introduce and demonstrate the algorithms implemented in the rOPS for uncertainty propagation from excess phase to atmospheric bending angle profiles, for estimated systematic and random uncertainties, including vertical error correlations and resolution estimates. We estimated systematic uncertainty profiles with the same operators as used for the basic state profiles retrieval. The random uncertainty is traced through covariance propagation and validated using Monte Carlo ensemble methods. The algorithm performance is demonstrated using test day ensembles of simulated data as well as real RO event data from the satellite missions CHAllenging Minisatellite Payload (CHAMP); Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC); and Meteorological Operational Satellite A (MetOp). The results of the Monte Carlo validation show that our covariance propagation delivers correct uncertainty quantification from excess phase to bending angle profiles. The results from the real RO event ensembles demonstrate that the new uncertainty estimation chain performs robustly. Together

Near real-time estimation of ionosphere vertical total electron content from GNSS satellites using B-splines in a Kalman filter

Science.gov (United States)

Erdogan, Eren; Schmidt, Michael; Seitz, Florian; Durmaz, Murat

2017-02-01

Although the number of terrestrial global navigation satellite system (GNSS) receivers supported by the International GNSS Service (IGS) is rapidly growing, the worldwide rather inhomogeneously distributed observation sites do not allow the generation of high-resolution global ionosphere products. Conversely, with the regionally enormous increase in highly precise GNSS data, the demands on (near) real-time ionosphere products, necessary in many applications such as navigation, are growing very fast. Consequently, many analysis centers accepted the responsibility of generating such products. In this regard, the primary objective of our work is to develop a near real-time processing framework for the estimation of the vertical total electron content (VTEC) of the ionosphere using proper models that are capable of a global representation adapted to the real data distribution. The global VTEC representation developed in this work is based on a series expansion in terms of compactly supported B-spline functions, which allow for an appropriate handling of the heterogeneous data distribution, including data gaps. The corresponding series coefficients and additional parameters such as differential code biases of the GNSS satellites and receivers constitute the set of unknown parameters. The Kalman filter (KF), as a popular recursive estimator, allows processing of the data immediately after acquisition and paves the way of sequential (near) real-time estimation of the unknown parameters. To exploit the advantages of the chosen data representation and the estimation procedure, the B-spline model is incorporated into the KF under the consideration of necessary constraints. Based on a preprocessing strategy, the developed approach utilizes hourly batches of GPS and GLONASS observations provided by the IGS data centers with a latency of 1 h in its current realization. Two methods for validation of the results are performed, namely the self consistency analysis and a comparison

Single-frequency receivers as master permanent stations in GNSS networks: precision and accuracy of the positioning in mixed networks

Science.gov (United States)

Dabove, Paolo; Manzino, Ambrogio Maria

2015-04-01

The use of GPS/GNSS instruments is a common practice in the world at both a commercial and academic research level. Since last ten years, Continuous Operating Reference Stations (CORSs) networks were born in order to achieve the possibility to extend a precise positioning more than 15 km far from the master station. In this context, the Geomatics Research Group of DIATI at the Politecnico di Torino has carried out several experiments in order to evaluate the achievable precision obtainable with different GNSS receivers (geodetic and mass-market) and antennas if a CORSs network is considered. This work starts from the research above described, in particular focusing the attention on the usefulness of single frequency permanent stations in order to thicken the existing CORSs, especially for monitoring purposes. Two different types of CORSs network are available today in Italy: the first one is the so called "regional network" and the second one is the "national network", where the mean inter-station distances are about 25/30 and 50/70 km respectively. These distances are useful for many applications (e.g. mobile mapping) if geodetic instruments are considered but become less useful if mass-market instruments are used or if the inter-station distance between master and rover increases. In this context, some innovative GNSS networks were developed and tested, analyzing the performance of rover's positioning in terms of quality, accuracy and reliability both in real-time and post-processing approach. The use of single frequency GNSS receivers leads to have some limits, especially due to a limited baseline length, the possibility to obtain a correct fixing of the phase ambiguity for the network and to fix the phase ambiguity correctly also for the rover. These factors play a crucial role in order to reach a positioning with a good level of accuracy (as centimetric o better) in a short time and with an high reliability. The goal of this work is to investigate about the

On $R^4$ terms and MHV amplitudes in N = 5,6 supergravity vacua of Type II superstrings

CERN Document Server

Bianchi, Massimo

2011-01-01

We compute one-loop threshold corrections to $R^4$ terms in N= 5,6 supergravity vacua of Type II superstrings. We then discuss non-perturbative corrections generated by asymmetric D-brane instantons. Finally we derive generating functions for MHV amplitudes at tree level in N = 5, 6 supergravities.

In situ preparation of Fe3O4 in a carbon hybrid of graphene nanoscrolls and carbon nanotubes as high performance anode material for lithium-ion batteries

Science.gov (United States)

Liu, Yuewen; Hassan Siddique, Ahmad; Huang, Heran; Fang, Qile; Deng, Wei; Zhou, Xufeng; Lu, Huanming; Liu, Zhaoping

2017-11-01

A new conductive carbon hybrid combining both reduced graphene nanoscrolls and carbon nanotubes (rGNSs-CNTs) is prepared, and used to host Fe3O4 nanoparticles through an in situ synthesis method. As an anode material for LIBs, the obtained Fe3O4@rGNSs-CNTs shows good electrochemical performance. At a current density of 0.1 A g-1, the anode material shows a high reversible capacity of 1232.9 mAh g-1 after 100 cycles. Even at a current density of 1 A g-1, it still achieves a high reversible capacity of 812.3 mAh g-1 after 200 cycles. Comparing with bare Fe3O4 and Fe3O4/rGO composite anode materials without nanoscroll structure, Fe3O4@rGNSs-CNTs shows much better rate capability with a reversible capacity of 605.0 and 500.0 mAh g-1 at 3 and 5 A g-1, respectively. The excellent electrochemical performance of the Fe3O4@rGNSs-CNTs anode material can be ascribed to the hybrid structure of rGNSs-CNTs, and their strong interaction with Fe3O4 nanoparticles, which on one hand provides more pathways for lithium ions and electrons, on the other hand effectively relieves the volume change of Fe3O4 during the charge-discharge process.

On the feasibility to integrate low-cost MEMS accelerometers and GNSS receivers

Science.gov (United States)

Benedetti, Elisa; Dermanis, Athanasios; Crespi, Mattia

2017-06-01

The aim of this research was to investigate the feasibility of merging the benefits offered by low-cost GNSS and MEMS accelerometers technology, in order to promote the diffusion of low-cost monitoring solutions. A merging approach was set up at the level of the combination of kinematic results (velocities and displacements) coming from the two kinds of sensors, whose observations were separately processed, following to the so called loose integration, which sounds much more simple and flexible thinking about the possibility of an easy change of the combined sensors. At first, the issues related to the difference in reference systems, time systems and measurement rate and epochs for the two sensors were faced with. An approach was designed and tested to transform into unique reference and time systems the outcomes from GPS and MEMS and to interpolate the usually (much) more dense MEMS observation to common (GPS) epochs. The proposed approach was limited to time-independent (constant) orientation of the MEMS reference system with respect to the GPS one. Then, a data fusion approach based on the use of Discrete Fourier Transform and cubic splines interpolation was proposed both for velocities and displacements: MEMS and GPS derived solutions are firstly separated by a rectangular filter in spectral domain, and secondly back-transformed and combined through a cubic spline interpolation. Accuracies around 5 mm for slow and fast displacements and better than 2 mm/s for velocities were assessed. The obtained solution paves the way to a powerful and appealing use of low-cost single frequency GNSS receivers and MEMS accelerometers for structural and ground monitoring applications. Some additional remarks and prospects for future investigations complete the paper.

Application of dGNSS in Alpine Ski Racing: Basis for Evaluating Physical Demands and Safety

Science.gov (United States)

Gilgien, Matthias; Kröll, Josef; Spörri, Jörg; Crivelli, Philip; Müller, Erich

2018-01-01

External forces, such as ground reaction force or air drag acting on athletes' bodies in sports, determine the sport-specific demands on athletes' physical fitness. In order to establish appropriate physical conditioning regimes, which adequately prepare athletes for the loads and physical demands occurring in their sports and help reduce the risk of injury, sport-and/or discipline-specific knowledge of the external forces is needed. However, due to methodological shortcomings in biomechanical research, data comprehensively describing the external forces that occur in alpine super-G (SG) and downhill (DH) are so far lacking. Therefore, this study applied new and accurate wearable sensor-based technology to determine the external forces acting on skiers during World Cup (WC) alpine skiing competitions in the disciplines of SG and DH and to compare these with those occurring in giant slalom (GS), for which previous research knowledge exists. External forces were determined using WC forerunners carrying a differential global navigation satellite system (dGNSS). Combining the dGNSS data with a digital terrain model of the snow surface and an air drag model, the magnitudes of ground reaction forces were computed. It was found that the applied methodology may not only be used to track physical demands and loads on athletes, but also to simultaneously investigate safety aspects, such as the effectiveness of speed control through increased air drag and ski–snow friction forces in the respective disciplines. Therefore, the component of the ground reaction force in the direction of travel (ski–snow friction) and air drag force were computed. This study showed that (1) the validity of high-end dGNSS systems allows meaningful investigations such as characterization of physical demands and effectiveness of safety measures in highly dynamic sports; (2) physical demands were substantially different between GS, SG, and DH; and (3) safety-related reduction of skiing speed might

Application of dGNSS in Alpine Ski Racing: Basis for Evaluating Physical Demands and Safety

Directory of Open Access Journals (Sweden)

Matthias Gilgien

2018-03-01

Full Text Available External forces, such as ground reaction force or air drag acting on athletes' bodies in sports, determine the sport-specific demands on athletes' physical fitness. In order to establish appropriate physical conditioning regimes, which adequately prepare athletes for the loads and physical demands occurring in their sports and help reduce the risk of injury, sport-and/or discipline-specific knowledge of the external forces is needed. However, due to methodological shortcomings in biomechanical research, data comprehensively describing the external forces that occur in alpine super-G (SG and downhill (DH are so far lacking. Therefore, this study applied new and accurate wearable sensor-based technology to determine the external forces acting on skiers during World Cup (WC alpine skiing competitions in the disciplines of SG and DH and to compare these with those occurring in giant slalom (GS, for which previous research knowledge exists. External forces were determined using WC forerunners carrying a differential global navigation satellite system (dGNSS. Combining the dGNSS data with a digital terrain model of the snow surface and an air drag model, the magnitudes of ground reaction forces were computed. It was found that the applied methodology may not only be used to track physical demands and loads on athletes, but also to simultaneously investigate safety aspects, such as the effectiveness of speed control through increased air drag and ski–snow friction forces in the respective disciplines. Therefore, the component of the ground reaction force in the direction of travel (ski–snow friction and air drag force were computed. This study showed that (1 the validity of high-end dGNSS systems allows meaningful investigations such as characterization of physical demands and effectiveness of safety measures in highly dynamic sports; (2 physical demands were substantially different between GS, SG, and DH; and (3 safety-related reduction of skiing

Application of dGNSS in Alpine Ski Racing: Basis for Evaluating Physical Demands and Safety.

