WorldWideScience

Sample records for satellite based fog

  1. A Satellite Based Fog Study of the Korean Peninsula

    Science.gov (United States)

    2007-06-01

    total number of fog and fog likely days detected from the two MODIS satellites, Aqua and Tera , respectively. Results from all nine areas of...trends in fog detection based on the satellite differences. 46 0 20 40 60 80 100 120 N um be r o f D ay s 1 2 3 4 5 6 7 8 9 Areas Four Month Tera vs...Aqua Fog Totals Tera Fog Tera Fog Likely Aqua Fog Aqua Fog Likely Figure 29. Comparisons of the four month total number of fog and fog likely days

  2. An automated fog monitoring system for the Indo-Gangetic Plains based on satellite measurements

    Science.gov (United States)

    Patil, Dinesh; Chourey, Reema; Rizvi, Sarwar; Singh, Manoj; Gautam, Ritesh

    2016-05-01

    Fog is a meteorological phenomenon that causes reduction in regional visibility and affects air quality, thus leading to various societal and economic implications, especially disrupting air and rail transportation. The persistent and widespread winter fog impacts the entire the Indo-Gangetic Plains (IGP), as frequently observed in satellite imagery. The IGP is a densely populated region in south Asia, inhabiting about 1/6th of the world's population, with a strong upward pollution trend. In this study, we have used multi-spectral radiances and aerosol/cloud retrievals from Terra/Aqua MODIS data for developing an automated web-based fog monitoring system over the IGP. Using our previous and existing methodologies, and ongoing algorithm development for the detection of fog and retrieval of associated microphysical properties (e.g. fog droplet effective radius), we characterize the widespread fog detection during both daytime and nighttime. Specifically, for the night time fog detection, the algorithm employs a satellite-based bi-spectral brightness temperature difference technique between two spectral channels: MODIS band-22 (3.9μm) and band-31 (10.75μm). Further, we are extending our algorithm development to geostationary satellites, for providing continuous monitoring of the spatial-temporal variation of fog. We anticipate that the ongoing and future development of a fog monitoring system would be of assistance to air, rail and vehicular transportation management, as well as for dissemination of fog information to government agencies and general public. The outputs of fog detection algorithm and related aerosol/cloud parameters are operationally disseminated via http://fogsouthasia.com/.

  3. Satellite-based multi-spectral detection of the Widespread and Persistent Winter Fog over the Indo-Gangetic Plains

    Science.gov (United States)

    Gautam, R.; Rizvi, S.

    2015-12-01

    The Indo-Gangetic Plains (IGP), in the northern parts of south Asia, are subjected to dense haze/fog during winter months, on an annual basis. The thick fog prevalent during December/January months is both persistent and widespread in nature, often covering the entire IGP which stretches over 1500km in length. This study used multi-spectral imagery from MODIS data, to develop algorithms for daytime as well as nighttime detection of fog during winter 2000 to 2014 over the IGP. Specifically, our nighttime detection algorithm employs a bispectral thresholding technique, involving brightness temperature difference (BTD) between two spectral channels- 3.9 and 11.02μm. The theoretical basis for the detection using the 3.9 μm and 11.02 μm channels rely on the particular emissive properties of the two channels for fog droplets (Bendix and Bachmann, 1991). The small droplets found in fog are less emissive at 3.9 μm than at 11.02 μm. Brightness temperatures computed from corresponding radiance data (MODIS Level-1B) of band 22 (3.9 μm) and band 31 (11.02 μm), in conjunction with theoretical calculations from a radiative transfer (RT) model, were utilized to evaluate threshold value of BTD. Using theoretical RT calculations and automated analysis of hundreds of moderately high resolution satellite imagery (pixel resolution of 1km), our threshold cutoff for foggy pixels results in BTD value of 4 (deg) K. Additionally, to minimize contamination, we apply a spatial variability filter to discriminate the uniform texture of fog from other low-level clouds. A similar methodology based on BTD is also tested for daytime fog detection and separation from other cloud types. Furthermore, on the basis of operational multispectral retrievals of cloud properties (cloud effective radius, cloud top pressure, and cloud fraction) from MODIS, we have also processed spatial occurrences of fog climatology from 2000 to 2014. To validate our satellite retrieval algorithm of fog detection from

  4. Spatial and Temporal Analysis of Winter Fog Episodes over South Asia by exploiting ground-based and satellite observations

    Science.gov (United States)

    Fahim Khokhar, Muhammad; Yasmin, Naila; Zaib, Naila; Murtaza, Rabia; Noreen, Asma; Ishtiaq, Hira; Khayyam, Junaid; Panday, Arnico

    2016-04-01

    The South Asian region in general and the Indo-Gangetic Plains (IGP) in particular hold about 1/6th of the world's population and is considered as one of the major hotspots with increasing air pollution. Due to growing population and globalization, South Asia is experiencing high transformations in the urban and industrial sectors. Fog is one of the meteorological/environmental phenomena which can generate significant social and economic problems especially havoc to air and road traffic. Meteorological stations provide information about the fog episodes only on the basis of point observation. Continuous monitoring as well as a spatially coherent picture of fog distribution can only be possible through the use of satellite imagery. Current study focus on winter fog episodes over South Asian region using Moderate Resolution Image Spectrometer (MODIS) Level 2 Terra Product and other MODIS Aerosol Product in addition to ground-based sampling and AERONET measurements. MODIS Corrected Reflectance RGBs are used to analyse the spatial extent of fog over study area. MOD04 level 2 Collection 6 data is used to study aerosol load and distribution which are further characterised by using aerosol type land product of MODIS. In order to study the variation of ground based observations from satellite data MODIS, AERONET and high volume air Sampler were used. Main objective of this study was to explore the spatial extent of fog, its causes and to analyse the Aerosol Optical Depth (AOD) over South Asia with particular focus over Indo-Gangetic Plains (IGP). Current studies show a descent increase in AOD from past few decades over South Asia and is contributing to poor air quality in the region due to growing population, urbanization, and industrialization. Smoke and absorbing aerosol are major constituent of fog over South Asia. Furthermore, winter 2014-15 extended span of Fog was also observed over South Asia. A significant correlation between MODIS (AOD) and AERONET Station (AOD

  5. Preliminary results of the PreViBOSS project: description of the fog life cycle by ground-based and satellite observation

    Science.gov (United States)

    Elias, Thierry; Jolivet, Dominique; Dupont, Jean-Charles; Haeffelin, Martial; Burnet, Frédéric

    2012-11-01

    The instrument set-up designed by the PreViBOSS project for the ParisFog field campaign is suitable to sound microphysical properties of droplets and interstitial aerosols during developed fog in a semi-urban environment. Developed fog is defined as LWC computed by Mie theory applied on size distribution observed during developed fog in ambient conditions by both PALAS WELAS and DMT FM100. Comparison with particle extinction coefficient directly measured by the Degreanne DF20 visibilimeter demonstrates satisfying agreement, within combined uncertainties. Ratio of computed over measured particle extinction coefficient is 1.15+/-0.35. Visibility smaller than 1000 m at 3 m above ground level is observed not only during developed fog but also during shallow fog, which presents a significant vertical gradient, as ΔT > 0.4 K/m. In this case, LWC is highly variable and may be observed below 7 mg m-3. The consequent month average of LWC is 30+/-80 mg m-3. The optical counters miss large droplets significantly contributing to extinction in shallow fogs. Consequently, it is not possible to reproduce with satisfaction the particle extinction coefficient in shallow fog. Fog type may be distinguished by association of groundbased visibilimeter and MSG/SEVIRI. When clear-sky is given by EUMETSAT/NWCSAF cloud type product while visibility is observed smaller than 1000 m at SIRTA, in 75% cases a shallow fog occurs, and in other cases, horizontal heterogeneity characterises the developed fog within the SIRTA pixel, as during the dissipation phase. Moreover, consistently, low and very low clouds are mostly detected by the satellite product when developed fog is observed by ground-based instrumentation.

  6. Satellite based classification (haze, fog) and affected area estimation over Indo - Pak Sub-Continent

    Science.gov (United States)

    Ghauri, Badar; Zafar, Sumaira

    2016-07-01

    Northern Pakistan and bordering Indian Punjab experience intense smog and fog during fall and winters. Environmentalists have been raising their voices over the situation and demanded control over regional emissions to save the livelihood of millions of dwellers whose trade, commerce and agriculture is at stake because of long smog/ fog spells.. This paper estimates the area affected by haze, smog and fog during 2006- 2010. MODIS (geo-referenced MODIS subsets India1, 2 &3) of the area in Pakistan and India from 2006 to 2010 for the period October to February) were analyzed using state of the art software ENVI 4.2 and ArcGIS 10.2. This process resulted in area belonging to each class that is; haze, smog and fog. On the basis of density, haze and fog cover was determined. Variations in fog cover, its density and identification of location of fog initiation process were also determined using near real time (30 minutes) METEOSAT-7 IODC data where actually fog formation started and then extended to the area of favorable conditions. Haze has been noticed to intensify due to massive burning of agricultural waste (rice husk) in India and Pakistan towards the end of October each year. MODIS thermal anomalies/fire data (MYD 14) were also used to verify this activity on the ground, which results in hazy conditions at regional level during fall months. Haze-affected area during 2006 to 2010 in Pakistan ranged from 155,000 Km2 to 354,000 Km2 and in India it ranged from 333,000 Km2 to 846,000 Km2. Similarly winter fog cover during this period in Pakistan varied from 136,000 Km2 to 381,000 Km2 and in India it was estimated at 327,000 Km2 to 566,000 Km2. This phenomenon was more prominent in India than in Pakistan where and fog cover was at least twice than that was observed in Pakistan. It has been noted that area covered by fog, smog and haze doubled during the study period in the region. Atmospheric dimming during autumn/ fall also reduces the mixing height leading to greater

  7. Development of hybrid fog detection algorithm (FDA) using satellite and ground observation data for nighttime

    Science.gov (United States)

    Kim, So-Hyeong; Han, Ji-Hae; Suh, Myoung-Seok

    2017-04-01

    In this study, we developed a hybrid fog detection algorithm (FDA) using AHI/Himawari-8 satellite and ground observation data for nighttime. In order to detect fog at nighttime, Dual Channel Difference (DCD) method based on the emissivity difference between SWIR and IR1 is most widely used. DCD is good at discriminating fog from other things (middle/high clouds, clear sea and land). However, it is difficult to distinguish fog from low clouds. In order to separate the low clouds from the pixels that satisfy the thresholds of fog in the DCD test, we conducted supplementary tests such as normalized local standard derivation (NLSD) of BT11 and the difference of fog top temperature (BT11) and air temperature (Ta) from NWP data (SST from OSTIA data). These tests are based on the larger homogeneity of fog top than low cloud tops and the similarity of fog top temperature and Ta (SST). Threshold values for the three tests were optimized through ROC analysis for the selected fog cases. In addition, considering the spatial continuity of fog, post-processing was performed to detect the missed pixels, in particular, at edge of fog or sub-pixel size fog. The final fog detection results are presented by fog probability (0 100 %). Validation was conducted by comparing fog detection probability with the ground observed visibility data from KMA. The validation results showed that POD and FAR are ranged from 0.70 0.94 and 0.45 0.72, respectively. The quantitative validation and visual inspection indicate that current FDA has a tendency to over-detect the fog. So, more works which reducing the FAR is needed. In the future, we will also validate sea fog using CALIPSO data.

  8. Near-real time Monitoring of the widespread winter Fog over the Indo-Gangetic Plains using satellite data

    Science.gov (United States)

    Patil, D. L.; Gautam, R.; Rizvi, S.; Singh, M. K.

    2016-12-01

    The persistent and widespread winter fog impacts the Indo-Gangetic Plains (IGP) on an annual basis, disrupting day-to-day lives of millions of people in parts of northern India, Pakistan, Nepal and Bangladesh. The IGP is a densely-populated region located south of the Himalaya, in the northern parts of south Asia. During the past three decades or so, associated with growing population and energy demands, the IGP has witnessed strong upward trends in air pollution, particularly leading to poor air quality in the winter months. Co-occurring with the dense haze over the IGP, severe fog episodes persist throughout the months of December and January. Building on our recent work on satellite-based detection of fog, we have further extended the detection capability towards the development of a near-real time (NRT) fog monitoring system using satellite radiances and products. Here, we use multi-spectral radiances and aerosol/cloud retrievals from Terra/Aqua MODIS data for NRT fog monitoring over the IGP for both daytime as well as nighttime. Specifically, the nighttime fog detection algorithm employs a bi-spectral brightness temperature difference technique between two spectral channels: 3.9 μm and 11 μm. Our ongoing efforts also include extending fog detection capability in NRT to geostationary satellites, for providing continuous monitoring of the onset, evolution and spatial-temporal variation of fog, as well as the geospatial integration of surface meteorological observations of visibility, relative humidity, temperature. We anticipate that the ongoing and future development of a fog monitoring system may be of particular assistance to air and rail transportation management, as well as of general interest to the public. The outputs of fog detection algorithm and related aerosol/cloud parameters are operationally disseminated via http://fogsouthasia.com/.

  9. Persistent and Widespread Winter Haze & Fog over the Indo-Gangetic Plains: A climatological perspective from satellite observations

    Science.gov (United States)

    Gautam, R.

    2014-12-01

    Each year during winter season (December-January), dense fog engulfs the Indo-Gangetic Plains (IGP) in southern Asia, for more than a month, disrupting daily life of millions of people inhabiting the IGP. The widespread nature of the fog is frequently visible in satellite imagery, extending over a stretch of ~1500 km; that covers parts of Pakistan, northern India, Nepal and Bangladesh. Both, haze and fog are a tightly-coupled system over the IGP, during winter months, and have been a major environmental/climatic issue since the past several decades. Trends in poor visibility suggest a significant increase in worsening air quality and foggy days over the IGP. The persistent and widespread nature of the winter haze and fog is strongly influenced by the regional meteorology during wintertime, i.e. a stable boundary layer, low temperatures, high relative humidity and light winds. The valley-type topography of the IGP, adjacent to the towering Himalaya, and high concentrations of pollution aerosols, further favors the persistence of hazy/foggy conditions. A satellite-based observational portrayal will be presented, using various cloud, aerosol and radiation datasets, to characterize the widespread nature of winter haze and fog, based on a multi-sensor assessment from MODIS, CERES, AVHRR and CALIPSO datasets. More specifically, based on these observations, we will present results on: long-term trends/variability of winter haze and fog, vertical characterization of aerosol/fog/low-clouds, as well as assessment of the direct radiative effect of the region-wide haze/fog system. Results from this work are anticipated to shed light on the overall interactions within the highly persistent and tightly-coupled haze-fog phenomena. Additionally, against the backdrop of a changing climate scenario, possible linkages between the winter-time fog cover, regional meteorology and aerosol loading will also be discussed over the IGP.

  10. Winter fog monitoring over south asia by using multi satellite data

    Science.gov (United States)

    Yasmin, Naila

    2016-07-01

    committing The South Asian region in general and the Indo-Gangetic Plains (IGP) in particular hold about 1/6th of the world's population and is considered as one of the major hotspots of increasing atmospheric pollution. Due to growing population and globalization, South Asia is experiencing high transformations in the urban and industrial sectors. Fog is one of the meteorological/environmental phenomena which can generate significant social and economic problems especially a major havoc to air and road traffic. Meteorological stations provide information about the fog episodes only on the basis of point observation. Continuous monitoring as well as a spatially coherent picture of fog distribution can only be possible through the use of satellite imagery. Current study focus on winter fog episodes over South Asian region using Moderate Resolution Image Spectrometer (MODIS) Level 2 terra Product and MODIS Aerosol Product and OMI Absorbing Aerosol Index. The datasets used in this study includes MODIS Corrected Reflectance RGBs are used to analyse fog situation over study area. MOD04 level 2 Collection 6 data is used to study aerosol load and distribution which are characterised using aerosol type land. In order to study the variation of ground based observations from satellite data MODIS, CALIPSO, AERONET and high volume air Sampler were used. Objectives of the study was to map the spatial extent of fog as well as monitor its causes and similarly to analyze the Aerosol Optical Depth (AOD) over South Asia with particular focus over Indo Gangetic Plans (IGP). Current studies show an increase in AOD from past few decades over South Asia and is contributing to poor air quality in the region due to growing population, urbanization, and industrialization. Smoke and absorbing aerosol are major constituent of fog over south Asia. Furthermore, winter 2014-15 extended span of Fog was also observed over South Asia. A significant correlation between MODIS (AOD) and AERONET

  11. Fog

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Early in the morning forclouded up green trees, tallbamboos, lush grass andfresh flowers in the park. Ithanged over the lake like asoft mass of cotton. Howthick the fog was!However in the eyes oflovers the fog seemed to bethe first warm sparklingsnow or a tender passioncoming from their hearts.Love is a lingeringsentiment that can not beunraveled...A young man and a youngwoman were rambling sideby side. He was handsomeand she pretty like the heroand heroine of many stories.She was vivacious. Feelingelated, ...

  12. Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

    Science.gov (United States)

    Wærsted, Eivind G.; Haeffelin, Martial; Dupont, Jean-Charles; Delanoë, Julien; Dubuisson, Philippe

    2017-09-01

    Radiative cooling and heating impact the liquid water balance of fog and therefore play an important role in determining their persistence or dissipation. We demonstrate that a quantitative analysis of the radiation-driven condensation and evaporation is possible in real time using ground-based remote sensing observations (cloud radar, ceilometer, microwave radiometer). Seven continental fog events in midlatitude winter are studied, and the radiative processes are further explored through sensitivity studies. The longwave (LW) radiative cooling of the fog is able to produce 40-70 g m-2 h-1 of liquid water by condensation when the fog liquid water path exceeds 30 g m-2 and there are no clouds above the fog, which corresponds to renewing the fog water in 0.5-2 h. The variability is related to fog temperature and atmospheric humidity, with warmer fog below a drier atmosphere producing more liquid water. The appearance of a cloud layer above the fog strongly reduces the LW cooling relative to a situation with no cloud above; the effect is strongest for a low cloud, when the reduction can reach 100 %. Consequently, the appearance of clouds above will perturb the liquid water balance in the fog and may therefore induce fog dissipation. Shortwave (SW) radiative heating by absorption by fog droplets is smaller than the LW cooling, but it can contribute significantly, inducing 10-15 g m-2 h-1 of evaporation in thick fog at (winter) midday. The absorption of SW radiation by unactivated aerosols inside the fog is likely less than 30 % of the SW absorption by the water droplets, in most cases. However, the aerosols may contribute more significantly if the air mass contains a high concentration of absorbing aerosols. The absorbed radiation at the surface can reach 40-120 W m-2 during the daytime depending on the fog thickness. As in situ measurements indicate that 20-40 % of this energy is transferred to the fog as sensible heat, this surface absorption can contribute

  13. Improvement of the Fog Detection based on Himawari-8 over the Korean Peninsula

    Science.gov (United States)

    Lee, H. W.; Sohn, E. H.; Ryu, G. H.; Jang, J. D.

    2016-12-01

    Korea Meteorological Administration (KMA) services fog detection using Communication, Ocean and Meteorological Satellite (COMS) data for nowcasting. But, it is not easy to detect fog over complex terrain using COMS. Recently, Japan Meteorological Agency launched Himawari-8 geostationary satellite and releases data from July 2015. It has better spatial and spectral resolution than COMS, so it seems that Himawari-8 may have good sensitivity to detect fog. In this study, fog detection based on COMS methodology is applied and tested using Himawari-8 measurement over the Korean peninsula. A method has four threshold tests as follows: 1. Dual Channel Difference (DCD) between 12.3㎛ and 13.3㎛ (DCD1) test to remove higher cloud. 2. DCD between 3.9㎛ and 10.4㎛ (DCD2) test to detect night fog. 3. DCD between Clear Sky Brightness Temperature (CSTB; Maximum brightness temperature of 10.4㎛ during before 15 days) and 10.4㎛ (DCD3) test to set bottom layer. 4. 0.64㎛ albedo test to detect day fog. The fog detection from COMS and Himawari-8 were compared to understand each characteristics and performance at same condition. At night, typically showing similar DCD2, Himawari-8 has smaller value than COMS in the fog area. It seems that Himawari-8 receives a stronger signal because Spectral Response Function (SRF) of AHI is narrower than MI. In addition, improved spatial resolution (AHI: 2km; MI: 4km for IR channels) might enhance sensitivity of fog detection over mountainous area (Fig.1) In evaluation of accuracy, Probability of Detection (POD) and False Alarm Ratio (FAR) of Himawari-8 are 73%, 39% respectively (COMS POD: 65%; FAR: 55%) below 1K of DCD3 at Oct. 2015, when the radiation fog occurs a lot in Korea. The result shows that Himawari-8 has good performance of fog detection near the ground. Also, It is analyzed that reduce over-detection by using a variety of channels. In conclusion, fog detection using Himawari-8 data and similar methodology with COMS shows

  14. 20 years of KVH fiber optic gyro technology: the evolution from large, low performance FOGs to compact, precise FOGs and FOG-based inertial systems

    Science.gov (United States)

    Napoli, Jay

    2016-05-01

    Precision fiber optic gyroscopes (FOGs) are critical components for an array of platforms and applications ranging from stabilization and pointing orientation of payloads and platforms to navigation and control for unmanned and autonomous systems. In addition, FOG-based inertial systems provide extremely accurate data for geo-referencing systems. Significant improvements in the performance of FOGs and FOG-based inertial systems at KVH are due, in large part, to advancements in the design and manufacture of optical fiber, as well as in manufacturing operations and signal processing. Open loop FOGs, such as those developed and manufactured by KVH Industries, offer tactical-grade performance in a robust, small package. The success of KVH FOGs and FOG-based inertial systems is due to innovations in key fields, including the development of proprietary D-shaped fiber with an elliptical core, and KVH's unique ThinFiber. KVH continually improves its FOG manufacturing processes and signal processing, which result in improved accuracies across its entire FOG product line. KVH acquired its FOG capabilities, including its patented E•Core fiber, when the company purchased Andrew Corporation's Fiber Optic Group in 1997. E•Core fiber is unique in that the light-guiding core - critical to the FOG's performance - is elliptically shaped. The elliptical core produces a fiber that has low loss and high polarization-maintaining ability. In 2010, KVH developed its ThinFiber, a 170-micron diameter fiber that retains the full performance characteristics of E•Core fiber. ThinFiber has enabled the development of very compact, high-performance open-loop FOGs, which are also used in a line of FOG-based inertial measurement units and inertial navigation systems.

  15. Radiation in fog: quantification of the impact on fog liquid water based on ground-based remote sensing

    Directory of Open Access Journals (Sweden)

    E. G. Wærsted

    2017-09-01

    Full Text Available Radiative cooling and heating impact the liquid water balance of fog and therefore play an important role in determining their persistence or dissipation. We demonstrate that a quantitative analysis of the radiation-driven condensation and evaporation is possible in real time using ground-based remote sensing observations (cloud radar, ceilometer, microwave radiometer. Seven continental fog events in midlatitude winter are studied, and the radiative processes are further explored through sensitivity studies. The longwave (LW radiative cooling of the fog is able to produce 40–70 g m−2 h−1 of liquid water by condensation when the fog liquid water path exceeds 30 g m−2 and there are no clouds above the fog, which corresponds to renewing the fog water in 0.5–2 h. The variability is related to fog temperature and atmospheric humidity, with warmer fog below a drier atmosphere producing more liquid water. The appearance of a cloud layer above the fog strongly reduces the LW cooling relative to a situation with no cloud above; the effect is strongest for a low cloud, when the reduction can reach 100 %. Consequently, the appearance of clouds above will perturb the liquid water balance in the fog and may therefore induce fog dissipation. Shortwave (SW radiative heating by absorption by fog droplets is smaller than the LW cooling, but it can contribute significantly, inducing 10–15 g m−2 h−1 of evaporation in thick fog at (winter midday. The absorption of SW radiation by unactivated aerosols inside the fog is likely less than 30 % of the SW absorption by the water droplets, in most cases. However, the aerosols may contribute more significantly if the air mass contains a high concentration of absorbing aerosols. The absorbed radiation at the surface can reach 40–120 W m−2 during the daytime depending on the fog thickness. As in situ measurements indicate that 20–40 % of this energy is transferred to the fog

  16. Machine learning based Intelligent cognitive network using fog computing

    Science.gov (United States)

    Lu, Jingyang; Li, Lun; Chen, Genshe; Shen, Dan; Pham, Khanh; Blasch, Erik

    2017-05-01

    In this paper, a Cognitive Radio Network (CRN) based on artificial intelligence is proposed to distribute the limited radio spectrum resources more efficiently. The CRN framework can analyze the time-sensitive signal data close to the signal source using fog computing with different types of machine learning techniques. Depending on the computational capabilities of the fog nodes, different features and machine learning techniques are chosen to optimize spectrum allocation. Also, the computing nodes send the periodic signal summary which is much smaller than the original signal to the cloud so that the overall system spectrum source allocation strategies are dynamically updated. Applying fog computing, the system is more adaptive to the local environment and robust to spectrum changes. As most of the signal data is processed at the fog level, it further strengthens the system security by reducing the communication burden of the communications network.

  17. Forecasting of radiation fog with a new decision support system based on automatic LIDAR-ceilometer measurements

    Science.gov (United States)

    Laffineur, Quentin; Haeffelin, Martial; Bravo-Aranda, Juan-Antonio; Drouin, Marc-Antoine; Casquero-Vera, Juan-Andrés; Dupont, Jean-Charles; De Backer, Hugo

    2017-04-01

    Radiation fog is the most frequent cause of surface visibility below 1 km, and is one of the most common and persistent weather hazards encountered in aviation and to nearly all forms of surface transport. Forecasting radiation fog can be difficult, a number of approaches have been used to integrate the satellite data, numerical modeling and standard surface observations. These approaches lack generally the vertical and temporal resolution, representation of boundary layer and microphysical processes. They typically do not represent accurately the activation processes of fog droplets that depend on the chemical and physical properties of the aerosols. The automatic LIDAR-ceilometer (ALC) primarily designed for cloud base height detection has greatly improved over the last years and now offers the opportunity to analyse in near real-time the backscatter signal in the boundary layer that potentially contains major information to predict radiation fog formation or not. During the preliminary stage of fog formation, the backscatter profile may be influenced by atmospheric humidity due to the presence in the atmosphere of hygroscopic aerosols that see their size increase with their moisture content inducing an increase of the backscatter magnitude. In the framework of TOPROF (COST-ACTION, http://www.toprof.imaa.cnr.it/) activities, collaboration was initiated between the Royal Meteorological Institute of Belgium (RMI) and the Site Instrumental de Recherche par Télédéction Atmosphérique (SIRTA, IPSL) to develop a forward stepwise screening algorithm (PARAFOG) to help prediction of radiation fog formation. PARAFOG is a new decision support system for radiation fog forecasting based on analysis of the attenuated backscatter measured by ALCs, found at most airports, which provides information about the aerosol-particle hygroscopic growth process (Haeffelin et al., 2016). The monitoring of this hygroscopic growth process could provide useful warning to forecasters, in

  18. The Pacific Coast Fog Project: A Multi-disciplinary Effort to Provide Web-based Climate Products for Ecologists

    Science.gov (United States)

    Torregrosa, A.; Combs, C.; Ellrod, G. P.; Faloona, I. C.; Gultepe, I.

    2012-12-01

    project leverages results from existing research projects, such as long-term fog climatology based on surface land and buoy observations ongoing at the University of Washington, and California fog climatology derived from 11 years of Geostationary Operational Environmental Satellite (GOES) data underway at the Cooperative Institute for Research in the Atmosphere (CIRA) at Colorado State University in Ft. Collins. There are numerous other collaborators from academia (such as several University of California oceanographic and atmospheric science departments) and government agencies (U. S. Geological Survey, National Weather Service, NASA, and Environment Canada). During the summer of 2012, a pilot project deployed sensors on loan from Environment Canada to augment existing instruments at Bodega Bay, California and Pepperwood Preserve in Sonoma County to gather important data sets on mesoscale and microphysical variables including liquid water content, surface wind, visibility, temperature, and boundary layer height that will be used to better describe the characteristics of coastal fog. Sample transects for significant fog events along with examples of antecedent synoptic weather conditions and mockups of possible graphic products for end users will be shown.

  19. A diagnostic study of Antarctic fog

    Science.gov (United States)

    Lazzara, Matthew A.

    2008-10-01

    The United States Antarctic Program (USAP) is the largest scientific research program in the Antarctic and requires a considerable aviation operation. Although fog is one of the top three forecast problems related to flights aborted due to weather, it is largely unstudied. The objective of this project is to gain an understanding of fog that affects McMurdo Station, Antarctica and its nearby airfields. This understanding is gained through analyses of surface based weather observations, satellite measurements and numerical weather prediction models. Multi-channel satellite observations indicate that most austral summer fog events are "advective" in nature. This is supported by weather observations from McMurdo Station and nearby airfields where fog occurs at moderate wind speeds, and primarily from the eastward direction. Analyses using both a back trajectory model and mesoscale numerical model are consistent with this finding. The primary source region for fog is found to be from the southeast over the Ross Ice Shelf (72% of the cases studied), while only a minority of cases (23%) reveals a secondary source of fog from the north along the Scott Coast with airflow influences from the East Antarctic Plateau. McMurdo experiences two fog seasons with a primary peak in January and a secondary peak in September. Fog events are often short lived---typically 1 to 3 hours, though some can last up to 30 hours. Fog occurrences over the last 30 years appear to be decreasing. Time series analysis between the observed fog variability and large-scale circulations (e.g., El Nino, Antarctic Oscillation) yielded no correlations, while there is only a limited relationship of fog occurrence to ice concentration in nearby Lewis Bay and McMurdo Sound. Fog is more likely to take place at the nearby airfields rather than at McMurdo Station, which is consistent with the advective nature of the fog.

  20. Challenging Issues on fog forecast with a three-dimensional fog forecast model

    Science.gov (United States)

    Masbou, M.

    2012-12-01

    Fog has a significant impact on economical aspect (traffic management and safety) as well as on environmental issues (fresh water source for the population and the biosphere in arid region). However, reliable fog and visibility forecasts stay challenging issue. Fog is generally a small scale phenomenon which is mostly affected by local advective transport, radiation, topography, vegetation, turbulent mixing at the surface as well as its microphysical structure. In order to consider these intertwined processes, the three-dimensional fog forecast model, COSMO-FOG, with a high vertical resolution with different microphysical complexity has been developed. This model includes a microphysical parameterisation based on the one-dimensional fog forecast model. The implementation of the cloud water droplets as a new prognostic variable allows a detailed definition of the sedimentation processes and the variations in visibility. Moreover, the turbulence scheme, based on a Mellor-Yamada 2.5 order and a closure of a 2nd order has been modified to improve the model behaviour in case of a stable atmosphere structure, occurring typically during night radiative fog episodes. The potential of COSMO-FOG will be presented in some realistic fog situations (flat, bumpy and complex terrain). The fog spatial extension will be compared with MSG satellite products for fog and low cloud. The interplays between dynamical, thermodynamical patterns and the soil-atmosphere interactions will be presented.

  1. Multirule Based Diagnostic Approach for the Fog Predictions Using WRF Modelling Tool

    Directory of Open Access Journals (Sweden)

    Swagata Payra

    2014-01-01

    Full Text Available The prediction of fog onset remains difficult despite the progress in numerical weather prediction. It is a complex process and requires adequate representation of the local perturbations in weather prediction models. It mainly depends upon microphysical and mesoscale processes that act within the boundary layer. This study utilizes a multirule based diagnostic (MRD approach using postprocessing of the model simulations for fog predictions. The empiricism involved in this approach is mainly to bridge the gap between mesoscale and microscale variables, which are related to mechanism of the fog formation. Fog occurrence is a common phenomenon during winter season over Delhi, India, with the passage of the western disturbances across northwestern part of the country accompanied with significant amount of moisture. This study implements the above cited approach for the prediction of occurrences of fog and its onset time over Delhi. For this purpose, a high resolution weather research and forecasting (WRF model is used for fog simulations. The study involves depiction of model validation and postprocessing of the model simulations for MRD approach and its subsequent application to fog predictions. Through this approach model identified foggy and nonfoggy days successfully 94% of the time. Further, the onset of fog events is well captured within an accuracy of 30–90 minutes. This study demonstrates that the multirule based postprocessing approach is a useful and highly promising tool in improving the fog predictions.

  2. Temperature Drift Modeling of FOG Based on LS-WSVM

    Institute of Scientific and Technical Information of China (English)

    WANG Li-ping; KONG Xiao-mei; FU Meng-yin; WANG Mei-ling; ZHANG Jia-wen; JIANG Ming

    2008-01-01

    Large temperature drift is an important factor for improving the performance of FOG. A trend term of temperature drift of FOG is obtained using stationary wavelets transform, and an FOG drift algorithm with least squares wavelet support vector machine (LS-WSVM) is developed. The algorithm used Maxihat wavelet as a kernel function of LSWSVM to establish an FOG drift model. It has better modeling precise than LS-WSVM model with Gauss kernel. Results indicate the efficiency of this algorithm of LS-WSVM.

  3. An object-oriented based daytime over land fog detection approach using EOS/MODIS data

    Science.gov (United States)

    Wen, Xiongfei; Liu, Liangming; Li, Wei; Dong, Pei

    2009-09-01

    A new algorithm is presented for land fog detection from daytime image of Earth Observation System Moderate Resolution Imaging Spectroradiometer (EOS/MODIS) data. Due to its outstanding spatial and spectral resolutions, this image is an ideal data source for fog detection. The algorithm utilizes an object-oriented technique to separate fog from other cloud types. In this paper, MOD35 product is first introduced to exclude cloud-free areas, and high clouds are removed with MODIS 26 band, and then a parameter named Normalized Difference Fog Index (NDFI) is proposed based on Streamer radiative model and MODIS data for fog detection. Through segmenting NDFI image into regions of pixels, and computing attributes (e.g. mean value of brightness temperature) for each region to create objects, each object could be identified based on the attributes selected to determine whether belongs to fog or cloud. Algorithm's performance is evaluated against ground-based measurements over China in winter. The algorithm is proved to be effective in detecting fog accurately based on two different test cases.

  4. FOGCAST: Probabilistic fog forecasting based on operational (high-resolution) NWP models

    Science.gov (United States)

    Masbou, M.; Hacker, M.; Bentzien, S.

    2013-12-01

    The presence of fog and low clouds in the lower atmosphere can have a critical impact on both airborne and ground transports and is often connected with serious accidents. The improvement of localization, duration and variations in visibility therefore holds an immense operational value. Fog is generally a small scale phenomenon and mostly affected by local advective transport, radiation, turbulent mixing at the surface as well as its microphysical structure. Sophisticated three-dimensional fog models, based on advanced microphysical parameterization schemes and high vertical resolution, have been already developed and give promising results. Nevertheless, the computational time is beyond the range of an operational setup. Therefore, mesoscale numerical weather prediction models are generally used for forecasting all kinds of weather situations. In spite of numerous improvements, a large uncertainty of small scale weather events inherent in deterministic prediction cannot be evaluated adequately. Probabilistic guidance is necessary to assess these uncertainties and give reliable forecasts. In this study, fog forecasts are obtained by a diagnosis scheme similar to Fog Stability Index (FSI) based on COSMO-DE model outputs. COSMO-DE I the German-focused high-resolution operational weather prediction model of the German Meteorological Service. The FSI and the respective fog occurrence probability is optimized and calibrated with statistical postprocessing in terms of logistic regression. In a second step, the predictor number of the FOGCAST model has been optimized by use of the LASSO-method (Least Absolute Shrinkage and Selection Operator). The results will present objective out-of-sample verification based on the Brier score and is performed for station data over Germany. Furthermore, the probabilistic fog forecast approach, FOGCAST, serves as a benchmark for the evaluation of more sophisticated 3D fog models. Several versions have been set up based on different

  5. 静止气象卫星资料在白天海雾动态监测中的应用%Dynamic Detection of Daytime Sea Fog Using Geostationary Meteorological Satellite Data

    Institute of Scientific and Technical Information of China (English)

    邓玉娇; 田永杰; 王捷纯

    2016-01-01

    利用国产静止气象卫星FY2E数据建立白天海雾监测算法,利用VIS通道反射率实现海面与云雾区分离,利用IR1通道估算云高实现中高云与低层云雾的分离,利用VIS、IR1、IR4波段构建雾判识指数初步实现海雾与低云的分离,利用平滑稳定度指数进一步实现海雾与低云的分离,最终得到的海雾监测小时产品。根据2014年1~5月份广东沿海13个海雾监站点的实测数据,对本算法所得海雾产品进行精度检验,计算得到检测率POD为92.7%,漏检率FAR为29.4%,总体精度为64.7%。个例分析可知,静止卫星资料因其具备较高的时间分辨率,可较好实现对海雾过程的连续、动态监测。%Using Channel VIS, IR1 and IR4 of the domestic geostationary meteorological satellite FY2E/VISSR data, the multichannel method was proposed to detect the daytime sea fog. Firstly, the existing dynamic threshold method was revised in the paper in order to improve the accuracy of distinguishing sea surface from cloud and fog. The thresholds were based on the histogram statistics of the reflectance of Channel VIS, and ad-justed dynamically in different regions or different seasons. Secondly, cloud height estimated from the bright temperature of Channel IR1 was used to separate middle-and high-level cloud from low-level cloud and fog. When the height was greater than 2 000 m, the object was middle- and high-level cloud. Thirdly, fog index computed from Channel IR1,IR4 and VIS was used to divide low-level cloud from fog preliminarily. If the fog index was greater than 20, the object was possibly fog. Finally, smoothness and stability index were used to tell fog from low-level cloud further, and it was greater than 0.9 for fog. Ground-based fog observation data from thirteen sites on the coast of Guangdong were used to do the verification of the FY-2E fog detection prod-ucts, which were Zhanjiang, Wuchuan, Leizhou, Yangjiang, Shangchuandao, Zhuhai

  6. Research on day fog detection based on FY2E image%针对FY2E影像的白天雾检测研究

    Institute of Scientific and Technical Information of China (English)

    李维; 刘良明; 杜娟

    2012-01-01

    传统基于遥感的雾检测方法,主要利用极轨卫星遥感影像(如MODIS、AVHRR)建立雾检测模型,尽管极轨卫星影像的光谱信息丰富,但是其过境时间一般比较迟,MODIS为当地时间11点左右,AVHRR为当地时间14时左右,而且单颗极轨卫星的时间分辨率为一天左右,无法很好地满足雾检测的实际需要.针对静止卫星的雾检测研究还比较少,其主要思想是利用光谱差异进行雾检测.选择FY2E影像并结合面向对象思想开展白天雾检测研究,利用Streamer辐射传输模型针对云、雾、雪、地表对FY2E影像的5个波段进行模拟,构建雪检测指数(SDI)、雾检测指数(FDI)等6个雾检测特征参数;选择特征波段,利用MeanShift分割方法完成FY2E影像的分割,基于雾检测特征参数构建雾检测区域特征参数;建立白天雾检测模型,选择案例数据进行实验,并利用地面站点实测数据进行精度评定.实验结果表明,提出的雾检测模型取得了很好的检测效果.%Traditional fog detection methods based on remote sensing mainly use polar-orbiting satellite images (such as MODIS and AVHRR) to establish fog detection model. Although the spectral information of polar-orbiting satellite is richer than geostationary satellite, the transit time is usually relatively late in the day(MODIS is about 11 o' clock and AVHRR is about 14 o' clock) and the time resolution of single polar-orbiting satellite is about one day which is unable to meet the requirements of operational fog detection. The fog detection research on stationary satellite is relatively little and the main idea is to use spectral differences to detect fog. This paper chooses FY2E image to research on day fog detection based on object-oriented approach. Streamer radiative transfer model is used to simulate the 5 bands of FY2E image for fog, cloud, ice and surface combined with measured data, six fog detection characteristic parameters are established

  7. FogGIS: Fog Computing for Geospatial Big Data Analytics

    OpenAIRE

    Barik, Rabindra K.; Dubey, Harishchandra; Samaddar, Arun B.; Gupta, Rajan D.; Ray, Prakash K.

    2016-01-01

    Cloud Geographic Information Systems (GIS) has emerged as a tool for analysis, processing and transmission of geospatial data. The Fog computing is a paradigm where Fog devices help to increase throughput and reduce latency at the edge of the client. This paper developed a Fog-based framework named Fog GIS for mining analytics from geospatial data. We built a prototype using Intel Edison, an embedded microprocessor. We validated the FogGIS by doing preliminary analysis. including compression,...

  8. Thermal strain along optical fiber in lightweight composite FOG : Brillouin-based distributed measurement and finite element analysis

    Science.gov (United States)

    Minakuchi, Shu; Sanada, Teruhisa; Takeda, Nobuo; Mitani, Shinji; Mizutani, Tadahito; Sasaki, Yoshinobu; Shinozaki, Keisuke

    2014-05-01

    Thermal strain significantly affects stability of fiber optic gyroscope (FOG) performance. This study investigates thermal strain development in a lightweight carbon fiber reinforced plastic (CFRP) FOG under thermal vacuum condition simulating space environment. First, we measure thermal strain distribution along an optical fiber in a CFRP FOG using a Brillouin-based high-spatial resolution system. The key strain profile is clarified and the strain development is simulated using finite element analysis. Finally, several constituent materials for FOG are quantitatively compared from the aspect of the maximum thermal strain and the density, confirming the clear advantage of CFRP.

  9. A Source Anonymity-Based Lightweight Secure AODV Protocol for Fog-Based MANET

    Directory of Open Access Journals (Sweden)

    Weidong Fang

    2017-06-01

    Full Text Available Fog-based MANET (Mobile Ad hoc networks is a novel paradigm of a mobile ad hoc network with the advantages of both mobility and fog computing. Meanwhile, as traditional routing protocol, ad hoc on-demand distance vector (AODV routing protocol has been applied widely in fog-based MANET. Currently, how to improve the transmission performance and enhance security are the two major aspects in AODV’s research field. However, the researches on joint energy efficiency and security seem to be seldom considered. In this paper, we propose a source anonymity-based lightweight secure AODV (SAL-SAODV routing protocol to meet the above requirements. In SAL-SAODV protocol, source anonymous and secure transmitting schemes are proposed and applied. The scheme involves the following three parts: the source anonymity algorithm is employed to achieve the source node, without being tracked and located; the improved secure scheme based on the polynomial of CRC-4 is applied to substitute the RSA digital signature of SAODV and guarantee the data integrity, in addition to reducing the computation and energy consumption; the random delayed transmitting scheme (RDTM is implemented to separate the check code and transmitted data, and achieve tamper-proof results. The simulation results show that the comprehensive performance of the proposed SAL-SAODV is a trade-off of the transmission performance, energy efficiency, and security, and better than AODV and SAODV.

  10. A Source Anonymity-Based Lightweight Secure AODV Protocol for Fog-Based MANET.

    Science.gov (United States)

    Fang, Weidong; Zhang, Wuxiong; Xiao, Jinchao; Yang, Yang; Chen, Wei

    2017-06-17

    Fog-based MANET (Mobile Ad hoc networks) is a novel paradigm of a mobile ad hoc network with the advantages of both mobility and fog computing. Meanwhile, as traditional routing protocol, ad hoc on-demand distance vector (AODV) routing protocol has been applied widely in fog-based MANET. Currently, how to improve the transmission performance and enhance security are the two major aspects in AODV's research field. However, the researches on joint energy efficiency and security seem to be seldom considered. In this paper, we propose a source anonymity-based lightweight secure AODV (SAL-SAODV) routing protocol to meet the above requirements. In SAL-SAODV protocol, source anonymous and secure transmitting schemes are proposed and applied. The scheme involves the following three parts: the source anonymity algorithm is employed to achieve the source node, without being tracked and located; the improved secure scheme based on the polynomial of CRC-4 is applied to substitute the RSA digital signature of SAODV and guarantee the data integrity, in addition to reducing the computation and energy consumption; the random delayed transmitting scheme (RDTM) is implemented to separate the check code and transmitted data, and achieve tamper-proof results. The simulation results show that the comprehensive performance of the proposed SAL-SAODV is a trade-off of the transmission performance, energy efficiency, and security, and better than AODV and SAODV.

  11. The PreViBOSS project: study the short term predictability of the visibility change during the Fog life cycle, from surface and satellite observation

    Science.gov (United States)

    Elias, T.; Haeffelin, M.; Ramon, D.; Gomes, L.; Brunet, F.; Vrac, M.; Yiou, P.; Hello, G.; Petithomme, H.

    2010-07-01

    Fog prejudices major activities as transport and Earth observation, by critically reducing atmospheric visibility with no continuity in time and space. Fog is also an essential factor of air quality and climate as it modifies particle properties of the surface atmospheric layer. Complexity, diversity and the fine scale of processes make uncertain by current numerical weather prediction models, not only visibility diagnosis but also fog event prediction. Extensive measurements of atmospheric parameters are made on the SIRTA since 1997 to document physical processes over the atmospheric column, in the Paris suburb area, typical of an environment intermittently under oceanic influence and affected by urban and industrial pollution. The ParisFog field campaign hosted in SIRTA during 6-month in winter 2006-2007 resulted in the deployment of instrumentation specifically dedicated to study physical processes in the fog life cycle: thermodynamical, radiative, dynamical, microphysical processes. Analysis of the measurements provided a preliminary climatology of the episodes of reduced visibility, chronology of processes was delivered by examining time series of measured parameters and a closure study was performed on optical and microphysical properties of particles (aerosols to droplets) during the life cycle of a radiative fog, providing the relative contribution of several particle groups to extinction in clear-sky conditions, in haze and in fog. PreViBOSS is a 3-year project scheduled to start this year. The aim is to improve the short term prediction of changes in atmospheric visibility, at a local scale. It proposes an innovative approach: applying the Generalised Additive Model statistical method to the detailed and extended dataset acquired at SIRTA. This method offers the opportunity to explore non linear relationships between parameters, which are not yet integrated in current numerical models. Emphasis will be put on aerosols and their impact on the fog life

  12. Summer Arctic sea fog

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Synchronous or quasi-synchronous sea-land-air observations were conducted using advanced sea ice, atmospheric and marine instruments during China' s First Arctic Expedition. Based on the Precious data from the expedition, it was found that in the Arctic Ocean, most part of which is covered with ice or is mixed with ice, various kinds of sea fog formed such as advection fog, radiation fog and vapor fog. Each kind has its own characteristic and mechanics of creation. In the southern part of the Arctic Ocean, due to the sufficient warm and wet flow there, it is favorable for advection fog to form,which is dense and lasts a long time. On ice cap or vast floating ice, due to the strong radiation cooling effect, stable radiating fog is likely to form. In floating ice area there forms vapor fog with the appearance of masses of vapor from a boiling pot, which is different from short-lasting land fog. The study indicates that the reason why there are many kinds of sea fog form in the Arctic Ocean is because of the complicated cushion and the consequent sea-air interaction caused by the sea ice distribution and its unique physical characteristics. Sea fog is the atmospheric phenomenon of sea-air heat exchange. Especially, due to the high albedo of ice and snow surface, it is diffcult to absorb great amount of solar radiation during the polar days. Besides, ice is a poor conductor of heat; it blocks the sea-air heat exchange.The sea-air exchange is active in floating ice area where the ice is broken. The sea sends heat to the atmosphere in form of latent heat; vapor fog is a way of sea-air heat exchange influencing the climate and an indicator of the extent of the exchange. The study also indicates that the sea also transports heat to the atmosphere in form of sensible heat when vapor fog occurs.

  13. FOG Random Drift Signal Denoising Based on the Improved AR Model and Modified Sage-Husa Adaptive Kalman Filter.

    Science.gov (United States)

    Sun, Jin; Xu, Xiaosu; Liu, Yiting; Zhang, Tao; Li, Yao

    2016-07-12

    In order to reduce the influence of fiber optic gyroscope (FOG) random drift error on inertial navigation systems, an improved auto regressive (AR) model is put forward in this paper. First, based on real-time observations at each restart of the gyroscope, the model of FOG random drift can be established online. In the improved AR model, the FOG measured signal is employed instead of the zero mean signals. Then, the modified Sage-Husa adaptive Kalman filter (SHAKF) is introduced, which can directly carry out real-time filtering on the FOG signals. Finally, static and dynamic experiments are done to verify the effectiveness. The filtering results are analyzed with Allan variance. The analysis results show that the improved AR model has high fitting accuracy and strong adaptability, and the minimum fitting accuracy of single noise is 93.2%. Based on the improved AR(3) model, the denoising method of SHAKF is more effective than traditional methods, and its effect is better than 30%. The random drift error of FOG is reduced effectively, and the precision of the FOG is improved.

  14. Application of Fast Dynamic Allan Variance for the Characterization of FOGs-Based Measurement While Drilling

    Science.gov (United States)

    Wang, Lu; Zhang, Chunxi; Gao, Shuang; Wang, Tao; Lin, Tie; Li, Xianmu

    2016-01-01

    The stability of a fiber optic gyroscope (FOG) in measurement while drilling (MWD) could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR) is a sliding version of the Allan variance. It is a practical tool that could represent the non-stationary behavior of the gyroscope signal. Since the normal DAVAR takes too long to deal with long time series, a fast DAVAR algorithm has been developed to accelerate the computation speed. However, both the normal DAVAR algorithm and the fast algorithm become invalid for discontinuous time series. What is worse, the FOG-based MWD underground often keeps working for several days; the gyro data collected aboveground is not only very time-consuming, but also sometimes discontinuous in the timeline. In this article, on the basis of the fast algorithm for DAVAR, we make a further advance in the fast algorithm (improved fast DAVAR) to extend the fast DAVAR to discontinuous time series. The improved fast DAVAR and the normal DAVAR are used to responsively characterize two sets of simulation data. The simulation results show that when the length of the time series is short, the improved fast DAVAR saves 78.93% of calculation time. When the length of the time series is long (6×105 samples), the improved fast DAVAR reduces calculation time by 97.09%. Another set of simulation data with missing data is characterized by the improved fast DAVAR. Its simulation results prove that the improved fast DAVAR could successfully deal with discontinuous data. In the end, a vibration experiment with FOGs-based MWD has been implemented to validate the good performance of the improved fast DAVAR. The results of the experience testify that the improved fast DAVAR not only shortens computation time, but could also analyze discontinuous time series. PMID:27941600

  15. Application of Fast Dynamic Allan Variance for the Characterization of FOGs-Based Measurement While Drilling

    Directory of Open Access Journals (Sweden)

    Lu Wang

    2016-12-01

    Full Text Available The stability of a fiber optic gyroscope (FOG in measurement while drilling (MWD could vary with time because of changing temperature, high vibration, and sudden power failure. The dynamic Allan variance (DAVAR is a sliding version of the Allan variance. It is a practical tool that could represent the non-stationary behavior of the gyroscope signal. Since the normal DAVAR takes too long to deal with long time series, a fast DAVAR algorithm has been developed to accelerate the computation speed. However, both the normal DAVAR algorithm and the fast algorithm become invalid for discontinuous time series. What is worse, the FOG-based MWD underground often keeps working for several days; the gyro data collected aboveground is not only very time-consuming, but also sometimes discontinuous in the timeline. In this article, on the basis of the fast algorithm for DAVAR, we make a further advance in the fast algorithm (improved fast DAVAR to extend the fast DAVAR to discontinuous time series. The improved fast DAVAR and the normal DAVAR are used to responsively characterize two sets of simulation data. The simulation results show that when the length of the time series is short, the improved fast DAVAR saves 78.93% of calculation time. When the length of the time series is long ( 6 × 10 5 samples, the improved fast DAVAR reduces calculation time by 97.09%. Another set of simulation data with missing data is characterized by the improved fast DAVAR. Its simulation results prove that the improved fast DAVAR could successfully deal with discontinuous data. In the end, a vibration experiment with FOGs-based MWD has been implemented to validate the good performance of the improved fast DAVAR. The results of the experience testify that the improved fast DAVAR not only shortens computation time, but could also analyze discontinuous time series.

  16. Analysis of the Interaction and Transport of Aerosols with Cloud or Fog in East Asia from AERONET and Satellite Remote Sensing: 2012 DRAGON Campaigns and Climatological Data

    Science.gov (United States)

    Eck, T. F.; Holben, B. N.; Reid, J. S.; Lynch, P.; Schafer, J.; Giles, D. M.; Kim, J.; Kim, Y. J.; Sano, I.; Arola, A. T.; Munchak, L. A.; O'Neill, N. T.; Lyapustin, A.; Sayer, A. M.; Hsu, N. Y. C.; Randles, C. A.; da Silva, A. M., Jr.; Govindaraju, R.; Hyer, E. J.; Pickering, K. E.; Crawford, J. H.; Sinyuk, A.; Smirnov, A.

    2015-12-01

    Ground-based remote sensing observations from Aerosol Robotic Network (AERONET) sun-sky radiometers have recently shown several instances where cloud-aerosol interaction had resulted in modification of aerosol properties and/or in difficulty identifying some major pollution transport events due to aerosols being imbedded in cloud systems. Major Distributed Regional Aerosol Gridded Observation Networks (DRAGON) field campaigns involving multiple AERONET sites in Japan and South Korea during Spring of 2012 have yielded observations of aerosol transport associated with clouds and/or aerosol properties modification as a result of fog interaction. Analysis of data from the Korean and Japan DRAGON campaigns shows that major fine-mode aerosol transport events are sometimes associated with extensive cloud cover and that cloud-screening of observations often filter out significant pollution aerosol transport events. The Spectral De-convolution Algorithm (SDA) algorithm was utilized to isolate and analyze the fine-mode aerosol optical depth (AODf) signal from AERONET data for these cases of persistent and extensive cloud cover. Satellite retrievals of AOD from MODIS sensors (from Dark Target, Deep Blue and MAIAC algorithms) were also investigated to assess the issue of detectability of high AOD events associated with high cloud fraction. Underestimation of fine mode AOD by the Navy Aerosol Analysis and Prediction System (NAAPS) and by the NASA Modern-Era Retrospective Analysis For Research And Applications Aerosol Re-analysis (MERRAaero) models at very high AOD at sites in China and Korea was observed, especially for observations that are cloud screened by AERONET (Level 2 data). Additionally, multi-year monitoring at several AERONET sites are examined for climatological statistics of cloud screening of fine mode aerosol events. Aerosol that has been affected by clouds or the near-cloud environment may be more prevalent than AERONET data suggest due to inherent difficulty in

  17. A Long-Term Performance Enhancement Method for FOG-Based Measurement While Drilling.

    Science.gov (United States)

    Zhang, Chunxi; Lin, Tie

    2016-07-28

    In the oil industry, the measurement-while-drilling (MWD) systems are usually used to provide the real-time position and orientation of the bottom hole assembly (BHA) during drilling. However, the present MWD systems based on magnetic surveying technology can barely ensure good performance because of magnetic interference phenomena. In this paper, a MWD surveying system based on a fiber optic gyroscope (FOG) was developed to replace the magnetic surveying system. To accommodate the size of the downhole drilling conditions, a new design method is adopted. In order to realize long-term and high position precision and orientation surveying, an integrated surveying algorithm is proposed based on inertial navigation system (INS) and drilling features. In addition, the FOG-based MWD error model is built and the drilling features are analyzed. The state-space system model and the observation updates model of the Kalman filter are built. To validate the availability and utility of the algorithm, the semi-physical simulation is conducted under laboratory conditions. The results comparison with the traditional algorithms show that the errors were suppressed and the measurement precision of the proposed algorithm is better than the traditional ones. In addition, the proposed method uses a lot less time than the zero velocity update (ZUPT) method.

  18. Fog computing

    OpenAIRE

    Poplštein, Karel

    2016-01-01

    The purpose of this bachelor's thesis is to address fog computing technology, that emerged as a possible solution for the internet of things requirements and aims to lower latency and network bandwidth by moving a substantial part of computing operation to the network edge. The thesis identifies advantages as well as potential threats and analyses the possible solutions to these problems, proceeding to comparison of cloud and fog computing and specifying areas of use for both of them. Finally...

  19. A Heavy Sea Fog Event over the Yellow Sea in March 2005:Analysis and Numerical Modeling

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    In this paper, a heavy sea fog episode that occurred over the Yellow Sea on 9 March 2005 is investigated.The sea fog patch, with a spatial scale of several hundred kilometers at its mature stage, reduced visibility along the Shandong Peninsula coast to 100 m or much less at some sites. Satellite images, surface observations and soundings at islands and coasts, and analyses from the Japan Meteorology Agency (JMA) are used to describe and analyze this event. The analysis indicates that this sea fog can be categorized as advection cooling fog. The main features of this sea fog including fog area and its movement are reasonably reproduced by the Fifth-generation Pennsylvania State University/National Center for Atmospheric Research Mesoscale Model (MM5). Model results suggest that the formation and evolution of this event can be outlined as:(1) southerly warm/moist advection of low-level air resulted in a strong sea-surface-based inversion with a thickness of about 600 m; (2) when the inversion moved from the warmer East Sea to the colder Yellow Sea, a thermal internal boundary layer (TIBL) gradually formed at the base of the inversion while the sea fog grew in response to cooling and moistening by turbulence mixing; (3) the sea fog developed as the TIBL moved northward and (4) strong northerly cold and dry wind destroyed the TIBL and dissipated the sea fog. The principal findings of this study are that sea fog forms in response to relatively persistent southerly warm/moist wind and a cold sea surface, and that turbulence mixing by wind shear is the primary mechanism for the cooling and moistening the marine layer. In addition, the study of sensitivity experiments indicates that deterministic numerical modeling offers a promising approach to the prediction of sea fog over the Yellow Sea but it may be more efficient to consider ensemble numerical modeling because of the extreme sensitivity to model input.

  20. Radiative characteristics of fog over the Indo-Gangetic Plains during northern winter

    Science.gov (United States)

    Sathiyamoorthy, V.; Arya, R.; Kishtawal, C. M.

    2016-09-01

    The Indo-Gangetic plains (IGP), spread across northern parts of India, Pakistan and Bangladesh is a hot-spot for fog formation during northern winter. The unavailability of long-term fog data over the IGP from any space based platform incites the utilization of monthly International Satellite Cloud Climatology Project (ISCCP-D2) cloud data for studying fog at this region. Fog is primarily represented as low level stratus and stratocumulus clouds in ISCCP cloud data. Top of atmosphere cloud radiative forcing measured by Clouds and the Earth's Radiant Energy System instruments onboard Aqua/Terra satellites indicates a net radiative cooling by fog over the IGP region. Also, the analysis of gridded surface temperature data from India meteorological department suggests that negative temperature anomalies prevail over the regions of radiative cooling exerted by fog. These negative anomalies in surface temperature may cause further dipping of the temperature over the IGP during fog years. This study suggests that foggy winter will be colder than non-foggy winter over the IGP.

  1. Urbanization causes increased cloud base height and decreased fog in coastal Southern California

    Science.gov (United States)

    Williams, A. Park; Schwartz, Rachel E.; Iacobellis, Sam; Seager, Richard; Cook, Benjamin I.; Still, Christopher J.; Husak, Gregory; Michaelsen, Joel

    2015-03-01

    Subtropical marine stratus clouds regulate coastal and global climate, but future trends in these clouds are uncertain. In coastal Southern California (CSCA), interannual variations in summer stratus cloud occurrence are spatially coherent across 24 airfields and dictated by positive relationships with stability above the marine boundary layer (MBL) and MBL height. Trends, however, have been spatially variable since records began in the mid-1900s due to differences in nighttime warming. Among CSCA airfields, differences in nighttime warming, but not daytime warming, are strongly and positively related to fraction of nearby urban cover, consistent with an urban heat island effect. Nighttime warming raises the near-surface dew point depression, which lifts the altitude of condensation and cloud base height, thereby reducing fog frequency. Continued urban warming, rising cloud base heights, and associated effects on energy and water balance would profoundly impact ecological and human systems in highly populated and ecologically diverse CSCA.

  2. A UAV-Based Fog Collector Design for Fine-Scale Aerobiological Sampling

    Science.gov (United States)

    Gentry, D.; Guarro, M.; Demachkie, I. S.; Stumfall, I.; Dahlgren, R. P.

    2016-12-01

    Airborne microbes are found throughout the troposphere and into the stratosphere. Knowing how the activity of airborne microorganisms can alter water, carbon, and other geochemical cycles is vital to a full understanding of local and global ecosystems. Just as on the land or in the ocean, atmospheric regions vary in habitability; the underlying geochemical, climatic, and ecological dynamics must be characterized at different scales to be effectively modeled. Most aerobiological studies have focused on a high level: 'How high are airborne microbes found?' and 'How far can they travel?' Most fog and cloud water studies collect from stationary ground stations (point) or along flight transects (1D). To complement and provide context for this data, we have designed a UAV-based modified fog and cloud water collector to retrieve 4D-resolved samples for biological and chemical analysis. Our design uses a passive impacting collector hanging from a rigid rod suspended between two multi-rotor UAVs. The suspension design reduces the effect of turbulence and potential for contamination from the UAV downwash. The UAVs are currently modeled in a leader-follower configuration, taking advantage of recent advances in modular UAVs, UAV swarming, and flight planning. The collector itself is a hydrophobic mesh. Materials including Tyvek, PTFE, nylon, and polypropylene monofilament fabricated via laser cutting, CNC knife, or 3D printing were characterized for droplet collection efficiency using a benchtop atomizer and particle counter. Because the meshes can be easily and inexpensively fabricated, a set can be pre-sterilized and brought to the field for 'hot swapping' to decrease cross-contamination between flight sessions or use as negative controls. An onboard sensor and logging system records the time and location of each sample; when combined with flight tracking data, the samples can be resolved into a 4D volumetric map of the fog bank. Collected samples can be returned to the lab

  3. La Jolla Fog Study

    Science.gov (United States)

    Roberts, G. C.; Ramana, M.; Pham, A.; Ramanathan, V.

    2002-12-01

    The Center for Atmospheric Sciences at the Scripps Institution of Oceanography conducted a ground-based experiment to study fog/marine-stratus clouds over the San Diego region during the summer months of 2002. The purpose of the experiment is to understand aerosol/cloud interactions and how they might influence cloud radiative properties and precipitation. We operated several instruments on Mt. Soledad to study aerosol and cloud properties. These instruments include a forward scattering spectrometer probe (FSSP-100) and an aerosol particle sizer (APS) to measure the cloud droplet spectra during fog events, condensation particle counters to determine total aerosol concentrations, cloud condensation nuclei counters to understand aerosol/cloud droplet interactions, a scanning mobility particle sizer (SMPS) to determine dry aerosol number size distributions, and a weather station to relate fog events to local meteorology. Aerosol concentrations showed a diel variation with high and variable particle concentrations during the day, which often were greater than 104 cm-3. Nighttime concentrations were lower (i.e., several thousand cm-3) and exhibited less variation than daytime values. In general, aerosol concentrations do not appear to be correlated to droplet concentrations indicating that local anthropogenic sources may not have a large influence on the coastal fog. Two types of events (haze and fog) have been characterized during this study based on the droplet distribution. A haze event was dominated by droplets less than 5 μm diameter and sometimes exceeded droplet concentrations of 1000 cm-3. There were virtually no particles larger than 5 micron diameter during these events. A fog event was characterized by larger droplets with droplets greater than 5 μm diameter accounting for a bulk of the number concentration. The average effective radius during these fog events was about 5 μm and the droplet concentration rarely exceeded 100 cm-3. On several occasions, a

  4. Brain Fog

    Science.gov (United States)

    ... Elaine Alexander, MD, PhD, clinician and researcher in Sjögren’s syndrome, biomedical consultant and Chair-Elect of the SSF ... fact of life. Brain Fog can occur in Sjögren’s syndrome (SS), but other factors might cause these symptoms and ...

  5. Broad-spectrum monitoring strategies for predicting occult precipitation contribution to water balance in a coastal watershed in California: Ground-truthing, areal monitoring and isotopic analysis of fog in the San Francisco Bay region

    Science.gov (United States)

    Koohafkan, M.; Thompson, S. E.; Leonardson, R.; Dufour, A.

    2013-12-01

    We showcase a fog monitoring study designed to quantitatively estimate the contribution of summer fog events to the water balance of a coastal watershed managed by the San Francisco Public Utilities Commission. Two decades of research now clearly show that fog and occult precipitation can be major contributors to the water balance of watersheds worldwide. Monitoring, understanding and predicting occult precipitation is therefore as hydrologically compelling as forecasting precipitation or evaporation, particularly in the face of climate variability. We combine ground-based monitoring and collection strategies with remote sensing technologies, time-lapse imagery, and isotope analysis to trace the ';signature' of fog in physical and ecological processes. Spatial coverage and duration of fog events in the watershed is monitored using time-lapse cameras and leaf wetness sensors strategically positioned to provide estimates of the fog bank extent and cloud base elevation, and this fine-scale data is used to estimate transpiration suppression by fog and is examined in the context of regional climate through the use of satellite imagery. Soil moisture sensors, throughfall collectors and advective fog collectors deployed throughout the watershed provide quantitative estimates of fog drip contribution to soil moisture and plants. Fog incidence records and streamflow monitoring provide daily estimates of fog contribution to streamflow. Isotope analysis of soil water, fog drip, stream water and vegetation samples are used to probe for evidence of direct root and leaf uptake of fog drip by plants. Using this diversity of fog monitoring methods, we develop an empirical framework for the inclusion of fog processes in water balance models.

  6. Biogeography based Satellite Image Classification

    CERN Document Server

    Panchal, V K; Kaur, Navdeep; Kundra, Harish

    2009-01-01

    Biogeography is the study of the geographical distribution of biological organisms. The mindset of the engineer is that we can learn from nature. Biogeography Based Optimization is a burgeoning nature inspired technique to find the optimal solution of the problem. Satellite image classification is an important task because it is the only way we can know about the land cover map of inaccessible areas. Though satellite images have been classified in past by using various techniques, the researchers are always finding alternative strategies for satellite image classification so that they may be prepared to select the most appropriate technique for the feature extraction task in hand. This paper is focused on classification of the satellite image of a particular land cover using the theory of Biogeography based Optimization. The original BBO algorithm does not have the inbuilt property of clustering which is required during image classification. Hence modifications have been proposed to the original algorithm and...

  7. An Architecture of IoT Service Delegation and Resource Allocation Based on Collaboration between Fog and Cloud Computing

    Directory of Open Access Journals (Sweden)

    Aymen Abdullah Alsaffar

    2016-01-01

    Full Text Available Despite the wide utilization of cloud computing (e.g., services, applications, and resources, some of the services, applications, and smart devices are not able to fully benefit from this attractive cloud computing paradigm due to the following issues: (1 smart devices might be lacking in their capacity (e.g., processing, memory, storage, battery, and resource allocation, (2 they might be lacking in their network resources, and (3 the high network latency to centralized server in cloud might not be efficient for delay-sensitive application, services, and resource allocations requests. Fog computing is promising paradigm that can extend cloud resources to edge of network, solving the abovementioned issue. As a result, in this work, we propose an architecture of IoT service delegation and resource allocation based on collaboration between fog and cloud computing. We provide new algorithm that is decision rules of linearized decision tree based on three conditions (services size, completion time, and VMs capacity for managing and delegating user request in order to balance workload. Moreover, we propose algorithm to allocate resources to meet service level agreement (SLA and quality of services (QoS as well as optimizing big data distribution in fog and cloud computing. Our simulation result shows that our proposed approach can efficiently balance workload, improve resource allocation efficiently, optimize big data distribution, and show better performance than other existing methods.

  8. Sea Fog Forecasting with Lagrangian Models

    Science.gov (United States)

    Lewis, J. M.

    2014-12-01

    In 1913, G. I. Taylor introduced us to a Lagrangian view of sea fog formation. He conducted his study off the coast of Newfoundland in the aftermath of the Titanic disaster. We briefly review Taylor's classic work and then apply these same principles to a case of sea fog formation and dissipation off the coast of California. The resources used in this study consist of: 1) land-based surface and upper-air observations, 2) NDBC (National Data Buoy Center) observations from moored buoys equipped to measure dew point temperature as well as the standard surface observations at sea (wind, sea surface temperature, pressure, and air temperature), 3) satellite observations of cloud, and 4) a one-dimensional (vertically directed) boundary layer model that tracks with the surface air motion and makes use of sophisticated turbulence-radiation parameterizations. Results of the investigation indicate that delicate interplay and interaction between the radiation and turbulence processes makes accurate forecasts of sea fog onset unlikely in the near future. This pessimistic attitude stems from inadequacy of the existing network of observations and uncertainties in modeling dynamical processes within the boundary layer.

  9. A resource-sharing model based on a repeated game in fog computing

    Directory of Open Access Journals (Sweden)

    Yan Sun

    2017-03-01

    Full Text Available With the rapid development of cloud computing techniques, the number of users is undergoing exponential growth. It is difficult for traditional data centers to perform many tasks in real time because of the limited bandwidth of resources. The concept of fog computing is proposed to support traditional cloud computing and to provide cloud services. In fog computing, the resource pool is composed of sporadic distributed resources that are more flexible and movable than a traditional data center. In this paper, we propose a fog computing structure and present a crowd-funding algorithm to integrate spare resources in the network. Furthermore, to encourage more resource owners to share their resources with the resource pool and to supervise the resource supporters as they actively perform their tasks, we propose an incentive mechanism in our algorithm. Simulation results show that our proposed incentive mechanism can effectively reduce the SLA violation rate and accelerate the completion of tasks.

  10. A resource-sharing model based on a repeated game in fog computing.

    Science.gov (United States)

    Sun, Yan; Zhang, Nan

    2017-03-01

    With the rapid development of cloud computing techniques, the number of users is undergoing exponential growth. It is difficult for traditional data centers to perform many tasks in real time because of the limited bandwidth of resources. The concept of fog computing is proposed to support traditional cloud computing and to provide cloud services. In fog computing, the resource pool is composed of sporadic distributed resources that are more flexible and movable than a traditional data center. In this paper, we propose a fog computing structure and present a crowd-funding algorithm to integrate spare resources in the network. Furthermore, to encourage more resource owners to share their resources with the resource pool and to supervise the resource supporters as they actively perform their tasks, we propose an incentive mechanism in our algorithm. Simulation results show that our proposed incentive mechanism can effectively reduce the SLA violation rate and accelerate the completion of tasks.

