WorldWideScience

Sample records for radar sea clutter

  1. Sea clutter scattering, the K distribution and radar performance

    CERN Document Server

    Ward, Keith; Watts, Simon

    2013-01-01

    Sea Clutter: Scattering, the K Distribution and Radar Performance, 2nd Edition gives an authoritative account of our current understanding of radar sea clutter. Topics covered include the characteristics of radar sea clutter, modelling radar scattering by the ocean surface, statistical models of sea clutter, the simulation of clutter and other random processes, detection of small targets in sea clutter, imaging ocean surface features, radar detection performance calculations, CFAR detection, and the specification and measurement of radar performance. The calculation of the performance of pract

  2. Specification for a standard radar sea clutter model

    Science.gov (United States)

    Paulus, Richard A.

    1990-09-01

    A model for the average sea clutter radar cross section is proposed for the Oceanographic and Atmospheric Master Library. This model is a function of wind speed (or sea state), wind direction relative to the antenna, refractive conditions, radar antenna height, frequency, polarization, horizontal beamwidth, and compressed pulse length. The model is fully described, a FORTRAN 77 computer listing is provided, and test cases are given to demonstrate the proper operation of the program.

  3. Inversion for atmosphere duct parameters using real radar sea clutter

    International Nuclear Information System (INIS)

    Sheng Zheng; Fang Han-Xian

    2012-01-01

    This paper addresses the problem of estimating the lower atmospheric refractivity (M profile) under nonstandard propagation conditions frequently encountered in low altitude maritime radar applications. The vertical structure of the refractive environment is modeled using five parameters and the horizontal structure is modeled using five parameters. The refractivity model is implemented with and without a priori constraint on the duct strength as might be derived from soundings or numerical weather-prediction models. An electromagnetic propagation model maps the refractivity structure into a replica field. Replica fields are compared with the observed clutter using a squared-error objective function. A global search for the 10 environmental parameters is performed using genetic algorithms. The inversion algorithm is implemented on the basis of S-band radar sea-clutter data from Wallops Island, Virginia (SPANDAR). Reference data are from range-dependent refractivity profiles obtained with a helicopter. The inversion is assessed (i) by comparing the propagation predicted from the radar-inferred refractivity profiles with that from the helicopter profiles, (ii) by comparing the refractivity parameters from the helicopter soundings with those estimated. This technique could provide near-real-time estimation of ducting effects. (geophysics, astronomy, and astrophysics)

  4. Effects of Compound K-Distributed Sea Clutter on Angle Measurement of Wideband Monopulse Radar

    Directory of Open Access Journals (Sweden)

    Hong Zhu

    2017-01-01

    Full Text Available The effects of compound K-distributed sea clutter on angle measurement of wideband monopulse radar are investigated in this paper. We apply the conditional probability density function (pdf of monopulse ratio (MR error to analyze these effects. Based on the angle measurement procedure of the wideband monopulse radar, this conditional pdf is first deduced in detail for the case of compound K-distributed sea clutter plus noise. Herein, the spatial correlation of the texture components for each channel clutter and the correlation of the texture components between the sum and difference channel clutters are considered, and two extreme situations for each of them are tackled. Referring to the measured sea clutter data, angle measurement performances in various K-distributed sea clutter plus noise circumstances are simulated, and the effects of compound K-distributed sea clutter on angle measurement are discussed.

  5. Discriminating Sea Spikes in Incoherent Radar Measurements of Sea Clutter

    Science.gov (United States)

    2008-03-01

    het detecteren echter niet te verwachten dat bet gebruik van sea spikes te onderzoeken. Een van deze modellen zal leiden tot een Auteur (s) dergelijk...report I TNO-DV 2008 A067 6/33 Abbreviations CFAR Constant False-Alarm Rate CST Composite Surface Theory FFT Fast Fourier Transform PDF Probability Density...described by the composite surface theory (CST). This theory describes the sea surface as small Bragg-resonant capillary waves riding on top of

  6. Detection of Weather Radar Clutter

    DEFF Research Database (Denmark)

    Bøvith, Thomas

    2008-01-01

    classification and use a range of different techniques and input data. The first method uses external information from multispectral satellite images to detect clutter. The information in the visual, near-infrared, and infrared parts of the spectrum can be used to distinguish between cloud and cloud-free areas......Weather radars provide valuable information on precipitation in the atmosphere but due to the way radars work, not only precipitation is observed by the weather radar. Weather radar clutter, echoes from non-precipitating targets, occur frequently in the data, resulting in lowered data quality....... Especially in the application of weather radar data in quantitative precipitation estimation and forecasting a high data quality is important. Clutter detection is one of the key components in achieving this goal. This thesis presents three methods for detection of clutter. The methods use supervised...

  7. RCS Matrix Studies of Sea Clutter

    Science.gov (United States)

    1981-03-01

    clutter and sea clutter with targets. The study was motivated in part by the requirement to improving radar detect- ability of targets in sea clutter...ISO0 M DatiA 10111t. Sol jl 0 50 S SI (1 no 0 905 1 01 tV i VI i h WII 1111 ’uhlti .11 ŕ pS4 IV VIIIr OF -- LB -18 lob~l~ *- .4 - L it V1 1 I l a

  8. Realtime generation of K-Distributed sea clutter for hardware in the loop radar evaluation

    CSIR Research Space (South Africa)

    Van der Merwe, Johannes R

    2016-10-01

    Full Text Available This paper proposes a practical implementation for the generation of real-time K-Distributed correlated sea-clutter in firmware. The method uses a dual cumulative distribution function (CDF) based look-up method to transpose a complex uniformly...

  9. Maritime target and sea clutter measurements with a coherent Doppler polarimetric surveillance radar

    NARCIS (Netherlands)

    Smith, A.J.E.; Gelsema, S.J.; Kester, L.J.H.M.; Melief, H.W.; Premel Cabic, G.; Theil, A.; Woudenberg, E.

    2002-01-01

    Doppler polarimetry in a surveillance radar for the maritime surface picture is considered. This radar must be able to detect low-RCS targets in littoral environments. Measurements on such targets have been conducted with a coherent polarimetric measurement radar in March 2001 and preliminary

  10. Artificial Neural Network-Based Clutter Reduction Systems for Ship Size Estimation in Maritime Radars

    Directory of Open Access Journals (Sweden)

    M. P. Jarabo-Amores

    2010-01-01

    Full Text Available The existence of clutter in maritime radars deteriorates the estimation of some physical parameters of the objects detected over the sea surface. For that reason, maritime radars should incorporate efficient clutter reduction techniques. Due to the intrinsic nonlinear dynamic of sea clutter, nonlinear signal processing is needed, what can be achieved by artificial neural networks (ANNs. In this paper, an estimation of the ship size using an ANN-based clutter reduction system followed by a fixed threshold is proposed. High clutter reduction rates are achieved using 1-dimensional (horizontal or vertical integration modes, although inaccurate ship width estimations are achieved. These estimations are improved using a 2-dimensional (rhombus integration mode. The proposed system is compared with a CA-CFAR system, denoting a great performance improvement and a great robustness against changes in sea clutter conditions and ship parameters, independently of the direction of movement of the ocean waves and ships.

  11. Statistical problems with weather-radar images, I: Clutter identification

    International Nuclear Information System (INIS)

    Fernandez-Duran, Juan-Jose; Upton, Graham

    2003-01-01

    A Markov Chain Monte Carlo (MCMC) procedure is presented for the identification of clutter in weather-radar images. The key attributes of the image are the spatial coherence of the areas of clutter (noise) and cloud and the high spatial autocorrelation of the values in areas of cloud. A form of simulated annealing provides the possibility of fast clutter removal

  12. Wind turbine clutter mitigation in coastal UHF radar.

    Science.gov (United States)

    Yang, Jing; Pan, Chao; Wang, Caijun; Jiang, Dapeng; Wen, Biyang

    2014-01-01

    Coastal UHF radar provides a unique capability to measure the sea surface dynamic parameters and detect small moving targets, by exploiting the low energy loss of electromagnetic waves propagating along the salty and good conducting ocean surface. It could compensate the blind zone of HF surface wave radar at close range and reach further distance than microwave radars. However, its performance is susceptible to wind turbines which are usually installed on the shore. The size of a wind turbine is much larger than the wavelength of radio waves at UHF band, which results in large radar cross section. Furthermore, the rotation of blades adds time-varying Doppler frequency to the clutter and makes the suppression difficult. This paper proposes a mitigation method which is based on the specific periodicity of wind turbine clutter and performed mainly in the time-frequency domain. Field experimental data of a newly developed UHF radar are used to verify this method, and the results prove its effectiveness.

  13. Adaptation of Rejection Algorithms for a Radar Clutter

    Directory of Open Access Journals (Sweden)

    D. Popov

    2017-09-01

    Full Text Available In this paper, the algorithms for adaptive rejection of a radar clutter are synthesized for the case of a priori unknown spectral-correlation characteristics at wobbulation of a repetition period of the radar signal. The synthesis of algorithms for the non-recursive adaptive rejection filter (ARF of a given order is reduced to determination of the vector of weighting coefficients, which realizes the best effectiveness index for radar signal extraction from the moving targets on the background of the received clutter. As the effectiveness criterion, we consider the averaged (over the Doppler signal phase shift improvement coefficient for a signal-to-clutter ratio (SCR. On the base of extreme properties of the characteristic numbers (eigennumbers of the matrices, the optimal vector (according to this criterion maximum is defined as the eigenvector of the clutter correlation matrix corresponding to its minimal eigenvalue. The general type of the vector of optimal ARF weighting coefficients is de-termined and specific adaptive algorithms depending upon the ARF order are obtained, which in the specific cases can be reduced to the known algorithms confirming its authenticity. The comparative analysis of the synthesized and known algorithms is performed. Significant bene-fits are established in clutter rejection effectiveness by the offered processing algorithms compared to the known processing algorithms.

  14. 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

    This contribution presents the initial results from experiments with detection of weather radar clutter by information fusion with satellite based nowcasting products. Previous studies using information fusion of weather radar data and first generation Meteosat imagery have shown promising results...... 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...

  15. Adaptive sidelobe control for clutter rejection of atmospheric radars

    Directory of Open Access Journals (Sweden)

    K. Kamio

    2004-11-01

    Full Text Available Clutter rejection is among the most important issues in radar signal processing, for which the adaptive antenna technique can be a powerful means. Compared to other applications of the adaptive antenna, however, atmospheric radars require strict conditions, which have prevented application of this technique; the main antenna beam pattern should not be altered since the target region is defined by its shape. In particular, the loss of the antenna gain should be kept to no more than about 0.5dB, in order to maintain the high sensitivity of the system. Also, clutter from surrounding mountains is often stronger than the desired weak scattering from atmospheric turbulence. We introduce a new algorithm which satisfies the above conditions, and confirms its capability by applying it to actual data taken by the MU radar. This paper presents the first report that demonstrates the effectiveness of the adaptive antenna technique in atmospheric radar applications. Despite the fact that no information is given on the spectral features of the desired and undesired signals, only the clutter echoes from surrounding mountains were effectively cancelled without affecting the desired echoes from atmospheric turbulence.

  16. Mars radar clutter and surface roughness characteristics from MARSIS data

    Science.gov (United States)

    Campbell, Bruce A.; Schroeder, Dustin M.; Whitten, Jennifer L.

    2018-01-01

    Radar sounder studies of icy, sedimentary, and volcanic settings can be affected by reflections from surface topography surrounding the sensor nadir location. These off-nadir ;clutter; returns appear at similar time delays to subsurface echoes and complicate geologic interpretation. Additionally, broadening of the radar echo in delay by surface returns sets a limit on the detectability of subsurface interfaces. We use MARSIS 4 MHz data to study variations in the nadir and off-nadir clutter echoes, from about 300 km to 1000 km altitude, R, for a wide range of surface roughness. This analysis uses a new method of characterizing ionospheric attenuation to merge observations over a range of solar zenith angle and date. Mirror-like reflections should scale as R-2, but the observed 4 MHz nadir echoes often decline by a somewhat smaller power-law factor because MARSIS on-board processing increases the number of summed pulses with altitude. Prior predictions of the contributions from clutter suggest a steeper decline with R than the nadir echoes, but in very rough areas the ratio of off-nadir returns to nadir echoes shows instead an increase of about R1/2 with altitude. This is likely due in part to an increase in backscatter from the surface as the radar incidence angle at some round-trip time delay declines with increasing R. It is possible that nadir and clutter echo properties in other planetary sounding observations, including RIME and REASON flyby data for Europa, will vary in the same way with altitude, but there may be differences in the nature and scale of target roughness (e.g., icy versus rocky surfaces). We present global maps of the ionosphere- and altitude-corrected nadir echo strength, and of a ;clutter; parameter based on the ratio of off-nadir to nadir echoes. The clutter map offers a view of surface roughness at ∼75 m length scale, bridging the spatial-scale gap between SHARAD roughness estimates and MOLA-derived parameters.

  17. Reducing Surface Clutter in Cloud Profiling Radar Data

    Science.gov (United States)

    Tanelli, Simone; Pak, Kyung; Durden, Stephen; Im, Eastwood

    2008-01-01

    An algorithm has been devised to reduce ground clutter in the data products of the CloudSat Cloud Profiling Radar (CPR), which is a nadir-looking radar instrument, in orbit around the Earth, that measures power backscattered by clouds as a function of distance from the instrument. Ground clutter contaminates the CPR data in the lowest 1 km of the atmospheric profile, heretofore making it impossible to use CPR data to satisfy the scientific interest in studying clouds and light rainfall at low altitude. The algorithm is based partly on the fact that the CloudSat orbit is such that the geodetic altitude of the CPR varies continuously over a range of approximately 25 km. As the geodetic altitude changes, the radar timing parameters are changed at intervals defined by flight software in order to keep the troposphere inside a data-collection time window. However, within each interval, the surface of the Earth continuously "scans through" (that is, it moves across) a few range bins of the data time window. For each radar profile, only few samples [one for every range-bin increment ((Delta)r = 240 m)] of the surface-clutter signature are available around the range bin in which the peak of surface return is observed, but samples in consecutive radar profiles are offset slightly (by amounts much less than (Delta)r) with respect to each other according to the relative change in geodetic altitude. As a consequence, in a case in which the surface area under examination is homogenous (e.g., an ocean surface), a sequence of consecutive radar profiles of the surface in that area contains samples of the surface response with range resolution (Delta)p much finer than the range-bin increment ((Delta)p 10 dB and a reduction of the contaminated altitude over ocean from about 1 km to about 0.5 km (over the ocean). The algorithm has been embedded in CloudSat L1B processing as of Release 04 (July 2007), and the estimated flat surface clutter is removed in L2B-GEOPROF product from the

  18. Ground clutter cancellation in incoherent radars: solutions for EISCAT Svalbard radar

    Directory of Open Access Journals (Sweden)

    T. Turunen

    2000-09-01

    Full Text Available Incoherent scatter radars measure ionosphere parameters using modified Thomson scatter from free electrons in the target (see e.g. Hagfors, 1997. The integrated cross section of the ionospheric scatterers is extremely small and the measurements can easily be disturbed by signals returned by unwanted targets. Ground clutter signals, entering via the antenna side lobes, can render measurements at the nearest target ranges totally impossible. The EISCAT Svalbard Radar (ESR, which started measurements in 1996, suffers from severe ground clutter and the ionosphere cannot be measured in any simple manner at ranges less than about 120–150 km, depending on the modulation employed. If the target and clutter signals have different, and clearly identifiable, properties then, in principle, there are always ways to eliminate the clutter. In incoherent scatter measurements, differences in the coherence times of the wanted and unwanted signals can be used for clutter cancellation. The clutter cancellation must be applied to all modulations, usually alternating codes in modern experiments, used for shorter ranges. Excellent results have been obtained at the ESR using a simple pulse-to-pulse clutter subtraction method, but there are also other possibilities.Key words: Radio science (ionospheric physics; signal processing; instruments and techniques

  19. Cluttering

    Science.gov (United States)

    ... blood relatives who stutter or clutter. Social or vocational problems resulting from cluttering symptoms. Learning disability not ... toll-free at 800-992-9392. The Special Interest Division of the American Speech-Language-Hearing Association ...