Science.gov (United States)

Gilgien, Matthias; Kröll, Josef; Spörri, Jörg; Crivelli, Philip; Müller, Erich

2018-01-01

External forces, such as ground reaction force or air drag acting on athletes' bodies in sports, determine the sport-specific demands on athletes' physical fitness. In order to establish appropriate physical conditioning regimes, which adequately prepare athletes for the loads and physical demands occurring in their sports and help reduce the risk of injury, sport-and/or discipline-specific knowledge of the external forces is needed. However, due to methodological shortcomings in biomechanical research, data comprehensively describing the external forces that occur in alpine super-G (SG) and downhill (DH) are so far lacking. Therefore, this study applied new and accurate wearable sensor-based technology to determine the external forces acting on skiers during World Cup (WC) alpine skiing competitions in the disciplines of SG and DH and to compare these with those occurring in giant slalom (GS), for which previous research knowledge exists. External forces were determined using WC forerunners carrying a differential global navigation satellite system (dGNSS). Combining the dGNSS data with a digital terrain model of the snow surface and an air drag model, the magnitudes of ground reaction forces were computed. It was found that the applied methodology may not only be used to track physical demands and loads on athletes, but also to simultaneously investigate safety aspects, such as the effectiveness of speed control through increased air drag and ski-snow friction forces in the respective disciplines. Therefore, the component of the ground reaction force in the direction of travel (ski-snow friction) and air drag force were computed. This study showed that (1) the validity of high-end dGNSS systems allows meaningful investigations such as characterization of physical demands and effectiveness of safety measures in highly dynamic sports; (2) physical demands were substantially different between GS, SG, and DH; and (3) safety-related reduction of skiing speed might be

Angiotensin II Removes Kidney Resistance Conferred by Ischemic Preconditioning

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Hee-Seong Jang

2014-01-01

Full Text Available Ischemic preconditioning (IPC by ischemia/reperfusion (I/R renders resistance to the kidney. Strong IPC triggers kidney fibrosis, which is involved in angiotensin II (AngII and its type 1 receptor (AT1R signaling. Here, we investigated the role of AngII/AT1R signal pathway in the resistance of IPC kidneys to subsequent I/R injury. IPC of kidneys was generated by 30 minutes of bilateral renal ischemia and 8 days of reperfusion. Sham-operation was performed to generate control (non-IPC mice. To examine the roles of AngII and AT1R in IPC kidneys to subsequent I/R, IPC kidneys were subjected to either 30 minutes of bilateral kidney ischemia or sham-operation following treatment with AngII, losartan (AT1R blocker, or AngII plus losartan. IPC kidneys showed fibrotic changes, decreased AngII, and increased AT1R expression. I/R dramatically increased plasma creatinine concentrations in non-IPC mice, but not in IPC mice. AngII treatment in IPC mice resulted in enhanced morphological damage, oxidative stress, and inflammatory responses, with functional impairment, whereas losartan treatment reversed these effects. However, AngII treatment in non-IPC mice did not change I/R-induced injury. AngII abolished the resistance of IPC kidneys to subsequent I/R via the enhancement of oxidative stress and inflammatory responses, suggesting that the AngII/AT1R signaling pathway is associated with outcome in injury-experienced kidney.

Tidal analysis of GNSS data from a high resolution sensor network at Helheim Glacier

Science.gov (United States)

Martin, Ian; Aspey, Robin; Baugé, Tim; Edwards, Stuart; Everett, Alistair; James, Timothy; Loskot, Pavel; Murray, Tavi; O'Farrell, Tim; Rutt, Ian

2014-05-01

Changes in Greenland and Antarctic ice sheets due to ice flow/ice-berg calving are a major uncertainty affecting sea-level rise forecasts. Latterly GNSS (Global Navigation Satellite Systems) have been employed extensively to monitor such glacier dynamics. Until recently however, the favoured methodology has been to deploy sensors onto the glacier surface, collect data for a period of time, then retrieve and download the sensors. This approach works well in less dynamic environments where the risk of sensor loss is low. In more extreme environments e.g. approaching the glacial calving front, the risk of sensor loss and hence data loss increases dramatically. In order to provide glaciologists with new insights into flow dynamics and calving processes we have developed a novel sensor network to increase the robustness of data capture. We present details of the technological requirements for an in-situ Zigbee wireless streaming network infrastructure supporting instantaneous data acquisition from high resolution GNSS sensors thereby increasing data capture robustness. The data obtained offers new opportunities to investigate the interdependence of mass flow, uplift, velocity and geometry and the network architecture has been specifically designed for deployment by helicopter close to the calving front to yield unprecedented detailed information. Following successful field trials of a pilot three node network during 2012, a larger 20 node network was deployed on the fast-flowing Helheim glacier, south-east Greenland over the summer months of 2013. The utilisation of dual wireless transceivers in each glacier node, multiple frequencies and four 'collector' stations located on the valley sides creates overlapping networks providing enhanced capacity, diversity and redundancy of data 'back-haul', even close to 'floor' RSSI (Received Signal Strength Indication) levels around -100 dBm. Data loss through radio packet collisions within sub-networks are avoided through the

Maintenance of the Photovolatic Plants Using UAV Equipped with Low-cost GNSS RTK Receiver

DEFF Research Database (Denmark)

Bilal, Muhammad; Prasad, Ramjee; Nisi, Marco

2017-01-01

of low-cost GNSS RTK receiver, is the maintenance of photovoltaic (PV) plants using Unmanned Aerial Vehicle (UAV). This paper proposes a solution that aims at automating the maintenance of PV plant with enhanced reliability in a time and cost effective manner, which otherwise requires intermediate human...... intervention. The paper presents the architectural concept, system design, and end-to-end algorithm that plays a pivotal role in enabling the automatic report generation of PV plant status. Preliminary results of the proof-of-concept shows the feasibility of the proposed solution....

Les pneumopathies nosocomiales en réanimation de CHU Hassan II de Fès

Science.gov (United States)

Shimi, Abdelkarim; Touzani, Soumaya; Elbakouri, Nabil; Bechri, Brahim; Derkaoui, Ali; Khatouf, Mohammed

2015-01-01

L'objectif principal de notre étude était d'identifier les bactéries incriminées dans la pneumopathie nosocomiale (PN) au service de réanimation A1 du CHU Hassan II de Fès, en vue d'en améliorer la prise en charge et de diminuer la morbi-mortalité associée. Il s'agit d'une étude rétrospective et descriptive, menée du 1er janvier 2012 au 31 décembre 2013. Seules les infections pulmonaires survenant au-delà de 48 heures de l'admission du patient au service de réanimation ont été incluses. L'incidence de la PN était de 11,2%. Les Bacilles à Gram négatif (BGN) étaient retrouvés dans 48,5% des cas, le Staphylocoque Aureus dans 21,21% des cas et le Klebsiella Pneumoniae était dans 10,7% des cas. Le taux de mortalité était de 48,33%. L’âge, la gravité de la pathologie sous jacente et le retard de l'instauration d'une antibiothérapie adaptée étaient considérées comme facteurs de mauvais pronostic. L’étude de la résistance aux antibiotiques, montre une multirésistance surtout pour les BGN, dont il faut tenir compte en mettant en place une stratégie de prévention active. PMID:26966481

GNSS Positioning Performance Analysis Using PSO-RBF Estimation Model

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Jgouta Meriem

2017-06-01

Full Text Available Positioning solutions need to be more precise and available. The most frequent method used nowadays includes a GPS receiver, sometimes supported by other sensors. Generally, GPS and GNSS suffer from spreading perturbations that produce biases on pseudo-range measurements. With a view to optimize the use of the satellites received, we offer a positioning algorithm with pseudo range error modelling with the contribution of an appropriate filtering process. Extended Kalman Filter, The Rao- Blackwellized filter are among the most widely used algorithms to predict errors and to filter the high frequency noise. This paper describes a new method of estimating the pseudo-range errors based on the PSO-RBF model which achieves an optimal training criterion. This model is appropriate of its method to predict the GPS corrections for accurate positioning, it reduce the positioning errors at high velocities by more than 50% compared to the RLS or EKF methods.

GNSS-based multi-sensor system for structural monitoring applications

Science.gov (United States)

Bogusz, Janusz; Figurski, Mariusz; Nykiel, Grzegorz; Szolucha, Marcin; Wrona, Maciej

2012-03-01

In 2007 the Centre of Applied Geomatics of the Military University of Technology started measurements aimed at the monitoring of the dynamic state of the engineering structures using GNSS. The complexity of the problem forced us to apply an integrated system architecture. This concept is based on simultaneous measuring some selected elements of the structure using various types of sensors. Measurement information from numerous instruments is numerically integrated for determining the investigated parameter, e.g., the displacement vector. The CAG team performed the tests using such a system on the two permanent 500-meters long bridges, the temporary bridge crossing for military purposes and the 300-meters high chimney of the CHP station. The information about displacement vector together with the characteristic frequencies of the structure were determined using different techniques for increasing of its reliability. This paper presents the results of such tests, gives description of the integrated system designed in the CAG and brings forward with the plans for the future.

Consistency of different tropospheric models and mapping functions for precise GNSS processing

Science.gov (United States)

Graffigna, Victoria; Hernández-Pajares, Manuel; García-Rigo, Alberto; Gende, Mauricio

2017-04-01

The TOmographic Model of the IONospheric electron content (TOMION) software implements a simultaneous precise geodetic and ionospheric modeling, which can be used to test new approaches for real-time precise GNSS modeling (positioning, ionospheric and tropospheric delays, clock errors, among others). In this work, the software is used to estimate the Zenith Tropospheric Delay (ZTD) emulating real time and its performance is evaluated through a comparative analysis with a built-in GIPSY estimation and IGS final troposphere product, exemplified in a two-day experiment performed in East Australia. Furthermore, the troposphere mapping function was upgraded from Niell to Vienna approach. On a first scenario, only forward processing was activated and the coordinates of the Wide Area GNSS network were loosely constrained, without fixing the carrier phase ambiguities, for both reference and rover receivers. On a second one, precise point positioning (PPP) was implemented, iterating for a fixed coordinates set for the second day. Comparisons between TOMION, IGS and GIPSY estimates have been performed and for the first one, IGS clocks and orbits were considered. The agreement with GIPSY results seems to be 10 times better than with the IGS final ZTD product, despite having considered IGS products for the computations. Hence, the subsequent analysis was carried out with respect to the GIPSY computations. The estimates show a typical bias of 2cm for the first strategy and of 7mm for PPP, in the worst cases. Moreover, Vienna mapping function showed in general a fairly better agreement than Niell one for both strategies. The RMS values' were found to be around 1cm for all studied situations, with a slightly fitter performance for the Niell one. Further improvement could be achieved for such estimations with coefficients for the Vienna mapping function calculated from raytracing as well as integrating meteorological comparative parameters.

A Climate Benchmark of Upper Air Temperature Observations from GNSS Radio Occultation

Science.gov (United States)

Ao, C. O.; Mannucci, A. J.; Leroy, S. S.; Verkhoglyadova, O. P.

2017-12-01

GPS (Global Positioning System), or more generally Global Navigation Satellite System (GNSS), radio occultation (RO) is a remote sensing technique that produces highly accurate temperature in the upper troposphere and lower stratosphere across the globe with fine vertical resolution. Its fundamental measurement is the time delay of the microwave signal as it travels from a GNSS satellite to the receiver in low Earth orbit. With a relatively simple physical retrieval, the uncertainty in the derived temperature can be traced rigorously through the retrieval chain back to the raw measurements. The high absolute accuracy of RO allows these observations to be assimilated without bias correction in numerical weather prediction models and provides an anchor for assimilating other types of observations. The high accuracy, coupled with long-term stability, makes RO valuable in detecting decadal temperature trends. In this presentation, we will summarize the current state of RO observations and show temperature trends derived from 15 years of RO data in the upper troposphere and lower stratosphere. We will discuss our recent efforts in developing retrieval algorithms that are more tailored towards climate applications. Despite the relatively robust "self-calibrating" nature of RO observations, disparity in receiver hardware and software may introduce subtle differences that need to be carefully addressed. While the historic RO data record came from relatively homogeneous hardware based largely on NASA/JPL design (e.g., CHAMP and COSMIC), the future data will likely be comprised of a diverse set of observations from Europe, China, and various commercial data providers. In addition, the use of non-GPS navigation systems will become more prevalent. We will discuss the challenges involved in establishing a long-term RO climate data record from a suite of research and operational weather satellites with changes in instrumentation and coverage.

Current status of the EPOS WG4 - GNSS and Other Geodetic Data

Science.gov (United States)

Fernandes, Rui; Bastos, Luisa; Bruyninx, Carine; D'Agostino, Nicola; Dousa, Jan; Ganas, Athanassios; Lidberg, Martin; Nocquet, Jean-Mathieu

2014-05-01

WG4 - "EPOS Geodetic Data and Other Geodetic Data" is the Working Group of the EPOS project in charge of defining and preparing the integration of the existing Pan-European Geodetic Infrastructures that will support European Geosciences, which is the ultimate goal of the EPOS project. The WG4 is formed by representatives of the participating EPOS countries (23) but it is also open to the entire geodetic community. In fact, WG4 also already includes members from countries that formally are not integrating EPOS in this first step. The geodetic component of EPOS (WG4) is dealing essentially with Research Infrastructures focused on continuous operating GNSS (cGNSS) in the current phase. The option of concentrating the efforts on the presently most generalized geodetic tool supporting research on Solid Earth was decided in order to optimize the existing resources. Nevertheless, WG4 will continue to pursue the development of tools and methodologies that permit the access of the EPOS community to other geodetic information (e.g., gravimetry). Furthermore, although the focus is on Solid Earth applications, other research and technical applications (e.g., reference frames, meteorology, space weather) can also benefit from the efforts of WG4 EPOS towards the optimization of the geodetic resources in Europe. We will present and discuss the plans for the implementation of the thematic and core services (TCS) for geodetic data within EPOS and the related business plan. We will focus on strategies towards the implementation of the best solutions that will permit to the end-users, and in particular geo-scientists, to access the geodetic data, derived solutions, and associated metadata using transparent and uniform processes. Five pillars have been defined proposed for the TCS: Dissemination, Preservation, Monitoring, and Analysis of geodetic data plus the Support and Governance Infrastructure. Current proposals and remaining open questions will be discussed.