  11. Fog characteristics at the airport of Thessaloniki, Greece

    Directory of Open Access Journals (Sweden)

    S. N. Stolaki

    2009-09-01

    Full Text Available A statistical approach in order to study fog event characteristics occuring at the airport of Thessaloniki, Northern Greece is presented in this work. To achieve this, the seasonal and diurnal characteristics of fog are investigated using 35 years (1971–2005 of observations of meteorological parameters such as: visibility, air temperature, dew point temperature, air relative humidity, wind vector, precipitation, and cloud base height and coverage. Hourly surface observations of fifteen (15 years (1991–2005 are used to identify fog events induced by various physical mechanisms. Fog events are classified into fog types through the application of objective criteria that are derived upon fog formation processes and under the influence of various physiographic features. The temporal variability of different fog type occurrences are examined and the events are characterized according to their duration and intensity.

    The results are somehow affected by regional and local factors. Fog is mainly formed in winter time (~64% with an enhanced likelihood to appear also in late autumn (19%. The highest frequency of the fog events occurs around sunrise or 1 to 2 h before of it. The mean duration of the events is about 4.5 h. Most of them (75% are dense (visibility <400 m. The overall fog phenomenon is a combination of various types, such as: advection fog, radiation fog, cloud-base lowering fog and precipitation fog. Advection fog (30% and radiation fog (29%, which are the most common types, occur predominantly in winter and early spring time. With respect to the former type, it seems that, in many cases, already formed fog is advected from the nearby Anthemountas valley. Moreover, a considerable number of fog events (22% result from cloud-base lowering, and they frequently occur in late autumn and mid winter.

  12. Development and validation of satellite based estimates of surface visibility

    Science.gov (United States)

    Brunner, J.; Pierce, R. B.; Lenzen, A.

    2015-10-01

    A satellite based surface visibility retrieval has been developed using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements as a proxy for Advanced Baseline Imager (ABI) data from the next generation of Geostationary Operational Environmental Satellites (GOES-R). The retrieval uses a multiple linear regression approach to relate satellite aerosol optical depth, fog/low cloud probability and thickness retrievals, and meteorological variables from numerical weather prediction forecasts to National Weather Service Automated Surface Observing System (ASOS) surface visibility measurements. Validation using independent ASOS measurements shows that the GOES-R ABI surface visibility retrieval (V) has an overall success rate of 64.5% for classifying Clear (V ≥ 30 km), Moderate (10 km ≤ V skill during June through September, when Heidke skill scores are between 0.2 and 0.4. We demonstrate that the aerosol (clear sky) component of the GOES-R ABI visibility retrieval can be used to augment measurements from the United States Environmental Protection Agency (EPA) and National Park Service (NPS) Interagency Monitoring of Protected Visual Environments (IMPROVE) network, and provide useful information to the regional planning offices responsible for developing mitigation strategies required under the EPA's Regional Haze Rule, particularly during regional haze events associated with smoke from wildfires.

  13. Computer based satellite design

    Science.gov (United States)

    Lashbrook, David D.

    1992-06-01

    A computer program to design geosynchronous spacecraft has been developed. The program consists of four separate but interrelated executable computer programs. The programs are compiled to run on a DOS based personnel computer. The source code is written in DoD mandated Ada programming language. The thesis presents the design technique and design equations used in the program. Detailed analysis is performed in the following areas for both dual spin and three axis stabilized spacecraft configurations: (1) Mass Propellent Budget and Mass Summary; (2) Battery Cell and Solar Cell Requirements for a Payload Power Requirement; and (3) Passive Thermal Control Requirements. A user's manual is included as Appendix A, and the source code for the computer programs as Appendix B.

  14. Satellite-Based Quantum Communications

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Richard J [Los Alamos National Laboratory; Nordholt, Jane E [Los Alamos National Laboratory; McCabe, Kevin P [Los Alamos National Laboratory; Newell, Raymond T [Los Alamos National Laboratory; Peterson, Charles G [Los Alamos National Laboratory

    2010-09-20

    Single-photon quantum communications (QC) offers the attractive feature of 'future proof', forward security rooted in the laws of quantum physics. Ground based quantum key distribution (QKD) experiments in optical fiber have attained transmission ranges in excess of 200km, but for larger distances we proposed a methodology for satellite-based QC. Over the past decade we have devised solutions to the technical challenges to satellite-to-ground QC, and we now have a clear concept for how space-based QC could be performed and potentially utilized within a trusted QKD network architecture. Functioning as a trusted QKD node, a QC satellite ('QC-sat') could deliver secret keys to the key stores of ground-based trusted QKD network nodes, to each of which multiple users are connected by optical fiber or free-space QC. A QC-sat could thereby extend quantum-secured connectivity to geographically disjoint domains, separated by continental or inter-continental distances. In this paper we describe our system concept that makes QC feasible with low-earth orbit (LEO) QC-sats (200-km-2,000-km altitude orbits), and the results of link modeling of expected performance. Using the architecture that we have developed, LEO satellite-to-ground QKD will be feasible with secret bit yields of several hundred 256-bit AES keys per contact. With multiple ground sites separated by {approx} 100km, mitigation of cloudiness over any single ground site would be possible, potentially allowing multiple contact opportunities each day. The essential next step is an experimental QC-sat. A number of LEO-platforms would be suitable, ranging from a dedicated, three-axis stabilized small satellite, to a secondary experiment on an imaging satellite. to the ISS. With one or more QC-sats, low-latency quantum-secured communications could then be provided to ground-based users on a global scale. Air-to-ground QC would also be possible.

  15. About Security Solutions in Fog Computing

    Directory of Open Access Journals (Sweden)

    Eugen Petac

    2016-01-01

    Full Text Available The key for improving a system's performance, its security and reliability is to have the dataprocessed locally in remote data centers. Fog computing extends cloud computing through itsservices to devices and users at the edge of the network. Through this paper it is explored the fogcomputing environment. Security issues in this area are also described. Fog computing providesthe improved quality of services to the user by complementing shortages of cloud in IoT (Internet ofThings environment. Our proposal, named Adaptive Fog Computing Node Security Profile(AFCNSP, which is based security Linux solutions, will get an improved security of fog node withrich feature sets.

  16. 14 CFR 141.91 - Satellite bases.

    Science.gov (United States)

    2010-01-01

    ... 14 Aeronautics and Space 3 2010-01-01 2010-01-01 false Satellite bases. 141.91 Section 141.91... OTHER CERTIFICATED AGENCIES PILOT SCHOOLS Operating Rules § 141.91 Satellite bases. The holder of a... assistant chief instructor is designated for each satellite base, and that assistant chief instructor...

  17. Image to Fog Research Based on the Wavelet Noisereduction Measures%基于小波降噪度量的图像去雾研究

    Institute of Scientific and Technical Information of China (English)

    黄凤

    2016-01-01

    Proposed image to fog method based on wavelet noise reduction measure ,by determining threshold value to achieve the aim of fog image wavelet noise reduction ,image data information after the noise of background and target image segmentation ,wavelet hierarchy to fog calculation ,according to the different level objects to fog calculation according to the layer classification o f the important level ,finally through the local and the overall texture details relevance computing will fog image restoration ,completing the process of image to fog . Through the simulation experiment of image to fog algorithm based on wavelet measure reduction test ,from the effect of noise reduction ,to the time and speed of image to fog fog three aspects has carried on the comparison ,the algorithm is superior to the traditional method ,prove the effectiveness of the algorithm ,and has more extensive application value .%提出基于小波降噪度量的图像去雾方法,通过确定阈值来达到对浓雾图像小波降噪目的,对降噪后的图像数据信息进行背景和目标图像的分割,进行 Harr的小波层级去雾计算,按照不同级别物体按重要级别分层级进行去雾计算,最后通过局部细节和整体纹理关联计算将浓雾图像还原,完成图像的去雾过程。通过仿真实验对基于小波降度量的图像去雾算法进行测试,从降噪效果、去雾时间和图像去雾速度三个方面进行了比较,该算法均优于传统方法,证明了该算法的有效性,并且具有比较广泛的应用价值。

  18. Optimization of strawberry disinfection by fogging of a mixture of peracetic acid and hydrogen peroxide based on microbial reduction, color and phytochemicals retention.

    Science.gov (United States)

    Van de Velde, Franco; Vaccari, María Celia; Piagentini, Andrea Marcela; Pirovani, María Élida

    2016-09-01

    The fogging of strawberries using a environmentally friendly sanitizer mixture of peracetic acid (5%) and hydrogen peroxide (20%) was performed in a model chamber and modeled as a function of the concentration (3.4, 20.0, 60.0, 100.0 and 116.6 µL sanitizer L(-) (1) air chamber) and the treatment time (5.7, 15.0, 37.5, 60.0 and 69.3 min). The sanitizer fogging was adequate for reducing total mesophilic microbial and yeasts and moulds counts of fruits until seven days of storage at 2℃. However, sanitizer oxidant properties adversely affected the content of total anthocyanins, total phenolics, vitamin C, and antioxidant capacity to various degrees, with some deleterious changes in the fruits color, depending on the fogging conditions. A multiple numeric response optimization was developed based on 2.0 log microbiological reduction, maximum phytochemicals and antioxidant capacity retentions, with no changes in the fruits color, being the optimal fogging conditions achieved: 10.1 µL sanitizer L(-1) air chamber and 29.6 min. The fogging of strawberries at these conditions may represent a promising postharvest treatment option for extending their shelf-life without affecting their sensory quality and bioactive properties.

  19. Cross stratum resources protection in fog-computing-based radio over fiber networks for 5G services

    Science.gov (United States)

    Guo, Shaoyong; Shao, Sujie; Wang, Yao; Yang, Hui

    2017-09-01

    In order to meet the requirement of internet of things (IoT) and 5G, the cloud radio access network is a paradigm which converges all base stations computational resources into a cloud baseband unit (BBU) pool, while the distributed radio frequency signals are collected by remote radio head (RRH). A precondition for centralized processing in the BBU pool is an interconnection fronthaul network with high capacity and low delay. However, it has become more complex and frequent in the interaction between RRH and BBU and resource scheduling among BBUs in cloud. Cloud radio over fiber network has been proposed in our previous work already. In order to overcome the complexity and latency, in this paper, we first present a novel cross stratum resources protection (CSRP) architecture in fog-computing-based radio over fiber networks (F-RoFN) for 5G services. Additionally, a cross stratum protection (CSP) scheme considering the network survivability is introduced in the proposed architecture. The CSRP with CSP scheme can effectively pull the remote processing resource locally to implement the cooperative radio resource management, enhance the responsiveness and resilience to the dynamic end-to-end 5G service demands, and globally optimize optical network, wireless and fog resources. The feasibility and efficiency of the proposed architecture with CSP scheme are verified on our software defined networking testbed in terms of service latency, transmission success rate, resource occupation rate and blocking probability.

  20. Network Intelligence Based on Network State Information for Connected Vehicles Utilizing Fog Computing

    Directory of Open Access Journals (Sweden)

    Seongjin Park

    2017-01-01

    Full Text Available This paper proposes a method to take advantage of fog computing and SDN in the connected vehicle environment, where communication channels are unstable and the topology changes frequently. A controller knows the current state of the network by maintaining the most recent network topology. Of all the information collected by the controller in the mobile environment, node mobility information is particularly important. Thus, we divide nodes into three classes according to their mobility types and use their related attributes to efficiently manage the mobile connections. Our approach utilizes mobility information to reduce control message overhead by adjusting the period of beacon messages and to support efficient failure recovery. One is to recover the connection failures using only mobility information, and the other is to suggest a real-time scheduling algorithm to recover the services for the vehicles that lost connection in the case of a fog server failure. A real-time scheduling method is first described and then evaluated. The results show that our scheme is effective in the connected vehicle environment. We then demonstrate the reduction of control overhead and the connection recovery by using a network simulator. The simulation results show that control message overhead and failure recovery time are decreased by approximately 55% and 5%, respectively.

  1. Novel method for fog monitoring using cellular networks infrastructures

    Science.gov (United States)

    David, N.; Alpert, P.; Messer, H.

    2012-08-01

    A major detrimental effect of fog is visibility limitation which can result in serious transportation accidents, traffic delays and therefore economic damage. Existing monitoring techniques including satellites, transmissometers and human observers - suffer from low spatial resolution, high cost or lack of precision when measuring near ground level. Here we show a novel technique for fog monitoring using wireless communication systems. Communication networks widely deploy commercial microwave links across the terrain at ground level. Operating at frequencies of tens of GHz they are affected by fog and are, effectively, an existing, spatially world-wide distributed sensor network that can provide crucial information about fog concentration and visibility. Fog monitoring potential is demonstrated for a heavy fog event that took place in Israel. The correlation between transmissomters and human eye observations to the visibility estimates from the nearby microwave links was found to be 0.53 and 0.61, respectively. These values indicate the high potential of the proposed method.

  2. 雾天条件下的多尺度Retinex图像增强算法%Enhance Algorithm for Fog Images Based on Improved Multi-scale Retinex

    Institute of Scientific and Technical Information of China (English)

    李菊霞; 余雪丽

    2013-01-01

    When images are shot in fog circumstances, the color and contrast of fog images appear degrade phenomenon. In order to improve the quality of fog image, this paper proposed a fog image enhancement method based on improved multi-scale Retinex algorithm. Firstly, the dynamic range of image was compressed by the power transform, and then nonlinear transform was used to suppress the high light area of image, finally the unsharp mask filtering was used to e-liminate fuzzy to enhance the detail information of fog image,and a few fog images were used to test the performance of the proposed algorithms. The simulation results show that the proposed algorithm solves the shortcomings of traditional Retinex algorithms,accelerates the speed of fog image enhancement,and the fog image is more clearly, so it can obtain better visual effect.%在雾天条件下拍摄图像时,由于受到大气散射作用的影响,图像的颜色和对比度会出现退化现象.为了提高雾天图像的质量,提出一种改进的多尺度Retine雾天图像增强算法.首先采用幂次变换压缩图像动态范围;然后采用非线性变换对图像的高光区域进行抑制;最后采用反锐化掩模滤波消除图像模糊,增强雾天图像细节信息,并采用多幅雾天图像对算法性能进行仿真测试.仿真结果表明,改进多尺度Retine的雾天图像增强算法较好地解决了传统Retine算法存在的不足,加快了雾天图像增强的运行速度,使得雾天图像更加清晰化,获得了更优的视觉效果.

  3. The Association Between Fog and Temperature Inversions from Ground and Radiosonde Observations in East Greenland

    Science.gov (United States)

    Gilson, G.; Jiskoot, H.

    2016-12-01

    Many Arctic glaciers terminate along coasts where temperature inversions and sea fog are frequent during summer. Both can influence glacier ablation, but the effects of fog may be complex. To understand fog's physical and radiative properties and its association to temperature inversions it is important to determine accurate Arctic coastal fog climatologies In previous research we determined that fog in East Greenland peaks in the melt season and can be spatially extensive over glacierized terrain. In this study we aim to understand which environmental factors influence fog occurrence in East Greenland; understand the association between fog and temperature inversions; and quantify fog height. We analyzed fog observations and other weather data from coastal synoptic weather stations, and extracted temperature inversions from the Integrated Global Radiosonde Archive radiosonde profiles. Fog height was calculated from radiosonde profiles, based on a method developed for radiation fog which we expanded to include advection and steam fog. Our results show that Arctic coastal fog requires sea ice breakup and a sea breeze with wind speed between 1-4 m/s. Fog is mostly advective, occurring under stable synoptic conditions characterized by deep and strong low-level temperature inversions. Steam fog may occur 5-30% of the time. Fog can occur under near-surface subsidence, with a subsaturated inversion base, or a saturated inversion base. We classified five types of fog based on their vertical sounding characteristics: only at the surface, below an inversion, capped by an inversion, inside a surface-based inversion, or inside a low-level inversion. Fog is commonly 100-400 m thick, often reaching the top of the boundary layer. Fog height is greater at northern stations, where daily fog duration is longer and relative humidity lower. Our results will be included in glacier energy-balance models to account for the influence of fog and temperature inversions on glacier melt.

  4. Satellite-Based Sunshine Duration for Europe

    Directory of Open Access Journals (Sweden)

    Bodo Ahrens

    2013-06-01

    Full Text Available In this study, two different methods were applied to derive daily and monthly sunshine duration based on high-resolution satellite products provided by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT Satellite Application Facility on Climate Monitoring using data from Meteosat Second Generation (MSG SEVIRI (Spinning Enhanced Visible and Infrared Imager. The satellite products were either hourly cloud type or hourly surface incoming direct radiation. The satellite sunshine duration estimates were not found to be significantly different using the native 15-minute temporal resolution of SEVIRI. The satellite-based sunshine duration products give additional spatial information over the European continent compared with equivalent in situ-based products. An evaluation of the satellite sunshine duration by product intercomparison and against station measurements was carried out to determine their accuracy. The satellite data were found to be within ±1 h/day compared to high-quality Baseline Surface Radiation Network or surface synoptic observations (SYNOP station measurements. The satellite-based products differ more over the oceans than over land, mainly because of the treatment of fractional clouds in the cloud type-based sunshine duration product. This paper presents the methods used to derive the satellite sunshine duration products and the performance of the different retrievals. The main benefits and disadvantages compared to station-based products are also discussed.

  5. Characterization of multilayer anti-fog coatings.

    Science.gov (United States)

    Chevallier, Pascale; Turgeon, Stéphane; Sarra-Bournet, Christian; Turcotte, Raphaël; Laroche, Gaétan

    2011-03-01

    Fog formation on transparent substrates constitutes a major challenge in several optical applications requiring excellent light transmission characteristics. Anti-fog coatings are hydrophilic, enabling water to spread uniformly on the surface rather than form dispersed droplets. Despite the development of several anti-fog coating strategies, the long-term stability, adherence to the underlying substrate, and resistance to cleaning procedures are not yet optimal. We report on a polymer-based anti-fog coating covalently grafted onto glass surfaces by means of a multistep process. Glass substrates were first activated by plasma functionalization to provide amino groups on the surface, resulting in the subsequent covalent bonding of the polymeric layers. The anti-fog coating was then created by the successive spin coating of (poly(ethylene-maleic anhydride) (PEMA) and poly(vinyl alcohol) (PVA) layers. PEMA acted as an interface by covalently reacting with both the glass surface amino functionalities and the PVA hydroxyl groups, while PVA added the necessary surface hydrophilicity to provide anti-fog properties. Each step of the procedure was monitored by XPS, which confirmed the successful grafting of the coating. Coating thickness was evaluated by profilometry, nanoindentation, and UV visible light transmission. The hydrophilic nature of the anti-fog coating was assessed by water contact angle (CA), and its anti-fog efficiency was determined visually and tested quantitatively for the first time using an ASTM standard protocol. Results show that the PEMA/PVA coating not only delayed the initial period required for fog formation but also decreased the rate of light transmission decay. Finally, following a 24 hour immersion in water, these PEMA/PVA coatings remained stable and preserved their anti-fog properties.

  6. Optical Thickness and Effective Radius Retrievals of Low Stratus and Fog from MTSAT Daytime Data as a Prerequisite for Yellow Sea Fog Detection

    Directory of Open Access Journals (Sweden)

    Li Yi

    2015-12-01

    Full Text Available Operational nowcasting techniques for sea fog over the Yellow Sea rely on data from weather satellites because ground-based observations are hardly available. While there are several algorithms for detecting low stratus (LST that are applicable to geostationary weather satellite data, sea fog retrieval is more complicated. These schemes mostly need ancillary data such as Cloud Optical Thickness (COT and Droplet Effective Radius (DER. To retrieve the necessary parameters for sea fog detection over the Yellow Sea, the Comprehensive Analysis Program for Cloud Optical Measurement (CAPCOM scheme developed by Kawamoto et al. (2001 was adapted to the Japanese Multifunctional Transport Satellites (MTSAT system-Japanese Advanced Meteorological Imager (JAMI. COT and DER values were then retrieved for 64 cases over the Yellow Sea (= 85,000 LST pixels and compared with the COT and DER products from the MYD06/MOD06, CAPCOM-MODIS (Moderate Resolution Imaging Spectroradiometer and CloudSat (cloud radar. Results showed that the COT and DER values retrieved from JAMI were satisfactory. The MTSAT-2 JAMI data delivered better COT values than the MTSAT-1R JAMI data, due to the re-calibration of MTSAT-2 JAMI’s visible (VIS band in 2011. Similarly, improvements were seen in DER retrieval, even though the VIS re-calibration primarily affects COT retrieval. By comparing the difference in stratus thickness calculated by MTSAT-1R and MTSAT-2, the COT and DER retrieved from MTSAT-2 JAMI can be used in ground fog retrieval schemes. These values exhibit less bias, especially in cases involving high cloud top and thin cloud thickness. Both the COT and DER retrievals from MTSAT-2 JAMI offer potential as reliable parameters for Yellow Sea fog detection.

  7. Study on an Air Quality Evaluation Model for Beijing City Under Haze-Fog Pollution Based on New Ambient Air Quality Standards

    Science.gov (United States)

    Li, Li; Liu, Dong-Jun

    2014-01-01

    Since 2012, China has been facing haze-fog weather conditions, and haze-fog pollution and PM2.5 have become hot topics. It is very necessary to evaluate and analyze the ecological status of the air environment of China, which is of great significance for environmental protection measures. In this study the current situation of haze-fog pollution in China was analyzed first, and the new Ambient Air Quality Standards were introduced. For the issue of air quality evaluation, a comprehensive evaluation model based on an entropy weighting method and nearest neighbor method was developed. The entropy weighting method was used to determine the weights of indicators, and the nearest neighbor method was utilized to evaluate the air quality levels. Then the comprehensive evaluation model was applied into the practical evaluation problems of air quality in Beijing to analyze the haze-fog pollution. Two simulation experiments were implemented in this study. One experiment included the indicator of PM2.5 and was carried out based on the new Ambient Air Quality Standards (GB 3095-2012); the other experiment excluded PM2.5 and was carried out based on the old Ambient Air Quality Standards (GB 3095-1996). Their results were compared, and the simulation results showed that PM2.5 was an important indicator for air quality and the evaluation results of the new Air Quality Standards were more scientific than the old ones. The haze-fog pollution situation in Beijing City was also analyzed based on these results, and the corresponding management measures were suggested. PMID:25170682

  8. Study on an air quality evaluation model for Beijing City under haze-fog pollution based on new ambient air quality standards.

    Science.gov (United States)

    Li, Li; Liu, Dong-Jun

    2014-08-28

    Since 2012, China has been facing haze-fog weather conditions, and haze-fog pollution and PM2.5 have become hot topics. It is very necessary to evaluate and analyze the ecological status of the air environment of China, which is of great significance for environmental protection measures. In this study the current situation of haze-fog pollution in China was analyzed first, and the new Ambient Air Quality Standards were introduced. For the issue of air quality evaluation, a comprehensive evaluation model based on an entropy weighting method and nearest neighbor method was developed. The entropy weighting method was used to determine the weights of indicators, and the nearest neighbor method was utilized to evaluate the air quality levels. Then the comprehensive evaluation model was applied into the practical evaluation problems of air quality in Beijing to analyze the haze-fog pollution. Two simulation experiments were implemented in this study. One experiment included the indicator of PM2.5 and was carried out based on the new Ambient Air Quality Standards (GB 3095-2012); the other experiment excluded PM2.5 and was carried out based on the old Ambient Air Quality Standards (GB 3095-1996). Their results were compared, and the simulation results showed that PM2.5 was an important indicator for air quality and the evaluation results of the new Air Quality Standards were more scientific than the old ones. The haze-fog pollution situation in Beijing City was also analyzed based on these results, and the corresponding management measures were suggested.

  9. Retrieving fog liquid water content using a new 94 GHz FMCW cloud radar

    Science.gov (United States)

    Maier, F.; Thies, B.; Bendix, J.

    2010-07-01

    The vertical distribution of the liquid water content (LWC) in fog and low stratus is a critical microphysical parameter since it essentially influences the interaction between these low level clouds and the solar and terrestrial radiation. Despite of this importance there are only few investigations concerning LWC-profiles during fog events, which are mainly restricted to balloon borne measurements and suffer from a low temporal resolution. Therefore, no continuous records covering the whole life cycle of fog events can be provided for climatology studies. A new ground based frequency modulated continuous wave (FMCW) cloud radar has the po-tential to fill this lack of knowledge. Working at a frequency of 94 GHz (wavelength 3 mm) it is ideal for monitoring low level water clouds. The radar can detect clouds at a minimum height range of ~30 m and provides a vertical resolution of 4m: This offers the potential to retrieve detailed vertical structures of fog and low stratus. The reconstruction of the LWC-profile can be accomplished due to the close relationship be-tween the cloud LWC and the detected radar reflectivity. However, this relationship depends strongly on the drop size distribution within the cloud. The strength of the radar reflectivity is related to the sixth power of the drop size distribution and the LWC is related to the latter by the third power. Former studies yielded the existence of different fog evolutionary stages with characteristical drop size distributions. In order to explore the effect of the different drop size distribution on the relationship between the radar reflectivity and the LWC we conducted radiative transfer calculations with characteristical drop size distributions and LWC-profiles taken from the literature. For this purpose we adapted the radiative transfer model (RTM) QuickBeam developed for the Cloudsat satellite to our ground based microwave radar. Beside the adaptation to the verti-cal resolution of the ground based cloud

  10. Referenceless Prediction of Perceptual Fog Density and Perceptual Image Defogging.

    Science.gov (United States)

    Choi, Lark Kwon; You, Jaehee; Bovik, Alan Conrad

    2015-11-01

    We propose a referenceless perceptual fog density prediction model based on natural scene statistics (NSS) and fog aware statistical features. The proposed model, called Fog Aware Density Evaluator (FADE), predicts the visibility of a foggy scene from a single image without reference to a corresponding fog-free image, without dependence on salient objects in a scene, without side geographical camera information, without estimating a depth-dependent transmission map, and without training on human-rated judgments. FADE only makes use of measurable deviations from statistical regularities observed in natural foggy and fog-free images. Fog aware statistical features that define the perceptual fog density index derive from a space domain NSS model and the observed characteristics of foggy images. FADE not only predicts perceptual fog density for the entire image, but also provides a local fog density index for each patch. The predicted fog density using FADE correlates well with human judgments of fog density taken in a subjective study on a large foggy image database. As applications, FADE not only accurately assesses the performance of defogging algorithms designed to enhance the visibility of foggy images, but also is well suited for image defogging. A new FADE-based referenceless perceptual image defogging, dubbed DEnsity of Fog Assessment-based DEfogger (DEFADE) achieves better results for darker, denser foggy images as well as on standard foggy images than the state of the art defogging methods. A software release of FADE and DEFADE is available online for public use: http://live.ece.utexas.edu/research/fog/index.html.

  11. An Image Defogging Algorithm Based on the Fog Veil Theory%基于雾气遮罩理论的图像去雾算法

    Institute of Scientific and Technical Information of China (English)

    谢斌; 郭璠; 蔡自兴

    2012-01-01

    针对场景中雾气分布可能不均匀的问题,本文提出了一种基于雾气遮罩减除的图像去雾算法.首先对降质图像平滑滤波以估计其亮度分量,对亮度分量求均值得到均匀分布的雾气遮罩,并结合退化图像获取与场景深度信息相关的雾气遮罩.在对数域中从降质图像中减除获得的雾气遮罩,即可得到场景的反射图像.对反射图像进行自适应的对比度拉伸,可以得到最终的去雾结果.所提算法能较容易地扩展至视频去雾应用,真实场景的图片与视频实验验证了所提算法的有效性.%A new image defog algorithm based on fog veil subtraction is proposed to deal with the situation where the fog might not be uniformly distributed. The proposed algorithm first estimates the illumination component of the image by applying smoothing to the degraded image, and then obtains the uniform distributed fog veil through a mean calculation of the illumination component. Next, we multiply the uniform veil by the original image to obtain a depth-like map and extract its intensity component to produce a fog veil whose distribution is in accord with the real fog density of the scene. Once the fog veil is calculated, the reflectance map can be obtained by subtracting the veil from the degraded image. Finally, we apply an adaptive contrast stretching to the reflectance map to obtain an enhanced result. This algorithm can easily be extended to video domains and is verified by both real-scene photographs and videos.

  12. An analysis of fog events at Belgrade International Airport

    Science.gov (United States)

    Veljović, Katarina; Vujović, Dragana; Lazić, Lazar; Vučković, Vladan

    2015-01-01

    A preliminary study of the occurrence of fog at Belgrade "Nikola Tesla" Airport was carried out using a statistical approach. The highest frequency of fog has occurred in the winter months of December and January and far exceeded the number of fog days in the spring and the beginning of autumn. The exceptionally foggy months, those having an extreme number of foggy days, occurred in January 1989 (18 days), December 1998 (18 days), February 2005 (17 days) and October 2001 (15 days). During the winter months (December, January and February) from 1990 to 2005 (16 years), fog occurred most frequently between 0600 and 1000 hours, and in the autumn, between 0500 and 0800 hours. In summer, fog occurred most frequently between 0300 and 0600 hours. During the 11-year period from 1995 to 2005, it was found that there was a 13 % chance for fog to occur on two consecutive days and a 5 % chance that it would occur 3 days in a row. In October 2001, the fog was observed over nine consecutive days. During the winter half year, 52.3 % of fog events observed at 0700 hours were in the presence of stratus clouds and 41.4 % were without the presence of low clouds. The 6-h cooling observed at the surface preceding the occurrence of fog between 0000 and 0700 hours ranged mainly from 1 to 4 °C. A new method was applied to assess the probability of fog occurrence based on complex fog criteria. It was found that the highest probability of fog occurrence (51.2 %) takes place in the cases in which the relative humidity is above 97 %, the dew-point depression is 0 °C, the cloud base is lower than 50 m and the wind is calm or weak 1 h before the onset of fog.

  13. Advancing satellite-based solar power forecasting through integration of infrared channels for automatic detection of coastal marine inversion layer

    Energy Technology Data Exchange (ETDEWEB)

    Kostylev, Vladimir; Kostylev, Andrey; Carter, Chris; Mahoney, Chad; Pavlovski, Alexandre; Daye, Tony [Green Power Labs Inc., Dartmouth, NS (Canada); Cormier, Dallas Eugene; Fotland, Lena [San Diego Gas and Electric Co., San Diego, CA (United States)

    2012-07-01

    The marine atmospheric boundary layer is a layer or cool, moist maritime air with the thickness of a few thousand feet immediately below a temperature inversion. In coastal areas as moist air rises from the ocean surface, it becomes trapped and is often compressed into fog above which a layer of stratus clouds often forms. This phenomenon is common for satellite-based solar radiation monitoring and forecasting. Hour ahead satellite-based solar radiation forecasts are commonly using visible spectrum satellite images, from which it is difficult to automatically differentiate low stratus clouds and fog from high altitude clouds. This provides a challenge for cloud motion tyracking and cloud cover forecasting. San Diego Gas and Electric {sup registered} (SDG and E {sup registered}) Marine Layer Project was undertaken to obtain information for integration with PV forecasts, and to develop a detailed understanding of long-term benefits from forecasting Marine Layer (ML) events and their effects on PV production. In order to establish climatological ML patterns, spatial extent and distribution of marine layer, we analyzed visible and IR spectrum satellite images (GOES WEST) archive for the period of eleven years (2000 - 2010). Historical boundaries of marine layers impact were established based on the cross-classification of visible spectrum (VIS) and infrared (IR) images. This approach is successfully used by us and elsewhere for evaluating cloud albedo in common satellite-based techniques for solar radiation monitoring and forecasting. The approach allows differentiation of cloud cover and helps distinguish low laying fog which is the main consequence of marine layer formation. ML occurrence probability and maximum extent inland was established for each hour and day of the analyzed period and seasonal/patterns were described. SDG and E service area is the most affected region by ML events with highest extent and probability of ML occurrence. Influence of ML was the

  14. MODELLING AND SIMULATION OF FOG SYSTEM BASED ON MATLAB/SIMULINK%基于Matlab/Simulink的光纤陀螺系统建模与仿真

    Institute of Scientific and Technical Information of China (English)

    于中权; 赵海涛; 梁仁仁; 张华; 吴大庆

    2013-01-01

    In order to accurately understand the working process of fibre optic gyroscope (FOG),the modelling and simulative analysis on digital closed-loop FOG is carried out with Matlab-based Simulink software.The focus of the analysis puts on the influence of half-wave voltage fluctuation on the accuracy of gyroscopes,where the fluctuation is caused by Y waveguide which is a key component of FOG.Simulation results shows that the simulation model can timely track the modulation gain drift and compensate it.%为了准确理解光纤陀螺的工作过程,基于Matlab的Simulink软件对数字闭环光纤陀螺进行建模和仿真分析,重点分析光纤陀螺的关键器件Y波导的半波电压波动对陀螺精度的影响.仿真结果表明,仿真模型能够对调制增益漂移进行实时跟踪和补偿.

  15. Modeling Radiation Fog

    Science.gov (United States)

    K R, Sreenivas; Mohammad, Rafiuddin

    2016-11-01

    Predicting the fog-onset, its growth and dissipation helps in managing airports and other modes of transport. After sunset, occurrence of fog requires moist air, low wind and clear-sky conditions. Under these circumstances radiative heat transfer plays a vital role in the NBL. Locally, initiation of fog happens when the air temperature falls below the dew-point. Thus, to predict the onset of fog at a given location, one has to compute evolution of vertical temperature profile. Earlier,our group has shown that the presence of aerosols and vertical variation in their number density determines the radiative-cooling and hence development of vertical temperature profile. Aerosols, through radiation in the window-band, provides an efficient path for air layers to lose heat to the cold, upper atmosphere. This process creates cooler air layer between warmer ground and upper air layers and resulting temperature profile facilitate the initiation of fog. Our results clearly indicates that accounting for the presence of aerosols and their radiative-transfer is important in modeling micro-meteorological process of fog formation and its evolution. DST, Govt. INDIA.

  16. An SDR based AIS receiver for satellites

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Mortensen, Hans Peter; Nielsen, Jens Frederik Dalsgaard

    2011-01-01

    For a few years now, there has been a high interest in monitoring the global ship traffic from space. A few satellite, capable of listening for ship borne AIS transponders have already been launched, and soon the AAUSAT3, carrying two different types of AIS receivers will also be launched. One...... of the AIS receivers onboard AAUSAT3 is an SDR based AIS receiver. This paper serves to describe the background of the AIS system, and how the SDR based receiver has been integrated into the AAUSAT3 satellite. Amongst some of the benefits of using an SDR based receiver is, that due to its versatility, new...

  17. A Space Based Solar Power Satellite System

    Science.gov (United States)

    Engel, J. M.; Polling, D.; Ustamujic, F.; Yaldiz, R.; et al.

    2002-01-01

    (SPoTS) supplying other satellites with energy. SPoTS is due to be commercially viable and operative in 2020. of Technology designed the SPoTS during a full-time design period of six weeks as a third year final project. The team, organized according to the principles of systems engineering, first conducted a literature study on space wireless energy transfer to select the most suitable candidates for use on the SPoTS. After that, several different system concepts have been generated and evaluated, the most promising concept being worked out in greater detail. km altitude. Each SPoTS satellite has a 50m diameter inflatable solar collector that focuses all received sunlight. Then, the received sunlight is further redirected by means of four pointing mirrors toward four individual customer satellites. A market-analysis study showed, that providing power to geo-stationary communication satellites during their eclipse would be most beneficial. At arrival at geo-stationary orbit, the focused beam has expended to such an extent that its density equals one solar flux. This means that customer satellites can continue to use their regular solar arrays during their eclipse for power generation, resulting in a satellite battery mass reduction. the customer satellites in geo-stationary orbit, the transmitted energy beams needs to be pointed with very high accuracy. Computations showed that for this degree of accuracy, sensors are needed, which are not mainstream nowadays. Therefore further research must be conducted in this area in order to make these high-accuracy-pointing systems commercially attractive for use on the SPoTS satellites around 2020. Total 20-year system lifetime cost for 18 SPoT satellites are estimated at approximately USD 6 billion [FY2001]. In order to compete with traditional battery-based satellite power systems or possible ground based wireless power transfer systems the price per kWh for the customer must be significantly lower than the present one

  18. Motorway lighting under fog conditions : based on a paper presented at Japan Highway Corporation, Tokyo, 12 July 1990.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1992-01-01

    This study defines fog as an aerosol consisting primarily of water droplets. The main effect on road traffic is the contrast reduction as a result of the scatter of light in the aerosol. Absorption plays only a small role. The effect of the contrast reduction is that many objects in the field of vie

  19. Motorway lighting under fog conditions : based on a paper presented at Japan Highway Corporation, Tokyo, 12 July 1990.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1992-01-01

    This study defines fog as an aerosol consisting primarily of water droplets. The main effect on road traffic is the contrast reduction as a result of the scatter of light in the aerosol. Absorption plays only a small role. The effect of the contrast reduction is that many objects in the field of vie

  20. Lorentz Force Based Satellite Attitude Control

    Science.gov (United States)

    Giri, Dipak Kumar; Sinha, Manoranjan

    2016-07-01

    Since the inception of attitude control of a satellite, various active and passive control strategies have been developed. These include using thrusters, momentum wheels, control moment gyros and magnetic torquers. In this present work, a new technique named Lorentz force based Coulombic actuators for the active control is proposed. This method uses electrostatic charged shells, which interact with the time varying earth's magnetic field to establish a full three axes control of the satellite. It is shown that the proposed actuation mechanism is similar to a satellite actuated by magnetic coils except that the resultant magnetic moment vanishes under two different conditions. The equation for the required charges on the the Coulomb shells attached to the satellite body axes is derived, which is in turn used to find the available control torque for actuating the satellite along the orbit. Stability of the proposed system for very high initial angular velocity and exponential stability about the origin are proved for a proportional-differential control input. Simulations are carried out to show the efficacy of the proposed system for the attitude control of the earth-pointing satellite.

  1. 基于雾气理论的视频去雾算法%Video Defogging Algorithm Based on Fog Theory

    Institute of Scientific and Technical Information of China (English)

    郭璠; 蔡自兴; 谢斌

    2011-01-01

    本文提出了两种基于雾气理论的视频去雾新算法,一种视雾气为覆盖在各帧图像上的一层遮罩被从原视频中减除,一种视雾气为光路传播图被分离消除.前者将Retinex算法得到的亮度图像与视频帧自身的深度关系相结合求取雾气遮罩,并将此遮罩从原视频帧中分离以去除雾气;后者将由背景图像得到的视频“通用”传播图应用于视频的所有帧以消除雾气.实验证明两种算法均能有效地提高原有雾视频各帧的对比度和清晰度.本文所提算法从雾气的角度人手,无需借助参考图像,运算代价低,与一般视频去雾算法相比,在获得较优的去雾效果的同时,具有较好的实用性和较快的处理速度.%In this paper,we proposed two new video defogging algorithms based on fog theory. One is regarding fog as the veil layer to be subtracted, and the other is taking fog as the transmission map to be separated from the original video. The former uses the luminance component image obtained by Retinex algorithm and the depth information of the original video frames to separate the veil layer. The latter applies a single transmission map obtained from the background image to a series of video frames. Experiments show that both algorithms can effectively improve the contrast and quality of the video frames. Compared with other state of the art algorithms,our algorithms restore video frames from a perspective of fog with no reference image and low computation cost.The new algorithms can remove fog effectively as well as provide a good practicability and a fast speed.

  2. Wind Statistics Offshore based on Satellite Images

    DEFF Research Database (Denmark)

    Hasager, Charlotte Bay; Mouche, Alexis; Badger, Merete

    2009-01-01

    Ocean wind maps from satellites are routinely processed both at Risø DTU and CLS based on the European Space Agency Envisat ASAR data. At Risø the a priori wind direction is taken from the atmospheric model NOGAPS (Navel Operational Global Atmospheric Prediction System) provided by the U.S. Navy......’s Master Environmental Library. At CLS the a priori wind direction is taken from the ECMWF (European Centre of Medium-range Weather Forecasting). It is also possible to use other sources of wind direction e.g. the satellite-based ASCAT wind directions as demonstrated by CLS. The wind direction has to known...

  3. Satellite Formation based on SDDF Method

    Directory of Open Access Journals (Sweden)

    Yu Wang

    2014-04-01

    Full Text Available The technology of satellite formation flying has being a research focus in flight application. The relative position and velocity between satellites are basic parameters to achieve the control of formation flight during the satellite formation flying mission. In order to improve the navigation accuracy, a new filter different from Extended Kalman Filter (EKF should be adopted to estimate the errors of relative position and velocity, which is based on the nonlinearity of the kinetic model for the satellite formation flying. A nonlinear Divided Difference Filter (DDF based on Stirling interpolation formula was proposed in this paper. According to the linearity of the measurement equation for the filter, a simplified differential filter was designed by means of expanding the polynomial of the nonlinear system equation and linear approximating of the finite differential interpolation. Digital simulation experiment for the relative positioning of satellite formation flying was carried out. The result demonstrates that the filter proposed in this paper has a higher filtering accuracy, faster convergence speed and better stability. Compared with the EKF, the estimation accuracy of the relative position and velocity has improved by 77.1%and 47% respectively in the method of simplified DDF, which indicates the significance for practical applications. 

  4. Satellite-based terrestrial production efficiency modeling

    Directory of Open Access Journals (Sweden)

    Obersteiner Michael

    2009-09-01

    Full Text Available Abstract Production efficiency models (PEMs are based on the theory of light use efficiency (LUE which states that a relatively constant relationship exists between photosynthetic carbon uptake and radiation receipt at the canopy level. Challenges remain however in the application of the PEM methodology to global net primary productivity (NPP monitoring. The objectives of this review are as follows: 1 to describe the general functioning of six PEMs (CASA; GLO-PEM; TURC; C-Fix; MOD17; and BEAMS identified in the literature; 2 to review each model to determine potential improvements to the general PEM methodology; 3 to review the related literature on satellite-based gross primary productivity (GPP and NPP modeling for additional possibilities for improvement; and 4 based on this review, propose items for coordinated research. This review noted a number of possibilities for improvement to the general PEM architecture - ranging from LUE to meteorological and satellite-based inputs. Current PEMs tend to treat the globe similarly in terms of physiological and meteorological factors, often ignoring unique regional aspects. Each of the existing PEMs has developed unique methods to estimate NPP and the combination of the most successful of these could lead to improvements. It may be beneficial to develop regional PEMs that can be combined under a global framework. The results of this review suggest the creation of a hybrid PEM could bring about a significant enhancement to the PEM methodology and thus terrestrial carbon flux modeling. Key items topping the PEM research agenda identified in this review include the following: LUE should not be assumed constant, but should vary by plant functional type (PFT or photosynthetic pathway; evidence is mounting that PEMs should consider incorporating diffuse radiation; continue to pursue relationships between satellite-derived variables and LUE, GPP and autotrophic respiration (Ra; there is an urgent need for

  5. Instant AppFog

    CERN Document Server

    Wee, Pau Kiat

    2013-01-01

    Get to grips with a new technology, understand what it is and what it can do for you, and then get to work with the most important features and tasks. This easy to follow, hands-on guide shows you how to deploy and manage your application within minutes.Instant AppFog Starter is great for developers who are new to AppFog and who are primarily working on code rather than infrastructure. This book is perfect for those who are looking to publish applications without an in-depth knowledge of servers, firewalls, and networking. It is assumed that you will have some experience of web development as

  6. Demand Side Management Using the Internet of Energy based on Fog and Cloud Computing

    DEFF Research Database (Denmark)

    Shahryari, Kolsoom; Anvari-Moghaddam, Amjad

    2017-01-01

    The smart grid, as a communication network, allows numerous connected devices such as sensors, relays and actuators to interact and cooperate with each other. An Internet-based solution for electricity that provides bidirectional flow of information and power is internet of energy (IoE) which...

  7. Virucidal Activity of Fogged Chlorine Dioxide- and Hydrogen Peroxide-Based Disinfectants against Human Norovirus and Its Surrogate, Feline Calicivirus, on Hard-to-Reach Surfaces

    Directory of Open Access Journals (Sweden)

    Naim Montazeri

    2017-06-01

    Full Text Available Human norovirus (NoV is the leading cause of foodborne illnesses in the United States. Norovirus is shed in high numbers in the feces and vomitous of infected individuals. Contact surfaces contaminated with bodily fluids harboring infectious virus particles serve as vehicles for pathogen transmission. Environmental stability of NoV and its resistance to many conventional disinfectants necessitate effective inactivation strategies to control the spread of virus. We investigated the efficacy of two commercial disinfectants, hydrogen peroxide (7.5% and a chlorine dioxide (0.2%-surfactant-based product using a fogging delivery system against human NoV GI.6 and GII.4 Sydney strains as well as the cultivable surrogate, feline calicivirus (FCV dried on stainless steel coupons. Log10 reductions in human NoV and FCV were calculated utilizing RNase RT-qPCR and infectivity (plaque assay, respectively. An improved antiviral activity of hydrogen peroxide as a function of disinfectant formulation concentration in the atmosphere was observed against both GII.4 and FCV. At 12.4 ml/m3, hydrogen peroxide achieved a respective 2.5 ± 0.1 and 2.7 ± 0.3 log10 reduction in GI.6 and GII.4 NoV genome copies, and a 4.3 ± 0.1 log10 reduction in infectious FCV within 5 min. At the same disinfectant formulation concentration, chlorine dioxide-surfactant-based product resulted in a respective 1.7 ± 0.2, 0.6 ± 0.0, and 2.4 ± 0.2 log10 reduction in GI.6, GII.4, and FCV within 10 min; however, increasing the disinfectant formulation concentration to 15.9 ml/m3 negatively impacted its efficacy. Fogging uniformly delivered the disinfectants throughout the room, and effectively decontaminated viruses on hard-to-reach surfaces. Hydrogen peroxide delivered by fog showed promising virucidal activity against FCV by meeting the United States EPA 4-log10 reduction criteria for an anti-noroviral disinfectant; however, fogged chlorine dioxide-surfactant-based product did not achieve

  8. Virucidal Activity of Fogged Chlorine Dioxide- and Hydrogen Peroxide-Based Disinfectants against Human Norovirus and Its Surrogate, Feline Calicivirus, on Hard-to-Reach Surfaces.

    Science.gov (United States)

    Montazeri, Naim; Manuel, Clyde; Moorman, Eric; Khatiwada, Janak R; Williams, Leonard L; Jaykus, Lee-Ann

    2017-01-01

    Human norovirus (NoV) is the leading cause of foodborne illnesses in the United States. Norovirus is shed in high numbers in the feces and vomitous of infected individuals. Contact surfaces contaminated with bodily fluids harboring infectious virus particles serve as vehicles for pathogen transmission. Environmental stability of NoV and its resistance to many conventional disinfectants necessitate effective inactivation strategies to control the spread of virus. We investigated the efficacy of two commercial disinfectants, hydrogen peroxide (7.5%) and a chlorine dioxide (0.2%)-surfactant-based product using a fogging delivery system against human NoV GI.6 and GII.4 Sydney strains as well as the cultivable surrogate, feline calicivirus (FCV) dried on stainless steel coupons. Log10 reductions in human NoV and FCV were calculated utilizing RNase RT-qPCR and infectivity (plaque) assay, respectively. An improved antiviral activity of hydrogen peroxide as a function of disinfectant formulation concentration in the atmosphere was observed against both GII.4 and FCV. At 12.4 ml/m(3), hydrogen peroxide achieved a respective 2.5 ± 0.1 and 2.7 ± 0.3 log10 reduction in GI.6 and GII.4 NoV genome copies, and a 4.3 ± 0.1 log10 reduction in infectious FCV within 5 min. At the same disinfectant formulation concentration, chlorine dioxide-surfactant-based product resulted in a respective 1.7 ± 0.2, 0.6 ± 0.0, and 2.4 ± 0.2 log10 reduction in GI.6, GII.4, and FCV within 10 min; however, increasing the disinfectant formulation concentration to 15.9 ml/m(3) negatively impacted its efficacy. Fogging uniformly delivered the disinfectants throughout the room, and effectively decontaminated viruses on hard-to-reach surfaces. Hydrogen peroxide delivered by fog showed promising virucidal activity against FCV by meeting the United States EPA 4-log10 reduction criteria for an anti-noroviral disinfectant; however, fogged chlorine dioxide-surfactant-based product did not achieve a 4-log10

  9. Development and validation of satellite-based estimates of surface visibility

    Science.gov (United States)

    Brunner, J.; Pierce, R. B.; Lenzen, A.

    2016-02-01

    A satellite-based surface visibility retrieval has been developed using Moderate Resolution Imaging Spectroradiometer (MODIS) measurements as a proxy for Advanced Baseline Imager (ABI) data from the next generation of Geostationary Operational Environmental Satellites (GOES-R). The retrieval uses a multiple linear regression approach to relate satellite aerosol optical depth, fog/low cloud probability and thickness retrievals, and meteorological variables from numerical weather prediction forecasts to National Weather Service Automated Surface Observing System (ASOS) surface visibility measurements. Validation using independent ASOS measurements shows that the GOES-R ABI surface visibility retrieval (V) has an overall success rate of 64.5 % for classifying clear (V ≥ 30 km), moderate (10 km ≤ V skill during June through September, when Heidke skill scores are between 0.2 and 0.4. We demonstrate that the aerosol (clear-sky) component of the GOES-R ABI visibility retrieval can be used to augment measurements from the United States Environmental Protection Agency (EPA) and National Park Service (NPS) Interagency Monitoring of Protected Visual Environments (IMPROVE) network and provide useful information to the regional planning offices responsible for developing mitigation strategies required under the EPA's Regional Haze Rule, particularly during regional haze events associated with smoke from wildfires.

  10. Research Fog- Degraded Images Clearness Algorithm Based on the MSR%基于MSR的雾天图像清晰化算法研究

    Institute of Scientific and Technical Information of China (English)

    程娅荔; 张也驰

    2012-01-01

    Research the fog - degraded images clearness problem to improve the uniformity of the image enhancement. In foggy weather conditions, fog makes images contrast low and image local details not clear. The traditional fog-degraded images clearness algorithm based on histogram equalization can enhance image contrast, but the enhancement of image local details is insufficient, causing image enhancement uniformity is not high. This paper proposed a fog - degraded image clearness algorithm based on MSR. Through the Sigmoid function, the image was mapped and the image contrast was stretched. Then, the MSR algorithm was used to get the image wavelet decomposition for high frequency components and low frequency components. The high frequency components were calculate for the largest absolute value and the low frequency components were calculate for the weighted average. Experiments show that the algorithm can enhance the image contrast and get high - definition images.%研究雾天图像清晰化的问题,需提高图像增强的均匀性.针对雾天情况下,由于雾气的遮挡使得拍摄图像对比度降低,图像局部细节处不清晰,传统的直方图均衡化的雾天图像清晰化方法虽然能够增强图像对比度,但是图像局部细节增强不足,造成图像增强均匀性不高的问题.提出一种MSR的雾天图像清晰化算法,通过Sigmoid函数对图像作映射,拉伸图像的对比度,然后利用MSR算法,将图像小波分解为高频分量和低频分量,对高频分量取绝对值最大运算,低频分量加权平均,并避免了对图像进行全局直方图均衡化造成的图像增强不均匀,局部细节增强不足的问题.实验证明,提出的算法能够将雾天图像均匀增强,得到高清晰的图像,取得了满意的效果.

  11. An SDR based AIS receiver for satellites

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Mortensen, Hans Peter; Nielsen, Jens Frederik Dalsgaard

    2011-01-01

    For a few years now, there has been a high interest in monitoring the global ship traffic from space. A few satellite, capable of listening for ship borne AIS transponders have already been launched, and soon the AAUSAT3, carrying two different types of AIS receivers will also be launched. One...... of the AIS receivers onboard AAUSAT3 is an SDR based AIS receiver. This paper serves to describe the background of the AIS system, and how the SDR based receiver has been integrated into the AAUSAT3 satellite. Amongst some of the benefits of using an SDR based receiver is, that due to its versatility, new...... detection algorithms are easily deployed, and it is easily adapted the new proposed AIS transmission channels....

  12. Probabilistic Model for Free-Space Optical Links Under Continental Fog Conditions

    Directory of Open Access Journals (Sweden)

    Marzuki

    2010-09-01

    Full Text Available The error characteristics of a free-space optical (FSO channel are significantly different from the fiber based optical links and thus require a deep physical understanding of the propagation channel. In particular different fog conditions greatly influence the optical transmissions and thus a channel model is required to estimate the detrimental fog effects. In this paper we shall present the probabilistic model for radiation fog from the measured data over a 80 m FSO link installed at Graz, Austria. The fog events are classified into thick fog, moderate fog, light fog and general fog based on the international code of visibility range. We applied some probability distribution functions (PDFs such as Kumaraswamy, Johnson SB and Logistic distribution, to the actual measured optical attenuations. The performance of each distribution is evaluated by Q-Q and P-P plots. It is found that Kumaraswamy distribution is the best fit for general fog, while Logistic distribution is the optimum choice for thick fog. On the other hand, Johnson SB distribution best fits the moderate and light fog related measured attenuation data. The difference in these probabilistic models and the resultant variation in the received signal strength under different fog types needs to be considered in designing an efficient FSO system.

  13. In the Fog

    Institute of Scientific and Technical Information of China (English)

    程炜

    2002-01-01

    One morning there was such a thick fog that the drivers could hardly see the roads. Mr Brown was driving a car in the street. He was driving slowly,but still he was afraid that he might bump into a tree or something. Just then he saw a red car in front and decided to follow it.

  14. Satellite Contamination and Materials Outgassing Knowledge base

    Science.gov (United States)

    Minor, Jody L.; Kauffman, William J. (Technical Monitor)

    2001-01-01

    Satellite contamination continues to be a design problem that engineers must take into account when developing new satellites. To help with this issue, NASA's Space Environments and Effects (SEE) Program funded the development of the Satellite Contamination and Materials Outgassing Knowledge base. This engineering tool brings together in one location information about the outgassing properties of aerospace materials based upon ground-testing data, the effects of outgassing that has been observed during flight and measurements of the contamination environment by on-orbit instruments. The knowledge base contains information using the ASTM Standard E- 1559 and also consolidates data from missions using quartz-crystal microbalances (QCM's). The data contained in the knowledge base was shared with NASA by government agencies and industry in the US and international space agencies as well. The term 'knowledgebase' was used because so much information and capability was brought together in one comprehensive engineering design tool. It is the SEE Program's intent to continually add additional material contamination data as it becomes available - creating a dynamic tool whose value to the user is ever increasing. The SEE Program firmly believes that NASA, and ultimately the entire contamination user community, will greatly benefit from this new engineering tool and highly encourages the community to not only use the tool but add data to it as well.

  15. Advective, orographic and radiation fog in the Tarapacá region, Chile

    Science.gov (United States)

    Cereceda, P.; Osses, P.; Larrain, H.; Farías, M.; Lagos, M.; Pinto, R.; Schemenauer, R. S.

    A project in northern Chile was undertaken to determine the origin and behaviour of fog in the coastal and inland locations of the Tarapacá Region. In the Pampa del Tamarugal, 50 km from the sea, conditions exist for the formation of radiation fog. Advective fog has been studied on the coast and orographic fog was observed at a few coastal sites near mountain ranges with elevations above 1000 m. Fog water collected by two standard fog collectors (SFC) for 3 1/2 years showed an average flux of 8.5 l m -2 day -1 on the coast and 1.1 l m -2 day -1 inland 12 km from the coastline. On only a few days in 10 months was water collected at the inland site of Pampa del Tamarugal. GOES satellite images are shown to illustrate the pattern of formation of the stratocumuli cloud over the sea, its approach to the coastline, the entrance of fog by corridors through the coastal range and the presence of radiation fog inland. The results are important for the understanding of fog formation and dissipation along the coastal mountain range and for the recognition of potential sites for the installation of fog water collectors, which can be used as a water source in the Atacama Desert. The results also provide vital information for use in the preservation of the unique ecosystems of the most arid desert of the world.

  16. Noise correlation-based adaptive polarimetric image representation for contrast enhancement of a polarized beacon in fog

    Science.gov (United States)

    Panigrahi, Swapnesh; Fade, Julien; Alouini, Mehdi

    2015-10-01

    We show the use of a simplified snapshot polarimetric camera along with an adaptive image processing for optimal detection of a polarized light beacon through fog. The adaptive representation is derived using theoretical noise analysis of the data at hand and is shown to be optimal in the Maximum likelihood sense. We report that the contrast enhancing optimal representation that depends on the background noise correlation differs in general from standard representations like polarimetric difference image or polarization filtered image. Lastly, we discuss a detection strategy to reduce the false positive counts.

  17. Analysis of the Sea Fog in the Sea Around the Great Wall Station,Antarctica

    Institute of Scientific and Technical Information of China (English)

    黄耀荣; 薛振和

    2001-01-01

    The synoptic analysis of sea fog in western Antarctic sea region is made based on the observation data in the Chinese Antarctic station, Great Wall Station, from December 1994 to November 1995, and the facsimile weather charts issued by Chile. It is found that more than 90% fog in this region is the advection cooling fog. Also, the synoptic mechanism of the fog creation and distinction is discussed by analyzing the pressure field, the temperature field and the upperlevel stratification. Finally, the focus of attention in forecasting fog is pointed out.

  18. Investigation of Sea Surface Temperature and local topography effects on coastal fog: Case study of 21-22 January 2008 event on the west coast of Morocco

    Science.gov (United States)

    Bari, Driss; Bergot, Thierry; El Khlifi, Mohamed

    2014-05-01

    The life cycle of fog over coastal regions is very sensitive to the heterogeneity of the landform and to the vicinity to the Ocean. Thus, the influence of the sea surface temperature (SST) and local topography on the evolution of a coastal fog is assessed in this study by performing sensitivity experiments. To achieve this, the numerical simulations are performed with the three-dimensional research model Meso-NH. This fog event occurred at the Grand Casablanca region, in the northwest coast of Morocco, during the night of 21-22 January 2008 and last more than 12 hours. It was analyzed using standard meteorological observations from the two synoptic stations of the region, the observed radio-sounding at the coastal station, the MSG satellite imagery and the ECMWF ERA-Interim reanalysis. The numerical simulation reproduced well the main features of this fog event since its formation to its dissipation. The numerical results demonstrated that this fog event was of a radiation type over land, due to the nocturnal radiative cooling and the turbulence. And one hour later near the coast, the fog was resulting from base lowering of Stratus low cloud, due to the cloud top cooling and the vertical turbulent mixing. The sensitivity experiments to SST demonstrate that varying SST in space and time affects the spatial distribution of the fog layer over an area of about 20km around the coast. Besides, the SST governs the thermodynamic fluxes at the air-sea interface, and then affects the life cycle of this fog event, in particular in the mature and dissipation phases. On the other hand, the sensitivity experiments to local coastal topography demonstrated its impact on the speed and direction of wind in the boundary layer during the different phases of the life cycle of this fog event. Then, it was found that the heterogeneities of terrain over the coastal regions affect the horizontal extension of this fog event during the mature phase and its evolution during the dissipation

  19. Satellite-based Tropical Cyclone Monitoring Capabilities

    Science.gov (United States)

    Hawkins, J.; Richardson, K.; Surratt, M.; Yang, S.; Lee, T. F.; Sampson, C. R.; Solbrig, J.; Kuciauskas, A. P.; Miller, S. D.; Kent, J.

    2012-12-01

    Satellite remote sensing capabilities to monitor tropical cyclone (TC) location, structure, and intensity have evolved by utilizing a combination of operational and research and development (R&D) sensors. The microwave imagers from the operational Defense Meteorological Satellite Program [Special Sensor Microwave/Imager (SSM/I) and the Special Sensor Microwave Imager Sounder (SSMIS)] form the "base" for structure observations due to their ability to view through upper-level clouds, modest size swaths and ability to capture most storm structure features. The NASA TRMM microwave imager and precipitation radar continue their 15+ yearlong missions in serving the TC warning and research communities. The cessation of NASA's QuikSCAT satellite after more than a decade of service is sorely missed, but India's OceanSat-2 scatterometer is now providing crucial ocean surface wind vectors in addition to the Navy's WindSat ocean surface wind vector retrievals. Another Advanced Scatterometer (ASCAT) onboard EUMETSAT's MetOp-2 satellite is slated for launch soon. Passive microwave imagery has received a much needed boost with the launch of the French/Indian Megha Tropiques imager in September 2011, basically greatly supplementing the very successful NASA TRMM pathfinder with a larger swath and more frequent temporal sampling. While initial data issues have delayed data utilization, current news indicates this data will be available in 2013. Future NASA Global Precipitation Mission (GPM) sensors starting in 2014 will provide enhanced capabilities. Also, the inclusion of the new microwave sounder data from the NPP ATMS (Oct 2011) will assist in mapping TC convective structures. The National Polar orbiting Partnership (NPP) program's VIIRS sensor includes a day night band (DNB) with the capability to view TC cloud structure at night when sufficient lunar illumination exits. Examples highlighting this new capability will be discussed in concert with additional data fusion efforts.

  20. Operational evapotranspiration based on Earth observation satellites

    Science.gov (United States)

    Gellens-Meulenberghs, Françoise; Ghilain, Nicolas; Arboleda, Alirio; Barrios, Jose-Miguel

    2016-04-01

    Geostationary satellites have the potential to follow fast evolving atmospheric and Earth surface phenomena such those related to cloud cover evolution and diurnal cycle. Since about 15 years, EUMETSAT has set up a network named 'Satellite Application Facility' (SAF, http://www.eumetsat.int/website/home/Satellites/GroundSegment/Safs/index.html) to complement its ground segment. The Land Surface Analysis (LSA) SAF (http://landsaf.meteo.pt/) is devoted to the development of operational products derived from the European meteorological satellites. In particular, an evapotranspiration (ET) product has been developed by the Royal Meteorological Institute of Belgium. Instantaneous and daily integrated results are produced in near real time and are freely available respectively since the end of 2009 and 2010. The products cover Europe, Africa and the Eastern part of South America with the spatial resolution of the SEVIRI sensor on-board Meteosat Second Generation (MSG) satellites. The ET product algorithm (Ghilain et al., 2011) is based on a simplified Soil-Vegetation-Atmosphere transfer (SVAT) scheme, forced with MSG derived radiative products (LSA SAF short and longwave surface fluxes, albedo). It has been extensively validated against in-situ validation data, mainly FLUXNET observations, demonstrating its good performances except in some arid or semi-arid areas. Research has then been pursued to develop an improved version for those areas. Solutions have been found in reviewing some of the model parameterizations and in assimilating additional satellite products (mainly vegetation indices and land surface temperature) into the model. The ET products will be complemented with related latent and sensible heat fluxes, to allow the monitoring of land surface energy partitioning. The new algorithm version should be tested in the LSA-SAF operational computer system in 2016 and results should become accessible to beta-users/regular users by the end of 2016/early 2017. In

  1. Crowd Sensing-Enabling Security Service Recommendation for Social Fog Computing Systems.

    Science.gov (United States)

    Wu, Jun; Su, Zhou; Wang, Shen; Li, Jianhua

    2017-07-30

    Fog computing, shifting intelligence and resources from the remote cloud to edge networks, has the potential of providing low-latency for the communication from sensing data sources to users. For the objects from the Internet of Things (IoT) to the cloud, it is a new trend that the objects establish social-like relationships with each other, which efficiently brings the benefits of developed sociality to a complex environment. As fog service become more sophisticated, it will become more convenient for fog users to share their own services, resources, and data via social networks. Meanwhile, the efficient social organization can enable more flexible, secure, and collaborative networking. Aforementioned advantages make the social network a potential architecture for fog computing systems. In this paper, we design an architecture for social fog computing, in which the services of fog are provisioned based on "friend" relationships. To the best of our knowledge, this is the first attempt at an organized fog computing system-based social model. Meanwhile, social networking enhances the complexity and security risks of fog computing services, creating difficulties of security service recommendations in social fog computing. To address this, we propose a novel crowd sensing-enabling security service provisioning method to recommend security services accurately in social fog computing systems. Simulation results show the feasibilities and efficiency of the crowd sensing-enabling security service recommendation method for social fog computing systems.

  2. The Structure and Formation Mechanism of a Sea Fog Event over the Yellow Sea

    Institute of Scientific and Technical Information of China (English)

    GUO Jingtian; LI Pengyuan; FU Gang; ZHANG Wei; GAO Shanhong; ZHANG Suping

    2015-01-01

    In this paper, a heavy sea fog event occurring over the Yellow Sea on 11 April 2004 was investigated based upon obser-vational and modeling analyses. From the observational analyses, this sea fog event is a typical advection cooling case. Sea surface temperature (SST) and specific humidity (SH) show strong gradients from south to north, in which warm water is located in the south and consequently, moisture is larger in the south than in the north due to evaporation processes. After fog formation, evaporation process provides more moisture into the air and further contributes to fog evolution. The sea fog event was reproduced by the Re-gional Atmospheric Modeling System (RAMS) reasonably. The roles of important physical processes such as radiation, turbulence as well as atmospheric stratification in sea fog’s structure and its formation mechanisms were analyzed using the model results. The roles of long wave radiation cooling, turbulence as well as atmospheric stratification were analyzed based on the modeling results. It is found that the long wave radiative cooling at the fog top plays an important role in cooling down the fog layer through turbulence mixing. The fog top cooling can overpower warming from the surface. Sea fog develops upward with the aid of turbulence. The buoyancy term,i.e., the unstable layer, contributes to the generation of TKE in the fog region. However, the temperature inversion layer prevents fog from growing upward.

  3. Hierarchical Surface Architecture of Plants as an Inspiration for Biomimetic Fog Collectors.

    Science.gov (United States)

    Azad, M A K; Barthlott, W; Koch, K

    2015-12-01

    Fog collectors can enable us to alleviate the water crisis in certain arid regions of the world. A continuous fog-collection cycle consisting of a persistent capture of fog droplets and their fast transport to the target is a prerequisite for developing an efficient fog collector. In regard to this topic, a biological superior design has been found in the hierarchical surface architecture of barley (Hordeum vulgare) awns. We demonstrate here the highly wettable (advancing contact angle 16° ± 2.7 and receding contact angle 9° ± 2.6) barbed (barb = conical structure) awn as a model to develop optimized fog collectors with a high fog-capturing capability, an effective water transport, and above all an efficient fog collection. We compare the fog-collection efficiency of the model sample with other plant samples naturally grown in foggy habitats that are supposed to be very efficient fog collectors. The model sample, consisting of dry hydrophilized awns (DH awns), is found to be about twice as efficient (fog-collection rate 563.7 ± 23.2 μg/cm(2) over 10 min) as any other samples investigated under controlled experimental conditions. Finally, a design based on the hierarchical surface architecture of the model sample is proposed for the development of optimized biomimetic fog collectors.

  4. An innovative artificial fog production device improved in the European project “FOG”

    Science.gov (United States)

    Colomb, M.; Hirech, K.; André, P.; Boreux, J. J.; Lacôte, P.; Dufour, J.

    2008-03-01

    Transport safety is a major goal in the European Union. Low visibility conditions, especially due to fog, increase the risk of major accidents (chain collision). Innovative products have been developed by the automotive industry, including equipment manufacturers, to increase the level of safety of car passengers and drivers. Testing of these products requires the simulation or artificial reproduction of low visibility (fog) conditions with good stability and reproducibility characteristics. We report on the results of the European Union funded "FOG" project to improve road transport safety through fog production in an experimental test chamber located at the Clermont-Ferrand laboratory for research on road safety and visibility. The project developed a prototype of a small-scale climatic chamber, an improved fog production spraying device, a laser-based visibility measurement device, a reduced scale transmissometer, and a combined indoor climate-fog production simulation software. The ability of the fog chamber to test for driver reaction was also investigated. Recent developments include a device able to produce stable visibility levels and homogeneous fog, representative of various types of natural water droplet distribution. The fog characteristics were determined and compared to natural fog. Results are presented for a selection of conditions including stabilized visibility levels for dense fog and two kinds of droplet distributions.

  5. Project Fog Drops. Part 1: Investigations of warm fog properties

    Science.gov (United States)

    Pilie, R. J.; Eadie, W.; Mack, E. J.; Rogers, C.; Kocmond, W. C.

    1972-01-01

    A detailed study was made of the micrometeorological and microphysical characteristics of eleven valley fogs occurring near Elmira, New York. Observations were made of temperature, dew point, wind speed and direction, dew deposition, vertical wind velocity, and net radiative flux. In fog, visibility was continuously recorded and periodic measurements were made of liquid water content and drop-size distribution. The observations were initiated in late evening and continued until the time of fog dissipation. The vertical distribution of temperature in the lowest 300 meters and cloud nucleus concentration at several heights were measured from an aircraft before fog nucleus concentrations at several heights were measured from an aircraft before fog formation. A numerical model was developed to investigate the life cycle of radiation fogs. The model predicts the temporal evolution of the vertical distributions of temperature, water vapor, and liquid water as determined by the turbulent transfer of heat and moisture. The model includes the nocturnal cooling of the earth's surface, dew formation, fog drop sedimentation, and the absorption of infrared radiation by fog.

  6. Humidification - Fogging and other evaporative cooling in greenhouses

    NARCIS (Netherlands)

    Nederhoff, E.M.; Weel, van P.A.

    2011-01-01

    Fogging, misting, roof sprinklers, pad-and-fan and other techniques based on water evaporation are effective tools for improving the growing conditions in a greenhouse when humidity is low. They should be used wisely though.

  7. Humidification - Fogging and other evaporative cooling in greenhouses

    NARCIS (Netherlands)

    Nederhoff, E.M.; Weel, van P.A.

    2011-01-01

    Fogging, misting, roof sprinklers, pad-and-fan and other techniques based on water evaporation are effective tools for improving the growing conditions in a greenhouse when humidity is low. They should be used wisely though.

  8. Monitoring objects orbiting earth using satellite-based telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Scot S.; Pertica, Alexander J.; Riot, Vincent J.; De Vries, Willem H.; Bauman, Brian J.; Nikolaev, Sergei; Henderson, John R.; Phillion, Donald W.