  20. Analysis of calibrated sea clutter and boat reflectivity data at C- and X-band in South African coastal waters

    CSIR Research Space (South Africa)

    Herselman, PLR

    2007-10-01

    Full Text Available datasets of sea clutter returns at different frequencies, range resolutions, grazing angles, look angles and environmental conditions to validate the state-of-the-art sea clutter models on South African coastal seawaters. Secondly, the aim was to record... boat reflectivity datasets for a number of small boats to investigate its detectability with state-of-the-art detectors. This will lead to the development of improved detection algorithms for radar systems employing adaptive dwell times. Figure 1...

  1. Hardware in the loop simulation of arbitrary magnitude shaped correlated radar clutter

    CSIR Research Space (South Africa)

    Strydom, JJ

    2014-10-01

    Full Text Available This paper describes a simple process for the generation of arbitrary probability distributions of complex data with correlation from sample to sample, optimized for hardware in the loop radar environment simulation. Measured radar clutter is used...

  2. Surface return direction-of-arrival analysis for radar ice sounding surface clutter suppression

    DEFF Research Database (Denmark)

    Nielsen, Ulrik; Dall, Jørgen

    2015-01-01

    Airborne radar ice sounding is challenged by surface clutter masking the depth signal of interest. Surface clutter may even be prohibitive for potential space-based ice sounding radars. To some extent the radar antenna suppresses the surface clutter, and a multi-phase-center antenna in combination...... with coherent signal processing techniques can improve the suppression, in particular if the direction of arrival (DOA) of the clutter signal is estimated accurately. This paper deals with data-driven DOA estimation. By using P-band data from the ice shelf in Antarctica it is demonstrated that a varying...

  3. Coherent Surface Clutter Suppression Techniques with Topography Estimation for Multi-Phase-Center Radar Ice Sounding

    DEFF Research Database (Denmark)

    Nielsen, Ulrik; Dall, Jørgen; Kristensen, Steen Savstrup

    2012-01-01

    Radar ice sounding enables measurement of the thickness and internal structures of the large ice sheets on Earth. Surface clutter masking the signal of interest is a major obstacle in ice sounding. Algorithms for surface clutter suppression based on multi-phase-center radars are presented. These ...

  4. Advances in the testing and evaluation of airborne radar through realtime simulation of synthetic clutter

    CSIR Research Space (South Africa)

    Strydom, JJ

    2011-11-01

    Full Text Available and Evaluation of Airborne Radar through Realtime Simulation of Synthetic Clutter Presenter: Jurgen Strydom Systems Engineer & Signal Analyst Experimental EW Systems, CSIR Email: jjstrydom@csir.co.za Co-authors: Jacques Cilliers, CSIR 48th AOC Conference... environment simulation domain ? CSIR 2011 Slide 2 ? Technological advancements and challenges in the simulation of clutter for an airborne radar platform is discussed Where we are from: South Africa ? CSIR 2011 Slide 3 Health Natural Environment...

  5. Advances in the realtime simulation of synthetic clutter for radar testing and evaluation

    CSIR Research Space (South Africa)

    Strydom, JJ

    2010-10-01

    Full Text Available measures. Recent developments in processing power have allowed for a ground clutter simulation capability to be added to this list. RadaR ClutteR Simulation Radar clutter simulation is computationally expensive as a single range line can contain... and correlation functions require more processing power to simulate. RefeRenCeS [1] B. Manz, ?DRFMs Grow to Meet New Threats,? The Journal of Electronic Defense, August 2010, pp. 43-48. K-8430 [www.kashan.co.za] Advances in the Realtime Simulation...

  6. High Grazing Angle Sea-Clutter Literature Review

    Science.gov (United States)

    2013-03-01

    exact nature of this variation is complicated and involves the difference in temperature between the ocean surface and the surrounding air layer...distributions [80-83]. This work showed that the form of the optimal KK detector is extremely complicated and not feasible in a real radar system, while...the optimal Pareto detector is far simpler. Also, for coherent multi-look detection in a Pareto clutter environment, the whitening matched filter

  7. Spectral Polarimetric Features Analysis of Wind Turbine Clutter in Weather Radar

    NARCIS (Netherlands)

    Yin, J.; Krasnov, O.A.; Unal, C.M.H.; Medagli, S.; Russchenberg, H.W.J.

    2017-01-01

    Wind turbine clutter has gradually become a concern for the radar community for its increasing size and quantity worldwide. Based on the S-band polarimetric Doppler PARSAX radar measurements, this paper demonstrates the micro-Doppler features and spectral-polarimetric characteristic of wind turbine

  8. Simulation and Prediction of Weather Radar Clutter Using a Wave Propagator on High Resolution NWP Data

    DEFF Research Database (Denmark)

    Benzon, Hans-Henrik; Bovith, Thomas

    2008-01-01

    for prediction of this type of weather radar clutter is presented. The method uses a wave propagator to identify areas of potential non-standard propagation. The wave propagator uses a three dimensional refractivity field derived from the geophysical parameters: temperature, humidity, and pressure obtained from......Weather radars are essential sensors for observation of precipitation in the troposphere and play a major part in weather forecasting and hydrological modelling. Clutter caused by non-standard wave propagation is a common problem in weather radar applications, and in this paper a method...... a high-resolution Numerical Weather Prediction (NWP) model. The wave propagator is based on the parabolic equation approximation to the electromagnetic wave equation. The parabolic equation is solved using the well-known Fourier split-step method. Finally, the radar clutter prediction technique is used...

  9. Robust Adaptive Signal Processing Methods for Heterogeneous Radar Clutter Scenarios

    National Research Council Canada - National Science Library

    Rangaswamy, Muralidhar; Lin, Freeman C; Gerlach, Karl R

    2004-01-01

    .... Specifically, we present the performance of the normalized matched filter test in a background of disturbance consisting of clutter having a covariance matrix with known structure and unknown scaling...

  10. Using FDFD Technique in Two-Dimensional TE Analysis for Modeling Clutter in Wall Penetrating Radar

    Directory of Open Access Journals (Sweden)

    David Insana

    2014-01-01

    Full Text Available Finite difference frequency domain (FDFD computational electromagnetic modeling is implemented to perform a two-dimensional TEz analysis for the application of wall penetrating radar (WPR. Resolving small targets of interest, embedded in a strong clutter environment of unknown configuration, is difficult. Field interaction between clutter elements will dominate the received fields back-scattered from the scene. Removing the effects of clutter ultimately relies on the accuracy of the model. Analysis starts with a simple model that continues to build based on the dominant scattering features of the scene. FDFD provides a steady state frequency response to a discrete excitation. Taking the fast Fourier transform of the wideband response of the scene, at several external transmit/receive locations, produces 2D images of the clutter, which are used to mature the model.

  11. Simplified formulae for the estimation of offshore wind turbines clutter on marine radars.

    Science.gov (United States)

    Grande, Olatz; Cañizo, Josune; Angulo, Itziar; Jenn, David; Danoon, Laith R; Guerra, David; de la Vega, David

    2014-01-01

    The potential impact that offshore wind farms may cause on nearby marine radars should be considered before the wind farm is installed. Strong radar echoes from the turbines may degrade radars' detection capability in the area around the wind farm. Although conventional computational methods provide accurate results of scattering by wind turbines, they are not directly implementable in software tools that can be used to conduct the impact studies. This paper proposes a simple model to assess the clutter that wind turbines may generate on marine radars. This method can be easily implemented in the system modeling software tools for the impact analysis of a wind farm in a real scenario.

  12. Analysis of high resolution land clutter using an X-band radar

    CSIR Research Space (South Africa)

    Melebari, A

    2015-10-01

    Full Text Available . Measurements were performed with an X-band radar system with two instantaneous bandwidths of 40 MHz and 400 MHz. The clutter data was analyzed by fitting the amplitude Probability Distribution Function (PDF) to different distributions using the Method...

  13. Detecting and mitigating wind turbine clutter for airspace radar systems.

    Science.gov (United States)

    Wang, Wen-Qin

    2013-01-01

    It is well recognized that a wind turbine has a large radar cross-section (RCS) and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR) and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results.

  14. Detecting and Mitigating Wind Turbine Clutter for Airspace Radar Systems

    Directory of Open Access Journals (Sweden)

    Wen-Qin Wang

    2013-01-01

    Full Text Available It is well recognized that a wind turbine has a large radar cross-section (RCS and, due to the movement of the blades, the wind turbine will generate a Doppler frequency shift. This scattering behavior may cause severe interferences on existing radar systems including static ground-based radars and spaceborne or airborne radars. To resolve this problem, efficient techniques or algorithms should be developed to mitigate the effects of wind farms on radars. Herein, one transponder-based mitigation technique is presented. The transponder is not a new concept, which has been proposed for calibrating high-resolution imaging radars. It modulates the radar signal in a manner that the retransmitted signals can be separated from the scene echoes. As wind farms often occupy only a small area, mitigation processing in the whole radar operation will be redundant and cost inefficient. Hence, this paper uses a transponder to determine whether the radar is impacted by the wind farms. If so, the effects of wind farms are then mitigated with subsequent Kalman filtering or plot target extraction algorithms. Taking airborne synthetic aperture radar (SAR and pulse Doppler radar as the examples, this paper provides the corresponding system configuration and processing algorithms. The effectiveness of the mitigation technique is validated by numerical simulation results.

  15. An Improved Clutter Suppression Method for Weather Radars Using Multiple Pulse Repetition Time Technique

    Directory of Open Access Journals (Sweden)

    Yingjie Yu

    2017-01-01

    Full Text Available This paper describes the implementation of an improved clutter suppression method for the multiple pulse repetition time (PRT technique based on simulated radar data. The suppression method is constructed using maximum likelihood methodology in time domain and is called parametric time domain method (PTDM. The procedure relies on the assumption that precipitation and clutter signal spectra follow a Gaussian functional form. The multiple interleaved pulse repetition frequencies (PRFs that are used in this work are set to four PRFs (952, 833, 667, and 513 Hz. Based on radar simulation, it is shown that the new method can provide accurate retrieval of Doppler velocity even in the case of strong clutter contamination. The obtained velocity is nearly unbiased for all the range of Nyquist velocity interval. Also, the performance of the method is illustrated on simulated radar data for plan position indicator (PPI scan. Compared with staggered 2-PRT transmission schemes with PTDM, the proposed method presents better estimation accuracy under certain clutter situations.

  16. Detecting Weather Radar Clutter by Information Fusion With Satellite Images and Numerical Weather Prediction Model Output

    DEFF Research Database (Denmark)

    Bøvith, Thomas; Nielsen, Allan Aasbjerg; Hansen, Lars Kai

    2006-01-01

    A method for detecting clutter in weather radar images by information fusion is presented. Radar data, satellite images, and output from a numerical weather prediction model are combined and the radar echoes are classified using supervised classification. The presented method uses indirect...... information on precipitation in the atmosphere from Meteosat-8 multispectral images and near-surface temperature estimates from the DMI-HIRLAM-S05 numerical weather prediction model. Alternatively, an operational nowcasting product called 'Precipitating Clouds' based on Meteosat-8 input is used. A scale...

  17. Development Of Signal Detection For Radar Navigation System

    OpenAIRE

    Theingi Win Hlaing; Hla Myo Tun; Zaw Min Naing; Win Khaing Moe

    2017-01-01

    This paper aims to evaluate the performance of target detection in the presence of sea clutter. Radar detection of a background of unwanted clutter due to echoes from sea clutter or land is a problem of interest in the radar field. Radar detector has been developed by assuming the radar clutter is Gaussian distributed. However as technology emerges the radar distribution is seen to deviates from the Gaussian assumption. Thus detectors designs based on Gaussian assumption are no longer optimum...

  18. Detection of Ground Clutter from Weather Radar Using a Dual-Polarization and Dual-Scan Method

    Directory of Open Access Journals (Sweden)

    Mohammad-Hossein Golbon-Haghighi

    2016-06-01

    Full Text Available A novel dual-polarization and dual-scan (DPDS classification algorithm is developed for clutter detection in weather radar observations. Two consecutive scans of dual-polarization radar echoes are jointly processed to estimate auto- and cross-correlation functions. Discriminants are then defined and estimated in order to separate clutter from weather based on their physical and statistical properties. An optimal Bayesian classifier is used to make a decision on clutter presence from the estimated discriminant functions. The DPDS algorithm is applied to the data collected with the KOUN polarimetric radar and compared with the existing detection methods. It is shown that the DPDS algorithm yields a higher probability of detection and lower false alarm rate in clutter detection.

  19. Ship Detection in Gaofen-3 SAR Images Based on Sea Clutter Distribution Analysis and Deep Convolutional Neural Network.

    Science.gov (United States)

    An, Quanzhi; Pan, Zongxu; You, Hongjian

    2018-01-24

    Target detection is one of the important applications in the field of remote sensing. The Gaofen-3 (GF-3) Synthetic Aperture Radar (SAR) satellite launched by China is a powerful tool for maritime monitoring. This work aims at detecting ships in GF-3 SAR images using a new land masking strategy, the appropriate model for sea clutter and a neural network as the discrimination scheme. Firstly, the fully convolutional network (FCN) is applied to separate the sea from the land. Then, by analyzing the sea clutter distribution in GF-3 SAR images, we choose the probability distribution model of Constant False Alarm Rate (CFAR) detector from K-distribution, Gamma distribution and Rayleigh distribution based on a tradeoff between the sea clutter modeling accuracy and the computational complexity. Furthermore, in order to better implement CFAR detection, we also use truncated statistic (TS) as a preprocessing scheme and iterative censoring scheme (ICS) for boosting the performance of detector. Finally, we employ a neural network to re-examine the results as the discrimination stage. Experiment results on three GF-3 SAR images verify the effectiveness and efficiency of this approach.