Altimetria GNSS de precisão aplicada ao monitoramento da dinâmica sedimentar costeira de curta duração em escala regional

Directory of Open Access Journals (Sweden)

Marcelo Soares Teles Santos

Full Text Available Este trabalho apresenta metodologia utilizada na altimetria GNSS de precisão aplicada em estudos costeiros de praias arenosas localizadas no Litoral Setentrional do Rio Grande do Norte, baseada em cálculo, modelagem e remoção da Componente Sistemática (CS do modelo geoidal. Os métodos foram aplicados e avaliados utilizando o modelo geoidal MAPGEO. O cálculo da CS foi realizado em Referências de Nível (RNs localizadas na área de estudo pela subtração entre as alturas geoidais gravimétricas, obtidas pelo modelo geoidal, e as geométricas, obtidas pelo posicionamento GNSS em RNs. Após modelagem e remoção da CS, por um modelo superfície polinomial quadrático, a CS calculada, com média de -0,498 m, Desvio Padrão (DP de 0,110 m e Erro Quadrático Médio (EQM de 0,509 m, passou a ter média nula, DP de 0,065 m e EQM de 0,062 m. Avaliações realizadas a partir de pontos de controle externos ao modelo mostraram que a metodologia forneceu acurácia decimétrica à altimetria GNSS, adequada ao monitoramento da elevada dinâmica sedimentar em ambientes costeiros, fato comprovado no estudo de caso apresentado.

Impacts of Earth rotation parameters on GNSS ultra-rapid orbit prediction: Derivation and real-time correction

Science.gov (United States)

Wang, Qianxin; Hu, Chao; Xu, Tianhe; Chang, Guobin; Hernández Moraleda, Alberto

2017-12-01

Analysis centers (ACs) for global navigation satellite systems (GNSSs) cannot accurately obtain real-time Earth rotation parameters (ERPs). Thus, the prediction of ultra-rapid orbits in the international terrestrial reference system (ITRS) has to utilize the predicted ERPs issued by the International Earth Rotation and Reference Systems Service (IERS) or the International GNSS Service (IGS). In this study, the accuracy of ERPs predicted by IERS and IGS is analyzed. The error of the ERPs predicted for one day can reach 0.15 mas and 0.053 ms in polar motion and UT1-UTC direction, respectively. Then, the impact of ERP errors on ultra-rapid orbit prediction by GNSS is studied. The methods for orbit integration and frame transformation in orbit prediction with introduced ERP errors dominate the accuracy of the predicted orbit. Experimental results show that the transformation from the geocentric celestial references system (GCRS) to ITRS exerts the strongest effect on the accuracy of the predicted ultra-rapid orbit. To obtain the most accurate predicted ultra-rapid orbit, a corresponding real-time orbit correction method is developed. First, orbits without ERP-related errors are predicted on the basis of ITRS observed part of ultra-rapid orbit for use as reference. Then, the corresponding predicted orbit is transformed from GCRS to ITRS to adjust for the predicted ERPs. Finally, the corrected ERPs with error slopes are re-introduced to correct the predicted orbit in ITRS. To validate the proposed method, three experimental schemes are designed: function extrapolation, simulation experiments, and experiments with predicted ultra-rapid orbits and international GNSS Monitoring and Assessment System (iGMAS) products. Experimental results show that using the proposed correction method with IERS products considerably improved the accuracy of ultra-rapid orbit prediction (except the geosynchronous BeiDou orbits). The accuracy of orbit prediction is enhanced by at least 50

Navigation capabilities of mid-cost GNSS/INS vs. smartphone analysis and comparison in urban navigation scenarios

OpenAIRE

Martí, Luis; García, Jesús; Molina, José M.

2014-01-01

Proceedings of: 17th International Conference on Information Fusion (FUSION 2014): Salamanca, Spain 7-10 July 2014. High accuracy navigation usually require expensive sensors and/or its careful integration into a complex and finely tuned system. Smartphones pack a high number of sensors in a portable format, becoming a source of low-quality information with a high heterogeneity and redundancy. This work compares pure GNSS/INS capabilities on both types of platform, and discuss the weakness...

First Zenith Total Delay and Integrated Water Vapour Estimates from the Near Real-Time GNSS Data Processing Systems at the University of Luxembourg

Science.gov (United States)

Ahmed, F.; Teferle, F. N.; Bingley, R. M.

2012-04-01

Since September 2011 the University of Luxembourg in collaboration with the University of Nottingham has been setting up two near real-time processing systems for ground-based GNSS data for the provision of zenith total delay (ZTD) and integrated water vapour (IWV) estimates. Both systems are based on Bernese v5.0, use the double-differenced network processing strategy and operate with a 1-hour (NRT1h) and 15-minutes (NRT15m) update cycle. Furthermore, the systems follow the approach of the E-GVAP METO and IES2 systems in that the normal equations for the latest data are combined with those from the previous four updates during the estimation of the ZTDs. NRT1h currently takes the hourly data from over 130 GNSS stations in Europe whereas NRT15m is primarily using the real-time streams of EUREF-IP. Both networks include additional GNSS stations in Luxembourg, Belgium and France. The a priori station coordinates for all of these stem from a moving average computed over the last 20 to 50 days and are based on the precise point positioning processing strategy. In this study we present the first ZTD and IWV estimates obtained from the NRT1h and NRT15m systems in development at the University of Luxembourg. In a preliminary evaluation we compare their performance to the IES2 system at the University of Nottingham and find the IWV estimates to agree at the sub-millimetre level.

Rigorous Performance Evaluation of Smartphone GNSS/IMU Sensors for ITS Applications

Directory of Open Access Journals (Sweden)

Vassilis Gikas

2016-08-01

Full Text Available With the rapid growth in smartphone technologies and improvement in their navigation sensors, an increasing amount of location information is now available, opening the road to the provision of new Intelligent Transportation System (ITS services. Current smartphone devices embody miniaturized Global Navigation Satellite System (GNSS, Inertial Measurement Unit (IMU and other sensors capable of providing user position, velocity and attitude. However, it is hard to characterize their actual positioning and navigation performance capabilities due to the disparate sensor and software technologies adopted among manufacturers and the high influence of environmental conditions, and therefore, a unified certification process is missing. This paper presents the analysis results obtained from the assessment of two modern smartphones regarding their positioning accuracy (i.e., precision and trueness capabilities (i.e., potential and limitations based on a practical but rigorous methodological approach. Our investigation relies on the results of several vehicle tracking (i.e., cruising and maneuvering tests realized through comparing smartphone obtained trajectories and kinematic parameters to those derived using a high-end GNSS/IMU system and advanced filtering techniques. Performance testing is undertaken for the HTC One S (Android and iPhone 5s (iOS. Our findings indicate that the deviation of the smartphone locations from ground truth (trueness deteriorates by a factor of two in obscured environments compared to those derived in open sky conditions. Moreover, it appears that iPhone 5s produces relatively smaller and less dispersed error values compared to those computed for HTC One S. Also, the navigation solution of the HTC One S appears to adapt faster to changes in environmental conditions, suggesting a somewhat different data filtering approach for the iPhone 5s. Testing the accuracy of the accelerometer and gyroscope sensors for a number of

The GNSS polarimetric radio-occultation technique to sense precipitation events: a new concept to be tested aboard PAZ Low Earth Satellite

Science.gov (United States)

Tomás, Sergio; Oliveras, Santi; Cardellach, Estel; Rius, Antonio

2013-04-01

The Radio Occultation and Heavy Precipitation (ROHP) experiment, to be conducted aboard the Spanish PAZ satellite, consists of a radio occultation (RO) mission provided with dual-polarization capabilities. The research with polarimetric RO data has the goal of assessing the capabilities and limitations of this technique to infer profiles of heavy precipitation. The technique aims to provide vertical profiles of precipitation simultaneously to the vertical profiles of thermodynamic parameters (standard RO products) perfectly collocated both in space and time. If successful, the polarimetric RO will represent the first technique able to provide these complementary information on precipitation. This is a relevant input for studies on heavy and violent rainfall events, which being poorly represented by the current-generation of Numerical Weather Prediction and General Circulation Models appear to be difficult to forecast on all time-scales. The Low Earth Orbiter hosting this experiment, to be launched in 2013, will orbit at 500 km altitude in a near-Polar orbit. The Radio Occulation payload includes a RO GNSS receiver and a dual polarization (H/V) limb oriented antenna to capture the signals of setting GNSS transmitters. NOAA and UCAR participate in the ground-segment of the radiometric experiment to enable near-real time dissemination of the level-1 standard RO products. The space-based GNSS RO technique scans the atmosphere vertically at fine resolution (close to 300 meter in the troposphere) by precisely measure the delay between a GNSS transmitter and a GNSS receiver aboard a Low Earth Orbiter, when the former is setting below or rising above the Earth limb. The standard, thermodynamical, products are extracted from the excess delay induced by the atmosphere at different layers. This presentation will not focus on this well-established application, but a novel concept using polarimetry to also retrieve rain information. The precipitation-measurement principle is

The Proposal to “Snapshot” Raim Method for Gnss Vessel Receivers Working in Poor Space Segment Geometry

Directory of Open Access Journals (Sweden)

Nowak Aleksander

2015-12-01

Full Text Available Nowadays, we can observe an increase in research on the use of small unmanned autonomous vessel (SUAV to patrol and guiding critical areas including harbours. The proposal to “snapshot” RAIM (Receiver Autonomous Integrity Monitoring method for GNSS receivers mounted on SUAV operating in poor space segment geometry is presented in the paper. Existing “snapshot” RAIM methods and algorithms which are used in practical applications have been developed for airborne receivers, thus two main assumptions have been made. The first one is that the geometry of visible satellites is strong. It means that the exclusion of any satellite from the positioning solution don’t cause significant deterioration of Dilution of Precision (DOP coefficients. The second one is that only one outlier could appear in pseudorange measurements. In case of SUAV operating in harbour these two assumptions cannot be accepted. Because of their small dimensions, GNSS antenna is only a few decimetres above sea level and regular ships, buildings and harbour facilities block and reflect satellite signals. Thus, different approach to “snapshot” RAIM is necessary. The proposal to method based on analyses of allowable maximal separation of positioning sub-solutions with using some information from EGNOS messages is described in the paper. Theoretical assumptions and results of numerical experiments are presented.

Millimetre Level Accuracy GNSS Positioning with the Blind Adaptive Beamforming Method in Interference Environments

Directory of Open Access Journals (Sweden)

Saeed Daneshmand

2016-10-01

Full Text Available The use of antenna arrays in Global Navigation Satellite System (GNSS applications is gaining significant attention due to its superior capability to suppress both narrowband and wideband interference. However, the phase distortions resulting from array processing may limit the applicability of these methods for high precision applications using carrier phase based positioning techniques. This paper studies the phase distortions occurring with the adaptive blind beamforming method in which satellite angle of arrival (AoA information is not employed in the optimization problem. To cater to non-stationary interference scenarios, the array weights of the adaptive beamformer are continuously updated. The effects of these continuous updates on the tracking parameters of a GNSS receiver are analyzed. The second part of this paper focuses on reducing the phase distortions during the blind beamforming process in order to allow the receiver to perform carrier phase based positioning by applying a constraint on the structure of the array configuration and by compensating the array uncertainties. Limitations of the previous methods are studied and a new method is proposed that keeps the simplicity of the blind beamformer structure and, at the same time, reduces tracking degradations while achieving millimetre level positioning accuracy in interference environments. To verify the applicability of the proposed method and analyze the degradations, array signals corresponding to the GPS L1 band are generated using a combination of hardware and software simulators. Furthermore, the amount of degradation and performance of the proposed method under different conditions are evaluated based on Monte Carlo simulations.