    2015-06-30

    An ephemeris refinement system includes satellites with imaging devices in earth orbit to make observations of space-based objects ("target objects") and a ground-based controller that controls the scheduling of the satellites to make the observations of the target objects and refines orbital models of the target objects. The ground-based controller determines when the target objects of interest will be near enough to a satellite for that satellite to collect an image of the target object based on an initial orbital model for the target objects. The ground-based controller directs the schedules to be uploaded to the satellites, and the satellites make observations as scheduled and download the observations to the ground-based controller. The ground-based controller then refines the initial orbital models of the target objects based on the locations of the target objects that are derived from the observations.

  9. Prediction of Radiation Fog by DNA Computing

    OpenAIRE

    Ray, Kumar Sankar; Mondal, Mandrita

    2015-01-01

    In this paper we propose a wet lab algorithm for prediction of radiation fog by DNA computing. The concept of DNA computing is essentially exploited for generating the classifier algorithm in the wet lab. The classifier is based on a new concept of similarity based fuzzy reasoning suitable for wet lab implementation. This new concept of similarity based fuzzy reasoning is different from conventional approach to fuzzy reasoning based on similarity measure and also replaces the logical aspect o...

  10. Coastal Upwelling and Deep Fog: 50-year Worldwide Climatology

    Science.gov (United States)

    Koracin, D. R.

    2015-12-01

    An analysis is presented of the marine fog distribution based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Deep fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. Occurrence is estimated by the number of deep fog observations divided by the total present weather observations in a one-degree area centered on latitude and longitude grid point intersections. The mean fog occurrence for the summer (June-July-August) 1950-2007 was computed for each one degree point for the world. There are five major world locations with coastal SST minimums due to wind driven upwelling. Four of these are during the local summer on the eastern side of a semi-permanent anticyclone on eastern sides of northern and southern mid-latitudes of the Pacifica and the Atlantic. The fifth is during the SW monsoon in the Indian Ocean. For all five of these locations, the deep fog occurrence is at maximum during the upwelling season, with the greatest occurrences concentrated along the coast and isolated over the SST minimum. For the five coastal fog maxima, the greatest and longest duration occurrence along coast occurrence is associated with the coldest sea surface temperature and longest along coast occurrence, which is along N. California- S. Oregon. In contrast, the lowest occurrence of fog and the least along coast occurrence is associated with the warmest sea surface temperatures and least along coast occurrence along the SE Arabian Peninsula. The remaining three zones, Peru-Chile, NW Africa, and SW Africa are between the two extremes in fog occurrence, along coast coverage and sea surface temperature. Peru-Chile is more complex than the others as the Peru upwelling and fog appears the more dominant although ship observations are sparse along Chile.

  11. Earth Observation Satellites Scheduling Based on Decomposition Optimization Algorithm

    Directory of Open Access Journals (Sweden)

    Feng Yao

    2010-11-01

    Full Text Available A decomposition-based optimization algorithm was proposed for solving Earth Observation Satellites scheduling problem. The problem was decomposed into task assignment main problem and single satellite scheduling sub-problem. In task assignment phase, the tasks were allocated to the satellites, and each satellite would schedule the task respectively in single satellite scheduling phase. We adopted an adaptive ant colony optimization algorithm to search the optimal task assignment scheme. Adaptive parameter adjusting strategy and pheromone trail smoothing strategy were introduced to balance the exploration and the exploitation of search process. A heuristic algorithm and a very fast simulated annealing algorithm were proposed to solve the single satellite scheduling problem. The task assignment scheme was valued by integrating the observation scheduling result of multiple satellites. The result was responded to the ant colony optimization algorithm, which can guide the search process of ant colony optimization. Computation results showed that the approach was effective to the satellites observation scheduling problem.

  12. An Analysis and Modeling Study of a Sea Fog Event over the Yellow and Bohai Seas

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this study, a sea fog event which occurred on 27 March 2005 over the Yellow and Bohai Seas was investigated observationally and numerically. Almost all available observational data were used, including satellite imagery of Geostationary Operational Environmental Satellite (GOES)-9, three data sets from station observations at Dandong, Dalian and Qingdao, objectively reanalyzed data of final run analysis (FNL) issued by the National Center for Environmental Prediction (NCEP) and Regional Atmospheric Modeling System (RAMS) results. Synoptic conditions and fog characteristics were analyzed. The fog formed when warm,moist air was advected northwards over the cool water of the Yellow and Bohai Seas, and dissipated when a cold front brought northerly winds and cool, dry air. In order to better understand the fog formation mechanism, a high-resolution RAMS modeling with a 6km×6km grid, initialized and validated by FNL data, was designed. A 48h modeling that started from 12 UTC 26 March 2005reproduced the main characteristics of this sea fog event. The simulated lower visibility area agreed reasonably well with the sea fog region identified from the satellite imagery. Advection cooling effect seemed to play a significant role in the fog formation.

  13. Pilot Scale Advanced Fogging Demonstration

    Energy Technology Data Exchange (ETDEWEB)

    Demmer, Rick L. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Fox, Don T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Archiblad, Kip E. [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-01-01

    Experiments in 2006 developed a useful fog solution using three different chemical constituents. Optimization of the fog recipe and use of commercially available equipment were identified as needs that had not been addressed. During 2012 development work it was noted that low concentrations of the components hampered coverage and drying in the United Kingdom’s National Nuclear Laboratory’s testing much more so than was evident in the 2006 tests. In fiscal year 2014 the Idaho National Laboratory undertook a systematic optimization of the fogging formulation and conducted a non-radioactive, pilot scale demonstration using commercially available fogging equipment. While not as sophisticated as the equipment used in earlier testing, the new approach is much less expensive and readily available for smaller scale operations. Pilot scale testing was important to validate new equipment of an appropriate scale, optimize the chemistry of the fogging solution, and to realize the conceptual approach.

  14. Comparison of sodium hypochlorite-based foam and peroxyacetic acid-based fog sanitizing procedures in a salmon smokehouse: Survival of the general microflora and Listeria monocytogenes

    DEFF Research Database (Denmark)

    Bagge, Dorthe; Gardshodn, K.; Gram, Lone

    2003-01-01

    in the composition of the flora, with Pseudomonas spp. and Alcaligenes spp. being the dominant gram- negative bacteria and Kurthia spp. and Bacillus spp. being the surviving gram-positive bacteria. Bacteria were very sensitive to fog sanitization, and yeasts accounted for almost half of the surviving flora...

  15. SAW based systems for mobile communications satellites

    Science.gov (United States)

    Peach, R. C.; Miller, N.; Lee, M.

    1993-01-01

    Modern mobile communications satellites, such as INMARSAT 3, EMS, and ARTEMIS, use advanced onboard processing to make efficient use of the available L-band spectrum. In all of these cases, high performance surface acoustic wave (SAW) devices are used. SAW filters can provide high selectivity (100-200 kHz transition widths), combined with flat amplitude and linear phase characteristics; their simple construction and radiation hardness also makes them especially suitable for space applications. An overview of the architectures used in the above systems, describing the technologies employed, and the use of bandwidth switchable SAW filtering (BSSF) is given. The tradeoffs to be considered when specifying a SAW based system are analyzed, using both theoretical and experimental data. Empirical rules for estimating SAW filter performance are given. Achievable performance is illustrated using data from the INMARSAT 3 engineering model (EM) processors.

  16. Global Ocean Surveillance With Electronic Intelligence Based Satellite System

    Science.gov (United States)

    Venkatramanan, Haritha

    2016-07-01

    The objective of this proposal is to design our own ELINT based satellite system to detect and locate the target by using satellite Trilateration Principle. The target position can be found by measuring the radio signals arrived at three satellites using Time Difference of Arrival(TDOA) technique. To locate a target it is necessary to determine the satellite position. The satellite motion and its position is obtained by using Simplified General Perturbation Model(SGP4) in MATLAB. This SGP4 accepts satellite Two Line Element(TLE) data and returns the position in the form of state vectors. These state vectors are then converted into observable parameters and then propagated in space. This calculations can be done for satellite constellation and non - visibility periods can be calculated. Satellite Trilateration consists of three satellites flying in formation with each other. The satellite constellation design consists of three satellites with an inclination of 61.3° maintained at equal distances between each other. The design is performed using MATLAB and simulated to obtain the necessary results. The target's position can be obtained using the three satellites ECEF Coordinate system and its position and velocity can be calculated in terms of Latitude and Longitude. The target's motion is simulated to obtain the Speed and Direction of Travel.

  17. 33 CFR 118.130 - Fog signals.

    Science.gov (United States)

    2010-07-01

    ... 33 Navigation and Navigable Waters 1 2010-07-01 2010-07-01 false Fog signals. 118.130 Section 118... LIGHTING AND OTHER SIGNALS § 118.130 Fog signals. On waterways where visibility is frequently reduced due... more fog signals to warn the navigator of the presence of the bridge. The fog signals must conform to...

  18. Impact of Reduced Visibility from Fog on Traffic Sign Detection

    OpenAIRE

    Belaroussi, Rachid; Gruyer, Dominique

    2014-01-01

    In camera-based Advance Driver Assistance System (ADAS) such as traffic sign recognition, some failure may be inferred by adverse meteorological conditions, in particular under foggy weather. This paper investigates the effects of reduced visibility from fog in an ADAS operating range, more specifically a traffic sign detection algorithm. For this purpose, we produced a database of synthetic images containing road signs with and without fog, that is intended to be shared with the scientific c...

  19. Fog research in China: An overview

    Science.gov (United States)

    Niu, Shengjie; Lu, Chunsong; Yu, Huaying; Zhao, Lijuan; Lü, Jingjing

    2010-05-01

    Fog can adversely affect human activity directly and indirectly, resulting in large losses both in terms of the local economy and lives. Much effort has been devoted to studies of fog across many areas of China, and in that context this paper aims to summarize climatic characteristics and review fog field experiments and their major results relating to fog mechanisms, physical properties and chemical characteristics. Progress in the application of remote sensing techniques and numerical simulation in fog research are also discussed. In particular, the effects of urbanization and industrialization on fog are highlighted. To end, perspectives on future fog research are outlined. The goal of this review paper is to introduce fog research in China to the global academic community and thus promote international collaboration on fog research. This is important because most papers on fog in China are published in Chinese, which are unreadable for the vast majority of non-Chinese researchers.

  20. The Potential for Scaling Up a Fog Collection System on the Eastern Escarpment of Eritrea

    Directory of Open Access Journals (Sweden)

    Mussie Fessehaye

    2015-11-01

    Full Text Available Fog is an untapped natural resource. A number of studies have been undertaken to understand its potential as an alternative or complementary water source. In 2007, a pilot fog-collection project was implemented in 2 villages on the Eastern Escarpment of Eritrea. The government of Eritrea, buoyed by the project’s positive results, has encouraged research into and application of fog-collection technologies to alleviate water-supply problems in this region. In 2014, this study was undertaken to assess the coverage, prevalence, intensity, and seasonality of fog on the Eastern Escarpment of Eritrea and consequently to identify potential beneficiary villages. Three independent methods used in the study—satellite image analyses, personal interviews, and a standard fog collector—produced reasonably similar characterizations of fog coverage and timing. The period with high fog incidence is mainly between November and March, with the highest number of fog days per year (96 on the central Eastern Escarpment and decreasing frequency to the south (78 days and north (73 days. The fog intensity on the central Eastern Escarpment is very high and in most cases reduces visibility to less than 500 m. In this period, a light to moderate breeze blows predominantly from the north and northeast. More than half of the villages in the region currently have a reliable water-supply system. The rest depend on seasonal roof-water harvesting, rock-water harvesting, and truck delivery and, therefore, could potentially benefit from fog collection as a supplementary water source. In particular, fog water could be useful for a small number of beneficiaries, including public services like schools and health facilities, where conventional water-delivery systems are not viable.

  1. Definition Method of Fog Factor Based on Vertex Shader%基于顶点着色器的雾化因子定义方法

    Institute of Scientific and Technical Information of China (English)

    王彦

    2011-01-01

    Fog effect can enhance the realism and distance of scene. Linear, exponential and exponential-squared fog parameters are enumerated in Direct3D, and they make the real-time rendering rapid and convenient, however, the various transformations of fog are limited by the only three parameters. Fog factor is the key to define the formula of parameters, and vertex shader has the ability to render vertex separately. This paper discusses a way to reconstruct the formula of fog factor by combination of the features above, gives an example, which can implement the fog effect according to the altitude of scene, the distance between observer and scene and the density of fog. Experimental results show that the restriction of original parameters can be improved in this way, and fog effect in reality can be imitated freely.%Direct3D提供的线性、指数与指数平方3种雾化参数可便捷地渲染场景,但仅有的参数限制了雾化的多样性.雾化因子在定义参数的公式中起决定作用,顶点着色器则具有单独渲染顶点的能力.为此,结合两者特性,提出一种雾化因子定义方法,并给出一个根据顶点高度、观察距离及雾的密度产生雾化效果的实例.实验结果表明,该方法突破了原有参数的限制,能灵活模拟现实中的雾化环境.

  2. Exploring microphysical, radiative, dynamic and thermodynamic processes driving fog and low stratus clouds using ground-based Lidar and Radar measurements

    Science.gov (United States)

    Haeffelin, Martial

    2016-04-01

    Radiation fog formation is largely influenced by the chemical composition, size and number concentration of cloud condensation nuclei and by heating/cooling and drying/moistening processes in a shallow mixing layer near the surface. Once a fog water layer is formed, its development and dissipation become predominantly controlled by radiative cooling/heating, turbulent mixing, sedimentation and deposition. Key processes occur in the atmospheric surface layer, directly in contact with the soil and vegetation, and throughout the atmospheric column. Recent publications provide detailed descriptions of these processes for idealized cases using very high-resolution models and proper representation of microphysical processes. Studying these processes in real fog situations require atmospheric profiling capabilities to monitor the temporal evolution of key parameters at several heights (surface, inside the fog, fog top, free troposphere). This could be done with in-situ sensors flown on tethered balloons or drones, during dedicated intensive field campaigns. In addition Backscatter Lidars, Doppler Lidars, Microwave Radiometers and Cloud Doppler Radars can provide more continuous, yet precise monitoring of key parameters throughout the fog life cycle. The presentation will describe how Backscatter Lidars can be used to study the height and kinetics of aerosol activation into fog droplets. Next we will show the potential of Cloud Doppler Radar measurements to characterize the temporal evolution of droplet size, liquid water content, sedimentation and deposition. Contributions from Doppler Lidars and Microwave Radiometers will be discussed. This presentation will conclude on the potential to use Lidar and Radar remote sensing measurements to support operational fog nowcasting.

  3. Analysis of an extremely dense regional fog event in Eastern China using a mesoscale model

    Science.gov (United States)

    Shi, Chune; Yang, Jun; Qiu, Mingyan; Zhang, Hao; Zhang, Su; Li, Zihua

    2010-03-01

    An unusually dense regional advection-radiation fog event over Anhui and the surrounding provinces in eastern China during Dec. 25-27, 2006, was investigated. At its mature stage, the fog covered most Anhui and parts of the surrounding provinces, reducing visibility to 100 m or less. It lasted more than 36 consecutive hours in some places. A mesoscale meteorological model (MM5), together with back-trajectory analysis, was used to investigate this fog event. The observations from a field station as well as hundreds of routine stations, along with two sets of visibility computing methods, were used to quantitatively and objectively validate the MM5 simulated liquid water content (LWC) and visibility. The verifications demonstrate that MM5 has a better fog predictability for the first day compared to the second day forecast, and better fog predictability compared to dense fog predictability with regard to the probability of detection (POD) and the threat score (TS). The new visibility algorithm that uses both LWC and number density of fog droplets significantly outperforms the conventional LWC-only based one in the fog prediction in terms of the POD score, especially for dense fog prediction. The objective verification in this work is the first time conducted for MM5 fog prediction, with which we can better understand the performance of simulated temporal and spatial fog coverage. The back-trajectory and sensitivity experiments confirm that subsidence and the steady warm and moist advections from southeast and southwest maintained the dense fog while the northwesterly dry wind resulted in dissipation of the fog.

  4. Fog Collection and Sustainable Architecture in Atacama Coast

    Science.gov (United States)

    Suau, C.

    2010-07-01

    It is imperative to integrate renewable energy and climate into zero-carbon buildings in arid lands, particularly when it is reinforced by natural and social science-based innovation in natural and built environs. The aim is twofold: On one hand, to establish potential natural and urban habitats and their yields required in different scales of intervention and, on another hand, augment rate and yield of fog collection used for drinking and irrigation in chosen locations. The purpose of this study is to integrate zero-carbon energy, landscape and sustainable architecture as a whole and thus envision potential inhabitation through self-sufficient space-frame configurations along the coast of Tarapacá Region in Chile. In a sequential way, this study distinguishes three scales of interventions: A. Territorial scale. It consists of rural and natural zones along the shore of Tarapacá Region: Fog oases, creeks or corridors. The strategic allocation of large fog collectors can bring local agriculture back and thus stop rural emigration; and also repair existing fragile ecosystems in several fog oases by harvesting and distributing mainly crop water. B. Local scale. The space-frame fog collectors are allocated in Alto Patache (fog oasis) and Iquique city (low-income sprawl of Alto Hospicio). These artefacts can supply both water and electricity to small communities through forestation, sustainable micro-agriculture and complementary electrification. C. Domestic scale. It consists of the design of autonomous housing configuration based in polygonal space-frames. This inhabitable unit is modular, deployable and lightweight; with an adjustable polyvalent membrane which performs as water repellent skin (facing South and SW winds) and shading device facing Equator. In addition, a domestic wind turbine is installed within the structural frame to provide autonomous electrification. Water collector, filtering (purification) and irrigation network is designed with available

  5. An Overview of the MATERHORN Fog Project: Observations and Predictability

    Science.gov (United States)

    Gultepe, I.; Fernando, H. J. S.; Pardyjak, E. R.; Hoch, S. W.; Silver, Z.; Creegan, E.; Leo, L. S.; Pu, Zhaoxia; De Wekker, S. F. J.; Hang, Chaoxun

    2016-09-01

    A field campaign design to study fog processes in complex terrain was a component of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) Program. The experiment was conducted in the Wasatch Mountains during January 5-February 15, 2015. Fog and in particular, Ice fog (IF), defined as fog composed of only ice crystals, was studied during a part of the campaign, and this component of the program was dubbed MATERHORN-Fog. Ice fog often occurs in mountainous regions due do rapid cooling, such as radiative cooling, advective cooling, and cooling associated with mountain circulations (e.g., slope and valley winds). A variety of major instrument platforms were deployed, which included meteorological towers, a SODAR, a LiDAR, ceilometers, and a tethersonde profiler. In addition, in situ measurements took place at several locations surrounding Salt Lake City and Heber City. During the campaign, ice fog occurred at temperatures below -5 °C down to -13 °C and lasted for several hours until radiative heating became significant. The visibility (Vis) during ice fog events ranged from 100 m up to 10 km. At the Heber City site an array of sensors for measuring microphysical, radiative, and dynamical characteristics of IF events were deployed. Some local effects such as upslope advection were observed to affect the IF conditions. As expected during these events, ice water content (IWC) varied from 0.01 up to 0.2 g m-3, with radiative cooling fluxes as strong as 200 W m-2; turbulent heat and moisture fluxes were significantly lower during fog events than those of fog dissipation. At times, the measured ice crystal number concentration was as high as 100 cm-3 during periods of saturation with respect to ice. N i was not a constant as usually assumed in forecasting simulations, but rather changed with increasing IWC. Measurement based statistics suggested that the occurrence of IF events in the region was up to 30 % during the study period in the winter of 2015

  6. Satellite-Based EMI Detection, Identification, and Mitigation

    Science.gov (United States)

    Stottler, R.; Bowman, C.

    2016-09-01

    Commanding, controlling, and maintaining the health of satellites requires a clear operating spectrum for communications. Electro Magnetic Interference (EMI) from other satellites can interfere with these communications. Determining which satellite is at fault improves space situational awareness and can be used to avoid the problem in the future. The Rfi detection And Prediction Tool, Optimizing Resources (RAPTOR) monitors the satellite communication antenna signals to detect EMI (also called RFI for Radio Frequency Interference) using a neural network trained on past cases of both normal communications and EMI events. RAPTOR maintains a database of satellites that have violated the reserved spectrum in the past. When satellite-based EMI is detected, RAPTOR first checks this list to determine if any are angularly close to the satellite being communicated with. Additionally, RAPTOR checks the Space Catalog to see if any of its active satellites are angularly close. RAPTOR also consults on-line databases to determine if the described operating frequencies of the satellites match the detected EMI and recommends candidates to be added to the known offenders database, accordingly. Based on detected EMI and predicted orbits and frequencies, RAPTOR automatically reschedules satellite communications to avoid current and future satellite-based EMI. It also includes an intuitive display for a global network of satellite communications antennas and their statuses including the status of their EM spectrum. RAPTOR has been prototyped and tested with real data (amplitudes versus frequency over time) for both satellite communication signals and is currently undergoing full-scale development. This paper describes the RAPTOR technologies and results of testing.

  7. Observer-based Satellite Attitude Control and Simulation Researches

    Institute of Scientific and Technical Information of China (English)

    王子才; 马克茂

    2002-01-01

    Observer design method is applied to the realization of satellite attitude control law baaed on simplified control model. Exact mathematical model of the satellite attitude control system is also constructed, together with the observer-based control law, to conduct simulation research. The simulation results justify the effectiveness andfeasibility of the observer-based control method.

  8. Comparison of sodium hypochlorite-based foam and peroxyacetic acid-based fog sanitizing procedures in a salmon smokehouse: Survival of the general microflora and Listeria monocytogenes

    DEFF Research Database (Denmark)

    Bagge, Dorthe; Gardshodn, K.; Gram, Lone

    2003-01-01

    sample, and a total of 288 bacterial strains were randomly isolated and tentatively identified to genus level by physiological and biochemical tests. The microflora was dominated by Neisseriaceae, Enterobacteriaceae, and lactic acid bacteria during production. Foam sanitization caused a change......The effects of fog sanitization with peroxyacetic acid (hydrogen peroxide, peracetic acid, and acetic acid in combination) on general hygiene (aerobic plate count) and on Listeria monocytogenes were assessed in a slicing area at a salmon smokehouse and compared with the effects of foam sanitization...... in the composition of the flora, with Pseudomonas spp. and Alcaligenes spp. being the dominant gram- negative bacteria and Kurthia spp. and Bacillus spp. being the surviving gram-positive bacteria. Bacteria were very sensitive to fog sanitization, and yeasts accounted for almost half of the surviving flora...

  9. A kind of integrated method discuss of fOG signal processing circuit

    Science.gov (United States)

    Lu, Jun; Pan, Xin; Ying, Jiaju; Liu, Jie

    2014-12-01

    In view of the circuit miniaturization need in project application of fiber optic gyroscope(FOG), a new integrated technical scheme adopting system in package(SIP) for signal processing circuit of FOG was put forward. At first, the principle on signal processing circuit of FOG was analyzed, and the technical scheme adopting SIP based on low-temperature co-fired substrate technology was presented according to circuit characteristic and actual condition. Secondly, under the prerequisite of the concept introduction of SIP and LTCC, the SIP prototype of signal processing circuit of FOG was trialed produced,and it passed through the debug test. This SIP modular is an overall circuit complete integrated the signal processing circuit of FOG, and only a potentiometer and EPROM do not case outside. The testing results indicate that SIP is a kind of feasible scheme that carries out miniaturization for signal processing circuit of FOG.

  10. Fog water chemistry in Shanghai

    Science.gov (United States)

    Li, Pengfei; Li, Xiang; Yang, Chenyu; Wang, Xinjun; Chen, Jianmin; Collett, Jeffrey L., Jr.

    2011-08-01

    With the aim of understanding the fog chemistry in a Chinese megacity, twenty-six fog water samples were collected in urban Shanghai from March 2009 to March 2010. The following parameters were measured: pH, electrical conductivity (EC), ten inorganic major ions ( SO42-, NO3-, NO2-, F -, Cl -, Na +, K +, Ca 2+, Mg 2+, NH4+) and four major organic acids (CH 3COO -, HCOO -, CO42-, MSA). The total ionic concentration (TIC) and EC of fog samples were one or two orders of magnitude higher than those often found in Europe, North America and other Asian countries. Pollutants were expected to be mainly from local sources, including factories, motor vehicle emissions and civil construction. Non-local sources such as moderate- and long-range transport of sea salt also contributed to pollution levels in fog events as indicated by back trajectory analysis. The pH of the fog water collected during the monitoring period varied from 4.68 to 6.58; acidic fogs represented about 30.8% of the total fog events during this period. The fog water was characterized by high concentrations of SO42- (20.0% of measured TIC), NO3- (17.1%), NH4+ (28.3%) and Ca 2+ (14.4%). SO42- and NO3-, the main precursors of fog acidity, were related to burning fossil fuels and vehicle emissions, respectively. NH4+, originating from the scavenging of gaseous ammonia and particulate ammonium nitrate and ammonium sulfate, and Ca 2+, originating from the scavenging of coarse particles, acted as acid neutralizers and were the main cause for the relatively high pH of fogs in Shanghai. The ratio of ( SO42- + NO3-)/( NH4+ + Ca 2+) was lower than 1, indicating the alkaline nature of the fog water. A high ratio of NO3-/ SO42- and low ratio of HCOO -/CH 3COO - were consistent with large contributions from vehicular emissions that produce severe air pollution in megacities.

  11. Methylmercury and other chemical constituents in Pacific coastal fog water from seven sites in Central/Northern California (FogNet) during the summer of 2014

    Science.gov (United States)

    Weiss-Penzias, P. S.; Heim, W. A.; Fernandez, D.; Coale, K. H.; Oliphant, A. J.; Dann, D.; Porter, M.; Hoskins, D.; Dodge, C.

    2014-12-01

    This project investigates the mercury content in summertime Pacific coastal fog in California and whether fog could be an important vector for ocean emissions of mercury to be deposited via fog drip to upland coastal ecosystems. Efforts began in early 2014 with the building of 7 active-strand fog collectors based on the Colorado State University Caltech CASCC design. The new UCSC CASCC includes doors sealing the collector which open under microcomputer control based on environmental sensing (relative humidity). Seven sites spanning from Trinidad in the north to Marina in the south have collected samples June-August 2014 under a project called FogNet. Fog conditions were favorable for collecting large water volumes (> 250 mL) at many sites. Fog samplers were cleaned with soap and deionized water daily and field blanks taken immediately following cleaning. Fog water samples were collected overnight, split into an aliquot for anion and DOC/DIC analysis and the remaining sample was acidified. Monomethyl mercury (MMHg) concentrations in samples and field blanks for 3 sites in FogNet are shown in the accompanying figure. The range of MMHg concentrations from 10 fog water samples > 100 mL in volume was 0.9-9.3 ng/L (4.5-46.4 pM). Elevated MMHg concentrations (> 5 ng/L, 25 pM) were observed at 2 sites: UC Santa Cruz and Bodega Bay. The field blanks produced MMHg concentrations of 0.08-0.4 ng/L (0.4-2.0 pM), which was on average operations (summer 2014) reveal surface waters that were supersaturated in DMHg which represents a potential source of organic mercury to the overlying fog bank.

  12. System refinement for content based satellite image retrieval

    Directory of Open Access Journals (Sweden)

    NourElDin Laban

    2012-06-01

    Full Text Available We are witnessing a large increase in satellite generated data especially in the form of images. Hence intelligent processing of the huge amount of data received by dozens of earth observing satellites, with specific satellite image oriented approaches, presents itself as a pressing need. Content based satellite image retrieval (CBSIR approaches have mainly been driven so far by approaches dealing with traditional images. In this paper we introduce a novel approach that refines image retrieval process using the unique properties to satellite images. Our approach uses a Query by polygon (QBP paradigm for the content of interest instead of using the more conventional rectangular query by image approach. First, we extract features from the satellite images using multiple tiling sizes. Accordingly the system uses these multilevel features within a multilevel retrieval system that refines the retrieval process. Our multilevel refinement approach has been experimentally validated against the conventional one yielding enhanced precision and recall rates.

  13. Radio occultation based on BeiDou satellite navigation

    Science.gov (United States)

    Jiang, Hu; Hu, Haiying; Shen, Xue-min; Gong, Wenbin; Zhang, Yonghe

    2014-11-01

    With the development of GNSS systems, it has become a tendency that radio occultation is used to sense the Earth's atmosphere. By this means, the moisture, temperature, pressure, and total electron content can be derived. Based on the sensing results, more complicated models for atmosphere might come into being. Meteorology well benefits from this technology. As scheduled, the BD satellite navigation system will have a worldwide coverage by the end of 2020. Radio occultation studies in China have been highlighted in the recent decade. More and more feasibilities reports have been published in either domestic or international journals. Herein, some scenarios are proposed to assess the coverage of radio occultation based on two different phases of BD satellite navigation system. Phase one for BD is composed of GEO,IGSO and several MEO satellites. Phase two for BD consists mostly of 24 MEO satellites, some GEO and IGSO satellites. The characteristics of radio occultation based on these two phases are presented respectively.

  14. Satellite based wind resource assessment over the South China Sea

    DEFF Research Database (Denmark)

    Badger, Merete; Astrup, Poul; Hasager, Charlotte Bay

    2014-01-01

    modeling to develop procedures and best practices for satellite based wind resource assessment offshore. All existing satellite images from the Envisat Advanced SAR sensor by the European Space Agency (2002-12) have been collected over a domain in the South China Sea. Wind speed is first retrieved from...

  15. UAV Applications for Thermodynamic Profiling:Emphasis on Ice Fog Visibility

    Science.gov (United States)

    Gultepe, Ismail; Heymsfield, Andrew; Fernando, Joseph; hoch, sebastian; pardyjack, Eric; Boudala, faisal; Ware, Randolph

    2017-04-01

    Ice fog often occurs over the Arctic, in cold climates, and near mountainous regions about 30% of time when temperatures (T) drop to -10°C or below. Ice fog affects aviation operations, transportation, and local climate. Ice Nucleation (IN) and radiative cooling play an important role by controlling the intensity of ice fog conditions. Ice fog can also occur at T above -10°C, but close to 0°C it mainly occurs due to freezing of supercooled droplets that contain an IN. To better document ice fog conditions, observations from ice fog events of the Indirect and Semi-Direct Aerosol effects on Climate (ISDAC) project (Barrow, Alaska), Fog Remote Sensing And Modeling (FRAM) project (Yellowknife, Northwest Territories), and the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) project (Heber City, Utah), were analyzed. Difficulties in measuring small ice fog particles at low temperatures and low-level research aircraft flying restrictions prevent observations from aircraft within the atmospheric boundary layer. However, Unmanned Aerial Vehicles (UAVs) can be operated safely to measure IN number concentration, Relative Humidity with respect to ice (RHi), T, horizontal wind speed (Uh) and direction, visibility, and possibly even measuring ice crystal spectra below about 500 micron, to provide a method for future research of ice fog. In this study, thermodynamic profiling was conducted using a Radiometrics Microwave Radiometer (PMWR) and Vaisala CL51 ceilometer to describe vertical spatial and temporal development of ice fog conditions. Overall, ice fog characteristics and its thermodynamic environment will be presented using both ground-based and airborne platforms such as a UAV with new sensors. Some examples of measurements from the UAV and a DMT GCIP (Droplet Measurement Technologies Ground Cloud Imaging Probe), and challenges related to both ice fog measurements and visibility parameterization will also be presented.

  16. 基于移动模板的图像去雾方法研究%Study of removing fog from images based on moving mask

    Institute of Scientific and Technical Information of China (English)

    曲艺

    2013-01-01

    Fog degrades images greatly, and many methods have been used to enhance foggy images. This paper analyzes the defect of global histogram equalization, presents an improved local equalization method based on moving mask, discusses the selection of mask size and its moving step, and provides a solution to potential block effect. It is proven that this method can enhance foggy images effectively, and it is easy to implement.%雾使图像退化严重,已有多种方法应用于图像去雾。分析了直方图均衡化方法在图像去雾方面的缺点,提出了一种改进的基于移动模板的局部重叠直方图均衡化去雾方法,分析了模板大小和移动步长对实验效果的影响,对可能出现的块效应提出了简单的滤波平滑算法。实验证明,该方法能够在增强图像的同时有效去雾,降低对图像的影响,且实现简单。

  17. 雾无线接入网:架构、原理和挑战%Fog computing based radio access networks: architecture, principles and challenges

    Institute of Scientific and Technical Information of China (English)

    尹博南; 艾元; 彭木根

    2016-01-01

    为了降低前传(fronthaul)链路开销、避免传统云无线接入网基带单元池中无线信号处理大规模/高实时要求、充分利用边缘网络设备的计算和存储能力,提出了雾无线接入网络(fog computing based radio access network,F-RAN),作为异构云无线接入网络的演进.F-RAN的核心是利用用户和边缘网络设备的计算和存储功能,进行本地业务分发、分布式信号处理和分布式资源管理等.详细介绍了F-RAN的系统架构、关键技术及未来需研究的问题.

  18. Digital evaluation of the influence of interruption of the fixation process on radiographic contrast and base-plus-fog density in three commercial brands of radiographic films

    Directory of Open Access Journals (Sweden)

    Paula Verona Ragusa da Silva

    Full Text Available INTRODUCTION : With the interest in anticipating access to the result of intraoral radiography, the radiographic processing is frequently neglected, compromising image quality. OBJECTIVE : The aim of this study was to evaluate the influence of interrupting the fixation process on the radiographic contrast and base-plus-fog density (BPFD in three brands of periapical films. MATERIAL AND METHOD : Ninety radiographs were taken of an aluminum stepwedge and a lead plate for each brand, and they were divided according to the time of initial immersion in the fixative in: control group (without interrupting the fixing, 5, 10, 20, 30 and 40 seconds. During processing, films had the fixing stage stopped and were exposed to a negatoscope for 1 minute, then the fixation time of 10 minutes was completed. The radiographs were digitized and exported to Image Tool 3.0.software. RESULT : Kodak(r film showed no statistically significant differences between groups, while Agfa(r film presented difference in BPFD compared with Group 5 seconds, and Dentix(r film showed statistical difference in all groups in comparison with the control group. CONCLUSION : Under the conditions studied, Kodak(r film is not influenced by disruption of fixation as regards BPFD and image contrast, enabling early access to the results of radiographs, whereas Agfa(r film requires at least 10 seconds of initial fixation, and Dentix(r film obtains better results when the process of fixation is not interrupted.

  19. Global trends in satellite-based emergency mapping.

    Science.gov (United States)

    Voigt, Stefan; Giulio-Tonolo, Fabio; Lyons, Josh; Kučera, Jan; Jones, Brenda; Schneiderhan, Tobias; Platzeck, Gabriel; Kaku, Kazuya; Hazarika, Manzul Kumar; Czaran, Lorant; Li, Suju; Pedersen, Wendi; James, Godstime Kadiri; Proy, Catherine; Muthike, Denis Macharia; Bequignon, Jerome; Guha-Sapir, Debarati

    2016-07-15

    Over the past 15 years, scientists and disaster responders have increasingly used satellite-based Earth observations for global rapid assessment of disaster situations. We review global trends in satellite rapid response and emergency mapping from 2000 to 2014, analyzing more than 1000 incidents in which satellite monitoring was used for assessing major disaster situations. We provide a synthesis of spatial patterns and temporal trends in global satellite emergency mapping efforts and show that satellite-based emergency mapping is most intensively deployed in Asia and Europe and follows well the geographic, physical, and temporal distributions of global natural disasters. We present an outlook on the future use of Earth observation technology for disaster response and mitigation by putting past and current developments into context and perspective.

  20. Global trends in satellite-based emergency mapping

    Science.gov (United States)

    Voigt, Stefan; Giulio-Tonolo, Fabio; Lyons, Josh; Kučera, Jan; Jones, Brenda; Schneiderhan, Tobias; Platzeck, Gabriel; Kaku, Kazuya; Hazarika, Manzul Kumar; Czaran, Lorant; Li, Suju; Pedersen, Wendi; James, Godstime Kadiri; Proy, Catherine; Muthike, Denis Macharia; Bequignon, Jerome; Guha-Sapir, Debarati

    2016-01-01

    Over the past 15 years, scientists and disaster responders have increasingly used satellite-based Earth observations for global rapid assessment of disaster situations. We review global trends in satellite rapid response and emergency mapping from 2000 to 2014, analyzing more than 1000 incidents in which satellite monitoring was used for assessing major disaster situations. We provide a synthesis of spatial patterns and temporal trends in global satellite emergency mapping efforts and show that satellite-based emergency mapping is most intensively deployed in Asia and Europe and follows well the geographic, physical, and temporal distributions of global natural disasters. We present an outlook on the future use of Earth observation technology for disaster response and mitigation by putting past and current developments into context and perspective.

  1. Global trends in satellite-based emergency mapping

    Science.gov (United States)

    Voigt, Stefan; Giulio-Tonolo, Fabio; Lyons, Josh; Kučera, Jan; Jones, Brenda; Schneiderhan, Tobias; Platzeck, Gabriel; Kaku, Kazuya; Hazarika, Manzul Kumar; Czaran, Lorant; Li, Suju; Pedersen, Wendi; James, Godstime Kadiri; Proy, Catherine; Muthike, Denis Macharia; Bequignon, Jerome; Guha-Sapir, Debarati

    2016-07-01

    Over the past 15 years, scientists and disaster responders have increasingly used satellite-based Earth observations for global rapid assessment of disaster situations. We review global trends in satellite rapid response and emergency mapping from 2000 to 2014, analyzing more than 1000 incidents in which satellite monitoring was used for assessing major disaster situations. We provide a synthesis of spatial patterns and temporal trends in global satellite emergency mapping efforts and show that satellite-based emergency mapping is most intensively deployed in Asia and Europe and follows well the geographic, physical, and temporal distributions of global natural disasters. We present an outlook on the future use of Earth observation technology for disaster response and mitigation by putting past and current developments into context and perspective.

  2. On Study of Sea Fog over the Yellow and Bohai Seas in China

    Science.gov (United States)

    Fu, G.; Gao, S.; Yang, Y.; Xu, X.; Wang, X.; Chen, Y.; Xue, D.; Shen, J.

    2010-07-01

    A ubiquitous feature of the Yellow and Bohai Sea (YBS) in the eastern Asian region is the frequent occurrence of the sea fog in spring and summer season. The pioneer work on sea fog over YBS can be traced back to Prof. Binhua Wang as early as 1940's. He investigated sea fog systematically and published his book Sea Fog in 1985 (by China Ocean Press and Springer-Verlag). Recently, a research group in the Department of Marine Meteorology at Ocean University of China (OUC) continued sea fog research collaborated with Shandong Meteorological Bureau and Qingdao Meteorological Bureau under the financial supports of National Natural Science Foundation of China and China Meteorological Administration. Their researches involved in both observation analyses and high-resolution modeling of sea fog over YBS. In this talk, the brief history of sea fog research in China will be reviewed firstly. Then, a typical heavy sea fog event over YBS occurred in the morning of 11 April 2004 will be documented by using all available observational data and high-resolution Regional Atmospheric Modeling System (RAMS) modeling results. Finally, the applications of a quasi-operational sea fog forecasting system which was mainly based on RAMS model will be introduced.

  3. Crash risk analysis during fog conditions using real-time traffic data.

    Science.gov (United States)

    Wu, Yina; Abdel-Aty, Mohamed; Lee, Jaeyoung

    2017-05-30

    This research investigates the changes of traffic characteristics and crash risks during fog conditions. Using real-time traffic flow and weather data at two regions in Florida, the traffic patterns at the fog duration were compared to the traffic patterns at the clear duration. It was found that the average 5-min speed and the average 5-min volume were prone to decreasing during fog. Based on previous studies, a "Crash Risk Increase Indicator (CRII)" was proposed to explore the differences of crash risk between fog and clear conditions. A binary logistic regression model was applied to link the increase of crash risks with traffic flow characteristics. The results suggested that the proposed indicator worked well in evaluating the increase of crash risk under fog condition. It was indicated that the crash risk was prone to increase at ramp vicinities in fog conditions. Also, the average 5-min volume during fog and the lane position are important factors for crash risk increase. The differences between the regions were also explored in this study. The results indicated that the locations with heavier traffic or locations at the lanes that were closest to the median in Region 2 were more likely to observe an increase in crash risks in fog conditions. It is expected that the proposed indicator can help identify the dangerous traffic status under fog conditions and then proper ITS technologies can be implemented to enhance traffic safety when the visibility declines. Copyright © 2017 Elsevier Ltd. All rights reserved.

  4. An Alarming Increase in Winter Fog Events Over Indo-Gangetic Plains of India

    Science.gov (United States)

    Srivastava, S. K., Sr.

    2016-12-01

    In the present study, an attempt was made to examine climatological characteristic of fog using ground based observations of meteorological parameters over Indo-Gangetic plains (IGP) of Indian subcontinent. Long term (1971-2010) trend is estimated for 30 stations of IGP and further, spatial and temporal variability of fog over the study area was also assessed using Geo-statistical tools. Differential fog prone areas has been identified using spatial cluster analysis, this approach is unique and help us to understand fog behavior more closely in the given region. Mann - Kendall statistical test and Kendall tau's statistics were used to explain temporal variability and trend analysis. Decadal time series analysis (1971-2010) revealed net overall significant increase of 99% over IGP. Additionally, geo-statistical analysis performed to extract spatial distribution characteristics, revealed that the IGP is high fog prone zone with fog occurrence frequency of more than 66 % days during the study period. Diurnal variability indicates the peak occurrence of fog is between 0600-0900hrs local time and average daily fog persistence extends to 5 to 7 hours during peak winter season. The results would offer new perspective to take proactive measures in reducing the irreparable damage that could be caused due to changing trends of fog.

  5. Numerical simulation of diurnally varying thermal environment in a street canyon under haze-fog conditions

    Science.gov (United States)

    Tan, Zijing; Dong, Jingliang; Xiao, Yimin; Tu, Jiyuan

    2015-10-01

    The impact of haze-fog on surface temperature, flow pattern, pollutant dispersion and pedestrian thermal comfort are investigated using computational fluid dynamics (CFD) approach based on a three-dimensional street canyon model under different haze-fog conditions. In this study, light extinction coefficient (Kex) is adopted to represent haze-fog pollution level. Numerical simulations are performed for different Kex values at four representative time events (1000 LST, 1300 LST, 1600 LST and 2000 LST). The numerical results suggest that the surface temperature is strongly affected by the haze-fog condition. Surface heating induced by the solar radiation is enhanced by haze-fog, as higher surface temperature is observed under thicker haze-fog condition. Moreover, the temperature difference between sunlit and shadow surfaces is reduced, while that for the two shadow surfaces is slightly increased. Therefore, the surface temperature among street canyon facets becomes more evenly distributed under heavy haze-fog conditions. In addition, flow patterns are considerably altered by different haze-fog conditions, especially for the afternoon (1600 LST) case, in which thermal-driven flow has opposite direction as that of the wind-driven flow direction. Consequently, pollutants such as vehicular emissions will accumulate at pedestrian level, and pedestrian thermal comfort may lower under thicker haze-fog condition.

  6. Mechanisms of fat, oil and grease (FOG) deposit formation in sewer lines.

    Science.gov (United States)

    He, Xia; de los Reyes, Francis L; Leming, Michael L; Dean, Lisa O; Lappi, Simon E; Ducoste, Joel J

    2013-09-01

    FOG deposits in sewer systems have recently been shown to be metallic salts of fatty acids. However, the fate and transport of FOG deposit reactant constituents and the complex interactions during the FOG deposit formation process are still largely unknown. In this study, batch tests were performed to elucidate the mechanisms of FOG deposit formation that lead to sanitary sewer overflows (SSOs). We report the first formation of FOG deposits on a concrete surface under laboratory conditions that mimic the formation of deposits in sewer systems. Results showed that calcium, the dominant metal in FOG deposits, can be released from concrete surfaces under low pH conditions and contribute to the formation process. Small amounts of additional oil to grease interceptor effluent substantially facilitated the air/water or pipe surface/water interfacial reaction between free fatty acids and calcium to produce surface FOG deposits. Tests of different fatty acids revealed that more viscous FOG deposit solids were formed on concrete surfaces, and concrete corrosion was accelerated, in the presence of unsaturated FFAs versus saturated FFAs. Based on all the data, a comprehensive model was proposed for the mechanisms of FOG deposit formation in sewer systems.

  7. Detection of nighttime sea fog/stratus over the Huanghai Sea using MTSAT-1R IR data

    Institute of Scientific and Technical Information of China (English)

    GAO Shanhong; WU Wei; ZHU Leilei; FU Gang; HUANG Bin

    2009-01-01

    A dual channel difference (DCD) method is applied to detect nighttime sea fog/stratus over the Huanghai Sea using the infrared (IR) data of shortwave (3.5-4.0 μm) and longwave (10.3-11.3 μm) channels from the Multi-functional Transport Satellite (MTSAT)-IR, i.e., shortwave minus longwave brightness temperature difference (SLTD). Twenty-four sea fog events over the Huanghai Sea during March to July of 2006 and 2007 are chosen to determine a suitable value of SLTD for nighttime sea fog/stratus detection, and it is found that the value of-5.5-2.5℃ can be taken as a criterion. Two case examples of sea fog events are especially demonstrated in detail utilizing the criterion, and the results show that the derived sea fog/stratus coverage is quite reasonable.This coverage information is very helpful to analyze the formation and evolution of sea fog/stratus during night and can provide sea fog researchers with observational evidences for model results verification. However, more efforts are needed to further obtain vertical extent information of sea. fog/stratus and attempt to discriminate between sea fog and stratus.

  8. Digital, Satellite-Based Aeronautical Communication

    Science.gov (United States)

    Davarian, F.

    1989-01-01

    Satellite system relays communication between aircraft and stations on ground. System offers better coverage with direct communication between air and ground, costs less and makes possible new communication services. Carries both voice and data. Because many data exchanged between aircraft and ground contain safety-related information, probability of bit errors essential.

  9. Model-based satellite image fusion

    DEFF Research Database (Denmark)

    Aanæs, Henrik; Sveinsson, J. R.; Nielsen, Allan Aasbjerg

    2008-01-01

    A method is proposed for pixel-level satellite image fusion derived directly from a model of the imaging sensor. By design, the proposed method is spectrally consistent. It is argued that the proposed method needs regularization, as is the case for any method for this problem. A framework for pixel...

  10. Delivery of satellite based broadband services

    Science.gov (United States)

    Chandrasekhar, M. G.; Venugopal, D.

    2007-06-01

    Availability of speedy communication links to individuals and organizations is essential to keep pace with the business and social requirements of this modern age. While the PCs have been continuously growing in processing speed and memory capabilities, the availability of broadband communication links still has not been satisfactory in many parts of the world. Recognizing the need to give fillip to the growth of broadband services and improve the broadband penetration, the telecom policies of different counties have placed special emphasis on the same. While emphasis is on the use of fiber optic and copper in local loop, satellite communications systems will play an important role in quickly establishing these services in areas where fiber and other communication systems are not available and are not likely to be available for a long time to come. To make satellite communication systems attractive for the wide spread of these services in a cost effective way special emphasis has to be given on factors affecting the cost of the bandwidth and the equipment. As broadband services are bandwidth demanding, use of bandwidth efficient modulation technique and suitable system architecture are some of the important aspects that need to be examined. Further there is a need to re-look on how information services are provided keeping in view the user requirements and broadcast capability of satellite systems over wide areas. This paper addresses some of the aspects of delivering broadband services via satellite taking Indian requirement as an example.

  11. Co-Channel Interference Mitigation Using Satellite Based Receivers

    Science.gov (United States)

    2014-12-01

    While there is some phase noise present in the continuous time-shifted signal, it is important to recognize that this signal is plotted over the [−π...NAVAL POSTGRADUATE SCHOOL MONTEREY, CALIFORNIA THESIS CO-CHANNEL INTERFERENCE MITIGATION USING SATELLITE BASED RECEIVERS by John E. Patterson...07-02-2012 to 12-19-2014 4. TITLE AND SUBTITLE CO-CHANNEL INTERFERENCE MITIGATION USING SATELLITE BASED RE- CEIVERS 5. FUNDING NUMBERS 6. AUTHOR(S

  12. Efficient chaotic based satellite power supply subsystem

    Energy Technology Data Exchange (ETDEWEB)

    Ramos Turci, Luiz Felipe [Technological Institute of Aeronautics (ITA), Sao Jose dos Campos, SP (Brazil)], E-mail: felipeturci@yahoo.com.br; Macau, Elbert E.N. [National Institute of Space Research (Inpe), Sao Jose dos Campos, SP (Brazil)], E-mail: elbert@lac.inpe.br; Yoneyama, Takashi [Technological Institute of Aeronautics (ITA), Sao Jose dos Campos, SP (Brazil)], E-mail: takashi@ita.br

    2009-10-15

    In this work, we investigate the use of the Dynamical System Theory to increase the efficiency of the satellite power supply subsystems. The core of a satellite power subsystem relies on its DC/DC converter. This is a very nonlinear system that presents a multitude of phenomena ranging from bifurcations, quasi-periodicity, chaos, coexistence of attractors, among others. The traditional power subsystem design techniques try to avoid these nonlinear phenomena so that it is possible to use linear system theory in small regions about the equilibrium points. Here, we show that more efficiency can be drawn from a power supply subsystem if the DC/DC converter operates in regions of high nonlinearity. In special, if it operates in a chaotic regime, is has an intrinsic sensitivity that can be exploited to efficiently drive the power subsystem over high ranges of power requests by using control of chaos techniques.

  13. Advancing Fog Effect on VRML and X3D Using Local Fog Density

    Institute of Scientific and Technical Information of China (English)

    Seongah Chin

    2004-01-01

    In this paper an improved fog effect algorithm in VRML and X3 D is presented with respect to expressing density. The fundamental idea in the approach is to adapt local fog density having influence on Iocal regions with various grades of fog density whereas existing VRML and X3 D only make use of global fog effect. Several filters for making different fog density are presented along with experiments showing the correctness of the proposed method.

  14. The influences of macro- and microphysical characteristics of sea-fog on fog-water chemical composition

    Science.gov (United States)

    Yue, Yanyu; Niu, Shengjie; Zhao, Lijuan; Zhang, Yu; Xu, Feng

    2014-05-01

    During a sea-fog field observation campaign on Donghai Island in the spring of 2011, fog-water, visibility, meteorological elements, and fog droplet spectra were measured. The main cations and anions in 191 fog-water samples were Na+, NH{4/+}, H+, NO{3/-}, Cl- and SO{4/2-}, and the average concentrations of cations and anions were 2630 and 2970 μeq L-1, respectively. The concentrations of Na+ and Cl- originated from the ocean were high. The enhancement of anthropogenic pollution might have contributed to the high concentration of NH{4/+}, H+, and NO{3/-}. The average values of pH and electrical conductivity (EC) were 3.34 and 505 μS cm-1, respectively, with a negative correlation between them. Cold fronts associated with cyclonic circulations promoted the decline of ion loadings. Air masses from coastal areas had the highest ion loadings, contrary to those from the sea. The ranges of wind speed, wind direction and temperature corresponding to the maximum total ion concentration (TIC) were 3.5-4 m s-1, 79°-90° and 21°C-22°C, respectively. In view of the low correlation coefficients, a new parameter Lr was proposed as a predictive parameter for TIC and the correlation coefficient increased to 0.74. Based on aerosol concentrations during the sea-fog cases in 2010, we confirmed that fog-water chemical composition also depended on the species and sizes of aerosol particles. When a dust storm passed through Donghai Island, the number concentration of large aerosol particles (with diameter > 1 μm) increased. This caused the ratio of Ca2+/Na+ in fog-water to increase significantly.

  15. FOG Output Drift Compensation Based on Temperature Gradients%基于温度梯度的光纤陀螺输出漂移补偿

    Institute of Scientific and Technical Information of China (English)

    张晓峰; 范华春; 梁宇

    2011-01-01

    理论上,采用四极对称法绕制的光纤线圈能很好抑制温度梯度对光纤陀螺的影响,实际上,由于结构加工不理想或石英缠绕引起自身的机械形变,使线圈内外的温度变化,从而导致陀螺输出速率误差.该文分析并给出了光纤陀螺输出速率误差与线圈内外温度差或温度梯度间的关系,提出了一种补偿光纤陀螺因温度变化而导致输出速率漂移误差的方法,尽管光纤陀螺因温度变化所导致的温度漂移不可避免,我们通过测量获取陀螺内部的温度梯度变化并计算出修正系数来对光纤陀螺的输出进行补偿修正,这种方法适合高精度陀螺温度变化较小或是低精度陀螺温度变化较大的情况,这种补偿方法对陀螺系统的硬件要求低,试验结果表明,该补偿方法能有效抑制光纤陀螺随温度变化而导致的漂移速率误差.%Theoretically, the effect of the temperature gradient on the fiber optic gyroscope (FOG) can be well suppressed by using the quadrupole winding. In fact, the imperfect structure or winding causing glass coil distortion leads to FOG output rate error when there are temperature changes between FOG housing and the sensor coil spool. This paper shows a relationship between FOG output rate error and temperature change or temperature gradients. A method of compensating the FOG output drift rate error caused by the temperature change has been proposed. As is known that FOG drift rate error due to rates of temperature change is almost unavoidable, but we can make some adjustments by acquiring temperature gradients in FOG and calculating the required correction factor. This method is suited to high accuracy FOG in which temperature changes are small or to low accuracy FOG when thermal disturb ances are relatively large. A best merit of this compensation method is its low requirements for the hardware. Test results demonstrate that the above mentioned compensation method can largely

  16. A Summary of Research on Sea Fog Forecasting%海雾预报研究综述

    Institute of Scientific and Technical Information of China (English)

    史得道; 吴振玲; 高山红; 罗凯

    2016-01-01

    A review of the research progress over the past few decades is presented here on the sea fog forecasting technique based upon statistical and numerical prediction. The statistical method is a major tool except the synoptic method on the sea fog forecast at coastal meteorological observatories in China. It improves the forecasts of sea fog but have defects of the empirical statistics. With the rapidly development of computer technology, the numerical simulation and prediction on sea fog events are applied widely and will become the main method. Nowadays, the sea fog numerical prediction models are developed from the one-dimensional to three-dimensional and from the single atmospheric model to coupled air-sea model. The advanced assimilation technique, which assimilates the satellite data to overcome the lack of marine observations, together with the ensemble prediction in the three-dimensional numerical prediction model, which uses a higher resolution, selects the most suitable boundary layer and physical parameterization schemes, will greatly improve the sea fog forecasts.%从统计预报和数值模拟预报两方面回顾了过去几十年国内在海雾预报技术上的主要研究进展。统计预报方法是中国沿海气象台站预报海雾的除天气学方法外的主要工具,一定程度上能提高海雾预报准确率,但无法摆脱自身经验统计的缺陷。随着计算机技术的飞速发展,海雾数值模拟和预报应用越来越广泛,并将成为海雾预报主流方法。海雾数值预报模式的发展经历了从一维到三维、从单一大气模式到海气耦合模式的过程。而研发先进的数据同化技术,同化更好的卫星资料弥补海上观测缺少的不足,选择最合适的边界层与微物理参数化方案,进行高分辨率三维数值模式集合预报,将使海雾预报准确率明显提高。

  17. Denoising algorithm for FOG based on adaptive time-frequency peak filtering%基于自适应时频峰值滤波的光纤陀螺去噪算法

    Institute of Scientific and Technical Information of China (English)

    顾姗姗; 刘建业; 曾庆化; 陈维娜; 陈磊江

    2014-01-01

    An algorithm based on adaptive time-frequency peak filtering(ATFPF) for fiber optical gyro(FOG) is proposed to reduce the noise of FOG and improve the precision of the inertial navigation system. With the presented algorithm, the FOG signal is transformed and modulated, and then time frequency analysis of the modulated signal is made by pseudo Wigner-Ville distribution(PWVD). A rule for the optimal window length selection of adaptive PWVD is given, and the instantaneous frequency of the coded signal is estimated by local peak search. In this way, the useful signal is restored and the noise of FOG is reduced. Simulation and real data are processed by discrete wavelet transform(DWT) and ATFPF algorithms separately, and the results show that proposed algorithm can reduce the noise of FOG effectively, and the improvement of SNR is 1~3 dB. The signal denoised by ATFPF can effectively track the initial signal, especially for the high dynamic signal.%为减小光纤陀螺输出信号噪声、提高惯导系统精度,提出了光纤陀螺信号自适应时频峰值滤波算法。对光纤陀螺信号进行初始变换并调制,采用伪 Wigner-Ville 分布对调制信号进行时频分析,给出了一种自适应的伪 Wigner-Ville 分布最优窗长获取准则,通过局部峰值搜索实现编码信号的瞬时频率估计进而还原出有用信号,实现了光纤陀螺噪声的去除。详细对比了小波方法与自适应时频峰值滤波算法并分析了两者的去噪效果。仿真结果和实际数据验证表明:自适应时频峰值滤波算法能有效减小光纤陀螺输出噪声,信噪比比小波滤波改善1~3 dB;特别对于高动态信号,该算法滤波后的信号能够有效地跟踪原始信号。

  18. A Case Study of the Mechanisms Modulating the Evolution of Valley Fog

    Science.gov (United States)

    Hang, C.; Nadeau, D. F.; Gultepe, I.; Hoch, S. W.; Román-Cascón, C.; Pryor, K.; Fernando, H. J. S.; Creegan, E. D.; Leo, L. S.; Silver, Z.; Pardyjak, E. R.

    2016-09-01

    We present a valley fog case study in which radiation fog is modulated by topographic effects using data obtained from a field campaign conducted in Heber Valley, Utah from January 7-February 1, 2015, as part of the Mountain Terrain Atmospheric Modeling and Observations (MATERHORN) program. We use data collected on January 9, 2015 to gain insight into relationships between typical shallow radiation fog, turbulence, and gravity waves associated with the surrounding topography. A ≈ 10-30 m fog layer formed by radiative cooling was observed from 0720 to 0900 MST under cold air temperatures (≈-9 °C), near-saturated (relative humidity with respect to water ≈95 %), and calm wind (mostly conditions. Drainage flows were observed occasionally prior to fog formation, which modulated heat exchanges between air masses through the action of internal gravity waves and cold-air pool sloshing. The fog appeared to be triggered by cold-air advection from the south (≈200°) at 0700 MST. Quasi-periodic oscillations were observed before and during the fog event with a time period of about 15 min. These oscillations were detected in surface pressure, temperature, sensible heat flux, incoming longwave radiation, and turbulent kinetic energy measurements. We hypothesize that the quasi-periodic oscillations were caused by atmospheric gravity waves with a time period of about 10-20 min based on wavelet analysis. During the fog event, internal gravity waves led to about 1 °C fluctuations in air temperatures. After 0835 MST when net radiation became positive, fog started to dissipate due to the surface heating and heat absorption by the fog particles. Overall, this case study provides a concrete example of how fog evolution is modulated by very weak thermal circulations in mountainous terrain and illustrates the need for high density vertical and horizontal measurements to ensure that the highly spatially varying physics in complex terrain are sufficient for hypothesis testing.

  19. Autonomous sensor-based dual-arm satellite grappling

    Science.gov (United States)

    Wilcox, Brian; Tso, Kam; Litwin, Todd; Hayati, Samad; Bon, Bruce

    1989-01-01

    Dual-arm satellite grappling involves the integration of technologies developed in the Sensing and Perception (S&P) Subsystem for object acquisition and tracking, and the Manipulator Control and Mechanization (MCM) Subsystem for dual-arm control. S&P acquires and tracks the position, orientation, velocity, and angular velocity of a slowly spinning satellite, and sends tracking data to the MCM subsystem. MCM grapples the satellite and brings it to rest, controlling the arms so that no excessive forces or torques are exerted on the satellite or arms. A 350-pound satellite mockup which can spin freely on a gimbal for several minutes, closely simulating the dynamics of a real satellite is demonstrated. The satellite mockup is fitted with a panel under which may be mounted various elements such as line replacement modules and electrical connectors that will be used to demonstrate servicing tasks once the satellite is docked. The subsystems are housed in three MicroVAX II microcomputers. The hardware of the S&P Subsystem includes CCD cameras, video digitizers, frame buffers, IMFEX (a custom pipelined video processor), a time-code generator with millisecond precision, and a MicroVAX II computer. Its software is written in Pascal and is based on a locally written vision software library. The hardware of the MCM Subsystem includes PUMA 560 robot arms, Lord force/torque sensors, two MicroVAX II computers, and unimation pneumatic parallel grippers. Its software is written in C, and is based on a robot language called RCCL. The two subsystems are described and test results on the grappling of the satellite mockup with rotational rates of up to 2 rpm are provided.

  20. The combined Fog Monitoring System of ARPAV over the Veneto Region, Po Valley - Italy

    Science.gov (United States)

    Domenichini, F.; Rossa, A.; Zardini, F.; Monai, M.; Calza, M.; Della Valle, A.; Gaspari, V.

    2010-07-01

    The presence of fog is a frequent problem in the Po Valley. The consequent reduction in visibility has a strong impact on the road, air, ship and railway traffic. Both, fog monitoring and forecasting, constitute significant challenges, not least due to the high spatial and temporal variability of the phenomenon. ARPAV (Regional Agency for Environmental Prevention and Protection of Veneto) is the regional meteorological service of the north-eastern Italian region Veneto and, as such, is responsible for meteorological support to institutional and private users. Real-time visibility information over an extended area would represent an interesting product for road and transport safety. In the framework of the FP7 project Roadidea, (14 partners from 8 different countries, Dec 2007 - Aug 2010) on road safety and traffic control ARPAV developed pilot system for the fog monitoring. The main idea of this fog monitoring methodology is to merge information derived from different observation platforms, i.e. satellite low stratus cloud classification, direct visibility monitoring, statistical estimation of low visibility from meteorological parameters at the ground. This information is translated into probability maps of fog occurrence and information weight on a common grid (4x4 km) covering the flat portion of the region Veneto. These weights are used to combine the three data sources into the final fog probability map. A probabilistic verification applied to the fog monitoring product yields encouraging results, and is systematically more skillfull than the fog probabilities derived from the individual data sources. First real-time products are now available on the ARPAV Fog Pilot website for a group of specific users (motorway head office, road police, national railways and others) and are under testing.

  1. Fog collectors and collection techniques

    Science.gov (United States)

    Höhler, I.; Suau, C.

    2010-07-01

    The earth sciences taught that due to the occurrence of water in three phases: gas, liquid and solid, solar energy keeps the hydrological cycle going, shaping the earth surface while regulating the climate and thus allowing smart technologies to interfere in the natural process by rerouting water and employing its yield for natural and human environments’ subsistence. This is the case of traditional fog collectors implemented by several researchers along the Atacama Desert since late ’50s such as vertical tensile mesh or macro-diamonds structures. Nevertheless, these basic prototypes require to be upgraded, mainly through new shapes, fabrics and frameworks’ types by following the principles of lightness, transformability, portability and polyvalence. The vertical canvas of conventional fog collectors contain too much stressed at each joints and as result it became vulnerable. Our study constitutes a research by design of two fog-trap devices along the Atacama Desert. Different climatic factors influence the efficiency of fog harvesting. In order to increase yield of collected fog water, we need to establish suitable placements that contain high rates of fog’s accumulation. As important as the location is also the building reliability of these collectors that will be installed. Their frames and skins have to be adjustable to the wind direction and resistant against strong winds and rust. Its fabric need to be more hydrophobic, elastic and with light colours to ease dripping/drainage and avoid ultra-violet deterioration. In addition, meshes should be well-tensed and frames well-embraced too. In doing so we have conceived two fog collectors: DropNet© (Höhler) and FogHive© (Suau). These designs explore climatic design parameters combined with the agile structural principles of Tensegrity and Geodesic widely developed by Bucky Fuller and Frei Otto. The research methods mainly consisted of literature review; fieldwork; comparative analysis of existing fog

  2. Moving Target Information Extraction Based on Single Satellite Image

    Directory of Open Access Journals (Sweden)

    ZHAO Shihu

    2015-03-01

    Full Text Available The spatial and time variant effects in high resolution satellite push broom imaging are analyzed. A spatial and time variant imaging model is established. A moving target information extraction method is proposed based on a single satellite remote sensing image. The experiment computes two airplanes' flying speed using ZY-3 multispectral image and proves the validity of spatial and time variant model and moving information extracting method.

  3. A comparative study of satellite and ground-based phenology.

    Science.gov (United States)

    Studer, S; Stöckli, R; Appenzeller, C; Vidale, P L

    2007-05-01

    Long time series of ground-based plant phenology, as well as more than two decades of satellite-derived phenological metrics, are currently available to assess the impacts of climate variability and trends on terrestrial vegetation. Traditional plant phenology provides very accurate information on individual plant species, but with limited spatial coverage. Satellite phenology allows monitoring of terrestrial vegetation on a global scale and provides an integrative view at the landscape level. Linking the strengths of both methodologies has high potential value for climate impact studies. We compared a multispecies index from ground-observed spring phases with two types (maximum slope and threshold approach) of satellite-derived start-of-season (SOS) metrics. We focus on Switzerland from 1982 to 2001 and show that temporal and spatial variability of the multispecies index correspond well with the satellite-derived metrics. All phenological metrics correlate with temperature anomalies as expected. The slope approach proved to deviate strongly from the temporal development of the ground observations as well as from the threshold-defined SOS satellite measure. The slope spring indicator is considered to indicate a different stage in vegetation development and is therefore less suited as a SOS parameter for comparative studies in relation to ground-observed phenology. Satellite-derived metrics are, however, very susceptible to snow cover, and it is suggested that this snow cover should be better accounted for by the use of newer satellite sensors.

  4. Coastal fog, climate change, and the environment

    Science.gov (United States)

    Torregrosa, Alicia; O'Brien, Travis A.; Faloona, Ian C.

    2014-01-01

    Coastal marine fog, a characteristic feature of climates generated at the eastern boundaries of ocean basins worldwide, evokes different feelings in those who experience it (see Figure 1). Authors and poets use fog to represent mystery, bleakness, and confusion. Film directors seek out fog to shroud scenes in eerie gloominess. Tourists visiting beaches bemoan the cool and damp conditions that create a striking contrast to the sunny warm conditions typically found less than a few kilometers inland. Airline passengers delayed by fog impatiently wait for the skies to clear. Residents get used to the Sun “rising” in midday after fog dissipates.

  5. A Hybrid Scheme for Fine-Grained Search and Access Authorization in Fog Computing Environment

    Science.gov (United States)

    Xiao, Min; Zhou, Jing; Liu, Xuejiao; Jiang, Mingda

    2017-01-01

    In the fog computing environment, the encrypted sensitive data may be transferred to multiple fog nodes on the edge of a network for low latency; thus, fog nodes need to implement a search over encrypted data as a cloud server. Since the fog nodes tend to provide service for IoT applications often running on resource-constrained end devices, it is necessary to design lightweight solutions. At present, there is little research on this issue. In this paper, we propose a fine-grained owner-forced data search and access authorization scheme spanning user-fog-cloud for resource constrained end users. Compared to existing schemes only supporting either index encryption with search ability or data encryption with fine-grained access control ability, the proposed hybrid scheme supports both abilities simultaneously, and index ciphertext and data ciphertext are constructed based on a single ciphertext-policy attribute based encryption (CP-ABE) primitive and share the same key pair, thus the data access efficiency is significantly improved and the cost of key management is greatly reduced. Moreover, in the proposed scheme, the resource constrained end devices are allowed to rapidly assemble ciphertexts online and securely outsource most of decryption task to fog nodes, and mediated encryption mechanism is also adopted to achieve instantaneous user revocation instead of re-encrypting ciphertexts with many copies in many fog nodes. The security and the performance analysis show that our scheme is suitable for a fog computing environment. PMID:28629131

  6. DIGITAL VIDEO BROADCAST RETURN CHANNEL VIA SATELLITE (DVB-RCS HUB FOR SATELLITE BASED E-LEARNING

    Directory of Open Access Journals (Sweden)

    N.G.Vasantha Kumar

    2011-02-01

    Full Text Available This paper discusses in-house designed and developed scale-down DVB-RCS hub along with the performance of the realized hub. This development is intended to support the Satellite Based e-Learning initiative in India. The scale-down DVB-RCS HUB is implemented around a single PC with other subsystems making it very cost effective and unique of its kind. This realization will drastically reduce the total cost of Satellite based Education Networks as very low cost commercially available Satellite Interactive Terminals (SITs complying to open standard could be used at remote locations. The system is successfully tested to work with a commercial SIT using a GEO satellite EDUSAT which is especially dedicated for satellite based e-Learning. The internal detail of the DVB-RCS Forward and Return Link Organization and how it manages the Satellite Interactive Terminals access to the satellite channel using MF-TDMA approach has been described.

  7. Technology status of HNF-based monopropellants for satellite propulsion

    NARCIS (Netherlands)

    Marée, A.G.M.; Moerel, J.L.P.A.; Weiland-Veltmans, W.H.M.; Wierkx, F.J.M.; Zevenbergen, J.

    2004-01-01

    This paper reports on significant technological progress made over the last few years in determining the feasibility of HNF-based monopropellants. An HNF-based monopropellant is an interesting alternative for hydrazine as monopropellant for satellite propulsion. New non-toxic monopropellants based o

  8. Technology status of HNF-based monopropellants for satellite propulsion

    NARCIS (Netherlands)

    Marée, A.G.M.; Moerel, J.L.P.A.; Weiland-Veltmans, W.H.M.; Wierkx, F.J.M.; Zevenbergen, J.

    2004-01-01

    This paper reports on significant technological progress made over the last few years in determining the feasibility of HNF-based monopropellants. An HNF-based monopropellant is an interesting alternative for hydrazine as monopropellant for satellite propulsion. New non-toxic monopropellants based o

  9. In situ detection of the chemistry of individual fog droplet residues in the Pearl River Delta region, China

    Science.gov (United States)

    Bi, Xinhui; Lin, Qinhao; Peng, Long; Zhang, Guohua; Wang, Xinming; Brechtel, Fred J.; Chen, Duohong; Li, Mei; Peng, Ping'an; Sheng, Guoying; Zhou, Zhen

    2016-08-01

    We use a single-particle aerosol mass spectrometer coupled with a ground-based counterflow virtual impactor to measure the chemical compositions of individual submicron fog droplet residues. This is the first report on single particle mass spectrometry measurements of fog droplet residual particles at ground level in an urban area. We show that most of the fog droplet residues were composed of elemental carbon (EC) (67.7%), followed by K-rich (19.2%) and mineral dust/metal (12.3%) particles. The predominance of EC-containing particles demonstrated that these particles could be effective fog nuclei and highlights the important influence of anthropogenic emissions on regional climate system. Compared with interstitial and ambient aerosols, nitrate was enhanced, sulfate was depressed, and ammonium- and organics-containing particles were hardly found in the fog droplet residues during fog events, suggesting that dust and metal particles containing nitrate may be preferentially activated and that ammonium and organics may not play important roles in fog formation in Guangzhou. We also present direct observational evidence that trimethylamine and hydroxymethanesulfonate are not found within fog droplet residues, although we previously observed enhanced gas-to-particle partitioning of these compounds by fog processing. Additionally, higher fraction or intensities of [K]+, [Fe]+, and [SiO3]- were found in fog droplet residues than in ambient and interstitial particles.