  20. High Grazing Angle and High Resolution Sea Clutter: Correlation and Polarisation Analyses

    Science.gov (United States)

    2007-03-01

    the azimuthal correlation. The correlation between the HH and VV sea clutter data is low. A CA-CFAR ( cell average constant false-alarm rate...to calculate the power spectra of correlation profiles. The frequency interval of the traditional Discrete Fourier Transform is NT1 Hz, where N and...sea spikes, the Entropy-Alpha decomposition of sea spikes is shown in Figure 30. The process first locates spikes using a cell -average constant false

  1. SAR Imagery Simulation of Ship Based on Electromagnetic Calculations and Sea Clutter Modelling for Classification Applications

    International Nuclear Information System (INIS)

    Ji, K F; Zhao, Z; Xing, X W; Zou, H X; Zhou, S L

    2014-01-01

    Ship detection and classification with space-borne SAR has many potential applications within the maritime surveillance, fishery activity management, monitoring ship traffic, and military security. While ship detection techniques with SAR imagery are well established, ship classification is still an open issue. One of the main reasons may be ascribed to the difficulties on acquiring the required quantities of real data of vessels under different observation and environmental conditions with precise ground truth. Therefore, simulation of SAR images with high scenario flexibility and reasonable computation costs is compulsory for ship classification algorithms development. However, the simulation of SAR imagery of ship over sea surface is challenging. Though great efforts have been devoted to tackle this difficult problem, it is far from being conquered. This paper proposes a novel scheme for SAR imagery simulation of ship over sea surface. The simulation is implemented based on high frequency electromagnetic calculations methods of PO, MEC, PTD and GO. SAR imagery of sea clutter is modelled by the representative K-distribution clutter model. Then, the simulated SAR imagery of ship can be produced by inserting the simulated SAR imagery chips of ship into the SAR imagery of sea clutter. The proposed scheme has been validated with canonical and complex ship targets over a typical sea scene

  2. Polarization-Based Radar Detection in Sea Clutter

    Science.gov (United States)

    2015-02-27

    arccos- tan(0i + P) sin a Vcos2V+lan2(0~T^ (44) 0^1 = arccos tan(0j - ^) sina 7cos2a + tan2(0( -/?) (45) Proof: To see this, NF and NE are...m cos a ^’^ Vcos2 a + tan2(0i + /?) cos(0j + /?) (46) And cos ’iy = yr^^sin^^ 2 fl -. tan(0; + |S) sina Vcos2a + tan2(0( +/?) (47...Similarly, for 0^/, it can be shown that 45 Gyi = arccos tan(0j - P) sina ^Jcos^a + tan^idi-p) (48) a + tan’((9,+/9)cos(6i,+yff) Sin a cos a Figure

  3. Development Of Signal Detection For Radar Navigation System

    Directory of Open Access Journals (Sweden)

    Theingi Win Hlaing

    2017-09-01

    Full Text Available This paper aims to evaluate the performance of target detection in the presence of sea clutter. Radar detection of a background of unwanted clutter due to echoes from sea clutter or land is a problem of interest in the radar field. Radar detector has been developed by assuming the radar clutter is Gaussian distributed. However as technology emerges the radar distribution is seen to deviates from the Gaussian assumption. Thus detectors designs based on Gaussian assumption are no longer optimum for detection in non-Gaussian nature. The theory of target detection in Gaussian distributed clutter has been well established and the closed form of the detection performances can be easily obtained. However that is not the case in non-Gaussian clutter distributions. The operation of radar detection is determined by radar detection theory with different types of Swerling target models such as Swerling I II III IV and V. By using MATLAB these signal detection techniques are developed.

  4. Techniques for Clutter Suppression in the Presence of Body Movements during the Detection of Respiratory Activity through UWB Radars

    Directory of Open Access Journals (Sweden)

    Antonio Lazaro

    2014-02-01

    Full Text Available This paper focuses on the feasibility of tracking the chest wall movement of a human subject during respiration from the waveforms recorded using an impulse-radio (IR ultra-wideband radar. The paper describes the signal processing to estimate sleep apnea detection and breathing rate. Some techniques to solve several problems in these types of measurements, such as the clutter suppression, body movement and body orientation detection are described. Clutter suppression is achieved using a moving averaging filter to dynamically estimate it. The artifacts caused by body movements are removed using a threshold method before analyzing the breathing signal. The motion is detected using the time delay that maximizes the received signal after a clutter removing algorithm is applied. The periods in which the standard deviations of the time delay exceed a threshold are considered macro-movements and they are neglected. The sleep apnea intervals are detected when the breathing signal is below a threshold. The breathing rate is determined from the robust spectrum estimation based on Lomb periodogram algorithm. On the other hand the breathing signal amplitude depends on the body orientation respect to the antennas, and this could be a problem. In this case, in order to maximize the signal-to-noise ratio, multiple sensors are proposed to ensure that the backscattered signal can be detected by at least one sensor, regardless of the direction the human subject is facing. The feasibility of the system is compared with signals recorded by a microphone.

  5. Subcarrier-based Processing for Clutter Rejection in CP-OFDM Signal-based Passive Radar Using SFN Configuration (in English

    Directory of Open Access Journals (Sweden)

    Yi Jian-xin

    2013-03-01

    Full Text Available Clutter rejection is a key technique used by passive radars for target detection. Especially when using Single Frequency Network (SFN configuration, the multipath clutter and ground clutter increase several times more than during a single illuminator situation, which means that the clutter extends in both the spatial and temporal dimensions. The high amount of clutter occupies numerous degrees of freedom when conventional spatial or temporal processing is used, leading to a large array requirement, a huge computational cost, or even a complete failure. This paper investigates a novel subcarrier-based processing technique that is tailored for Orthogonal Frequency Division Multiplex (OFDM modulation with a Cyclic Prefix (CP-OFDM to avoid the abovementioned predicament. The algorithm principle is initially illustrated and followed by a discussion about the unique characteristics of Subcarrier-based Spatial Adaptive Processing (SSAP, which include the Doppler response and its unusual main-lobe clutter case. Then, the robustness is researched by evaluating the performance under relaxed basic assumptions. The conclusions are demonstrated by conducting test using simulated and real data sets.

  6. Infrared maritime target detection using a probabilistic single Gaussian model of sea clutter in Fourier domain

    Science.gov (United States)

    Zhou, Anran; Xie, Weixin; Pei, Jihong; Chen, Yapei

    2018-02-01

    For ship targets detection in cluttered infrared image sequences, a robust detection method, based on the probabilistic single Gaussian model of sea background in Fourier domain, is put forward. The amplitude spectrum sequences at each frequency point of the pure seawater images in Fourier domain, being more stable than the gray value sequences of each background pixel in the spatial domain, are regarded as a Gaussian model. Next, a probability weighted matrix is built based on the stability of the pure seawater's total energy spectrum in the row direction, to make the Gaussian model more accurate. Then, the foreground frequency points are separated from the background frequency points by the model. Finally, the false-alarm points are removed utilizing ships' shape features. The performance of the proposed method is tested by visual and quantitative comparisons with others.

  7. OPTIMAL SELECTION OF THE CA-CFAR ADJUSTMENT FACTOR FOR K POWER SEA CLUTTER WITH STATISTICAL VARIATIONS

    Directory of Open Access Journals (Sweden)

    José Raúl Machado Fernández

    2017-01-01

    Full Text Available La presencia de la señal interferente de clutter marino establece limitaciones en la calidad de la detección de radar en ambientes costeros y de alta mar. El procesador CA-CFAR es la solución clásica para detectar blancos de radar. Usualmente mantiene su factor de ajuste constante todo el período de operación. Como consecuencia, el esquema no toma en consideración las variaciones estadísticas de la señal de fondo cuando realiza la discriminación del clutter . Para resolver este problema, los autores realizaron un procesamiento intensivo de 40 millones de muestras de clutter de intensidad, generadas en computadora a través de MATLAB. Como resultado, encontraron los valores óptimos del factor de ajuste a ser aplicados para 40 posibles estados estadísticos del clutter , sugiriendo el uso de la arquitectura CA-CFAR con un factor de ajuste variable. Adicionalmente, fue llevado a cabo un ajuste de curvas, obteniéndose expresiones matemáticas que generalizan los resultados en todo el intervalo de considerado de estados estadísticos del clutter . Los experimentos se ejecutaron con un CA-CFAR de 64 celdas y apuntaron a encontrar los valores del factor de ajuste para tres probabilidades de falsa alarma comunes. La distribución K fue elegida como el modelo usado para el clutter , gracias a su amplia popularidad. Este artículo facilita el manejo de la distribución K de intensidad, evitando el uso de funciones Gamma y Bessel, comúnmente encontradas en desarrollos relacionados con el modelo K. Además, fueron cumplidos los requerimientos necesarios para construir un detector adaptativo en clutter de potencia K con conocimiento previo del parámetro de forma. Al mismo tiempo, fueron dadas varias recomendaciones para continuar el desarrollo de una solución más general que también incluirá la estimación del parámetro de forma.

  8. Performance limits for exo-clutter Ground Moving Target Indicator (GMTI) radar.

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2010-09-01

    The performance of a Ground Moving Target Indicator (GMTI) radar system depends on a variety of factors, many which are interdependent in some manner. It is often difficult to 'get your arms around' the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall GMTI radar system. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the 'seek time'.

  9. Application of a Statistical Linear Time-Varying System Model of High Grazing Angle Sea Clutter for Computing Interference Power

    Science.gov (United States)

    2017-12-08

    STATISTICAL LINEAR TIME-VARYING SYSTEM MODEL OF HIGH GRAZING ANGLE SEA CLUTTER FOR COMPUTING INTERFERENCE POWER 1. INTRODUCTION Statistical linear time...beam. We can approximate one of the sinc factors using the Dirichlet kernel to facilitate computation of the integral in (6) as follows: ∣∣∣∣sinc(WB...plotted in Figure 4. The resultant autocorrelation can then be found by substituting (18) into (28). The Python code used to generate Figures 1-4 is found

  10. The use of radar for bathymetry in shallow seas

    NARCIS (Netherlands)

    Greidanus, H.

    1997-01-01

    The bottom topography in shallow seas can be observed by air- and space borne radar. The paper reviews the radar imaging mechanism, and discusses the possibilities and limitations for practical use of radar in bathymetric applications, including the types of radar instruments available for this

  11. Improved Shape Parameter Estimation in Pareto Distributed Clutter with Neural Networks

    Directory of Open Access Journals (Sweden)

    José Raúl Machado-Fernández

    2016-12-01

    Full Text Available The main problem faced by naval radars is the elimination of the clutter input which is a distortion signal appearing mixed with target reflections. Recently, the Pareto distribution has been related to sea clutter measurements suggesting that it may provide a better fit than other traditional distributions. The authors propose a new method for estimating the Pareto shape parameter based on artificial neural networks. The solution achieves a precise estimation of the parameter, having a low computational cost, and outperforming the classic method which uses Maximum Likelihood Estimates (MLE. The presented scheme contributes to the development of the NATE detector for Pareto clutter, which uses the knowledge of clutter statistics for improving the stability of the detection, among other applications.

  12. HF Radar Sea-echo from Shallow Water

    Directory of Open Access Journals (Sweden)

    Josh Kohut

    2008-08-01

    Full Text Available HF radar systems are widely and routinely used for the measurement of ocean surface currents and waves. Analysis methods presently in use are based on the assumption of infinite water depth, and may therefore be inadequate close to shore where the radar echo is strongest. In this paper, we treat the situation when the radar echo is returned from ocean waves that interact with the ocean floor. Simulations are described which demonstrate the effect of shallow water on radar sea-echo. These are used to investigate limits on the existing theory and to define water depths at which shallow-water effects become significant. The second-order spectral energy increases relative to the first-order as the water depth decreases, resulting in spectral saturation when the waveheight exceeds a limit defined by the radar transmit frequency. This effect is particularly marked for lower radar transmit frequencies. The saturation limit on waveheight is less for shallow water. Shallow water affects second-order spectra (which gives wave information far more than first-order (which gives information on current velocities, the latter being significantly affected only for the lowest radar transmit frequencies for extremely shallow water. We describe analysis of radar echo from shallow water measured by a Rutgers University HF radar system to give ocean wave spectral estimates. Radar-derived wave height, period and direction are compared with simultaneous shallow-water in-situ measurements.

  13. DRFM Cordic Processor and Sea Clutter Modeling for Enhancing Structured False Target Synthesis

    Science.gov (United States)

    2017-09-01

    Computer ) algorithm. Mathematical modeling is used to examine the accuracy of converting a digitized radar signal I/Q sample into a corresponding five-bit...converter based on a CORDIC (Coordinate Rotation Digital Computer ) algorithm. Mathematical modeling is used to examine the accuracy of converting a...Coordinate Rotation Digital Computer , Digital Image Synthesizer, DRFM, digital radio frequency memory, electronic attack 15. NUMBER OF PAGES 137 16

  14. Mine detection using SF-GPR: A signal processing approach for resolution enhancement and clutter reduction

    DEFF Research Database (Denmark)

    Karlsen, Brian; Jakobsen, Kaj Bjarne; Larsen, Jan

    2001-01-01

    Proper clutter reduction is essential for Ground Penetrating Radar data since low signal-to-clutter ratio prevent correct detection of mine objects. A signal processing approach for resolution enhancement and clutter reduction used on Stepped-Frequency Ground Penetrating Radar (SF-GPR) data is pr....... The clutter reduction method is based on basis function decomposition of the SF-GPR time-series from which the clutter and the signal are separated....