Complex analysis of the ionospheric response to operation of ``Progress'' cargo spacecraft according to the data of GNSS receivers in Baikal region

Science.gov (United States)

Ishin, Artem; Voeykov, Sergey; Perevalova, Natalia; Khakhinov, Vitaliy

2017-12-01

As a part of the Plasma-Progress and Radar-Progress space experiments conducted from 2006 to 2014, effects of the Progress spacecraft engines on the ionosphere have been studied using data from Global Navigation Satellite System (GNSS) receivers. 72 experiments have been carried out. All these experiments were based on data from the International GNSS Service (IGS) to record ionospheric plasma irregularities caused by engine operation. 35 experiments used data from the ISTP SB RAS network SibNet. The analysis of the spatio-temporal structure of total electron content (TEC) variations has shown that the problem of identifying the TEC response to engine operation is complicated by a number of factors: 1) the engine effect on ionospheric plasma is strongly localized in space and has a relatively low intensity; 2) a small number of satellite-receiver radio rays due to the limited number of GNSS stations, particularly before 2013; 3) a potential TEC response is masked with background ionospheric disturbances of various intensities. However, TEC responses are identified with certainty when a satellite-receiver radio ray crosses a disturbed region within minutes after the impact. TEC responses have been registered in 7 experiments (10 % of cases). The amplitude of ionospheric response (0.3-0.16 TECU) exceeded the background TEC variations (~0.25 TECU) several times. The TEC data indicate that the ionospheric irregularity lifetime is from 4 to 10 minutes. According to the estimates we made, the transverse size of irregularities is from 12 to 30 km.

Coulomb stress change of crustal faults in Japan for 21 years, estimated from GNSS displacement

Science.gov (United States)

Nishimura, T.

2017-12-01

Coulomb stress is one of the simplest index to show how the fault is close to a brittle failure (e.g., earthquake). Many previous studies used the Coulomb stress change (ΔCFS) to evaluate whether the fault approaches failure and successfully explained an earthquake triggered by previous earthquakes and volcanic sources. Most studies use a model of a half-space medium with given rheological properties, boundary conditions, dislocation, etc. to calculate ΔCFS. However, Ueda and Takahashi (2005) proposed to calculate DCFS directly from surface displacement observed by GNSS. There are 6 independent components of stress tensor in an isotropic elastic medium. On the surface of the half-space medium, 3 components should be zero because of no traction on the surface. This means the stress change on the surface is calculated from the surface strain change using Hooke's law. Although an earthquake does not occur on surface, the stress change on the surface may approximate that at a depth of a shallow crustal earthquake (e.g., 10 km) if the source is far from the point at which we calculate the stress change. We tested it by comparing ΔCFS from the surface displacement and that from elastic fault models for past earthquakes. We first estimate a strain change with a method of Shen et al.(1996 JGR) from surface displacement and then calculate ΔCFS for a targeted focal mechanism. Although ΔCFS in the vicinity of the source fault cannot be reproduced from the surface displacement, surface displacement gives a good approximation of ΔCFS in a region 50 km away from the source if the target mechanism is a vertical strike-slip fault. It suggests that GNSS observation can give useful information on a recent change of earthquake potential. We, therefore, calculate the temporal evolution of ΔCFS on active faults in southwest Japan from April 1996 using surface displacement at GNSS stations. We used parameters for the active faults used for evaluation of strong motion by the

The GNSS Component of the Seismic Monitoring System in Chile

Science.gov (United States)

Barrientos, S. E.

2016-12-01

Chile is amongst the most seismically active countries in the world. Since mid-XVI Century, a magnitude 8 or more earthquake has taken place every dozen of years, as an average. In the last 100 years, more than ten events with magnitudes around 8 or larger have taken place in this part of world. Three events with M>8 have taken place only in the last six years. The largest earthquake ever recorded took place in May, 1960, in southern Chile. Such extreme seismic activity is the result of the interaction of the Nazca, Antarctic, Scotia and South American plates in southwestern South America where Chile is located. These megathrust earthquakes exhibit long rupture regions reaching several hundreds of km with fault displacements of several tens of meters. At least eighteen of these earthquakes have generated local tsunamis with runups larger than 4 m -including events in 2010, 2014 and 2015- therefore it is mandatory to establish a system with capabilities to rapidly evaluate the tsunamigenic potential of these events. In 2013, the newly created National Seismological Center (CSN) of the University of Chile was tasked to upgrade the countrýs seismic network by increasing the numbers of real-time monitoring stations. The most important change to previous practices is the establishment of a GNSS network composed by 130 devices, in addition to the incorporation of 65 new collocated broadband and strong motion instruments. Additional 297 strong motion instruments for engineering purposes complement the system. Forty units -of the 130 devices- present an optional RTX capability, where satellite orbits and clock corrections are sent to the field device producing a 1-Hz position stream at 4-cm level. First records of ground displacement -using this technology-were recorded at the time of the largest aftershock (Mw=7.6) of the sequence that affected northern Chile in 2014. The CSN is currently developing automatic detectors and amplitude estimators of displacement from the

Boundary Layer Ducting of Low-elevation GNSS Ocean Reflected Signals

DEFF Research Database (Denmark)

Høeg, Per; von Benzon, Hans-Henrik; Durgonics, Tibor

for the data retrievals and the precision and the accuracy, are of interest for assessing the observational data content.Simulations of the low-elevation ocean reflected GNSS signal reveal a ducting of the signalwhen applying a model of the boundary layer. This effect is presented during varying conditions...... of the sea surface roughness, ocean wind and temperature, density and gradient of the water vapor profile in the boundary layer.The model for the sea surface roughness impedance, wind speed, and rms ocean wave-heightshow a stronger signal damping for a smoother ocean surfaces (sea state 0) compared...... to a rough sea (sea state 4). While the real part of the signal shows the reverse effect. At the same time the reflection zone enhances for rough sea states. Simulations, including a standard atmosphere and a boundary layer, give a significant ducting of the received signal, leading to a much larger...

An immuno-wall microdevice exhibits rapid and sensitive detection of IDH1-R132H mutation specific to grade II and III gliomas

Science.gov (United States)

Yamamichi, Akane; Kasama, Toshihiro; Ohka, Fumiharu; Suzuki, Hiromichi; Kato, Akira; Motomura, Kazuya; Hirano, Masaki; Ranjit, Melissa; Chalise, Lushun; Kurimoto, Michihiro; Kondo, Goro; Aoki, Kosuke; Kaji, Noritada; Tokeshi, Manabu; Matsubara, Toshio; Senga, Takeshi; Kaneko, Mika K.; Suzuki, Hidenori; Hara, Masahito; Wakabayashi, Toshihiko; Baba, Yoshinobu; Kato, Yukinari; Natsume, Atsushi

2016-01-01

World Health Organization grade II and III gliomas most frequently occur in the central nervous system (CNS) in adults. Gliomas are not circumscribed; tumor edges are irregular and consist of tumor cells, normal brain tissue, and hyperplastic reactive glial cells. Therefore, the tumors are not fully resectable, resulting in recurrence, malignant progression, and eventual death. Approximately 69-80% of grade II and III gliomas harbor mutations in the isocitrate dehydrogenase 1 gene (IDH1), of which 83-90% are found to be the IDH1-R132H mutation. Detection of the IDH1-R132H mutation should help in the differential diagnosis of grade II and III gliomas from other types of CNS tumors and help determine the boundary between the tumor and normal brain tissue. In this study, we established a highly sensitive antibody-based device, referred to as the immuno-wall, to detect the IDH1-R132H mutation in gliomas. The immuno-wall causes an immunoreaction in microchannels fabricated using a photo-polymerizing polymer. This microdevice enables the analysis of the IDH1 status with a small sample within 15 min with substantially high sensitivity. Our results suggested that 10% content of the IDH1-R132H mutation in a sample of 0.33 μl volume, with 500 ng protein, or from 500 cells is theoretically sufficient for the analysis. The immuno-wall device will enable the rapid and highly sensitive detection of the IDH1-R132H mutation in routine clinical practice.

Integrating uncertainty propagation in GNSS radio occultation retrieval: from excess phase to atmospheric bending angle profiles

Directory of Open Access Journals (Sweden)

J. Schwarz

2018-05-01

Full Text Available Global Navigation Satellite System (GNSS radio occultation (RO observations are highly accurate, long-term stable data sets and are globally available as a continuous record from 2001. Essential climate variables for the thermodynamic state of the free atmosphere – such as pressure, temperature, and tropospheric water vapor profiles (involving background information – can be derived from these records, which therefore have the potential to serve as climate benchmark data. However, to exploit this potential, atmospheric profile retrievals need to be very accurate and the remaining uncertainties quantified and traced throughout the retrieval chain from raw observations to essential climate variables. The new Reference Occultation Processing System (rOPS at the Wegener Center aims to deliver such an accurate RO retrieval chain with integrated uncertainty propagation. Here we introduce and demonstrate the algorithms implemented in the rOPS for uncertainty propagation from excess phase to atmospheric bending angle profiles, for estimated systematic and random uncertainties, including vertical error correlations and resolution estimates. We estimated systematic uncertainty profiles with the same operators as used for the basic state profiles retrieval. The random uncertainty is traced through covariance propagation and validated using Monte Carlo ensemble methods. The algorithm performance is demonstrated using test day ensembles of simulated data as well as real RO event data from the satellite missions CHAllenging Minisatellite Payload (CHAMP; Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC; and Meteorological Operational Satellite A (MetOp. The results of the Monte Carlo validation show that our covariance propagation delivers correct uncertainty quantification from excess phase to bending angle profiles. The results from the real RO event ensembles demonstrate that the new uncertainty estimation chain performs

ALGORITHMS VARIANTS OF ELABORATION OF THE PRECISE GNSS NETWORK ESTABLISHED FOR GEODETIC SERVICE OF BUILDING OF THE MINING FACILITY

Directory of Open Access Journals (Sweden)

Ryszard MIELIMĄKA

2014-10-01

Full Text Available The article presents the problem of the usage of post‐processing services of the ASG‐EUPOS system on the example of GNSS network established for geodetic service of building of the inclined drift, to make coal deposit accessible, and also building associated objects. For the purpose of geodetic service of construction realization network was established outside the planned objects. The network consists of six new ground points and four control points belonging to ASG‐EUPOS network. Simultaneous, static measurements of the network were performed in three‐hour observation session, using multi‐frequency and multi‐system satellite receivers – Trimble R8. The paper presents three variants of post‐processing of the observation results. Calculations were performed using POZGEO‐D service and geodetic software package GEONET. The results of the calculation process revealed, that homogeneous vector networks should be adjusted on the ellipsoid or in the geocentric system. Model of adjustment of the vector network on the plane adopted in the GEONET software package should not be applied for elaboration of this type of network (long reference vectors more than 50km.

Bg1II polymorphism of the epidermal growth factor receptor (EGF-R) gene

Energy Technology Data Exchange (ETDEWEB)

Biunno, I; Pozzi, M R; Radice, P; Mondini, P; Pierotti, M A; Porta, G D [Istituto Nazionale Tumori, Milan (Italy); Haley, J; Waterfield, M D [Ludwig Institute for Cancer Research, London (England)

1988-08-11

A 770 bp cDNA fragment was derived from the cytoplasmic portion of the EGF-R (ref. Libermann et al., 1985). Bg1II identifies 4 invariant bands of 7.0, 5.0, 3.5 and 1.2 kb and a two allele polymorphism with a band of either 10.6 kb (lane 1) or 9.4 kb (lane 3). An heterozygote individual is represented. The frequency was analyzed in 78 unrelated European Caucasians. Its chromosomal location was determined. Co-dominant segregation was demonstrated in three families of 12 individuals. A rare variant of 8.3 kb was seen in one chromosome out of the 144 examined. This allelic form has not yet been fully characterized.

Assimilation of GNSS radio occultation observations in GRAPES

Science.gov (United States)

Liu, Y.; Xue, J.