  10. First Steps for a Giant FOG: Searching for the Limits

    Science.gov (United States)

    Guattari, Frederic; Lucas, Alexandra; Foughali, Ghaieth; Bigueur, Alexandre; de Toldi, Elliot; Schreiber, Ulrich; Wassermann, Joachim

    2017-04-01

    Based on recent experiences in constructing very low noise fibre-optic gyroscopes (FOG) dedicated to seismology, we will present first performance results of a large fibre-optic coil (approx. 1m diameter). Next to in house (iXBlue) factory testing the self-noise of the new sensor is estimated by co-locating it to existing high performance large ring lasers located in Wettzell and Fürstenfeldbruck (Germany), respectively. The reason for constructing this huge FOG is to evaluate experimentally the physical limits (if any exists) of this kind of technology. While this experiment is probing the fundamental limits of FOGs technology and thus is interesting from the construction point of view, it also serves as a first step for cost effective very low noise laboratory rotational seismometer and leads in a second step to performance improvements on portable rotational seismometer

  11. Monte Carlo simulation of laser attenuation characteristics in fog

    Science.gov (United States)

    Wang, Hong-Xia; Sun, Chao; Zhu, You-zhang; Sun, Hong-hui; Li, Pan-shi

    2011-06-01

    Based on the Mie scattering theory and the gamma size distribution model, the scattering extinction parameter of spherical fog-drop is calculated. For the transmission attenuation of the laser in the fog, a Monte Carlo simulation model is established, and the impact of attenuation ratio on visibility and field angle is computed and analysed using the program developed by MATLAB language. The results of the Monte Carlo method in this paper are compared with the results of single scattering method. The results show that the influence of multiple scattering need to be considered when the visibility is low, and single scattering calculations have larger errors. The phenomenon of multiple scattering can be interpreted more better when the Monte Carlo is used to calculate the attenuation ratio of the laser transmitting in the fog.

  12. Temporal Variability and Characterization of Aerosols across the Pakistan Region during the Winter Fog Periods

    Directory of Open Access Journals (Sweden)

    Muhammad Fahim Khokhar

    2016-05-01

    Full Text Available Fog is a meteorological/environmental phenomenon which happens across the Indo-Gangetic Plains (IGP and leads to significant social and economic problems, especially posing significant threats to public health and causing disruptions in air and road traffic. Meteorological stations in Pakistan provide limited information regarding fog episodes as these provide only point observations. Continuous monitoring, as well as a spatially coherent picture of fog distribution, is possible through the use of satellite observations. This study focuses on the 2012–2015 winter fog episodes over the Pakistan region using the Moderate Resolution Image Spectrometer (MODIS, the Ozone Monitoring Instrument and the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO products. The main objective of the study was to map the spatial distribution of aerosols, their types, and to identify the aerosol origins during special weather conditions like fog in Pakistan. The study also included ground monitoring of particulate matter (PM concentrations, which were conducted during the 2014–2015 winter period only. Overall, this study is part of a multi-country project supported by the International Centre for Integrated Mountain Development (ICIMOD, started in 2014–2015 winter period, whereby scientists from Bangladesh, India and Nepal have also conducted measurements at their respective sites. A significant correlation between MODIS (AOD and AERONET Station (AOD data from Lahore was identified. Mass concentration of PM10 at all sampling sites within Lahore city exceeded the National Environmental Quality Standards (NEQS levels on most of the occasions. Smoke and absorbing aerosol were found to be major constituents of winter fog in Pakistan. Furthermore, an extended span of winter fog was also observed in Lahore city during the winter of 2014–2015. The Vertical Feature Mask (VFM provided by CALIPSO satellite confirmed the low-lying aerosol

  13. Characteristics of the Boundary Layer Structure of Sea Fog on the Coast of Southern China

    Institute of Scientific and Technical Information of China (English)

    HUANG Huijun; LIU Hongnian; JIANG Weimei; HUANG Jian; MAO Weikang

    2011-01-01

    Using boundary layer data with regard to sea fog observed at the Science Experiment Base for Marine Meteorology at Bohe,Guangdong Province,the structure of the atmospheric boundary layer and the characteristics of the tops of the fog and the clouds were analyzed.In addition,the effects of advection,radiation,and turbulence during sea fog were also investigated.According to the stability definition of saturated,wet air,the gradient of the potential pseudo-equivalent temperature equal to zero was defined as the thermal turbulence interface.There is evidence to suggest that two layers of turbulence exist in sea fog.Thermal turbulence produced by long-wave radiation is prevalent above the thermal turbulence interface,whereas mechanical turbulence aroused by wind shear is predominant below the interface.The height of the thermal turbulence interface was observed between 180 m and 380 m.Three important factors are closely related to the development of the top of the sea fog:(1) the horizontal advection of the water vapor,(2) the long-wave radiation of the fog top,and (3) the movement of the vertical turbulence.Formation,development,and dissipation are the three possible phases of the evolution of the boundary-layer structure during the sea fog season.In addition,the thermal turbulence interface is the most significant turbulence interface during the formation and development periods; it is maintained after sea fog rises into the stratus layer.

  14. Traffic accident and emission reduction through intermittent release measures for heavy fog weather

    Science.gov (United States)

    Shi, Jing; Tan, Jin-Hua

    2015-09-01

    Heavy fog weather can increase traffic accidents and lead to freeway closures which result in delays. This paper aims at exploring traffic accident and emission characteristics in heavy fog, as well as freeway intermittent release measures for heavy fog weather. A driving simulator experiment is conducted for obtaining driving behaviors in heavy fog. By proposing a multi-cell cellular automaton (CA) model based on the experimental data, the role of intermittent release measures on the reduction of traffic accidents and CO emissions is studied. The results show that, affected by heavy fog, when cellular occupancy ρ traffic accidents is much higher; and CO emissions increase significantly when ρ traffic accidents and level of CO emissions become reasonable. Obviously, the measure can enhance traffic safety and reduce emissions.

  15. Indoor test of the fog's effect on FSO link

    Science.gov (United States)

    Touati, Abir; Abdaoui, Abderrazak; Touati, Farid; Khandakar, Amith; Bouallegue, Ammar

    2017-02-01

    In order to distinguish the most rigorous model, we made a comparison between measurements data and the mostly used empirical models. These models use the visibility as a basic parameter to predict the fog attenuation. In order to measure the visibility, we used a laser lamp of 532 nm and two light sensors. The experimental set up is composed of a fog machine and two KORUZA terminals operating at 1310 nm and 1550 nm, respectively. Every one minute, the measured attenuation is averaged to one value then compared to the attenuation calculated based on measured visibility and according to the empirical models cited previously.

  16. OPEN-LOOP FOG SIGNAL TESTING AND WAVELET ELIMINATING NOISE

    Institute of Scientific and Technical Information of China (English)

    ZHUYun-zhao; WANGShun-ring; MIAOLing-juan; WANGBo

    2005-01-01

    An open-loop fiber optic gyro (FOG) testing system is designed. The noise characteristic of open-loop fiber optic gyro signals is analyzed. The wavelet eliminating noise method is discussed and compared with other methods, such as smoothing and low-pass filter methods. Results indicate that the wavelet eliminating noise method can satisfy the measuring demand of the FOG weak output signal with noise disturbing. The wavelet analysis method can efficiently eliminate the noise and reserve the information of the signal. The eliminating noise effect of using different wavelet base functions is compared. The effectiveness of multiresolution wavelet analyses of eliminating noise is proved by experimental results.

  17. Acid fog deposition and the declining forest in Tanzawa mountains, Japan.

    Science.gov (United States)

    Igawa, M.; Shigihara, A.; Goto, S.; Nanzai, B.

    2010-07-01

    Since 1988, we have investigated fog chemistry in Mt. Oyama, Tanzawa mountains, Japan, and acid fog has been frequently observed there. We have observed fog on Mt. Oyama by using a night view video camera placed at the base of the mountain, by using a visibility meter at the top of the mountain, and by an active fog sampler at the mountainside. We have reported the fog frequency at the top of Mt. Oyama to be 46% measured by the video camera, but it was overestimated. The visibility measured at the top of the mountain is the most reliable index, and the top of the mountain is covered with fog for about 30%. The frequency of about 15% was added for the case of the visibility of a few km when it was measured by a night view video camera placed at the base of the mountain (8.5 km far from the top). Fog-water deposition increases with the increasing altitude to be much larger than the rain-water deposition. The factors affecting on the occult precipitation intensity were investigated by the simultaneous measurement of the rainfall intensity under a canopy, the wind speed and direction, and the visibility at the top of the mountain. Air pollution has been improved recently in Japan, but acid fog is not improved and has been affecting the leaves of the trees. In Tanzawa mountains, many fir trees and beech trees are declining, while cedar trees show no decline symptoms. We have investigated the effect of acid fog on the trees of these species by exposing simulated acid fog on the seedlings of the species. Seedlings of fir and beech are much damaged by the long term exposure of pH 3 fog, while cedar seedlings are not affected by the acid fog. By the exposure of simulated acid fog, the epicuticle wax is eroded at first, then the cross linking polycation between sugar chains of cell wall is ion-exchanged with proton and the cell wall is swollen, and the membrane calcium is desorbed from the membrane, which lowers the tolerance of the trees to the climate change. Fir and beech

  18. A satellite based telemetry link for a UAV application

    Science.gov (United States)

    Bloise, Anthony

    1995-01-01

    The requirements for a satellite based communication facility to service the needs of the Geographical Information System (GIS) data collection community are addressed in this paper. GIS data is supplied in the form of video imagery at sub-television rates in one or more spectral bands / polarizations laced with a position correlated data stream. The limitations and vicissitudes of using a terrestrial based telecommunications link to collect GIS data are illustrated from actual mission scenarios. The expectations from a satellite based communications link by the geophysical data collection community concerning satellite architecture, operating bands, bandwidth, footprint agility, up link and down link hardware configurations on the UAV, the Mobile Control Vehicle and at the Central Command and Data Collection Facility comprise the principle issues discussed in the first section of this paper. The final section of the paper discusses satellite based communication links would have an increased volume and scope of services the GIS data collection community could make available to the GIS user community, and the price the data collection community could afford to pay for access to the communication satellite described in the paper.

  19. Multi-spectral band selection for satellite-based systems

    Energy Technology Data Exchange (ETDEWEB)

    Clodius, W.B.; Weber, P.G.; Borel, C.C.; Smith, B.W.

    1998-09-01

    The design of satellite based multispectral imaging systems requires the consideration of a number of tradeoffs between cost and performance. The authors have recently been involved in the design and evaluation of a satellite based multispectral sensor operating from the visible through the long wavelength IR. The criteria that led to some of the proposed designs and the modeling used to evaluate and fine tune the designs will both be discussed. These criteria emphasized the use of bands for surface temperature retrieval and the correction of atmospheric effects. The impact of cost estimate changes on the final design will also be discussed.

  20. Microphysical Characteristics of Sea Fog over the East Coast of Leizhou Peninsula, China

    Institute of Scientific and Technical Information of China (English)

    ZHAO Lijuan; NIU Shengjie; ZHANG Yu; XU Feng

    2013-01-01

    Microphysical properties of sea fog and correlations of these properties were analyzed based on the measurements from a comprehensive field campaign carried out from 15 March to 18 April 2010 on Donghai Island (21°35″N,110°32′5″E) in Zhanjiang,Guangdong Province,China.There were four types of circulation pattern in favor of sea fog events in this area identified,and the synoptic weather pattern was found to influence the microphysical properties of the sea fogs.Those influenced by a warm sector in front of a cold front or the anterior part of low pressure were found to usually have a much longer duration,lower visibility,greater liquid water content,and bigger fog droplet sizes.A fog droplet number concentration of N> 1 cm-3 and liquid water content of L≥0.001 g m-3 can be used to define sea fogs in this area.The type of fog droplet size distribution of the sea fog events was mostly monotonically-decreasing,with the spectrum width always being >20 μ.m.The significant temporal variation of N was due in large part to the number concentration variation of fog droplets with radius <3 μm.A strong collection process appeared when droplet spectrum width was >10 μm,which subsequently led to the sudden increase of droplet spectrum width.The dominant physical process during the sea fog events was activation with subsequent condensational growth or reversible evaporation processes,but turbulent mixing also played an important role.The collection process occurred,but was not vital.

  1. Tracking target objects orbiting earth using satellite-based telescopes

    Energy Technology Data Exchange (ETDEWEB)

    De Vries, Willem H; Olivier, Scot S; Pertica, Alexander J

    2014-10-14

    A system for tracking objects that are in earth orbit via a constellation or network of satellites having imaging devices is provided. An object tracking system includes a ground controller and, for each satellite in the constellation, an onboard controller. The ground controller receives ephemeris information for a target object and directs that ephemeris information be transmitted to the satellites. Each onboard controller receives ephemeris information for a target object, collects images of the target object based on the expected location of the target object at an expected time, identifies actual locations of the target object from the collected images, and identifies a next expected location at a next expected time based on the identified actual locations of the target object. The onboard controller processes the collected image to identify the actual location of the target object and transmits the actual location information to the ground controller.

  2. 基于脚本驱动的光纤陀螺自动化测试系统设计%Design of FOG automatic testing system based on script driving technology

    Institute of Scientific and Technical Information of China (English)

    李贺; 邓学文; 朱奎宝; 邓年茂

    2016-01-01

    介绍一种采用脚本驱动技术设计光纤陀螺自动化测试系统的方法.参考ATLAS语言结构设计脚本语言编写的格式,给出陀螺测试软件整体的运行框架,利用项目管理的方式解决光纤陀螺测试过程不规范和数据存储混乱等问题,设计专用硬件电路实现多类型光纤陀螺的测试任务.实验结果表明,该测试系统实用性好,能有效降低光纤陀螺的测试成本和时间成本,提高测试效率和准确性.%A method of designing the FOG automatic testing system based on script driving technology was introduced.Accor-ding to the ATLAS language structure,the format of script language writing was designed.The running frame of testing software was given.The method of proj ect management was used to solve the problems of testing irregularity and data storage confusion. And the design of hardware circuit realized the testing task of various FOG.Experimental results show that the system is practi-cal and it can reduce the testing cost and time cost,and improve the testing efficiency and the accuracy of the FOG.

  3. SOFT project: a new forecasting system based on satellite data

    Science.gov (United States)

    Pascual, Ananda; Orfila, A.; Alvarez, Alberto; Hernandez, E.; Gomis, D.; Barth, Alexander; Tintore, Joaquim

    2002-01-01

    The aim of the SOFT project is to develop a new ocean forecasting system by using a combination of satellite dat, evolutionary programming and numerical ocean models. To achieve this objective two steps are proved: (1) to obtain an accurate ocean forecasting system using genetic algorithms based on satellite data; and (2) to integrate the above new system into existing deterministic numerical models. Evolutionary programming will be employed to build 'intelligent' systems that, learning form the past ocean variability and considering the present ocean state, will be able to infer near future ocean conditions. Validation of the forecast skill will be carried out by comparing the forecasts fields with satellite and in situ observations. Validation with satellite observations will provide the expected errors in the forecasting system. Validation with in situ data will indicate the capabilities of the satellite based forecast information to improve the performance of the numerical ocean models. This later validation will be accomplished considering in situ measurements in a specific oceanographic area at two different periods of time. The first set of observations will be employed to feed the hybrid systems while the second set will be used to validate the hybrid and traditional numerical model results.

  4. Validation of an Innovative Satellite-Based UV Dosimeter

    Science.gov (United States)

    Morelli, Marco; Masini, Andrea; Simeone, Emilio; Khazova, Marina

    2016-08-01

    We present an innovative satellite-based UV (ultraviolet) radiation dosimeter with a mobile app interface that has been validated by exploiting both ground-based measurements and an in-vivo assessment of the erythemal effects on some volunteers having a controlled exposure to solar radiation.Both validations showed that the satellite-based UV dosimeter has a good accuracy and reliability needed for health-related applications.The app with this satellite-based UV dosimeter also includes other related functionalities such as the provision of safe sun exposure time updated in real-time and end exposure visual/sound alert. This app will be launched on the global market by siHealth Ltd in May 2016 under the name of "HappySun" and available both for Android and for iOS devices (more info on http://www.happysun.co.uk).Extensive R&D activities are on-going for further improvement of the satellite-based UV dosimeter's accuracy.

  5. Impact of Fog on Electromagnetic Wave Propagation

    Science.gov (United States)

    Morris, Jonathon; Fleisch, Daniel

    2002-04-01

    This experiment was designed to explore the impact of fog on electromagnetic radiation, in particular microwaves and infrared light. For years law enforcement agencies have used microwave radiation (radar guns) to measure the speed of vehicles, and the last ten years has seen increased use of LIDAR, which uses 905-nm infrared radiation rather than microwaves. To evaulate the effect of fog on the operation of these devices, we have constructed a fog chamber with microwave and optical portals to allow light from a HeNe laser and 10.6-GHz microwaves to propagate through various densities of fog. Data is acquired using Vernier Logger Pro and analyzed using MATLAB and Mathematica. Using the attenuation of the laser light to determine fog density, the impact of fog on the signal-to-noise ratio of both microwave and IR devices may be quantified, and the maximum useful range may be calculated.

  6. Engineering satellite-based navigation and timing global navigation satellite systems, signals, and receivers

    CERN Document Server

    Betz, J

    2016-01-01

    This book describes the design and performance analysis of satnav systems, signals, and receivers. It also provides succinct descriptions and comparisons of all the world’s satnav systems. Its comprehensive and logical structure addresses all satnav signals and systems in operation and being developed. Engineering Satellite-Based Navigation and Timing: Global Navigation Satellite Systems, Signals, and Receivers provides the technical foundation for designing and analyzing satnav signals, systems, and receivers. Its contents and structure address all satnav systems and signals: legacy, modernized, and new. It combines qualitative information with detailed techniques and analyses, providing a comprehensive set of insights and engineering tools for this complex multidisciplinary field. Part I describes system and signal engineering including orbital mechanics and constellation design, signal design principles and underlying considerations, link budgets, qua tifying receiver performance in interference, and e...

  7. Alto Patache fog oasis in the Atacama Desert: Geographical basis for a sustainable development program

    Science.gov (United States)

    Calderón, M.; Cereceda, P.; Larrain, H.; Osses, P.; Pérez, L.; Ibáñez, M.

    2010-07-01

    Alto Patache coastal fog oasis is a protected area located south of Iquique, Northern Chile, being presently in charge of the Atacama Desert Center (ADC) research group of the Pontificia Universidad Católica de Chile, since 1997. On 2007, the Chilean Government bestowed a piece of land stretch covering 1,114 hectares to ADC scientific group for scientific research, ecosystem protection and environmental education. This oasis has been recently studied from different points of view: climate, biogeography, fog collection, geomorphology, soil survey and land use planning, plant distribution, conservation and archaeology. During 2009, a study of the geographical basis to elaborate a general management plan was undertaken to collect information to fulfill our planned out objectives. Through this study, georreferenciated strategic information was compiled to evaluate future actions conducting to a sustainable development within the protected area. This information was translated into thematic maps showing the spatial distribution of variables like: climate, geology, geomorphology, soils, vegetation, fauna, archaeological sites and management zones. The methodology used is the analysis of satellite imagery, using GPS by creating a cartographic Data Base incorporated in GIS. Results show that the area starts at the littoral plain, ranging from 500 m to 2.000 m, being continued in parts by a piedmont intercepted by a very abrupt mega-cliff, or hectares of climbing sand dunes leading to a short high plateau limited by a soft hilly area to the East. Two soil types are characteristic: Entisols (Torriorthent) covering the coastal beach sediments, and Aridisols along the cliff and adjacent hills. Vegetation consists not only of a very rich lichen cover, but also of endangered vascular species associations constituting a very fragile sub-tropical coastal desert community, such as Eulychnia, Cumulopuntia, Eriosyce cacti, and Lycium - Nolana- Ephedra communities. Fog oasis

  8. Exposure Standard for Fog Oil

    Science.gov (United States)

    1990-11-15

    18 frmmation, dermatitis, folliculitis, acne, eczema and contact sensitivity. ,’• (The term ’conventionally-refined’ is used here to describe...comparable to "new" fog oil. Of the species tested (rat, rabbit, dog , hamster and mouse), rats and dog & were most affected by the mineral oil mists (Table 3...Exposures to 100 mg/mr for one year caused pulmonary lipoid granulomas in the dog and pneumonitis in the rat. Findings of "a few fibrotic strands

  9. Satellite Type Estination from Ground-based Photometric Observation

    Science.gov (United States)

    Endo, T.; Ono, H.; Suzuki, J.; Ando, T.; Takanezawa, T.

    2016-09-01

    The optical photometric observation is potentially a powerful tool for understanding of the Geostationary Earth Orbit (GEO) objects. At first, we measured in laboratory the surface reflectance of common satellite materials, for example, Multi-layer Insulation (MLI), mono-crystalline silicon cells, and Carbon Fiber Reinforced Plastic (CFRP). Next, we calculated visual magnitude of a satellite by simplified shape and albedo. In this calculation model, solar panels have dimensions of 2 by 8 meters, and the bus area is 2 meters squared with measured optical properties described above. Under these conditions, it clarified the brightness can change the range between 3 and 4 magnitudes in one night, but color index changes only from 1 to 2 magnitudes. Finally, we observed the color photometric data of several GEO satellites visible from Japan multiple times in August and September 2014. We obtained that light curves of GEO satellites recorded in the B and V bands (using Johnson filters) by a ground-base optical telescope. As a result, color index changed approximately from 0.5 to 1 magnitude in one night, and the order of magnitude was not changed in all cases. In this paper, we briefly discuss about satellite type estimation using the relation between brightness and color index obtained from the photometric observation.

  10. Trellis-coded CPM for satellite-based mobile communications

    Science.gov (United States)

    Abrishamkar, Farrokh; Biglieri, Ezio

    1988-01-01

    Digital transmission for satellite-based land mobile communications is discussed. To satisfy the power and bandwidth limitations imposed on such systems, a combination of trellis coding and continuous-phase modulated signals are considered. Some schemes based on this idea are presented, and their performance is analyzed by computer simulation. The results obtained show that a scheme based on directional detection and Viterbi decoding appears promising for practical applications.

  11. PERSPECTIVES FOR FOG COMPUTING IN MANUFACTURING

    Directory of Open Access Journals (Sweden)

    Jakub PIZOŃ

    2016-09-01

    Full Text Available This article discusses ongoing efforts to enable the fog computing vision in manufacturing. As a new paradigm of computing implementation of fog computing faces many challenges that open perspective of new applications within a field of manufacturing. It is expected that fog computing will be one of factors that will accelerate development of in forth industrial revolution. In this article we discuss the perspectives of manufacturing companies surrounded by new solutions of CPS, CPPS and CM in relation to fog computing.

  12. Development testing of large volume water sprays for warm fog dispersal

    Science.gov (United States)

    Keller, V. W.; Anderson, B. J.; Burns, R. A.; Lala, G. G.; Meyer, M. B.; Beard, K. V.

    1986-01-01

    A new brute-force method of warm fog dispersal is described. The method uses large volume recycled water sprays to create curtains of falling drops through which the fog is processed by the ambient wind and spray induced air flow. Fog droplets are removed by coalescence/rainout. The efficiency of the technique depends upon the drop size spectra in the spray, the height to which the spray can be projected, the efficiency with which fog laden air is processed through the curtain of spray, and the rate at which new fog may be formed due to temperature differences between the air and spray water. Results of a field test program, implemented to develop the data base necessary to assess the proposed method, are presented. Analytical calculations based upon the field test results indicate that this proposed method of warm fog dispersal is feasible. Even more convincingly, the technique was successfully demonstrated in the one natural fog event which occurred during the test program. Energy requirements for this technique are an order of magnitude less than those to operate a thermokinetic system. An important side benefit is the considerable emergency fire extinguishing capability it provides along the runway.

  13. The principle of the positioning system based on communication satellites

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    It is a long dream to realize the communication and navigation functionality in a satellite system in the world. This paper introduces how to establish the system, a positioning system based on communication satellites called Chinese Area Positioning System (CAPS). Instead of the typical navigation satellites, the communication satellites are configured firstly to transfer navigation signals from ground stations, and can be used to obtain service of the positioning, velocity and time, and to achieve the function of navigation and positioning. Some key technique issues should be first solved; they include the accuracy position determination and orbit prediction of the communication satellites, the measur- ing and calculation of transfer time of the signals, the carrier frequency drift in communication satellite signal transfer, how to improve the geometrical configuration of the constellation in the system, and the integration of navigation & communication. Several innovative methods are developed to make the new system have full functions of navigation and communication. Based on the development of crucial techniques and methods, the CAPS demonstration system has been designed and developed. Four communication satellites in the geosynchronous orbit (GEO) located at 87.5°E, 110.5°E, 134°E, 142°E and barometric altimetry are used in the CAPS system. The GEO satellites located at 134°E and 142°E are decommissioned GEO (DGEO) satellites. C-band is used as the navigation band. Dual frequency at C1=4143.15 MHz and C2=3826.02 MHz as well as dual codes with standard code (CA code and precision code (P code)) are adopted. The ground segment consists of five ground stations; the master station is in Lintong, Xi’an. The ground stations take a lot of responsibilities, including monitor and management of the operation of all system components, determination of the satellite position and prediction of the satellite orbit, accomplishment of the virtual atomic clock

  14. 基于多项式模型和 BP神经网络的光纤陀螺温度补偿%TEMPERATURE COMPENSATION FOR FOG BASED ON POLYNOMIAL MODEL AND BP NEURAL NETWORK

    Institute of Scientific and Technical Information of China (English)

    席绪奇; 姚志成; 何志昆; 赵曦晶

    2013-01-01

    在对开环干涉型光纤陀螺仪大量实验数据分析的基础上,分别对光纤陀螺仪零位温度漂移建立BP神经网络温度补偿,标度因数与温度、输入角速率建立多项式模型。利用建立的模型对实验数据进行温度补偿。补偿结果表明,BP神经网络补偿效果优于多项式模型,零偏和零偏稳定性减小了一个数量级,补偿效果明显。%Based on analysing lots of experimental data of open-loop interference type fibre optic gyro (FOG), we set up the BP neural network temperature compensation for zero temperature drift of FOG and the polynomial model for scale factor , temperature and input angular rate respectively .The established model is used to make temperature compensation on experimental data .The results of compensation show that, BP neural network is better than polynomial model in compensation effect , the zero-bias and the stability of zero-bias is reduced by an order of magnitude , the compensation effect is noticeable .

  15. 基于暗原色先验的雾天图像车牌定位%License Plate Location Based on Dark Channel Prior in Fog-degraded Images

    Institute of Scientific and Technical Information of China (English)

    鞠丽丽; 王英

    2016-01-01

    在雾天条件下,会影响到基于传统车牌识别方法的车牌识别系统的车牌识别准确率。首先根据He提出的暗原色先验原理应用IMF算法对图像去雾处理;然后进行小波边缘检测,定位车牌候选区域;最后根据车牌先验知识定位车牌区域。实验表明,该方法对雾天条件下车牌定位有良好的效果。%Fog weather conditions affect the license plate recognition system accuracy,which based on traditional license plate recognition method.Firstly,this paper employs Dark Channel Prior principle proposed by He to eliminate the influence of fog weather.Secondly uses b-spline wavelet edge detection to position license plate candidate area of restored images,final-ly locates the license plate according to the the candidate area.

  16. Possible satellite-based observations of the 1997 Leonid meteoroids

    Energy Technology Data Exchange (ETDEWEB)

    Pongratz, M.B.; Carlos, R.C.; Cayton, T.

    1998-12-01

    The Block IIA GPS satellites are equipped with a sensor designed to detect electromagnetic transients. Several phenomena will produce triggers in this sensor. They include earth-based electromagnetic transients such as lightning and two space-based phenomena--deep dielectric discharge and meteoroid or hyper-velocity micro-gram particle impact (HMPI). Energetic electrons in the GPS environment cause the deep dielectric charging. HMPIs cause triggers through the transient electric fields generated by the ejecta plasma. During the 1997 Leonid passage the energetic particle fluxes were very low. In the presence of such low fluxes the typical median trigger rate is 20 per minute with a standard deviation of about 20 per minute. Between 0800 UT and 1200 UT on November 17, 1997, the sensor on a specially configured satellite observed trigger rates more than 10 sigma above the nominal median rate. Sensors on other Block IIA GPS satellites also observed excess triggers during November. Detection is enhanced when the sensor antenna is oriented into the Leonid radiant. While many questions persist the authors feel that it is likely that the excess events during the November interval were caused by the close approach of the satellites to the Leonid meteoroid path.

  17. An Ontology Based Methodology for Satellite Data Semantic Interoperability

    Directory of Open Access Journals (Sweden)

    ABBURU, S.

    2015-08-01

    Full Text Available Satellites and ocean based observing system consists of various sensors and configurations. These observing systems transmit data in heterogeneous file formats and heterogeneous vocabulary from various data centers. These data centers maintain a centralized data management system that disseminates the observations to various research communities. Currently, different data naming conventions are being used by existing observing systems, thus leading to semantic heterogeneity. In this work, sensor data interoperability and semantics of the data are being addressed through ontologies. The present work provides an effective technical solution to address semantic heterogeneity through semantic technologies. These technologies provide interoperability, capability to build knowledge base, and framework for semantic information retrieval by developing an effective concept vocabulary through domain ontologies. The paper aims at a new methodology to interlink the multidisciplinary and heterogeneous sensor data products. A four phase methodology has been implemented to address satellite data semantic interoperability. The paper concludes with the evaluation of the methodology by linking and interfacing multiple ontologies to arrive at ontology vocabulary for sensor observations. Data from Indian Meteorological satellite INSAT-3D satellite have been used as a typical example to illustrate the concepts. This work on similar lines can also be extended to other sensor observations.

  18. Increase California-Oregon Coastal Summer Sea Level Fog from 1950 to 2007

    Science.gov (United States)

    Dorman, C. E.

    2015-12-01

    An analysis is presented of the marine fog distribution based upon the International Comprehensive Ocean-Atmosphere Data Set (ICOADS) ship observations taken during 1950-2007. Deep fog occurrence is reported in routine weather reports that are encoded in an ICOADS ship observation. Occurrence is estimated by the number of deep fog observations divided by the total present weather observations in a one-degree area centered on latitude and longitude grid point intersections. The mean fog occurrence for the summer (June-July-August) 1950-2007 was computed for each one degree point. There is a long term, deep fog occurrence maximum on the California-Oregon coast with its highest value of 16.6 % at 38° N 123° W. This fog maximum is coincident with coldest June-July-August sea surface temperatures (SST) along the coast. To compute annual averages of the maximum, a block average was based on the 19 over water grid points with the deep fog occurrences generally greater than 0.6 times the highest long term maximum value that extended along the California-Oregon coast from 37° N to 44° N. The June-July-August block averaged, annual value computed for each of the 58 summers for the period 1950-2007 has a distinct positive trend. A line fitted to the data has a deep fog percent occurrence increase of +7.4 % from 1950 through 2007 or a trend of +0.13 % per year. The Mann-Kendall test was applied and the trend is significant at the 0.05 level. The increase in long term coastal fog is coincident with a decrease in the California-Oregon coastal SST. The SST decrease is consistent with interior California land temperatures increasing, increasing the cross shore sea level pressure gradient, and increasing the along coast winds creating a positive feedback that causes more upwelling and lower SST.

  19. Real-time WAMI streaming target tracking in fog

    Science.gov (United States)

    Chen, Yu; Blasch, Erik; Chen, Ning; Deng, Anna; Ling, Haibin; Chen, Genshe

    2016-05-01

    Real-time information fusion based on WAMI (Wide-Area Motion Imagery), FMV (Full Motion Video), and Text data is highly desired for many mission critical emergency or security applications. Cloud Computing has been considered promising to achieve big data integration from multi-modal sources. In many mission critical tasks, however, powerful Cloud technology cannot satisfy the tight latency tolerance as the servers are allocated far from the sensing platform, actually there is no guaranteed connection in the emergency situations. Therefore, data processing, information fusion, and decision making are required to be executed on-site (i.e., near the data collection). Fog Computing, a recently proposed extension and complement for Cloud Computing, enables computing on-site without outsourcing jobs to a remote Cloud. In this work, we have investigated the feasibility of processing streaming WAMI in the Fog for real-time, online, uninterrupted target tracking. Using a single target tracking algorithm, we studied the performance of a Fog Computing prototype. The experimental results are very encouraging that validated the effectiveness of our Fog approach to achieve real-time frame rates.

  20. Mesoscale numerical simulation study of warm fog dissipation by salt particles seeding

    Science.gov (United States)

    He, Hui; Guo, Xueliang; Liu, Xiang'e.; Gao, Qian; Jia, Xingcan

    2016-05-01

    Based on the dynamic framework of WRF and Morrison 2-moment explicit cloud scheme, a salt-seeding scheme was developed and used to simulate the dissipation of a warm fog event during 6-7 November 2009 in the Beijing and Tianjin area. The seeding effect and its physical mechanism were studied. The results indicate that when seeding fog with salt particles sized 80 µm and at a quantity of 6 g m-2 at the fog top, the seeding effect near the ground surface layer is negative in the beginning period, and then a positive seeding effect begins to appear at 18 min, with the best effect appearing at 21 min after seeding operation. The positive effect can last about 35 min. The microphysical mechanism of the warm fog dissipation is because of the evaporation due to the water vapor condensation on the salt particles and coalescence with salt particles. The process of fog water coalescence with salt particles contributed mostly to this warm fog dissipation. Furthermore, two series of sensitivity experiments were performed to study the seeding effect under different seeding amounts and salt particles sizes. The results show that seeding fog with salt particles sized of 80 µm can have the best seeding effect, and the seeding effect is negative when the salt particle size is less than 10 µm. For salt particles sized 80 µm, the best seeding effect, with corresponding visibility of 380 m, can be achieved when the seeding amount is 30 g m-2.

  1. A Study of Aerosols Transportation around City Boundary in the Fog Weather

    Science.gov (United States)

    Ding, J.; Li, J. H.; Liu, Y.; Zhang, B. L.; Wang, Q. T.

    2011-09-01

    The structure of city surface seriously affects transport and diffusion of pollutant aerosol particles in the fog weather. So dynamic model population balance model (PBM) of aerosol particles and multiphase-coupled flow model were established to describe the fluid-particle system of fog. Based on the Eulerian-Lagrangian method and Multi-Monte Carlo method, a study of aerosols transportation around city boundary was conducted. The computed results show a part of aerosols change into droplets during the formation of fog, and the average sizes of aerosols, droplets are about 0.032 7 μm and 28.7 μm with time evolution to 60 min. For the development of fog, with time of 60 min and wind of 2 m/s, the number of aerosol is down to 84.5% of initial value, and the average particle size is down to 22.1 μm accordingly. During the dissipation of fog, the numbers of aerosol and fog droplet are decreased to the 1.65% and 0.016 5% of initial value. As wind speed rising, the turbulent motion strength of particles is increased. Eventually, the droplets have almost disappeared, and a small number of aerosols are still suspended in the atmosphere. The computed results reflect the transport and dynamic characteristics for respirable aerosols around city boundary during three stages of fog.

  2. Satellite Based Extrusion Rates for the 2006 Augustine Eruption

    Science.gov (United States)

    Dehn, J.; Bailey, J. E.; Dean, K. G.; Skoog, R.; Valcic, L.

    2006-12-01

    Extrusion rates were calculated from polar orbiting infrared satellite data for the 2006 eruption of Augustine Volcano, Alaska. The pixel integrated brightness temperatures from the satellite data were converted to estimates of ground temperature by making assumptions and using first hand observations about the geometry of the hot area (lava dome, flows and pyroclastic flow deposits) relative to the cold area in the kilometer scale pixels. Extrusion rate is calculated by assuming that at a given temperature, a lava emits an amount of radiation proportional to its volume. On ten occasions during the activity, helicopter based infrared imagers were used to validate the satellite observations. The pre-January 11 thermal activity was not significantly above background in satellite data. The first strong thermal anomalies were recorded during the first explosive phase on January 11. During successive explosive phases in January, bright thermal signals were observed, often saturating the sensors. Large areas (many km2) were observed to be warm in the satellite data, indicative of pyroclastic flows. Sometime during or after January 29, during a phase of sustained ash emission, the thermal signal became persistent, suggesting the beginning of lava effusion. The extrusion rates derived from satellite data varied from 0 to nearly 7 m3/s, giving an eruption rate of 2.7 m3/s. The extrusion event produced two blocky lava flows which moved down the north flank of the volcano. Extrusion occurred through at least March 15 (day 76) when a sharp drop in extrusion rate and thermal signal is observed. Based on the derived extrusion rates, it is estimated that 18 million m3 of lava was extruded during the course of the eruption. This value agreed well with photogrammetric measurements, but does not agree with volumes derived through subtraction of digital elevation models post- and pre- eruption. It should be noted that the thermal approach only works for hot lavas, and does not

  3. Evaluating the hydrological consistency of satellite based water cycle components

    KAUST Repository

    Lopez Valencia, Oliver M.

    2016-06-15

    Advances in multi-satellite based observations of the earth system have provided the capacity to retrieve information across a wide-range of land surface hydrological components and provided an opportunity to characterize terrestrial processes from a completely new perspective. Given the spatial advantage that space-based observations offer, several regional-to-global scale products have been developed, offering insights into the multi-scale behaviour and variability of hydrological states and fluxes. However, one of the key challenges in the use of satellite-based products is characterizing the degree to which they provide realistic and representative estimates of the underlying retrieval: that is, how accurate are the hydrological components derived from satellite observations? The challenge is intrinsically linked to issues of scale, since the availability of high-quality in-situ data is limited, and even where it does exist, is generally not commensurate to the resolution of the satellite observation. Basin-scale studies have shown considerable variability in achieving water budget closure with any degree of accuracy using satellite estimates of the water cycle. In order to assess the suitability of this type of approach for evaluating hydrological observations, it makes sense to first test it over environments with restricted hydrological inputs, before applying it to more hydrological complex basins. Here we explore the concept of hydrological consistency, i.e. the physical considerations that the water budget impose on the hydrologic fluxes and states to be temporally and spatially linked, to evaluate the reproduction of a set of large-scale evaporation (E) products by using a combination of satellite rainfall (P) and Gravity Recovery and Climate Experiment (GRACE) observations of storage change, focusing on arid and semi-arid environments, where the hydrological flows can be more realistically described. Our results indicate no persistent hydrological

  4. The principle of the positioning system based on communication satellites

    Institute of Scientific and Technical Information of China (English)

    AI GuoXiang; SHI HuLi; WU HaiTao; LI ZhiGang; GUO Ji

    2009-01-01

    It is a long dream to realize the communication and navigation functionality in a satellite system in the world.This paper introduces how to establish the system,a positioning system based on communication satellites called Chinese Area Positioning System (CAPS).Instead of the typical navigation satelIites,the communication satellites are configured firstly to transfer navigation signals from ground stations,and can be used to obtain service of the positioning,velocity and time,and to achieve the function of navigation and positioning.Some key technique issues should be first solved; they include the accuracy position determination and orbit prediction of the communication satellites,the measuring and calculation of transfer time of the signals,the carrier frequency drift in communication satellite ignal transfer,how to improve the geometrical configuration of the constellation in the system,and the integration of navigation & communication.Several innovative methods are developed to make the new system have full functions of navigation and communication.Based on the development of crucial techniques and methods,the CAPS demonstration system has been designed and developed.Four communication satellites in the geosynchronous orbit (GEO) located at 87.5°E,110.5°E,134°E,142°E and barometric altimetry are used in the CAPS system.The GEO satellites located at 134°E and 142°E re decommissioned GEO (DGEO) satellites.C-band is used as the navigation band.Dual frequency at C1=4143.15 MHz and C2=3826.02 MHz as well as dual codes with standard code (CA code and precision code (P code)) are adopted.The ground segment consists of five ground stations; the master station is in Lintong,Xi'an.The ground stations take a lot of responsibilities,including monitor and management of the operation of all system components,determination of the satellite position and prediction of the satellite orbit,accomplishment of the virtual atomic clock measurement,transmission and receiving

  5. Aviation Weather and Model-Based Operational Forecasts of Low Visibility and Fog%航空气象要素以及基于数值模式的低能见度和雾的预报

    Institute of Scientific and Technical Information of China (English)

    周斌斌; 蒋乐; 杜钧

    2016-01-01

    This article introduces the operational predictions of hazardous weather elements to aviation both en-route and in TAF. Two visibility algorithms and three fog diagnostic schemes used at NCEP are discussed in particular. The ifrst visibility algorithm is Stoelinga and Warner method. This method requires outputs of four hydrometeors from a model to estimate optical extinction coefifcient and calculate visibility. The second visibility method is an upgrade to the ifrst one by adding more species of hydrometeor. This method can also estimate visibility in high humidity and haze conditions without knowing hydrometers as well as considering the differences between daytime and nighttime. The concept of airport Runway Visibility Range (RVR) is introduced and the relationship between the RVR and horizontal visibility range (HVR) is given. The fog diagnosis includes the UPS method, multi-rule method and physical-process balanced method. The UPS method uses surface-layer stability index. The multi-rule method uses a combination of visibility, cloud, surface humidity and wind speed to diagnose fog occurrence. These two methods do not predict fog intensity. The third method can diagnose both fog occurrence and intensity. It is based on the turbulence condition for fog formation and persistence as well as the explicit formulation of fog liquid water content suggested by a fog’s physical balance theory. Both multi-rule and physical-process balance methods have been implemented operationally in the NCEP’s regional ensemble forecast systems and showed encouraging results. However, the current skill of low visibility and fog forecasts directly derived from a numerical weather prediction model is generally low comparing to the forecasts of other weather elements such as precipitation. The dififculties are discussed and the ways of improvement are also suggested.%简述了对航空运输有危害的天气要素,包括航线要素和航站要素的业务预报。着重介绍了

  6. Periodic material-based vibration isolation for satellites

    Directory of Open Access Journals (Sweden)

    Xinnan Liu

    2016-01-01

    Full Text Available The vibration environment of a satellite is very severe during launch. Isolating the satellitevibrations during launch will significantly enhance reliability and lifespan, and reduce the weight of satellite structure and manufacturing cost. Guided by the recent advances in solid-state physics research, a new type of satellite vibration isolator is proposed by usingperiodic material that is hence called periodic isolator. The periodic isolator possesses a unique dynamic property, i.e., frequency band gaps. External vibrations with frequencies falling in the frequency band gaps of the periodic isolator are to be isolated. Using the elastodynamics and the Bloch-Floquet theorem, the frequency band gaps of periodic isolators are determined. A parametric study is conducted to provide guidelines for the design of periodic isolators. Based on these analytical results, a finite element model of a micro-satellite with a set of designed periodic isolators is built to show the feasibility of vibration isolation. The periodic isolator is found to be a multi-directional isolator that provides vibration isolation in the three directions.

  7. Fog Machines, Vapors, and Phase Diagrams

    Science.gov (United States)

    Vitz, Ed

    2008-01-01

    A series of demonstrations is described that elucidate the operation of commercial fog machines by using common laboratory equipment and supplies. The formation of fogs, or "mixing clouds", is discussed in terms of the phase diagram for water and other chemical principles. The demonstrations can be adapted for presentation suitable for elementary…

  8. 基于大气散射模型的单幅图像快速去雾%Fast single image fog removal based on atmospheric scattering model

    Institute of Scientific and Technical Information of China (English)

    孙伟; 李大健; 刘宏娟; 贾伟

    2013-01-01

    Based on the physical model of atmospheric scattering and an optical reflectance imaging model, three major factors influencing the fog removal for a single image were discussed in detail. The dark channel phenomenon was explained by the optical model, and the method to solve the parameters of atmospheric scattering model was rigorously derived from a new view. The gray-scale opening operation was used to eliminate the interference from a while object to obtain the global atmospheric light and the fast joint bilateral filtering technique was proposed to greatly improve the speed and accuracy of atmospheric scattering function solving. Finally, the scene albedo was recovered by inverting this model. Experiments show that the method can remove effectively the effect of lights from sky and environments and can recover the color and definition of original scenes. The simulation results indicate that the processing time for an image of 576×768 spends only by 1. 7 s. As compared with the existing algorithm, obtained results on a variety of outdoor foggy images demonstrate that the proposed method achieves good restoration for contrast and color deity, and improves image visibility greatly.%根据大气散射物理模型及光学反射成像模型,总结并分析了影响单幅图像去雾效果的3大因素,以实现对雾霾图像的快速去雾.基于光学原理,解释了暗影通道现象,从新的角度推导出了大气散射模型中各参数的求法.利用灰度开运算去除白色目标的干扰获得精确的环境光亮度,基于快速联合双边带滤波精确计算了大气散射函数,最后由光学反射模型计算了场景目标的反射率并有效截断至[0,1]区间.本方法可以消除天空及环境光线的影响,能真实复原场景的色彩和清晰度.仿真结果表明,对分辨率为576×768的图像处理时间仅为0.517 s,且视觉效果和客观指标比现有算法均有不同程度的提高.与现有图像去雾算法相比,本

  9. The satellite based augmentation system – EGNOS for non-precision approach global navigation satellite system

    Directory of Open Access Journals (Sweden)

    Andrzej FELLNER

    2012-01-01

    Full Text Available First in the Poland tests of the EGNOS SIS (Signal in Space were conducted on 5th October 2007 on the flight inspection with SPAN (The Synchronized Position Attitude Navigation technology at the Mielec airfield. This was an introduction to a test campaign of the EGNOS-based satellite navigation system for air traffic. The advanced studies will be performed within the framework of the EGNOS-APV project in 2011. The implementation of the EGNOS system to APV-I precision approach operations, is conducted according to ICAO requirements in Annex 10. Definition of usefulness and certification of EGNOS as SBAS (Satellite Based Augmentation System in aviation requires thorough analyses of accuracy, integrity, continuity and availability of SIS. Also, the project will try to exploit the excellent accuracy performance of EGNOS to analyze the implementation of GLS (GNSS Landing System approaches (Cat I-like approached using SBAS, with a decision height of 200 ft. Location of the EGNOS monitoring station Rzeszów, located near Polish-Ukrainian border, being also at the east border of planned EGNOS coverage for ECAC states is very useful for SIS tests in this area. According to current EGNOS programmed schedule, the project activities will be carried out with EGNOS system v2.2, which is the version released for civil aviation certification. Therefore, the project will allow demonstrating the feasibility of the EGNOS certifiable version for civil applications.

  10. GPS SATELLITE SIMULATOR SIGNAL ESTIMATION BASED ON ANN

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Multi-channel Global Positioning System (GPS) satellite signal simulator is used to provide realistic test signals for GPS receivers and navigation systems. In this paper, signals arriving the antenna of GPS receiver are analyzed from the viewpoint of simulator design. The estimation methods are focused of which several signal parameters are difficult to determine directly according to existing experiential models due to various error factors. Based on the theory of Artificial Neural Network (ANN), an approach is proposed to simulate signal propagation delay,carrier phase, power, and other parameters using ANN. The architecture of the hardware-in-the-loop test system is given. The ANN training and validation process is described. Experimental results demonstrate that the ANN designed can statistically simulate sample data in high fidelity.Therefore the computation of signal state based on this ANN can meet the design requirement,and can be directly applied to the development of multi-channel GPS satellite signal simulator.

  11. Fog Computing to protect real and sensitivity information in Cloud

    Directory of Open Access Journals (Sweden)

    Thogaricheti Ashwini

    2015-03-01

    Full Text Available Cloud computing can simply be described as computing based on the internet. In the past, people depended on physical computer storage or servers to run their programs. However, with the introduction of cloud computing, people as well as business enterprises can now access their programs through the internet. Due this ease, software companies and other agencies are shifting more towards cloud computing environment. To achieve better operational efficiency in many organizations and small or medium agencies is using Cloud environment for managing their data. It is a combination of a number of computing strategies and concepts such as Service Oriented Architecture (SOA, virtualization and other which rely on the Internet. Cloud Computing provides an easy way for accessing, managing and computation of user data, but it also has some severe security risks. Very common risks now days are data theft attacks. Data theft considered one of the top threats to cloud computing by the Cloud Security Alliance is. To deal with such cases and malicious intruders there are some techniques which are used to secure user data. A new technology called “Fog computing” is gaining attention of the cloud users nowadays. Fog computing improves the Quality of service and also reduces latency. According to Cisco, due to its wide geographical distribution the Fog computing is well suited for real time analytics and big data.Fog computing is a paradigm that extends Cloud computing and services to the edge of the network. Similar to Cloud, Fog provides data, compute, storage, and application services to end-users.

  12. Satellite Formation Design for Space Based Radar Applications

    Science.gov (United States)

    2007-07-30

    Practical Guidance Methodology for Relative Motion of LEO Spacecraft Based on the Clohessy-Wiltshire Equations,” AAS Paper 04-252, AAS/AIAA Space...Non- Circular Reference Orbit," AAS Paper 01-222, AAS/AIAA Space Flight Mechanics Meeting, Santa Barbara, CA, Feb 11-16, 2001. 11. D. Brouwer ...Small Eccentricities or Inclinations in the Brouwer Theory of the Artificial Satellite,” The Astronomical Journal, Vol. 68, October 1963, pp. 555

  13. On the fog variability over south Asia

    Energy Technology Data Exchange (ETDEWEB)

    Syed, F.S. [Stockholm University, Department of Meteorology, Stockholm (Sweden); Pakistan Meteorological Department, Islamabad (Pakistan); Koernich, H.; Tjernstroem, M. [Stockholm University, Department of Meteorology, The Bert Bolin Centre for Climate Research, Stockholm (Sweden)

    2012-12-15

    An increasing trend in fog frequencies over south Asia during winter in the last few decades has resulted in large economical losses and has caused substantial difficulties in the daily lives of people. In order to better understand the fog phenomenon, we investigated the climatology, inter-annual variability and trends in the fog occurrence from 1976 to 2010 using observational data from 82 stations, well distributed over India and Pakistan. Fog blankets large area from Pakistan to Bangladesh across north India from west to east running almost parallel to south of the Himalayas. An EOF analysis revealed that the fog variability over the whole region is coupled and therefore must be governed by some large scale phenomenon on the inter-annual time scale. Significant positive trends were found in the fog frequency but this increase is not gradual, as with the humidity, but comprises of two distinct regimes shifts, in 1990 and 1998, with respect to both mean and variance. The fog is also detected in ERA-Interim 3 hourly, surface and model level forecast data when using the concept of ''cross-over temperature'' combined with boundary layer stability. This fog index is able to reproduce the regime shift around 1998 and shows that the method can be applied to analyze fog over south Asia. The inter-annual variability seems to be associated with the wave train originating from the North Atlantic in the upper troposphere that when causing higher pressure over the region results in an increased boundary layer stability and surface-near relative humidity. The trend and shifts in the fog occurrence seems to be associated with the gradual increasing trend in relative humidity from 1990 onwards. (orig.)

  14. On the fog variability over south Asia

    Science.gov (United States)

    Syed, F. S.; Körnich, H.; Tjernström, M.

    2012-12-01

    An increasing trend in fog frequencies over south Asia during winter in the last few decades has resulted in large economical losses and has caused substantial difficulties in the daily lives of people. In order to better understand the fog phenomenon, we investigated the climatology, inter-annual variability and trends in the fog occurrence from 1976 to 2010 using observational data from 82 stations, well distributed over India and Pakistan. Fog blankets large area from Pakistan to Bangladesh across north India from west to east running almost parallel to south of the Himalayas. An EOF analysis revealed that the fog variability over the whole region is coupled and therefore must be governed by some large scale phenomenon on the inter-annual time scale. Significant positive trends were found in the fog frequency but this increase is not gradual, as with the humidity, but comprises of two distinct regimes shifts, in 1990 and 1998, with respect to both mean and variance. The fog is also detected in ERA-Interim 3 hourly, surface and model level forecast data when using the concept of "cross-over temperature" combined with boundary layer stability. This fog index is able to reproduce the regime shift around 1998 and shows that the method can be applied to analyze fog over south Asia. The inter-annual variability seems to be associated with the wave train originating from the North Atlantic in the upper troposphere that when causing higher pressure over the region results in an increased boundary layer stability and surface-near relative humidity. The trend and shifts in the fog occurrence seems to be associated with the gradual increasing trend in relative humidity from 1990 onwards.

  15. Efficient enhancing scheme for TCP performance over satellite-based internet

    Institute of Scientific and Technical Information of China (English)

    Wang Lina; Gu Xuemai

    2007-01-01

    Satellite link characteristics drastically degrade transport control protocol (TCP) performance. An efficient performance enhancing scheme is proposed. The improvement of TCP performance over satellite-based Intemet is accomplished by protocol transition gateways at each end ora satellite link. The protocol which runs over a satellite link executes the receiver-driven flow control and acknowledgements- and timeouts-based error control strategies. The validity of this TCP performance enhancing scheme is verified by a series of simulation experiments. Results show that the proposed scheme can efficiently enhance the TCP performance over satellite-based Intemet and ensure that the available bandwidth resources of the satellite link are fully utilized.

  16. Biomass prediction model in maize based on satellite images

    Science.gov (United States)

    Mihai, Herbei; Florin, Sala

    2016-06-01

    Monitoring of crops by satellite techniques is very useful in the context of precision agriculture, regarding crops management and agricultural production. The present study has evaluated the interrelationship between maize biomass production and satellite indices (NDVI and NDBR) during five development stages (BBCH code), highlighting different levels of correlation. Biomass production recorded was between 2.39±0.005 t ha-1 (12-13 BBCH code) and 51.92±0.028 t ha-1 (83-85 BBCH code), in relation to vegetation stages studied. Values of chlorophyll content ranged from 24.1±0.25 SPAD unit (12-13 BBCH code) to 58.63±0.47 SPAD unit (71-73 BBCH code), and the obtained satellite indices ranged from 0.035641±0.002 and 0.320839±0.002 for NDVI indices respectively 0.035095±0.034 and 0.491038±0.018 in the case of NDBR indices. By regression analysis it was possible to obtain predictive models of biomass in maize based on the satellite indices, in statistical accurate conditions. The most accurate prediction was possible based on NDBR index (R2 = 0.986, F = 144.23, p<0.001, RMSE = 1.446), then based on chlorophyll content (R2 = 0.834, F = 16.14, p = 0.012, RMSE = 6.927) and NDVI index (R2 = 0.682, F = 3.869, p = 0.116, RMSE = 12.178).

  17. SAMIRA - SAtellite based Monitoring Initiative for Regional Air quality

    Science.gov (United States)

    Schneider, Philipp; Stebel, Kerstin; Ajtai, Nicolae; Diamandi, Andrei; Horalek, Jan; Nicolae, Doina; Stachlewska, Iwona; Zehner, Claus

    2016-04-01

    Here, we present a new ESA-funded project entitled Satellite based Monitoring Initiative for Regional Air quality (SAMIRA), which aims at improving regional and local air quality monitoring through synergetic use of data from present and upcoming satellites, traditionally used in situ air quality monitoring networks and output from chemical transport models. Through collaborative efforts in four countries, namely Romania, Poland, the Czech Republic and Norway, all with existing air quality problems, SAMIRA intends to support the involved institutions and associated users in their national monitoring and reporting mandates as well as to generate novel research in this area. Despite considerable improvements in the past decades, Europe is still far from achieving levels of air quality that do not pose unacceptable hazards to humans and the environment. Main concerns in Europe are exceedances of particulate matter (PM), ground-level ozone, benzo(a)pyrene (BaP) and nitrogen dioxide (NO2). While overall sulfur dioxide (SO2) emissions have decreased in recent years, regional concentrations can still be high in some areas. The objectives of SAMIRA are to improve algorithms for the retrieval of hourly aerosol optical depth (AOD) maps from SEVIRI, and to develop robust methods for deriving column- and near-surface PM maps for the study area by combining satellite AOD with information from regional models. The benefit to existing monitoring networks (in situ, models, satellite) by combining these datasets using data fusion methods will be tested for satellite-based NO2, SO2, and PM/AOD. Furthermore, SAMIRA will test and apply techniques for downscaling air quality-related EO products to a spatial resolution that is more in line with what is generally required for studying urban and regional scale air quality. This will be demonstrated for a set of study sites that include the capitals of the four countries and the highly polluted areas along the border of Poland and the

  18. Revisiting the fog bottle experiment

    Science.gov (United States)

    Kamcharean, C.; Khanchong, C.; Wattanakasiwich, P.

    2016-11-01

    In this article we propose an irreversible adiabatic expansion model, modified from previous work, to explain the fog bottle experiment. Our model divides the phenomenon into five thermodynamic states, and we include in our calculation irreversible work pushing a stopper out of the bottle and heat gain from the condensation of saturated vapour. In the experiment, thermodynamic variables including pressure and temperature as functions of time were measured. The work done in pushing the stopper out was measured and the condensation heat was determined using the Clausius-Clapeyron equation to determine saturated vapour pressure. As a result, fog formation was explained through a phase diagram of water showing the saturated vapour pressure during irreversible adiabatic expansion. Also, state variables (P, V and T) and the entropy change of the real process were compared with the reversible and irreversible adiabatic expansion and our modified process. Using a P-T diagram, we show that the amount of reversible work is always higher than the amount of irreversible work, due to dissipative work. According to our modified model, the dissipative work and the heat transferred from condensation cause irreversibility or {{Δ }}{S}{{t}{{o}}{{t}}{{a}}{{l}}}\\gt 0.

  19. IFCIoT: Integrated Fog Cloud IoT Architectural Paradigm for Future Internet of Things

    OpenAIRE

    Munir, Arslan; Kansakar, Prasanna; Khan, Samee U.

    2017-01-01

    We propose a novel integrated fog cloud IoT (IFCIoT) architectural paradigm that promises increased performance, energy efficiency, reduced latency, quicker response time, scalability, and better localized accuracy for future IoT applications. The fog nodes (e.g., edge servers, smart routers, base stations) receive computation offloading requests and sensed data from various IoT devices. To enhance performance, energy efficiency, and real-time responsiveness of applications, we propose a reco...

  20. Efficient Satellite Scheduling Based on Improved Vector Evaluated Genetic Algorithm

    Directory of Open Access Journals (Sweden)

    Tengyue Mao

    2012-03-01

    Full Text Available Satellite scheduling is a typical multi-peak, many-valley, nonlinear multi-objective optimization problem. How to effectively implement the satellite scheduling is a crucial research in space areas.This paper mainly discusses the performance of VEGA (Vector Evaluated Genetic Algorithm based on the study of basic principles of VEGA algorithm, algorithm realization and test function, and then improves VEGA algorithm through introducing vector coding, new crossover and mutation operators, new methods to assign fitness and hold good individuals. As a result, the diversity and convergence of improved VEGA algorithm of improved VEGA algorithm have been significantly enhanced and will be applied to Earth-Mars orbit optimization. At the same time, this paper analyzes the results of the improved VEGA, whose results of performance analysis and evaluation show that although VEGA has a profound impact upon multi-objective evolutionary research,  multi-objective evolutionary algorithm on the basis of Pareto seems to be a more effective method to get the non-dominated solutions from the perspective of diversity and convergence of experimental result. Finally, based on Visual C + + integrated development environment, we have implemented improved vector evaluation algorithm in the satellite scheduling.

  1. Covariance analysis of differential drag-based satellite cluster flight

    Science.gov (United States)

    Ben-Yaacov, Ohad; Ivantsov, Anatoly; Gurfil, Pini

    2016-06-01

    One possibility for satellite cluster flight is to control relative distances using differential drag. The idea is to increase or decrease the drag acceleration on each satellite by changing its attitude, and use the resulting small differential acceleration as a controller. The most significant advantage of the differential drag concept is that it enables cluster flight without consuming fuel. However, any drag-based control algorithm must cope with significant aerodynamical and mechanical uncertainties. The goal of the current paper is to develop a method for examination of the differential drag-based cluster flight performance in the presence of noise and uncertainties. In particular, the differential drag control law is examined under measurement noise, drag uncertainties, and initial condition-related uncertainties. The method used for uncertainty quantification is the Linear Covariance Analysis, which enables us to propagate the augmented state and filter covariance without propagating the state itself. Validation using a Monte-Carlo simulation is provided. The results show that all uncertainties have relatively small effect on the inter-satellite distance, even in the long term, which validates the robustness of the used differential drag controller.

  2. Satellite Imagery Assisted Road-Based Visual Navigation System

    Science.gov (United States)

    Volkova, A.; Gibbens, P. W.

    2016-06-01

    There is a growing demand for unmanned aerial systems as autonomous surveillance, exploration and remote sensing solutions. Among the key concerns for robust operation of these systems is the need to reliably navigate the environment without reliance on global navigation satellite system (GNSS). This is of particular concern in Defence circles, but is also a major safety issue for commercial operations. In these circumstances, the aircraft needs to navigate relying only on information from on-board passive sensors such as digital cameras. An autonomous feature-based visual system presented in this work offers a novel integral approach to the modelling and registration of visual features that responds to the specific needs of the navigation system. It detects visual features from Google Earth* build a feature database. The same algorithm then detects features in an on-board cameras video stream. On one level this serves to localise the vehicle relative to the environment using Simultaneous Localisation and Mapping (SLAM). On a second level it correlates them with the database to localise the vehicle with respect to the inertial frame. The performance of the presented visual navigation system was compared using the satellite imagery from different years. Based on comparison results, an analysis of the effects of seasonal, structural and qualitative changes of the imagery source on the performance of the navigation algorithm is presented. * The algorithm is independent of the source of satellite imagery and another provider can be used

  3. Entropy-Based Block Processing for Satellite Image Registration

    Directory of Open Access Journals (Sweden)

    Ikhyun Lee

    2012-11-01

    Full Text Available Image registration is an important task in many computer vision applications such as fusion systems, 3D shape recovery and earth observation. Particularly, registering satellite images is challenging and time-consuming due to limited resources and large image size. In such scenario, state-of-the-art image registration methods such as scale-invariant feature transform (SIFT may not be suitable due to high processing time. In this paper, we propose an algorithm based on block processing via entropy to register satellite images. The performance of the proposed method is evaluated using different real images. The comparative analysis shows that it not only reduces the processing time but also enhances the accuracy.

  4. Chaos Based Secure IP Communications over Satellite DVB

    Science.gov (United States)

    Caragata, Daniel; El Assad, Safwan; Tutanescu, Ion; Sofron, Emil

    2010-06-01

    The Digital Video Broadcasting—Satellite (DVB-S) standard was originally conceived for TV and radio broadcasting. Later, it became possible to send IP packets using encapsulation methods such as Multi Protocol Encapsulation, MPE, or Unidirectional Lightweight Encapsulation, ULE. This paper proposes a chaos based security system for IP communications over DVB-S with ULE encapsulation. The proposed security system satisfies all the security requirements while respecting the characteristics of satellite links, such as the importance of efficient bandwidth utilization and high latency time. It uses chaotic functions to generate the keys and to encrypt the data. The key management is realized using a multi-layer architecture. A theoretical analysis of the system and a simulation of FTP and HTTP traffic are presented and discussed to show the cost of the security enhancement and to provide the necessary tools for security parameters setup.

  5. Fogging formulations for fixation of particulate contamination in ductwork and enclosures

    Energy Technology Data Exchange (ETDEWEB)

    Maresca, Jr., Joseph W.; Kostelnik, Lori M.; Kriskivich, James R.; Demmer, Rick L.; Tripp, Julia L.

    2015-09-08

    A method and an apparatus using aqueous fixatives for fogging of ventilation ductwork, enclosures, or buildings containing dust, lint, and particulates that may be contaminated by radionuclides and other dangerous or unsafe particulate contaminants, which method and apparatus are capable of (1) obtaining full coverage within the ductwork and (2) penetrating and fixing the lint, dust and large particles present in the ductwork so that no airborne particles are released during or after the application of the fixative. New aqueous fogging solutions outperform conventional glycerin-based solutions. These aqueous solutions will fog using conventional methods of application and contain a surfactant to aid wetting and penetration of the lint and dust, a binder to stabilize loose or respirable particles, and an agent to aid in fogging and enhance adhesiveness. The solutions are safe and easy to use.

  6. Characterization of Fogging and Develop-Loading Effects in Electron-Beam Direct-Writing Technology

    Science.gov (United States)

    Kon, Jun-ichi; Kojima, Yoshinori; Takahashi, Yasushi; Maruyama, Takashi; Sugatani, Shinji

    2012-06-01

    We investigated long-range critical dimension (CD) error factors, such as fogging and develop loading, to improve CD uniformity in electron-beam direct-writing (EBDW) technology. It was found that the impact of both effects reached 20 mm and the CD of the monitor pattern decreased by no less than 10%. Fogging and develop loading were separated by comparing the newly designed test patterns that were exposed using both EB and a krypton-fluoride excimer laser. We confirmed that the impact of fogging and develop loading by arranging dummy patterns with a density of 40% was estimated to be +8.9 and -18.9% in the CD, respectively. Based on success in separating each effect, fogging and develop loading were decreased by applying an antistatic agent and multipuddle development, respectively.

  7. A Secure and Verifiable Outsourced Access Control Scheme in Fog-Cloud Computing

    Science.gov (United States)

    Fan, Kai; Wang, Junxiong; Wang, Xin; Li, Hui; Yang, Yintang

    2017-01-01

    With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient. PMID:28737733

  8. A Secure and Verifiable Outsourced Access Control Scheme in Fog-Cloud Computing.

    Science.gov (United States)

    Fan, Kai; Wang, Junxiong; Wang, Xin; Li, Hui; Yang, Yintang

    2017-07-24

    With the rapid development of big data and Internet of things (IOT), the number of networking devices and data volume are increasing dramatically. Fog computing, which extends cloud computing to the edge of the network can effectively solve the bottleneck problems of data transmission and data storage. However, security and privacy challenges are also arising in the fog-cloud computing environment. Ciphertext-policy attribute-based encryption (CP-ABE) can be adopted to realize data access control in fog-cloud computing systems. In this paper, we propose a verifiable outsourced multi-authority access control scheme, named VO-MAACS. In our construction, most encryption and decryption computations are outsourced to fog devices and the computation results can be verified by using our verification method. Meanwhile, to address the revocation issue, we design an efficient user and attribute revocation method for it. Finally, analysis and simulation results show that our scheme is both secure and highly efficient.

  9. Fingers-of-God effect of infalling satellite galaxies

    CERN Document Server

    Hikage, Chiaki

    2015-01-01

    Understanding the nonlinear property of redshift-space distortion, i.e., Fingers-of-God (FoG) effect, is important for the redshift-space distortion studies to test gravity models. FoG effect has been usually attributed to the random motion of galaxies inside the clusters. In this paper, we demonstrate the importance of the coherent infalling motion of satellite galaxies toward the cluster center. We analytically derive the satellite velocity distribution due to the infall motion together with the random motion and show that the velocity distribution becomes far from Maxwellian when the infalling motion is dominant. We use simulated subhalo catalogs to find that the contribution of infall motion is important for massive subhalos and that their velocity distribution has top-hat like shape as expected from our analytic model.We also study the FoG effect due to infall motion on the redshift-space power spectrum. Using the simulated subhalo catalogs based on the halo occupation distribution of luminous red galaxi...

  10. Oxygen Isotopic Composition of Nitrate and Sulfate in Fog and River water in Podocarpus National Forest, Ecuador

    Science.gov (United States)

    Brothers, L. A.; Fabian, P.; Thiemens, M. H.

    2006-12-01

    The eastern slopes of the Andean rainforests of Ecuador possess some of the highest plant biodiversity found on the planet; however, these ecosystems are in jeopardy because region is experiences one of the highest deforestation rates in South America. This rainforest characterized by high acidity and low nutrient soils and experiences natural process which are both destabilizing and stabilizing to biodiversity rendering this a unique, though sensitive environment. There is increased concern that anthropogenic activities are affecting rainforests and could lead to higher extinction rates, changes in the biodiversity and far reaching effects on the global troposphere. Measurements of nitrate and sulfate in rain and fog water have shown periods of elevated concentrations in the Podocarpus National Park near Loja, Ecuador. These high episodes contribute to annual deposition rates that are comparable to polluted central Europe. Significant anthropogenic sources near this region are lacking and it is believed that the majority of the nitrate and sulfate pollution can be attributed to biomass burning in the Amazon basin. Concentration measurements do not elucidate the source of high nitrate and sulfate pollution; however, by measuring all three stable isotopes of oxygen in nitrate and sulfate from fog and river water provides a new way to examine the impacts of biomass burning on the region. By using stable isotope techniques atmospheric nitrate and sulfate can be resolved from terrestrial sources. This provides an unique way to trace the contributions from the biomass burning and farming sources. Current research at the field station monitors sulfate and nitrate concentrations in rain and fog water by standard methods to investigate water and nutrient pathways along with data from satellite and ground based remote sensing, in-situ observations and numerical models.