  15. The Radar locates spills of Petroleum Sea inside

    International Nuclear Information System (INIS)

    Acantland Sylvie; De Biegert

    1996-01-01

    The satellite information is helping to the petroleum geologists to determine the potential of new petroleum reserves all over the world. Particularly, radar technology recently available is providing an increased dependability, an improved effectiveness of costs and a quicker access to the information that can be vital to detect and to supervise the petroleum spills that naturally happen. Several projects have been carrying out to evaluate the best use in the technology of the satellite information, specifically radar information for satellite, in sea inside exploration. The authors comment about of the kindness and benefits in the radar use

  16. A Model of Low Grazing Angle Sea Clutter for Coherent Radar Performance Analysis

    Science.gov (United States)

    2013-06-01

    parameters. 20 UNCLASSIFIED UNCLASSIFIED DSTO–TR–2864 Table 4: Model Parameters for Upwind and Downwind Data from Portland Bill [26] PHB /P V B PW/P H B PS/P...be modelled as PS PHB ∣ ∣ ∣ ∣ φ = Max [ 0, 19.1 ( U − 4 6 )] cosφ, = 0, 0 ≤ φ ≤ π/2, π/2 ≤ φ ≤ π (56) where U is the wind strength in metres per...roughly equal. Walker’s upwind data indicates that at 10 m/s, the ratio of PW UNCLASSIFIED 23 DSTO–TR–2864 UNCLASSIFIED to PHB is 11.5 dB, or a

  17. Joint optimization of MIMO radar waveform and biased estimator with prior information in the presence of clutter

    Directory of Open Access Journals (Sweden)

    Liu Hongwei

    2011-01-01

    Full Text Available Abstract In this article, we consider the problem of joint optimization of multi-input multi-output (MIMO radar waveform and biased estimator with prior information on targets of interest in the presence of signal-dependent noise. A novel constrained biased Cramer-Rao bound (CRB based method is proposed to optimize the waveform covariance matrix (WCM and biased estimator such that the performance of parameter estimation can be improved. Under a simplifying assumption, the resultant nonlinear optimization problem is solved resorting to a convex relaxation that belongs to the semidefinite programming (SDP class. An optimal solution of the initial problem is then constructed through a suitable approximation to an optimal solution of the relaxed one (in a least squares (LS sense. Numerical results show that the performance of parameter estimation can be improved considerably by the proposed method compared to uncorrelated waveforms.

  18. Towards Inverse Synthetic Aperture Radar (ISAR) for small sea vessels

    CSIR Research Space (South Africa)

    Abdul Gaffar, MY

    2006-12-01

    Full Text Available Aperture Radar (ISAR) for Small Sea Vessels M.Y. Abdul Gaffar Council for Scientific and Industrial Research University of Cape Town Slide 2 © CSIR 2006 www.csir.co.za What is ISAR? • Technique that produces cross range...

  19. Multitarget tracking in cluttered environment for a multistatic passive radar system under the DAB/DVB network

    Science.gov (United States)

    Shi, Yi Fang; Park, Seung Hyo; Song, Taek Lyul

    2017-12-01

    The target tracking using multistatic passive radar in a digital audio/video broadcast (DAB/DVB) network with illuminators of opportunity faces two main challenges: the first challenge is that one has to solve the measurement-to-illuminator association ambiguity in addition to the conventional association ambiguity between the measurements and targets, which introduces a significantly complex three-dimensional (3-D) data association problem among the target-measurement illuminator, this is because all the illuminators transmit the same carrier frequency signals and signals transmitted by different illuminators but reflected via the same target become indistinguishable; the other challenge is that only the bistatic range and range-rate measurements are available while the angle information is unavailable or of very poor quality. In this paper, the authors propose a new target tracking algorithm directly in three-dimensional (3-D) Cartesian coordinates with the capability of track management using the probability of target existence as a track quality measure. The proposed algorithm is termed sequential processing-joint integrated probabilistic data association (SP-JIPDA), which applies the modified sequential processing technique to resolve the additional association ambiguity between measurements and illuminators. The SP-JIPDA algorithm sequentially operates the JIPDA tracker to update each track for each illuminator with all the measurements in the common measurement set at each time. For reasons of fair comparison, the existing modified joint probabilistic data association (MJPDA) algorithm that addresses the 3-D data association problem via "supertargets" using gate grouping and provides tracks directly in 3-D Cartesian coordinates, is enhanced by incorporating the probability of target existence as an effective track quality measure for track management. Both algorithms deal with nonlinear observations using the extended Kalman filtering. A simulation study is

  20. Sea Ice Movements from Synthetic Aperture Radar

    Science.gov (United States)

    1981-12-01

    correlating these components. B-l8 These correlations are also plotted in figure l1. 5.3.3.2 AUlications of the space correlation. The spatial...aperture radar. To appear in J. of Geophys. Res. Hastings, A. D. Jr., 1971. Surface climate of the Arctic Basin. Report ETL- TR-71-5, Earth Sciences Division...Administration Grant NA50-AA-D-00015, which was funded in part by the Global Atmospheric Research Program and the Office of Climate Dynarics, Divisic

  1. Detection of small targets in a marine environment using laser radar

    NARCIS (Netherlands)

    Kunz, G.J.; Bekman, H.H.P.T.; Benoist, K.W.; Cohen, L.H.; Heuvel, J.C. van den; Putten, F.J.M.

    2005-01-01

    Small maritime targets, e.g., periscope tubes, jet skies, swimmers and small boats, are potential threats for naval ships under many conditions, but are difficult to detect with current radar systems due to their limited radar cross section and the presence of sea clutter. On the other hand,

  2. Detection of Small Sea-Surface Targets with a Search Lidar

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Bekman, H.H.P.T.; Putten, F.J.M.; Cohen, L.A.

    2007-01-01

    Naval operations in the littoral have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and low velocity, which makes them hard to detect by radar in the presence of sea clutter. Typical threats include periscopes, jet skies, FIAC’s, and speedboats.

  3. Radar Backscatter Study of Sea Ice.

    Science.gov (United States)

    1980-02-01

    CRINC/RS-TR-331-14 N END 11111 .0 W 2.0 =il I.0 i IIIB ii 2 IIIII Bill IlIIIl 8 [(25 I 4 Bi l 1.6 MICROCOPY RE SOL UTIION TEIST CHART 177 slopes...Research, 1978. 51. Continentai Shelf Data Systems, Beaufort Sea-Arctic Coast: Oceano - graphic and Climatologic Data, Vol. 1, Continental Shelf Data Systems

  4. Millimeter Wave Radar Clutter Program

    Science.gov (United States)

    1989-10-30

    94. end 1i0 G~x. A HP SSIGA ielt aMATIf Is 400110d iS tb* 0 IT F NINP sytu~ an a "si ceedkieer sai prerme t* bdiuO redi- eel-se-00i. ruleo of the...y, iny 2 (27d) We can write the phase matrix as P (9*.*S; 0A) - g1(’/)(LL) 2 + g2(W)(t,r) 2 g1(V)(r,t) 2+ g2(W~)(r,r) 2 L0 0 -g1 (𔃺)r."ŕ.) + 92(iy...r,r)(tr)0 g,())(r,t)t.L - g2(s)(rr) 2(t.r) 2 0 Using the oosine and sin law of a spherical triangle, we can write (t.t). (r,t), (r,t), and (t,r) in

  5. CFAR Detection from Noncoherent Radar Echoes Using Bayesian Theory

    Directory of Open Access Journals (Sweden)

    Wataru Suganuma

    2010-01-01

    Full Text Available We propose a new constant false alarm rate (CFAR detection method from noncoherent radar echoes, considering heterogeneous sea clutter. It applies the Bayesian theory for adaptive estimation of the local clutter statistical distribution in the cell under test. The detection technique can be readily implemented in existing noncoherent marine radar systems, which makes it particularly attractive for economical CFAR detection systems. Monte Carlo simulations were used to investigate the detection performance and demonstrated that the proposed technique provides a higher probability of detection than conventional techniques, such as cell averaging CFAR (CA-CFAR, especially with a small number of reference cells.

  6. CFAR Detection from Noncoherent Radar Echoes Using Bayesian Theory

    Directory of Open Access Journals (Sweden)

    Yamaguchi Hiroyuki

    2010-01-01

    Full Text Available Abstract We propose a new constant false alarm rate (CFAR detection method from noncoherent radar echoes, considering heterogeneous sea clutter. It applies the Bayesian theory for adaptive estimation of the local clutter statistical distribution in the cell under test. The detection technique can be readily implemented in existing noncoherent marine radar systems, which makes it particularly attractive for economical CFAR detection systems. Monte Carlo simulations were used to investigate the detection performance and demonstrated that the proposed technique provides a higher probability of detection than conventional techniques, such as cell averaging CFAR (CA-CFAR, especially with a small number of reference cells.

  7. Simulation of a weather radar display for over-water airborne radar approaches

    Science.gov (United States)

    Clary, G. R.

    1983-01-01

    Airborne radar approach (ARA) concepts are being investigated as a part of NASA's Rotorcraft All-Weather Operations Research Program on advanced guidance and navigation methods. This research is being conducted using both piloted simulations and flight test evaluations. For the piloted simulations, a mathematical model of the airborne radar was developed for over-water ARAs to offshore platforms. This simulated flight scenario requires radar simulation of point targets, such as oil rigs and ships, distributed sea clutter, and transponder beacon replies. Radar theory, weather radar characteristics, and empirical data derived from in-flight radar photographs are combined to model a civil weather/mapping radar typical of those used in offshore rotorcraft operations. The resulting radar simulation is realistic and provides the needed simulation capability for ongoing ARA research.

  8. Analysis of X-band calibrated sea clutter and small boat reflectivity at medium-to-low grazing angles

    CSIR Research Space (South Africa)

    Herselman, PL

    2008-11-01

    Full Text Available , allows the development of advanced detection and tracking algorithms, which will improve the performance of surveillance and marine navigation radar against small boats. Work presented is based on the empirical analysis of data recorded with two...

  9. Application of Statistical Linear Time-Varying System Theory to Modeling of High Grazing Angle Sea Clutter

    Science.gov (United States)

    2017-10-25

    9 3.2 Time -Frequency Power Distribution at Channel Output .................................................. 16 3.3...describes the distribution of the radar return as a function of lag τ and correlation time ∆t [1, 3]. In an airborne pulse-Doppler radar system we can...obtained by interpolating data points taken from Figure 7.13 from [37]. 3.2 Time -Frequency Power Distribution at Channel Output One of the goals of pulse

  10. Morphologie radar de fonds marins Radar Morphology of Some Sea Floors

    Directory of Open Access Journals (Sweden)

    Wadsworth A.

    2006-11-01

    Full Text Available Les radars latéraux sont des instruments de télédétection, fournissant des images de la surface terrestre survolée par pratiquement tout temps, c'est-à-dire de jour ou de nuit, par temps clair ou à travers de la brume, du brouillard, des nuages ou de la pluie. Dans le cadre de l'utilisation de ces instruments pour l'acquisition de données en mer, afin de quantifier les vagues ou la houle, des visualisations annexes, involontaires à l'origine, ont été réalisées. C'est le cas, par exemple, de certains fonds marins, que l'on peut voirlorsque quelques éléments opérationnels sont bien choisis. De plus, une certaine idée de leur morphologie peut être atteinte. Divers exemples sont présentés dans le cas de faibles fonds. Une approche des causes de cette visualisation est proposée, les grandes limites en sont fixées. Side-looking radars are remote-sensing instruments providing images of the ground surface overflown in almost all weather, i. e. day or night, with clear weather or through mist, fog, clouds or rain. These equipments, previously used to quantify sea waves and swell produced, in sonie cases, a noise which was later understood as being a signal, an expression of sea bottom features. This is the case, for example, for sonie sea floors which can be seenwhen a few operational elements have been carefully chosen. Likewise, some idea of the morphology of sea floors can be obtained. This article gives different examples for shallow depths. An approach to the causes of this visualization is proposed, and the major limitations are determined.

  11. Radar and infrared remote sensing of terrain, water resources, arctic sea ice, and agriculture

    Science.gov (United States)

    Biggs, A. W.

    1983-01-01

    Radar range measurements, basic waveforms of radar systems, and radar displays are initially described. These are followed by backscatter from several types of terrain and vegetation as a function of frequency and grazing angle. Analytical models for this backscatter include the facet models of radar return, with range-angle, velocity-range, velocity-angle, range, velocity, and angular only discriminations. Several side-looking airborne radar geometries are presented. Radar images of Arctic sea ice, fresh water lake ice, cloud-covered terrain, and related areas are presented to identify applications of radar imagery. Volume scatter models are applied to radar imagery from alpine snowfields. Short pulse ice thickness radar for subsurface probes is discussed in fresh-water ice and sea ice detection. Infrared scanners, including multispectral, are described. Diffusion of cold water into a river, Arctic sea ice, power plant discharges, volcanic heat, and related areas are presented in thermal imagery. Multispectral radar and infrared imagery are discussed, with comparisons of photographic, infrared, and radar imagery of the same terrain or subjects.

  12. Estimation of directional sea wave spectra from radar images. A Mediterranean Sea case study

    International Nuclear Information System (INIS)

    Corsini, G.; Grasso, R.; Manara, G.; Monorchio, A.

    2001-01-01

    An inversion technique for estimating sea wave directional spectra from Synthetic Aperture Radar (SAR) images is applied to a set of ERS-1 data relevant to selected Mediterranean areas. The approach followed is based on the analytical definition of the transform which maps the sea wave spectrum onto the corresponding SAR image spectrum. The solution of the inverse problem is determined through a numerical procedure which minimises a proper functional. A suitable iterative scheme is adopted, involving the use of the above transform. Although widely applied to the ocean case, the method has not been yet extensively tested widely applied to the ocean case, the method has not been yet extensively tested in smaller scale basins, as for instance the Mediterranean sea. The results obtained demonstrate the effectiveness of the numerical procedure discussed for retrieving the sea wave spectrum from SAR images. This work provides new experimental data relevant to the Mediterranean Sea, discusses the results obtained by the above inversion technique and compares them with buoy derived sea truth measurements

  13. Improved measurements of mean sea surface velocity in the Nordic Seas from synthetic aperture radar

    Science.gov (United States)

    Wergeland Hansen, Morten; Johnsen, Harald; Engen, Geir; Øie Nilsen, Jan Even

    2017-04-01

    The warm and saline surface Atlantic Water (AW) flowing into the Nordic Seas across the Greenland-Scotland ridge transports heat into the Arctic, maintaining the ice-free oceans and regulating sea-ice extent. The AW influences the region's relatively mild climate and is the northern branch of the global thermohaline overturning circulation. Heat loss in the Norwegian Sea is key for both heat transport and deep water formation. In general, the ocean currents in the Nordic Seas and the North Atlantic Ocean is a complex system of topographically steered barotropic and baroclinic currents of which the wind stress and its variability is a driver of major importance. The synthetic aperture radar (SAR) Doppler centroid shift has been demonstrated to contain geophysical information about sea surface wind, waves and current at an accuracy of 5 Hz and pixel spacing of 3.5 - 9 × 8 km2. This corresponds to a horizontal surface velocity of about 20 cm/s at 35° incidence angle. The ESA Prodex ISAR project aims to implement new and improved SAR Doppler shift processing routines to enable reprocessing of the wide swath acquisitions available from the Envisat ASAR archive (2002-2012) at higher resolution and better accuracy than previously obtained, allowing combined use with Sentinel-1 and Radarsat-2 retrievals to build timeseries of the sea surface velocity in the Nordic Seas. Estimation of the geophysical Doppler shift from new SAR Doppler centroid shift retrievals will be demonstrated, addressing key issues relating to geometric (satellite orbit and attitude) and electronic (antenna mis-pointing) contributions and corrections. Geophysical Doppler shift retrievals from one month of data in January 2010 and the inverted surface velocity in the Nordic Seas are then addressed and compared to other direct and indirect estimates of the upper ocean current, in particular those obtained in the ESA GlobCurrent project.