2014-07-01

This paper reviews the development of the global navigation satellite system (GNSS) radio occultation (RO) observations assimilation in the Global/Regional Assimilation and PrEdiction System (GRAPES) of China Meteorological Administration, including the choice of data to assimilate, the data quality control, the observation operator, the tuning of observation error, and the results of the observation impact experiments. The results indicate that RO data have a significantly positive effect on analysis and forecast at all ranges in GRAPES not only in the Southern Hemisphere where conventional observations are lacking but also in the Northern Hemisphere where data are rich. It is noted that a relatively simple assimilation and forecast system in which only the conventional and RO observation are assimilated still has analysis and forecast skill even after nine months integration, and the analysis difference between both hemispheres is gradually reduced with height when compared with NCEP (National Centers for Enviromental Prediction) analysis. Finally, as a result of the new onboard payload of the Chinese FengYun-3 (FY-3) satellites, the research status of the RO of FY-3 satellites is also presented.

Using forum-based competitions to improve sustainability and motivation in higher education GNSS learning - Chances and risks

Science.gov (United States)

Mayer, M.

2012-04-01

The learning strategies of students seem often to be economically adapted to framework requirements in order to achieve best possible examination performances, especially. For this reason, teachers often detect surface level learning characteristics (e.g., accepting facts uncritically, isolated fact storage, fact memorisation) within the learning concepts of students. Therefore, knowledge sustainability is often suffering. This is detectable when trying to build on knowledge of earlier lectures or lecture courses. In order to improve the sustainability of geodetic knowledge, case studies were carried out at the Geodetic Institute of the Karlsruhe Institute of Technology (Karlsruhe, Germany) within the lecture course "Introduction into GNSS positioning". The lecture course "Introduction into GNSS positioning" is a compulsory part of the Bachelor study course "Geodesy and Geoinformatics" and also a supplementary module of the Bachelor study course "Geophysics". The lecture course is aiming for transferring basic knowledge and basic principles of Global Navigation Satellite Systems (e.g., GPS). During the winter semesters 2010/11 and 2011/12 ten resp. 15 students visited this compulsory attendance lecture course. In addition to classroom lectures and practical training (e.g., field exercises), a forum-based competition was included and tested using the forum feature of the learning management system ILIAS. According to the Bologna Declaration, a special focus of the innovative competition concept is on competence-related learning. The developed eLearning-related competition concept supports and motivates the students to learn more sustainable. In addition, the students have to be creative and have to deal with GNSS factual knowledge in order to win the competition. Within the presentation, the didactical concept of the enriched blended learning lecture course and the competition-based case study are discussed. The rules of the competition are presented in detail

Assessing ionospheric activity by long time series of GNSS signals: the search of possible connection with seismicity

Science.gov (United States)

Galeandro, Angelo; Mancini, Francesco; De Giglio, Michaela; Barbarella, Maurizio

2014-05-01

The modifications of some atmospheric physical properties prior to a high magnitude earthquake were recently debated in the frame of the Lithosphere-Atmosphere-Ionosphere (LAI) Coupling model. Among this variety of phenomena, the ionization of air at the ionospheric levels due to leaking of gases from earth crust through the analysis of long time series of GNSS (Global Navigation Satellite System) signals was investigated in this work. Several authors used the dispersive properties of the ionospheric strata towards the GNSS signals to detect possible ionospheric anomalies over areas affected by earthquakes and some evidences were encountered. However, the spatial scale and temporal domains over which such disturbances come into evidence is still a controversial item. Furthermore, the correspondence by chance between ionospheric disturbances and relevant seismic activity is even more difficult to model whenever the reference time period and spatial extent of investigation are confined. Problems could also arise from phenomena due to solar activity (now at culmination within the 11 years-long solar cycle) because such global effects could reduce the ability to detect disturbances at regional or local spatial scale. In this work, two case studies were investigated. The first one focuses on the M = 6.3 earthquake occurred on April 6, 2009, close to the city of L'Aquila (Abruzzo, Italy). The second concerns the M = 5.9 earthquake occurred on May 20, 2012, between the cities of Ferrara and Modena (Emilia Romagna, Italy). To investigate possible connections between the ionospheric activity and seismicity for such events, a five-year (2008-2012) long series of high resolution ionospheric maps was used. These maps were produced by authors from GNSS data collected by permanent stations uniformly distributed around the epicenters and allowed to assess the ionospheric activity through the analysis of the TEC (Total Electron Content). To avoid the influence of solar activity

First Study on the Occurrence Frequency of Equatorial Plasma Bubbles over West Africa Using an All-Sky Airglow Imager and GNSS Receivers

Science.gov (United States)

Okoh, Daniel; Rabiu, Babatunde; Shiokawa, Kazuo; Otsuka, Yuichi; Segun, Bolaji; Falayi, Elijah; Onwuneme, Sylvester; Kaka, Rafiat

2017-12-01

This is the first paper that reports the occurrence frequency of equatorial plasma bubbles and their dependences of local time, season, and geomagnetic activity based on airglow imaging observations at West Africa. The all-sky imager, situated in Abuja (Geographic: 8.99°N, 7.38°E; Geomagnetic: 1.60°S), has a 180° fisheye view covering almost the entire airspace of Nigeria. Plasma bubbles are observed for 70 nights of the 147 clear-sky nights from 9 June 2015 to 31 January 2017. Differences between nighttime and daytime ROTIs were also computed as a proxy of plasma bubbles using Global Navigation Satellite Systems (GNSS) receivers within the coverage of the all-sky imager. Most plasma bubble occurrences are found during equinoxes and least occurrences during solstices. The occurrence rate of plasma bubbles was highest around local midnight and lower for hours farther away. Most of the postmidnight plasma bubbles were observed around the months of December to March, a period that coincides with the harmattan period in Nigeria. The on/off status of plasma bubble in airglow and GNSS observations were in agreement for 67.2% of the total 768 h, while we suggest several reasons responsible for the remaining 32.8% when the airglow and GNSS bubble status are inconsistent. A majority of the plasma bubbles were observed under relatively quiet geomagnetic conditions (Dst ≥ -40 and Kp ≤ 3), but there was no significant pattern observed in the occurrence rate of plasma bubbles as a function of geomagnetic activity. We suggest that geomagnetic activities could have either suppressed or promoted the occurrence of plasma bubbles.

JOYO MK-II core characteristics database. Update to JFS-3-J3.2R

International Nuclear Information System (INIS)

Ohkawachi, Yasushi; Maeda, Shigetaka; Sekine, Takashi

2003-04-01

The 'JOYO' MK-II core characteristics database was compiled and published in 1998. Comments and requests from many users led to the creation of a revised edition in 2001. The revisions include changes to the MAGI calculation code system to use the 70 group JFS-3-J3.2 constant set processed from the JENDL-3.2 library. However, after the database was published, it was recently found that there were errors in the process of making the group constant set JFS-3-J3.2, and it was revised at JFS-3-J3.2R. Then, the group constant set was updated at JFS-3-J3.2R in this database. The MK-II core management data nad core characteristics data were recorded on CD-ROM for user convenience. The structure of the database is the same as in the first edition. The 'Configuration Data' include the core arrangement and refueling record for each operational cycle. The 'Subassembly Library Data' include the atomic number density, neutron fluence, burn-up, integral power of 362 driver fuel subassemblies and 69 irradiation test subassemblies. The 'Output Data' contain the calculated neutron flux, gamma flux, power density, linear heat rate, coolant and fuel temperature distribution of all the fuel subassemblies at the beginning and end of each operational cycle. The 'Core Characteristics Data' include the measured excess reactivity, control rod worth calibration curve, and reactivity coefficients of temperature, power and burn-up. The effect of updating the group constant set, the calculation results of excess reactivity decreased by about 0.15Δk/kk', and the effects to other core characteristics were negligible. (author)

Vertical Deformation Monitoring of the Suspension Bridge Tower Using GNSS: A Case Study of the Forth Road Bridge in the UK

Directory of Open Access Journals (Sweden)

Qusen Chen

2018-02-01

Full Text Available The vertical deformation monitoring of a suspension bridge tower is of paramount importance to maintain the operational safety since nearly all forces are eventually transferred as the vertical stress on the tower. This paper analyses the components affecting the vertical deformation and attempts to reveal its deformation mechanism. Firstly, we designed a strategy for high-precision GNSS data processing aiming at facilitating deformation extraction and analysis. Then, 33 months of vertical deformation time series of the southern tower of the Forth Road Bridge (FRB in the UK were processed, and the accurate subsidence and the parameters of seasonal signals were estimated based on a classic function model that has been widely studied to analyse GNSS coordinate time series. We found that the subsidence rate is about 4.7 mm/year, with 0.1 mm uncertainty. Meanwhile, a 15-month meteorological dataset was utilised with a thermal expansion model (TEM to explain the effects of seasonal signals on tower deformation. The amplitude of the annual signals correlated quite well that obtained by the TEM, with the consistency reaching 98.9%, demonstrating that the thermal effect contributes significantly to the annual signals. The amplitude of daily signals displays poor consistency with the ambient temperature data. However, the phase variation tendencies between the daily signals of the vertical deformation and the ambient temperature are highly consistent after February 2016. Finally, the potential contribution of the North Atlantic Drift (NAD to the characteristics of annual and daily signals is discussed because of the special geographical location of the FRB. Meanwhile, this paper emphasizes the importance of collecting more detailed meteorological and other loading data for the investigation of the vertical deformation mechanism of the bridge towers over time with the support of GNSS.

Application of Geostationary GNSS and SBAS Satellites for Studying Ionospheric TEC Disturbances of Geomagnetic and Meteorological Origin

Science.gov (United States)

Padokhin, A. M.; Kurbatov, G. A.; Yasyukevich, Y.; Yasyukevich, A.

2017-12-01

With the development of GNSS and SBAS constellations, the coherent multi-frequency L band transmissions are now available from a number of geostationary satellites. These signals can be used for ionospheric TEC estimations in the same way as widely used GPS/GLONASS signals. In this work, we compare noise patterns in TEC estimations based on different geostationary satellites data: augmentation systems (Indian GAGAN, European EGNOS and American WAAS), and Chinese COMPASS/Beidou navigation system. We show that noise level in geostationary COMPASS/Beidou TEC estimations is times smaller than noise in SBAS TEC estimation and corresponds to those of GPS/GLONASS at the same elevation angles. We discuss the capabilities of geostationary TEC data for studying ionospheric variability driven by space weather and meteorological sources at different time scales. Analyzing data from IGS/MGEX receivers we present geostationary TEC response on X-class Solar flares of current cycle, moderate and strong geomagnetic storms, including G4 St. Patrick's day Storm 2015 and recent G3 storm of the end of May 2017. We also discuss geostationary TEC disturbances in near equatorial ionosphere caused by two SSW events (minor and major final warming of 2015-2016 winter season) as well as geostationary TEC response on typhoons activity near Taiwan in autumn 2016. Our results show large potential of geostationary TEC estimations with GNSS and SBAS signals for continuous ionospheric monitoring.

2D PWV monitoring of a wide and orographically complex area with a low dense GNSS network

Science.gov (United States)

Ferrando, Ilaria; Federici, Bianca; Sguerso, Domenico

2018-04-01

This study presents an innovative procedure to monitor the precipitable water vapor (PWV) content of a wide and orographically complex area with low-density networks. The procedure, termed G4M (global navigation satellite system, GNSS, for Meteorology), has been developed in a geographic information system (GIS) environment using the free and open source GRASS GIS software (https://grass.osgeo.org). The G4M input data are zenith total delay estimates obtained from GNSS permanent stations network adjustment and pressure ( P) and temperature ( T) observations using existing infrastructure networks with different geographic distributions in the study area. In spite of the wide sensor distribution, the procedure produces 2D maps with high spatiotemporal resolution (up to 250 m and 6 min) based on a simplified mathematical model including data interpolation, which was conceived by the authors to describe the atmosphere's physics. In addition to PWV maps, the procedure provides ΔPWV and heterogeneity index maps: the former represents PWV variations with respect to a "calm" moment, which are useful for monitoring the PWV evolution; and the latter are promising indicators to localize severe meteorological events in time and space. This innovative procedure is compared with meteorological simulations in this paper; in addition, an application to a severe event that occurred in Genoa (Italy) is presented.[Figure not available: see fulltext.