  11. Interoperability of satellite-based augmentation systems for aircraft navigation

    Science.gov (United States)

    Dai, Donghai

    The Federal Aviation Administration (FAA) is pioneering a transformation of the national airspace system from its present ground based navigation and landing systems to a satellite based system using the Global Positioning System (GPS). To meet the critical safety-of-life aviation positioning requirements, a Satellite-Based Augmentation System (SBAS), the Wide Area Augmentation System (WAAS), is being implemented to support navigation for all phases of flight, including Category I precision approach. The system is designed to be used as a primary means of navigation, capable of meeting the Required Navigation Performance (RNP), and therefore must satisfy the accuracy, integrity, continuity and availability requirements. In recent years there has been international acceptance of Global Navigation Satellite Systems (GNSS), spurring widespread growth in the independent development of SBASs. Besides the FAA's WAAS, the European Geostationary Navigation Overlay Service System (EGNOS) and the Japan Civil Aviation Bureau's MTSAT-Satellite Augmentation System (MSAS) are also being actively developed. Although all of these SBASs can operate as stand-alone, regional systems, there is increasing interest in linking these SBASs together to reduce costs while improving service coverage. This research investigated the coverage and availability improvements due to cooperative efforts among regional SBAS networks. The primary goal was to identify the optimal interoperation strategies in terms of performance, complexity and practicality. The core algorithms associated with the most promising concepts were developed and demonstrated. Experimental verification of the most promising concepts was conducted using data collected from a joint international test between the National Satellite Test Bed (NSTB) and the EGNOS System Test Bed (ESTB). This research clearly shows that a simple switch between SBASs made by the airborne equipment is the most effective choice for achieving the

  12. 基于OSG的实时烟雾模拟的研究与应用%Research and application for simulation of real-time fog based on OSG

    Institute of Scientific and Technical Information of China (English)

    侯美华; 吴志红; 陈楷民

    2011-01-01

    为了模拟出具有实时性和真实感的烟雾效果,分析了传统烟雾的模拟方法,提出了一种基于OSG平台下的实时烟雾模拟方法.该方法采用流体力学纳维-斯托克斯方程组作为基本物理模型,通过添加漩涡约束力来达到真实性的要求.由于NS方程求解的复杂性和CPU计算的限制性,在方程解算上,提出一种基于GPU的采用半拉格朗日方法、雅克比迭代法等稳定的求解方法,并结合体绘制技术来实现实时烟雾的模拟.实验结果表明,该方法能快速模拟出实时、逼真的烟雾效果.%To simulate a real-time and realistic smoke effects, an OSG platform-based method to simulate the fog in real-time is proposed,by analyzing the traditional simulation methods of fog. Navier-Stokes equations as the basic physical model are used, and a vorticity confinement force is added to achieve authenticity. Because of the complexity of the Navier-Stokes equations and the restrictive of CPU calculation, in numerical calculation, a graphic processing unit (GPU) -based method which realized the real-time simulation by using such stable solving method as Semi-Lagrangian scheme, Jacobi iteration method is designed. The experimental results show that the method is able to simulate smoke quickly with real-time and realistic characteristic.

  13. Convolutional neural network features based change detection in satellite images

    Science.gov (United States)

    Mohammed El Amin, Arabi; Liu, Qingjie; Wang, Yunhong

    2016-07-01

    With the popular use of high resolution remote sensing (HRRS) satellite images, a huge research efforts have been placed on change detection (CD) problem. An effective feature selection method can significantly boost the final result. While hand-designed features have proven difficulties to design features that effectively capture high and mid-level representations, the recent developments in machine learning (Deep Learning) omit this problem by learning hierarchical representation in an unsupervised manner directly from data without human intervention. In this letter, we propose approaching the change detection problem from a feature learning perspective. A novel deep Convolutional Neural Networks (CNN) features based HR satellite images change detection method is proposed. The main guideline is to produce a change detection map directly from two images using a pretrained CNN. This method can omit the limited performance of hand-crafted features. Firstly, CNN features are extracted through different convolutional layers. Then, a concatenation step is evaluated after an normalization step, resulting in a unique higher dimensional feature map. Finally, a change map was computed using pixel-wise Euclidean distance. Our method has been validated on real bitemporal HRRS satellite images according to qualitative and quantitative analyses. The results obtained confirm the interest of the proposed method.

  14. Fog and Dew Collection Projects in Croatia

    OpenAIRE

    Mileta, M.; Beysens, D; Nikolayev, Vadim; Milimouk, I; Clus, O.; Muselli, M

    2006-01-01

    accessible sur http://balwois.mpl.ird.fr/balwois/administration/full_paper/ffp-587.pdf.; International audience; The present paper discusses the fog and dew water collection in Croatia. Zavizan, the highest meteorological station in Croatia( 1594m) is chosen for collecting of fog water with a standard fog collector (SFC). The highest daily collection rate was 27.8 L / m². The highest daily collection rate in days without rain was 19.1 l/m². Dew is also a noticeable source of water, especially...

  15. The boundary layer characteristics in the heavy fog formation process over Beijing and its adjacent areas

    Institute of Scientific and Technical Information of China (English)

    ZHANG; Guangzhi; BIAN; Lingeng; WANG; Jizhi; YANG; Yuanqi

    2005-01-01

    By utilizing the Atmospheric Boundary Layer (ABL) observational data made available from the project "973" under the auspices of the Ministry of Science and Technology of the People's Republic of China - entitled the Beijing City Air Pollution Observation Field Experiment (BECAPEX), including the measurements by a wind profiler, captive airships, tower-based boundary layer wind and temperature gradient observational instruments (ultrasonic anemometers and electronic thermometers), air composition samplers, conventional upper-air, surface and Automatic Weather Stations (AWS) observations, this paper herewith analyzes, in a comprehensive manner, the occurrence of a heavy fog event over Beijing in February 2001, including its formation, development, persistence, dynamic and thermodynamic features as well as evolving stratification structures within the boundary layer at different stages. The results suggested: (i) as a typical case of urban heavy fog, before the fog onset over Beijing, a temperature inversion existed in the lower atmosphere, the smokes and the pollutants like SO2 and NO2 had been accumulated at a lower level. Proceeding the fog event, with the increase of SO2 and NO2 concentrations, condensability increased sharply. On the contrary, during the fog process, with increasing condensability, SO2 and NO2 concentrations decreased. This indicated that, acting as condensation nucleus, these accumulated pollutants were playing a key role in catalyzing the fog condensation. (ii) By analyzing mean gradient-, pulsation- and turbulence-distribution patterns derived from the wind measurements taken by the aforementioned tower-based instruments, they all indicated that about 10 hours before the fog onset, a signal foretelling potential strong disturbances in the lower boundary layer was detected, and a significant rise of both mean and disturbance kinetic energies was observed, revealing that the low-level wind shear was strengthened before the fog onset

  16. Research on fog-degraded image restoration based on bilateral filter of RGB channel%基于双边滤波的RGB通道去雾算法研究

    Institute of Scientific and Technical Information of China (English)

    游谦; 黎英; 李玉成; 赵虎; 王振

    2014-01-01

    因大气光的散射和入射光的衰减,大雾天气下捕获到的图像质量呈指数系数下降。为改善退化图像的视觉效果,利用暗原色先验信息获得大气光;根据单幅雾天图像RGB通道强度估计场景深度图;同时在明亮区域引入一种容差阈值,避免了这部分区域场景深度的错误估计,使用带边缘保持的双边滤波器对求得的场景深度图进一步处理;利用大气散射模型实现了图像复原。实验结果表明,改进后的算法有效提高了雾天退化图像的视觉效果。%Due to scattering of atmospheric light and attenuation of incident light, the quality of images captured under foggy conditions will be reduced exponentially to the scene depth. In order to improve the visual effect of the degraded image, this paper makes use of the dark channel to estimate the air light. According to the strength of RGB channel, then, the scene depth map is estimated from a single fog image. Moreover, this paper introduces a tolerance threshold in the bright region to avoid the error estimates of the scene depth. A bilateral filter with edge-preserving is utilized to further process the scene depth map. A clear image can be recovered based on the atmospheric scattering model. Experiment results show that the proposed improved algorithm can enhance the visibility of fog-degraded images effectively.

  17. Fog-degraded Image Enhancement Based on Single-scale Retinex%基于单尺度 Re ti nex 雾天降质图像增强算法

    Institute of Scientific and Technical Information of China (English)

    刘松; 孙东; 卢一相

    2013-01-01

    According to degraded phenomena of images taken in foggy weather ,this paper proposesd an algorithm of foggy image enhancement based on Single-Scale Retinex .The proposed algorithm first conversed RGB color space to HSI space .Using Retinex to estimate the fog veil of brightness whose distribution was in accord with the real fog density of the scene .The reflectance image could be obtained by subtracting the veil from the degraded image . Then ,using bilateral filtering extracted the reflectance information included in the veil .The result image could be obtained by fusing the both reflectance images ,using linear stretching to adjust saturation and conversing to RGB color space .Experiments show that the algorithm is more effective in foggy weather .%针对雾天采集的图像的退化现象,提出一种基于单尺度Retinex的雾天图像增强的算法。此算法首先把图像从RGB空间转换到 HSI空间,对亮度I分量用单尺度Retinex估计出与场景深度信息相关的雾气遮罩度,从亮度I分量中除去所估算的雾气遮罩度,即可得到亮度I分量的反射分量;然后利用双边滤波器,提取雾气遮罩度的反射分量,将该反射分量和亮度I的反射分量进行融合,并对饱和度S进行线性拉伸;最后转换到RGB空间即可得到增强后的图像。实验结果表明,该方法对雾天退化图像效果较好。

  18. Laser Imaging Video Camera Sees Through Fire, Fog, Smoke

    Science.gov (United States)

    2015-01-01

    Under a series of SBIR contracts with Langley Research Center, inventor Richard Billmers refined a prototype for a laser imaging camera capable of seeing through fire, fog, smoke, and other obscurants. Now, Canton, Ohio-based Laser Imaging through Obscurants (LITO) Technologies Inc. is demonstrating the technology as a perimeter security system at Glenn Research Center and planning its future use in aviation, shipping, emergency response, and other fields.

  19. Fog forecasting: ``old fashioned'' semi-empirical methods from radio sounding observations versus ``modern'' numerical models

    Science.gov (United States)

    Holtslag, M. C.; Steeneveld, G. J.; Holtslag, A. A. M.

    2010-07-01

    Fog forecasting is a very challenging task due to the local and small-scale nature of the relevant physical processes and land surface heterogeneities. Despite the many research efforts, numerical models remain to have difficulties with fog forecasting, and forecast skill from direct model output is relatively poor. In order to put the progress of fog forecasting in the last decades into a historical perspective, we compare the fog forecasting skill of a semi-empirical method based on radio sounding observations (developed in the 60s and 70s) with the forecasting skill of a state-of-the-art numerical weather prediction model (MM5) for The Netherlands. The semi-empirical method under investigation, the Fog Stability Index, depends solely on the temperature difference between the surface and 850 hPa, the surface dew point depression and the wind speed at 850 hPa, and a threshold value to indicate the probability of fog in the coming hours. Using the critical success index (CSI) as a criterion for forecast quality, we find that the Fog Stability Index is a rather successful predictor for fog, with similar performance as MM5. The FSI could even been optimized for different observational stations in the Netherlands. Also, it appears that adding the 10 m wind as a predictor did not increase the CSI score for all stations. The results of the current study clearly indicate that the current state of knowledge requires improvement of the physical insight in different physical processes in order to beat simple semi-empirical methods.

  20. Particulate contribution to extinction of visible radiation: Pollution, haze, and fog

    Science.gov (United States)

    Elias, Thierry; Haeffelin, Martial; Drobinski, Philippe; Gomes, Laurent; Rangognio, Jerome; Bergot, Thierry; Chazette, Patrick; Raut, Jean-Christophe; Colomb, Michèle

    2009-06-01

    A data set acquired by eight particle-dedicated instruments set up on the SIRTA (Site Instrumental de Recherche par Télédétection Atmosphérique, which is French for Instrumented Site for Atmospheric Remote Sensing Research) during the ParisFog field campaign are exploited to document microphysical properties of particles contributing to extinction of visible radiation in variable situations. The study focuses on a 48-hour period when atmospheric conditions are highly variable: relative humidity changes between 50 and 100%, visibility ranges between 65 and 35 000 m, the site is either downwind the Paris area either under maritime influence. A dense and homogeneous fog formed during the night by radiative cooling. In 6 h, visibility decreased down from 30 000 m in the clear-sky regime to 65 m within the fog, because of advected urban pollution (factor 3 to 4 in visibility reduction), aerosol hydration (factor 20) and aerosol activation (factor 6). Computations of aerosol optical properties, based on Mie theory, show that extinction in clear-sky regime is due equally to the ultrafine modes and to the accumulation mode. Extinction by haze is due to hydrated aerosol particles distributed in the accumulation mode, defined by a geometric mean diameter of 0.6 μm and a geometric standard deviation of 1.4. These hydrated aerosol particles still contribute by 20 ± 10% to extinction in the fog. The complementary extinction is due to fog droplets distributed around the geometric mean diameter of 3.2 μm with a geometric standard deviation of 1.5 during the first fog development stage. The study also shows that the experimental set-up could not count all fog droplets during the second and third fog development stages.

  1. Fog/Low Visibility Forecasting from NCEP - Current Status and Performance

    Science.gov (United States)

    Zhou, B.; Dimego, G.; Gultepe, I.

    2010-07-01

    Low visibility(fog is very hazardous to air/land traffic and is beeing particularly emphasized at National Weather Service(NWS) of NOAA and in NextGen, a future Air Traffic Management System of Federal Aviation Administration (FAA), United States. As of now however, fog forecast is still not operational guidance from National Centers for Environment Prediction (NCEP), an official numerical weather prediction (NWP) center of NWS, due to its complexity and computational resource limitation. Instead, it is only diagnosed by local weather forecasters through either model output statistics (MOS) or other variables based upon their forecasting experience. Nevertheless, research on numerical fog prediction has been conducting at NCEP. Recently, in an effort to add it to NCEP’s operational guidance as a step to echo the requirement from NWS and the NextGen of FAA, low visibility/fog forecast was experimentally implemented and tested at NCEP. In this paper, predictions of fog and low visibility (fog from two ensemble forecast systems are also presented. One is the Short Range Ensemble Forecast System (SREF), the other is the Very Sort Range Ensemble Forecast System (VSREF). Through verifications, deterministically and probabilistically from November 2009 to March 2010 on North America, the fog and low visibility predictabilities for various models and ensembles are compared and discussed. The results show that the general performances of fog and low visibility prediction from the single model forecast systems are still low, but the application of ensemble, either in low or high resolution, has shed light on its performance improvement. Furthermore through this study, where the efforts should be focused on in the models or methods are also suggested.

  2. Fog water collection with SFC on the mountain Velebit (Croatia) during the period 2000-2009

    Science.gov (United States)

    Mileta, M.; Likso, T.

    2010-07-01

    Zavižan (1594 m above sea level) is the highest mountain station in Croatia and it is equipped with SFC (standard fog collector). It is situated on Velebit Mountain which is the boundary between maritime and continental climate. The methodology used was described in Schemenauer and Cereceda (1994) and is based on the use of the standard fog collector (SFC) of 1 m ² of polypropylene mesh. Fog water collection with SFC started in the summer 2000. With the annual mean temperature of 5. 1° C the year 2000 was the warmest year in the available measurements (1953-2009). A significant increase in annual temperature was observed during the whole period 2000-2009. Among ten the warmest years on Zavižan, five were observed in this century (2000, 2007, 2008, 2002 and 2009). The paper discusses the daily fog water amounts collected during the different long periods in the warm parts of the examined period 2000-2009. Fog water collected in days without precipitation are analysed separately. Also a number of days with fog in the monitoring period have been analysed with respect to the 1961-1990 reference period. Maximum one day value of 27.8 l /m² was recorded in October 2003, while the highest daily rate in days without rain was 19.0 l/m² in October 2002. Synoptic situation for days with maximum one day-value in 2009 has been analysed.

  3. No Such Thing as Menstrual Memory Fog

    Science.gov (United States)

    ... fullstory_167035.html No Such Thing as Menstrual Memory Fog Changes in hormones don't seem to ... negative impact of hormonal changes on [thinking and memory]," said the study's lead author, Brigitte Leeners. She's ...

  4. Fog interception by Ball moss (Tillandsia recurvata

    Directory of Open Access Journals (Sweden)

    G. Malda-Barrera

    2011-08-01

    Full Text Available Interception losses are a major influence in the water yield of vegetated areas. For most storms, rain interception results in less water reaching the ground. However, fog interception can increase the overall water storage capacity of the vegetation and once the storage is exceeded, fog drip is a common hydrological input. Fog interception is disregarded in water budgets of semiarid regions, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions and applying simulated rain or fog. Juvenile, vegetative specimens were used to determine the potential upperbound storage capacities. The storage capacity was proportional to dry weight mass. Interception storage capacity (Cmin was 0.19 and 0.56 mm for rainfall and fog respectively. The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted by rain. T. recurvata contributed 20 % to the rain interception capacity of their shrub hosts: Acacia farnesiana and Prosopis laevigata and; also potentially intercepted 4.8 % of the annual rainfall. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543 ± 77 vs. 325 ± 56 mg, p = 0.048. The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because potential storage capacity is very high, in the laboratory experiments it took up to 12 h at a rate of 0.26 l h−1 to reach saturation conditions

  5. Fog interception by Ball moss (Tillandsia recurvata)

    Science.gov (United States)

    Guevara-Escobar, A.; Cervantes-Jiménez, M.; Suzán-Azpiri, H.; González-Sosa, E.; Hernández-Sandoval, L.; Malda-Barrera, G.; Martínez-Díaz, M.

    2011-08-01

    Interception losses are a major influence in the water yield of vegetated areas. For most storms, rain interception results in less water reaching the ground. However, fog interception can increase the overall water storage capacity of the vegetation and once the storage is exceeded, fog drip is a common hydrological input. Fog interception is disregarded in water budgets of semiarid regions, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions and applying simulated rain or fog. Juvenile, vegetative specimens were used to determine the potential upperbound storage capacities. The storage capacity was proportional to dry weight mass. Interception storage capacity (Cmin) was 0.19 and 0.56 mm for rainfall and fog respectively. The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted by rain. T. recurvata contributed 20 % to the rain interception capacity of their shrub hosts: Acacia farnesiana and Prosopis laevigata and; also potentially intercepted 4.8 % of the annual rainfall. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543 ± 77 vs. 325 ± 56 mg, p = 0.048). The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water recharge, because potential storage capacity is very high, in the laboratory experiments it took up to 12 h at a rate of 0.26 l h-1 to reach saturation conditions when fog was applied.

  6. A Time and Space-based Dynamic IP Routing in Broadband Satellite Networks

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The topology architecture, characteristics and routing technologies of broadband satellite networks are studied in this paper. The authors propose the routing scheme of satellite networks and design a time and space-based distributed routing algorithm whose complexity is O(1). Simulation results aiming at satellite mobility show that the new algorithm can determine the minimum propagation delay paths effectively.

  7. Scheduler for monitoring objects orbiting earth using satellite-based telescopes

    Energy Technology Data Exchange (ETDEWEB)

    Olivier, Scot S; Pertica, Alexander J; Riot, Vincent J; De Vries, Willem H; Bauman, Brian J; Nikolaev, Sergei; Henderson, John R; Phillion, Donald W

    2015-04-28

    An ephemeris refinement system includes satellites with imaging devices in earth orbit to make observations of space-based objects ("target objects") and a ground-based controller that controls the scheduling of the satellites to make the observations of the target objects and refines orbital models of the target objects. The ground-based controller determines when the target objects of interest will be near enough to a satellite for that satellite to collect an image of the target object based on an initial orbital model for the target objects. The ground-based controller directs the schedules to be uploaded to the satellites, and the satellites make observations as scheduled and download the observations to the ground-based controller. The ground-based controller then refines the initial orbital models of the target objects based on the locations of the target objects that are derived from the observations.

  8. Planning for a data base system to support satellite conceptual design

    Science.gov (United States)

    Claydon, C. R.

    1976-01-01

    The conceptual design of an automated satellite design data base system is presented. The satellite catalog in the system includes data for all earth orbital satellites funded to the hardware stage for launch between 1970 and 1980, and provides a concise compilation of satellite capabilities and design parameters. The cost of satellite subsystems and components will be added to the base. Data elements are listed and discussed. Sensor and science and applications opportunities catalogs will be included in the data system. Capabilities of the BASIS storage, retrieval, and analysis system are used in the system design.

  9. IUKF neural network modeling for FOG temperature drift

    Institute of Scientific and Technical Information of China (English)

    Feng Zha; Jiangning Xu; Jingshu Li; Hongyang He

    2013-01-01

    A novel neural network based on iterated unscented Kalman filter (IUKF) algorithm is established to model and com-pensate for the fiber optic gyro (FOG) bias drift caused by tempe-rature. In the network, FOG temperature and its gradient are set as input and the FOG bias drift is set as the expected output. A 2-5-1 network trained with IUKF algorithm is established. The IUKF algorithm is developed on the basis of the unscented Kalman filter (UKF). The weight and bias vectors of the hidden layer are set as the state of the UKF and its process and measurement equations are deduced according to the network architecture. To solve the unavoidable estimation deviation of the mean and covariance of the states in the UKF algorithm, iterative computation is introduced into the UKF after the measurement update. While the measure-ment noise R is extended into the state vectors before iteration in order to meet the statistic orthogonality of estimate and mea-surement noise. The IUKF algorithm can provide the optimized estimation for the neural network because of its state expansion and iteration. Temperature rise (-20-20◦C) and drop (70-20◦C) tests for FOG are carried out in an attemperator. The temperature drift model is built with neural network, and it is trained respec-tively with BP, UKF and IUKF algorithms. The results prove that the proposed model has higher precision compared with the back-propagation (BP) and UKF network models.

  10. Zenith Pass Problem of Inter-satellite Linkage Antenna Based on Program Guidance Method

    Institute of Scientific and Technical Information of China (English)

    Zhai Kun; Yang Di

    2008-01-01

    While adopting an elevation-over-azimuth architecture by an inter-satellite linkage antenna of a user satellite, a zenith pass problem always occurs when the antenna is tracing the tracking and data relay satellite (TDRS). This paper deals with this problem by way of,firstly, introducing movement laws of the inter-satellite linkage to predict the movement of the user satellite antenna followed by analyzing the potential pass moment and the actual one of the zenith pass in detail. A number of specific orbit altitudes for the user satellite that can remove the blindness zone are obtained. Finally, on the base of the predicted results from the movement laws of the inter-satellite linkage, the zenith pass tracing strategies for the user satellite antenna are designed under the program guidance using a trajectory preprocessor. Simulations have confirmed the reasonability and feasibility of the strategies in dealing with the zenith pass problem.

  11. The Quality of Fog Water Collected for Domestic and Agricultural Use in Chile.

    Science.gov (United States)

    Schemenauer, Robert S.; Cereceda, Pilar

    1992-03-01

    One exciting new application of meteorology is the prospect of using high-elevation fogs as an and land's water resource. This has now become reality in northern Chile where a pilot project has used 50 fog collectors to generate an average of 7200 1 of water per day during three drought years. The chemical composition of the fog water is of primary importance and is examined in this paper.A small, carefully cleaned fog-water collector was used at the site (elevation 780 m) to study the incoming fog (cloud). The ion and trace-element concentrations met Chilean and the World Health Organization's (WHO) drinking-water standards. The pH values, however, were at times extremely low. Samples from 1987 and 1988 were consistent with those from the larger dataset in 1989. The lowest observed pH was 3.46. The acidity was associated with high concentrations (89%) of excess sulfate in the 15 fog-water samples (based on Cl as the seawater tracer element). The NO3/SO4 equivalents ratio for the fog samples was 0.18, showing the dominance of SO4 in determining the acidity of the fog samples. The relative abundances of ions and trace elements in the dry deposition are very similar to those in the fog water, suggesting that the aerosols originate primarily from evaporated cloud droplets over the ocean. Based on enrichment-factor calculations (with Cl as the indicator element for seawater and A1 for the earth's crust), sea salts were the main source of Na+, Mg++, and Cl in the fog water; soil dust was the main source of Fe, Al and Ti; and other sources provided Ca++, K+, NH4+, Br SO4NO3 As,Cd,Pb,V,Mn,Ni,Cu,SrSb,and Ba in the fog water.The use of enrichment factors based on the relative abundances in soil extracts suggests that As, V, Cu, and Sr may be available from wetted soil dust.The output from the large (48 m2) fog collectors was also acceptable, except for several of the 24 trace elements, which exceeded the maximum allowable values in the first flush of water after a dry

  12. Advanced Multipath Mitigation Techniques for Satellite-Based Positioning Applications

    Directory of Open Access Journals (Sweden)

    Mohammad Zahidul H. Bhuiyan

    2010-01-01

    Full Text Available Multipath remains a dominant source of ranging errors in Global Navigation Satellite Systems (GNSS, such as the Global Positioning System (GPS or the future European satellite navigation system Galileo. Multipath is generally considered undesirable in the context of GNSS, since the reception of multipath can make significant distortion to the shape of the correlation function used for time delay estimation. However, some wireless communications techniques exploit multipath in order to provide signal diversity though in GNSS, the major challenge is to effectively mitigate the multipath, since we are interested only in the satellite-receiver transit time offset of the Line-Of-Sight (LOS signal for the receiver's position estimate. Therefore, the multipath problem has been approached from several directions in order to mitigate the impact of multipath on navigation receivers, including the development of novel signal processing techniques. In this paper, we propose a maximum likelihood-based technique, namely, the Reduced Search Space Maximum Likelihood (RSSML delay estimator, which is capable of mitigating the multipath effects reasonably well at the expense of increased complexity. The proposed RSSML attempts to compensate the multipath error contribution by performing a nonlinear curve fit on the input correlation function, which finds a perfect match from a set of ideal reference correlation functions with certain amplitude(s, phase(s, and delay(s of the multipath signal. It also incorporates a threshold-based peak detection method, which eventually reduces the code-delay search space significantly. However, the downfall of RSSML is the memory requirement which it uses to store the reference correlation functions. The multipath performance of other delay-tracking methods previously studied for Binary Phase Shift Keying-(BPSK- and Sine Binary Offset Carrier- (SinBOC- modulated signals is also analyzed in closed loop model with the new Composite

  13. Parameterization of oceanic whitecap fraction based on satellite observations

    Directory of Open Access Journals (Sweden)

    M. F. M. A. Albert

    2015-08-01

    Full Text Available In this study the utility of satellite-based whitecap fraction (W values for the prediction of sea spray aerosol (SSA emission rates is explored. More specifically, the study is aimed at improving the accuracy of the sea spray source function (SSSF derived by using the whitecap method through the reduction of the uncertainties in the parameterization of W by better accounting for its natural variability. The starting point is a dataset containing W data, together with matching environmental and statistical data, for 2006. Whitecap fraction W was estimated from observations of the ocean surface brightness temperature TB by satellite-borne radiometers at two frequencies (10 and 37 GHz. A global scale assessment of the data set to evaluate the wind speed dependence of W revealed a quadratic correlation between W and U10, as well as a relatively larger spread in the 37 GHz data set. The latter could be attributed to secondary factors affecting W in addition to U10. To better visualize these secondary factors, a regional scale assessment over different seasons was performed. This assessment indicates that the influence of secondary factors on W is for the largest part imbedded in the exponent of the wind speed dependence. Hence no further improvement can be expected by looking at effects of other factors on the variation in W explicitly. From the regional analysis, a new globally applicable quadratic W(U10 parameterization was derived. An intrinsic correlation between W and U10 that could have been introduced while estimating W from TB was determined, evaluated and presumed to lie within the error margins of the newly derived W(U10 parameterization. The satellite-based parameterization was compared to parameterizations from other studies and was applied in a SSSF to estimate the global SSA emission rate. The thus obtained SSA production for 2006 of 4.1 × 1012 kg is within previously reported estimates. While recent studies that account for

  14. Experimental FSO network availability estimation using interactive fog condition monitoring

    Science.gov (United States)

    Turán, Ján.; Ovseník, Łuboš

    2016-12-01

    Free Space Optics (FSO) is a license free Line of Sight (LOS) telecommunication technology which offers full duplex connectivity. FSO uses infrared beams of light to provide optical broadband connection and it can be installed literally in a few hours. Data rates go through from several hundreds of Mb/s to several Gb/s and range is from several 100 m up to several km. FSO link advantages: Easy connection establishment, License free communication, No excavation are needed, Highly secure and safe, Allows through window connectivity and single customer service and Compliments fiber by accelerating the first and last mile. FSO link disadvantages: Transmission media is air, Weather and climate dependence, Attenuation due to rain, snow and fog, Scattering of laser beam, Absorption of laser beam, Building motion and Air pollution. In this paper FSO availability evaluation is based on long term measured data from Fog sensor developed and installed at TUKE experimental FSO network in TUKE campus, Košice, Slovakia. Our FSO experimental network has three links with different physical distances between each FSO heads. Weather conditions have a tremendous impact on FSO operation in terms of FSO availability. FSO link availability is the percentage of time over a year that the FSO link will be operational. It is necessary to evaluate the climate and weather at the actual geographical location where FSO link is going to be mounted. It is important to determine the impact of a light scattering, absorption, turbulence and receiving optical power at the particular FSO link. Visibility has one of the most critical influences on the quality of an FSO optical transmission channel. FSO link availability is usually estimated using visibility information collected from nearby airport weather stations. Raw data from fog sensor (Fog Density, Relative Humidity, Temperature measured at each ms) are collected and processed by FSO Simulator software package developed at our Department. Based

  15. Fog interception by Ball moss (Tillandsia recurvata

    Directory of Open Access Journals (Sweden)

    G. Malda-Barrera

    2010-03-01

    Full Text Available Interception losses are a major influence in the water yield of vegetated areas. For most storms, interception results in less water reaching the ground. However, fog drip or occult precipitation can result in negative interception because small drops are deposited on all plant surfaces and subsequently fall to the ground once vegetation storage capacities are exceeded. Fog drip is normally disregarded, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions through applying simulated rain or fog. The storage capacity was proportional to dry weight mass. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543±77 vs. 325±56 mg, p=0.048. The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted. Interception storage capacity (Cmin was 0.19 and 0.54 mm for rainfall and fog respectively. T. recurvata contributed 20% to the rain interception of their shrub hosts: Acacia farnesiana and Prosopis laevigata. Meteorological data registered during one year at Cadereyta, México showed that radiative fog formation was possible during the dry season. The results showed the potential role of T. recurvata in capturing fog, which probably is a main source of water during the dry season that supports their reproductive and physiological activity at that time. The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be

  16. Fog interception by Ball moss (Tillandsia recurvata)

    Science.gov (United States)

    Guevara-Escobar, A.; Cervantes-Jiménez, M.; Suzán-Azpiri, H.; González-Sosa, E.; Hernández-Sandoval, L.; Malda-Barrera, G.; Martínez-Díaz, M.

    2010-03-01

    Interception losses are a major influence in the water yield of vegetated areas. For most storms, interception results in less water reaching the ground. However, fog drip or occult precipitation can result in negative interception because small drops are deposited on all plant surfaces and subsequently fall to the ground once vegetation storage capacities are exceeded. Fog drip is normally disregarded, but for some plant communities, it could be a mechanism offsetting evaporation losses. Tillandsia recurvata is a cosmopolitan epiphyte adapted to arid habitats where fog may be an important water source. Therefore, the interception storage capacity by T. recurvata was measured in controlled conditions through applying simulated rain or fog. The storage capacity was proportional to dry weight mass. Nocturnal stomatic opening in T. recurvata is not only relevant for CO2 but for water vapor, as suggested by the higher weight change of specimens wetted with fog for 1 h at dark in comparison to those wetted during daylight (543±77 vs. 325±56 mg, p=0.048). The coefficients obtained in the laboratory were used together with biomass measurements for T. recurvata in a xeric scrub to calculate the depth of water intercepted. Interception storage capacity (Cmin) was 0.19 and 0.54 mm for rainfall and fog respectively. T. recurvata contributed 20% to the rain interception of their shrub hosts: Acacia farnesiana and Prosopis laevigata. Meteorological data registered during one year at Cadereyta, México showed that radiative fog formation was possible during the dry season. The results showed the potential role of T. recurvata in capturing fog, which probably is a main source of water during the dry season that supports their reproductive and physiological activity at that time. The storage capacity of T. recurvata leaf surfaces could increase the amount of water available for evaporation, but as this species colonise montane forests, the effect could be negative on water

  17. Internet-Protocol-Based Satellite Bus Architecture Designed

    Science.gov (United States)

    Slywczak, Richard A.

    2004-01-01

    NASA is designing future complex satellite missions ranging from single satellites and constellations to space networks and sensor webs. These missions require more interoperability, autonomy, and coordination than previous missions; in addition, a desire exists to have scientists retrieve data directly from the satellite rather than a central distribution source. To meet these goals, NASA has been studying the possibility of extending the Transmission Control Protocol/Internet Protocol (TCP/IP) suite for spacebased applications.

  18. Satellite-based Flood Modeling Using TRMM-based Rainfall Products

    Directory of Open Access Journals (Sweden)

    Greg Easson

    2007-12-01

    Full Text Available Increasingly available and a virtually uninterrupted supply of satellite-estimatedrainfall data is gradually becoming a cost-effective source of input for flood predictionunder a variety of circumstances. However, most real-time and quasi-global satelliterainfall products are currently available at spatial scales ranging from 0.25o to 0.50o andhence, are considered somewhat coarse for dynamic hydrologic modeling of basin-scaleflood events. This study assesses the question: what are the hydrologic implications ofuncertainty of satellite rainfall data at the coarse scale? We investigated this question onthe 970 km2 Upper Cumberland river basin of Kentucky. The satellite rainfall productassessed was NASA’s Tropical Rainfall Measuring Mission (TRMM Multi-satellitePrecipitation Analysis (TMPA product called 3B41RT that is available in pseudo real timewith a latency of 6-10 hours. We observed that bias adjustment of satellite rainfall data canimprove application in flood prediction to some extent with the trade-off of more falsealarms in peak flow. However, a more rational and regime-based adjustment procedureneeds to be identified before the use of satellite data can be institutionalized among floodmodelers.

  19. Development of the one dimensional Fog Model PAFOG for operational Use at Munich Airport

    Science.gov (United States)

    Thoma, C.; Schneider, W.; Rohn, M.; Röhner, P.; Beckmann, B.-R.; Masbou, M.; Bott, A.

    2010-07-01

    Reduced visibility due to heavy fog is a hazard for land, sea, and air traffic. Especially for air transportation systems, reduced visibility leads to significant cost increments. Therefore, it is of particular importance to predict poor visibility fog events at airports accurately. In iPort-VIS, part of an aviation research program funded by the German Ministry for economy and technology, a site specific fog forecast system for Munich airport will be developed in cooperation between DWD, the German Aviation Control (DFS) and University of Bonn. The principal component of this forecast system is the one dimensional fog forecast model PAFOG (PArameterised FOG) that will be upgraded to operational use. The model consists of a parameterised microphysics scheme. The particle size distribution of cloud droplets is taken into account by a lognormal distribution and the visibility is calculated dependent on liquid water content and droplet concentration based on the Koschmieder formula. The turbulence in the atmospheric boundary layer is treated by the Mellor and Yamada closure scheme of order 2.5 in which a prognostic equation for the Turbulent Kinetic Energy (TKE) is solved. Radiative transports are considered by a Delta-Two-Stream Method with 18 spectral bands. Due to the fact that fog is a small scale complex phenomenon with high spatial and temporal variability, detailed knowledge of the atmospheric boundary layer structure is fundamental to get a realistic fog forecast. A time nudging scheme has been developed for integrating local observations (vertical profiles of temperature and specific humidity) periodically during the forecast. The system has been tested in several case studies with data from Lindenberg observatory and will be adapted to Munich airport with a new measurement system that will be installed by DWD. A second version of the nudging scheme, driven by the forecast of the high-resolution COSMO-DE model by DWD, is currently under development.

  20. Dsm Based Orientation of Large Stereo Satellite Image Blocks

    Science.gov (United States)

    d'Angelo, P.; Reinartz, P.

    2012-07-01

    High resolution stereo satellite imagery is well suited for the creation of digital surface models (DSM). A system for highly automated and operational DSM and orthoimage generation based on CARTOSAT-1 imagery is presented, with emphasis on fully automated georeferencing. The proposed system processes level-1 stereo scenes using the rational polynomial coefficients (RPC) universal sensor model. The RPC are derived from orbit and attitude information and have a much lower accuracy than the ground resolution of approximately 2.5 m. In order to use the images for orthorectification or DSM generation, an affine RPC correction is required. In this paper, GCP are automatically derived from lower resolution reference datasets (Landsat ETM+ Geocover and SRTM DSM). The traditional method of collecting the lateral position from a reference image and interpolating the corresponding height from the DEM ignores the higher lateral accuracy of the SRTM dataset. Our method avoids this drawback by using a RPC correction based on DSM alignment, resulting in improved geolocation of both DSM and ortho images. Scene based method and a bundle block adjustment based correction are developed and evaluated for a test site covering the nothern part of Italy, for which 405 Cartosat-1 Stereopairs are available. Both methods are tested against independent ground truth. Checks against this ground truth indicate a lateral error of 10 meters.

  1. 基于DSP的光纤惯性测试组件嵌入式数据采集系统%Embedded Data Acquisition System Design for Inertial Measurement Unit Consisted by FOG Based on DSP

    Institute of Scientific and Technical Information of China (English)

    樊勇华; 查峰; 李京书

    2012-01-01

    针对光纤测试组件信号输出特点,设计一种基于DSP的光纤惯性测试组件的数据采集系统,实现对光纤陀螺和加速度计输出信息、温度信息的A/D转换、采集、存储。针对光纤陀螺输出、温度以及加速度计输出等脉冲形式的信号,设计基于CPLD的脉冲信号计数电路,实现了固定时间间隔内的数据采样。针对加速度计温度输出为模拟信号的特点,基于24位的AD7738转换芯片通过DSP编程实现对加速度计温度信号AD转换和采集。设计了DSP与CPLD、上位机的外围通讯电路,通过对DSP内部存储器的编程,实现了对光纤惯性测试组件各信息的采集与测试,并将其发送给上位机进行存储、分析等处理。%To acquire the outputs of fiber optic gyros(FOG) and accelerometers and their temperature,a acquisition system is designed for the FOG inertial measurement unit(IMU) according to its data characteristic.A pulse-scaling circuit based on CPLD is designed to count the output pulses of the gyros and accelerometers,and consequently the outputs are sampled.Due to the temperature outputs of the accelerometers are analog signals,so the signals are converted to digital format using AD7738 chip and then they are acquired by DSP TMS320F28335.Finally,the communication circuit and DSP interactive program between the DSP,CPLD and test computer are designed and the data is acquired and sent to the test computer by the DSP.

  2. 基于小波变换的雾霾立体图像增强算法研究%Wavelet transform stereoscopic images enhancement algorithms based on fog and haze

    Institute of Scientific and Technical Information of China (English)

    邱奕敏; 周毅

    2015-01-01

    This paper proposes a new image enhancement algorithm based on edge sharpening of wavelet coefficients for fog and haze stereoscopic images, using multi-scale characteristic of wavelet transform in order to improve the clarity of fog and haze stereoscopic images, which is mainly used in moderate pollution. The algorithm combines the depth of stereo-scopic images with multi-scale wavelet decomposition, setting a control factor in the high-frequency sub-graph to regulate contrast enhancement. And it highlights the overall outline through the sharpening of the low-frequency sub-graph. Experi-mental results show that whether PSNR or visual effect, or the subjective assessment of the DMOS value, the proposed method has better enhanced performance than the conventional edge sharpening and wavelet transform. And it has good image edge enhancement, details protection. Meanwhile, the proposed algorithm has the same computational complexity with wavelet transform.%针对立体图像在雾霾环境下的质量问题,运用小波变换的多尺度特征,提出了一种雾霾环境下的立体图像增强算法,主要用于中度污染情况下的雾霾立体图像,以提高图像资源的清晰程度。该算法将原始雾霾立体图像的深度信息与多尺度小波分解相结合,在不同尺度下分解得到的小波高频子图中设置人为操控因子,调控对比度增强的强度;锐化分解后的小波低频子图边缘来突出整体轮廓。实验从PSNR指标、视觉效果和DMOS主观评价值三个方面验证了算法的成效,该方法的增强性能均好于传统的边缘锐化和四层小波变换方法,具备很好的图像边缘增强能力,细节保护能力,且与传统小波变换有相同的算法时间复杂度。

  3. Fog and Dew Collection Projects in Croatia

    CERN Document Server

    Mileta, M; Nikolayev, Vadim; Milimouk, I; Clus, O; Muselli, M

    2007-01-01

    The present paper discusses the fog and dew water collection in Croatia. Zavizan, the highest meteorological station in Croatia(1594m) is chosen for collecting of fog water with a standard fog collector (SFC). The highest daily collection rate was 27.8 L / m2. The highest daily collection rate in days without rain was 19.1 l/m2. Dew is also a noticeable source of water, especially during the drier summer season. Dew condensers in Croatia have been installed on the Adriatic coast (Zadar) and islands Vis and Bisevo. We report and discuss the data collected since 2003. In the small Bisevo island, a special roof has been designed to improve the formation and collection of dew on a house. Data from April 2005 will be presented and discussed.

  4. Mosquito flight failure in heavy fog

    Science.gov (United States)

    Dickerson, Andrew; Telljohann, Luke; Thornton, Lee-Ellen; Moyer, Caitlin; Hu, David

    2012-11-01

    Mosquitoes thrive during rainfall and high humidity. We previously found that mosquitoes are successful fliers through rainfall. Heavy fog, consisting of drops three orders of magnitude smaller in mass than raindrops, presents an environment in which mosquitoes cannot maintain flight. Through high-speed videography, we observe mosquitoes reduce wingbeat frequency in heavy fog, but retain the ability to generate sufficient force to lift their bodies, even after significant dew deposition. They are unable, however, to maintain an upright position required for sustainable flight. A mosquito's primary flight control mechanism is its halteres, small knobbed structures evolved from the hind wings, which flap anti-phase with the wings and provide gyroscopic feedback through Coriolis forces. Though the halteres are hydrophobic, repeated collisions with 10-micron fog particles hinders flight control, leading to flight failure.

  5. CONSIDERATIONS OF THE FOG REGIME IN THE AIRPORTS AREA FROM MOLDAVIA TERRITORY (ROMANIA

    Directory of Open Access Journals (Sweden)

    MACHIDON DANA

    2014-03-01

    Full Text Available In the airports area where the possibility of frequent mists and lasting fog exist, there is a risk that the aviation activity shut down for hours and sometimes for days. The paper is based primarily on the factual material represented by continually measured data during the 1961-2012 period by the weather stations witch are located in Iaşi, Bacău and Suceava airports area. Of all the airports located on the Moldova territory, the Iasi airport have lowest risk of occurrence of fog (33 days/year, and the opposite, with the highest number of days with fog, is Bacău airport (57 days/year. Annual average duration of fog case is between 5.4 hours at Iași and 8.3 hours at Suceava. In all that three airports, calculations based on long sequences of observations (1961 - 2012 have indicated that the annual number of days with fog presents a downward trend, more pronounced in Bacău and Suceava airports.

  6. Adjusting soil water balance calculations for light rainfall, dew, and fog.

    Science.gov (United States)

    Snyder, R. L.; Spano, D.; Moratiel, R.

    2012-04-01

    The main sources of water for an irrigated crop include irrigation applications, precipitation, water tables, fog interception, and dew formation. For a well-drained soil in a climate where there are a few events of fog, dew, or light rainfall, computing a water balance is relatively easy, but it is complicated in regions characterized by considerable events of fog, dew and light rainfall. In these regions, growers are hesitant to use ET-Based scheduling because the cumulative crop evapotranspiration is often considerably higher than the soil water depletion. We will present a simple and practical procedure to estimate the contribution of fog interception, dew, and light rainfall to daily crop evapotranspiration in California and to show how to use the information to improve water balance calculations for efficient water use in irrigation. It is assumed that the relationship between normalized hourly ETo and time of the day is similar to the relationship between normalized hourly ETc and time of the day. We can describe the change in soil water depletion (ΔDSW) on that day as: ΔDsw =ETc x F where F is the fraction of ETc coming from the soil, and F is determined using the expression: F = --1--- 1+ e(t-11.265.5) Where t is the approximate local standard time in hours when the crop dries. This simple method improves water balance scheduling and the adoption of the ET-based scheduling method in microclimates where fog, dew, and light rainfall are common.

  7. Three-Axis Satellite Attitude Control Based on Magnetic Torquing

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    1995-01-01

    Recently small satellite missions have gained considerable interest due to low-cost launch opportunities and technilogical improvement of micro-electronics.......Recently small satellite missions have gained considerable interest due to low-cost launch opportunities and technilogical improvement of micro-electronics....

  8. Three-Axis Satellite Attitude Control Based on Magnetic Torquing

    DEFF Research Database (Denmark)

    Wisniewski, Rafal

    1995-01-01

    Recently small satellite missions have gained considerable interest due to low-cost launch opportunities and technilogical improvement of micro-electronics.......Recently small satellite missions have gained considerable interest due to low-cost launch opportunities and technilogical improvement of micro-electronics....

  9. Fuel type characterization based on coarse resolution MODIS satellite data

    Directory of Open Access Journals (Sweden)

    Lanorte A

    2007-01-01

    Full Text Available Fuel types is one of the most important factors that should be taken into consideration for computing spatial fire hazard and risk and simulating fire growth and intensity across a landscape. In the present study, forest fuel mapping is considered from a remote sensing perspective. The purpose is to delineate forest types by exploring the use of coarse resolution satellite remote sensing MODIS imagery. In order to ascertain how well MODIS data can provide an exhaustive classification of fuel properties a sample area characterized by mixed vegetation covers and complex topography was analysed. The study area is located in the South of Italy. Fieldwork fuel type recognitions, performed before, after and during the acquisition of remote sensing MODIS data, were used as ground-truth dataset to assess the obtained results. The method comprised the following three steps: (I adaptation of Prometheus fuel types for obtaining a standardization system useful for remotely sensed classification of fuel types and properties in the considered Mediterranean ecosystems; (II model construction for the spectral characterization and mapping of fuel types based on two different approach, maximum likelihood (ML classification algorithm and spectral Mixture Analysis (MTMF; (III accuracy assessment for the performance evaluation based on the comparison of MODIS-based results with ground-truth. Results from our analyses showed that the use of remotely sensed MODIS data provided a valuable characterization and mapping of fuel types being that the achieved classification accuracy was higher than 73% for ML classifier and higher than 83% for MTMF.

  10. Evaluation of trace elements contamination in cloud/fog water at an elevated mountain site in Northern China.

    Science.gov (United States)

    Liu, Xiao-huan; Wai, Ka-ming; Wang, Yan; Zhou, Jie; Li, Peng-hui; Guo, Jia; Xu, Peng-ju; Wang, Wen-xing

    2012-07-01

    Totally 117 cloud/fog water samples were collected at the summit of Mt. Tai (1534m a.s.l.)-the highest mountain in the Northern China Plain. The results were investigated by a combination of techniques including back trajectory model, regional air quality and dust storm models, satellite observations and Principal Component Analysis. Elemental concentrations were determined by Inductively Coupled Plasma Mass Spectrometry, with stringent quality control measures. Higher elemental concentrations were found at Mt. Tai compared with those reported by other overseas studies. The larger proportions and higher concentrations of toxic elements such as Pb and As in cloud/fog water compared with those in rainwater at Mt. Tai suggests higher potential hazards of cloud/fog water as a source of contamination in polluted areas to the ecosystem. Peak concentrations of trace elements were frequently observed during the onset of cloud/fog events when liquid water contents of cloud/fog water were usually low and large amount of pollutants were accumulated in the ambient air. Inverse relationship between elemental concentrations and liquid water contents were only found in the samples with high electrical conductivities and liquid water contents lower than 0.3gm(-3). Affected mainly by the emissions of steel industries and mining activities, air masses transported from south/southwest of Mt. Tai were frequently associated with higher elemental concentrations. The element Mn is attributed to play an important role in the acidity of cloud/fog water. The composition of cloud/fog water influenced by an Asian dust storm event was reported, which was seldom found in the literature.

  11. A Hybrid Algorithm for Satellite Data Transmission Schedule Based on Genetic Algorithm

    Institute of Scientific and Technical Information of China (English)

    LI Yun-feng; WU Xiao-yue

    2008-01-01

    A hybrid scheduling algorithm based on genetic algorithm is proposed in this paper for reconnaissance satellite data transmission. At first, based on description of satellite data transmission request, satellite data transmission task modal and satellite data transmission scheduling problem model are established. Secondly, the conflicts in scheduling are discussed. According to the meaning of possible conflict, the method to divide possible conflict task set is given. Thirdly, a hybrid algorithm which consists of genetic algorithm and heuristic information is presented. The heuristic information comes from two concepts, conflict degree and conflict number. Finally, an example shows the algorithm's feasibility and performance better than other traditional algorithms.

  12. New dynamic routing algorithm based on MANET in LEO/MEO satellite network

    Institute of Scientific and Technical Information of China (English)

    LI Zhe; LI Dong-ni; WANG Guang-xing

    2006-01-01

    The features of low earth orbit/medium earth orbit (LEO/MEO) satellite networks routing algorithm based on inter-satellite link are analyzed and the similarities between satellite networks and mobile Ad Hoc network (MANET) are pointed out.The similar parts in MANET routing protocol are used in the satellite network for reference.A new dynamic routing algorithm based on MANET in LEO/MEO satellite networks,which fits for the LEO/MEO satellite communication system,is proposed.At the same time,the model of the algorithm is simulated and features are analyzed.It is shown that the algorithm has strong adaptability.It can give the network high autonomy,perfect function,low system overhead and great compatibility.

  13. A virtual maintenance-based approach for satellite assembling and troubleshooting assessment

    Science.gov (United States)

    Geng, Jie; Li, Ying; Wang, Ranran; Wang, Zili; Lv, Chuan; Zhou, Dong

    2017-09-01

    In this study, a Virtual Maintenance (VM)-based approach for satellite troubleshooting assessment is proposed. By focusing on various elements in satellite assemble troubleshooting, such as accessibility, ergonomics, wiring, and extent of damage, a systematic, quantitative, and objective assessment model is established to decrease subjectivity in satellite assembling and troubleshooting assessment. Afterwards, based on the established assessment model and satellite virtual prototype, an application process of this model suitable for a virtual environment is presented. Finally, according to the application process, all the elements in satellite troubleshooting are analyzed and assessed. The corresponding improvements, which realize the transformation from a conventional way to a virtual simulation and assessment, are suggested, and the flaws in assembling and troubleshooting are revealed. Assembling or troubleshooting schemes can be improved in the early stage of satellite design with the help of a virtual prototype. Repetition in the practical operation is beneficial to companies as risk and cost are effectively reduced.

  14. Fog as a Potential Indicator of a Local Water Source in Valles Marineris

    Science.gov (United States)

    Leung, Cecilia W. S.; Rafkin, Scot C. R.; McEwen, Alfred S.

    2016-10-01

    Images from Mars Express suggest that water ice fog may be present in Valles Marineris while absent from the surrounding plateau. Using a regional atmospheric model, we investigate planetary boundary layer processes and discuss the implications of these potential water ice fog. Results from our simulations show that the temperature inside Valles Marineris appears warmer relative to the plateaus outside at all times of day. From the modeled temperatures, we calculate saturation vapor pressures and saturation mixing to determine the amount of water vapor in the atmosphere for cloud formation. For a well-mixed atmosphere, saturated conditions in the canyon imply supersaturated conditions outside the canyon where it is colder. Consequently, low clouds should be everywhere. This is generally not the case. Based on potential fog observations inside the canyon, if we assume the plateau is just sub-saturated, and the canyon bottom is just saturated, the resulting difference in mixing ratios represents the minimum amount of vapor required for the atmosphere to be saturated, and for potential fog to form. Under these conditions, we determined that the air inside the canyon would require a 4-7 times enrichment in water vapor at saturation compared to outside the canyon. This suggests a local source of water vapor is required to explain water ice fog appearing within the confines of Valles Marineris on Mars.

  15. Channel modeling and performance evaluation of FSO communication systems in fog

    KAUST Repository

    Esmail, Maged Abdullah

    2016-07-01

    Free space optical (FSO) communication has become more exciting during the last decade. It has unregulated spectrum with a huge capacity compared to its radio frequency (RF) counterpart. Although FSO has many applications that cover indoor and outdoor environments, its widespread is humped by weather effects. Fog is classified as an extreme weather impairment that may cause link drop. Foggy channel modeling and characterization is necessary to analyze the system performance. In this paper, we first address the statistical behavior of the foggy channel based on a set of literature experimental data and develop a probability distribution function (PDF) model for fog attenuation. We then exploit our PDF model to derive closed form expressions and evaluate the system performance theoretically and numerically, in terms of average signal-to-noise ratio (SNR), and outage probability. The results show that for 10-3 outage probability and 22 dBm transmitted power, the FSO system can work over 80 m, 160 m, 310 m, and 460 m link length under dense, thick, moderate, and light fog respectively. Increasing the transmitted power will have high impact when the fog density is low. However, under very dense fog, it has almost no effect. © 2016 IEEE.

  16. Object Based and Pixel Based Classification Using Rapideye Satellite Imager of ETI-OSA, Lagos, Nigeria

    OpenAIRE

    Esther Oluwafunmilayo Makinde; Ayobami Taofeek Salami; James Bolarinwa Olaleye; Oluwapelumi Comfort Okewusi

    2016-01-01

    Several studies have been carried out to find an appropriate method to classify the remote sensing data. Traditional classification approaches are all pixel-based, and do not utilize the spatial information within an object which is an important source of information to image classification. Thus, this study compared the pixel based and object based classification algorithms using RapidEye satellite image of Eti-Osa LGA, Lagos. In the object-oriented approach, the image was segmented to homog...

  17. Spatiotemporal Variability of Surface Meteorological Variables During Fog and No-Fog Events in the Heber Valley, UT; Selected Case Studies From MATERHORN-Fog

    Science.gov (United States)

    van den Bossche, Michael; De Wekker, Stephan F. J.

    2016-09-01

    We investigated the spatiotemporal variability of surface meteorological variables in the nocturnal boundary layer using six automatic weather stations deployed in the Heber Valley, UT, during the MATERHORN-Fog experiment. The stations were installed on the valley floor within a 1.5 km × 0.8 km area and collected 1-Hz wind and pressure data and 0.2-Hz temperature and humidity data. We describe the weather stations and analyze the spatiotemporal variability of the measured variables during three nights with radiative cooling. Two nights were characterized by the presence of dense ice fog, one night with a persistent (`heavy') fog, and one with a short-lived (`moderate') fog, while the third night had no fog. Frost-point depressions were larger preceding the night without fog and showed a continued decrease during the no-fog night. On both fog nights, the frost-point depression reached values close to zero early in the night, but ~5 h earlier on the heavy-fog night than on the moderate-fog night. Spatial variability of temperature and humidity was smallest during the heavy-fog night and increased temporarily during short periods when wind speeds increased and the fog lifted. During all three nights, wind speeds did not exceed 2 m/s. The temporal variability of the wind speed and direction was larger during the fog nights than during the no-fog nights, but was particularly large during the heavy-fog night. The large variability corresponded with short-lived (5-10 min) pressure variations with amplitudes on the order of 0.5 hPa, indicating gravity wave activity. These pressure fluctuations occurred at all stations and were correlated in particular with variability in wind direction. Although not able to provide a complete picture of the nocturnal boundary layer, our low-cost weather stations were able to continuously collect data that were comparable to those of nearby research-grade instruments. From these data, we distinguished between fog and no-fog events

  18. A Collective Detection Based GPS Receiver for Small Satellites Project

    Data.gov (United States)

    National Aeronautics and Space Administration — To solve the problem of autonomous navigation on small satellite platforms less than 20 kg, we propose to develop an onboard orbit determination receiver for small...

  19. Urban-rural fog differences in Belgrade area, Serbia

    Science.gov (United States)

    Vujović, Dragana; Todorović, Nedeljko

    2016-12-01

    Urban/rural fog appearance during the last 27 years in the Belgrade region is analysed using hourly meteorological records from two meteorological stations: an urban station at Belgrade-Vračar (BV) and a rural station at Belgrade-Airport (BA). The effects of urban development on fog formation are discussed through analysis of fog frequency trends and comparison with a number of meteorological parameters. The mean annual and the mean annual minimum temperatures were greater at the urban BV station than at the rural BA station. The mean monthly relative humidity and the mean monthly water vapour pressure were greater at the rural than urban station. During the period of research (1988-2014), BA experiences 425 more days with fog than BV, which means that BV experiences fog for 62.68% of foggy days at BA. Trends in the number of days with fog were statistically non-significant. We analysed the fog occurrence during different types of weather. Fog in urban BV occurred more frequently during cyclonal circulation (in 52.75% of cases). In rural BA, the trend was the opposite and fog appeared more frequently during anticyclonic circulation (in 53.58% of cases). Fog at BV occurred most frequently in stable anticyclonic weather with light wind, when a temperature inversion existed (21.86% of cases). Most frequently, fog at BA occurred in the morning and only lasted a short time, followed by clearer skies during the anticyclonic warm and dry weather (22.55% of cases).

  20. Satellite Image Time Series Decomposition Based on EEMD

    Directory of Open Access Journals (Sweden)

    Yun-long Kong

    2015-11-01

    Full Text Available Satellite Image Time Series (SITS have recently been of great interest due to the emerging remote sensing capabilities for Earth observation. Trend and seasonal components are two crucial elements of SITS. In this paper, a novel framework of SITS decomposition based on Ensemble Empirical Mode Decomposition (EEMD is proposed. EEMD is achieved by sifting an ensemble of adaptive orthogonal components called Intrinsic Mode Functions (IMFs. EEMD is noise-assisted and overcomes the drawback of mode mixing in conventional Empirical Mode Decomposition (EMD. Inspired by these advantages, the aim of this work is to employ EEMD to decompose SITS into IMFs and to choose relevant IMFs for the separation of seasonal and trend components. In a series of simulations, IMFs extracted by EEMD achieved a clear representation with physical meaning. The experimental results of 16-day compositions of Moderate Resolution Imaging Spectroradiometer (MODIS, Normalized Difference Vegetation Index (NDVI, and Global Environment Monitoring Index (GEMI time series with disturbance illustrated the effectiveness and stability of the proposed approach to monitoring tasks, such as applications for the detection of abrupt changes.

  1. Satellite-Based Study of Glaciers Retreat in Northern Pakistan

    Science.gov (United States)

    Munir, Siraj

    Glaciers serve as a natural regulator of regional water supplies. About 16933 Km 2 area of glaciers is covered by Pakistan. These glaciers are enormous reservoirs of fresh water and their meltwater is an important resource which feed rivers in Pakistan. Glacier depletion, especially recent melting can affect agriculture, drinking water supplies, hydro-electric power, and ecological habitats. This can also have a more immediate impact on Pakistan's economy that depends mainly on water from glacier melt. Melting of seasonal snowfall and permanent glaciers has resulted not only in reduction of water resources but also caused flash floods in many areas of Pakistan. With the advent of satellite technology, using optical and SAR data the study of glaciers, has become possible. Using temporal data, based on calculation of snow index, band ratios and texture reflectance it has been revealed that the rate of glacier melting has increased as a consequent of global warming. Comparison of Landsat images of Batura glacier for October 1992 and October 2000 has revealed that there is a decrease of about 17 sq km in Batura glaciers. Although accurate changes in glacier extent cannot be assessed without baseline information, these efforts have been made to analyze future changes in glaciated area.

  2. Security in Fog Computing through Encryption

    Directory of Open Access Journals (Sweden)

    Akhilesh Vishwanath

    2016-05-01

    Full Text Available Cloud computing is considered as one of the most exciting technology because of its flexibility and scalability. The main problem that occurs in cloud is security. To overcome the problems or issues of security, a new technique called fog-computing is evolved. As there are security issues in fog even after getting the encrypted data from cloud, we implemented the process of encryption using AES algorithm to check how it works for the fog. So far, to our analysis AES algorithm is the most secured process of encryption for security. Three datasets of different types are considered and applied the analysed encryption technique over those datasets. On validation, entire data over datasets is being accurately encrypted and decrypted back as well. We took android mobile as an edge device and deployed the encryption over datasets into it. Further, performance of encryption is evaluated over selected datasets for accuracy if the entire data is correctly encrypted and decrypted along with the time, User load, Response time, Memory Utilization over file size. Further best and worst cases among the datasets are analysed thereby evaluating the suitability of AES in fog.

  3. Population-based geographic access to parent and satellite National Cancer Institute Cancer Center Facilities.

    Science.gov (United States)

    Onega, Tracy; Alford-Teaster, Jennifer; Wang, Fahui

    2017-09-01

    Satellite facilities of National Cancer Institute (NCI) cancer centers have expanded their regional footprints. This study characterized geographic access to parent and satellite NCI cancer center facilities nationally overall and by sociodemographics. Parent and satellite NCI cancer center facilities, which were geocoded in ArcGIS, were ascertained. Travel times from every census tract in the continental United States and Hawaii to the nearest parent and satellite facilities were calculated. Census-based population attributes were used to characterize measures of geographic access for sociodemographic groups. From the 62 NCI cancer centers providing clinical care in 2014, 76 unique parent locations and 211 satellite locations were mapped. The overall proportion of the population within 60 minutes of a facility was 22% for parent facilities and 32.7% for satellite facilities. When satellites were included for potential access, the proportion of some racial groups for which a satellite was the closest NCI cancer center facility increased notably (Native Americans, 22.6% with parent facilities and 39.7% with satellite facilities; whites, 34.8% with parent facilities and 50.3% with satellite facilities; and Asians, 40.0% with parent facilities and 54.0% with satellite facilities), with less marked increases for Hispanic and black populations. Rural populations of all categories had dramatically low proportions living within 60 minutes of an NCI cancer center facility of any type (1.0%-6.6%). Approximately 14% of the population (n = 43,033,310) lived more than 180 minutes from a parent or satellite facility, and most of these individuals were Native Americans and/or rural residents (37% of Native Americans and 41.7% of isolated rural residents). Racial/ethnic and rural populations showed markedly improved geographic access to NCI cancer center care when satellite facilities were included. Cancer 2017;123:3305-11. © 2017 American Cancer Society. © 2017 American

  4. Research and implementation of digital detection method on closed loop FOG

    Institute of Scientific and Technical Information of China (English)

    LI Di; LI Xu-you; SUN Yao

    2004-01-01

    In the strapdown inertial navigation system, the Fiber Optical Gyro(FOG) must have high precision to give accurate navigation information. In this paper, a digital closed loop detection method based on the ramp wave modulating technigue is introduced. DSP and FPGA have many advantages in digital signal processing. In the design, by using DSP, a complex arithmetic operation is completed to meet the needs of closed loop control of FOG within a short time. All kinds of control signals are produced easily by FPGA, under which DSP could work properly. Combining the DSP and FPGA, the detecting method is implemented successfully. In the end, the result of test and performance is given. From the result we can conclude that the precision of FOG is improved and the noises are limited to a low level.

  5. Experimental evaluation of fog warning system.

    Science.gov (United States)

    Al-Ghamdi, Ali S

    2007-11-01

    Highway safety is a major concern to the public and to transportation professionals, so the number of crashes caused by poor visibility due to fog form an alarming statistic. Drivers respond to poor visibility conditions in different ways: some slow down; others do not. Many drivers simply follow the taillights of the vehicle ahead. Accordingly, hazardous conditions are created in which speeds are both too high for the prevailing conditions and highly variable. Findings are presented from a study of traffic crashes due to fog in the southern region of Saudi Arabia. The primary objective was to assess the effectiveness of fog detection and warning system on driver behavior regarding speed and headway. This warning system includes visibility sensors that automatically activate a variable message sign that posts an advisory speed when hazardous conditions due to fog occur. The system was installed on a 2 km section of a two-lane, rural highway. A data set of 36,013 observations from both experimental and control sections at two study sites was collected and analyzed. The data included vehicle speed, volume, and classification; time headway, time of day, and visibility distance. Although the warning system was ineffective in reducing speed variability, mean speed throughout the experimental sections was reduced by about 6.5 kph. This reduction indicates that the warning system appeared to have a positive effect on driver behavior in fog even though the observed mean speeds were still higher than the posted advisory speed. From relationships found in the literature between mean driving speed and number of crashes, a speed reduction of only 5 kph would yield a 15% decrease in the number of crashes.

  6. Preliminary Analysis of a Novel SAR Based Emergency System for Earth Orbit Satellites using Galileo

    NARCIS (Netherlands)

    Gill, E.K.A.; Helderweirt, A.

    2010-01-01

    This paper presents a preliminary analysis of a novel Search and Rescue (SAR) based emergency system for Low Earth Orbit (LEO) satellites using the Galileo Global Navigation Satellite System (GNSS). It starts with a description of the space user SAR system including a concept description, mission ar

  7. Operational Testing of Satellite based Hydrological Model (SHM)

    Science.gov (United States)

    Gaur, Srishti; Paul, Pranesh Kumar; Singh, Rajendra; Mishra, Ashok; Gupta, Praveen Kumar; Singh, Raghavendra P.

    2017-04-01

    Incorporation of the concept of transposability in model testing is one of the prominent ways to check the credibility of a hydrological model. Successful testing ensures ability of hydrological models to deal with changing conditions, along with its extrapolation capacity. For a newly developed model, a number of contradictions arises regarding its applicability, therefore testing of credibility of model is essential to proficiently assess its strength and limitations. This concept emphasizes to perform 'Hierarchical Operational Testing' of Satellite based Hydrological Model (SHM), a newly developed surface water-groundwater coupled model, under PRACRITI-2 program initiated by Space Application Centre (SAC), Ahmedabad. SHM aims at sustainable water resources management using remote sensing data from Indian satellites. It consists of grid cells of 5km x 5km resolution and comprises of five modules namely: Surface Water (SW), Forest (F), Snow (S), Groundwater (GW) and Routing (ROU). SW module (functions in the grid cells with land cover other than forest and snow) deals with estimation of surface runoff, soil moisture and evapotranspiration by using NRCS-CN method, water balance and Hragreaves method, respectively. The hydrology of F module is dependent entirely on sub-surface processes and water balance is calculated based on it. GW module generates baseflow (depending on water table variation with the level of water in streams) using Boussinesq equation. ROU module is grounded on a cell-to-cell routing technique based on the principle of Time Variant Spatially Distributed Direct Runoff Hydrograph (SDDH) to route the generated runoff and baseflow by different modules up to the outlet. For this study Subarnarekha river basin, flood prone zone of eastern India, has been chosen for hierarchical operational testing scheme which includes tests under stationary as well as transitory conditions. For this the basin has been divided into three sub-basins using three flow

  8. Groundwater Modelling For Recharge Estimation Using Satellite Based Evapotranspiration

    Science.gov (United States)

    Soheili, Mahmoud; (Tom) Rientjes, T. H. M.; (Christiaan) van der Tol, C.

    2017-04-01

    Groundwater movement is influenced by several factors and processes in the hydrological cycle, from which, recharge is of high relevance. Since the amount of aquifer extractable water directly relates to the recharge amount, estimation of recharge is a perquisite of groundwater resources management. Recharge is highly affected by water loss mechanisms the major of which is actual evapotranspiration (ETa). It is, therefore, essential to have detailed assessment of ETa impact on groundwater recharge. The objective of this study was to evaluate how recharge was affected when satellite-based evapotranspiration was used instead of in-situ based ETa in the Salland area, the Netherlands. The Methodology for Interactive Planning for Water Management (MIPWA) model setup which includes a groundwater model for the northern part of the Netherlands was used for recharge estimation. The Surface Energy Balance Algorithm for Land (SEBAL) based actual evapotranspiration maps from Waterschap Groot Salland were also used. Comparison of SEBAL based ETa estimates with in-situ abased estimates in the Netherlands showed that these SEBAL estimates were not reliable. As such results could not serve for calibrating root zone parameters in the CAPSIM model. The annual cumulative ETa map produced by the model showed that the maximum amount of evapotranspiration occurs in mixed forest areas in the northeast and a portion of central parts. Estimates ranged from 579 mm to a minimum of 0 mm in the highest elevated areas with woody vegetation in the southeast of the region. Variations in mean seasonal hydraulic head and groundwater level for each layer showed that the hydraulic gradient follows elevation in the Salland area from southeast (maximum) to northwest (minimum) of the region which depicts the groundwater flow direction. The mean seasonal water balance in CAPSIM part was evaluated to represent recharge estimation in the first layer. The highest recharge estimated flux was for autumn

  9. Bionic development of textile materials for harvesting water from fog

    Science.gov (United States)

    Sarsour, J.; Stegmaier, Th.; Linke, M.; Planck, H.

    2010-07-01

    The supply of drinking water is one of the great challenges for mankind in the future. At present about one billion people have no access to clean drinking water. Particularly in developing countries the supply of potable water is often insufficient. A centralized water supply can often not be implemented because of technical and logistical problems. In certain remote areas, a connection to a public water supply net is economically or technically not feasible, e.g. in settlements on small islands, in isolated sea bays or in mountainous areas. Water supply represents a fundamental problem for terrestrial organisms. In fact, plants and animals of dry areas have developed various methods for obtaining water. The potential for a technical transfer of these natural solutions is far from being well evaluated. An example for obtaining water in arid environments is fog harvesting. Particularly in environments which receive extremely low rates of precipitation, organisms can be found which are capable of obtaining water from fog. The goal of this project is a detailed study of the underlying strategies and mechanisms and their application in technical devices for fog harvesting of drinking water. The project concentrates on the development of textile materials which are optimized for their use in large harvesting collector arrays that are able to supply multi-family houses and/or schools up to smaller villages with water. We expect that techniques can also be used in irrigation systems. The lecture presents the transfer strategy of biological strategies into textile-based devices and first successful field studies.