  14. Ku-Band radar penetration into Snow over Arctic Sea Ice

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    is the snow/air interface, whereas radar waves interact with the variable physical properties of the snow cover on the Arctic sea ice. In addition, radar elevation measurements may vary for different retracker algorithms, which determine the track point of the scattered echo power distribution. Since accurate...... knowledge of the reflection horizon is critical for sea ice thickness retrieval, validation data is necessary to investigate the penetration of radar waves into the snow for the upcoming CryoSat-2 mission. Furthermore, the combination of both optical and RF wavelengths might be used to derive snow thickness......, if radar altimeters are capable of measuring the distance to the snow-ice interface reliably. We present the results of aircraft campaigns in the Arctic with a scanning laser altimeter and the Airborne SAR/Interferometric Radar Altimeter System (ASIRAS) of the European Space Agency. The elevation...

  15. Limits to Clutter Cancellation in Multi-Aperture GMTI Data

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin W. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States); Bickel, Douglas L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2015-03-01

    Multi-aperture or multi-subaperture antennas are fundamental to Ground Moving Target Indicator (GMTI) radar systems in order to detect slow-moving targets with Doppler characteristics similar to clutter. Herein we examine the performance of several subaperture architectures for their clutter cancelling performance. Significantly, more antenna phase centers isn’t always better, and in fact is sometimes worse, for detecting targets.

  16. Advances in bistatic radar

    CERN Document Server

    Willis, Nick

    2007-01-01

    Advances in Bistatic Radar updates and extends bistatic and multistatic radar developments since publication of Willis' Bistatic Radar in 1991. New and recently declassified military applications are documented. Civil applications are detailed including commercial and scientific systems. Leading radar engineers provide expertise to each of these applications. Advances in Bistatic Radar consists of two major sections: Bistatic/Multistatic Radar Systems and Bistatic Clutter and Signal Processing. Starting with a history update, the first section documents the early and now declassified military

  17. Maximum Likelihood Joint Tracking and Association in Strong Clutter

    Directory of Open Access Journals (Sweden)

    Leonid I. Perlovsky

    2013-01-01

    Full Text Available We have developed a maximum likelihood formulation for a joint detection, tracking and association problem. An efficient non-combinatorial algorithm for this problem is developed in case of strong clutter for radar data. By using an iterative procedure of the dynamic logic process “from vague-to-crisp” explained in the paper, the new tracker overcomes the combinatorial complexity of tracking in highly-cluttered scenarios and results in an orders-of-magnitude improvement in signal-to-clutter ratio.

  18. Measurement of the sea surface wind speed and direction by an airborne microwave radar altimeter

    Energy Technology Data Exchange (ETDEWEB)

    Nekrassov, A. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Hydrophysik

    2001-07-01

    A pilot needs operational information about wind over sea as well as wave height to provide safety of a hydroplane landing on water. Near-surface wind speed and direction can be obtained with an airborne microwave scatterometer, radar designed for measuring the scatter characteristics of a surface. Mostly narrow-beam antennas are applied for such wind measurement. Unfortunately, a microwave narrow-beam antenna has considerable size that hampers its placing on flying apparatus. In this connection, a possibility to apply a conventional airborne radar altimeter as a scatterometer with a nadir-looking wide-beam antenna in conjunction with Doppler filtering for recovering the wind vector over sea is discussed, and measuring algorithms of sea surface wind speed and direction are proposed. The obtained results can be used for creation of an airborne radar system for operational measurement of the sea roughness characteristics and for safe landing of a hydroplane on water. (orig.)

  19. Radar equations for modern radar

    CERN Document Server

    Barton, David K

    2012-01-01

    Based on the classic Radar Range-Performance Analysis from 1980, this practical volume extends that work to ensure applicability of radar equations to the design and analysis of modern radars. This unique book helps you identify what information on the radar and its environment is needed to predict detection range. Moreover, it provides equations and data to improve the accuracy of range calculations. You find detailed information on propagation effects, methods of range calculation in environments that include clutter, jamming and thermal noise, as well as loss factors that reduce radar perfo

  20. A study of the radar backscattering from the breaking of wind waves on the sea

    International Nuclear Information System (INIS)

    Ivanov, V.A.; Yurovskij, Yu.Yu.; Malinovskij, V.V.

    2011-01-01

    The results of a field study of the relationship between radar backscattering parameters and geometrical characteristics of the wind wave breaking are presented. The radar cross-section of a whitecap is found to be proportional to the breaking crest length. It is shown that the accounting for a change of the non-Bragg scattering in the presence of an oil slick on the sea surface allows one to interpret experimental data correctly.

  1. Space-polarization Collaborative Suppression Method for Ionospheric Clutter in HFSWR

    Directory of Open Access Journals (Sweden)

    Yang Yunlong

    2016-12-01

    Full Text Available High Frequency Surface Wave Radar (HFSWR is able to receive surface target and low-flying aircraft echoes at a long-distance, but it suffers severely from ionospheric clutter. In this paper, a spacepolarization collaborative-based filter is introduced to mitigate ionospheric clutter. For parameter estimation on ionospheric clutter used for filters, a spatial parameter estimation algorithm based on compressive sensing is introduced to the DOA estimation of ionospheric clutter. In addition, a polarized parameter estimation algorithm based on statistical characteristics is proposed for ionospheric clutter in the range-Doppler spectrum. Higher estimation accuracy is achieved as a result of the range-Doppler spectrum; therefore, these two estimation algorithms enhance the performance of the space-polarization collaborative suppression method for ionospheric clutter. Experimental results of practical dual-polarized HFSWR data show the effectiveness of the two algorithms and the above mentioned filter for ionospheric clutter suppression.

  2. Optical identification of sea-mines - Gated viewing three-dimensional laser radar

    DEFF Research Database (Denmark)

    Busck, Jens

    2005-01-01

    A gated viewing high accuracy mono-static laser radar has been developed for the purpose of improving the optical underwater sea-mine identification handled by the Navy. In the final stage of the sea-mine detection, classification and identification process the Navy applies a remote operated...... vehicle for optical identification of the bottom seamine. The experimental results of the thesis indicate that replacing the conventional optical video and spotlight system applied by the Navy with the gated viewing two- and three-dimensional laser radar can improve the underwater optical sea...... of the short laser pulses (0.5 ns), the high laser pulse repetition rate (32.4 kHz), the fast gating camera (0.2 ns), the short camera delay steps (0.1 ns), the applied optical single mode fiber, and the applied algorithm for three-dimensional imaging. The gated viewing laser radar system configuration...

  3. Bubbles in Titan’s Seas: Nucleation, Growth, and RADAR Signature

    Science.gov (United States)

    Cordier, Daniel; Liger-Belair, Gérard

    2018-05-01

    In the polar regions of Titan, the main satellite of Saturn, hydrocarbon seas have been discovered by the Cassini–Huygens mission. RADAR observations have revealed surprising and transient bright areas over the Ligeia Mare surface. As suggested by recent research, bubbles could explain these strange features. However, the nucleation and growth of such bubbles, together with their RADAR reflectivity, have never been investigated. All of these aspects are critical to an actual observation. We have thus applied the classical nucleation theory to our context, and we developed a specific radiative transfer model that is appropriate for bubble streams in cryogenic liquids. According to our results, the sea bed appears to be the most plausible place for the generation of bubbles, leading to a signal comparable to observations. This conclusion is supported by thermodynamic arguments and by RADAR properties of a bubbly column. The latter are also valid in the case of bubble plumes, due to gas leaking from the sea floor.

  4. Wind Profiling Radar

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Clutter present in radar return signals as used for wind profiling is substantially removed by carrying out a Daubechies wavelet transformation on a time series of...

  5. Validation of Airborne FMCW Radar Measurements of Snow Thickness Over Sea Ice in Antarctica

    Science.gov (United States)

    Galin, Natalia; Worby, Anthony; Markus, Thorsten; Leuschen, Carl; Gogineni, Prasad

    2012-01-01

    Antarctic sea ice and its snow cover are integral components of the global climate system, yet many aspects of their vertical dimensions are poorly understood, making their representation in global climate models poor. Remote sensing is the key to monitoring the dynamic nature of sea ice and its snow cover. Reliable and accurate snow thickness data are currently a highly sought after data product. Remotely sensed snow thickness measurements can provide an indication of precipitation levels, predicted to increase with effects of climate change in the polar regions. Airborne techniques provide a means for regional-scale estimation of snow depth and distribution. Accurate regional-scale snow thickness data will also facilitate an increase in the accuracy of sea ice thickness retrieval from satellite altimeter freeboard estimates. The airborne data sets are easier to validate with in situ measurements and are better suited to validating satellite algorithms when compared with in situ techniques. This is primarily due to two factors: better chance of getting coincident in situ and airborne data sets and the tractability of comparison between an in situ data set and the airborne data set averaged over the footprint of the antennas. A 28-GHz frequency modulated continuous wave (FMCW) radar loaned by the Center for Remote Sensing of Ice Sheets to the Australian Antarctic Division is used to measure snow thickness over sea ice in East Antarctica. Provided with the radar design parameters, the expected performance parameters of the radar are summarized. The necessary conditions for unambiguous identification of the airsnow and snowice layers for the radar are presented. Roughnesses of the snow and ice surfaces are found to be dominant determinants in the effectiveness of layer identification for this radar. Finally, this paper presents the first in situ validated snow thickness estimates over sea ice in Antarctica derived from an FMCW radar on a helicopterborne platform.

  6. Effectiveness of WRF wind direction for retrieving coastal sea surface wind from synthetic aperture radar

    DEFF Research Database (Denmark)

    Takeyama, Yuko; Ohsawa, Teruo; Kozai, Katsutoshi

    2013-01-01

    Wind direction is required as input to the geophysical model function (GMF) for the retrieval of sea surface wind speed from a synthetic aperture radar (SAR) images. The present study verifies the effectiveness of using the wind direction obtained from the weather research and forecasting model (...

  7. SIMULATION OF THE Ku-BAND RADAR ALTIMETER SEA ICE EFFECTIVE SCATTERING SURFACE

    DEFF Research Database (Denmark)

    Tonboe, Rasmus; Andersen, Søren; Pedersen, Leif Toudal

    2006-01-01

    A radiative transfer model is used to simulate the sea ice radar altimeter effective scattering surface variability as a function of snow depth and density. Under dry snow conditions without layering these are the primary snow parameters affecting the scattering surface variability. The model is ...

  8. New Techniques for Radar Altimetry of Sea Ice and the Polar Oceans

    Science.gov (United States)

    Armitage, T. W. K.; Kwok, R.; Egido, A.; Smith, W. H. F.; Cullen, R.

    2017-12-01

    Satellite radar altimetry has proven to be a valuable tool for remote sensing of the polar oceans, with techniques for estimating sea ice thickness and sea surface height in the ice-covered ocean advancing to the point of becoming routine, if not operational, products. Here, we explore new techniques in radar altimetry of the polar oceans and the sea ice cover. First, we present results from fully-focused SAR (FFSAR) altimetry; by accounting for the phase evolution of scatterers in the scene, the FFSAR technique applies an inter-burst coherent integration, potentially over the entire duration that a scatterer remains in the altimeter footprint, which can narrow the effective along track resolution to just 0.5m. We discuss the improvement of using interleaved operation over burst-more operation for applying FFSAR processing to data acquired by future missions, such as a potential CryoSat follow-on. Second, we present simulated sea ice retrievals from the Ka-band Radar Interferometer (KaRIn), the instrument that will be launched on the Surface Water and Ocean Topography (SWOT) mission in 2021, that is capable of producing swath images of surface elevation. These techniques offer the opportunity to advance our understanding of the physics of the ice-covered oceans, plus new insight into how we interpret more conventional radar altimetry data in these regions.

  9. Detection of range migrating targets in compound-Gaussian clutter

    NARCIS (Netherlands)

    Petrov, N.; le Chevalier, F.; Yarovyi, O.

    2018-01-01

    This paper deals with the problem of coherent radar detection of fast moving targets in a high range resolution mode. In particular, we are focusing on the spiky clutter modeled as a compound Gaussian process with rapidly varying power along range. Additionally, a fast moving target of interest has

  10. Effects of surface roughness on sea ice freeboard retrieval with an Airborne Ku-Band SAR radar altimeter

    DEFF Research Database (Denmark)

    Hendricks, Stefan; Stenseng, Lars; Helm, Veit

    2010-01-01

    to investigate sea ice volume changes on an Arctic wide scale. Freeboard retrieval requires precise radar range measurements to the ice surface, therefore we investigate the penetration of the Ku-Band radar waves into the overlying snow cover as well as the effects of sub-footprint-scale surface roughness using...... airborne radar and laser altimeters. We find regional variable penetration of the radar signal at late spring conditions, where the difference of the radar and the reference laser range measurement never agrees with the expected snow thickness. In addition, a rough surface can lead to biases...

  11. Doppler HF Radar Application for the Study of Spatial Structure of Currents in the Black Sea

    Directory of Open Access Journals (Sweden)

    V.V. Gorbatskiy

    2017-06-01

    Full Text Available The results of the surface current spatial structure observations performed by SeaSonde Doppler HF radar (operating frequency is 25 MHz in the Black Sea region adjacent to the city of Gelendzhik are represented. The observations imply a special technique consisting in successive measurements at two selected points of the coastline. Initially, the measurements are carried out in the first of two selected coastal points during two hours. Then the radar system is transferred to the second point on the coast where the procedure is repeated. At that the velocity field is assumed to remain unchanged during the total measurement period (including the time of the radar displacement from both points. The measurement results are shown in a form of a spatial map of the current velocity vectors in the research region (with 20 × 20 km dimensions. Some features of the current spatial and temporal variability in the coastal waters are revealed. Particularly, the eddy-like formations (the diameter is a few kilometers which rapidly move and collapse. Since similar eddies are detected using the contact measurement methods, complex and variable structure of the surface currents measured by a radar does not seem to be an artifact. Nevertheless, reliability of the data resulted from the radar measurements of the surface current velocity field should be verified in future by comparing it with the results of the quasi-synchronous velocity field measurements performed by stationary, drifting and towed velocity meters.