Normalized GNSS Interference Pattern Technique for Altimetry

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Miguel Angel Ribot

2014-06-01

Full Text Available It is well known that reflected signals from Global Navigation Satellite Systems (GNSS can be used for altimetry applications, such as monitoring of water levels and determining snow height. Due to the interference of these reflected signals and the motion of satellites in space, the signal-to-noise ratio (SNR measured at the receiver slowly oscillates. The oscillation rate is proportional to the change in the propagation path difference between the direct and reflected signals, which depends on the satellite elevation angle. Assuming a known receiver position, it is possible to compute the distance between the antenna and the surface of reflection from the measured oscillation rate. This technique is usually known as the interference pattern technique (IPT. In this paper, we propose to normalize the measurements in order to derive an alternative model of the SNR variations. From this model, we define a maximum likelihood estimate of the antenna height that reduces the estimation time to a fraction of one period of the SNR variation. We also derive the Cramér–Rao lower bound for the IPT and use it to assess the sensitivity of different parameters to the estimation of the antenna height. Finally, we propose an experimental framework, and we use it to assess our approach with real GPS L1 C/A signals.

Atmospheric QBO and ENSO indices with high vertical resolution from GNSS radio occultation temperature measurements

Science.gov (United States)

Wilhelmsen, Hallgeir; Ladstädter, Florian; Scherllin-Pirscher, Barbara; Steiner, Andrea K.

2018-03-01

We provide atmospheric temperature variability indices for the tropical troposphere and stratosphere based on global navigation satellite system (GNSS) radio occultation (RO) temperature measurements. By exploiting the high vertical resolution and the uniform distribution of the GNSS RO temperature soundings we introduce two approaches, both based on an empirical orthogonal function (EOF) analysis. The first method utilizes the whole vertical and horizontal RO temperature field from 30° S to 30° N and from 2 to 35 km altitude. The resulting indices, the leading principal components, resemble the well-known patterns of the Quasi-Biennial Oscillation (QBO) and the El Niño-Southern Oscillation (ENSO) in the tropics. They provide some information on the vertical structure; however, they are not vertically resolved. The second method applies the EOF analysis on each altitude level separately and the resulting indices contain information on the horizontal variability at each densely available altitude level. They capture more variability than the indices from the first method and present a mixture of all variability modes contributing at the respective altitude level, including the QBO and ENSO. Compared to commonly used variability indices from QBO winds or ENSO sea surface temperature, these new indices cover the vertical details of the atmospheric variability. Using them as proxies for temperature variability is also of advantage because there is no further need to account for response time lags. Atmospheric variability indices as novel products from RO are expected to be of great benefit for studies on atmospheric dynamics and variability, for climate trend analysis, as well as for climate model evaluation.

Angiotensin II type 1a receptor-deficient mice develop angiotensin II-induced oxidative stress and DNA damage without blood pressure increase.

Science.gov (United States)

Zimnol, Anna; Amann, Kerstin; Mandel, Philipp; Hartmann, Christina; Schupp, Nicole

2017-12-01

Hypertensive patients have an increased risk of developing kidney cancer. We have shown in vivo that besides elevating blood pressure, angiotensin II causes DNA damage dose dependently. Here, the role of blood pressure in the formation of DNA damage is studied. Mice lacking one of the two murine angiotensin II type 1 receptor (AT1R) subtypes, AT1aR, were equipped with osmotic minipumps, delivering angiotensin II during 28 days. Parameters of oxidative stress and DNA damage of kidneys and hearts of AT1aR-knockout mice were compared with wild-type (C57BL/6) mice receiving angiotensin II, and additionally, with wild-type mice treated with candesartan, an antagonist of both AT1R subtypes. In wild-type mice, angiotensin II induced hypertension, reduced kidney function, and led to a significant formation of reactive oxygen species (ROS). Furthermore, genomic damage was markedly increased in this group. All these responses to angiotensin II could be attenuated by concurrent administration of candesartan. In AT1aR-deficient mice treated with angiotensin II, systolic pressure was not increased, and renal function was not affected. However, angiotensin II still led to an increase of ROS in kidneys and hearts of these animals. Additionally, genomic damage in the form of double-strand breaks was significantly induced in kidneys of AT1aR-deficient mice. Our results show that angiotensin II induced ROS production and DNA damage even without the presence of AT1aR and independently of blood pressure changes. Copyright © 2017 the American Physiological Society.

Filmiinimesed sõjaretkel, Aadu Krevald ja metsikud räpparid : Valitud palu dokumentaalfilmide sarjast "Eesti lood" II / Olev Remsu

Index Scriptorium Estoniae

Remsu, Olev, 1947-

2009-01-01

ETVs näidatud dokumentaalfilmidest sarjas "Eesti lood II" - Mart Arjukese film Ilmar Raagi osalemisest Erna retkel "Sõjamäng" (esilinastus kinos Sõprus 9. XI 2008), Igor Kurve film sporditeadlasest Aadu Krevaldist "Teaduspõhine toode" (eetris 14. I 2009), Mihkel Ulgi film räpparitest "MC Battle - sõnasõjad" (eetris 8. X 2008)

Estimation of small surface displacements in the Upper Rhine Graben area from a combined analysis of PS-InSAR, levelling and GNSS data

NARCIS (Netherlands)

Fuhrmann, T.; Caro Cuenca, M.; Knöpfler, A.; Leijen, F.J. van; Mayer, M.; Westerhaus, M.; Hanssen, R.F.; Heck, B.

2015-01-01

The intra-plate deformation of the Upper Rhine Graben (URG) located in Central Europe is investigated using geodetic measurement techniques. We present a new approach to calculate a combined velocity field from InSAR, levelling and GNSS measurements. As the expected tectonic movements in the URG

IGF-II Promotes Stemness of Neural Restricted Precursors

Science.gov (United States)

Ziegler, Amber N.; Schneider, Joel S.; Qin, Mei; Tyler, William A.; Pintar, John E.; Fraidenraich, Diego; Wood, Teresa L.; Levison, Steven W.

2016-01-01

Insulin-like growth factor (IGF)-I and IGF-II regulate brain development and growth through the IGF type 1 receptor (IGF-1R). Less appreciated is that IGF-II, but not IGF-I, activates a splice variant of the insulin receptor (IR) known as IR-A. We hypothesized that IGF-II exerts distinct effects from IGF-I on neural stem/progenitor cells (NSPs) via its interaction with IR-A. Immunofluorescence revealed high IGF-II in the medial region of the subventricular zone (SVZ) comprising the neural stem cell niche, with IGF-II mRNA predominant in the adjacent choroid plexus. The IGF-1R and the IR isoforms were differentially expressed with IR-A predominant in the medial SVZ, whereas the IGF-1R was more abundant laterally. Similarly, IR-A was more highly expressed by NSPs, whereas the IGF-1R was more highly expressed by lineage restricted cells. In vitro, IGF-II was more potent in promoting NSP expansion than either IGF-I or standard growth medium. Limiting dilution and differentiation assays revealed that IGF-II was superior to IGF-I in promoting stemness. In vivo, NSPs propagated in IGF-II migrated to and took up residence in periventricular niches while IGF-I-treated NSPs predominantly colonized white matter. Knockdown of IR or IGF-1R using shRNAs supported the conclusion that the IGF-1R promotes progenitor proliferation, whereas the IR is important for self-renewal. Q-PCR revealed that IGF-II increased Oct4, Sox1, and FABP7 mRNA levels in NSPs. Our data support the conclusion that IGF-II promotes the self-renewal of neural stem/progenitors via the IR. By contrast, IGF-1R functions as a mitogenic receptor to increase precursor abundance. PMID:22593020

Biosorption of Cu(II) onto agricultural materials from tropical regions

KAUST Repository

Acheampong, Mike A.; Pereira, Joana P.C.; Meulepas, Roel J.W.; Lens, Piet N.L.

2011-01-01

model described the Cu(II) removal by coconut husk (R2 = 0.999) and sawdust (R2 = 0.993) very well and the Cu(II) removal by Moringa oleifera seeds (R2 = 0.960) well. The model only reasonably described the Cu(II) removal by coconut shell (R2 = 0.932). A

Preparation, infrared, raman and nmr spectra of N,N'-diethylthiourea complexes with zinc(II), cadmium(II) and mercury(II) halides

Energy Technology Data Exchange (ETDEWEB)

Marcotrigiano, G [Bari Univ. (Italy). Cattedra di Chimica, Facolta di Medicina-Veterinaria

1976-05-01

Several complexes of N,N'-diethylthiourea (Dietu) with zinc(II), cadmium(II) and mercury(II) halides were prepared and characterized by i.r. (4000-60 cm/sup -1/), raman (400-60 cm/sup -1/), in the solid state and n.m.r. and conductometric methods in solution. The complexes Zn(Dietu)/sub 2/X/sub 2/, Cd(Dietu)/sub 2/X/sub 2/ (X=Cl, Br, I) and Hg(Dietu)/sub 2/X/sub 2/ (X=Br, I) are tetrahedral species in which intramolecular -NH...X interactions have been observed. The 1:1 mercury(II) complexes, Hg(Dietu)X/sub 2/ (X=Cl, Br), appear to have a dimeric tetrahedral halide-bridged structure in the solid state. In all these complexes N,N'-diethylthiourea is sulphur-bonded to the metal.

Mathematical modelling of ionospheric TEC from Turkish permanent GNSS Network (TPGN) observables during 2009-2017 and predictability of NeQuick and Kriging models

Science.gov (United States)

Ansari, Kutubuddin; Panda, Sampad Kumar; Corumluoglu, Ozsen

2018-03-01

The present study examines the ionospheric Total Electron Content (TEC) variations in the lower mid-latitude Turkish region from the Turkish permanent GNSS network (TPGN) and International GNSS Services (IGS) observations during the years 2009 to 2017. The corresponding vertical TEC (VTEC) predicted by Kriging and NeQuick-2 models are evaluated to realize their efficacy over the country. We studied the diurnal, seasonal and spatial pattern of VTEC variation and tried to estimate by a new mathematical model using the long term of 9 years VTEC data. The diurnal variation of VTEC demonstrates a normal trend with its gradual enhancement from dawn to attain a peak around 09:00-14.00 UT and reaching the minimum level after 22.00 UT. The seasonal behavior of VTEC indicates a strong semi-annual variation of VTEC with maxima in September equinox followed by March equinox and minima in June solstice followed by December solstice. Also, the spatial variation in VTEC depicts a meaningful longitudinal/latitudinal pattern altering with seasons. It decreases longitudinally from the west to the east during March equinox and June solstice increases with latitude. The comparative analysis among the GNSS-VTEC, Kriging, NeQuick and the proposed mathematical model are evaluated with the help one way ANOVA test. The analysis shows that the null hypothesis of the models during storm and quiet days are accepted and suggesting that all models are statistically significantly equivalent from each other. We believe the outcomes from this study would complement towards a relatively better understanding of the lower mid-latitude VTEC variation over the Turkish region and analogous latitudes over the globe.

R Jayaraman

Indian Academy of Sciences (India)

More Details Fulltext PDF. Volume 13 Issue 10 October 2008 pp 898-908 General Article. Seymour Benzer and T4 rII - Running the Map into the Ground · R Jayaraman · More Details Fulltext PDF. Volume 15 Issue 12 December 2010 pp 1084-1096 General Article. Jacques Monod and the Advent of the Age of Operons.

The review and development of a modern GNSS network and datum in Uzbekistan

Directory of Open Access Journals (Sweden)

Dilbarkhon Fazilova

2017-05-01

Full Text Available This study is focused on the discussion of a modern GNSS network and datum in Uzbekistan. Considering the significance difference (up to 200 m in positions of the local ellipsoidal datum and the global datum, the precise transformation parameters between national geodetic datum CS-42, and the World Geodetic System 1984 (WGS84 global datum used by the GPS is estimated. This study aims to evaluate the accuracy of the currently used transformation parameters from different sources in the region, and give preliminary recommendations for using these sets also. The differences between transformed, original and WGS-84 coordinates were calculated and evaluated. On the basis of this difference, different zones for determination of transformation parameters have been proposed.