  10. Global Crop Monitoring: A Satellite-Based Hierarchical Approach

    Directory of Open Access Journals (Sweden)

    Bingfang Wu

    2015-04-01

    Full Text Available Taking advantage of multiple new remote sensing data sources, especially from Chinese satellites, the CropWatch system has expanded the scope of its international analyses through the development of new indicators and an upgraded operational methodology. The approach adopts a hierarchical system covering four spatial levels of detail: global, regional, national (thirty-one key countries including China and “sub-countries” (for the nine largest countries. The thirty-one countries encompass more that 80% of both production and exports of maize, rice, soybean and wheat. The methodology resorts to climatic and remote sensing indicators at different scales. The global patterns of crop environmental growing conditions are first analyzed with indicators for rainfall, temperature, photosynthetically active radiation (PAR as well as potential biomass. At the regional scale, the indicators pay more attention to crops and include Vegetation Health Index (VHI, Vegetation Condition Index (VCI, Cropped Arable Land Fraction (CALF as well as Cropping Intensity (CI. Together, they characterize crop situation, farming intensity and stress. CropWatch carries out detailed crop condition analyses at the national scale with a comprehensive array of variables and indicators. The Normalized Difference Vegetation Index (NDVI, cropped areas and crop conditions are integrated to derive food production estimates. For the nine largest countries, CropWatch zooms into the sub-national units to acquire detailed information on crop condition and production by including new indicators (e.g., Crop type proportion. Based on trend analysis, CropWatch also issues crop production supply outlooks, covering both long-term variations and short-term dynamic changes in key food exporters and importers. The hierarchical approach adopted by CropWatch is the basis of the analyses of climatic and crop conditions assessments published in the quarterly “CropWatch bulletin” which

  11. Introducing multisensor satellite radiance-based evaluation for regional Earth System modeling

    Science.gov (United States)

    Matsui, T.; Santanello, J.; Shi, J. J.; Tao, W.-K.; Wu, D.; Peters-Lidard, C.; Kemp, E.; Chin, M.; Starr, D.; Sekiguchi, M.; Aires, F.

    2014-07-01

    Earth System modeling has become more complex, and its evaluation using satellite data has also become more difficult due to model and data diversity. Therefore, the fundamental methodology of using satellite direct measurements with instrumental simulators should be addressed especially for modeling community members lacking a solid background of radiative transfer and scattering theory. This manuscript introduces principles of multisatellite, multisensor radiance-based evaluation methods for a fully coupled regional Earth System model: NASA-Unified Weather Research and Forecasting (NU-WRF) model. We use a NU-WRF case study simulation over West Africa as an example of evaluating aerosol-cloud-precipitation-land processes with various satellite observations. NU-WRF-simulated geophysical parameters are converted to the satellite-observable raw radiance and backscatter under nearly consistent physics assumptions via the multisensor satellite simulator, the Goddard Satellite Data Simulator Unit. We present varied examples of simple yet robust methods that characterize forecast errors and model physics biases through the spatial and statistical interpretation of various satellite raw signals: infrared brightness temperature (Tb) for surface skin temperature and cloud top temperature, microwave Tb for precipitation ice and surface flooding, and radar and lidar backscatter for aerosol-cloud profiling simultaneously. Because raw satellite signals integrate many sources of geophysical information, we demonstrate user-defined thresholds and a simple statistical process to facilitate evaluations, including the infrared-microwave-based cloud types and lidar/radar-based profile classifications.

  12. Introducing Multisensor Satellite Radiance-Based Evaluation for Regional Earth System Modeling

    Science.gov (United States)

    Matsui, T.; Santanello, J.; Shi, J. J.; Tao, W.-K.; Wu, D.; Peters-Lidard, C.; Kemp, E.; Chin, M.; Starr, D.; Sekiguchi, M.; hide

    2014-01-01

    Earth System modeling has become more complex, and its evaluation using satellite data has also become more difficult due to model and data diversity. Therefore, the fundamental methodology of using satellite direct measurements with instrumental simulators should be addressed especially for modeling community members lacking a solid background of radiative transfer and scattering theory. This manuscript introduces principles of multisatellite, multisensor radiance-based evaluation methods for a fully coupled regional Earth System model: NASA-Unified Weather Research and Forecasting (NU-WRF) model. We use a NU-WRF case study simulation over West Africa as an example of evaluating aerosol-cloud-precipitation-land processes with various satellite observations. NU-WRF-simulated geophysical parameters are converted to the satellite-observable raw radiance and backscatter under nearly consistent physics assumptions via the multisensor satellite simulator, the Goddard Satellite Data Simulator Unit. We present varied examples of simple yet robust methods that characterize forecast errors and model physics biases through the spatial and statistical interpretation of various satellite raw signals: infrared brightness temperature (Tb) for surface skin temperature and cloud top temperature, microwave Tb for precipitation ice and surface flooding, and radar and lidar backscatter for aerosol-cloud profiling simultaneously. Because raw satellite signals integrate many sources of geophysical information, we demonstrate user-defined thresholds and a simple statistical process to facilitate evaluations, including the infrared-microwave-based cloud types and lidar/radar-based profile classifications.

  13. Satellite link augmentation of ground based packet switched data networks

    Science.gov (United States)

    Farrell, J. B.; McLane, P. J.; Campbell, L. L.

    Use of satellite link augmentation to improve the performance of a packet switched data network is considered. Particular attention is paid to the analysis of two queues in series from the standpoint of time delay. A finite state machine model is used to aid the analysis. The results from the analysis are then used in a flow deviation routing algorithm. This algorithm is applied to study the performance improvement when satellite links are used to augment the Canadian DATAPAC network. The results are backed up by extensive simulations on a digital computer.

  14. Role of sea ice in air-sea exchange and its relation to sea fog

    Institute of Scientific and Technical Information of China (English)

    解思梅; 包澄澜; 姜德中; 邹斌

    2001-01-01

    Synchronous or quasi-synchronous stereoscopic sea-ice-air comprehensive observation was conducted during the First China Arctic Expedition in summer of 1999. Based on these data, the role of sea ice in sea-air exchange was studied. The study shows that the kinds, distribution and thickness of sea ice and their variation significantly influence the air-sea heat exchange. In floating ice area, the heat momentum transferred from ocean to atmosphere is in form of latent heat; latent heat flux is closely related to floating ice concentration; if floating ice is less, the heat flux would be larger. Latent heat flux is about 21 23.6 W*m-2, which is greater than sensible heat flux. On ice field or giant floating ice, heat momentum transferred from atmosphere to sea ice or snow surface is in form of sensible heat. In the floating ice area or polynya, sea-air exchange is the most active, and also the most sensible for climate. Also this area is the most important condition for the creation of Arctic vapor fog. The heat exchange of a large-scale vapor fog process of about 500000 km2 on Aug. 21 22,1999 was calculated; the heat momentum transferred from ocean to air was about 14.8×109 kW. There are various kinds of sea fog, radiation fog, vapor fog and advection fog, forming in the Arctic Ocean in summer. One important cause is the existence of sea ice and its resultant complexity of both underlying surface and sea-air exchange.

  15. Impact of Air Pollution on California Central Valley Fog Frequency

    Science.gov (United States)

    Gray, E.; Baldocchi, D. D.; Goldstein, A. H.

    2015-12-01

    Throughout the 20th century, trends in California Central Valley fog frequency have changed dramatically without explanation. While episodes of dense radiation fog, known regionally as Tule Fog, increased steadily from 1930-1970, analysis from both ground and remote sensing measurements confirm a 46-50% reduction in fog days in the last 30 years (Baldocchi and Waller, 2014, Herkes et al., 2014). The dominant hypotheses suggest that the recent decline in radiation fog can be explained by the rising temperatures associated with climate change or urban heat island effect. This assertion fails to explain the significant increase in Central Valley fog midcentury. Here we instead assert that changes in air pollution, rather than climate, better support this upward then downward temporal trend. Automobile use greatly increased emissions of nitrogen oxide (NOx) midcentury, followed by a large decrease in vehicle emissions due to statewide regulation from 1980 to present. In the Central Valley, NOx from automobile emissions contributes to the formation ammonium nitrate (NH4NO3), the dominant hygroscopic aerosol in the valley's wintertime boundary layer that can act as cloud condensation nuclei (CCN) necessary for fog droplet formation. Thus, changes in air pollution not only affect the number of CCN, but may also impact the density and persistence of fog episodes. Using NOAA meteorological records throughout the twentieth century, we will show the correlation between fog frequency, air pollution, and climatic drivers. We conclude that fog trends are closely correlated with changes in air pollution, rather than solely climate change.

  16. Evaluation of satellite-based precipitation estimates in winter season using an object-based approach

    Science.gov (United States)

    Li, J.; Hsu, K.; AghaKouchak, A.; Sorooshian, S.

    2012-12-01

    Verification has become an integral component of satellite precipitation algorithms and products. A number of object-based verification methods have been proposed to provide diagnostic information regarding the precipitation products' ability to capture the spatial pattern, intensity, and placement of precipitation. However, most object-based methods are not capable of investigating precipitation objects at the storm-scale. In this study, an image processing approach known as watershed segmentation was adopted to detect the storm-scale rainfall objects. Then, a fuzzy logic-based technique was utilized to diagnose and analyze storm-scale object attributes, including centroid distance, area ratio, intersection area ratio and orientation angle difference. Three verification metrics (i.e., false alarm ratio, missing ratio and overall membership score) were generated for validation and verification. Three satellite-based precipitation products, including PERSIANN, CMORPH, 3B42RT, were evaluated against NOAA stage IV MPE multi-sensor composite rain analysis at 0.25° by 0.25° on a daily scale in the winter season of 2010 over the contiguous United States. Winter season is dominated by frontal systems which usually have larger area coverage. All three products and the stage IV observation tend to find large size storm objects. With respect to the evaluation attributes, PERSIANN tends to obtain larger area ratio and consequently has larger centroid distance to the stage IV observations, while 3B42RT are found to be closer to the stage IV for the object size. All evaluation products give small orientation angle differences but vary significantly for the missing ratio and false alarm ratio. This implies that satellite estimates can fail to detect storms in winter. The overall membership scores are close for all three different products which indicate that all three satellite-based precipitation products perform well for capturing the spatial and geometric characteristics of

  17. Performance tests of a satellite-based asymmetric communication network for the 'hyper hospital'.

    Science.gov (United States)

    Yamaguchi, T

    1997-01-01

    The Hyper Hospital is a prototype networked telemedicine system which uses virtual reality. We measured the performance of a novel multimedia network based on satellite communications. The network was a hybrid system consisting of a satellite channel in one direction and a terrestrial channel in the other. Each user was equipped with a standard satellite communication receiver and a telephone connection. Requests from the users were sent by modern and telephone line and responses were received by satellite. The user requests were initiated by clicking buttons on a World Wide Web browser screen. The transmission rates of satellite and normal telephone-line communications were compared for standardized text data. Satellite communication was three to five times faster. The transmission rate was also measured for standardized graphical data (GIF format). With a file size of about 400 kByte, satellite-mediated communication was 10 times faster than telephone lines. The effect of simultaneous access on performance was also explored. For simultaneous access of nine users to a single graphics file, 78% of the transmission speed was obtained in comparison with that of a single user. The satellite-based system showed excellent high-speed communication performance, particularly for multimedia data.

  18. Recent Developments for Satellite-Based Fire Monitoring in Canada

    Science.gov (United States)

    Abuelgasim, A.; Fraser, R.

    2002-05-01

    Wildfires in Canadian forests are a major source of natural disturbance. These fires have a tremendous impact on the local environment, humans and wildlife, ecosystem function, weather, and climate. Approximately 9000 fires burn 3 million hectares per year in Canada (based on a 10-year average). While only 2 to 3 percent of these wildfires grow larger than 200 hectares in size, they account for almost 97 percent of the annual area burned. This provides an excellent opportunity to monitor active fires using a combination of low and high resolution sensors for the purpose of determining fire location and burned areas. Given the size of Canada, the use of remote sensing data is a cost-effective way to achieve a synoptic overview of large forest fire activity in near-real time. In 1998 the Canada Centre for Remote Sensing (CCRS) and the Canadian Forest Service (CFS) developed a system for Fire Monitoring, Mapping and Modelling (Fire M3;http://fms.nofc.cfs.nrcan.gc.ca/FireM3/). Fire M3 automatically identifies, monitors, and maps large forest fires on a daily basis using NOAA AVHRR data. These data are processed daily using the GEOCOMP-N satellite image processing system. This presentation will describe recent developments to Fire M3, included the addition of a set of algorithms tailored for NOAA-16 (N-16) data. The two fire detection algorithms are developed for N-16 day and night-time daily data collection. The algorithms exploit both the multi-spectral and thermal information from the AVHRR daily images. The set of N-16 day and night algorithms was used to generate daily active fire maps across North America for the 2001 fire season. Such a combined approach for fire detection leads to an improved detection rate, although day-time detection based on the new 1.6 um channel was much less effective (note - given the low detection rate with day time imagery, I don't think we can make the statement about capturing the diurnal cycle). Selected validation sites in western

  19. The potential of Tillandsia dune ecosystems for revealing past and present variations in advective fog along the coastal Atacama Desert, northern Chile

    Science.gov (United States)

    Latorre Hidalgo, C.; García, J. L.; Gonzalez, A. L.; Marquet, P. A.

    2015-12-01

    The coastal Atacama Desert is home to a complex geo-ecosystem supported by fog with multiple atmospheric and oceanic drivers. Fog collectors in place for the last 17 years reveal that monthly fog intensity and amount are significantly linked to the El Niño-Southern Oscillation (ENSO 1+2) with cold (warm) anomalies correlated to increased (decreased) fog (R2 = 0.41). Rainfall, however, can occur during extreme positive ENSO anomalies. Tillandsia landbeckii is an epiarenitic plant common to the coastal Atacama where fog is intercepted by the coastal escarpment between 950-1250 m.a.s.l. These plants possess multiple adaptations to survive exclusively on fog, including the construction of "dune" ecosystems known as "tillandsiales". Buried T. landbeckii layers in such dunes contain a record of past variations of fog over time (dunes can top 3 m in height) and alternating plant and sand layers are readily visible in dune stratigraphy. Stable N isotopes on modern plants and fog indicate that these plants reflect δ15N values of total N dissolved in fog. We measured δ15N values from buried T. landbeckii layers from five different tillandsiales found across c. 50 km the coastal escarpment. The isotope values in these buried plants indicate a prominent c. 8.0 ‰ shift towards more negative δ15N values on average over the last 3,200 years. Based on differences in δ15N between modern and more extensive "paleo" tillandsiales at one of our lowest elevation study sites, we interpret this shift as an increase in available moisture due to increased fog input during the late Holocene. Increased variability in ENSO as well as increased upwelling and southerly winds along the coastal Atacama would explain in part this increase. Clearly, the Atacama tillandsiales have considerable potential for monitoring past and present change of these large-scale ocean-atmosphere systems.

  20. 基于区域生长的翡翠云雾纹理分割方法%Method of EmeraId CIoud and Fog Texture Segmentation Based on Region Growing

    Institute of Scientific and Technical Information of China (English)

    姚建龙; 陈建勋

    2014-01-01

    this paper proposed a method of emeraId coud and fog texture segmentation based on region growing.First,convert the image to YCrCb coIor space, according to the statistics of the EmeraId CbCr component range,using the boundary tracking aIgorithm to determine the anaIysis area.Then FCM cIustering performed for CbCr components,so seed growing areas are seIected.Next,make the seeds growing for the regionaI characteristics of simiIar coIor and texture simiIar,and using the anaIysis GLCM texture feature of Y component extract factors for segmentation,and then merging simiIar region.%根据翡翠云雾纹理特征,提出基于区域生长算法的翡翠纹理分割方法。首先,将图像转换到 YCbCr 颜色空间,根据统计的翡翠 CbCr 分量范围,利用边界跟踪算法确定分析区域,然后针对 CbCr 分量进行 FCM 聚类,选定生长区域种子,根据生长区域颜色相近和纹理相似的特征,进行区域生长,利用灰度共生矩阵分析 Y 分量进行纹理特征提取,针对分割效果影响因素,进行区域合并。实验表明该方法的分割效果良好。

  1. GPS/Magnetometer Based Satellite Navigation and Attitude Determination

    Science.gov (United States)

    Deutschmann, Julie; Bar-Itzhack, Itzhack; Harman, Rick; Bauer, Frank H. (Technical Monitor)

    2001-01-01

    In recent years algorithms were developed for orbit, attitude and angular-rate determination of Low Earth Orbiting (LEO) satellites. Those algorithms rely on measurements of magnetometers, which are standard, relatively inexpensive, sensors that are normally installed on every LEO satellite. Although magnetometers alone are sufficient for obtaining the desired information, the convergence of the algorithms to the correct values of the satellite orbital parameters, position, attitude and angular velocity is very slow. The addition of sun sensors reduces the convergence time considerably. However, for many LEO satellites the sun data is not available during portions of the orbit when the spacecraft (SC) is in the earth shadow. It is here where the GPS space vehicles (SV) can provide valuable support. This is clearly demonstrated in the present paper. Although GPS measurements alone can be used to obtain SC position, velocity, attitude and angular-rate, the use of magnetometers improve the results due to the synergistic effect of sensor fusion. Moreover, it is possible to obtain these results with less than three SVs. In this paper we introduce an estimation algorithm, which is a combination of an Extended Kalman Filter (EKF) and a Pseudo Linear Kalman Filter (PSELIKA).

  2. A Constraint Based Approach for Building Operationally Responsive Satellites

    Science.gov (United States)

    2008-09-01

    discipline specific software codes into a common environment. LLB team also uses MATLAB R© to integrate CAD tools such as Catia , Pro/Engineer with FE...satellite configuration through a Catia CAD tool. The LLB approach is similar to the approach discussed in this research because it provides a method

  3. The ESRC: A Web-based Environmental Satellite Resource Center

    Science.gov (United States)

    Abshire, W. E.; Guarente, B.; Dills, P. N.

    2009-12-01

    The COMET® Program has developed an Environmental Satellite Resource Center (known as the ESRC), a searchable, database-driven Website that provides easy access to a wide range of useful information training materials on polar-orbiting and geostationary satellites. Primarily sponsored by the NPOESS Program and NOAA, the ESRC is a tool for users seeking reliable sources of satellite information, training, and data. First published in September 2008, and upgraded in April 2009, the site is freely available at: http://www.meted.ucar.edu/esrc. Additional contributions to the ESRC are sought and made on an ongoing basis. The ESRC was created in response to a broad community request first made in May 2006. The COMET Program was asked to develop the site to consolidate and simplify access to reliable, current, and diverse information, training materials, and data associated with environmental satellites. The ESRC currently includes over 400 significant resources from NRL, CIMSS, CIRA, NASA, VISIT, NESDIS, and EUMETSAT, and improves access to the numerous satellite resources available from COMET’s MetEd Website. The ESRC is designed as a community site where organizations and individuals around the globe can easily submit their resources via online forms by providing a small set of metadata. The ESRC supports languages other than English and multi-lingual character sets have been tested. COMET’s role is threefold: 1) maintain the site, 2) populate it with our own materials, including smaller, focused learning objects derived from our larger training modules, and 3) provide the necessary quality assurance and monitoring to ensure that all resources are appropriate and well described before being made available. Our presentation will demonstrate many of the features and functionality of searching for resources using the ESRC, and will outline the steps for users to make their own submissions. For the site to reach its full potential, submissions representing diverse

  4. Robot Vision to Monitor Structures in Invisible Fog Environments Using Active Imaging Technology

    Energy Technology Data Exchange (ETDEWEB)

    Park, Seungkyu; Park, Nakkyu; Baik, Sunghoon; Choi, Youngsoo; Jeong, Kyungmin [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    Active vision is a direct visualization technique using a highly sensitive image sensor and a high intensity illuminant. Range-gated imaging (RGI) technique providing 2D and 3D images is one of emerging active vision technologies. The RGI technique extracts vision information by summing time sliced vision images. In the RGI system, objects are illuminated for ultra-short time by a high intensity illuminant and then the light reflected from objects is captured by a highly sensitive image sensor with the exposure of ultra-short time. The RGI system provides 2D and 3D image data from several images and it moreover provides clear images from invisible fog and smoke environment by using summing of time-sliced images. Nowadays, the Range-gated (RG) imaging is an emerging technology in the field of surveillance for security applications, especially in the visualization of invisible night and fog environment. Although RGI viewing was discovered in the 1960's, this technology is, nowadays, more and more applicable by virtue of the rapid development of optical and sensor technologies, such as highly sensitive imaging sensor and ultra-short pulse laser light. In contrast to passive vision systems, this technology enables operation even in harsh environments like fog and smoke. During the past decades, several applications of this technology have been applied in target recognition and in harsh environments, such as fog, underwater vision. Also, this technology has been demonstrated 3D imaging based on range-gated imaging. In this paper, a robot system to monitor structures in invisible fog environment is developed using an active range-gated imaging technique. The system consists of an ultra-short pulse laser device and a highly sensitive imaging sensor. The developed vision system is carried out to monitor objects in invisible fog environment. The experimental result of this newly approach vision system is described in this paper. To see invisible objects in fog

  5. Spline model of the high latitude scintillation based on in situ satellite data

    Science.gov (United States)

    Priyadarshi, S.; Wernik, A. W.

    2013-12-01

    We present a spline model for the high latitude ionospheric scintillation using satellite in situ measurements made by the Dynamic Explorer 2 (DE 2) satellite. DE 2 satellite measurements give observations only along satellite orbit but our interpolation model fills the gaps between the satellite orbits. This analytical model is based on products of cubic B-splines and coefficients determined by least squares fit to the binned data and constrained to make the fit periodic in 24 hours of geomagnetic local time, periodic in 360 degrees of invariant longitude, in geomagnetic indices and solar radio flux. Discussion of our results clearly shows the seasonal and diurnal behavior of ionospheric parameters important in scintillation modeling for different geophysical and solar activity conditions. We also show that results obtained from our analytical model match observations obtained from in situ measurements. Shishir Priyadarshi Space Research Centre, Poland

  6. An Image-Based Sensor System for Autonomous Rendez-Vous with Uncooperative Satellites

    CERN Document Server

    Miravet, Carlos; Krouch, Eloise; del Cura, Juan Manuel

    2008-01-01

    In this paper are described the image processing algorithms developed by SENER, Ingenieria y Sistemas to cope with the problem of image-based, autonomous rendez-vous (RV) with an orbiting satellite. The methods developed have a direct application in the OLEV (Orbital Life Extension Extension Vehicle) mission. OLEV is a commercial mission under development by a consortium formed by Swedish Space Corporation, Kayser-Threde and SENER, aimed to extend the operational life of geostationary telecommunication satellites by supplying them control, navigation and guidance services. OLEV is planned to use a set of cameras to determine the angular position and distance to the client satellite during the complete phases of rendez-vous and docking, thus enabling the operation with satellites not equipped with any specific navigational aid to provide support during the approach. The ability to operate with un-equipped client satellites significantly expands the range of applicability of the system under development, compar...

  7. Fog chemistry in the Texas-Louisiana Gulf Coast corridor

    Science.gov (United States)

    Raja, Suresh; Raghunathan, Ravikrishna; Yu, Xiao-Ying; Lee, Taehyoung; Chen, Jing; Kommalapati, Raghava R.; Murugesan, Karthik; Shen, Xinhua; Qingzhong, Yuan; Valsaraj, Kalliat T.; Collett, Jeffrey L.

    Fog samples were collected in two population centers of the US Gulf Coast (Houston, Texas and Baton Rouge, Louisiana) using Caltech active strand cloud collectors. A total of 32 fogwater samples were collected in Baton Rouge (November 2004-February 2005) and Houston (February 2006). These samples were analyzed for pH, total and dissolved organic carbon, major inorganic ions, and a variety of organic compounds including organic acids, aromatics, carbonyls, and linear alkanes. Fogs in both environments were of moderate density, with typical fog liquid water contents clouds in the eastern US. Total organic carbon concentrations were much higher in Houston fogs than in Baton Rouge fogs. Efforts to speciate dissolved organic carbon (DOC) reveal large contributions from organic acids and carbonyls, with smaller contributions from other organic compound families including aromatics, alkanes, amides, and alcohols. Approximately 40% of the fog DOC was unspeciated in samples from both study locations.

  8. A Satellite Based Method for Wetland Inundation Mapping

    Science.gov (United States)

    Di Vittorio, C.; Georgakakos, A. P.

    2016-12-01

    Hydrologic models of wetlands enable hydrologists and water resources managers to appreciate the environmental and societal roles of wetlands and manage them in ways that preserve their integrity and sustain their valuable services. However, wetland model reliability and accuracy are often unsatisfactory due to the complexity of the underlying processes and the lack of adequate in-situ data. In this research, we demonstrate how MODIS satellite imagery can be used to characterize wetland flooding over time and to support the development of more reliable wetland models. We apply this method to the Sudd, a seasonal wetland in South Sudan that is part of the Nile River Basin. The database consists of 16 years of 8-day composite ground surface reflectance data with a 500 m spatial resolution downloaded from Earth Explorer. After masking poor quality pixels, monthly mean NDWI and NDVI values were extracted. Based on literature and personal accounts describing the Sudd as well as Google Earth imagery, a set of ground truth locations were identified for each land class and monthly distributions of the indices were derived. The indices were then combined in a unique way and statistics of the new distributions were used to classify land types present in the full area of interest. Subsequently, annual statistics were derived from the same indices and used to identify pixels that undergo flooding as well as the timing and duration of flooding for each year (2000-2015). An independent set of ground truth locations were selected for method validation. The combined indices demonstrate high land classification accuracy and outperform the individual indices as well as other existing land classification algorithms. The derived monthly inundation series agrees well with literature and anecdotal observations. This information is currently being used to develop wetland models as part of a comprehensive modeling system for the Nile River Basin. The new method is general and can be used

  9. Monitoring Snow Using Geostationary Satellite Retrievals During the SAAWSO Project

    Science.gov (United States)

    Rabin, Robert M.; Gultepe, Ismail; Kuligowski, Robert J.; Heidinger, Andrew K.

    2016-09-01

    The SAAWSO (Satellite Applications for Arctic Weather and SAR (Search And Rescue) Operations) field programs were conducted by Environment Canada near St. Johns, NL and Goose Bay, NL in the winters of 2012-13 and 2013-14, respectively. The goals of these programs were to validate satellite-based nowcasting products, including snow amount, wind intensity, and cloud physical parameters (e.g., cloud cover), over northern latitudes with potential applications to Search And Rescue (SAR) operations. Ground-based in situ sensors and remote sensing platforms were used to measure microphysical properties of precipitation, clouds and fog, radiation, temperature, moisture and wind profiles. Multi-spectral infrared observations obtained from Geostationary Operational Environmental Satellite (GOES)-13 provided estimates of cloud top temperature and height, phase (water, ice), hydrometer size, extinction, optical depth, and horizontal wind patterns at 15 min intervals. In this work, a technique developed for identifying clouds capable of producing high snowfall rates and incorporating wind information from the satellite observations is described. The cloud top physical properties retrieved from operational satellite observations are validated using measurements obtained from the ground-based in situ and remote sensing platforms collected during two precipitation events: a blizzard heavy snow storm case and a moderate snow event. The retrieved snow precipitation rates are found to be comparable to those of ground-based platform measurements in the heavy snow event.

  10. Cost Analysis of Algorithm Based Billboard Manger Based Handover Method in LEO satellite Networks

    Directory of Open Access Journals (Sweden)

    Suman Kumar Sikdar

    2012-12-01

    Full Text Available Now-a-days LEO satellites have an important role in global communication system. They have some advantages like low power requirement and low end-to-end delay, more efficient frequency spectrum utilization between satellites and spot beams over GEO and MEO. So in future they can be used as a replacement of modern terrestrial wireless networks. But the handover occurrence is more due to the speed of the LEOs. Different protocol has been proposed for a successful handover among which BMBHO is more efficient. But it had a problem during the selection of the mobile node during handover. In our previous work we have proposed an algorithm so that the connection can be established easily with the appropriate satellite. In this paper we will evaluate the mobility management cost of Algorithm based Billboard Manager Based Handover method (BMBHO. A simulation result shows that the cost is lower than the cost of Mobile IP of SeaHO-LEO and PatHOLEO

  11. Simultaneous ground- and satellite-based observation of MF/HF auroral radio emissions

    Science.gov (United States)

    Sato, Yuka; Kumamoto, Atsushi; Katoh, Yuto; Shinbori, Atsuki; Kadokura, Akira; Ogawa, Yasunobu

    2016-05-01

    We report on the first simultaneous measurements of medium-high frequency (MF/HF) auroral radio emissions (above 1 MHz) by ground- and satellite-based instruments. Observational data were obtained by the ground-based passive receivers in Iceland and Svalbard, and by the Plasma Waves and Sounder experiment (PWS) mounted on the Akebono satellite. We observed two simultaneous appearance events, during which the frequencies of the auroral roar and MF bursts detected at ground level were different from those of the terrestrial hectometric radiation (THR) observed by the Akebono satellite passing over the ground-based stations. This frequency difference confirms that auroral roar and THR are generated at different altitudes across the F peak. We did not observe any simultaneous observations that indicated an identical generation region of auroral roar and THR. In most cases, MF/HF auroral radio emissions were observed only by the ground-based detector, or by the satellite-based detector, even when the satellite was passing directly over the ground-based stations. A higher detection rate was observed from space than from ground level. This can primarily be explained in terms of the idea that the Akebono satellite can detect THR emissions coming from a wider region, and because a considerable portion of auroral radio emissions generated in the bottomside F region are masked by ionospheric absorption and screening in the D/E regions associated with ionization which results from auroral electrons and solar UV radiation.

  12. Research on Coal Exploration Technology Based on Satellite Remote Sensing

    Directory of Open Access Journals (Sweden)

    Dong Xiao

    2016-01-01

    Full Text Available Coal is the main source of energy. In China and Vietnam, coal resources are very rich, but the exploration level is relatively low. This is mainly caused by the complicated geological structure, the low efficiency, the related damage, and other bad situations. To this end, we need to make use of some advanced technologies to guarantee the resource exploration is implemented smoothly and orderly. Numerous studies show that remote sensing technology is an effective way in coal exploration and measurement. In this paper, we try to measure the distribution and reserves of open-air coal area through satellite imagery. The satellite picture of open-air coal mining region in Quang Ninh Province of Vietnam was collected as the experimental data. Firstly, the ENVI software is used to eliminate satellite imagery spectral interference. Then, the image classification model is established by the improved ELM algorithm. Finally, the effectiveness of the improved ELM algorithm is verified by using MATLAB simulations. The results show that the accuracies of the testing set reach 96.5%. And it reaches 83% of the image discernment precision compared with the same image from Google.

  13. A Novel Method for Optimum Global Positioning System Satellite Selection Based on a Modified Genetic Algorithm.

    Science.gov (United States)

    Song, Jiancai; Xue, Guixiang; Kang, Yanan

    2016-01-01

    In this paper, a novel method for selecting a navigation satellite subset for a global positioning system (GPS) based on a genetic algorithm is presented. This approach is based on minimizing the factors in the geometric dilution of precision (GDOP) using a modified genetic algorithm (MGA) with an elite conservation strategy, adaptive selection, adaptive mutation, and a hybrid genetic algorithm that can select a subset of the satellites represented by specific numbers in the interval (4 ∼ n) while maintaining position accuracy. A comprehensive simulation demonstrates that the MGA-based satellite selection method effectively selects the correct number of optimal satellite subsets using receiver autonomous integrity monitoring (RAIM) or fault detection and exclusion (FDE). This method is more adaptable and flexible for GPS receivers, particularly for those used in handset equipment and mobile phones.

  14. A Novel Onboard-gateway-based Mechanism to Improve TCP Performance in Aeronautical Satellite Networks

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The IP-based networks on aircraft serve to support Internet services via satellites. However, in aeronautical satellite hybrid networks, the TCP protocol performance often deteriorates due to improper decreases and slow recovery of the congestion window. This paper proposes a window size determination and notification mechanism, onboard-gateway-based mechanism (OGBM), which is based on the onboard gateway in the networks on aircraft. A cross-layer approach is adopted by the onboard gateway to obtain the satellite link bandwidth information. And then, by the gateway, through changing the receiver's advertised window field in ACK packets, TCP sources are notified of the window size of each TCP source calculated on the ground of bandwidth delay product and flow numbers. The mechanism is able to avoid improper changes of TCP window and serve multiple users. Simulation results show that the mechanism with the fairness index close to 1 improves TCP performance in aeronautical satellite networks.

  15. On the Influence of a Simple Microphysics Parametrization on Radiation Fog Modelling: A Case Study During ParisFog

    Science.gov (United States)

    Zhang, Xiaojing; Musson-Genon, Luc; Dupont, Eric; Milliez, Maya; Carissimo, Bertrand

    2014-05-01

    A detailed numerical simulation of a radiation fog event with a single column model is presented, which takes into account recent developments in microphysical parametrizations. One-dimensional simulations are performed using the computational fluid dynamics model Code_Saturne and the results are compared to a very detailed in situ dataset collected during the ParisFog campaign, which took place near Paris, France, during the winter 2006-2007. Special attention is given to the detailed and complete diurnal simulations and to the role of microphysics in the fog life cycle. The comparison between the simulated and the observed visibility, in the single-column model case study, shows that the evolution of radiation fog is correctly simulated. Sensitivity simulations show that fog development and dissipation are sensitive to the droplet-size distribution through sedimentation/deposition processes but the aerosol number concentration in the coarse mode has a low impact on the time of fog formation.

  16. GOES-derived fog and low cloud indices for coastal north and central California ecological analyses

    Science.gov (United States)

    Torregrosa, Alicia; Combs, Cindy; Peters, Jeff

    2016-02-01

    Fog and low cloud cover (FLCC) strongly influences the water, energy, and nutrient flux of coastal ecosystems. Easy-to-use FLCC data are needed to quantify the impacts of FLCC on ecosystem dynamics especially during hot and dry Mediterranean climate summers. Monthly, annual, and decadal FLCC digital maps (indices) were derived for June-September 1999-2009 for coastal California, latitude 34.50°N (south of Monterey Bay) to latitude 41.95°N (north of Crescent City) from 26,000 hourly night and day Geostationary Operational Environmental Satellite (GOES) images. Monthly average FLCC ranges from winds and is lowest in the lee of major capes. FLCC advects farthest inland through low-lying NW ocean-facing valleys. At night, average total hours of FLCC are higher more frequently on land than over the ocean. The interannual FLCC coefficient of variation shows long-term geographic stability that is strongly associated with landform position. FLCC hours per day mapped contours, derived from decadal average FLCC, delineate the commonly used term "fog belt" into FLCC zones with increased locational precision. FLCC indices are available for download from the California Landscape Conservation Cooperative Climate Commons website (http://climate.calcommons.org/datasets/summertime-fog). FLCC indices can improve analyses of biogeographic and bioclimatic species distribution models; understanding meteorological mechanisms driving FLCC patterns; solar energy feasibility studies; investigations of ecohydrology, evapotranspiration, and agricultural irrigation demand; and viticulture ripening models.

  17. Simulating Atmospheric Free-Space Optical Propagation; Part II: Haze, Fog, and Low Clouds Attenuations

    Science.gov (United States)

    Achour, Maha

    2002-12-01

    One of the biggest challenges facing Free-Space Optics deployment is proper understanding of optical signal propagation in different atmospheric conditions. In an earlier study by the author (30), attenuation by rain was analyzed and successfully modeled for infrared signal transmission. In this paper, we focus on attenuation due to scattering by haze, fog and low clouds droplets using the original Mie Scattering theory. Relying on published experimental results on infrared propagation, electromagnetic waves scattering by spherical droplet, atmospheric physics and thermodynamics, UlmTech developed a computer-based platform, Simulight, which simulates infrared signal (750 nm-12 μm) propagation in haze, fog, low clouds, rain and clear weather. Optical signals are scattered by fog droplets during transmission in the forward direction preventing the receiver from detecting the minimum required power. Weather databases describe foggy conditions by measuring the visibility parameter, which is, in general, defined as the maximum distance that the visible 550 nm signal can travel while distinguishing between the target object and its background at 2% contrast. Extrapolating optical signal attenuations beyond 550 nm using only visibility is not as straightforward as stated by the Kruse equation which is unfortunately widely used. We conclude that it is essential to understand atmospheric droplet sizes and their distributions based on measured attenuations to effectively estimate infrared attenuation. We focus on three types of popular fogs: Evolving, Stable and Selective.

  18. A comparing design of satellite attitude control system based on reaction wheel

    Institute of Scientific and Technical Information of China (English)

    CHENG Hao; GE Sheng-min; SHEN Yi

    2008-01-01

    The disturbance caused by the reaction wheel with a current controller greatly influences the accuracy and stability of the satellite attitude control system.To solve this problem,the idea of speed feedback compensation control reaction wheel is put forward.This paper introduces the comparison on design and performance of two satellite attitude control systems,which are separately based on the current control reaction wheel and the speed feedback compensation control reaction wheel.Analysis shows that the speed feedback compensation control flywheel system may effectively suppress the torque fluctuation.Simulation results indicate that the satellite attitude control system with the speed feedback compensation control flywheel has improved performance.

  19. A DISTRIBUTED QOS ROUTING BASED ON ANT ALGORITHM FOR LEO SATELLITE NETWORK

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Low Earth Orbit (LEO) satellites provide short round-trip delays and are becoming increasingly important. One of the challenges in LEO satellite networks is the development of specialized and efficient routing algorithms. To satisfy the QoS requirements of multimedia applications, satellite routing protocols should consider handovers and minimize their effect on the active connections. A distributed QoS routing scheme based on heuristic ant algorithm is proposed for satisfying delay bound and avoiding link congestion. Simulation results show that the call blocking probabilities of this algorithm are less than that of Shortest Path First (SPF) with different delay bound.

  20. Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign

    Directory of Open Access Journals (Sweden)

    E. Hammer

    2014-04-01

    Full Text Available Fog causes a variety of hazards in road traffic, maritime navigation, as well as in air traffic and railway traffic. There is a great demand, e.g. from airports, for more reliable fog forecasts to prevent fog related accidents. Improved fog forecasts require a better understanding of the numerous complex mechanisms during the fog life cycle. During winter 2012/13 a field campaign called ParisFog aiming at fog research took place at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research. SIRTA is located about 20 km southwest of the Paris city centre, France in a semi-urban environment. In situ activation properties of the prevailing fog were investigated by measuring: (1 total and interstitial (non-activated dry particle number size distributions behind two different inlet systems; (2 interstitial hydrated aerosol and fog droplet size distributions at ambient conditions; (3 cloud condensation nuclei (CCN number concentration at different supersaturations (SS with a CCN counter. The aerosol particles were characterized regarding their hygroscopic properties, fog droplet activation behavior and contribution to light scattering for 17 developed fog events. Low particle hygroscopicity with an overall median of hygroscopicity parameter, κ, of 0.14 was found, likely caused by substantial influence from local traffic and wood burning emissions. Measurements of the aerosol size distribution at ambient RH revealed that the critical wet diameter, above which the hydrated aerosols activate to fog droplets, is rather large with a median value of 2.4 μm and is highly variable (ranging from 1 to 5 μm between the different fog events. Thus, the number of activated fog droplets was very small and the non-activated hydrated particles were found to contribute siginificantly to the observed light scattering and thus to the reduction in visibility. Combining all experimental data, the effective peak supersaturation, SSpeak, a measure of the peak

  1. Size-dependent particle activation properties in fog during the ParisFog 2012/13 field campaign

    Science.gov (United States)

    Hammer, E.; Gysel, M.; Roberts, G. C.; Elias, T.; Hofer, J.; Hoyle, C. R.; Bukowiecki, N.; Dupont, J.-C.; Burnet, F.; Baltensperger, U.; Weingartner, E.

    2014-04-01

    Fog causes a variety of hazards in road traffic, maritime navigation, as well as in air traffic and railway traffic. There is a great demand, e.g. from airports, for more reliable fog forecasts to prevent fog related accidents. Improved fog forecasts require a better understanding of the numerous complex mechanisms during the fog life cycle. During winter 2012/13 a field campaign called ParisFog aiming at fog research took place at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research). SIRTA is located about 20 km southwest of the Paris city centre, France in a semi-urban environment. In situ activation properties of the prevailing fog were investigated by measuring: (1) total and interstitial (non-activated) dry particle number size distributions behind two different inlet systems; (2) interstitial hydrated aerosol and fog droplet size distributions at ambient conditions; (3) cloud condensation nuclei (CCN) number concentration at different supersaturations (SS) with a CCN counter. The aerosol particles were characterized regarding their hygroscopic properties, fog droplet activation behavior and contribution to light scattering for 17 developed fog events. Low particle hygroscopicity with an overall median of hygroscopicity parameter, κ, of 0.14 was found, likely caused by substantial influence from local traffic and wood burning emissions. Measurements of the aerosol size distribution at ambient RH revealed that the critical wet diameter, above which the hydrated aerosols activate to fog droplets, is rather large with a median value of 2.4 μm and is highly variable (ranging from 1 to 5 μm) between the different fog events. Thus, the number of activated fog droplets was very small and the non-activated hydrated particles were found to contribute siginificantly to the observed light scattering and thus to the reduction in visibility. Combining all experimental data, the effective peak supersaturation, SSpeak, a measure of the peak supersaturation

  2. Prevalence and associated features of self-reported freezing of gait in Parkinson disease: The DEEP FOG study.

    Science.gov (United States)

    Amboni, M; Stocchi, F; Abbruzzese, G; Morgante, L; Onofrj, M; Ruggieri, S; Tinazzi, M; Zappia, M; Attar, M; Colombo, D; Simoni, L; Ori, A; Barone, P; Antonini, A

    2015-06-01

    Freezing of Gait (FOG) is a common and disabling symptom in patients with Parkinson disease (PD). The relationship between FOG and dopaminergic medication is complex. The aim of the present study was to estimate the prevalence of self-reported FOG, its associated clinical features, and its relationship with wearing-off in a wide PD population. This is an observational multicenter study of 634 consecutive non-demented PD patients. Patients were identified either as freezers or non-freezers based on item-3 of the Freezing of Gait-Questionnaire. FOG was then classified as on, off and onoff freezing based on its relationship with wearing-off. Patients were assessed with Unified Parkinson's Disease Rating Scale, Hoehn and Yahr scale, 8-item Parkinson's disease Questionnaire, Mini-Mental State Examination. Data from 593 patients were analyzed, 325 (54.3%) were freezers of whom 200 (61.6%) experienced FOG only during off state (off-freezers), 6 (1.8%) only during on state and 119 (36.6%) either in on and off states or independently of dopaminergic response-related symptoms (onoff-freezers). Overall, freezers vs non-freezers had longer disease duration, more advanced disease and greater disability. Moreover, freezers more frequently reported wearing-off and experienced worse quality of life. Onoff-freezers vs off-freezers were older, more severely disabled, less likely to experience wearing-off, treated with lower levodopa equivalent daily dose and with poorer cognitive performance. Self-reported FOG is mainly recognizable in advanced PD and is associated with more disability and worse quality of life. Onoff-FOG may represent the result of under-treatment or rather interpretable as a distinct clinical entity.

  3. Smoothing of Fused Spectral Consistent Satellite Images with TV-based Edge Detection

    DEFF Research Database (Denmark)

    Sveinsson, Johannes; Aanæs, Henrik; Benediktsson, Jon Atli

    2007-01-01

    Several widely used methods have been proposed for fusing high resolution panchromatic data and lower resolution multi-channel data. However, many of these methods fail to maintain the spectral consistency of the fused high resolution image, which is of high importance to many of the applications...... based on satellite data. Additionally, most conventional methods are loosely connected to the image forming physics of the satellite image, giving these methods an ad hoc feel. Vesteinsson et al. [1] proposed a method of fusion of satellite images that is based on the properties of imaging physics...... in a statistically meaningful way and was called spectral consistent panshapening (SCP). In this paper we improve this framework for satellite image fusion by introducing a better image prior, via data-dependent image smoothing. The dependency is obtained via total variation edge detection method....

  4. A Novel Sampling Method for Satellite-Based Offshore Wind Resource Estimation

    DEFF Research Database (Denmark)

    Badger, Merete; Badger, Jake; Hasager, Charlotte Bay

    Synthetic aperture radar (SAR) measurements from satellites can be used to estimate the spatial wind speed variation offshore in great detail. The radar senses cm-scale roughness at the sea surface which can be translated to wind speed at the height 10 m using an empirical geophysical model......-based wind climatology have improved gradually as more data were collected. The satellite scenes have been treated as random samples and weighted equally in our previous analyses. Here we introduce a novel sampling strategy based on the wind class methodology that is normally applied in numerical modeling...... climatologically representative large-scale meteorological conditions for the region of interest. The wind classes are used to make the most representative selection of satellite images from the ENVISAT image catalogue. A minimum of one satellite image is chosen per wind class. The frequency of occurrence of each...

  5. Design and simulation of satellite attitude control system based on Simulink and VR

    Science.gov (United States)

    Zhang, Yang; Gan, Qingbo; Kang, Jingshu

    2016-01-01

    In order to research satellite attitude control system design and visual simulation, the simulation framework of satellite dynamics and attitude control using Simulink were established. The design of satellite earth-oriented control system based on quaternion feedback was completed. The 3D scene based on VR was created and models in the scene were driven by simulation data of Simulink. By coordinate transformation. successful observing the scene in inertial coordinate system, orbit coordinate system and body coordinate system. The result shows that application of simulation method of Simulink combined with VR in the design of satellite attitude control system field, has the advantages of high confidence level, hard real-time property, multi-perspective and multi-coordinate system observing the scene, and improves the comprehensibility and accuracy of the design.

  6. UKF-based attitude determination method for gyroless satellite

    Institute of Scientific and Technical Information of China (English)

    张红梅; 邓正隆

    2004-01-01

    UKF (unscented Kalman filtering) is a new filtering method suitable to nonlinear systems. The method need not linearize nonlinear systems at the prediction stage of filtering, which is indispensable in EKF (extended Kalman filtering). As a result, the linearization error is avoided, and the filtering accuracy is greatly improved. UKF is applied to the attitude determination for gyroless satellite. Simulations are made to compare the new filter with the traditional EKF.The results indicate that under same conditions, compared with EKF, UKF has faster convergence speed, higher filtering accuracy and more stable estimation performance.

  7. Satellite -Based Networks for U-Health & U-Learning

    Science.gov (United States)

    Graschew, G.; Roelofs, T. A.; Rakowsky, S.; Schlag, P. M.

    2008-08-01

    The use of modern Information and Communication Technologies (ICT) as enabling tools for healthcare services (eHealth) introduces new ways of creating ubiquitous access to high-level medical care for all, anytime and anywhere (uHealth). Satellite communication constitutes one of the most flexible methods of broadband communication offering high reliability and cost-effectiveness of connections meeting telemedicine communication requirements. Global networks and the use of computers for educational purposes stimulate and support the development of virtual universities for e-learning. Especially real-time interactive applications can play an important role in tailored and personalised services.

  8. Space-Based Observations of Satellites From the MOST Microsatellite

    Science.gov (United States)

    2006-11-01

    observations spatiales canadiennes d’un objet en orbite terrestre . Deux satellites de géolocalisation GPS ont été suivis à l’aide du télescope optique monté...the derived orbital metric data with high precision ephemerides yielded root mean square errors of 13 arcseconds. The errors are shown to result...space surveillance from an orbiting platform. Résumé Le 12 octobre 2005, le microsatellite MOST du Canada a acquis les premières images

  9. Processamento radiográfico - câmara escura portátil: relação entre filtro de luz e densidade de base + véu Radiographic processing - portable darkroom: relation between light filtering and base density plus fog

    Directory of Open Access Journals (Sweden)

    José Roberto TAMBURÚS

    1999-01-01

    Full Text Available O objetivo desta pesquisa foi avaliar o efeito sobre a densidade de base + véu de filmes radiográficos, decorrente do uso da luz filtrada pelo polímero acrílico utilizado nas câmaras portáteis para processamento radiográfico. Filmes Kodak Ultra-speed e Ektaspeed Plus foram colocados no interior de uma câmara desse tipo e submetidos durante cinco minutos às condições de iluminação natural e artificial em que elas são rotineiramente utilizadas. Depois disso, os filmes foram processados pelo método temperatura-tempo em câmara escura convencional, juntamente com filmes dos mesmos grupos de sensibilidade que serviram como controle. Os valores densitométricos obtidos das amostras dos filmes foram analisados pelo teste de Mann-Whitney que indicou ao nível de 1% de significância, que os filmes submetidos às condições da câmara portátil apresentaram densidades de base + véu maiores em relação aos grupos controle. Os resultados mostraram que o filme Ektaspeed Plus apresentou valores maiores de densidade de base + véu em comparação com o filme Ultra-speed e que, embora o acrílico filtre a luz de forma similar ao filtro Kodak GBX 2, a maior intensidade de luz no interior da câmara escura portátil ocasionou o aumento na densidade de base + véu.The aim of this study was to assess the base density plus fog of dental X-ray films affected by light filtered through a commercial portable acrylic chamber used for radiography processing. Both Kodak Ultra-speed and Ektaspeed Plus films were placed into an acrylic chamber and submitted to the incidence of simultaneous natural and artificial light for five minutes to mimic a routine procedure in dental practice. Using a time/temperature method, these films were processed in a conventional darkroom together with films from the same sensitivity group that had not been subjected to light incidence (control. Densitometric values were obtained from all samples and the data were analysed by

  10. Impact of activation process on fog life cycle

    Science.gov (United States)

    Mazoyer, Marie; Burnet, Frédéric; Lac, Christine; Roberts, Greg; Dupont, Jean-Charles; Haeffelin, Martial; Elias, Thierry

    2015-04-01

    Fogs are complex meteorological system dealing with fine scale processes. Subtle interaction between radiative, dynamic, turbulent and microphysic processes can lead to different fog life cycle, which make prediction difficult. The droplets that composed fogs are formed trough the activation of aerosol particles called CCN (cloud condensation nuclei) described by the Köhler theory (Köhler, 1936). The number and distribution of the droplets activated during fog formation is determined by the aerosols particles properties and number and the ambient vapor supersaturation of the atmosphere. In the frame of the PreViBOSS project, an in-situ measurement platform of fog properties at ground level was deployed at SIRTA (Instrumented Site for Atmospheric Remote Sensing Research) during winter 2010 to 2013. Microphysics data supply a detailed characterization of number size spectrum from dry to wet aerosols particles and inform on the abilities of the aerosols particles to act as a CCN. 48 fog events have been studied. Supersaturation critical values and concentrations of CCN have been determined and linked to aerosols properties. The main impact of aerosols size distribution on activation have been pointed out. The study of droplets spectra evolution reveals the major physical processes into fogs and suggests that even if thermodynamic dominates the fog life cycle, activation process seems to have a significant effect. Large eddy simulation of fog run with Meso-NH model allow to explore precisely the interaction between fog physical processes and to quantify activation impact. Supersaturation modelling is a key point, a new pseudo-prognostic scheme (Thouron et al., 2012) is used. Confrontation between a detailed experimental study and three-dimensional fine scale simulation in LES provides an accurate investigation of the impact of activation process on fog life cycle.

  11. Ice Fog and Light Snow Measurements Using a High-Resolution Camera System

    Science.gov (United States)

    Kuhn, Thomas; Gultepe, Ismail

    2016-09-01

    Ice fog, diamond dust, and light snow usually form over extremely cold weather conditions, and they affect both visibility and Earth's radiative energy budget. Prediction of these hydrometeors using models is difficult because of limited knowledge of the microphysical properties at the small size ranges due to measurement issues. These phenomena need to be better represented in forecast and climate models; therefore, in addition to remote sensing accurate measurements using ground-based instrumentation are required. An imaging instrument, aimed at measuring ice fog and light snow particles, has been built and is presented here. The ice crystal imaging (ICI) probe samples ice particles into a vertical, tapered inlet with an inlet flow rate of 11 L min-1. A laser beam across the vertical air flow containing the ice crystals allows for their detection by a photodetector collecting the scattered light. Detected particles are then imaged with high optical resolution. An illuminating LED flash and image capturing are triggered by the photodetector. In this work, ICI measurements collected during the fog remote sensing and modeling (FRAM) project, which took place during Winter of 2010-2011 in Yellowknife, NWT, Canada, are summarized and challenges related to measuring small ice particles are described. The majority of ice particles during the 2-month-long campaign had sizes between 300 and 800 μm. During ice fog events the size distribution measured had a lower mode diameter of 300 μm compared to the overall campaign average with mode at 500 μm.

  12. Secondary organic aerosol formation in cloud and fog droplets: a literature evaluation of plausibility

    Science.gov (United States)

    Blando, James D.; Turpin, Barbara J.

    This paper investigates the hypothesis that cloud and fog processes produce fine organic particulate matter in the atmosphere. The evidence provided suggests that cloud and fog processes could be important contributors to secondary organic aerosol formation, and the contribution of this formation pathway should be further investigated. This conclusion is based on the following observations: (1) many organic vapors present in the atmosphere are sorbed by suspended droplets and have been measured in cloud and fog water, (2) organics participate in aqueous-phase reactions, and (3) organic particulate matter is sometimes found in the size mode attributed to cloud processing (i.e. the droplet mode). Specific compounds identified as potential precursors include aldehydes (e.g. formaldehyde, acetaldehyde, and propionaldehyde), acetone, alcohols (e.g. methanol, ethanol, 2-propanol, and phenol), monocarboxylic acids, and organic peroxides. Carboxylic acids (e.g. diacids and oxo-acids), glyoxal, esters, organosulfur compounds, polyols, amines and amino acids are potential products of cloud and fog processing.

  13. Coastal fog during summer drought improves the water status of sapling trees more than adult trees in a California pine forest.

    Science.gov (United States)

    Baguskas, Sara A; Still, Christopher J; Fischer, Douglas T; D'Antonio, Carla M; King, Jennifer Y

    2016-05-01

    Fog water inputs can offset seasonal drought in the Mediterranean climate of coastal California and may be critical to the persistence of many endemic plant species. The ability to predict plant species response to potential changes in the fog regime hinges on understanding the ways that fog can impact plant physiological function across life stages. Our study uses a direct metric of water status, namely plant water potential, to understand differential responses of adult versus sapling trees to seasonal drought and fog water inputs. We place these measurements within a water balance framework that incorporates the varying climatic and soil property impacts on water budgets and deficit. We conducted our study at a coastal and an inland site within the largest stand of the regionally endemic bishop pine (Pinus muricata D. Don) on Santa Cruz Island. Our results show conclusively that summer drought negatively affects the water status of sapling more than adult trees and that sapling trees are also more responsive to changes in shallow soil moisture inputs from fog water deposition. Moreover, between the beginning and end of a large, late-season fog drip event, water status increased more for saplings than for adults. Relative to non-foggy conditions, we found that fog water reduces modeled peak water deficit by 80 and 70 % at the inland and coastal sites, respectively. Results from our study inform mechanistically based predictions of how population dynamics of this and other coastal species may be affected by a warmer, drier, and potentially less foggy future.

  14. Satellite image based methods for fuels maps updating

    Science.gov (United States)

    Alonso-Benito, Alfonso; Hernandez-Leal, Pedro A.; Arbelo, Manuel; Gonzalez-Calvo, Alejandro; Moreno-Ruiz, Jose A.; Garcia-Lazaro, Jose R.

    2016-10-01

    Regular updating of fuels maps is important for forest fire management. Nevertheless complex and time consuming field work is usually necessary for this purpose, which prevents a more frequent update. That is why the assessment of the usefulness of satellite data and the development of remote sensing techniques that enable the automatic updating of these maps, is of vital interest. In this work, we have tested the use of the spectral bands of OLI (Operational Land Imager) sensor on board Landsat 8 satellite, for updating the fuels map of El Hierro Island (Spain). From previously digitized map, a set of 200 reference plots for different fuel types was created. A 50% of the plots were randomly used as a training set and the rest were considered for validation. Six supervised and 2 unsupervised classification methods were applied, considering two levels of detail. A first level with only 5 classes (Meadow, Brushwood, Undergrowth canopy cover >50%, Undergrowth canopy cover <15%, and Xeric formations), and the second one containing 19 fuel types. The level 1 classification methods yielded an overall accuracy ranging from 44% for Parellelepided to an 84% for Maximun Likelihood. Meanwhile, level 2 results showed at best, an unacceptable overall accuracy of 34%, which prevents the use of this data for such a detailed characterization. Anyway it has been demonstrated that in some conditions, images of medium spatial resolution, like Landsat 8-OLI, could be a valid tool for an automatic upgrade of fuels maps, minimizing costs and complementing traditional methodologies.

  15. Authentication Scheme Based on Principal Component Analysis for Satellite Images

    Directory of Open Access Journals (Sweden)

    Ashraf. K. Helmy

    2009-09-01

    Full Text Available This paper presents a multi-band wavelet image content authentication scheme for satellite images by incorporating the principal component analysis (PCA. The proposed schemeachieves higher perceptual transparency and stronger robustness. Specifically, the developed watermarking scheme can successfully resist common signal processing such as JPEG compression and geometric distortions such as cropping. In addition, the proposed scheme can be parameterized, thus resulting in more security. That is, an attacker may not be able to extract the embedded watermark if the attacker does not know the parameter.In an order to meet these requirements, the host image is transformed to YIQ to decrease the correlation between different bands, Then Multi-band Wavelet transform (M-WT is applied to each channel separately obtaining one approximate sub band and fifteen detail sub bands. PCA is then applied to the coefficients corresponding to the same spatial location in all detail sub bands. The last principle component band represents an excellent domain forinserting the water mark since it represents lowest correlated features in high frequency area of host image.One of the most important aspects of satellite images is spectral signature, the behavior of different features in different spectral bands, the results of proposed algorithm shows that the spectral stamp for different features doesn't tainted after inserting the watermark.

  16. A facile strategy for the fabrication of a bioinspired hydrophilic-superhydrophobic patterned surface for highly efficient fog-harvesting

    KAUST Repository

    Wang, Yuchao

    2015-08-10

    Fog water collection represents a meaningful effort in the places where regular water sources, including surface water and ground water, are scarce. Inspired by the amazing fog water collection capability of Stenocara beetles in the Namib Desert and based on the recent work in biomimetic water collection, this work reported a facile, easy-to-operate, and low-cost method for the fabrication of hydrophilic-superhydrophobic patterned hybrid surface toward highly efficient fog water collection. The essence of the method is incorporating a (super)hydrophobically modified metal-based gauze onto the surface of a hydrophilic polystyrene (PS) flat sheet by a simple lab oven-based thermal pressing procedure. The produced hybrid patterned surfaces consisted of PS patches sitting within the holes of the metal gauzes. The method allows for an easy control over the pattern dimension (e.g., patch size) by varying gauze mesh size and thermal pressing temperature, which is then translated to an easy optimization of the ultimate fog water collection efficiency. Given the low-cost and wide availability of both PS and metal gauze, this method has a great potential for scaling-up. The results showed that the hydrophilic-superhydrophobic patterned hybrid surfaces with a similar pattern size to Stenocara beetles’s back pattern produced significantly higher fog collection efficiency than the uniformly (super)hydrophilic or (super)hydrophobic surfaces. This work contributes to general effort in fabricating wettability patterned surfaces and to atmospheric water collection for direct portal use.

  17. A scalable satellite-based crop yield mapper: Integrating satellites and crop models for field-scale estimation in India

    Science.gov (United States)

    Jain, M.; Singh, B.; Srivastava, A.; Lobell, D. B.

    2015-12-01

    Food security will be challenged over the upcoming decades due to increased food demand, natural resource degradation, and climate change. In order to identify potential solutions to increase food security in the face of these changes, tools that can rapidly and accurately assess farm productivity are needed. With this aim, we have developed generalizable methods to map crop yields at the field scale using a combination of satellite imagery and crop models, and implement this approach within Google Earth Engine. We use these methods to examine wheat yield trends in Northern India, which provides over 15% of the global wheat supply and where over 80% of farmers rely on wheat as a staple food source. In addition, we identify the extent to which farmers are shifting sow date in response to heat stress, and how well shifting sow date reduces the negative impacts of heat stress on yield. To identify local-level decision-making, we map wheat sow date and yield at a high spatial resolution (30 m) using Landsat satellite imagery from 1980 to the present. This unique dataset allows us to examine sow date decisions at the field scale over 30 years, and by relating these decisions to weather experienced over the same time period, we can identify how farmers learn and adapt cropping decisions based on weather through time.

  18. Validation of PV performance models using satellite-based irradiance measurements : a case study.

    Energy Technology Data Exchange (ETDEWEB)

    Stein, Joshua S.; Parkins, Andrew (Clean Power Research); Perez, Richard (University at Albany)

    2010-05-01

    Photovoltaic (PV) system performance models are relied upon to provide accurate predictions of energy production for proposed and existing PV systems under a wide variety of environmental conditions. Ground based meteorological measurements are only available from a relatively small number of locations. In contrast, satellite-based radiation and weather data (e.g., SUNY database) are becoming increasingly available for most locations in North America, Europe, and Asia on a 10 x 10 km grid or better. This paper presents a study of how PV performance model results are affected when satellite-based weather data is used in place of ground-based measurements.

  19. 光纤陀螺随机漂移在线建模实时滤波技术%Real-time Filtering Research Based on On-line Modeling Random Drift of FOG

    Institute of Scientific and Technical Information of China (English)

    金毅; 吴训忠; 谢聂; 郭创

    2015-01-01

    Establishing the model of FOG’s random drift and compensating in the filter is an effective method to improve the output precision of FOG. For traditional random drift of fiber optical gyroscope has some shortages like off-line, needing pre-process and the off-line models, which are usually not universal for environmental changing, a new modeling and filtering way is put forward. First, based on a large amount of measured data, the traditional off-line AR model is improved, and a new method to build the model of FOG’s random drift is studied. Then, the comparison is made between the traditional Kalman filter andH∞ filter in real time. The result demonstrates that improved AR model has much applicability and the performance ofH∞ filter is better than Kalman filter. The minimum value of fitting accuracy is 91.6% andH∞ filter can improve the performance of filtering by almost 38.5% when analyzing ingle noise.%建立光纤陀螺随机漂移模型以便在滤波中加以补偿是提高光纤陀螺输出精度的有效方法。针对传统光纤陀螺随机漂移建模均采用离线形式,需预先处理数据,不具备普适性等问题,提出一种实时的建模滤波方法。首先,根据大量实测数据对传统离线模型进行改进,研究了一种基于AR模型的在线建立光纤陀螺随机漂移模型的方法。然后,比较了传统Kalman滤波器与H∞滤波器用于实时滤波的效果。实验结果表明,改进型AR模型拟合精度高、普适性强,单个噪声拟合精度最低值为91.6%。H∞滤波器效果优于传统的 Kalman 滤波器,分析单个噪声滤波效果时,H∞滤波器较Kalman滤波器性能最多可提高38.5%。

  20. Towards a satellite-based sea ice climate data record

    Science.gov (United States)

    Meier, W. N.; Fetterer, F.; Stroeve, J.; Cavalieri, D.; Parkinson, C.; Comiso, J.; Weaver, R.

    2005-12-01

    Sea ice plays an important role in the Earth's climate through its influence on the surface albedo, heat and moisture transfer between the ocean and the atmosphere, and the thermohaline circulation. Satellite data reveal that since 1979, summer Arctic sea ice has, overall, been declining at a rate of almost 8%/decade, with recent summers (beginning in 2002) being particularly low. The receding sea ice is having an effect on wildlife and indigenous peoples in the Arctic, and concern exists that these effects may become increasingly severe. Thus, a long-term, ongoing climate data record of sea ice is crucial for tracking the changes in sea ice and for assessing the significance of long-term trends. Since the advent of passive microwave satellite instruments in the early 1970s, sea ice has been one of the most consistently monitored climate parameters. There is now a 27+ year record of sea ice extent and concentration from multi-channel passive microwave radiometers that has undergone inter-sensor calibration and other quality controls to ensure consistency throughout the record. Several algorithms have been developed over the years to retrieve sea ice extent and concentration and two of the most commonly used algorithms, the NASA Team and Bootstrap, have been applied to the entire SMMR-SSM/I record to obtain a consistent time series. These algorithms were developed at NASA Goddard Space Flight Center and are archived at the National Snow and Ice Data Center. However, the complex surface properties of sea ice affect the microwave signature, and algorithms can yield ambiguous results; no single algorithm has been found to work uniformly well under all sea ice conditions. Thus there are ongoing efforts to further refine the algorithms and the time series. One approach is to develop data fusion methods to optimally combine sea ice fields from two or more algorithms. Another approach is to take advantage of the improved capabilities of JAXA's AMSR-E sensor on NASA's Aqua

  1. Fog deposition to a Tillandsia carpet in the Atacama Desert

    Directory of Open Access Journals (Sweden)

    P. Osses

    2009-09-01

    Full Text Available In the Atacama Desert, one of the driest places on earth, fog deposition plays an important role for the water balance and for the survival of vulnerable ecosystems. The eddy covariance method, previously applied for the quantification of fog deposition to forests in various parts of the world, was used for the first time to measure deposition of fog water to a desert. In this exploratory study we estimate the amount of water available for the ecosystem by deposition and determine the relevant processes driving fog deposition. This is especially important for the species Tillandsia landbecki living in coastal Atacama at the limit of plant existence with fog and dew being the only sources of water. Between 31 July and 19 August 2008 approximately 2.5 L m−2 of water were made available through deposition. Whole-year deposition was estimated as 25 L m−2. Turbulent upward fluxes occurred several times during the evenings and are explained by the formation of radiation fog. In connection with that, underestimates of the deposition are assumed. More detailed studies covering various seasons and all parameters and fluxes contributing to the local energy balance are suggested. This will help to further develop understanding about the processes of (i deposition of water to the desert, and (ii intensification of advection fog through additional formation of radiation fog.

  2. Clearing the Fog from the Undergraduate Course in Linear Algebra

    Science.gov (United States)

    Scott, Damon

    2007-01-01

    For over a decade it has been a common observation that a "fog" passes over the course in linear algebra once abstract vector spaces are presented. See [2, 3]. We show how this fog may be cleared by having the students translate "abstract" vector-space problems to isomorphic "concrete" settings, solve the "concrete" problem either by hand or with…

  3. Energy-Efficient Network Transmission between Satellite Swarms and Earth Stations Based on Lyapunov Optimization Techniques

    Directory of Open Access Journals (Sweden)

    Weiwei Fang

    2014-01-01

    Full Text Available The recent advent of satellite swarm technologies has enabled space exploration with a massive number of picoclass, low-power, and low-weight spacecraft. However, developing swarm-based satellite systems, from conceptualization to validation, is a complex multidisciplinary activity. One of the primary challenges is how to achieve energy-efficient data transmission between the satellite swarm and terrestrial terminal stations. Employing Lyapunov optimization techniques, we present an online control algorithm to optimally dispatch traffic load among different satellite-ground links for minimizing overall energy consumption over time. Our algorithm is able to independently and simultaneously make control decisions on traffic dispatching over intersatellite-links and up-down-links so as to offer provable energy and delay guarantees, without requiring any statistical information of traffic arrivals and link condition. Rigorous analysis and extensive simulations have demonstrated the performance and robustness of the proposed new algorithm.

  4. Satellite Fault Diagnosis Using Support Vector Machines Based on a Hybrid Voting Mechanism

    Directory of Open Access Journals (Sweden)

    Hong Yin

    2014-01-01

    Full Text Available The satellite fault diagnosis has an important role in enhancing the safety, reliability, and availability of the satellite system. However, the problem of enormous parameters and multiple faults makes a challenge to the satellite fault diagnosis. The interactions between parameters and misclassifications from multiple faults will increase the false alarm rate and the false negative rate. On the other hand, for each satellite fault, there is not enough fault data for training. To most of the classification algorithms, it will degrade the performance of model. In this paper, we proposed an improving SVM based on a hybrid voting mechanism (HVM-SVM to deal with the problem of enormous parameters, multiple faults, and small samples. Many experimental results show that the accuracy of fault diagnosis using HVM-SVM is improved.

  5. Using Multi-Isotope Tracer Methods to Understand the Sources of Nitrate in Aerosols, Fog and River Water in Podocarpus National Forest, Ecuador

    Science.gov (United States)

    Brothers, L. A.; Dominguez, G.; Fabian, P.; Thiemens, M. H.

    2008-12-01

    sulfate and nitrate concentrations in rain and fog water by standard methods to investigate water and nutrient pathways along with data from satellite and ground based remote sensing, observations and numerical models. We hope to pair this with a multi-isotope tracer method and NOAA Hysplit Back trajectories, and satellite imagery for information about the number of fires burning in the region to help identify sources of the high nitrate deposition.

  6. Validation of satellite-based noontime UVI with NDACC ground-based instruments: influence of topography, environment and satellite overpass time

    Science.gov (United States)

    Brogniez, Colette; Auriol, Frédérique; Deroo, Christine; Arola, Antti; Kujanpää, Jukka; Sauvage, Béatrice; Kalakoski, Niilo; Riku Aleksi Pitkänen, Mikko; Catalfamo, Maxime; Metzger, Jean-Marc; Tournois, Guy; Da Conceicao, Pierre

    2016-12-01

    Spectral solar UV radiation measurements are performed in France using three spectroradiometers located at very different sites. One is installed in Villeneuve d'Ascq, in the north of France (VDA). It is an urban site in a topographically flat region. Another instrument is installed in Observatoire de Haute-Provence, located in the southern French Alps (OHP). It is a rural mountainous site. The third instrument is installed in Saint-Denis, Réunion Island (SDR). It is a coastal urban site on a small mountainous island in the southern tropics. The three instruments are affiliated with the Network for the Detection of Atmospheric Composition Change (NDACC) and carry out routine measurements to monitor the spectral solar UV radiation and enable derivation of UV index (UVI). The ground-based UVI values observed at solar noon are compared to similar quantities derived from the Ozone Monitoring Instrument (OMI, onboard the Aura satellite) and the second Global Ozone Monitoring Experiment (GOME-2, onboard the Metop-A satellite) measurements for validation of these satellite-based products. The present study concerns the period 2009-September 2012, date of the implementation of a new OMI processing tool. The new version (v1.3) introduces a correction for absorbing aerosols that were not considered in the old version (v1.2). Both versions of the OMI UVI products were available before September 2012 and are used to assess the improvement of the new processing tool. On average, estimates from satellite instruments always overestimate surface UVI at solar noon. Under cloudless conditions, the satellite-derived estimates of UVI compare satisfactorily with ground-based data: the median relative bias is less than 8 % at VDA and 4 % at SDR for both OMI v1.3 and GOME-2, and about 6 % for OMI v1.3 and 2 % for GOME-2 at OHP. The correlation between satellite-based and ground-based data is better at VDA and OHP (about 0.99) than at SDR (0.96) for both space-borne instruments. For all

  7. Fairness based channel borrowing strategy in multimedia LEO satellite communications

    Institute of Scientific and Technical Information of China (English)

    HUANG Fei; XU Hui; WU Shiqi

    2007-01-01

    A novel bandwidth allocation strategy along with a connection admission control technique was proposed to improve the utilization of network resources.It provides the network with better quality-of-service (QoS) guarantees,such as new call blocking probability (CBP) and handoff call dropping probability (CDP) in multimedia low earth orbit (LEO) satellite networks.Simulation results show that,compared with other bandwidth allocation schemes,the proposed scheme offers very low call dropping probability for real-time connections while,at the same time,keeping resource utilization high.Finally we discussed the fairness for the borrowed nonreal-time connections under three different channel borrowing methods.