  12. Articulatory variability in cluttering.

    Science.gov (United States)

    Hartinger, Mariam; Mooshammer, Christine

    2008-01-01

    In order to investigate the articulatory processes of the hasty and mumbled speech in cluttering, the kinematic variability was analysed by means of electromagnetic midsagittal articulography. In contrast to persons with stuttering, those with cluttering improve their intelligibility by concentrating on their speech task. Variability has always been an important criterion in comparable studies of stuttering and is discussed in terms of the stability of the speech motor system. The aim of the current study was to analyse the spatial and temporal variability in the speech of three persons with cluttering (PWC) and three control speakers. All participants were native speakers of German. The speech material consisted of repetitive CV syllables and loan words such as 'emotionalisieren', because PWC have the severest problems with long words with a complex syllable structure. The results showed a significantly higher coefficient of variation for PWC in loan word production, both in the temporal and in the spatial domain, whereas the means of displacements and durations did not differ between groups. These findings were discussed in terms of the effects of the linguistic complexity, since for the syllable repetition task, no significant differences between PWC and controls were found. Copyright 2008 S. Karger AG, Basel.

  13. Sea Ice Monitoring from Space with Synthetic Aperture Radar

    Science.gov (United States)

    Eltoft, T.; Dierking, W.; Doulgeris, A.; Kasapoglu, G.; Kraemer, T.

    2013-03-01

    This paper summarizes the knowledge status in some areas of SAR monitoring of sea ice. It starts with a brief summary of the whitepaper by Breivik et al. from OceanObs’09 [3], and then focuses on segmentation and classification, drift estimation, and assimilation strategies, which are considered as key areas in the development of more mature sea ice products from SAR and polarimetric SAR (PoLSAR) data.

  14. Surface current dynamics under sea breeze conditions observed by simultaneous HF radar, ADCP and drifter measurements

    Science.gov (United States)

    Sentchev, Alexei; Forget, Philippe; Fraunié, Philippe

    2017-04-01

    Ocean surface boundary layer dynamics off the southern coast of France in the NW Mediterranean is investigated by using velocity observations by high-frequency (HF) radars, surface drifting buoys and a downward-looking drifting acoustic Doppler current profiler (ADCP). The analysis confirms that velocities measured by HF radars correspond to those observed by an ADCP at the effective depth z f = k -1, where k is wavenumber of the radio wave emitted by the radar. The radials provided by the radars were in a very good agreement with in situ measurements, with the relative errors of 1 and 9 % and root mean square (RMS) differences of 0.02 and 0.04 m/s for monostatic and bistatic radar, respectively. The total radar-based velocities appeared to be slightly underestimated in magnitude and somewhat biased in direction. At the end of the survey period, the difference in the surface current direction, based on HF radar and ADCP data, attained 10°. It was demonstrated that the surface boundary layer dynamics cannot be reconstructed successfully without taking into the account velocity variation with depth. A significant misalignment of ˜30° caused by the sea breeze was documented between the HF radar (HFR-derived) surface current and the background current. It was also found that the ocean response to a moderate wind forcing was confined to the 4-m-thick upper layer. The respective Ekman current attained the maximum value of 0.15 m/s, and the current rotation was found to be lagging the wind by approximately 40 min, with the current vector direction being 15-20° to the left of the wind. The range of velocity variability due to wind forcing was found comparable with the magnitude of the background current variability.

  15. NOAA high resolution sea surface winds data from Synthetic Aperture Radar (SAR) on the Sentinel-1 satellites

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This data set consists of high resolution sea surface winds data produced from Synthetic Aperture Radar (SAR) on board Sentinel-1A and Sentinel-1B satellites. This...

  16. Entropy-Based Clutter Rejection for Intrawall Diagnostics

    Directory of Open Access Journals (Sweden)

    Raffaele Solimene

    2012-01-01

    Full Text Available The intrawall diagnostic problem of detecting localized inhomogeneities possibly present within the wall is addressed. As well known, clutter arising from masonry structure can impair detection of embedded scatterers due to high amplitude reflections that wall front face introduces. Moreover, internal multiple reflections also can make it difficult ground penetrating radar images (radargramms interpretation. To counteract these drawbacks, a clutter rejection method, properly tailored on the wall features, is mandatory. To this end, here we employ a windowing strategy based on entropy measures of temporal traces “similarity.” Accordingly, instants of time for which radargramms exhibit entropy values greater than a prescribed threshold are “silenced.” Numerical results are presented in order to show the effectiveness of the entropy-based clutter rejection algorithm. Moreover, a comparison with the standard average trace subtraction is also included.

  17. Hyperspectral and Radar Airborne Imagery over Controlled Release of Oil at Sea

    Directory of Open Access Journals (Sweden)

    Sébastien Angelliaume

    2017-08-01

    Full Text Available Remote sensing techniques are commonly used by Oil and Gas companies to monitor hydrocarbon on the ocean surface. The interest lies not only in exploration but also in the monitoring of the maritime environment. Occurrence of natural seeps on the sea surface is a key indicator of the presence of mature source rock in the subsurface. These natural seeps, as well as the oil slicks, are commonly detected using radar sensors but the addition of optical imagery can deliver extra information such as thickness and composition of the detected oil, which is critical for both exploration purposes and efficient cleanup operations. Today, state-of-the-art approaches combine multiple data collected by optical and radar sensors embedded on-board different airborne and spaceborne platforms, to ensure wide spatial coverage and high frequency revisit time. Multi-wavelength imaging system may create a breakthrough in remote sensing applications, but it requires adapted processing techniques that need to be developed. To explore performances offered by multi-wavelength radar and optical sensors for oil slick monitoring, remote sensing data have been collected by SETHI (Système Expérimental de Télédection Hyperfréquence Imageur, the airborne system developed by ONERA (the French Aerospace Lab, during an oil spill cleanup exercise carried out in 2015 in the North Sea, Europe. The uniqueness of this dataset lies in its high spatial resolution, low noise level and quasi-simultaneous acquisitions of different part of the EM spectrum. Specific processing techniques have been developed to extract meaningful information associated with oil-covered sea surface. Analysis of this unique and rich dataset demonstrates that remote sensing imagery, collected in both optical and microwave domains, allows estimating slick surface properties such as the age of the emulsion released at sea, the spatial abundance of oil and the relative concentration of hydrocarbons remaining on

  18. Comparison of PCA and ICA based clutter reduction in GPR systems for anti-personal landmine detection

    DEFF Research Database (Denmark)

    Karlsen, Brian; Larsen, Jan; Sørensen, Helge Bjarup Dissing

    2001-01-01

    This paper presents statistical signal processing approaches for clutter reduction in stepped-frequency ground penetrating radar (SF-GPR) data. In particular, we suggest clutter/signal separation techniques based on principal and independent component analysis (PCA/ICA). The approaches...

  19. Implementation and validation of the ISMAR High Frequency Coastal Radar Network in the Gulf of Manfredonia (Mediterranean Sea)

    DEFF Research Database (Denmark)

    Corgnati, Lorenzo; Mantovani, Carlo; Griffa, Annalisa

    2018-01-01

    In this paper a High Frequency (HF) Coastal Radar Network is described, established and maintained by the Institute of Marine Sciences (ISMAR) of the National Research Council of Italy (CNR) for the measurement of surface current velocities in the Gulf of Manfredonia, located in the semi......-enclosed Adriatic Sea (Mediterranean Sea), during the period 2013-2015. The network consisted of four HF radars that provided hourly sea surface velocity data in real-time mode in a netCDF format compliant to the Climate and Forecast Metadata Conventions CF-1.6 and to the INSPIRE directive. The hourly netCDF files...... are disseminated via a THREDDS catalog supporting OGC compliant distributions and protocols for data visualization, metadata interrogation and data download. HF radar velocity data were validated using in situ velocity measurements by GPS-tracked surface drifters deployed within the radar footprint. The results...

  20. Sensitivity of CryoSat-2 Arctic sea-ice freeboard and thickness on radar-waveform interpretation

    DEFF Research Database (Denmark)

    Ricker, R.; Hendricks, S.; Helm, V.

    2014-01-01

    In the context of quantifying Arctic ice-volume decrease at global scale, the CryoSat-2 satellite was launched in 2010 and is equipped with the K-u band synthetic aperture radar altimeter SIRAL (Synthetic Aperture Interferometric Radar Altimeter), which we use to derive sea-ice freeboard defined...... knowledge of ice and snow properties, the composition of radar backscatter and therefore the interpretation of radar echoes is crucial. This has consequences in the selection of retracker algorithms which are used to track the main scattering horizon and assign a range estimate to each CryoSat-2 measurement...... of sea-ice freeboard and higher-level products that arise from the choice of the retracker threshold only, independent of the uncertainties related to snow and ice properties. Our study shows that the choice of retracker thresholds does have a significant impact on magnitudes of estimates of sea...

  1. Modeling of GPR Clutter Caused by Soil Heterogeneity

    Directory of Open Access Journals (Sweden)

    Kazunori Takahashi

    2012-01-01

    Full Text Available In small-scale measurements, ground-penetrating radar (GPR often uses a higher frequency to detect a small object or structural changes in the ground. GPR becomes more sensitive to the natural heterogeneity of the soil when a higher frequency is used. Soil heterogeneity scatters electromagnetic waves, and the scattered waves are in part observed as unwanted reflections that are often referred to as clutter. Data containing a great amount of clutter are difficult to analyze and interpret because clutter disturbs reflections from objects of interest. Therefore, modeling GPR clutter is useful to assess the effectiveness of GPR measurements. In this paper, the development of such a technique is discussed. This modeling technique requires the permittivity distribution of soil (or its geostatistical properties and gives a nominal value of clutter power. The paper demonstrates the technique with the comparison to the data from a GPR time-lapse measurement. The proposed technique is discussed in regard to its applicability and limitations based on the results.

  2. Reconstruction of the sea surface elevation from the analysis of the data collected by a wave radar system

    Science.gov (United States)

    Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco; Lugni, Claudio; Fucile, Fabio; Bulian, Gabriele

    2016-04-01

    X-band radar system is able to provide information about direction and intensity of the sea surface currents and dominant waves in a range of few kilometers from the observation point (up to 3 nautical miles). This capability, together with their flexibility and low cost, makes these devices useful tools for the sea monitoring either coastal or off-shore area. The data collected from wave radar system can be analyzed by using the inversion strategy presented in [1,2] to obtain the estimation of the following sea parameters: peak wave direction; peak period; peak wavelength; significant wave height; sea surface current and bathymetry. The estimation of the significant wave height represents a limitation of the wave radar system because of the radar backscatter is not directly related to the sea surface elevation. In fact, in the last period, substantial research has been carried out to estimate significant wave height from radar images either with or without calibration using in-situ measurements. In this work, we will present two alternative approaches for the reconstruction of the sea surface elevation from wave radar images. In particular, the first approach is based on the basis of an approximated version of the modulation transfer function (MTF) tuned from a series of numerical simulation, following the line of[3]. The second approach is based on the inversion of radar images using a direct regularised least square technique. Assuming a linearised model for the tilt modulation, the sea elevation has been reconstructed as a least square fitting of the radar imaging data[4]. References [1]F. Serafino, C. Lugni, and F. Soldovieri, "A novel strategy for the surface current determination from marine X-band radar data," IEEE Geosci.Remote Sens. Lett., vol. 7, no. 2, pp. 231-235, Apr. 2010. [2]Ludeno, G., Brandini, C., Lugni, C., Arturi, D., Natale, A., Soldovieri, F., Serafino, F. (2014). Remocean System for the Detection of the Reflected Waves from the Costa

  3. Bistatic radar

    CERN Document Server

    Willis, Nick

    2004-01-01

    Annotation his book is a major extension of a chapter on bistatic radar written by the author for the Radar Handbook, 2nd edition, edited by Merrill Skolnik. It provides a history of bistatic systems that points out to potential designers the applications that have worked and the dead-ends not worth pursuing. The text reviews the basic concepts and definitions, and explains the mathematical development of relationships, such as geometry, Ovals of Cassini, dynamic range, isorange and isodoppler contours, target doppler, and clutter doppler spread.Key Features * All development and analysis are

  4. Performance of Distributed CFAR Processors in Pearson Distributed Clutter

    OpenAIRE

    Messali Zoubeida; Soltani Faouzi

    2007-01-01

    This paper deals with the distributed constant false alarm rate (CFAR) radar detection of targets embedded in heavy-tailed Pearson distributed clutter. In particular, we extend the results obtained for the cell averaging (CA), order statistics (OS), and censored mean level CMLD CFAR processors operating in positive alpha-stable (P&S) random variables to more general situations, specifically to the presence of interfering targets and distributed CFAR detectors. The receiver operating ...

  5. Research on Strong Clutter Suppression for Gaofen-3 Dual-Channel SAR/GMTI

    Directory of Open Access Journals (Sweden)

    Mingjie Zheng

    2018-03-01

    Full Text Available In spaceborne synthetic aperture radar (SAR, moving targets are almost buried in ground clutter due to the wide clutter Doppler spectrum and the restricted pulse repetition frequency (PRF, which increases the difficulty of moving target detection. Clutter suppression is one of the key issues in the spaceborne SAR moving target indicator operation. In this paper, we describe the clutter suppression principle and analyze the influence of amplitude and phase error on clutter suppression. In the following, a novel dual-channel SAR clutter suppression algorithm is proposed, which is suitable for the Gaofen-3(GF-3 SAR sensor. The proposed algorithm consists of three technique steps, namely adaptive two-dimensional (2D channel calibration, refined amplitude error correction and refined phase error correction. After channel error is corrected by these procedures, the clutter component, especially a strong clutter component, can be well suppressed. The validity of the proposed algorithm is verified by GF-3 SAR real data which demonstrates the ground moving-target indication (GMTI capability of GF-3 SAR sensor.

  6. Arta process model of maritime clutter and targets

    CSIR Research Space (South Africa)

    Mc

    2012-10-01

    Full Text Available stream_source_info McDonald_2013_ABSTRACT ONLY.pdf.txt stream_content_type text/plain stream_size 1370 Content-Encoding UTF-8 stream_name McDonald_2013_ABSTRACT ONLY.pdf.txt Content-Type text/plain; charset=UTF-8 IET... Radar 2012, International conference on radar systems, Glasgow, United Kingdom, 22-25 October 2012 ARTA PROCESS MODEL OF MARITIME CLUTTER AND TARGETS Andre McDonald and Jacques Cilliers Council for Scientific and Industrial Research (CSIR) Meiring...