Safety Case as a Necessary Aspect of the Aviation Implementation of the Gnss / Safety Case Jako Niezbędny Aspekt Lotniczej Implementacji Systemu Gnss

Directory of Open Access Journals (Sweden)

Fellner Andrzej

2014-12-01

Full Text Available Artykuł przedstawia analizę ryzyka na potrzeby wdrożenia procedur podejścia precyzyjnego (Localizer Performance and Vertical Guidance - LPV z użyciem sensora GNSS dla lotnisk w Warszawie i Katowicach. Szczegóły zostały zawarte w opracowywanym w ramach międzynarodowego projektu SHERPA. Do analizy wykorzystano techniki identyfikacji zagrożeń (zderzenie z powierzchnią ziemi w locie sterowanym - CFIT, wypadek podczas lądowania - LA, kolizja w powietrzu - MAC, procedura po nieudanym podejściu - MA, bezpieczne lądowanie i oceny ich następstw oparte o metody analiz: Event Tree Analysis, zestawienie prawdopodobieństwa ryzyka bezpieczeństwa, macierz oceny ryzyka bezpieczeństwa oraz Functional Hazard Assesment. Następnie określono cele bezpieczeństwa. Przeprowadzone badania pozwoliły na wyznaczenie prawdopodobieństw występowania zagrożeń i celów bezpieczeństwa, a także porównanie ich względem wymagań systemu ILS

Application of thin plate splines for accurate regional ionosphere modeling with multi-GNSS data

Science.gov (United States)

Krypiak-Gregorczyk, Anna; Wielgosz, Pawel; Borkowski, Andrzej

2016-04-01

GNSS-derived regional ionosphere models are widely used in both precise positioning, ionosphere and space weather studies. However, their accuracy is often not sufficient to support precise positioning, RTK in particular. In this paper, we presented new approach that uses solely carrier phase multi-GNSS observables and thin plate splines (TPS) for accurate ionospheric TEC modeling. TPS is a closed solution of a variational problem minimizing both the sum of squared second derivatives of a smoothing function and the deviation between data points and this function. This approach is used in UWM-rt1 regional ionosphere model developed at UWM in Olsztyn. The model allows for providing ionospheric TEC maps with high spatial and temporal resolutions - 0.2x0.2 degrees and 2.5 minutes, respectively. For TEC estimation, EPN and EUPOS reference station data is used. The maps are available with delay of 15-60 minutes. In this paper we compare the performance of UWM-rt1 model with IGS global and CODE regional ionosphere maps during ionospheric storm that took place on March 17th, 2015. During this storm, the TEC level over Europe doubled comparing to earlier quiet days. The performance of the UWM-rt1 model was validated by (a) comparison to reference double-differenced ionospheric corrections over selected baselines, and (b) analysis of post-fit residuals to calibrated carrier phase geometry-free observational arcs at selected test stations. The results show a very good performance of UWM-rt1 model. The obtained post-fit residuals in case of UWM maps are lower by one order of magnitude comparing to IGS maps. The accuracy of UWM-rt1 -derived TEC maps is estimated at 0.5 TECU. This may be directly translated to the user positioning domain.

Cálculo, mediante la aplicación del algoritmo de ajuste por mínimos cuadrados, de los componentes de velocidad para estaciones GNSS continuas

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Jorge Moya Zamora

2014-07-01

Full Text Available El cálculo de la velocidad de una estación de observación continua GNSS representa un insumo fundamental en la geodesia moderna. El hecho de determinar la posición de las estaciones GNSS de forma diaria implica que se puedan establecer las series temporales de las estaciones, con base en las cuales se puede obtener información de la influencia de fenómenos que afecten el comportamiento de estas. En este artículo se plantea una descripción del algoritmo de ajuste por mínimos cuadrados adaptado y aplicado a la determinación de los componentes de velocidad de estaciones de observación continua. Además, se aplica este algoritmo para la calcular la velocidad de la estación ETCG, perteneciente al Sistema Geocéntrico para las Américas (SIRGAS.

Augmented GNSS Differential Corrections Minimum Mean Square Error Estimation Sensitivity to Spatial Correlation Modeling Errors

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Nazelie Kassabian

2014-06-01

Full Text Available Railway signaling is a safety system that has evolved over the last couple of centuries towards autonomous functionality. Recently, great effort is being devoted in this field, towards the use and exploitation of Global Navigation Satellite System (GNSS signals and GNSS augmentation systems in view of lower railway track equipments and maintenance costs, that is a priority to sustain the investments for modernizing the local and regional lines most of which lack automatic train protection systems and are still manually operated. The objective of this paper is to assess the sensitivity of the Linear Minimum Mean Square Error (LMMSE algorithm to modeling errors in the spatial correlation function that characterizes true pseudorange Differential Corrections (DCs. This study is inspired by the railway application; however, it applies to all transportation systems, including the road sector, that need to be complemented by an augmentation system in order to deliver accurate and reliable positioning with integrity specifications. A vector of noisy pseudorange DC measurements are simulated, assuming a Gauss-Markov model with a decay rate parameter inversely proportional to the correlation distance that exists between two points of a certain environment. The LMMSE algorithm is applied on this vector to estimate the true DC, and the estimation error is compared to the noise added during simulation. The results show that for large enough correlation distance to Reference Stations (RSs distance separation ratio values, the LMMSE brings considerable advantage in terms of estimation error accuracy and precision. Conversely, the LMMSE algorithm may deteriorate the quality of the DC measurements whenever the ratio falls below a certain threshold.

Development and testing of a new ray-tracing approach to GNSS carrier-phase multipath modelling

Science.gov (United States)

Lau, Lawrence; Cross, Paul

2007-11-01

Multipath is one of the most important error sources in Global Navigation Satellite System (GNSS) carrier-phase-based precise relative positioning. Its theoretical maximum is a quarter of the carrier wavelength (about 4.8 cm for the Global Positioning System (GPS) L1 carrier) and, although it rarely reaches this size, it must clearly be mitigated if millimetre-accuracy positioning is to be achieved. In most static applications, this may be accomplished by averaging over a sufficiently long period of observation, but in kinematic applications, a modelling approach must be used. This paper is concerned with one such approach: the use of ray-tracing to reconstruct the error and therefore remove it. In order to apply such an approach, it is necessary to have a detailed understanding of the signal transmitted from the satellite, the reflection process, the antenna characteristics and the way that the reflected and direct signal are processed within the receiver. This paper reviews all of these and introduces a formal ray-tracing method for multipath estimation based on precise knowledge of the satellite reflector antenna geometry and of the reflector material and antenna characteristics. It is validated experimentally using GPS signals reflected from metal, water and a brick building, and is shown to be able to model most of the main multipath characteristics. The method will have important practical applications for correcting for multipath in well-constrained environments (such as at base stations for local area GPS networks, at International GNSS Service (IGS) reference stations, and on spacecraft), and it can be used to simulate realistic multipath errors for various performance analyses in high-precision positioning.

New Applications for Detecting Natural Hazards Using Ground and Space-Based GNSS-Derived Ionospheric Measurements

Science.gov (United States)

Komjathy, A.; Butala, M.; Verkhoglyadova, O. P.; Wilson, B. D.; Iijima, B.; Akopian, V.; Mannucci, A.

2012-12-01

The NASA Jet Propulsion Laboratory (JPL) and University of Southern California (USC) have jointly developed the Global Assimilative Ionospheric Model (GAIM) to monitor space weather, study storm effects, and provide ionospheric calibration for various customers including NASA flight projects. JPL/USC GAIM is a physics-based 3D data assimilation model using 4DVAR and Kalman filter approaches to solve for ion and electron density states and other key ionospheric drivers. The JPL/USC GAIM technologies, now operating in real-time and post-processing modes, can routinely accept as input ground GPS TEC data from 1200+ sites including streaming and hourly GPS stations, occultation links from CHAMP, SAC-C, COSMIC and C/NOFS satellites, UV limb and nadir scans. In the presentation, first we will discuss recent advances in our assimilating ground-based GPS, C/NOFS and COSMIC occultation measurements using our GAIM system characterizing the ionosphere in 3D. We will elaborate on our improved space-based bias estimation techniques to generate high precision calibrated TEC measurements to be assimilated into GAIM. We will discuss the benefits of adding GLONASS measurements to our GIM and GAIM processing technologies. New and upcoming applications and first results will be shown for estimating very high precision TEC perturbations using real-time and post-processed GNSS observations from GEONET and IGS networks. We will demonstrate initial steps on how to integrate this GNSS ionosphere-based technology into a global tsunami warning system. Additional potential applications might include the remote sensing of ionospheric TEC perturbations generated by other natural hazards such as earthquakes and volcanic eruptions and human-made events such as nuclear tests.

Amplification of marine methanotrophic enrichment DNA with 16S rDNA PCR primers for type II alpha proteobacteria methanotrophs.

Science.gov (United States)

Rockne, Karl J; Strand, Stuart E

2003-09-01

Type II alpha proteobacteria methanotrophs are capable of a wide range of cometabolic transformations of chlorinated solvents and polycyclic aromatic hydrocarbons (PAHs), and this activity has been exploited in many terrestrial bioremediation systems. However, at present, all known obligately marine methanotrophic isolates are Type I gamma proteobacteria which do not have this activity to the extent of Type II methanotrophs. In previous work in our laboratory, determining the presence of Type II alpha proteobacteria methanotrophs in marine enrichment cultures that co-metabolized PAHs required a more sensitive assay. 16S rDNA PCR primers were designed based on oligonucleotide probes for serine pathway methanotrophs and serine pathway methylotrophs with an approximate amplification fragment size of 870 base pairs. Comparison of the primers using double primer BLAST searches in established nucleotide databases showed potential amplification with all Methylocystis and Methylosinus spp., as well as potential amplification with Methylocella palustrus. DNA from Methylosinus trichosporium OB3b, a Type II methanotroph, amplified with the primers with a fragment size of approximately 850 base pairs, whereas DNA extracted from Methylomonas methanica, a Type I methanotroph, did not. The primers were used to amplify DNA extracted from two marine methanotrophic enrichment cultures: a low nitrogen/low copper enrichment to select for Type II methanotrophs and a high nitrogen/high copper enrichment to select for Type I methanotrophs. Although DNA from both cultures amplified with the PCR primers, amplification was stronger in cultures that were specifically enriched for Type II methanotrophs, suggesting the presence of higher numbers of Type II methanotrophs. These results provide further evidence for the existence of Type II marine methanotrophs, suggesting the possibility of exploiting cometabolic activity in marine systems.

Are estimates of wind characteristics based on measurements with Pitot tubes and GNSS receivers mounted on consumer-grade unmanned aerial vehicles applicable in meteorological studies?

Science.gov (United States)

Niedzielski, Tomasz; Skjøth, Carsten; Werner, Małgorzata; Spallek, Waldemar; Witek, Matylda; Sawiński, Tymoteusz; Drzeniecka-Osiadacz, Anetta; Korzystka-Muskała, Magdalena; Muskała, Piotr; Modzel, Piotr; Guzikowski, Jakub; Kryza, Maciej

2017-09-01

The objective of this paper is to empirically show that estimates of wind speed and wind direction based on measurements carried out using the Pitot tubes and GNSS receivers, mounted on consumer-grade unmanned aerial vehicles (UAVs), may accurately approximate true wind parameters. The motivation for the study is that a growing number of commercial and scientific UAV operations may soon become a new source of data on wind speed and wind direction, with unprecedented spatial and temporal resolution. The feasibility study was carried out within an isolated mountain meadow of Polana Izerska located in the Izera Mountains (SW Poland) during an experiment which aimed to compare wind characteristics measured by several instruments: three UAVs (swinglet CAM, eBee, Maja) equipped with the Pitot tubes and GNSS receivers, wind speed and direction meters mounted at 2.5 and 10 m (mast), conventional weather station and vertical sodar. The three UAVs performed seven missions along spiral-like trajectories, most reaching 130 m above take-off location. The estimates of wind speed and wind direction were found to agree between UAVs. The time series of wind speed measured at 10 m were extrapolated to flight altitudes recorded at a given time so that a comparison was made feasible. It was found that the wind speed estimates provided by the UAVs on a basis of the Pitot tube/GNSS data are in agreement with measurements carried out using dedicated meteorological instruments. The discrepancies were recorded in the first and last phases of UAV flights.