  8. A new algorithm for agile satellite-based acquisition operations

    Science.gov (United States)

    Bunkheila, Federico; Ortore, Emiliano; Circi, Christian

    2016-06-01

    Taking advantage of the high manoeuvrability and the accurate pointing of the so-called agile satellites, an algorithm which allows efficient management of the operations concerning optical acquisitions is described. Fundamentally, this algorithm can be subdivided into two parts: in the first one the algorithm operates a geometric classification of the areas of interest and a partitioning of these areas into stripes which develop along the optimal scan directions; in the second one it computes the succession of the time windows in which the acquisition operations of the areas of interest are feasible, taking into consideration the potential restrictions associated with these operations and with the geometric and stereoscopic constraints. The results and the performances of the proposed algorithm have been determined and discussed considering the case of the Periodic Sun-Synchronous Orbits.

  9. Possible ground fog detection from SLI imagery of Titan

    CERN Document Server

    Smith, Christina L; Moores, John E

    2016-01-01

    Titan, with its thick, nitrogen-dominated atmosphere, has been seen from satellite and terrestrial observations to harbour methane clouds. To investigate whether atmospheric features such as clouds could also be visible from the surface of Titan, data taken with the Side Looking Imager (SLI) on-board the Huygens probe after landing have been analysed to identify any potential atmospheric features. In total, 82 SLI images were calibrated, processed and examined for features. The calibrated images show a smooth vertical radiance gradient across the images, with no other discernible features. After mean-frame subtraction, six images contained an extended, horizontal feature that had a radiance value that lay outside the 95% confidence limit of the predicted radiance when compared to regions higher and lower in the images. The change in optical depth of these features were found to be between 0.005 and 0.014. It is considered that these features most likely originate from the presence of a fog bank close to the h...

  10. Characterization of satellite based proxies for estimating nucleation mode particles over South Africa

    Directory of Open Access Journals (Sweden)

    A.-M. Sundström

    2014-10-01

    Full Text Available In this work satellite observations from the NASA's A-Train constellation were used to derive the values of primary emission and regional nucleation proxies over South Africa to estimate the potential for new particle formation. As derived in Kulmala et al. (2011, the satellite based proxies consist of source terms (NO2, SO2 and UV-B radiation, and a sink term describing the pre-existing aerosols. The first goal of this work was to study in detail the use of satellite aerosol optical depth (AOD as a substitute to the in situ based condensation sink (CS. One of the major factors affecting the agreement of CS and AOD was the elevated aerosol layers that increased the value of column integrated AOD but not affected the in situ CS. However, when the AOD in the proxy sink was replaced by an estimate from linear bivariate fit between AOD and CS, the agreement with the actual nucleation mode number concentration improved somewhat. The second goal of the work was to estimate how well the satellite based proxies can predict the potential for new particle formation. For each proxy the highest potential for new particle formation were observed over the Highveld industrial area, where the emissions were high but the sink due to pre-existing aerosols was relatively low. Best agreement between the satellite and in situ based proxies were obtained for NO2/AOD and UV-B/AOD2, whereas proxies including SO2 in the source term had lower correlation. Even though the OMI SO2 boundary layer product showed reasonable spatial pattern and detected the major sources over the study area, some of the known minor point sources were not detected. When defining the satellite proxies only for days when new particle formation event was observed, it was seen that for all the satellite based proxies the event day medians were higher than the entire measurement period median.

  11. The irradiating field of view of imaging laser radar under fog conditions in a controlled laboratory environment

    Science.gov (United States)

    Song, Wen-Hua; Ghassemlooy, Zabih; Lai, Jian-Cheng; Yan, Wei; Wang, Chun-Yong; Li, Zhen-Hua

    2017-04-01

    This paper theoretically and experimentally investigates the performance of the imaging laser radar (ILR) system under the fog condition. Fog is generated and controlled homogeneously within a dedicated indoor atmospheric chamber. A physical model of the reflected laser pulses due to fog and a standard Lambertian target are developed to determine the width of each echo pulse for different fog concentrations. We show that there is a good agreement between the predicted and measured results for the width of backscattered return pulses. Based on experimental results an empirical model of the horizontal and vertical irradiating field of views (FOVs) of ILR under different visibilities is also developed. Consequently, a new model is proposed to predict the horizontal and vertical irradiating FOVs of ILR by using the width of the backscattered return pulse under different fog conditions. The reported results can be used to dynamically adjust the scanning interval based on the variation of the irradiating FOVs of laser radar and improve the precision of target ranging and imaging.

  12. Wave energy resource assessment based on satellite observations around Indonesia

    Science.gov (United States)

    Ribal, Agustinus; Zieger, Stefan

    2016-06-01

    A preliminary assessment of wave energy resource around Indonesian's ocean has been carried out by means of analyzing satellite observations. The wave energy flux or wave power can be approximated using parameterized sea states. Wave power scales with significant wave height, characteristic wave period and water depth. In this approach, the significant wave heights were obtained from ENVISAT (Environmental Satellite) data which have been calibrated. However, as the characteristic wave period is rarely specified and therefore must be estimated from other variables when information about the wave spectra is unknown. Here, the characteristic wave period was calculated with an empirical model that utilizes altimeter estimates of wave height and backscatter coefficient originally proposed. For the Indonesian region, wave power energy is calculated over two periods of one year each and was compared with the results from global hindcast carried out with a recent release of wave model WAVEWATCH III. We found that, the most promising wave power energy regions around the Indonesian archipelago are located in the south of Java island and the south west of Sumatera island. In these locations, about 20 - 30 kW/m (90th percentile: 30-50 kW/m, 99th percentile: 40-60 kW/m) wave power energy on average has been found around south of Java island during 2010. Similar results have been found during 2011 at the same locations. Some small areas which are located around north of Irian Jaya (West Papua) are also very promising and need further investigation to determine its capacity as a wave energy resource.

  13. Simulation and Analysis of Autonomous Time Synchronization Based on Asynchronism Two-way Inter-satellite Link

    Science.gov (United States)

    Fang, L.; Yang, X. H.; Sun, B. Q.; Qin, W. J.; Kong, Y.

    2013-09-01

    The measurement of the inter-satellite link is one of the key techniques in the autonomous operation of satellite navigation system. Based on the asynchronism inter-satellite two-way measurement mode in GPS constellation, the reduction formula of the inter-satellite time synchronization is built in this paper. Moreover, the corrective method of main systematic errors is proposed. Inter-satellite two-way time synchronization is simulated on the basis of IGS (International GNSS Service) precise ephemeris. The impacts of the epoch domestication of asynchronism inter-satellite link pseudo-range, the initial orbit, and the main systematic errors on satellite time synchronization are analyzed. Furthermore, the broadcast clock error of each satellite is calculated by the ``centralized'' inter-satellite autonomous time synchronization. Simulation results show that the epoch domestication of asynchronism inter-satellite link pseudo-range and the initial orbit have little impact on the satellite clock errors, and thus they needn't be taken into account. The errors caused by the relativistic effect and the asymmetry of path travel have large impact on the satellite clock errors. These should be corrected with theoretical formula. Compared with the IGS precise clock error, the root mean square of the broadcast clock error of each satellite is about 0.4 ns.

  14. Object Based and Pixel Based Classification Using Rapideye Satellite Imager of ETI-OSA, Lagos, Nigeria

    Directory of Open Access Journals (Sweden)

    Esther Oluwafunmilayo Makinde

    2016-12-01

    Full Text Available Several studies have been carried out to find an appropriate method to classify the remote sensing data. Traditional classification approaches are all pixel-based, and do not utilize the spatial information within an object which is an important source of information to image classification. Thus, this study compared the pixel based and object based classification algorithms using RapidEye satellite image of Eti-Osa LGA, Lagos. In the object-oriented approach, the image was segmented to homogenous area by suitable parameters such as scale parameter, compactness, shape etc. Classification based on segments was done by a nearest neighbour classifier. In the pixel-based classification, the spectral angle mapper was used to classify the images. The user accuracy for each class using object based classification were 98.31% for waterbody, 92.31% for vegetation, 86.67% for bare soil and 90.57% for Built up while the user accuracy for the pixel based classification were 98.28% for waterbody, 84.06% for Vegetation 86.36% and 79.41% for Built up. These classification techniques were subjected to accuracy assessment and the overall accuracy of the Object based classification was 94.47%, while that of Pixel based classification yielded 86.64%. The result of classification and accuracy assessment show that the object-based approach gave more accurate and satisfying results

  15. Adjusting thresholds of satellite-based convective initiation interest fields based on the cloud environment

    Science.gov (United States)

    Jewett, Christopher P.; Mecikalski, John R.

    2013-11-01

    The Time-Space Exchangeability (TSE) concept states that similar characteristics of a given property are closely related statistically for objects or features within close proximity. In this exercise, the objects considered are growing cumulus clouds, and the data sets to be considered in a statistical sense are geostationary satellite infrared (IR) fields that help describe cloud growth rates, cloud top heights, and whether cloud tops contain significant amounts of frozen hydrometeors. In this exercise, the TSE concept is applied to alter otherwise static thresholds of IR fields of interest used within a satellite-based convective initiation (CI) nowcasting algorithm. The convective environment in which the clouds develop dictate growth rate and precipitation processes, and cumuli growing within similar mesoscale environments should have similar growth characteristics. Using environmental information provided by regional statistics of the interest fields, the thresholds are examined for adjustment toward improving the accuracy of 0-1 h CI nowcasts. Growing cumulus clouds are observed within a CI algorithm through IR fields for many 1000 s of cumulus cloud objects, from which statistics are generated on mesoscales. Initial results show a reduction in the number of false alarms of ~50%, yet at the cost of eliminating approximately ~20% of the correct CI forecasts. For comparison, static thresholds (i.e., with the same threshold values applied across the entire satellite domain) within the CI algorithm often produce a relatively high probability of detection, with false alarms being a significant problem. In addition to increased algorithm performance, a benefit of using a method like TSE is that a variety of unknown variables that influence cumulus cloud growth can be accounted for without need for explicit near-cloud observations that can be difficult to obtain.

  16. Cooling analysis of a light emitting diode automotive fog lamp

    Directory of Open Access Journals (Sweden)

    Zadravec Matej

    2017-01-01

    Full Text Available Efficiency of cooling fins inside of a light emitting diode fog lamp is studied using computational fluid dynamics. Diffusion in heat sink, natural convection and radiation are the main principles of the simulated heat transfer. The Navier-Stokes equations were solved by the computational fluid dynamics code, including Monte Carlo radiation model and no additional turbulence model was needed. The numerical simulation is tested using the existing lamp geometry and temperature measurements. The agreement is excellent inside of few degrees at all measured points. The main objective of the article is to determine the cooling effect of various heat sink parts. Based on performed simulations, some heat sink parts are found to be very ineffective. The geometry and heat sink modifications are proposed. While radiation influence is significant, compressible effects are found to be minor.

  17. Detecting Anomaly Regions in Satellite Image Time Series Based on Sesaonal Autocorrelation Analysis

    Science.gov (United States)

    Zhou, Z.-G.; Tang, P.; Zhou, M.

    2016-06-01

    Anomaly regions in satellite images can reflect unexpected changes of land cover caused by flood, fire, landslide, etc. Detecting anomaly regions in satellite image time series is important for studying the dynamic processes of land cover changes as well as for disaster monitoring. Although several methods have been developed to detect land cover changes using satellite image time series, they are generally designed for detecting inter-annual or abrupt land cover changes, but are not focusing on detecting spatial-temporal changes in continuous images. In order to identify spatial-temporal dynamic processes of unexpected changes of land cover, this study proposes a method for detecting anomaly regions in each image of satellite image time series based on seasonal autocorrelation analysis. The method was validated with a case study to detect spatial-temporal processes of a severe flooding using Terra/MODIS image time series. Experiments demonstrated the advantages of the method that (1) it can effectively detect anomaly regions in each of satellite image time series, showing spatial-temporal varying process of anomaly regions, (2) it is flexible to meet some requirement (e.g., z-value or significance level) of detection accuracies with overall accuracy being up to 89% and precision above than 90%, and (3) it does not need time series smoothing and can detect anomaly regions in noisy satellite images with a high reliability.

  18. DETECTING ANOMALY REGIONS IN SATELLITE IMAGE TIME SERIES BASED ON SESAONAL AUTOCORRELATION ANALYSIS

    Directory of Open Access Journals (Sweden)

    Z.-G. Zhou

    2016-06-01

    Full Text Available Anomaly regions in satellite images can reflect unexpected changes of land cover caused by flood, fire, landslide, etc. Detecting anomaly regions in satellite image time series is important for studying the dynamic processes of land cover changes as well as for disaster monitoring. Although several methods have been developed to detect land cover changes using satellite image time series, they are generally designed for detecting inter-annual or abrupt land cover changes, but are not focusing on detecting spatial-temporal changes in continuous images. In order to identify spatial-temporal dynamic processes of unexpected changes of land cover, this study proposes a method for detecting anomaly regions in each image of satellite image time series based on seasonal autocorrelation analysis. The method was validated with a case study to detect spatial-temporal processes of a severe flooding using Terra/MODIS image time series. Experiments demonstrated the advantages of the method that (1 it can effectively detect anomaly regions in each of satellite image time series, showing spatial-temporal varying process of anomaly regions, (2 it is flexible to meet some requirement (e.g., z-value or significance level of detection accuracies with overall accuracy being up to 89% and precision above than 90%, and (3 it does not need time series smoothing and can detect anomaly regions in noisy satellite images with a high reliability.

  19. Object-based illumination normalization for multi-temporal satellite images in urban area

    Science.gov (United States)

    Su, Nan; Zhang, Ye; Tian, Shu; Yan, Yiming

    2016-09-01

    Multi-temporal satellite images acquisition with different illumination conditions cause radiometric difference to have a huge effect on image quality during remote sensing image processing. In particular, image matching of satellite stereo images with great difference between acquisition dates is very difficult for the high-precision DSM generation in the field of satellite photogrammetry. Therefore, illumination normalization is one of the greatest application technology to eliminate radiometric difference for image matching and other image applications. In this paper, we proposed a novel method of object-based illumination normalization to improve image matching of different temporal satellite stereo images in urban area. Our proposed method include two main steps: 1) the object extraction 2) multi-level illumination normalization. Firstly, we proposed a object extraction method for the same objects extraction among the multi-temporal satellite images, which can keep the object structural attribute. Moreover, the multi-level illumination normalization is proposed by combining gradient domain method and singular value decomposition (SVD) according to characteristic information of relevant objects. Our proposed method has great improvement for the illumination of object area to be benefit for image matching in urban area with multiple objects. And the histogram similarity parameter and matching rate are used for illumination consistency quantitative evaluation. The experiments have been conducted on different satellite images with different acquisition dates in the same urban area to verify the effectiveness of our proposed method. The experimental results demonstrate a good performance by comparing other methods.

  20. Assessing Satellite-Based Fire Data for use in the National Emissions Inventory

    Science.gov (United States)

    Soja, Amber J.; Al-Saadi, Jassim; Giglio, Louis; Randall, Dave; Kittaka, Chieko; Pouliot, George; Kordzi, Joseph J.; Raffuse, Sean; Pace, Thompson G.; Pierce, Thomas E.; Moore, Tom; Biswadev, Roy; Pierce, R. Bradley; Szykman, James J.

    2009-01-01

    Biomass burning is significant to emission estimates because: (1) it can be a major contributor of particulate matter and other pollutants; (2) it is one of the most poorly documented of all sources; (3) it can adversely affect human health; and (4) it has been identified as a significant contributor to climate change through feedbacks with the radiation budget. Additionally, biomass burning can be a significant contributor to a regions inability to achieve the National Ambient Air Quality Standards for PM 2.5 and ozone, particularly on the top 20% worst air quality days. The United States does not have a standard methodology to track fire occurrence or area burned, which are essential components to estimating fire emissions. Satellite imagery is available almost instantaneously and has great potential to enhance emission estimates and their timeliness. This investigation compares satellite-derived fire data to ground-based data to assign statistical error and helps provide confidence in these data. The largest fires are identified by all satellites and their spatial domain is accurately sensed. MODIS provides enhanced spatial and temporal information, and GOES ABBA data are able to capture more small agricultural fires. A methodology is presented that combines these satellite data in Near-Real-Time to produce a product that captures 81 to 92% of the total area burned by wildfire, prescribed, agricultural and rangeland burning. Each satellite possesses distinct temporal and spatial capabilities that permit the detection of unique fires that could be omitted if using data from only one satellite.

  1. Satellite-Based actual evapotranspiration over drying semiarid terrain in West-Africa

    NARCIS (Netherlands)

    Schuttemeyer, D.; Schillings, Ch.; Moene, A.F.; Bruin, de H.A.R.

    2007-01-01

    A simple satellite-based algorithm for estimating actual evaporation based on Makkink¿s equation is applied to a seasonal cycle in 2002 at three test sites in Ghana, West Africa: at a location in the humid tropical southern region and two in the drier northern region. The required input for the algo

  2. Neural Network Based Lna Design for Mobile Satellite Receiver

    Directory of Open Access Journals (Sweden)

    Abhijeet Upadhya

    2014-08-01

    Full Text Available Paper presents a Neural Network Modelling approach to microwave LNA design. To acknowledge the specifications of the amplifier, Mobile Satellite Systems are analyzed. Scattering parameters of the LNA in the frequency range 0.5 to 18 GHz are calculated using a Multilayer Perceptron Artificial Neural Network model and corresponding smith charts and polar charts are plotted as output to the model. From these plots, the microwave scattering parameter description of the LNA are obtained. Model is efficiently trained using Agilent ATF 331M4 InGaAs/InP Low Noise pHEMT amplifier datasheet and the neural model’s output seem to follow the various device characteristic curves with high regression. Next, Maximum Allowable Gain and Noise figure of the device are modelled and plotted for the same frequency range. Finally, the optimized model is utilized as an interpolator and the resolution of the amplifying capability with noise characteristics are obtained for the L Band of MSS operation.

  3. 非结构化道路中基于均质雾天的摄像机动态标定算法%A Dynamic Camera Calibration Algorithm Based on Homogenous Fog in Unstructured Road

    Institute of Scientific and Technical Information of China (English)

    宋洪军; 陈阳舟; 郜园园

    2013-01-01

    现有的交通摄像机标定算法大多基于车道线长度、车辆尺寸等先验信息,由于在非结构化道路中往往不存在车道线,使得标定算法具有局限性.为了改进摄像机标定在非结构化道路中的适用性,结合摄像机线性模型与均质雾天,提出一种只包含路面以及运动车辆的摄像机动态标定算法.首先生成并更新背景和场景活动图,提取路面、天空的纹理特征,利用区域搜索算法得到感兴趣区域,并根据感兴趣区域的像素变化规律判断当前天气是否为均质雾天;其次根据暗原色先验原理计算场景透射率,将结果映射到[0,255]作为图像显示;最后结合均质雾天光线传输模型、摄像机线性模型和暗原色先验原理导出标定方程,选取路面上具有特定透射率的8个点生成2个一次方程、1个二次方程和1个三角方程,依次标定摄像机参数,将视频多帧图像标定的参数值平均得到准确值.与角点检测法、摄像机6点标定法以及基于消失点的标定算法进行对比的实验结果表明,该算法是有效的且满足视频的实时性处理要求.%Most existing traffic camera calibration algorithms work on the basis of lane length,vehicle size prior information; however in unstructured road there are often no traffic lanes.In order to improve the applicability of camera calibration algorithms in unstructured road,a dynamic camera calibration algorithm combining with the camera linear model and homogeneous fog is presented in this paper; this algorithm only contains road surface and moving vehicles.Three main steps are included in the algorithm.Firstly,the algorithm generate and update scenes background and scene activity diagram,extract texture features of the road and sky,search interesting region by the area search algorithm (ASA) and judge whether it is homogeneous fog or not according to the pixel changing form in the interesting region; Secondly,calculate scene

  4. Estimating fog-top height through near-surface micrometeorological measurements

    NARCIS (Netherlands)

    Román-Cascón, Carlos; Yagüe, Carlos; Steeneveld, Gert Jan; Sastre, Mariano; Arrillaga, Jon Ander; Maqueda, Gregorio

    2016-01-01

    Fog-top height (fog thickness) is very useful information for aircraft maneuvers, data assimilation/validation of Numerical Weather Prediction models or nowcasting of fog dissipation. This variable is usually difficult to determine, since the fog-layer top cannot be observed from the surface. In

  5. Extreme haze pollution in Beijing during January 2013: chemical characteristics, formation mechanism and role of fog processing

    Science.gov (United States)

    Huang, K.; Zhuang, G.; Wang, Q.; Fu, J. S.; Lin, Y.; Liu, T.; Han, L.; Deng, C.

    2014-03-01

    Severe haze hovered over large areas of China in January 2013 right after the public release of PM2.5 data of major cities in China at the very first time. This historical severe haze emerged over the northern China with monthly average concentrations of PM2.5, SO2, and NO2 exceeding 225, 200, and 80 μg m-3, respectively. Surface aerosol mean concentration of Beijing in January 2013 reached record high (only slightly lower than 2006) compared to historical data from 2003-2012, but with the largest daily fluctuation. Anomalous meteorological conditions in 2013 compared to the mean climatology from 2007-2012 were especially favorable for the formation of haze, such as higher humidity, lower temperature, lower PBL height, lower wind speed, and the high frequency of fog occurrences. The field campaign in Beijing showed an extremely high PM2.5 average concentration of 299.2 ± 79.1μg m-3 with extremely low visibility of 0.92 ± 0.82 km during an episode of high relative humidity with fog events. High AOD (Aerosol Optical Depth) was observed during fog days but with relatively low Angstrom exponent (relative humidity, suggesting the significant impact of aerosol hygroscopicity on the visibility impairment. SO42- increased ∼5 folds while NO3-, NH4+, and C2O42- increased ∼3 folds in the fog days compared to the non-fog days. Aerosol in fog days was much more acidic than that in non-fog days. The in situ aerosol pH ranged from -0.78 to 0.14 in fog days based on the E-AIM model simulation. Bisulfate (HSO42-) accounted for 52% of the total sulfate and free hydrogen ion (H+Aq) accounted for 27% of the total acids in average. Enhanced coal combustion during the winter heating season along with traffic and industrial emissions were recognized to be the major causes for this severe haze. Fog processing was found to be the major pathway of producing extremely high yields of secondary inorganic aerosol and impacting the neutralization process (i.e. aerosol acidity) in this

  6. Region of Interest Detection Based on Histogram Segmentation for Satellite Image

    Science.gov (United States)

    Kiadtikornthaweeyot, Warinthorn; Tatnall, Adrian R. L.

    2016-06-01

    High resolution satellite imaging is considered as the outstanding applicant to extract the Earth's surface information. Extraction of a feature of an image is very difficult due to having to find the appropriate image segmentation techniques and combine different methods to detect the Region of Interest (ROI) most effectively. This paper proposes techniques to classify objects in the satellite image by using image processing methods on high-resolution satellite images. The systems to identify the ROI focus on forests, urban and agriculture areas. The proposed system is based on histograms of the image to classify objects using thresholding. The thresholding is performed by considering the behaviour of the histogram mapping to a particular region in the satellite image. The proposed model is based on histogram segmentation and morphology techniques. There are five main steps supporting each other; Histogram classification, Histogram segmentation, Morphological dilation, Morphological fill image area and holes and ROI management. The methods to detect the ROI of the satellite images based on histogram classification have been studied, implemented and tested. The algorithm is be able to detect the area of forests, urban and agriculture separately. The image segmentation methods can detect the ROI and reduce the size of the original image by discarding the unnecessary parts.

  7. 基于二代小波的光纤陀螺实时降噪方法研究%Research on real-time de-noising of FOG based on second generation wavelet transform

    Institute of Scientific and Technical Information of China (English)

    高伟; 祖悦; 王伟; 兰海钰; 张亚

    2012-01-01

    In the application of SINS using fiber optic gyroscope (FOG) as the main inertial measurement sensor, the real-time de-noising of the FOG non-deterministic random drift significantly improves the SINS initial alignment and navigation accuracy. Considering the restriction of traditional wavelet de-noising performance and the real-time problem, an improved method for the real-time de-noising of the FOG output signal using the second generation wavelet transform combined with hard threshold, mandatory noise reduction and sliding data window is proposed. Sinusoidal signal and FOG output signal experiments were carried out using MATLAB. Compared with traditional wavelet real-time de-noising performance, the experiment results show that the proposed method can both enhance the de-noising performance and reduce the SINS output attitude error under the premise of great theoretical computing speed increasing.%在以光纤陀螺为主要惯性敏感元件的捷联惯导系统中,陀螺输出信号中的非确定性随机漂移的实时滤除,对提高实际系统的初始对准精度及导航精度均具有重要的意义.考虑到传统小波阈值法的去噪性能及实时性问题,提出了一种基于第二代小波变换,并结合硬阈值、强制降噪和带滑动数据窗的光纤陀螺信号实时降噪改进方案.利用MATLAB进行了正弦信号和光纤陀螺输出信号的模拟实时降噪实验,并与一代小波实时降噪方案进行了比较,验证了改进方案在理论计算速度大幅提升的前提下,降噪性能得到提高,进而减小了系统输出的姿态误差.

  8. Japanese Global Precipitation Measurement (GPM) mission status and application of satellite-based global rainfall map

    Science.gov (United States)

    Kachi, Misako; Shimizu, Shuji; Kubota, Takuji; Yoshida, Naofumi; Oki, Riko; Kojima, Masahiro; Iguchi, Toshio; Nakamura, Kenji

    2010-05-01

    As accuracy of satellite precipitation estimates improves and observation frequency increases, application of those data to societal benefit areas, such as weather forecasts and flood predictions, is expected, in addition to research of precipitation climatology to analyze precipitation systems. There is, however, limitation on single satellite observation in coverage and frequency. Currently, the Global Precipitation Measurement (GPM) mission is scheduled under international collaboration to fulfill various user requirements that cannot be achieved by the single satellite, like the Tropical Rainfall Measurement Mission (TRMM). The GPM mission is an international mission to achieve high-accurate and high-frequent rainfall observation over a global area. GPM is composed of a TRMM-like non-sun-synchronous orbit satellite (GPM core satellite) and constellation of satellites carrying microwave radiometer instruments. The GPM core satellite carries the Dual-frequency Precipitation Radar (DPR), which is being developed by the Japan Aerospace Exploration Agency (JAXA) and the National Institute of Information and Communications Technology (NICT), and microwave radiometer provided by the National Aeronautics and Space Administration (NASA). Development of DPR instrument is in good progress for scheduled launch in 2013, and DPR Critical Design Review has completed in July - September 2009. Constellation satellites, which carry a microwave imager and/or sounder, are planned to be launched around 2013 by each partner agency for its own purpose, and will contribute to extending coverage and increasing frequency. JAXA's future mission, the Global Change Observation Mission (GCOM) - Water (GCOM-W) satellite will be one of constellation satellites. The first generation of GCOM-W satellite is scheduled to be launched in 2011, and it carries the Advanced Microwave Scanning Radiometer 2 (AMSR2), which is being developed based on the experience of the AMSR-E on EOS Aqua satellite

  9. Satellite-based assessment of yield variation and its determinants in smallholder African systems

    Science.gov (United States)

    Lobell, David B.

    2017-01-01

    The emergence of satellite sensors that can routinely observe millions of individual smallholder farms raises possibilities for monitoring and understanding agricultural productivity in many regions of the world. Here we demonstrate the potential to track smallholder maize yield variation in western Kenya, using a combination of 1-m Terra Bella imagery and intensive field sampling on thousands of fields over 2 y. We find that agreement between satellite-based and traditional field survey-based yield estimates depends significantly on the quality of the field-based measures, with agreement highest (R2 up to 0.4) when using precise field measures of plot area and when using larger fields for which rounding errors are smaller. We further show that satellite-based measures are able to detect positive yield responses to fertilizer and hybrid seed inputs and that the inferred responses are statistically indistinguishable from estimates based on survey-based yields. These results suggest that high-resolution satellite imagery can be used to make predictions of smallholder agricultural productivity that are roughly as accurate as the survey-based measures traditionally used in research and policy applications, and they indicate a substantial near-term potential to quickly generate useful datasets on productivity in smallholder systems, even with minimal or no field training data. Such datasets could rapidly accelerate learning about which interventions in smallholder systems have the most positive impact, thus enabling more rapid transformation of rural livelihoods. PMID:28202728

  10. PARTICLE SWARM OPTIMIZATION BASED ON PYRAMID MODEL FOR SATELLITE MODULE LAYOUT

    Institute of Scientific and Technical Information of China (English)

    Zhang Bao; Teng Hongfei

    2005-01-01

    To improve the global search ability of particle swarm optimization (PSO), a multi-population PSO based on pyramid model (PPSO) is presented. Then, it is applied to solve the layout optimization problems against the background of an international commercial communication satellite (INTELSAT-Ⅲ) module. Three improvements are developed, including multi-population search based on pyramid model, adaptive collision avoidance among particles, and mutation of degraded particles. In the numerical examples of the layout design of this simplified satellite module, the performance of PPSO is compared to global version PSO and local version PSO (ring and Neumann PSO). The results show that PPSO has higher computational accuracy, efficiency and success ratio.

  11. A MEMS-based Adaptive AHRS for Marine Satellite Tracking Antenna

    DEFF Research Database (Denmark)

    Wang, Yunlong; Hussain, Dil Muhammed Akbar; Soltani, Mohsen

    2015-01-01

    Satellite tracking is a challenging task for marine applications. An attitude determination system should estimate the wave disturbances on the ship body accurately. To achieve this, an Attitude Heading Reference System (AHRS) based on Micro-Electro-Mechanical Systems (MEMS) sensors, composed...... of three-axis gyroscope, accelerometer and magnetometer, is developed for Marine Satellite Tracking Antenna (MSTA). In this paper, the attitude determination algorithm is improved using an adaptive mechanism that tunes the attitude estimator parameters based on an estimation of ship motion frequency...

  12. Evaluation of satellite soil moisture products over Norway using ground-based observations

    Science.gov (United States)

    Griesfeller, A.; Lahoz, W. A.; Jeu, R. A. M. de; Dorigo, W.; Haugen, L. E.; Svendby, T. M.; Wagner, W.

    2016-03-01

    In this study we evaluate satellite soil moisture products from the advanced SCATterometer (ASCAT) and the Advanced Microwave Scanning Radiometer - Earth Observing System (AMSR-E) over Norway using ground-based observations from the Norwegian water resources and energy directorate. The ASCAT data are produced using the change detection approach of Wagner et al. (1999), and the AMSR-E data are produced using the VUA-NASA algorithm (Owe et al., 2001, 2008). Although satellite and ground-based soil moisture data for Norway have been available for several years, hitherto, such an evaluation has not been performed. This is partly because satellite measurements of soil moisture over Norway are complicated owing to the presence of snow, ice, water bodies, orography, rocks, and a very high coastline-to-area ratio. This work extends the European areas over which satellite soil moisture is validated to the Nordic regions. Owing to the challenging conditions for soil moisture measurements over Norway, the work described in this paper provides a stringent test of the capabilities of satellite sensors to measure soil moisture remotely. We show that the satellite and in situ data agree well, with averaged correlation (R) values of 0.72 and 0.68 for ASCAT descending and ascending data vs in situ data, and 0.64 and 0.52 for AMSR-E descending and ascending data vs in situ data for the summer/autumn season (1 June-15 October), over a period of 3 years (2009-2011). This level of agreement indicates that, generally, the ASCAT and AMSR-E soil moisture products over Norway have high quality, and would be useful for various applications, including land surface monitoring, weather forecasting, hydrological modelling, and climate studies. The increasing emphasis on coupled approaches to study the earth system, including the interactions between the land surface and the atmosphere, will benefit from the availability of validated and improved soil moisture satellite datasets, including those

  13. An ASIFT-Based Local Registration Method for Satellite Imagery

    Directory of Open Access Journals (Sweden)

    Xiangjun Wang

    2015-05-01

    Full Text Available Imagery registration is a fundamental step, which greatly affects later processes in image mosaic, multi-spectral image fusion, digital surface modelling, etc., where the final solution needs blending of pixel information from more than one images. It is highly desired to find a way to identify registration regions among input stereo image pairs with high accuracy, particularly in remote sensing applications in which ground control points (GCPs are not always available, such as in selecting a landing zone on an outer space planet. In this paper, a framework for localization in image registration is developed. It strengthened the local registration accuracy from two aspects: less reprojection error and better feature point distribution. Affine scale-invariant feature transform (ASIFT was used for acquiring feature points and correspondences on the input images. Then, a homography matrix was estimated as the transformation model by an improved random sample consensus (IM-RANSAC algorithm. In order to identify a registration region with a better spatial distribution of feature points, the Euclidean distance between the feature points is applied (named the S criterion. Finally, the parameters of the homography matrix were optimized by the Levenberg–Marquardt (LM algorithm with selective feature points from the chosen registration region. In the experiment section, the Chang’E-2 satellite remote sensing imagery was used for evaluating the performance of the proposed method. The experiment result demonstrates that the proposed method can automatically locate a specific region with high registration accuracy between input images by achieving lower root mean square error (RMSE and better distribution of feature points.

  14. Unmodelled magnetic contributions in satellite-based models

    Science.gov (United States)

    Tozzi, Roberta; Mandea, Mioara; De Michelis, Paola

    2016-06-01

    A complex system of electric currents flowing in the ionosphere and magnetosphere originates from the interaction of the solar wind and the Interplanetary Magnetic Field (IMF) with the Earth's magnetic field. These electric currents generate magnetic fields contributing themselves to those measured by both ground observatories and satellites. Here, low-resolution (1 Hz) magnetic vector data recorded between 1 March 2014 and 31 May 2015 by the recently launched Swarm constellation are considered. The core and crustal magnetic fields and part of that originating in the magnetosphere are removed from Swarm measurements using CHAOS-5 model. Low- and mid-latitude residuals of the geomagnetic field representing the ionospheric and the unmodelled magnetospheric contributions are investigated, in the Solar Magnetic frame, according to the polarity of IMF B y (azimuthal) and B z (north-south) components and to different geomagnetic activity levels. The proposed approach makes it possible to investigate the features of unmodelled contributions due to the external sources of the geomagnetic field. Results show, on one side, the existence of a relation between the analysed residuals and IMF components B y and B z , possibly due to the long distance effect of high-latitude field-aligned currents. On the other side, they suggest the presence of a contribution due to the partial ring current that is activated during the main phase of geomagnetic storms. The perturbation observed on residuals is also compatible with the effect of the net field-aligned currents. Moreover, we have quantitatively estimated the effect of these current systems on computed residuals.

  15. A field investigation and numerical simulation of coastal fog

    Science.gov (United States)

    Mack, E. J.; Eadie, W. J.; Rogers, C. W.; Kocmond, W. C.; Pilie, R. J.

    1973-01-01

    A field investigation of the microphysical and micrometeorological features of fogs occurring near Los Angeles and Vandenberg, California was conducted. Observations of wind speed and direction, temperature, dew point, vertical wind velocity, dew deposition, drop-size distribution, liquid water content, and haze and cloud nucleus concentration were obtained. These observations were initiated in late evening prior to fog formation and continued until the time of dissipation in both advection and radiation fogs. Data were also acquired in one valley fog and several dense haze situations. The behavior of these parameters prior to and during fog are discussed in detail. A two-dimensional numerical model was developed to investigate the formation and dissipation of advection fogs under the influence of horizontal variations in surface temperature. The model predicts the evolution of potential temperature, water vapor content, and liquid water content in a vertical plane as determined by vertical turbulent transfer and horizontal advection. Results are discussed from preliminary numerical experiments on the formation of warm-air advection fog and dissipation by natural and artificial heating from the surface.

  16. Variability and trends of surface solar radiation in Europe based on CM SAF satellite data records

    Science.gov (United States)

    Trentmann, Jörg; Pfeifroth, Uwe; Sanchez-Lorenzo, Arturo; Urbain, Manon; Clerbaux, Nicolas

    2017-04-01

    The EUMETSAT Satellite Application Facility on Climate Monitoring (CM SAF) generates satellite-based high-quality climate data records, with a focus on the global energy and water cycle. Here, the latest releases of the CM SAF's data records of surface solar radiation, Surface Solar Radiation Data Set - Heliosat (SARAH), and CM SAF cLouds, Albedo and Radiation dataset from AVHRR data (CLARA), are analyzed and validated with reference to ground-based measurements, e.g., provided by the Baseline Surface Radiation Network (BSRN), the World Radiation Data Center (WRDC) and the Global Energy Balance Archive (GEBA). Focus is given to the trends and the variability of the surface irradiance in Europe as derived from the surface and the satellite-based data records. Both data sources show an overall increase (i.e., brightening) after the 1980s, and indicate substantial decadal variability with periods of reduced increase (or even a decrease) and periods with a comparable high increase. Also the increase shows a pronounced spatial pattern, which is also found to be consistent between the two data sources. The good correspondence between the satellite-based data records and the surface measurements highlight the potential of the satellite data to represent the variability and changes in the surface irradiance and document the dominant role of clouds over aerosol to explain its variations. Reasons for remaining differences between the satellite- and the surface-based data records (e.g., in Southern Europe) will be discussed. To test the consistency of the CM SAF solar radiation data records we also assess the decadal variability of the solar reflected radiation at the top-of-the atmosphere (TOA) from the CM SAF climate data record based on the MVIRI / SEVIRI measurements from 1983 to 2015. This data record complements the SARAH data record in its temporal and spatial coverage; fewer and different assumptions are used in the retrieval to generate the TOA reflected solar

  17. On the Measurement of Dewfall and Fog-Droplet Deposition

    Science.gov (United States)

    Price, J. D.; Clark, R.

    2014-09-01

    An observational study has been conducted concerning atmospheric dewfall and fog-droplet deposition with application to the formation and maintenance of fog layers. The relationship between dew and fog is discussed together with the challenges and requirements to measure representative values of their deposition to the surface. A practical instrument developed at the UK Met Office Research Unit, Cardington, is described. The instrument is a small portable device that uses a load cell to measure the weight of a pan upon which various types of natural and artificial canopies can be placed, and can measure dewfall and fog-droplet deposition to an accuracy of 0.0005 mm. Dewfall results from this device are shown for a selection of nights under varying conditions. On a given night the overriding factor determining the amount of dew deposition appears to be location. Several dewmeter devices were placed at different locations around the 18 ha Cardington field site for various clear nights and it was found that dew amounts varied significantly, depending on location: canopies with a more open aspect experienced more deposition by up to a factor of two. The results also suggest that the hygroscopic effect of a canopy, whereby water is absorbed into the canopy and topsoil layer before dew formation begins, is also important for the removal of atmospheric water vapour. Results indicate this effect can be of a similar magnitude to dew deposition. Measurements of fog-droplet deposition showed total water deposition rates did not change when thin radiation fog formed. When optically thick adiabatic fog formed, deposition rates were seen to decrease with time or be generally lower than for thinner radiation fog. Further observations are required to establish if the behaviours found are typical for all fogs.

  18. Review on the Analysis and Research of Fog Physicochemical Characteristic Observation

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    [Objective] The research aimed to review the analysis and research on the physicochemical characteristic observation aspect of fog. [Method] To understand the roles of fog microphysical characteristic and chemical reaction on the formation, dissipation, development of fog, the interaction between the microphysical structure, chemical characteristic of fog and the aerosol in the environment, the analysis and research on the micro-physicochemical observation aspect of fog were mainly introduced here. We also ...

  19. Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals

    Directory of Open Access Journals (Sweden)

    Y. Y. Liu

    2010-09-01

    Full Text Available Combining information derived from satellite-based passive and active microwave sensors has the potential to offer improved retrievals of surface soil moisture variations at global scales. Here we propose a technique to take advantage of retrieval characteristics of passive (AMSR-E and active (ASCAT microwave satellite estimates over sparse-to-moderately vegetated areas to obtain an improved soil moisture product. To do this, absolute soil moisture values from AMSR-E and relative soil moisture derived from ASCAT are rescaled against a reference land surface model date set using a cumulative distribution function (CDF matching approach. While this technique imposes the bias of the reference to the rescaled satellite products, it adjusts both satellite products to the same range and almost preserves the correlation between satellite products and in situ measurements. Comparisons with in situ data demonstrated that over the regions where the correlation coefficient between rescaled AMSR-E and ASCAT is above 0.65 (hereafter referred to as transitional regions, merging the different satellite products together increases the number of observations while minimally changing the accuracy of soil moisture retrievals. These transitional regions also delineate the boundary between sparsely and moderately vegetated regions where rescaled AMSR-E and ASCAT are respectively used in the merged product. Thus the merged product carries the advantages of better spatial coverage overall and increased number of observations particularly for the transitional regions. The combination approach developed in this study has the potential to be applied to existing microwave satellites as well as to new microwave missions. Accordingly, a long-term global soil moisture dataset can be developed and extended, enhancing basic understanding of the role of soil moisture in the water, energy and carbon cycles.

  20. Continental Fog Attenuation Empirical Relationship from Measured Visibility Data

    Directory of Open Access Journals (Sweden)

    F. Nadeem

    2010-12-01

    Full Text Available Free Space Optics (FSO has the great potential for future communication applications. However, weather influenced reduced availability had been the main cause for its restricted growth. Among different weather influences fog plays the major role. A new model generalized for all FSO wavelengths, has been proposed for the prediction of continental fog attenuation using visibility data. The performance of the proposed model has been compared with well known models for measured attenuation data of Continental fog. The comparison has been performed in terms of Root Mean Square Error (RMSE.

  1. A Girl in the Fog(习作)

    Institute of Scientific and Technical Information of China (English)

    周水霞

    2000-01-01

    It's a fresh morning, somewhat full of fog.The white fog is not heavy, but it fills the whole morning, the whole world, even the whole heart of the slim girl. She is wandering through the vague fog, holding some thick books in her slim arms near her chest. Her step is slow and shaky. She seems not to be thinking. Only her two bright eyes, which seem to be full of little tears, are saying her helplessness, her loss, her despair, her depression and all her disappointment. The foggy world makes her feel them m...

  2. Extreme fog events in Poland with respect to circulation conditions

    Science.gov (United States)

    Ustrnul, Z.; Czekierda, D.; Wypych, A.

    2010-09-01

    Fog is a phenomenon which belongs to a group of so-called hydrometeorites and, according to the different dictionaries, it is a suspension of water droplets or ice crystals in the ground layer of the air that impairs visibility in the horizontal direction below 1 km. The phenomenon of fog, although much less dynamic or violent than other extreme phenomena, such as thunderstorms or hail, is equally dangerous and brings about huge social and economic complications. Land and air transportation suffer and fog may sometimes leads to a complete crippling of the whole economy in an area where fog occurs. The main objective of the study is determination of the circulation types bringing extreme fog events in Poland. The duration of fog at each meteorological station was considered as the main input data originated from 54 synoptic stations located across the country. The mentioned data series cover the period of 56 years (1951-2006). The occurrence of fog depends on meteorological conditions caused to a large extent by a given synoptic situation and local terrain conditions. In this study, according to its objectives, only circulation conditions are taken into consideration. These have been described by 5 different circulation classifications (Grosswetterlagen, Litynski, Osuchowska-Klein, Niedzwiedz and Ustrnul). Situations when this phenomenon occurred across a large part of the country were taken into detailed consideration. Special attention was paid to fog coverage during 24-hour periods. In this work, in light of certain doubts about the homogeneity of the observation material available, the intensity of fog was not included, as it requires additional and very tedious analysis. In the first step all cases of fog during the 1966-2006 study period which lasted 24 hours at more than 10 of the considered weather stations, i.e: at least 5 stations have been considered. As expected, in most cases, either a centre of a classical high pressure system or a high pressure wedge

  3. Fog water chemical composition in different geographic regions of Poland

    Science.gov (United States)

    Błaś, Marek; Polkowska, Żaneta; Sobik, Mieczysław; Klimaszewska, Kamila; Nowiński, Kamil; Namieśnik, Jacek

    2010-03-01

    The fog water samples were collected with the use of both passive and active fog collectors during 2005-2006 at 3 sites: lowland in northern Poland (Borucino; 186 m a.s.l.), valley basin in southern Poland (Zakopane; 911 m a.s.l.) and mountain top (Szrenica Mt.; 1330 m a.s.l.) in south-western Poland. For all daily samples (Borucino—25; Zakopane—4 and Szrenica—155), electric conductivity, pH, and concentrations of some anions: Cl -, F -, Br -, NO 2-, NO 3-, SO 42-, PO 43-and cations: NH 4+, Ca 2+, K +, Na + and Mg 2+ were measured. The selected ions were determined using ion suppressed chromatography (IC). Fog consists of a specific type of atmospheric phenomena. Results obtained on the basis of analysis of suitable fog samples can be treated as a source of valuable information on the chemistry of the atmosphere. Statistical analysis revealed significant differences depending on region, altitude, local morphology and, last but not least, fog origin. A distinct contrast is evident in the concentration and chemical composition between lowland radiation fog (represents lower layers of the atmosphere which are more influenced by continental emissions) versus orographic slope fog represented by a summit station, Mt Szrenica. It is partly induced by a distinction in weather conditions favouring fog existence, height of fog formation and its microphysical parameters. Acidity was associated with high concentrations of excess sulphate and nitrate in the fog water samples. Ammonium and calcium concentrations represent the most important neutralizing inputs. Collected cloud water at Szrenica Mt. includes solute contributions from emission sources located at much larger upwind distances. The fact that 95% of fog/cloud deposition is concentrated during SW-W-NW-N-NE, atmospheric circulation exerts an influence on the environmental quality of montane forests in the Sudety Mts. At numerous conspicuous convex landforms, where fog/cloud deposition becomes at least as important

  4. Combined effects of organic aerosol loading and fog processing on organic aerosols oxidation and composition

    Science.gov (United States)

    Chakraborty, Abhishek; Tripathi, Sachchida; Gupta, Tarun

    2016-04-01

    seemed to be reducing the negative impact of OA loading on O/C ratio via oxidation through aqueous processing. Average O/C ratio difference between HL and LL period during no-fog condition is 0.13 while it is reduced to 0.06 during foggy condition. This indicates that fog processing to an extent negating the OA loading impact on O/C ratio. This is happening due to the fact that aqueous oxidation efficiency doesn't depend on OA loading but on fog LWC (liquid water content), RH, NOx and presence/absence of transition metals. These findings indicate that only aerosol volatility based approach to predict particle phase concentration, composition and oxidation ratio of organics may result in some misleading outcome.

  5. Motivating Students to Develop Satellites in a Problem and Project-Based Learning Environment

    DEFF Research Database (Denmark)

    Larsen, Jesper Abildgaard; Nielsen, Jens Frederik Dalsgaard; Zhou, Chunfang

    2013-01-01

    During the last decade, a total of three student satellites have been developed by engineering students in a Problem and Project-Based Learning (PBL) environment at Aalborg University (AAU), Denmark. As solving such a complex project, we emphasize that a high level of motivation is needed...... satellite projects in a PBL environment. Empirically, a total of 12 student participants were interviewed. The results show that students’ motivation is highly stimulated by the project management with a series of factors, such as the task characteristics, support of peers, help of supervisors, and openness...

  6. Research of Multi-Agent System based satellite fault diagnosis technology

    Institute of Scientific and Technical Information of China (English)

    范显峰; 姜兴渭; 黄文虎; 谷吉海

    2002-01-01

    Following the theory of Multi-Agent System (MAS) and using series-wound structure and shunt-wound structure of Agents, the performance of Agent was improved to satisfy the need of satellite fault diagno-sis, and a tridimensional MAS model of satellite fault diagnosis was thus established for the MAS based planardiagnosis system, which decentralizes the whole diagnosing task into subtasks to be performed by different func-tional Agents to make the complicated fault diagnosis very simple and the diagnosis system more intelligent.This method improved the reliability and accuracy of diagnosis and made the maintenance and upgrading of thesatellite fault diagnosis system very easy as well.

  7. Evaluation of Clear Sky Models for Satellite-Based Irradiance Estimates

    Energy Technology Data Exchange (ETDEWEB)

    Sengupta, M.; Gotseff, P.

    2013-12-01

    This report describes an intercomparison of three popular broadband clear sky solar irradiance model results with measured data, as well as satellite-based model clear sky results compared to measured clear sky data. The authors conclude that one of the popular clear sky models (the Bird clear sky model developed by Richard Bird and Roland Hulstrom) could serve as a more accurate replacement for current satellite-model clear sky estimations. Additionally, the analysis of the model results with respect to model input parameters indicates that rather than climatological, annual, or monthly mean input data, higher-time-resolution input parameters improve the general clear sky model performance.

  8. Satellite-based empirical models linking river plume dynamics with hypoxic area andvolume

    Science.gov (United States)

    Satellite-based empirical models explaining hypoxic area and volume variation were developed for the seasonally hypoxic (O2 < 2 mg L−1) northern Gulf of Mexico adjacent to the Mississippi River. Annual variations in midsummer hypoxic area and ...

  9. Efficient GOCE satellite gravity field recovery based on least-squares using QR decomposition

    NARCIS (Netherlands)

    Baur, O.; Austen, G.; Kusche, J.

    2007-01-01

    We develop and apply an efficient strategy for Earth gravity field recovery from satellite gravity gradiometry data. Our approach is based upon the Paige-Saunders iterative least-squares method using QR decomposition (LSQR). We modify the original algorithm for space-geodetic applications: firstly,

  10. MISAT : Designing a Series of Powerful Small Satellites Based upon Micro Systems Technology

    NARCIS (Netherlands)

    Gill, E.; Monna, G.L.E.; Scherpen, J.M.A.; Verhoeven, C.J.M.

    2007-01-01

    MISAT is a research and development cluster which will create a small satellite platform based on Micro Systems Technology (MST) aiming at innovative space as well as terrestrial applications. MISAT is part of the Dutch MicroNed program which has established a microsystems infrastructure to fully

  11. MISAT : Designing a Series of Powerful Small Satellites Based upon Micro Systems Technology

    NARCIS (Netherlands)

    Gill, E.; Monna, G.L.E.; Scherpen, J.M.A.; Verhoeven, C.J.M.

    2007-01-01

    MISAT is a research and development cluster which will create a small satellite platform based on Micro Systems Technology (MST) aiming at innovative space as well as terrestrial applications. MISAT is part of the Dutch MicroNed program which has established a microsystems infrastructure to fully ex

  12. Autonomous Sub-Pixel Satellite Track Endpoint Determination for Space Based Images

    Energy Technology Data Exchange (ETDEWEB)

    Simms, L M

    2011-03-07

    An algorithm for determining satellite track endpoints with sub-pixel resolution in spaced-based images is presented. The algorithm allows for significant curvature in the imaged track due to rotation of the spacecraft capturing the image. The motivation behind the subpixel endpoint determination is first presented, followed by a description of the methodology used. Results from running the algorithm on real ground-based and simulated spaced-based images are shown to highlight its effectiveness.

  13. THE SATELLITE STRUCTURE TOPOLOGY OPTIMIZATION BASED ON HOMOGENIZATION METHOD AND ITS SIZE SENSITIVITY ANALYSIS

    Institute of Scientific and Technical Information of China (English)

    ChenChangya; PanJin; WangDeyu

    2005-01-01

    With the development of satellite structure technology, more and more design parameters will affect its structural performance. It is desirable to obtain an optimal structure design with a minimum weight, including optimal configuration and sizes. The present paper aims to describe an optimization analysis for a satellite structure, including topology optimization and size optimization. Based on the homogenization method, the topology optimization is carried out for the main supporting frame of service module under given constraints and load conditions, and then the sensitivity analysis is made of 15 structural size parameters of the whole satellite and the optimal sizes are obtained. The numerical result shows that the present optimization design method is very effective.

  14. Protocol Support for a New Satellite-Based Airspace Communication Network

    Science.gov (United States)

    Shang, Yadong; Hadjitheodosiou, Michael; Baras, John

    2004-01-01

    We recommend suitable transport protocols for an aeronautical network supporting Internet and data services via satellite. We study the characteristics of an aeronautical satellite hybrid network and focus on the problems that cause dramatically degraded performance of the Transport Protocol. We discuss various extensions to standard TCP that alleviate some of these performance problems. Through simulation, we identify those TCP implementations that can be expected to perform well. Based on the observation that it is difficult for an end-to-end solution to solve these problems effectively, we propose a new TCP-splitting protocol, termed Aeronautical Transport Control Protocol (AeroTCP). The main idea of this protocol is to use a fixed window for flow control and one duplicated acknowledgement (ACK) for fast recovery. Our simulation results show that AeroTCP can maintain higher utilization for the satellite link than end-to-end TCP, especially in high BER environment.

  15. Satellites vs. fiber optics based networks and services - Road map to strategic planning

    Science.gov (United States)

    Marandi, James H. R.

    An overview of a generic telecommunications network and its components is presented, and the current developments in satellite and fiber optics technologies are discussed with an eye on the trends in industry. A baseline model is proposed, and a cost comparison of fiber- vs satellite-based networks is made. A step-by-step 'road map' to the successful strategic planning of telecommunications services and facilities is presented. This road map provides for optimization of the current and future networks and services through effective utilization of both satellites and fiber optics. The road map is then applied to different segments of the telecommunications industry and market place, to show its effectiveness for the strategic planning of executives of three types: (1) those heading telecommunications manufacturing concerns, (2) those leading communication service companies, and (3) managers of telecommunication/MIS departments of major corporations. Future networking issues, such as developments in integrated-services digital network standards and technologies, are addressed.

  16. Deep Learning-Based Large-Scale Automatic Satellite Crosswalk Classification

    Science.gov (United States)

    Berriel, Rodrigo F.; Lopes, Andre Teixeira; de Souza, Alberto F.; Oliveira-Santos, Thiago

    2017-09-01

    High-resolution satellite imagery have been increasingly used on remote sensing classification problems. One of the main factors is the availability of this kind of data. Even though, very little effort has been placed on the zebra crossing classification problem. In this letter, crowdsourcing systems are exploited in order to enable the automatic acquisition and annotation of a large-scale satellite imagery database for crosswalks related tasks. Then, this dataset is used to train deep-learning-based models in order to accurately classify satellite images that contains or not zebra crossings. A novel dataset with more than 240,000 images from 3 continents, 9 countries and more than 20 cities was used in the experiments. Experimental results showed that freely available crowdsourcing data can be used to accurately (97.11%) train robust models to perform crosswalk classification on a global scale.

  17. Multi-Objective Reinforcement Learning for Cognitive Radio-Based Satellite Communications

    Science.gov (United States)

    Ferreira, Paulo Victor R.; Paffenroth, Randy; Wyglinski, Alexander M.; Hackett, Timothy M.; Bilen, Sven G.; Reinhart, Richard C.; Mortensen, Dale J.

    2016-01-01

    Previous research on cognitive radios has addressed the performance of various machine-learning and optimization techniques for decision making of terrestrial link properties. In this paper, we present our recent investigations with respect to reinforcement learning that potentially can be employed by future cognitive radios installed onboard satellite communications systems specifically tasked with radio resource management. This work analyzes the performance of learning, reasoning, and decision making while considering multiple objectives for time-varying communications channels, as well as different cross-layer requirements. Based on the urgent demand for increased bandwidth, which is being addressed by the next generation of high-throughput satellites, the performance of cognitive radio is assessed considering links between a geostationary satellite and a fixed ground station operating at Ka-band (26 GHz). Simulation results show multiple objective performance improvements of more than 3.5 times for clear sky conditions and 6.8 times for rain conditions.

  18. A Handover Strategy in the LEO Satellite-Based Constellation Networks with ISLs

    Institute of Scientific and Technical Information of China (English)

    LIU Gang; GOU Dingyong; WU Shiqi

    2003-01-01

    A new handover strategy named minimal-hops handover(MHH) strategy for the low earth orbit(LEO) satellite constellations networks equipped with inter-satellite links(ISLs) is proposed.MHH strategy, which is based on the hops of the end-to-end connection paths and makes good use of the regularity of the constellation network topology, can appropriately combine the handover procedure with routing and efficiently solve the inter-satellite handover issue. Moreover, MHH strategy can provide quality of services( QoS) guarantees to some extent. The system performances of the MHH strategy, such as time propagation delay and handover frequency, are evaluated and compared with that of other previous strategies. The simulation results show that MHH strategy performs better than other previous handover strategies.

  19. Satellite-based annual evaporation estimates of invasive alien plant ...

    African Journals Online (AJOL)

    2013-12-17

    Dec 17, 2013 ... Water (WFW) programme, have on total evaporation (ET) and the availability of water resources in two highly-invaded ... on water resources were based on the results from the paired catchment ...... Tourism, Pretoria. 85 pp.

  20. A Review on Modern Distributed Computing Paradigms: Cloud Computing, Jungle Computing and Fog Computing

    OpenAIRE

    Hajibaba, Majid; Gorgin, Saeid

    2014-01-01

    The distributed computing attempts to improve performance in large-scale computing problems by resource sharing. Moreover, rising low-cost computing power coupled with advances in communications/networking and the advent of big data, now enables new distributed computing paradigms such as Cloud, Jungle and Fog computing.Cloud computing brings a number of advantages to consumers in terms of accessibility and elasticity. It is based on centralization of resources that possess huge processing po...

  1. Developing an improved soil moisture dataset by blending passive and active microwave satellite-based retrievals

    Directory of Open Access Journals (Sweden)

    Y. Y. Liu

    2011-02-01

    Full Text Available Combining information derived from satellite-based passive and active microwave sensors has the potential to offer improved estimates of surface soil moisture at global scale. We develop and evaluate a methodology that takes advantage of the retrieval characteristics of passive (AMSR-E and active (ASCAT microwave satellite estimates to produce an improved soil moisture product. First, volumetric soil water content (m3 m−3 from AMSR-E and degree of saturation (% from ASCAT are rescaled against a reference land surface model data set using a cumulative distribution function matching approach. While this imposes any bias of the reference on the rescaled satellite products, it adjusts them to the same range and preserves the dynamics of original satellite-based products. Comparison with in situ measurements demonstrates that where the correlation coefficient between rescaled AMSR-E and ASCAT is greater than 0.65 ("transitional regions", merging the different satellite products increases the number of observations while minimally changing the accuracy of soil moisture retrievals. These transitional regions also delineate the boundary between sparsely and moderately vegetated regions where rescaled AMSR-E and ASCAT, respectively, are used for the merged product. Therefore the merged product carries the advantages of better spatial coverage overall and increased number of observations, particularly for the transitional regions. The combination method developed has the potential to be applied to existing microwave satellites as well as to new missions. Accordingly, a long-term global soil moisture dataset can be developed and extended, enhancing basic understanding of the role of soil moisture in the water, energy and carbon cycles.

  2. Using Coastal Fog to Support Sustainable Water Use in a California Agricultural System

    Science.gov (United States)

    Baguskas, S. A.; Loik, M. E.

    2015-12-01

    Impacts of climate change threaten California farmers in a number of ways, most importantly through a decline in freshwater availability, concurrent with a rise in water demand. The future of California's multibillion-dollar agricultural industry depends on increasing water use efficiency on farms. In coastal California, the growing season of economically important crops overlaps with the occurrence of coastal fog, which buffers the summer dry season through shading effects and direct water inputs. While the impacts of coastal fog on plant biology have been extensively studied in natural ecosystems, very few studies have evaluated its direct effects on the water and energy budgets of agricultural systems. The objective of this study was to develop a mechanistic understanding of the relationships between coastal fog and the water and energy budgets of croplands in order to improve estimates of crop-scale evapotranspiration rates, which has potential to curtail groundwater use based on local cloud meteorology. We established three sites on strawberry farms along a coastal-inland gradient in the Salinas Valley, California. At each site, we installed a passive fog collector and a micrometeorological station to monitor variation in microclimate conditions. Flow meters were installed in drip lines to quantify irrigation amount and timing. To assess plant response to foggy and non-foggy conditions, we collected measurements of photosynthesis and transpiration rates at the leaf and canopy-scale between June-September 2015. We found that canopy-level transpiration rates on foggy days were reduced by half compared to sunny, clear days (1.5 and 3 mmol H2O m-2 s-1, respectively). Whereas the amount of direct fog water inputs to the soil did not differ significantly between foggy and clear days, average photosynthetically active radiation between 0900-1100 hr. was reduced from 1500 to 500 μmol photons m-2 s-1 between these sampling periods. Our results provide convincing

  3. Bias adjustment of satellite-based precipitation estimation using gauge observations: A case study in Chile

    Science.gov (United States)

    Yang, Zhongwen; Hsu, Kuolin; Sorooshian, Soroosh; Xu, Xinyi; Braithwaite, Dan; Verbist, Koen M. J.

    2016-04-01

    Satellite-based precipitation estimates (SPEs) are promising alternative precipitation data for climatic and hydrological applications, especially for regions where ground-based observations are limited. However, existing satellite-based rainfall estimations are subject to systematic biases. This study aims to adjust the biases in the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks-Cloud Classification System (PERSIANN-CCS) rainfall data over Chile, using gauge observations as reference. A novel bias adjustment framework, termed QM-GW, is proposed based on the nonparametric quantile mapping approach and a Gaussian weighting interpolation scheme. The PERSIANN-CCS precipitation estimates (daily, 0.04°×0.04°) over Chile are adjusted for the period of 2009-2014. The historical data (satellite and gauge) for 2009-2013 are used to calibrate the methodology; nonparametric cumulative distribution functions of satellite and gauge observations are estimated at every 1°×1° box region. One year (2014) of gauge data was used for validation. The results show that the biases of the PERSIANN-CCS precipitation data are effectively reduced. The spatial patterns of adjusted satellite rainfall show high consistency to the gauge observations, with reduced root-mean-square errors and mean biases. The systematic biases of the PERSIANN-CCS precipitation time series, at both monthly and daily scales, are removed. The extended validation also verifies that the proposed approach can be applied to adjust SPEs into the future, without further need for ground-based measurements. This study serves as a valuable reference for the bias adjustment of existing SPEs using gauge observations worldwide.

  4. PLAM - a meteorological pollution index for air quality and its applications in fog-haze forecasts in North China

    Science.gov (United States)

    Yang, Y. Q.; Wang, J. Z.; Gong, S. L.; Zhang, X. Y.; Wang, H.; Wang, Y. Q.; Wang, J.; Li, D.; Guo, J. P.

    2016-02-01

    Using surface meteorological observation and high-resolution emission data, this paper discusses the application of the PLAM/h index (Parameter Linking Air-quality to Meteorological conditions/haze) in the prediction of large-scale low visibility and fog-haze events. Based on the two-dimensional probability density function diagnosis model for emissions, the study extends the diagnosis and prediction of the meteorological pollution index PLAM to the regional visibility fog-haze intensity. The results show that combining the influence of regular meteorological conditions and emission factors together in the PLAM/h parameterization scheme is very effective in improving the diagnostic identification ability of the fog-haze weather in North China. The determination coefficients for four seasons (spring, summer, autumn, and winter) between PLAM/h and visibility observation are 0.76, 0.80, 0.96, and 0.86, respectively, and all of their significance levels exceed 0.001, showing the ability of PLAM/h to predict the seasonal changes and differences of fog-haze weather in the North China region. The high-value correlation zones are located in Jing-Jin-Ji (Beijing, Tianjin, Hebei), Bohai Bay rim, and southern Hebei-northern Henan, indicating that the PLAM/h index is related to the distribution of frequent heavy fog-haze weather in North China and the distribution of emission high-value zone. Through comparative analysis of the heavy fog-haze events and large-scale clear-weather processes in winter and summer, it is found that PLAM/h index 24 h forecast is highly correlated with the visibility observation. Therefore, the PLAM/h index has good capability in identification, analysis, and forecasting.

  5. Interannual increase of regional haze-fog in North China Plain in summer by intensified easterly winds and orographic forcing

    Science.gov (United States)

    Cao, Ziqi; Sheng, Lifang; Liu, Qian; Yao, Xiaohong; Wang, Wencai

    2015-12-01

    Regional haze-fog events over the North China Plain (NCP) have attracted much attention in recent years. Their increase has been attributed to anthropogenic emissions of air pollutants and synoptic weather conditions. We investigated the influence of local meteorological conditions and large-scale circulation on the haze-fog events over the NCP during 2001-2012, and found a significant interannual increase in the number of summer regional haze-fog days. Analysis indicated that local meteorological conditions could partly explain the increase but failed to explain the spatial variation; meanwhile, regional circulation change induced by large-scale circulation and orographic forcing unveiled a possible spatiotemporal variation mechanism. In summer, the prevalent southerly winds over the NCP were obstructed by the Taihang and Yanshan mountains, steadying the outflow direction to the southeast, while different inflow direction controlled by large-scale circulation had different effects on regional circulation. In weak (strong) East Asian summer monsoon years, an intensified eastward (westward) zonal inflow wind component reinforced (weakened) the negative vorticity and formed an anomalous anticyclone (cyclone), which strengthened (weakened) the downward motion, so the dissipation capability was weakened (strengthened) and the wind speed decreased (increased), ultimately resulting in the increased (decreased) occurrence of haze-fog. We also found that the circulation anomaly had a good relationship with strong El Niño and La Niña events. There was more haze-fog over the NCP in the summers that followed a La Niña event, and less in summers that followed an El Niño event. This suggested the possibility that summer haze-fog phenomena could be predicted based on the phase of ENSO.

  6. Evaluation of Satellite and Ground Based Precipitation Products for Flood Forecasting

    Science.gov (United States)

    Chintalapudi, S.; Sharif, H.; Yeggina, S.

    2012-04-01

    The development in satellite-derived rainfall estimates encouraged the hydrological modeling in sparse gauged basins or ungauged basins. Especially, physically-based distributed hydrological models can benefit from the good spatial and temporal coverage of satellite precipitation products. In this study, three satellite derived precipitation datasets (TRMM, CMORPH, and PERSIANN), NEXRAD, and rain gauge precipitation datasets were used to drive the hydrological model. The physically-based, distributed hydrological model Gridded Surface Subsurface Hydrological Analysis (GSSHA) was used in this study. Focus will be on the results from the Guadalupe River Basin above Canyon Lake and below Comfort, Texas. The Guadalupe River Basin above Canyon Lake and below Comfort Texas drains an area of 1232 km2. Different storm events will be used in these simulations. August 2007 event was used as calibration and June 2007 event was used as validation. Results are discussed interms of accuracy of satellite precipitation estimates with the ground based precipitation estimates, predicting peak discharges, runoff volumes, time lag, and spatial distribution. The initial results showed that, model was able to predict the peak discharges and runoff volumes when using NEXRAD MPE data, and TRMM 3B42 precipitation product. The results also showed that there was time lag in hydrographs driven by both PERSIANN and CMORPH data sets.

  7. Research Methods on Cloud and Fog Removal Processing of Remote Sensing Images%遥感图像薄云薄雾的去除处理方法

    Institute of Scientific and Technical Information of China (English)

    王敏; 周树道; 刘志华; 黄峰; 梁妙元

    2011-01-01

    Image processing research on cloud and fog removing has become a hot research topic of computer vision. At present,there are many algorithms for cloud and fog removal presented by domestic and international scholars. This article analyzed the influence of the cloud and fog to the image, and summary to the references, then introduced respectively the main principle and research of various existing cloud and fog removal methods, including fog removing methods based on physical model and image processing, multispectral cloud removing, image fusion cloud removing and homomorphic filter cloud removing. Also it discussed the advantage and limit of the processing algorithm. Finally, an outlook to the cloud and fog removing image processing methods was carried on.%分析云雾对图像的影响,对相关文献进行了分析总结,分别介绍了现有的各种薄云薄雾去除方法的主要原理及研究现状等,包括有基于物理模型和基于图像处理的薄雾去除方法,光谱图像去云、图像融合去云、同态滤波去云方法,并讨论了各处理方法的优势及局限.最后,对云雾去除图像处理方法进行了展望.

  8. Towards a medium-range coastal station fog forecasting system

    CSIR Research Space (South Africa)

    Landman, S

    2013-09-01

    Full Text Available An empirical downscaling technique to predict daily fog occurrence at Cape Town International Airport from low-level atmospheric circulation is developed by using the Principal Component Regression option of the Climate Predictability Tool. NCEP 12...

  9. Satellite-based estimation of rainfall erosivity for Africa

    NARCIS (Netherlands)

    Vrieling, A.; Sterk, G.; Jong, S.M. de

    2010-01-01

    Rainfall erosivity is a measure for the erosive force of rainfall. Rainfall kinetic energy determines the erosivity and is in turn greatly dependent on rainfall intensity. Attempts for its large-scale mapping are rare. Most are based on interpolation of erosivity values derived from rain gauge data.

  10. Linear and Nonlinear Relative Navigation Strategies for Small Satellite Formation Flying Based on Relative Position Measurement

    Science.gov (United States)

    Zhang, Xiaomin; Zheng, You

    Based on linear and nonlinear mathematical model of spacecraft formation flying and technology of relative position measurement of small satellites, the linear and nonlinear relative navigation strategies are developed in this paper. The dynamical characteristics of multi spacecraft formation flying have been researched in many references, including the authors' several International Astronautical Congress papers with numbers of IAF-98-A.2.06, IAA-99-IAA.11.1.09, IAA-01-IAA.11.4.08. Under conditions of short distance and short time, the linear model can describe relative orbit motion; otherwise, nonlinear model must be adopted. Furthermore the means of measurement and their error will influence relative navigation. Thus three kinds of relative navigation strategy are progressed. With consideration of difficulty in relative velocity measurement of small satellites, the three relative navigation strategies are proposed and only depend on sequential data of relative position through measuring the relative distance and relative orientation. The first kind of relative navigation strategy is based on linear model. The second relative navigation strategy is based on nonlinear model, with inclusion of the second order item. In fact the measurement error can not be avoided especially for small satellites, it is mainly considered in the third relative navigation strategy. This research is theoretical yet and a series of formulas of relative navigation are presented in this paper. Also the authors analyzed the three strategies qualitatively and quantitatively. According to results of simulation, the ranges of application are indicated and suggested in allusion to the three strategies of relative navigation. On the view of authors, the relative navigation strategies for small satellite formation flying based on relative position measurement are significant for engineering of small satellite formation flying.