  7. Hardware in the loop testing and evaluation of seaborne search radars

    CSIR Research Space (South Africa)

    Strydom, JJ

    2012-09-01

    Full Text Available for independent testing and evaluation of radar systems. The CSIR digital radio frequency memory (DRFM) hardware technology is used as the basis of these test systems. DRFM's are traditionally used for EW applications, but processing power of field programmable... environment simulation (RES) on digital radio frequency memory (DRFM) platforms can be utilised to test the performance of a search radar in a sea clutter Y ra n ge X r a n g e S h a p e p a r a m e t e r 0 1 2 3 4 x 1 0 4 - 3 - 2 - 1...

  8. Study of sea-surface slope distribution and its effect on radar backscatter based on Global Precipitation Measurement Ku-band precipitation radar measurements

    Science.gov (United States)

    Yan, Qiushuang; Zhang, Jie; Fan, Chenqing; Wang, Jing; Meng, Junmin

    2018-01-01

    The collocated normalized radar backscattering cross-section measurements from the Global Precipitation Measurement (GPM) Ku-band precipitation radar (KuPR) and the winds from the moored buoys are used to study the effect of different sea-surface slope probability density functions (PDFs), including the Gaussian PDF, the Gram-Charlier PDF, and the Liu PDF, on the geometrical optics (GO) model predictions of the radar backscatter at low incidence angles (0 deg to 18 deg) at different sea states. First, the peakedness coefficient in the Liu distribution is determined using the collocations at the normal incidence angle, and the results indicate that the peakedness coefficient is a nonlinear function of the wind speed. Then, the performance of the modified Liu distribution, i.e., Liu distribution using the obtained peakedness coefficient estimate; the Gaussian distribution; and the Gram-Charlier distribution is analyzed. The results show that the GO model predictions with the modified Liu distribution agree best with the KuPR measurements, followed by the predictions with the Gaussian distribution, while the predictions with the Gram-Charlier distribution have larger differences as the total or the slick filtered, not the radar filtered, probability density is included in the distribution. The best-performing distribution changes with incidence angle and changes with wind speed.

  9. Mapping coastal sea level at high resolution with radar interferometry: the SWOT Mission

    Science.gov (United States)

    Fu, L. L.; Chao, Y.; Laignel, B.; Turki, I., Sr.

    2017-12-01

    The spatial resolution of the present constellation of radar altimeters in mapping two-dimensional sea surface height (SSH) variability is approaching 100 km (in wavelength). At scales shorter than 100 km, the eddies and fronts are responsible for the stirring and mixing of the ocean, especially important in the various coastal processes. A mission currently in development will make high-resolution measurement of the height of water over the ocean as well as on land. It is called Surface Water and Ocean Topography (SWOT), which is a joint mission of US NASA and French CNES, with contributions from Canada and UK. SWOT will carry a pair of interferometry radars and make 2-dimensional SSH measurements over a swath of 120 km with a nadir gap of 20 km in a 21-day repeat orbit. The synthetic aperture radar of SWOT will make SSH measurement at extremely high resolution of 10-70 m. SWOT will also carry a nadir looking conventional altimeter and make 1-dimensional SSH measurements along the nadir gap. The temporal sampling varies from 2 repeats per 21 days at the equator to more than 4 repeats at mid latitudes and more than 6 at high latitudes. This new mission will allow a continuum of fine-scale observations from the open ocean to the coasts, estuaries and rivers, allowing us to investigate a number of scientific and technical questions in the coastal and estuarine domain to assess the coastal impacts of regional sea level change, such as the interaction of sea level with river flow, estuary inundation, storm surge, coastal wetlands, salt water intrusion, etc. As examples, we will illustrate the potential impact of SWOT to the studies of the San Francisco Bay Delta, and the Seine River estuary, etc. Preliminary results suggest that the SWOT Mission will provide fundamental data to map the spatial variability of water surface elevations under different hydrodynamic conditions and at different scales (local, regional and global) to improve our knowledge of the complex

  10. Comparison of space borne radar altimetry and airborne laser altimetry over sea ice in the Fram Strait

    DEFF Research Database (Denmark)

    Giles, K.A.; Hvidegaard, Sine Munk

    2006-01-01

    This paper describes the first comparison of satellite radar and airborne laser altimetry over sea ice. In order to investigate the differences between measurements from the two different instruments we explore the statistical properties of the data and determine reasonable scales in space and time...... at which to examine them. The resulting differences between the data sets show that the laser and the radar are reflecting from different surfaces and that the magnitude of the difference decreases with increasing surface air temperature. This suggests that the penetration depth of the radar signal......, into the snow, varies with temperature. The results also show the potential for computing Arctic wide snow depth maps by combining measurements from laser and radar altimeters....

  11. About uncertainties in sea ice thickness retrieval from satellite radar altimetry: results from the ESA-CCI Sea Ice ECV Project Round Robin Exercise

    Science.gov (United States)

    Kern, S.; Khvorostovsky, K.; Skourup, H.; Rinne, E.; Parsakhoo, Z. S.; Djepa, V.; Wadhams, P.; Sandven, S.

    2014-03-01

    One goal of the European Space Agency Climate Change Initiative sea ice Essential Climate Variable project is to provide a quality controlled 20 year long data set of Arctic Ocean winter-time sea ice thickness distribution. An important step to achieve this goal is to assess the accuracy of sea ice thickness retrieval based on satellite radar altimetry. For this purpose a data base is created comprising sea ice freeboard derived from satellite radar altimetry between 1993 and 2012 and collocated observations of snow and sea ice freeboard from Operation Ice Bridge (OIB) and CryoSat Validation Experiment (CryoVEx) air-borne campaigns, of sea ice draft from moored and submarine Upward Looking Sonar (ULS), and of snow depth from OIB campaigns, Advanced Microwave Scanning Radiometer aboard EOS (AMSR-E) and the Warren Climatology (Warren et al., 1999). An inter-comparison of the snow depth data sets stresses the limited usefulness of Warren climatology snow depth for freeboard-to-thickness conversion under current Arctic Ocean conditions reported in other studies. This is confirmed by a comparison of snow freeboard measured during OIB and CryoVEx and snow freeboard computed from radar altimetry. For first-year ice the agreement between OIB and AMSR-E snow depth within 0.02 m suggests AMSR-E snow depth as an appropriate alternative. Different freeboard-to-thickness and freeboard-to-draft conversion approaches are realized. The mean observed ULS sea ice draft agrees with the mean sea ice draft computed from radar altimetry within the uncertainty bounds of the data sets involved. However, none of the realized approaches is able to reproduce the seasonal cycle in sea ice draft observed by moored ULS satisfactorily. A sensitivity analysis of the freeboard-to-thickness conversion suggests: in order to obtain sea ice thickness as accurate as 0.5 m from radar altimetry, besides a freeboard estimate with centimetre accuracy, an ice-type dependent sea ice density is as mandatory

  12. SEA ICE THICKNESS MEASUREMENT BY GROUND PENETRATING RADAR FOR GROUND TRUTH OF MICROWAVE REMOTE SENSING DATA

    Directory of Open Access Journals (Sweden)

    M. Matsumoto

    2018-04-01

    Full Text Available Observation of sea ice thickness is one of key issues to understand regional effect of global warming. One of approaches to monitor sea ice in large area is microwave remote sensing data analysis. However, ground truth must be necessary to discuss the effectivity of this kind of approach. The conventional method to acquire ground truth of ice thickness is drilling ice layer and directly measuring the thickness by a ruler. However, this method is destructive, time-consuming and limited spatial resolution. Although there are several methods to acquire ice thickness in non-destructive way, ground penetrating radar (GPR can be effective solution because it can discriminate snow-ice and ice-sea water interface. In this paper, we carried out GPR measurement in Lake Saroma for relatively large area (200 m by 300 m, approximately aiming to obtain grand truth for remote sensing data. GPR survey was conducted at 5 locations in the area. The direct measurement was also conducted simultaneously in order to calibrate GPR data for thickness estimation and to validate the result. Although GPR Bscan image obtained from 600MHz contains the reflection which may come from a structure under snow, the origin of the reflection is not obvious. Therefore, further analysis and interpretation of the GPR image, such as numerical simulation, additional signal processing and use of 200 MHz antenna, are required to move on thickness estimation.

  13. ARCHAEOLOGICAL SURVEYS ON THE GERMAN NORTH SEA COAST USING HIGH-RESOLUTION SYNTHETIC APERTURE RADAR DATA

    Directory of Open Access Journals (Sweden)

    M. Gade

    2017-11-01

    Full Text Available We show that high-resolution space-borne Synthetic Aperture Radar (SAR imagery with pixel sizes well below 1 m2 can be used to complement archaeological surveys in areas that are difficult to access. After major storm surges in the 14th and 17th centuries, vast areas on the German North Sea coast were lost to the sea. Areas of former settlements and historical land use were buried under sediments for centuries, but when the surface layer is driven away under the permanent action of wind, currents, and waves, they appear again on the Wadden Sea surface. However, the frequent flooding and erosion of the intertidal flats make any archaeological monitoring a difficult task, so that remote sensing techniques appear to be an efficient and cost-effective instrument for any archaeological surveillance of that area. Space-borne SAR images clearly show remnants of farmhouse foundations and of former systems of ditches, dating back to the 14th and to the 16th/17th centuries. In particular, the very high-resolution acquisition (staring spotlight mode of the German TerraSAR/ TanDEM-X satellites allows for the detection of various kinds of residuals of historical land use with high precision. In addition, we also investigate the capability of SARs working at lower microwave frequencies (on Radarsat-2 to complement our archaeological survey of historical cultural traces, some of which have been unknown so far.

  14. Sea Ice Thickness Measurement by Ground Penetrating Radar for Ground Truth of Microwave Remote Sensing Data

    Science.gov (United States)

    Matsumoto, M.; Yoshimura, M.; Naoki, K.; Cho, K.; Wakabayashi, H.

    2018-04-01

    Observation of sea ice thickness is one of key issues to understand regional effect of global warming. One of approaches to monitor sea ice in large area is microwave remote sensing data analysis. However, ground truth must be necessary to discuss the effectivity of this kind of approach. The conventional method to acquire ground truth of ice thickness is drilling ice layer and directly measuring the thickness by a ruler. However, this method is destructive, time-consuming and limited spatial resolution. Although there are several methods to acquire ice thickness in non-destructive way, ground penetrating radar (GPR) can be effective solution because it can discriminate snow-ice and ice-sea water interface. In this paper, we carried out GPR measurement in Lake Saroma for relatively large area (200 m by 300 m, approximately) aiming to obtain grand truth for remote sensing data. GPR survey was conducted at 5 locations in the area. The direct measurement was also conducted simultaneously in order to calibrate GPR data for thickness estimation and to validate the result. Although GPR Bscan image obtained from 600MHz contains the reflection which may come from a structure under snow, the origin of the reflection is not obvious. Therefore, further analysis and interpretation of the GPR image, such as numerical simulation, additional signal processing and use of 200 MHz antenna, are required to move on thickness estimation.

  15. Analysis of a Pareto Mixture Distribution for Maritime Surveillance Radar

    Directory of Open Access Journals (Sweden)

    Graham V. Weinberg

    2012-01-01

    Full Text Available The Pareto distribution has been shown to be an excellent model for X-band high-resolution maritime surveillance radar clutter returns. Given the success of mixture distributions in radar, it is thus of interest to consider the effect of Pareto mixture models. This paper introduces a formulation of a Pareto intensity mixture distribution and investigates coherent multilook radar detector performance using this new clutter model. Clutter parameter estimates are derived from data sets produced by the Defence Science and Technology Organisation's Ingara maritime surveillance radar.

  16. Towards flash flood prediction in the dry Dead Sea region utilizing radar rainfall information

    Science.gov (United States)

    Morin, E.; Jacoby, Y.; Navon, S.; Bet-Halachmi, E.

    2009-04-01

    Flash-flood warning models can save lives and protect various kinds of infrastructure. In dry climate regions, rainfall is highly variable and can be of high-intensity. Since rain gauge networks in such areas are sparse, rainfall information derived from weather radar systems can provide useful input for flash-flood models. This paper presents a flash-flood warning model utilizing radar rainfall data and applies it to two catchments that drain into the dry Dead Sea region. Radar-based quantitative precipitation estimates (QPEs) were derived using a rain gauge adjustment approach, either on a daily basis (allowing the adjustment factor to change over time, assuming available real-time gauge data) or using a constant factor value (derived from rain gauge data) over the entire period of the analysis. The QPEs served as input for a continuous hydrological model that represents the main hydrological processes in the region, namely infiltration, flow routing and transmission losses. The infiltration function is applied in a distributed mode while the routing and transmission loss functions are applied in a lumped mode. Model parameters were found by calibration based on five years of data for one of the catchments. Validation was performed for a subsequent five-year period for the same catchment and then for an entire ten year record for the second catchment. The probability of detection and false alarm rates for the validation cases were reasonable. Probabilistic flash-flood prediction is presented applying Monte Carlo simulations with an uncertainty range for the QPEs and model parameters. With low probability thresholds, one can maintain more than 70% detection with no more than 30% false alarms. The study demonstrates that a flash-flood-warning model is feasible for catchments in the area studied.

  17. Towards flash-flood prediction in the dry Dead Sea region utilizing radar rainfall information

    Science.gov (United States)

    Morin, Efrat; Jacoby, Yael; Navon, Shilo; Bet-Halachmi, Erez

    2009-07-01

    Flash-flood warning models can save lives and protect various kinds of infrastructure. In dry climate regions, rainfall is highly variable and can be of high-intensity. Since rain gauge networks in such areas are sparse, rainfall information derived from weather radar systems can provide useful input for flash-flood models. This paper presents a flash-flood warning model which utilizes radar rainfall data and applies it to two catchments that drain into the dry Dead Sea region. Radar-based quantitative precipitation estimates (QPEs) were derived using a rain gauge adjustment approach, either on a daily basis (allowing the adjustment factor to change over time, assuming available real-time gauge data) or using a constant factor value (derived from rain gauge data) over the entire period of the analysis. The QPEs served as input for a continuous hydrological model that represents the main hydrological processes in the region, namely infiltration, flow routing and transmission losses. The infiltration function is applied in a distributed mode while the routing and transmission loss functions are applied in a lumped mode. Model parameters were found by calibration based on the 5 years of data for one of the catchments. Validation was performed for a subsequent 5-year period for the same catchment and then for an entire 10-year record for the second catchment. The probability of detection and false alarm rates for the validation cases were reasonable. Probabilistic flash-flood prediction is presented applying Monte Carlo simulations with an uncertainty range for the QPEs and model parameters. With low probability thresholds, one can maintain more than 70% detection with no more than 30% false alarms. The study demonstrates that a flash-flood warning model is feasible for catchments in the area studied.