Adjustments of the TaD electron density reconstruction model with GNSS-TEC parameters for operational application purposes

Directory of Open Access Journals (Sweden)

Belehaki Anna

2012-12-01

Full Text Available Validation results on the latest version of TaD model (TaDv2 show realistic reconstruction of the electron density profiles (EDPs with an average error of 3 TECU, similar to the error obtained from GNSS-TEC calculated paremeters. The work presented here has the aim to further improve the accuracy of the TaD topside reconstruction, adjusting the TEC parameter calculated from TaD model with the TEC parameter calculated by GNSS transmitting RINEX files provided by receivers co-located with the Digisondes. The performance of the new version is tested during a storm period demonstrating further improvements in respect to the previous version. Statistical comparison of modeled and observed TEC confirms the validity of the proposed adjustment. A significant benefit of the proposed upgrade is that it facilitates the real-time implementation of TaD. The model needs a reliable measure of the scale height at the peak height, which is supposed to be provided by Digisondes. Oftenly, the automatic scaling software fails to correctly calculate the scale height at the peak, Hm, due to interferences in the receiving signal. Consequently the model estimated topside scale height is wrongly calculated leading to unrealistic results for the modeled EDP. The proposed TEC adjustment forces the model to correctly reproduce the topside scale height, despite the inaccurate values of Hm. This adjustment is very important for the application of TaD in an operational environment.

Baseline configuration for GNSS attitude determination with an analytical least-squares solution

International Nuclear Information System (INIS)

Chang, Guobin; Wang, Qianxin; Xu, Tianhe

2016-01-01

The GNSS attitude determination using carrier phase measurements with 4 antennas is studied on condition that the integer ambiguities have been resolved. The solution to the nonlinear least-squares is often obtained iteratively, however an analytical solution can exist for specific baseline configurations. The main aim of this work is to design this class of configurations. Both single and double difference measurements are treated which refer to the dedicated and non-dedicated receivers respectively. More realistic error models are employed in which the correlations between different measurements are given full consideration. The desired configurations are worked out. The configurations are rotation and scale equivariant and can be applied to both the dedicated and non-dedicated receivers. For these configurations, the analytical and optimal solution for the attitude is also given together with its error variance–covariance matrix. (paper)

VLBI TRF Combination Using GNSS Software

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Younghee Kwak

2013-12-01

Full Text Available Space geodetic techniques can be used to obtain precise shape and rotation information of the Earth. To achieve this, the representative combination solution of each space geodetic technique has to be produced, and then those solutions need to be combined. In this study, the representative combination solution of very long baseline interferometry (VLBI, which is one of the space geodetic techniques, was produced, and the variations in the position coordinate of each station during 7 years were analyzed. Products from five analysis centers of the International VLBI Service for Geodesy and Astrometry (IVS were used as the input data, and Bernese 5.0, which is the global navigation satellite system (GNSS data processing software, was used. The analysis of the coordinate time series for the 43 VLBI stations indicated that the latitude component error was about 15.6 mm, the longitude component error was about 37.7 mm, and the height component error was about 30.9 mm, with respect to the reference frame, International Terrestrial Reference Frame 2008 (ITRF2008. The velocity vector of the 42 stations excluding the YEBES station showed a magnitude difference of 7.3 mm/yr (30.2% and a direction difference of 13.8° (3.8%, with respect to ITRF2008. Among these, the 10 stations in Europe showed a magnitude difference of 7.8 mm/yr (30.3% and a direction difference of 3.7° (1.0%, while the 14 stations in North America showed a magnitude difference of 2.7 mm/yr (15.8% and a direction difference of 10.3° (2.9%.

Transport and biotransformation of the new cytostatic complex cis-diammineplatinum(II)-chlorocholylglycinate (Bamet-R2) by the rat liver.

Science.gov (United States)

Macias, R I; Monte, M J; El-Mir, M Y; Villanueva, G R; Marin, J J

1998-09-01

Rat liver uptake and bile output of the cytostatic complex cis-diammineplatinum(II)-chlorocholylglycinate (Bamet-R2) were studied. Up to 100 microM, Bamet-R2 uptake by rat hepatocytes in primary culture followed saturation kinetics (Vmax = 0.65 +/- 0.12 nmol/5 min per mg protein; K(M) = 45.2 +/- 10.7 microM). Bamet-R2 uptake was lower than that of cholylglycinate (CG) but higher than that of cisplatin. Replacement of 116 mM NaCl by 116 mM choline chloride did not significantly reduce Bamet-R2 uptake. Addition of 500 microM CG, cholic acid, estrone sulfate, or ouabain to 50 microM Bamet-R2-containing incubation media inhibited Bamet-R2 uptake. No liver biotransformation of Bamet-R2 occurred, as indicated by HPLC analysis of bile collected from anesthetized rats after intravenous administration of the drug. Bamet-R2 uptake and secretion into bile by isolated rat livers exceeded those of cisplatin but were lower than those of CG. Differences between Bamet-R2 and CG were more marked for bile output than for liver uptake. Thus, higher Bamet-R2 than CG or cisplatin liver content was found. Co-administration of Bamet-R2 and CG revealed that CG induced a slight reduction in Bamet-R2 uptake and a marked inhibition in Bamet-R2 bile output. By contrast, Bamet-R2 had no effect on CG on either liver uptake or bile output. In sum, the present data indicate that Bamet-R2 is efficiently taken up and secreted into bile by the rat liver by mechanisms shared in part by natural bile acids.

Evaluation of extreme ionospheric total electron content gradient associated with plasma bubbles for GNSS Ground-Based Augmentation System

Science.gov (United States)

Saito, S.; Yoshihara, T.

2017-08-01

Associated with plasma bubbles, extreme spatial gradients in ionospheric total electron content (TEC) were observed on 8 April 2008 at Ishigaki (24.3°N, 124.2°E, +19.6° magnetic latitude), Japan. The largest gradient was 3.38 TECU km-1 (total electron content unit, 1 TECU = 1016 el m-2), which is equivalent to an ionospheric delay gradient of 540 mm km-1 at the GPS L1 frequency (1.57542 GHz). This value is confirmed by using multiple estimating methods. The observed value exceeds the maximum ionospheric gradient that has ever been observed (412 mm km-1 or 2.59 TECU km-1) to be associated with a severe magnetic storm. It also exceeds the assumed maximum value (500 mm km-1 or 3.08 TECU km-1) which was used to validate the draft international standard for Global Navigation Satellite System (GNSS) Ground-Based Augmentation Systems (GBAS) to support Category II/III approaches and landings. The steepest part of this extreme gradient had a scale size of 5.3 km, and the front-normal velocities were estimated to be 71 m s-1 with a wavefront-normal direction of east-northeastward. The total width of the transition region from outside to inside the plasma bubble was estimated to be 35.3 km. The gradient of relatively small spatial scale size may fall between an aircraft and a GBAS ground subsystem and may be undetectable by both aircraft and ground.

MiR-608, pre-miR-124-1 and pre-miR26a-1 polymorphisms modify susceptibility and recurrence-free survival in surgically resected CRC individuals.

Science.gov (United States)

Ying, Hou-Qun; Peng, Hong-Xin; He, Bang-Shun; Pan, Yu-Qin; Wang, Feng; Sun, Hui-Ling; Liu, Xian; Chen, Jie; Lin, Kang; Wang, Shu-Kui

2016-11-15

Genetic variation within microRNA (miRNA) may result in its abnormal folding or aberrant expression, contributing to colorectal turmorigenesis and metastasis. However, the association of six polymorphisms (miR-608 rs4919510, miR-499a rs3746444, miR-146a rs2910164, pre-miR-143 rs41291957, pre-miR-124-1 rs531564 and pre-miR-26a-1 rs7372209) with colorectal cancer (CRC) risk, therapeutic response and survival remains unclear. A retrospective study was carried out to investigate the association in 1358 0-III stage resected CRC patients and 1079 healthy controls using Sequenom's MassARRAY platform. The results showed that rs4919510 was significantly associated with a decreased susceptibility to CRC in co-dominant, allele and recessive genetic models, and the protective role of rs4919510 allele G and genotype GG was more pronounced among stage 0-II cases; significant association between rs531564 and poor RFS was observed in cases undergoing adjuvant chemo-radiotherapy in co-dominant, allele and dominant models; moreover, there was a positive association between rs7372209 and recurrence-free survival in stage II cases in co-dominant and over-dominant models; additionally, a cumulative effect of rs531564 and rs7372209 at-risk genotypes with hazard ratio at 1.30 and 1.95 for one and two at-risk genotypes was examined in stage II cases, respectively. Our findings indicated that rs4919510 allele G and genotype GG were protective factors for 0-II stage CRC, rs7372209 and rs531564 could decrease RFS in II stage individuals and resected CRC patients receiving adjuvant chemo-radiology.

Chiral analysis of alpha-diimine Ru(II) and Fe(II) complexes by capillary electrophoresis using sulfated cyclodextrins as stereoselectors

Czech Academy of Sciences Publication Activity Database

Sázelová, Petra; Koval, Dušan; Severa, Lukáš; Teplý, Filip; Kašička, Václav

2017-01-01

Roč. 38, č. 15 (2017), s. 1913-1921 ISSN 0173-0835 R&D Projects: GA ČR(CZ) GA15-01948S; GA ČR GA13-32974S; GA ČR GA13-19213S Institutional support: RVO:61388963 Keywords : binding constant * capillary electrophoresis * chiral separation * polypyridyl Fe(II) complex * polypyridyl Ru(II) complex Subject RIV: CB - Analytical Chemistry, Separation OBOR OECD: Analytical chemistry Impact factor: 2.744, year: 2016

The PEP-II Asymmetric B Factory: Design details and R ampersand D results

International Nuclear Information System (INIS)

Bloom, E.; DeStaebler, H.; Dorfan, J.

1994-06-01

PEP-II, a 9 GeV x 3.1 GeV electron-positron collider with a design luminosity of 3 x 10 33 cm -2 s -1 has now been approved for construction by SLAC, LBL and LLNL for the purpose of studying CP violation in the B bar B system. This upgrade project involves replacing the vacuum and RF systeum of PEP, which will serve as the high-energy ring (HER), along with the addition of a new low-energy ring (LER) mounted atop the HER. Designs for both rings are described, and the anticipated project construction schedule is indicated. Collider operation will begin at the end of 1998. An aggressive R ampersand D program has been carried out to validate our design choices; key results in the areas of lattice design, vacuum, RF, and multibunch feedback are summarized

A NEW RADIO RECOMBINATION LINE MASER OBJECT TOWARD THE MonR2 H II REGION

Energy Technology Data Exchange (ETDEWEB)

Jimenez-Serra, I.; Zhang, Q.; Dierickx, M.; Patel, N. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Baez-Rubio, A.; Rivilla, V. M.; Martin-Pintado, J., E-mail: ijimenez-serra@cfa.harvard.edu, E-mail: qzhang@cfa.harvard.edu, E-mail: mdierickx@cfa.harvard.edu, E-mail: npatel@cfa.harvard.edu, E-mail: ryvendel@gmail.com, E-mail: jmartin@cab.inta-csic.es, E-mail: baezra@cab.inta-csic.es [Centro de Astrobiologia (CSIC/INTA), Ctra. de Torrejon a Ajalvir km 4, E-28850 Torrejon de Ardoz, Madrid (Spain)

2013-02-10

We report the detection of a new radio recombination line (RRL) maser object toward the IRS2 source in the MonR2 ultracompact H II region. The continuum emission at 1.3 mm and 0.85 mm and the H30{alpha} and H26{alpha} lines were observed with the Submillimeter Array (SMA) at angular resolutions of {approx}0.''5-3''. The SMA observations show that the MonR2-IRS2 source is very compact and remains unresolved at spatial scales {<=}400 AU. Its continuum power spectrum at millimeter wavelengths is almost flat ({alpha} = -0.16, with S{sub {nu}}{proportional_to}{nu}{sup {alpha}}), indicating that this source is dominated by optically thin free-free emission. The H30{alpha} and H26{alpha} RRL emission is also compact and peaks toward the position of the MonR2-IRS2 source. The measured RRL profiles are double peaked with the H26{alpha} line showing a clear asymmetry in its spectrum. Since the derived line-to-continuum flux ratios ({approx}80 and 180 km s{sup -1} for H30{alpha} and H26{alpha}, respectively) exceed the LTE predictions, the RRLs toward MonR2-IRS2 are affected by maser amplification. The amplification factors are, however, smaller than those found toward the emission-line star MWC349A, indicating that MonR2-IRS2 is a weakly amplified maser. Radiative transfer modeling of the RRL emission toward this source shows that the RRL masers arise from a dense and collimated jet embedded in a cylindrical ionized wind, oriented nearly along the direction of the line of sight. High-angular resolution observations at submillimeter wavelengths are needed to unveil weakly amplified RRL masers in very young massive stars.