  11. Detecting weather radar clutter using satellite-based nowcasting products

    DEFF Research Database (Denmark)

    Jensen, Thomas B.S.; Gill, Rashpal S.; Overgaard, Søren

    2006-01-01

    for the detecting and removal of clutter. Naturally, the improved spatio-temporal resolution of the Meteosat Second Generation sensors, coupled with its increased number of spectral bands, is expected to yield even better detection accuracies. Weather radar data from three C-band Doppler weather radars...... Application Facility' of EUMETSAT and is based on multispectral images from the SEVIRI sensor of the Meteosat-8 platform. Of special interest is the 'Precipitating Clouds' product, which uses the spectral information coupled with surface temperatures from Numerical Weather Predictions to assign probabilities...... by the resolution of the radar data. Subsequently, a supervised classifier was developed based on training data selected by a weather radar expert. Results of classification of data from several different meteorological events are shown. Cases of widespread sea clutter caused by anomalous propagation are especially...

  12. Studies of oceanic tectonics based on GEOS-3 satellite altimetry

    Science.gov (United States)

    Poehls, K. A.; Kaula, W. M.; Schubert, G.; Sandwell, D.

    1979-01-01

    Using statistical analysis, geoidal admittance (the relationship between the ocean geoid and seafloor topography) obtained from GEOS-3 altimetry was compared to various model admittances. Analysis of several altimetry tracks in the Pacific Ocean demonstrated a low coherence between altimetry and seafloor topography except where the track crosses active or recent tectonic features. However, global statistical studies using the much larger data base of all available gravimetry showed a positive correlation of oceanic gravity with topography. The oceanic lithosphere was modeled by simultaneously inverting surface wave dispersion, topography, and gravity data. Efforts to incorporate geoid data into the inversion showed that the base of the subchannel can be better resolved with geoid rather than gravity data. Thermomechanical models of seafloor spreading taking into account differing plate velocities, heat source distributions, and rock rheologies were discussed.

  13. Scalable distributed computing hierarchy: cloud, fog and dew computing

    OpenAIRE

    Skala, Karolj; Davidović, Davor; Afgan, Enis; Sović, Ivan; Šojat, Zorislav

    2015-01-01

    The paper considers the conceptual approach for organization of the vertical hierarchical links between the scalable distributed computing paradigms: Cloud Computing, Fog Computing and Dew Computing. In this paper, the Dew Computing is described and recognized as a new structural layer in the existing distributed computing hierarchy. In the existing computing hierarchy, the Dew computing is positioned as the ground level for the Cloud and Fog computing paradigms. Vertical, complementary, hier...

  14. Fog Computing: Focusing on Mobile Users at the Edge

    OpenAIRE

    Luan, Tom H.; Gao, Longxiang; Li, Zhi; XIANG, YANG; Wei, Guiyi; Sun, Limin

    2015-01-01

    With smart devices, particular smartphones, becoming our everyday companions, the ubiquitous mobile Internet and computing applications pervade people daily lives. With the surge demand on high-quality mobile services at anywhere, how to address the ubiquitous user demand and accommodate the explosive growth of mobile traffics is the key issue of the next generation mobile networks. The Fog computing is a promising solution towards this goal. Fog computing extends cloud computing by providing...

  15. The influence of fog on car following distance

    OpenAIRE

    Cavallo, V.; BEAUDOIN, E; de Boer, E

    2004-01-01

    The hypothesis of distance misperception in fog has recently been corroborated by a series of fog chamber studies (Cavallo et al., 2000), showing an overestimation of 30-60 % of vehicle distance in foggy conditions, when the vehicle lights but not its outline remained visible. To validate these findings in a more ecological setting, we studied the control of following distance in a driving simulator experiment. Results revealed shorter following distances in all foggy conditions, irrespective...

  16. Vertical profile of fog microphysics : a case study

    Science.gov (United States)

    Burnet, Frédéric; Brilouet, Pierre-Etienne; Mazoyer, Marie; Bourrianne, Thierry; Etcheberry, Jean-Michel; Gaillard, Brigitte; Legain, Dominique; Tzanos, Diane; Barrié, Joel; Barrau, Sébastien; Defoy, Stephan

    2016-04-01

    The occurrence and development of fogs result from the non-linear interaction of competing radiative, thermodynamic, microphysical and dynamical processes and the forecasting of their life cycle still remains a challenging issue. Several field campaigns have been carried out at the SIRTA observatory in the Paris suburb area (France). These experiments have shown that fog events exhibit large differences of the microphysical properties and various evolutions during their life cycle. To better understand relationships between the different processes and to validate numerical simulations it is necessary however to document the vertical profile of the fog microphysics. A CDP (Cloud Droplet Spectrometer) from DMT (Droplet Measurement Technology, Boulder, CO) has been modified to allow measurements of the droplet size distribution in fog layers with a tethered balloon. This instrumental set-up has been used during a field campaign during the winter 2013-214 in the Landes area in the South West of France. To validate the vertical profiles provided by the modified CDP, a mast was equipped with microphysical instruments at 2 altitude levels with an another CDP at 24 m and a Fog Monitor FM100 at 42 m. The instrumental set-up deployed during this campaign is presented. Data collected during a fog event that occurred during the night of 5-6 March 2014 are analysed. We show that microphysical properties such as droplet number concentration, LWC and mean droplet size, exhibit different time evolution during the fog life cycle depending on the altitude level. Droplet size distribution measurements are also investigated. They reveal sharp variations along the vertical close to the top of the fog layer. In addition it is shown that the shape of the size distributions at the top follows a time evolution typical of a quasi-adiabatic droplet growth.

  17. Reliability in the utility computing era: Towards reliable Fog computing

    DEFF Research Database (Denmark)

    Madsen, Henrik; Burtschy, Bernard; Albeanu, G.

    2013-01-01

    This paper considers current paradigms in computing and outlines the most important aspects concerning their reliability. The Fog computing paradigm as a non-trivial extension of the Cloud is considered and the reliability of the networks of smart devices are discussed. Combining the reliability...... requirements of grid and cloud paradigms with the reliability requirements of networks of sensor and actuators it follows that designing a reliable Fog computing platform is feasible....

  18. Spacetime effects on satellite-based quantum communications

    Science.gov (United States)

    Bruschi, David Edward; Ralph, Timothy C.; Fuentes, Ivette; Jennewein, Thomas; Razavi, Mohsen

    2014-08-01

    We investigate the consequences of space-time being curved on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore adding additional noise to the channel for the transmission of information. The effects could be measured with current technology.

  19. Spacetime effects on satellite-based quantum communications

    CERN Document Server

    Bruschi, David Edward; Fuentes, Ivette; Jennewein, Thomas; Razavi, Mohsen

    2013-01-01

    We investigate the effects of space-time curvature on space-based quantum communication protocols. We analyze tasks that require either the exchange of single photons in a certain entanglement distribution protocol or beams of light in a continuous-variable quantum key distribution scheme. We find that gravity affects the propagation of photons, therefore acting as a noisy channel for the transmission of information. The effects can be measured with current technology.

  20. Implementing earth observation and advanced satellite based atmospheric sounders for water resource and climate modelling

    DEFF Research Database (Denmark)

    Boegh, E.; Dellwik, Ebba; Hahmann, Andrea N.;

    This paper discusses preliminary remote sensing (MODIS) based hydrological modelling results for the Danish island Sjælland (7330 km2) in relation to project objectives and methodologies of a new research project “Implementing Earth observation and advanced satellite based atmospheric sounders...... for effective land surface representation in water resource modeling” (2009- 2012). The purpose of the new research project is to develop remote sensing based model tools capable of quantifying the relative effects of site-specific land use change and climate variability at different spatial scales....... For this purpose, a) internal catchment processes will be studied using a Distributed Temperature Sensing (DTS) system, b) Earth observations will be used to upscale from field to regional scales, and c) at the largest scale, satellite based atmospheric sounders and meso-scale climate modelling will be used...

  1. Neural network-based recognition of whistlers on spectrograms detected by satellite

    Science.gov (United States)

    Conti, Livio

    2016-04-01

    We present a system to automatically recognize and classify the occurrence of whistler waves on spectrograms of electric field measurements performed by satellite. Whistlers - VLF waves generated by lightning, with a specific spectral dispersion relation - can induce precipitation of trapped Van Allen particles and have a role in the chemistry of some atmospheric components (mainly NOx). Moreover, it has also been suggested that the increase of the number of anomalous whistlers (i.e. whistlers with high value of dispersion constant) could be induced by disturbances in the Earth-ionosphere wave-guide, generated by seismo-electromagnetic emissions. On satellite, the recognition of whistlers asks for analyzing high-resolution spectrograms that cannot be downloaded to Earth, due to the limits of data transmission. For this reason, a real time identification and classification must be performed on satellite, by avoiding downloading all the unprocessed data. The procedure that we have developed is based on a Time Delay Neural Network (TDNN). The TDNN, proposed some years ago for speech recognition, can be fruitfully also applied in real-time analysis of electromagnetic spectrograms in order to detect phenomena characterized by a specific shape/signature such as those of the whistler waves. Some studies have been performed by the RNF experiment on board of the DEMETER satellite and our algorithm could be adopted on board of the satellite CSES (China Seismo-Electromagnetic Satellite), launch scheduled by the end of 2016. Moreover, the procedure can be also adopted to automatic analysis of whistlers detected on ground.

  2. Comparison of NO2 vertical profiles from satellite and ground based measurements over Antarctica

    OpenAIRE

    Kulkarni, Pavan; Bortoli, Daniele; Costa, Maria João; Silva, Ana Maria; Ravegnani, Fabrizio; Giovanelli, Giorgio

    2011-01-01

    The Intercomparison of nitrogen dioxide (NO2) vertical profiles, derived from the satellite based HALogen Occultation Experiment (HALOE) measurements and from the ground based UV-VIS spectrometer GASCOD (Gas Analyzer Spectrometer Correlating Optical Differences) observations at the Mario Zucchelli Station (MZS), in Antarctica, are done for the first time. It is shown here that both datasets are in good agreement showing the same features in terms of magnitude, profile structure, a...

  3. A Satellite-Based Multi-Pollutant Index of Global Air Quality

    Science.gov (United States)

    Cooper, Mathew J.; Martin, Randall V.; vanDonkelaar, Aaron; Lamsal, Lok; Brauer, Michael; Brook, Jeffrey R.

    2012-01-01

    Air pollution is a major health hazard that is responsible formillions of annual excess deaths worldwide. Simpleindicators are useful for comparative studies and to asses strends over time. The development of global indicators hasbeen impeded by the lack of ground-based observations in vast regions of the world. Recognition is growing of the need for amultipollutant approach to air quality to better represent human exposure. Here we introduce the prospect of amultipollutant air quality indicator based on observations from satellite remote sensing.

  4. Heavy precipitation retrieval from combined satellite observations and ground-based lightning measurements

    Science.gov (United States)

    Mugnai, A.; Dietrich, S.; Casella, D.; di Paola, F.; Formenton, M.; Sanò, P.

    2010-09-01

    We have developed a series of algorithms for the retrieval of precipitation (especially, heavy precipitation) over the Mediterranean area using satellite observations from the available microwave (MW) radiometers onboard low Earth orbit (LEO) satellites and from the visible-infrared (VIS-IR) SEVIRI radiometer onboard the European geosynchronous (GEO) satellite Meteosat Second Generation (MSG), in conjunction with lightning data from ground-based networks - such as ZEUS and LINET. These are: • A new approach for precipitation retrieval from space (which we call the Cloud Dynamics and Radiation Database approach, CDRD) that incorporates lightning and environmental/dynamical information in addition to the upwelling microwave brightness temperatures (TB’s) so as to reduce the retrieval uncertainty and improve the retrieval performance; • A new combined MW-IR technique for producing frequent precipitation retrievals from space (which we call PM-GCD technique), that uses passive-microwave (PM) retrievals in conjunction with lightning information and the Global Convection Detection (GCD) technique to discriminate deep convective clouds within the GEO observations; • A new morphing approach (which we call the Lightning-based Precipitation Evolving Technique, L-PET) that uses the available lightning measurements for propagating the rainfall estimates from satellite-borne MW radiometers to a much higher time resolution than the MW observations. We will present and discuss our combined MW/IR/lightning precipitation algorithms and analyses with special reference to some case studies over the western Mediterranean.

  5. Planetary gearbox condition monitoring of ship-based satellite communication antennas using ensemble multiwavelet analysis method

    Science.gov (United States)

    Chen, Jinglong; Zhang, Chunlin; Zhang, Xiaoyan; Zi, Yanyang; He, Shuilong; Yang, Zhe

    2015-03-01

    Satellite communication antennas are key devices of a measurement ship to support voice, data, fax and video integration services. Condition monitoring of mechanical equipment from the vibration measurement data is significant for guaranteeing safe operation and avoiding the unscheduled breakdown. So, condition monitoring system for ship-based satellite communication antennas is designed and developed. Planetary gearboxes play an important role in the transmission train of satellite communication antenna. However, condition monitoring of planetary gearbox still faces challenges due to complexity and weak condition feature. This paper provides a possibility for planetary gearbox condition monitoring by proposing ensemble a multiwavelet analysis method. Benefit from the property on multi-resolution analysis and the multiple wavelet basis functions, multiwavelet has the advantage over characterizing the non-stationary signal. In order to realize the accurate detection of the condition feature and multi-resolution analysis in the whole frequency band, adaptive multiwavelet basis function is constructed via increasing multiplicity and then vibration signal is processed by the ensemble multiwavelet transform. Finally, normalized ensemble multiwavelet transform information entropy is computed to describe the condition of planetary gearbox. The effectiveness of proposed method is first validated through condition monitoring of experimental planetary gearbox. Then this method is used for planetary gearbox condition monitoring of ship-based satellite communication antennas and the results support its feasibility.

  6. Satellite image blind restoration based on surface fitting and multivariate model

    Institute of Scientific and Technical Information of China (English)

    CHEN Xin-bing; YANG Shi-zhi; WANG Xian-hua; QIAO Yan-li

    2009-01-01

    Owing to the blurring effect from atmosphere and camera system in the satellite imaging a blind image restoration algo-rithm is proposed which includes the modulation transfer function (MTF) estimation and the image restoration. In the MTF estimation stage, based on every degradation process of satellite imaging-chain, a combined parametric model of MTF is given and used to fit the surface of normalized logarithmic amplitude spectrum of degraded image. In the image restoration stage, a maximum a posteriori (MAP) based edge-preserving image restoration method is presented which introduces multivariate Laplacian model to characterize the prior distribution of wavelet coefficients of original image. During the image restoration, in order to avoid solving high nonlinear equations, optimization transfer algorithm is adopted to decom-pose the image restoration procedure into two simple steps: Landweber iteration and wavelet thresholding denoising. In the numerical experiment, the satellite image restoration results from SPOT-5 and high resolution camera (HR) of China & Brazil earth resource satellite (CBERS-02B) ane compared, and the proposed algorithm is superior in the image edge preservation and noise inhibition.

  7. The turbulent structure and transport in fog layers observed over the Tianjin area

    Science.gov (United States)

    Ye, Xinxin; Wu, Bingui; Zhang, Hongsheng

    2015-02-01

    This paper investigates the vertical structure and turbulence activities in fog events. Three fog cases that occurred in the winter of 2010 over Tianjin, China were selected, including two advection-radiation fog events and an advection fog event. Field observations collected at a 255-m tall meteorological tower in Tianjin were analyzed, including turbulence measurements using the eddy covariance systems installed at three levels, measurements of temperature, horizontal wind and humidity collected at 15 levels, surface radiation fluxes and horizontal visibility. The results suggest that the advection fog was more enduring and thicker than the advection-radiation fog. The fog events were characterized by low wind speed throughout the fog layer. A temperature inversion and low-level jet were observed above the advection-radiation fog layer. The surface net radiation reflected some differences among the fog events. The collapse of turbulence was a necessity for the formation fog, and moderate turbulence was favorable to the development and maintenance. The heat and water vapor fluxes in the advection-radiation fog were weaker than those in the advection fog, in which the stratification was slightly unstable. The relationships among the turbulent transport efficiencies of water vapor, temperature and momentum were examined. The results suggest the applicability of local similarity in the fog layer for the momentum transport efficiency.

  8. Pattern recognition applied to infrared images for early alerts in fog

    Science.gov (United States)

    Boucher, Vincent; Marchetti, Mario; Dumoulin, Jean; Cord, Aurélien

    2014-09-01

    Fog conditions are the cause of severe car accidents in western countries because of the poor induced visibility. Its forecast and intensity are still very difficult to predict by weather services. Infrared cameras allow to detect and to identify objects in fog while visibility is too low for eye detection. Over the past years, the implementation of cost effective infrared cameras on some vehicles has enabled such detection. On the other hand pattern recognition algorithms based on Canny filters and Hough transformation are a common tool applied to images. Based on these facts, a joint research program between IFSTTAR and Cerema has been developed to study the benefit of infrared images obtained in a fog tunnel during its natural dissipation. Pattern recognition algorithms have been applied, specifically on road signs which shape is usually associated to a specific meaning (circular for a speed limit, triangle for an alert, …). It has been shown that road signs were detected early enough in images, with respect to images in the visible spectrum, to trigger useful alerts for Advanced Driver Assistance Systems.

  9. A MODIS-Based Robust Satellite Technique (RST for Timely Detection of Oil Spilled Areas

    Directory of Open Access Journals (Sweden)

    Teodosio Lacava

    2017-02-01

    Full Text Available Natural crude-oil seepages, together with the oil released into seawater as a consequence of oil exploration/production/transportation activities, and operational discharges from tankers (i.e., oil dumped during cleaning actions represent the main sources of sea oil pollution. Satellite remote sensing can be a useful tool for the management of such types of marine hazards, namely oil spills, mainly owing to the synoptic view and the good trade-off between spatial and temporal resolution, depending on the specific platform/sensor system used. In this paper, an innovative satellite-based technique for oil spill detection, based on the general robust satellite technique (RST approach, is presented. It exploits the multi-temporal analysis of data acquired in the visible channels of the Moderate Resolution Imaging Spectroradiometer (MODIS on board the Aqua satellite in order to automatically and quickly detect the presence of oil spills on the sea surface, with an attempt to minimize “false detections” caused by spurious effects associated with, for instance, cloud edges, sun/satellite geometries, sea currents, etc. The oil spill event that occurred in June 2007 off the south coast of Cyprus in the Mediterranean Sea has been considered as a test case. The resulting data, the reliability of which has been evaluated by both carrying out a confutation analysis and comparing them with those provided by the application of another independent MODIS-based method, showcase the potential of RST in identifying the presence of oil with a high level of accuracy.

  10. Research on measurement method of optical transmittance of the artificial fog

    Science.gov (United States)

    Hu, Jianghua; Jian, Chaochao; Cui, Guangzhen; Lv, Xuliang; Rong, Xianhui

    2016-10-01

    The attenuation of light was a common result that the light was absorbed and scattered by the artificial fog particles when it transmitted in the artificial fog. The absorbing attenuation process of light transmission in the artificial fog was that the artificial fog converting incident light energy into other forms of internal energy (such as heat energy). The scattering attenuation process of light transmission in the artificial fog was that the artificial fog particles intercepting incident radiation energy to form infrasonic waves and to radiate peripherally so that the incident light energy was reduced on the original direction of transmission. The mechanism of light transmission attenuation in the artificial fog was analyzed. The formation method of the artificial fog was expounded and the measuring principle of the artificial fog transmittance was described. A simple and reliable measurement method of the optical transmittance of the artificial fog in the fog chamber was proposed. The optical transmittance measurement system of the artificial fog was built by using incandescent lamp, power with steady current and voltage, lens, selenium photocell, micro-galvanometer, optical bench, hygrothermograph, humidifier, etc. Under different conditions of humidity, the optical transmittance of the artificial fog was obtained on the basis of measuring the photocurrent before the fog was formed in the fog chamber. The test results show that the measurement system is stable and reliable. During the 43 minutes after the artificial fog was formed, the optical transmittance of the artificial fog was averagely less than 5 percent and the optical transmittance increased gradually with the extension of time. In addition, the optical transmittance of artificial fog didn't produce obvious change while air humidity increased from 68.7% to 85%. The measurement system can be used to measure transmittance of smoke screen, water mist and other aerosol.

  11. Volcview: A Web-Based Platform for Satellite Monitoring of Volcanic Activity and Eruption Response

    Science.gov (United States)

    Schneider, D. J.; Randall, M.; Parker, T.

    2014-12-01

    The U.S. Geological Survey (USGS), in cooperation with University and State partners, operates five volcano observatories that employ specialized software packages and computer systems to process and display real-time data coming from in-situ geophysical sensors and from near-real-time satellite sources. However, access to these systems both inside and from outside the observatory offices are limited in some cases by factors such as software cost, network security, and bandwidth. Thus, a variety of Internet-based tools have been developed by the USGS Volcano Science Center to: 1) Improve accessibility to data sources for staff scientists across volcano monitoring disciplines; 2) Allow access for observatory partners and for after-hours, on-call duty scientists; 3) Provide situational awareness for emergency managers and the general public. Herein we describe VolcView (volcview.wr.usgs.gov), a freely available, web-based platform for display and analysis of near-real-time satellite data. Initial geographic coverage is of the volcanoes in Alaska, the Russian Far East, and the Commonwealth of the Northern Mariana Islands. Coverage of other volcanoes in the United States will be added in the future. Near-real-time satellite data from NOAA, NASA and JMA satellite systems are processed to create image products for detection of elevated surface temperatures and volcanic ash and SO2 clouds. VolcView uses HTML5 and the canvas element to provide image overlays (volcano location and alert status, annotation, and location information) and image products that can be queried to provide data values, location and measurement capabilities. Use over the past year during the eruptions of Pavlof, Veniaminof, and Cleveland volcanoes in Alaska by the Alaska Volcano Observatory, the National Weather Service, and the U.S. Air Force has reinforced the utility of shared situational awareness and has guided further development. These include overlay of volcanic cloud trajectory and

  12. Fog-drip contributions to soil moisture as determined through passive fog collector measurements, leaf wetness data, and soil moisture at Pepperwood Preserve, Sonoma County, California.

    Science.gov (United States)

    Micheli, L.; Dodge, C.; Fernandez, D.; Weiss, P. L.; Flint, L. E.; Flint, A. L.; Torregrosa, A.

    2016-12-01

    Summertime coastal fog advects from the ocean and transports water inland in the form of fog droplets to forests and grasslands. The amount of fog water delivered to the soil through fog drip from foliage and other surfaces that have captured and accumulated the droplets is often difficult to quantify due to many challenges including the difficulty of measuring the relatively small variations in soil moisture that accompany fog events. This study details summer season records collected from 4 sites at the Pepperwood Preserve in Santa Rosa, CA. Fog drip volumes were measured using 1 m2 standard fog collectors located at a grassland site for the past three summers. Soil moisture measurements were collected for portions of the three summer seasons from three sites: two oak woodland understory sites and a grassland site on the edge of a forest. One oak woodland site was within 400 m of the standard fog collector grassland site. Leaf wetness sensors (LWS) were co-located at all soil moisture sites. We observe a much higher frequency of wet periods at the grassland site than at the nearby oak woodland site during the summer fog season. One hypothesis is that the oak canopy acts to protect the LWS at the oak woodland site from nocturnal radiative cooling, thereby reducing condensation and dew formation. Another hypothesis is that the oak woodland canopy tends sheltered the understory during light fog events, resulting in edge effects that may tend to reduce fog deposition within the canopy. Leaf and soil moisture measurements both during fog events and during periods without fog but when dew point is reached may provide a more complete picture of non-rain mechanisms of moisture delivery to the foliage and the soil. Investigations are on-going to include corresponding meteorological data (wind speed and direction, relative humidity and temperature) to understand relative contributions to the soil associated with both fog and dew and to better distinguish between fog and

  13. Satellite-based RAR performance simulation for measuring directional ocean wave spectrum based on SAR inversion spectrum

    Institute of Scientific and Technical Information of China (English)

    REN Lin; MAO Zhihua; HUANG Haiqing; GONG Fang

    2010-01-01

    Some missions have been carried out to measure wave directional spectrum by synthetic aperture radar (SAR) and airborne real aperture radar (RAR) at a low incidence. Both them have their own advantages and limitations. Scientists hope that SAR and satellite-based RAR can complement each other for the research on wave properties in the future. For this study, the authors aim to simulate the satellite-based RAR system to validate performance for measuring the directional wave spectrum. The principal measurements are introduced and the simulation methods based on the one developed by Hauser are adopted and slightly modified. To enhance the authenticity of input spectrum and the wave spectrum measuring consistency for SAR and satellite-based RAR, the wave height spectrum inversed from Envisat ASAR data by cross spectrum technology is used as the input spectrum of the simulation system. In the process of simulation, the sea surface, backscattering signal, modulation spectrum and the estimated wave height spectrum are simulated in each look direction. Directional wave spectrum are measured based on the simulated observations from 0° to 360~. From the estimated wave spectrum, it has an 180° ambiguity like SAR, but it has no special high wave number cut off in all the direction. Finally, the estimated spectrum is compared with the input one in terms of the dominant wave wavelength, direction and SWH and the results are promising. The simulation shows that satellite-based RAR should be capable of measuring the directional wave properties. Moreover, it indicates satellite-based RAR basically can measure waves that SAR can measure.

  14. Multiangle Bistatic SAR Imaging and Fusion Based on BeiDou-2 Navigation Satellite System

    Directory of Open Access Journals (Sweden)

    Zeng Tao

    2015-01-01

    Full Text Available Bistatic Synthetic Aperture Radar (BSAR based on the Global Navigation Service System (GNSSBSAR uses navigation satellites as radar transmitters, which are low in cost. However, GNSS-BSAR images have poor resolution and low Signal-to-Noise Ratios (SNR. In this paper, a multiangle observation and data processing strategy are presented based on BeiDou-2 navigation satellite imagery, from which twenty-six BSAR images in different configurations are obtained. A region-based fusion algorithm using region of interest segmentation is proposed, and a high-quality fusion image is obtained. The results reveal that the multiangle imaging method can extend the applications of GNSS-BSAR.

  15. BeiDou satellite's differential code biases estimation based on uncombined precise point positioning with triple-frequency observable

    Science.gov (United States)

    Fan, Lei; Li, Min; Wang, Cheng; Shi, Chuang

    2017-02-01

    The differential code bias (DCB) of BeiDou satellite is an important topic to make better use of BeiDou system (BDS) for many practical applications. This paper proposes a new method to estimate the BDS satellite DCBs based on triple-frequency uncombined precise point positioning (UPPP). A general model of both triple-frequency UPPP and Geometry-Free linear combination of Phase-Smoothed Range (GFPSR) is presented, in which, the ionospheric observable and the combination of triple-frequency satellite and receiver DCBs (TF-SRDCBs) are derived. Then the satellite and receiver DCBs (SRDCBs) are estimated together with the ionospheric delay that is modeled at each individual station in a weighted least-squares estimator, and the satellite DCBs are determined by introducing the zero-mean condition of all available BDS satellites. To validate the new method, 90 day's real tracking GNSS data (from January to March in 2014) collected from 9 Multi-GNSS Experiment (MGEX) stations (equipped with Trimble NETR9 receiver) is used, and the BDS satellite DCB products from German Aerospace Center (DLR) are taken as reference values for comparison. Results show that the proposed method is able to precisely estimate BDS satellite DCBs: (1) the mean value of the day-to-day scattering for all available BDS satellites is about 0.24 ns, which is reduced in average by 23% when compared with the results derived by only GFPSR. Moreover, the mean value of the day-to-day scattering of IGSO satellites is lower than that of GEO and MEO satellites; (2) the mean value of RMS of the difference with respect to DLR DCB products is about 0.39 ns, which is improved by an average of 11% when compared with the results derived by only GFPSR. Besides, the RMS of IGSO and MEO satellites is at the same level which is better than that of GEO satellites.

  16. Formulation of geopotential difference determination using optical-atomic clocks onboard satellites and on ground based on Doppler cancellation system

    Science.gov (United States)

    Shen, Ziyu; Shen, Wen-Bin; Zhang, Shuangxi

    2016-08-01

    In this study, we propose an approach for determining the geopotential difference using high-frequency-stability microwave links between satellite and ground station based on Doppler cancellation system. Suppose a satellite and a ground station are equipped with precise optical-atomic clocks (OACs) and oscillators. The ground oscillator emits a signal with frequency fa towards the satellite and the satellite receiver (connected with the satellite oscillator) receives this signal with frequency fb which contains the gravitational frequency shift effect and other signals and noises. After receiving this signal, the satellite oscillator transmits and emits, respectively, two signals with frequencies fb and fc towards the ground station. Via Doppler cancellation technique, the geopotential difference between the satellite and the ground station can be determined based on gravitational frequency shift equation by a combination of these three frequencies. For arbitrary two stations on ground, based on similar procedures as described above, we may determine the geopotential difference between these two stations via a satellite. Our analysis shows that the accuracy can reach 1 m2 s- 2 based on the clocks' inaccuracy of about 10-17 (s s-1) level. Since OACs with instability around 10-18 in several hours and inaccuracy around 10-18 level have been generated in laboratory, the proposed approach may have prospective applications in geoscience, and especially, based on this approach a unified world height system could be realized with one-centimetre level accuracy in the near future.

  17. Integration between terrestrial-based and satellite-based land mobile communications systems

    Science.gov (United States)

    Arcidiancono, Antonio

    A survey is given of several approaches to improving the performance and marketability of mobile satellite systems (MSS). The provision of voice/data services in the future regional European Land Mobile Satellite System (LMSS), network integration between the Digital Cellular Mobile System (GSM) and LMSS, the identification of critical areas for the implementation of integrated GSM/LMSS areas, space segment scenarios, LMSS for digital trunked private mobile radio (PMR) services, and code division multiple access (CDMA) techniques for a terrestrial/satellite system are covered.

  18. Integration between terrestrial-based and satellite-based land mobile communications systems

    Science.gov (United States)

    Arcidiancono, Antonio

    1990-01-01

    A survey is given of several approaches to improving the performance and marketability of mobile satellite systems (MSS). The provision of voice/data services in the future regional European Land Mobile Satellite System (LMSS), network integration between the Digital Cellular Mobile System (GSM) and LMSS, the identification of critical areas for the implementation of integrated GSM/LMSS areas, space segment scenarios, LMSS for digital trunked private mobile radio (PMR) services, and code division multiple access (CDMA) techniques for a terrestrial/satellite system are covered.

  19. Satellite-based phenology detection in broadleaf forests in South-Western Germany

    Science.gov (United States)

    Misra, Gourav; Buras, Allan; Menzel, Annette

    2016-04-01

    Many techniques exist for extracting phenological information from time series of satellite data. However, there have been only a few successful attempts to temporarily match satellite-derived observations with ground based phenological observations (Fisher et al., 2006; Hamunyela et al., 2013; Galiano et al., 2015). Such studies are primarily plagued with problems relating to shorter time series of satellite data including spatial and temporal resolution issues. A great challenge is to correlate spatially continuous and pixel-based satellite information with spatially discontinuous and point-based, mostly species-specific, ground observations of phenology. Moreover, the minute differences in phenology observed by ground volunteers might not be sufficient to produce changes in satellite-measured reflectance of vegetation, which also exposes the difference in the definitions of phenology (Badeck et al., 2004; White et al., 2014). In this study Start of Season (SOS) was determined for broadleaf forests at a site in south-western Germany using MODIS-sensor time series of Normalised Difference Vegetation Index (NDVI) data for the years covering 2001 to 2013. The NDVI time series raster data was masked for broadleaf forests using Corine Land Cover dataset, filtered and corrected for snow and cloud contaminations, smoothed with a Gaussian filter and interpolated to daily values. Several SOS techniques cited in literature, namely thresholds of amplitudes (20%, 50%, 60% and 75%), rates of change (1st, 2nd and 3rd derivative) and delayed moving average (DMA) were tested for determination of satellite SOS. The different satellite SOS were then compared with a species-rich ground based phenology information (e.g. understory leaf unfolding, broad leaf unfolding and greening of evergreen tree species). Working with all the pixels at a finer resolution, it is seen that the temporal trends in understory and broad leaf species are well captured. Initial analyses show promising

  20. Remote Sensing-Based Detection and Spatial Pattern Analysis for Geo-Ecological Niche Modeling of Tillandsia SPP. In the Atacama, Chile

    Science.gov (United States)

    Wolf, N.; Siegmund, A.; del Río, C.; Osses, P.; García, J. L.

    2016-06-01

    In the coastal Atacama Desert in Northern Chile plant growth is constrained to so-called `fog oases' dominated by monospecific stands of the genus Tillandsia. Adapted to the hyperarid environmental conditions, these plants specialize on the foliar uptake of fog as main water and nutrient source. It is this characteristic that leads to distinctive macro- and micro-scale distribution patterns, reflecting complex geo-ecological gradients, mainly affected by the spatiotemporal occurrence of coastal fog respectively the South Pacific Stratocumulus clouds reaching inlands. The current work employs remote sensing, machine learning and spatial pattern/GIS analysis techniques to acquire detailed information on the presence and state of Tillandsia spp. in the Tarapacá region as a base to better understand the bioclimatic and topographic constraints determining the distribution patterns of Tillandsia spp. Spatial and spectral predictors extracted from WorldView-3 satellite data are used to map present Tillandsia vegetation in the Tarapaca region. Regression models on Vegetation Cover Fraction (VCF) are generated combining satellite-based as well as topographic variables and using aggregated high spatial resolution information on vegetation cover derived from UAV flight campaigns as a reference. The results are a first step towards mapping and modelling the topographic as well as bioclimatic factors explaining the spatial distribution patterns of Tillandsia fog oases in the Atacama, Chile.

  1. REMOTE SENSING-BASED DETECTION AND SPATIAL PATTERN ANALYSIS FOR GEO-ECOLOGICAL NICHE MODELING OF TILLANDSIA SPP. IN THE ATACAMA, CHILE

    Directory of Open Access Journals (Sweden)

    N. Wolf

    2016-06-01

    Full Text Available In the coastal Atacama Desert in Northern Chile plant growth is constrained to so-called ‘fog oases’ dominated by monospecific stands of the genus Tillandsia. Adapted to the hyperarid environmental conditions, these plants specialize on the foliar uptake of fog as main water and nutrient source. It is this characteristic that leads to distinctive macro- and micro-scale distribution patterns, reflecting complex geo-ecological gradients, mainly affected by the spatiotemporal occurrence of coastal fog respectively the South Pacific Stratocumulus clouds reaching inlands. The current work employs remote sensing, machine learning and spatial pattern/GIS analysis techniques to acquire detailed information on the presence and state of Tillandsia spp. in the Tarapacá region as a base to better understand the bioclimatic and topographic constraints determining the distribution patterns of Tillandsia spp. Spatial and spectral predictors extracted from WorldView-3 satellite data are used to map present Tillandsia vegetation in the Tarapaca region. Regression models on Vegetation Cover Fraction (VCF are generated combining satellite-based as well as topographic variables and using aggregated high spatial resolution information on vegetation cover derived from UAV flight campaigns as a reference. The results are a first step towards mapping and modelling the topographic as well as bioclimatic factors explaining the spatial distribution patterns of Tillandsia fog oases in the Atacama, Chile.

  2. Star Family Seen Through Dusty Fog

    Science.gov (United States)

    2007-03-01

    missed a significant number of globular clusters, particularly close to the disc of the Galaxy, where dense clouds of dust and gas obscure the view. In the early times of extragalactic astronomy this area was called the 'Zone of Avoidance' because extragalactic stellar systems appeared to be very rare in this part of the sky. Searching for the missing globular clusters in our Galaxy requires observations in the infrared, because infrared radiation is able to penetrate the thick 'galactic fog'. Using modern, sensitive infrared detectors, this is now possible. Completing the census is not only a challenge for its own sake, as finding new globular clusters is useful for several additional reasons. For example, analysing their orbits allows astronomers to draw conclusions about the distribution of mass in the Galaxy. Star clusters can therefore be used as probes for the large-scale structure of the Milky Way. "It has been estimated that the region close to the Galactic Centre might contain about 10 so far unknown globular clusters and we have started a large campaign to unveil and characterise them," explains Helmut Meusinger, from the Thüringer Landessternwarte Tautenburg, Germany, and part of the team. The astronomers carried out a systematic and automated large-scale (14,400 square degrees) search for globular cluster candidates in the entire Galactic Plane, based on the near-infrared Two Micron All Sky Survey (2MASS). Eventually, only about a dozen candidate objects remained. The astronomers observed these candidates with the SofI instrument attached to ESO's New Technology Telescope (NTT) at La Silla (Chile), taking images through three different near-infrared filters. The new images are ten times deeper and have a much better angular resolution than the original 2MASS images, thereby allowing the astronomers to resolve at least partly the dense accumulation of stars in the globular cluster candidates. One of these candidates had the number 1735 in the list of

  3. Developing a sustainable satellite-based environmental monitoring system In Nigeria

    Science.gov (United States)

    Akinyede, J. O.; Adepoju, K. A.; Akinluyi, F. O.; Anifowose, A. Y. B.

    2015-10-01

    Increased anthropogenic activities over the year have remained a major factor of the Earth changing environment. This phenomenon has given rise to a number of environmental degraded sites that characterize the Nigeria's landscape. The human-induced elements include gully erosion, mangrove ecosystems degradation, desertification and deforestation, particularly in the south east, Niger Delta, north east and south west of Nigeria respectively, as well as river flooding/flood plain inundation and land degradation around Kainji lake area. Because of little or no effective management measures, the attendant environmental hazards have been extremely damaging to the infrastructures and socio-economic development of the affected area. Hence, a concerted effort, through integrated and space-based research, is being intensified to manage and monitor the environment in order to restore the stability, goods and services of the environment. This has justified Nigeria's investment in its space programme, especially the launch of NigeriaSat-1, an Earth observation micro-satellite in constellation with five (5) other similar satellites, Alsat-1, China DMC, Bilsat-1, DEMOS and UK DMC belonging to Algeria, China, Turkey, Spain and United Kingdom respectively. The use of data from these satellites, particularly NigeriaSat-1, in conjunction with associated technologies has proved to be very useful in understanding the influence of both natural and human activities on the Nigeria's ecosystems and environment. The results of some researches on specific applications of Nigerian satellites are presented in this paper. Appropriate sustainable land and water resources management in the affected areas, based on Nigeria's satellite data capture and integration, are also discussed.

  4. DroughtView: Satellite Based Drought Monitoring and Assessment

    Science.gov (United States)

    Hartfield, K. A.; Van Leeuwen, W. J. D.; Crimmins, M.; Marsh, S. E.; Torrey, Y.; Rahr, M.; Orr, B. J.

    2014-12-01

    Drought is an ever growing concern within the United States and Mexico. Extended periods of below-average precipitation can adversely affect agricultural production and ecosystems, impact local water resources and create conditions prime for wildfire. DroughtView (www.droughtview.arizona.edu) is a new on-line resource for scientists, natural resource managers, and the public that brings a new perspective to remote-sensing based drought impact assessment that is not currently available. DroughtView allows users to monitor the impact of drought on vegetation cover for the entire continental United States and the northern regions of Mexico. As a spatially and temporally dynamic geospatial decision support tool, DroughtView is an excellent educational introduction to the relationship between remotely sensed vegetation condition and drought. The system serves up Normalized Difference Vegetation Index (NDVI) and Enhanced Vegetation Index (EVI) data generated from 250 meter 16-day composite Moderate-resolution Imaging Spectroradiometer (MODIS) imagery from 2000 to the present. Calculation of difference from average, previous period and previous year greenness products provide the user with a proxy for drought conditions and insight on the secondary impacts of drought, such as wildfire. The various image products and overlays are served up via the ArcGIS Server platform. DroughtView serves as a useful tool to introduce and teach vegetation time series analysis to those unfamiliar with the science. High spatial resolution imagery is available as a reference layer to locate points of interest, zoom in and export images for implementation in reports and presentations. Animation of vegetation time series allows users to examine ecosystem disturbances and climate data is also available to examine the relationship between precipitation, temperature and vegetation. The tool is mobile friendly allowing users to access the system while in the field. The systems capabilities and

  5. A space weather forecasting system with multiple satellites based on a self-recognizing network.

    Science.gov (United States)

    Tokumitsu, Masahiro; Ishida, Yoshiteru

    2014-05-05

    This paper proposes a space weather forecasting system at geostationary orbit for high-energy electron flux (>2 MeV). The forecasting model involves multiple sensors on multiple satellites. The sensors interconnect and evaluate each other to predict future conditions at geostationary orbit. The proposed forecasting model is constructed using a dynamic relational network for sensor diagnosis and event monitoring. The sensors of the proposed model are located at different positions in space. The satellites for solar monitoring equip with monitoring devices for the interplanetary magnetic field and solar wind speed. The satellites orbit near the Earth monitoring high-energy electron flux. We investigate forecasting for typical two examples by comparing the performance of two models with different numbers of sensors. We demonstrate the prediction by the proposed model against coronal mass ejections and a coronal hole. This paper aims to investigate a possibility of space weather forecasting based on the satellite network with in-situ sensing.

  6. An Attitude Modelling Method Based on the Inherent Frequency of a Satellite Platform

    Science.gov (United States)

    Mo, F.; Tang, X.; Xie, J.; Yan, C.

    2017-05-01

    The accuracy of attitude determination plays a key role in the improvement of surveying and mapping accuracy for high-resolution remote-sensing satellites, and it is a bottleneck in large-scale satellite topographical mapping. As the on-board energy is constrained and the performance of an attitude-measurement device is limited, the attitude acquired is discretely sampled with a settled time interval. The larger the interval, the easier the data transmission, and the more deviation the attitude data will have. Meanwhile, several kinds of jitter frequencies have been detected in satellite platforms. This paper presents a novel attitude modelling (AttModel) method that sufficiently considers the discrete and periodic characteristics, and the attitude model built is continuous and consists of several inherent waves of different frequencies. The process of modelling includes two steps: (a) frequency detection, which uses raw gyroscope data within a period of time to detect the attitude frequencies (as the gyroscope data can actually reflect continuous, very small changes of the satellite platform), and (b) attitude modelling , which processes the attitude data that was filtered by extended Kalman filtering based on general polynomial and trigonometric polynomials, and these trigonometric polynomials are rebuilt by those frequencies detected in the first part of the modelling process. Finally, one experiment designed for verifying the effectiveness of the presented method shows that the AttModel method can reach a slightly better pointing accuracy without ground-control points than traditional attitude-interpolation methods.

  7. Evaluation of satellite based indices for primary production estimates in a sparse savanna in the Sudan

    Directory of Open Access Journals (Sweden)

    M. Sjöström

    2008-07-01

    Full Text Available One of the more frequently applied methods for integrating controls on primary production through satellite data is the Light Use Efficiency (LUE approach. Satellite indices such as the Enhanced Vegetation Index (EVI and the Shortwave Infrared Water Stress Index (SIWSI have previously shown promise as predictors of primary production in several different environments. In this study, we evaluate EVI and SIWSI derived from the Moderate Resolution Imaging Spectroradiometer (MODIS satellite sensor against in-situ measurements from central Sudan in order to asses their applicability in LUE-based primary production modelling within a water limited environment. Results show a strong correlation between EVI against gross primary production (GPP, demonstrating the significance of EVI for deriving information on primary production with relatively high accuracy at similar areas. Evaluation of SIWSI however, reveal that the fraction of vegetation apparently is to low for the index to provide accurate information on canopy water content, indicating that the use of SIWSI as a predictor of water stress in satellite data-driven primary production modelling in similar semi-arid ecosystems is limited.

  8. Constellation design for earth observation based on the characteristics of the satellite ground track

    Science.gov (United States)

    Luo, Xin; Wang, Maocai; Dai, Guangming; Song, Zhiming

    2017-04-01

    This paper responds to the increasing need for Earth observation missions and deals with the design of Repeating Sun-Synchronous Constellations (RSSCs) which takes into consideration of constellations composed of one or more orbital planes. Based on the mature design approach of Repeating Sun-synchronous orbits, a novel technique to design RSSCs is presented, which takes the second gravitational zonal harmonic into consideration. In order to obtain regular cycles of observation of the Earth by a single satellite, the orbital relationships have to be satisfied firstly are illustrated. Then, by making full analyses of the characteristics of the satellite ground track, orbital parameters are properly calculated to make other satellites pass on the same or different ground track of the single satellite. Last, single-plane or multi-plane constellations are used to improve the repetitions of the observation and the ground resolution. RSSCs allow observing the same region once at the same local time in a solar day and several times at the different local time in a solar day. Therefore, this kind of constellations meets all requirements for the remote sensing applications, which need to observe the same region under the same or different visible conditions. Through various case studies, the calculation technique is successfully demonstrated.

  9. Sensitivity of Distributed Hydrologic Simulations to Ground and Satellite Based Rainfall Products

    Directory of Open Access Journals (Sweden)

    Singaiah Chintalapudi

    2014-05-01

    Full Text Available In this study, seven precipitation products (rain gauges, NEXRAD MPE, PERSIANN 0.25 degree, PERSIANN CCS-3hr, PERSIANN CCS-1hr, TRMM 3B42V7, and CMORPH were used to force a physically-based distributed hydrologic model. The model was driven by these products to simulate the hydrologic response of a 1232 km2 watershed in the Guadalupe River basin, Texas. Storm events in 2007 were used to analyze the precipitation products. Comparison with rain gauge observations reveals that there were significant biases in the satellite rainfall products and large variations in the estimated amounts. The radar basin average precipitation compared very well with the rain gauge product while the gauge-adjusted TRMM 3B42V7 precipitation compared best with observed rainfall among all satellite precipitation products. The NEXRAD MPE simulated streamflows matched the observed ones the best yielding the highest Nash-Sutcliffe Efficiency correlation coefficient values for both the July and August 2007 events. Simulations driven by TRMM 3B42V7 matched the observed streamflow better than other satellite products for both events. The PERSIANN coarse resolution product yielded better runoff results than the higher resolution product. The study reveals that satellite rainfall products are viable alternatives when rain gauge or ground radar observations are sparse or non-existent.

  10. Assessment of the quality of OSIRIS mesospheric temperatures using satellite and ground-based measurements

    Directory of Open Access Journals (Sweden)

    P. E. Sheese

    2012-12-01

    Full Text Available The Optical Spectrograph and InfraRed Imaging System (OSIRIS on the Odin satellite is currently in its 12th year of observing the Earth's limb. For the first time, continuous temperature profiles extending from the stratopause to the upper mesosphere have been derived from OSIRIS measurements of Rayleigh-scattered sunlight. Through most of the mesosphere, OSIRIS temperatures are in good agreement with coincident temperature profiles derived from other satellite and ground-based measurements. In the altitude region of 55–80 km, OSIRIS temperatures are typically within 4–5 K of those from the SABER, ACE-FTS, and SOFIE instruments on the TIMED, SciSat-I, and AIM satellites, respectively. The mean differences between individual OSIRIS profiles and those of the other satellite instruments are typically within the combined uncertainties and previously reported biases. OSIRIS temperatures are typically within 2 K of those from the University of Western Ontario's Purple Crow Lidar in the altitude region of 52–79 km, where the mean differences are within combined uncertainties. Near 84 km, OSIRIS temperatures exhibit a cold bias of 10–15 K, which is due to a cold bias in OSIRIS O2 A-band temperatures at 85 km, the upper boundary of the Rayleigh-scatter derived temperatures; and near 48 km OSIRIS temperatures exhibit a cold bias of 5–15 K, which is likely due to multiple-scatter effects that are not taken into account in the retrieval.

  11. A Space Weather Forecasting System with Multiple Satellites Based on a Self-Recognizing Network

    Directory of Open Access Journals (Sweden)

    Masahiro Tokumitsu

    2014-05-01

    Full Text Available This paper proposes a space weather forecasting system at geostationary orbit for high-energy electron flux (>2 MeV. The forecasting model involves multiple sensors on multiple satellites. The sensors interconnect and evaluate each other to predict future conditions at geostationary orbit. The proposed forecasting model is constructed using a dynamic relational network for sensor diagnosis and event monitoring. The sensors of the proposed model are located at different positions in space. The satellites for solar monitoring equip with monitoring devices for the interplanetary magnetic field and solar wind speed. The satellites orbit near the Earth monitoring high-energy electron flux. We investigate forecasting for typical two examples by comparing the performance of two models with different numbers of sensors. We demonstrate the prediction by the proposed model against coronal mass ejections and a coronal hole. This paper aims to investigate a possibility of space weather forecasting based on the satellite network with in-situ sensing.

  12. Detecting aircrafts from satellite images using saliency and conical pyramid based template representation

    Indian Academy of Sciences (India)

    SAMIK BANERJEE; NITIN GUPTA; SUKHENDU DAS; PINAKI ROY CHOWDHURY; L K SINHA

    2016-10-01

    Automatic target localization in satellite images still remains as a challenging problem in the field of computer vision. The issues involved in locating targets in satellite images are viewpoint, spectral (intensity) and scale variations. Diversity in background texture and target clutter also adds up to the complexity of the problem of localizing aircrafts in satellite images. Failure of modern feature extraction and object detection methods highlight the complexity of the problem. In the proposed work, pre-processing techniques, viz.denoising and contrast enhancement, are first used to improve the quality of the images. Then, the concept of unsupervised saliency is used to detect the potential regions of interest, which reduces the search space. Parts from the salient regions are further processed using clustering and morphological processing to get the probable regions of isolated aircraft targets. Finally, a novel conical pyramid based framework for template representation of the target samples is proposed for matching. Experimental results shown on a few satellite images exhibit the superior performance of the proposed methods.

  13. The Satellite based Monitoring Initiative for Regional Air quality (SAMIRA): Project summary and first results

    Science.gov (United States)

    Schneider, Philipp; Stebel, Kerstin; Ajtai, Nicolae; Diamandi, Andrei; Horalek, Jan; Nemuc, Anca; Stachlewska, Iwona; Zehner, Claus

    2017-04-01

    We present a summary and some first results of a new ESA-funded project entitled Satellite based Monitoring Initiative for Regional Air quality (SAMIRA), which aims at improving regional and local air quality monitoring through synergetic use of data from present and upcoming satellite instruments, traditionally used in situ air quality monitoring networks and output from chemical transport models. Through collaborative efforts in four countries, namely Romania, Poland, the Czech Republic and Norway, all with existing air quality problems, SAMIRA intends to support the involved institutions and associated users in their national monitoring and reporting mandates as well as to generate novel research in this area. The primary goal of SAMIRA is to demonstrate the usefulness of existing and future satellite products of air quality for improving monitoring and mapping of air pollution at the regional scale. A total of six core activities are being carried out in order to achieve this goal: Firstly, the project is developing and optimizing algorithms for the retrieval of hourly aerosol optical depth (AOD) maps from the Spinning Enhanced Visible and InfraRed Imager (SEVIRI) onboard of Meteosat Second Generation. As a second activity, SAMIRA aims to derive particulate matter (PM2.5) estimates from AOD data by developing robust algorithms for AOD-to-PM conversion with the support from model- and Lidar data. In a third activity, we evaluate the added value of satellite products of atmospheric composition for operational European-scale air quality mapping using geostatistics and auxiliary datasets. The additional benefit of satellite-based monitoring over existing monitoring techniques (in situ, models) is tested by combining these datasets using geostatistical methods and demonstrated for nitrogen dioxide (NO2), sulphur dioxide (SO2), and aerosol optical depth/particulate matter. As a fourth activity, the project is developing novel algorithms for downscaling coarse

  14. Assessing satellite AOD based and WRF/CMAQ output PM2.5 estimators

    Science.gov (United States)

    Cordero, Lina; Wu, Yonghua; Gross, Barry M.; Moshary, Fred

    2013-05-01

    Fine particulate matter measurements (PM2.5) are essential for air quality monitoring and related public health; however, the shortage of reliable measurmennts constrains researchers to use other means for obtaining reliable estimates over large scales. In particular, model forecasters and satellite community use their respective products to develop ground particulate matter estimations but few experiments have explored how the remote sensing approaches compare to the high resolution models. . In this paper we focus on studying the performance of the Moderate Resolution Imaging Spectroradiometer (MODIS) and the Geostationary Operational Environmental Satellites (GOES) regression based estimates in comparison to more direct bias corrected outputs from the Community Multiscale Air Quality (CMAQ) model, We use a two-year dataset (2005-2006) and apply urban, season and hour filters to illustrate the agreement between estimated and in-situ measured fine particulate matter from the New York State Department of Environmental Conservation (NYSDEC). We first begin by analyzing the correspondence between ground aerosol optical depth (AOD) measurements from an AERONET (AErosol RObotic NETwork) Cimel sun/sky radiometer with both satellite and model products in one urban location; we show that satellite readings perform better than model outputs, especially during the summer (RMODIS>=0.65, RCMAQ>=0.37). This is a clear symptom of the difficulty in the models to properly model realistic optical properties. We then turn to a direct assessment of PM2.5 presenting individual comparisons between ground PM2.5 measurements with satellite/model predictions and demonstrate the higher accuracy from model estimations (RurbanMODIS >= 0.74, RurbanCMAQ >= 0.77; Rnon-urbanMODIS >= 0.48, Rnon-urbanCMAQ >= 0.78). In general, we find that the bias corrected CMAQ estimates are superior to satellite based estimators except at very high resolution. Finally, we show that when using both model and

  15. Aerosol Number Concentrations and Visibility during Dense Fog over a Subtropical Urban Site

    Directory of Open Access Journals (Sweden)

    Manju Mohan

    2014-01-01

    Full Text Available There is now enough evidence of greater frequencies and extent of fog formation in urban areas. These could easily be linked to rapid increase in aerosol number concentration (ANC peculiar to polluted urban environments. It is therefore pertinent to study ANC and visibility alongside the meteorological parameters in order to investigate the relationships which may possibly exist between these parameters especially during foggy conditions. This study based on field measurements of ANC for aerosol spectrum varying from 0.3 µm to 20 µm attempts to investigates whether a threshold ANC could be associated with a given visibility range during low visibility conditions including dense fog episodes. Thus, the present work explores relationship between ANC size spectrum and visibility (100 m–4500 m in a polluted urban environment in India with specific reference to episodes of dense fog during winter period. The study depicts a threshold minimum value of ANC during foggy conditions. A power relationship between ANC and visibility is obtained. Further, aerosol number distribution and size distribution function are also studied and empirical relation is compared with previous studies. Further work is suggested to strengthen the findings presented here.

  16. A Positioning System based on Communication Satellites and the Chinese Area Positioning System (CAPS)

    Science.gov (United States)

    Ai, Guo-Xiang; Shi, Hu-Li; Wu, Hai-Tao; Yan, Yi-Hua; Bian, Yu-Jing; Hu, Yong-Hui; Li, Zhi-Gang; Guo, Ji; Xian-DeCai

    2008-12-01

    The Chinese Area Positioning System (CAPS) is a positioning system based on satellite communication that is fundamentally different from the 3``G'' (GPS, GLONASS and GALILEO) systems. The latter use special-purpose navigation satellites to broadcast navigation information generated on-board to users, while the CAPS transfers ground-generated navigation information to users via the communication satellite. In order to achieve accurate Positioning, Velocity and Time (PVT), the CAPS employs the following strategies to overcome the three main obstacles caused by using the communication satellite: (a) by real-time following-up frequency stabilization to achieve stable frequency; (b) by using a single carrier in the transponder with 36 MHz band-width to gain sufficient power; (c) by incorporating Decommissioned Geostationary Orbit communication satellite (DGEO), barometric pressure and Inclined Geostationary Orbit communication satellite (IGSO) to achieve the 3-D positioning. Furthermore, the abundant transponders available on DGEO can be used to realize the large capacity of communication as well as the integrated navigation and communication. With the communication functions incorporated, five new functions appear in the CAPS: (1) combination of navigation and communication; (2) combination of navigation and high accuracy orbit measurement; (3) combination of navigation message and wide/local area differential processing; (4) combination of the switching of satellites, frequencies and codes; and (5) combination of the navigation message and the barometric altimetry. The CAPS is thereby labelled a PVT5C system of high accuracy. In order to validate the working principle and the performance of the CAPS, a trial system was established in the course of two years at a cost of about 20 million dollars. The trial constellation consists of two GEO satellites located at E87.5° and E110.5°, two DGEOs located at E130° and E142°, as well as barometric altimetry as a virtual

  17. A Positioning System based on Communication Satellites and the Chinese Area Positioning System (CAPS)

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The Chinese Area Positioning System (CAPS) is a positioning system based on satellite communication that is fundamentally different from the 3"G" (GPS, GLONASS and GALILEO) systems. The latter use special-purpose navigation satellites to broadcast navi-gation information generated on-board to users, while the CAPS transfers ground-generated navigation information to users via the communication satellite. In order to achieve accurate Positioning, Velocity and Time (PVT), the CAPS employs the following strategies to over-come the three main obstacles caused by using the communication satellite: (a) by real-time following-up frequency stabilization to achieve stable frequency; (b) by using a single carrier in the transponder with 36 MHz band-width to gain sufficient power; (c) by incorporating Decommissioned Geostationary Orbit communication satellite (DGEO), barometric pressure and Inclined Geostationary Orbit communication satellite (IGSO) to achieve the 3-D posi-tioning. Furthermore, the abundant transponders available on DGEO can be used to realize the large capacity of communication as well as the integrated navigation and communication. With the communication functions incorporated, five new functions appear in the CAPS: (1) combination of navigation and communication; (2) combination of navigation and high accu-racy orbit measurement; (3) combination of navigation message and wide/local area differen-tial processing; (4) combination of the switching of satellites, frequencies and codes; and (5) combination of the navigation message and the barometric altimetry. The CAPS is thereby labelled a PVT5C system of high accuracy. In order to validate the working principle and the performance of the CAPS, a trial system was established in the course of two years at a cost of about 20 million dollars. The trial constellation consists of two GEO satellites located at E87.5°and E110.5°, two DGEOs located at E130° and E142°, as well as barometric altimetry as a virtual

  18. Satellite single-axis attitude determination based on Automatic Dependent Surveillance - Broadcast signals

    Science.gov (United States)

    Zhou, Kaixing; Sun, Xiucong; Huang, Hai; Wang, Xinsheng; Ren, Guangwei

    2017-10-01

    The space-based Automatic Dependent Surveillance - Broadcast (ADS-B) is a new technology for air traffic management. The satellite equipped with spaceborne ADS-B system receives the broadcast signals from aircraft and transfers the message to ground stations, so as to extend the coverage area of terrestrial-based ADS-B. In this work, a novel satellite single-axis attitude determination solution based on the ADS-B receiving system is proposed. This solution utilizes the signal-to-noise ratio (SNR) measurement of the broadcast signals from aircraft to determine the boresight orientation of the ADS-B receiving antenna fixed on the satellite. The basic principle of this solution is described. The feasibility study of this new attitude determination solution is implemented, including the link budget and the access analysis. On this basis, the nonlinear least squares estimation based on the Levenberg-Marquardt method is applied to estimate the single-axis orientation. A full digital simulation has been carried out to verify the effectiveness and performance of this solution. Finally, the corresponding results are processed and presented minutely.

  19. Satellite-based climate information within the WMO RA VI Regional Climate Centre on Climate Monitoring

    Science.gov (United States)

    Obregón, A.; Nitsche, H.; Körber, M.; Kreis, A.; Bissolli, P.; Friedrich, K.; Rösner, S.

    2014-05-01

    The World Meteorological Organization (WMO) established Regional Climate Centres (RCCs) around the world to create science-based climate information on a regional scale within the Global Framework for Climate Services (GFCS). The paper introduces the satellite component of the WMO Regional Climate Centre on Climate Monitoring (RCC-CM) for Europe and the Middle East. The RCC-CM product portfolio is based on essential climate variables (ECVs) as defined by the Global Climate Observing System (GCOS), spanning the atmospheric (radiation, clouds, water vapour) and terrestrial domains (snow cover, soil moisture). In the first part, the input data sets are briefly described, which are provided by the EUMETSAT (European Organisation for the Exploitation of Meteorological Satellites) Satellite Application Facilities (SAF), in particular CM SAF, and by the ESA (European Space Agency) Climate Change Initiative (CCI). In the second part, the derived RCC-CM products are presented, which are divided into two groups: (i) operational monitoring products (e.g. monthly means and anomalies) based on near-real-time environmental data records (EDRs) and (ii) climate information records (e.g. climatologies, time series, trend maps) based on long-term thematic climate data records (TCDRs) with adequate stability, accuracy and homogeneity. The products are provided as maps, statistical plots and gridded data, which are made available through the RCC-CM website (www.dwd.de/rcc-cm).

  20. Satellite-based monitoring of particulate matter pollution at very high resolution: the HOTBAR method

    Science.gov (United States)

    Wilson, Robin; Milton, Edward; Nield, Joanna

    2016-04-01

    Particulate matter air pollution is a major health risk, and is responsible for millions of premature deaths each year. Concentrations tend to be highest in urban areas - particularly in the mega-cities of rapidly industrialising countries, where there are limited ground monitoring networks. Satellite-based monitoring has been used for many years to assess regional-scale trends in air quality, but currently available satellite products produce data at 1-10km resolution: too coarse to discern the small-scale patterns of sources and sinks seen in urban areas. Higher-resolution satellite products are required to provide accurate assessments of particulate matter concentrations in these areas, and to allow analysis of localised air quality effects on health. The Haze Optimized Transform-based Aerosol Retrieval (HOTBAR) method is a novel method which provides estimates of PM2.5 concentrations from high-resolution (approximately 30m) satellite imagery. This method is designed to work over a wide range of land covers and performs well over the complex land-cover mosaic found in urban areas. It requires only standard visible and near-infrared data, making it applicable to a range of data from sensors such as Landsat, SPOT and Sentinel-2. The method is based upon an extension of the Haze Optimized Transform (HOT), which was originally designed for assessing areas of thick haze in satellite imagery. This was done by calculating a 'haziness' value for each pixel in an image as the distance from a 'Clear Line' in feature space, defined by the high correlation between visible bands. Here, we adapt the HOT method and use it to estimate Aerosol Optical Thickness (a measure of the column-integrated haziness of the atmosphere) instead, from which PM2.5 concentrations can then be estimated. Significant extensions to the original HOT method include Monte Carlo estimation of the 'Clear Line', object-based correction for land cover, and estimation of AOT from the haziness values

  1. Error analysis for satellite gravity field determination based on two-dimensional Fourier methods

    CERN Document Server

    Cai, Lin; Hsu, Houtse; Gao, Fang; Zhu, Zhu; Luo, Jun

    2012-01-01

    The time-wise and space-wise approaches are generally applied to data processing and error analysis for satellite gravimetry missions. But both the approaches, which are based on least-squares collocation, address the whole effect of measurement errors and estimate the resolution of gravity field models mainly from a numerical point of indirect view. Moreover, requirement for higher accuracy and resolution gravity field models could make the computation more difficult, and serious numerical instabilities arise. In order to overcome the problems, this study focuses on constructing a direct relationship between power spectral density of the satellite gravimetry measurements and coefficients of the Earth's gravity potential. Based on two-dimensional Fourier transform, the relationship is analytically concluded. By taking advantage of the analytical expression, it is efficient and distinct for parameter estimation and error analysis of missions. From the relationship and the simulations, it is analytically confir...

  2. Coherent receiving efficiency in satellite-ground coherent laser communication system based on analysis of polarization

    Science.gov (United States)

    Hao, Shiqi; Zhang, Dai; Zhao, Qingsong; Wang, Lei; Zhao, Qi

    2017-06-01

    Aimed at analyzing the coherent receiving efficiency of a satellite-ground coherent laser communication system, polarization state of the received light is analyzed. We choose the circularly polarized, partially coherent laser as transmitted light source. The analysis process includes 3 parts. Firstly, an theoretical model to analyze received light's polarization state is constructed based on Gaussian-Schell model (GSM) and cross spectral density function matrix. Then, analytic formulas to calculate coherent receiving efficiency are derived in which both initial ellipticity modification and deflection angle between polarization axes of the received light and the intrinsic light are considered. At last, numerical simulations are operated based on our study. The research findings investigate variations of polarization state and obtain analytic formulas to calculate the coherent receiving efficiency. Our study has theoretical guiding significances in construction and optimization of satellite-ground coherent laser communication system.

  3. Multiagent Attitude Control System for Satellites Based in Momentum Wheels and Event-Driven Synchronization

    Science.gov (United States)

    Garcia, Juan L.; Moreno, Jose Sanchez

    2012-12-01

    Attitude control is a requirement always present in spacecraft design. Several kinds of actuators exist to accomplish this control, being momentum wheels one of the most employed. Usually satellites carry redundant momentum wheels to handle any possible single failure, but the controller remains as a single centralized element, posing problems in case of failures. In this work a decentralized agent-based event-driven algorithm for attitude control is presented as a possible solution. Several agents based in momentum wheels will interact among them to accomplish the satellite control. A simulation environment has been developed to analyze the behavior of this architecture. This environment has been made available through the web page http://www.dia.uned.es.

  4. Massive information sharing among global data centers based on satellite laser communication

    Science.gov (United States)

    Yi, Longteng; Li, Cong; Liu, Naijin

    2015-10-01

    With the development of big data and information globalization, the requirements of massive information transmitting and sharing among data centers are expanding, especially among those data centers which are extremely far away from each other. In the above field, conventional optical fiber transmission faces many problems such as complex networking, poor security, long node switching delay, high lease and maintain cost and low migration flexibility. Besides, in the near future, data centers may tend to be built in the remote Polar Regions or on the sea for natural cooling. For the above situation, sharing the massive information among global data centers based on satellite laser communication is proposed in this paper. This proposal includes advantage analysis, research of restraining atmosphere interference, etc. At last, by comparison with conventional technology, the research result shows that massive information transmitting and sharing among global data centers based on satellite laser communication has far reaching application potential.

  5. Numerical simulation of radiation fog in complex terrain

    Science.gov (United States)

    Zhang, X.; Musson-Genon, L.; Carissimo, B.; Dupont, E.

    2009-09-01

    The interest for micro-scale modeling of the atmosphere is growing for environmental applications related, for example, to energy production, transport and urban development. The turbulence in the stable layers where pollutant dispersion is low and can lead to strong pollution events. This could be further complicated by the presence of clouds or fog and is specifically difficult in urban or industrial area due to the presence of buildings. In this context, radiation fog formation and dissipation over complex terrain were therefore investigated with a state-of-the-art model. This study is divided into two phases. The first phase is a pilot stage, which consist of employing a database from the ParisFog campaign which took place in the south of Paris during winter 2006-07 to assess the ability of the cloud model to reproduce the detailed structure of radiation fog. The second phase use the validated model for the study of influence of complex terrain on fog evolution. Special attention is given to the detailed and complete simulations and validation technique used is to compare the simulated results using the 3D cloud model of computational fluid dynamical software Code_Saturne with one of the best collected in situ data during the ParisFog campaign. Several dynamical, microphysical parameterizations and simulation conditions have been described. The resulting 3D cloud model runs at a horizontal resolution of 30 m and a vertical resolution comparable to the 1D model. First results look very promising and are able to reproduce the spatial distribution of fog. The analysis of the behavior of the different parameterized physical processes suggests that the subtle balance between the various processes is achieved.

  6. Satellite-based technique for nowcasting of thunderstorms over Indian region

    Indian Academy of Sciences (India)

    Suman Goyal; Ashish Kumar; M Mohapatra; L S Rathore; S K Dube; Rahul Saxena; R K Giri

    2017-08-01

    India experiences severe thunderstorms during the months, March–June. But these systems are not predicted well, mainly due to the absence of mesoscale observational network over Indian region and the expert system. As these are short lived systems, the nowcast is attempted worldwide based on satellite and radar observations. Due to inadequate radar network, satellite plays the dominant role for nowcast of these thunderstorms. In this study, a nowcast based algorithm ForTracc developed by Vila et al. (Weather Forecast 23:233–245, 2008) has been examined over the Indian region using Infrared Channel (10.8 μm) of INSAT-3D for prediction of Mesoscale Convective Systems (MCS). In this technique, the current location and intensity in terms of Cloud Top Brightness Temperature (CTBT) of the MCS are extrapolated. The purpose of this study is to validate this satellite-based nowcasting technique for Convective Cloud Clusters that helps in optimum utilization of satellite data and improve the nowcasting. The model could predict reasonably the minimum CTBT of the convective cell with average absolute error (AAE) of <7 K for different lead periods (30–180 min). However, it was underestimated for all the lead periods of forecasts. The AAE in the forecasts of size of the cluster varies from about 3×104 km2 for 30-min forecast to 7×104 km2 for 120-min forecast. The mean absolute error in prediction of size is above 31–38% of actual size for different lead periods of forecasts from 30 to 180 min. There is over estimation in prediction of size for 30 and 60 min forecasts (17% and 2.6% of actual size of the cluster, respectively) and underestimation in 90 to 180-min forecasts (–2.4% to –28%). The direct position error (DPE) based on the location of minimum CTBT ranges from 70 to 144 km for 30–180-min forecast respectively.

  7. Environmental evaluation of the forest of Mt. Fuji, based on multiple satellite data

    Energy Technology Data Exchange (ETDEWEB)

    Shiosaka, K.; Konta, F.; Nishikawa, H. (The Inst. of Regional Environ. Planning, Shizuoka (Japan) Shizuoka Univ., Shizuoka (Japan) Nippon Univ., Narashino (Japan))

    1994-03-01

    Evaluation of environmental roles of the forest of Mt. Fuji and estimation of deposition of sulfur dioxide on the leaves of Japanese cypress (Chamaecyparis obtusa) were done based on satellite data. The evaluation suggests that artificial Japanese cypress forests, which occupy the largest area among vegetations of Mt. Fuji, have problems concerning environmental role of storing of soil water, and that the result of the estimation indicates an uneven distribution of sulfur dioxide deposition.

  8. Environmental evaluation of the forest of MT Fuji, based on multiple satellite data