  18. Remote sensing of surface currents in the Fraser River plume with the SeaSonde HF radar

    International Nuclear Information System (INIS)

    Hodgins, D.O.; Hardy, J.S.; Tinis, S.E.

    1994-09-01

    The SeaSonde 12.5-MHz radar system was deployed to measure surface currents in the Juan de Fuca Strait in July 1992. Reliable data were obtained from the two radars installed, and successful trials were conducted with the Infosat satellite link to transmit data from the remote site. Data recovery from the SeaSonde was generally good, with maximum ranges varying from 15 km to over 30 km. Sea echo return strength at both radars was correlated with wind, consistent with lower Bragg scattering at lower wind speeds. A simple surface current forecasting algorithm, based on decomposing the signal into tidal and residual bands, was examined. It was found that tides account for the greatest portion of currents in the study area, and could be forecasted out to 48 h with 1-2 d of input data. The nonpredictable, fluctuating part of the current signal was isolated and its statistics were calculated. The algorithm tests showed that the SeaSonde data can be used to measure and predict the slowly varying tidal and mean flow velocities, as well as the random part of the signal, both of which are important in oil spill modelling. Surface flow patterns and time-series data from the SeaSonde measurements, and from a three-dimensional hydrodynamic model, were compared from an oil spill modelling perspective. In general, surface flow patterns from the model were smoother than those observed. The differences were most noticeable in the cross-channel direction. The radar data indicate that a flow-dependent eddy viscosity formulation, with coefficients calibrated to reproduce the features observed with the radar, would improve agreement and yield a good model for data assimilation. 21 refs., 478 figs., 3 tabs

  19. Clutter Moves in Old Age Homecare

    DEFF Research Database (Denmark)

    Lutz, Peter

    2010-01-01

    This chapter introduces the notion of clutter moves as an experimental heuristic for tracing how movement threads together a range of cluttered entities in old age homecare ecologies. In particular it is concerned with older people and their cluttered technologies. It is based on empirical data o...

  20. Identification of sea ice types in spaceborne synthetic aperture radar data

    Science.gov (United States)

    Kwok, Ronald; Rignot, Eric; Holt, Benjamin; Onstott, R.

    1992-01-01

    This study presents an approach for identification of sea ice types in spaceborne SAR image data. The unsupervised classification approach involves cluster analysis for segmentation of the image data followed by cluster labeling based on previously defined look-up tables containing the expected backscatter signatures of different ice types measured by a land-based scatterometer. Extensive scatterometer observations and experience accumulated in field campaigns during the last 10 yr were used to construct these look-up tables. The classification approach, its expected performance, the dependence of this performance on radar system performance, and expected ice scattering characteristics are discussed. Results using both aircraft and simulated ERS-1 SAR data are presented and compared to limited field ice property measurements and coincident passive microwave imagery. The importance of an integrated postlaunch program for the validation and improvement of this approach is discussed.

  1. Surface current measurements in Juan de Fuca Strait using the SeaSonde HF [high frequency] radar

    International Nuclear Information System (INIS)

    Hodgins, D.O.

    1994-09-01

    The shore-based SeaSonde high-frequency (HF) radar was deployed for three weeks in summer 1993 to measure surface currents in the Strait of Georgia, British Columbia. Experimental objectives included documenting the complex flow regime generated by large tides and the brackish plume of the Fraser River, and determining the radar performance under low-wind, low-salinity conditions. The radar data showed that surface flows are dominated by the plume jet formed by the Fraser River outflow, giving rise to recurring, energetic eddies with scales of 8-12 km, strong flow meanders, and convergent fronts. These features were continuously modulated by the along-channel tidal flows. Comparisons with a detailed numerical model hindcast gave good correlation between observed and predicted flow fields, especially at tidal and low frequencies. Radar return was found to be correlated with local winds and radar performance was independent of salinity variations in the plume. Synthetic aperture radar (SAR) provides a map of the radar scattering characteristics of the ocean surface on a capillary wave scale. ERS-1 satellite and airborne SAR images for July 28, 1993 were obtained and surface features were examined in the context of the HF radar current fields. Results show that SAR images alone cannot reliably provide the dynamical data required in this region by oil spill models. Under certain conditions, however, the radar imagery offers valuable physical information on phenomena affecting oil slick development. Interpretation of SAR imagery in conjunction with other remote sensing information would offer more quantitative prediction data. 28 refs., 334 figs., 1 tab

  2. Performance of Distributed CFAR Processors in Pearson Distributed Clutter

    Directory of Open Access Journals (Sweden)

    Messali Zoubeida

    2007-01-01

    Full Text Available This paper deals with the distributed constant false alarm rate (CFAR radar detection of targets embedded in heavy-tailed Pearson distributed clutter. In particular, we extend the results obtained for the cell averaging (CA, order statistics (OS, and censored mean level CMLD CFAR processors operating in positive alpha-stable (P&S random variables to more general situations, specifically to the presence of interfering targets and distributed CFAR detectors. The receiver operating characteristics of the greatest of (GO and the smallest of (SO CFAR processors are also determined. The performance characteristics of distributed systems are presented and compared in both homogeneous and in presence of interfering targets. We demonstrate, via simulation results, that the distributed systems when the clutter is modelled as positive alpha-stable distribution offer robustness properties against multiple target situations especially when using the "OR" fusion rule.

  3. Performance of Distributed CFAR Processors in Pearson Distributed Clutter

    Directory of Open Access Journals (Sweden)

    Faouzi Soltani

    2007-01-01

    Full Text Available This paper deals with the distributed constant false alarm rate (CFAR radar detection of targets embedded in heavy-tailed Pearson distributed clutter. In particular, we extend the results obtained for the cell averaging (CA, order statistics (OS, and censored mean level CMLD CFAR processors operating in positive alpha-stable (P&S random variables to more general situations, specifically to the presence of interfering targets and distributed CFAR detectors. The receiver operating characteristics of the greatest of (GO and the smallest of (SO CFAR processors are also determined. The performance characteristics of distributed systems are presented and compared in both homogeneous and in presence of interfering targets. We demonstrate, via simulation results, that the distributed systems when the clutter is modelled as positive alpha-stable distribution offer robustness properties against multiple target situations especially when using the “OR” fusion rule.

  4. An Investigation of the Pareto Distribution as a Model for High Grazing Angle Clutter

    Science.gov (United States)

    2011-03-01

    radar detection schemes under controlled conditions. Complicated clutter models result in mathematical difficulties in the determination of optimal and...a population [7]. It has been used in the modelling of actuarial data; an example is in excess of loss quotations in insurance [8]. Its usefulness as...UNCLASSIFIED modified Bessel functions, making it difficult to employ in radar detection schemes. The Pareto Distribution is amenable to mathematical

  5. Developing hydrological monitoring system based on HF radar for islands and reefs in the South China Sea

    Science.gov (United States)

    Li, J.; Shi, P.; Chen, J.; Zhu, Y.; Li, B.

    2016-12-01

    There are many islands (or reefs) in the South China Sea. The hydrological properties (currents and waves) around the islands are highly spatially variable compared to those of coastal region of mainland, because the shorelines are more complex with much smaller scale, and the topographies are step-shape with a much sharper slope. The currents and waves with high spatial variations may destroy the buildings or engineering on shorelines, or even influence the structural stability of reefs. Therefore, it is necessary to establish monitoring systems to obtain the high-resolution hydrological information. This study propose a plan for developing a hydrological monitoring system based on HF radar on the shoreline of a typical island in the southern South China Sea: firstly, the HF radar are integrated with auxiliary equipment (such as dynamo, fuel tank, air conditioner, communication facilities) in a container to build a whole monitoring platform; synchronously, several buoys are set within the radar visibility for data calibration and validation; and finally, the current and wave observations collected by the HF radar are assimilated with numerical models to obtain long-term and high-precision reanalysis products. To test the feasibility of this plan, our research group has built two HF radar sites at the western coastal region of Guangdong Province. The collected data were used to extract surface current information and assimilated with an ocean model. The results show that the data assimilation can highly improve the surface current simulation, especially for typhoon periods. Continuous data with intervals between 6 and 12 hour are the most suitable for ideal assimilations. On the other hand, the test also reveal that developing similar monitoring system on island environments need advanced radars that have higher resolutions and a better performance for persistent work.

  6. Monsoon Convective During the South China Sea Monsoon Experiment: Observations from Ground-Based Radar and the TRMM Satellite

    Science.gov (United States)

    Cifelli, Rob; Rickenbach, Tom; Halverson, Jeff; Keenan, Tom; Kucera, Paul; Atkinson, Lester; Fisher, Brad; Gerlach, John; Harris, Kathy; Kaufman, Cristina

    1999-01-01

    A main goal of the recent South China Sea Monsoon Experiment (SCSMEX) was to study convective processes associated with the onset of the Southeast Asian summer monsoon. The NASA TOGA C-band scanning radar was deployed on the Chinese research vessel Shi Yan #3 for two 20 day cruises, collecting dual-Doppler measurements in conjunction with the BMRC C-Pol dual-polarimetric radar on Dongsha Island. Soundings and surface meteorological data were also collected with an NCAR Integrated Sounding System (ISS). This experiment was the first major tropical field campaign following the launch of the Tropical Rainfall Measuring Mission (TRMM) satellite. These observations of tropical oceanic convection provided an opportunity to make comparisons between surface radar measurements and the Precipitation Radar (PR) aboard the TRMM satellite in an oceanic environment. Nearly continuous radar operations were conducted during two Intensive Observing Periods (IOPS) straddling the onset of the monsoon (5-25 May 1998 and 5-25 June 1998). Mesoscale lines of convection with widespread regions of both trailing and forward stratiform precipitation were observed following the onset of the active monsoon in the northern South China Sea region. The vertical structure of the convection during periods of strong westerly flow and relatively moist environmental conditions in the lower to mid-troposphere contrasted sharply with convection observed during periods of low level easterlies, weak shear, and relatively dry conditions in the mid to upper troposphere. Several examples of mesoscale convection will be shown from the ground (ship)-based and spaceborne radar data during times of TRMM satellite overpasses. Examples of pre-monsoon convection, characterized by isolated cumulonimbus and shallow, precipitating congestus clouds, will also be discussed.

  7. Monsoon Convection during the South China Sea Monsoon Experiment Observed from Shipboard Radar and the TRMM Satellite

    Science.gov (United States)

    Rickenbach, Tom; Cifelli, Rob; Halverson, Jeff; Kucera, Paul; Atkinson, Lester; Fisher, Brad; Gerlach, John; Harris, Kathy; Kaufman, Cristina; Liu, Ching-Hwang; hide

    1999-01-01

    A main goal of the recent South China Sea Monsoon Experiment (SCSMEX) was to study convective processes associated with the onset of the Southeast Asian summer monsoon. The NASA TOGA C-band scanning radar was deployed on the Chinese research vessel Shi Yan #3 for two 20 day cruises, collecting dual-Doppler measurements in conjunction with the BMRC C-Pol dual-polarimetric radar on Dongsha Island. Soundings and surface meteorological data were also collected with an NCAR Integrated Sounding System (ISS). This experiment was the first major tropical field campaign following the launch of the Tropical Rainfall Measuring Mission (TRMM) satellite. These observations of tropical oceanic convection provided an opportunity to make comparisons between surface radar measurements and the Precipitation Radar (PR) aboard the TRMM satellite in an oceanic environment. Nearly continuous radar operations were conducted during two Intensive Observing Periods (IOPS) straddling the onset of the monsoon (5-25 May 1998 and 5-25 June 1998). Mesoscale lines of convection with widespread regions of both trailing and forward stratiform precipitation were observed during the active monsoon periods in a southwesterly flow regime. Several examples of mesoscale convection will be shown from ship-based and spacebome radar reflectivity data during times of TRMM satellite overpasses. Further examples of pre-monsoon convection, characterized by isolated cumulonimbus and shallow, precipitating congestus clouds, will be discussed. A strong waterspout was observed very near the ship from an isolated cell in the pre-monsoon period, and was well documented with photography, radar, sounding, and sounding data.

  8. Holocene relative sea level variations at the spit system Feddet (Denmark) resolved by ground-penetrating radar and geomorphological data

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Bendixen, Mette; Clemmensen, Lars B

    Estimates of Holocene sea-level variations have been presented in a range of studies based on different approaches, including interpretation of internal beach ridge characteristics from ground-penetrating radar (GPR) and geomorphological data. We present GPR data and geomorphological observations...... of independent GPR and geomorphologic data collected across the recent and sub-recent beach ridge deposits. The data analyses include coastal topography, internal dips of beach ridge layers, and sea-level measurements. A clear change in characteristic layer dip is observed between beach face and upper shoreface...

  9. The SUMO Ship Detector Algorithm for Satellite Radar Images

    Directory of Open Access Journals (Sweden)

    Harm Greidanus

    2017-03-01

    Full Text Available Search for Unidentified Maritime Objects (SUMO is an algorithm for ship detection in satellite Synthetic Aperture Radar (SAR images. It has been developed over the course of more than 15 years, using a large amount of SAR images from almost all available SAR satellites operating in L-, C- and X-band. As validated by benchmark tests, it performs very well on a wide range of SAR image modes (from Spotlight to ScanSAR and resolutions (from 1–100 m and for all types and sizes of ships, within the physical limits imposed by the radar imaging. This paper describes, in detail, the algorithmic approach in all of the steps of the ship detection: land masking, clutter estimation, detection thresholding, target clustering, ship attribute estimation and false alarm suppression. SUMO is a pixel-based CFAR (Constant False Alarm Rate detector for multi-look radar images. It assumes a K distribution for the sea clutter, corrected however for deviations of the actual sea clutter from this distribution, implementing a fast and robust method for the clutter background estimation. The clustering of detected pixels into targets (ships uses several thresholds to deal with the typically irregular distribution of the radar backscatter over a ship. In a multi-polarization image, the different channels are fused. Azimuth ambiguities, a common source of false alarms in ship detection, are removed. A reliability indicator is computed for each target. In post-processing, using the results of a series of images, additional false alarms from recurrent (fixed targets including range ambiguities are also removed. SUMO can run in semi-automatic mode, where an operator can verify each detected target. It can also run in fully automatic mode, where batches of over 10,000 images have successfully been processed in less than two hours. The number of satellite SAR systems keeps increasing, as does their application to maritime surveillance. The open data policy of the EU

  10. Wind Turbine Radar Cross Section

    Directory of Open Access Journals (Sweden)

    David Jenn

    2012-01-01

    Full Text Available The radar cross section (RCS of a wind turbine is a figure of merit for assessing its effect on the performance of electronic systems. In this paper, the fundamental equations for estimating the wind turbine clutter signal in radar and communication systems are presented. Methods of RCS prediction are summarized, citing their advantages and disadvantages. Bistatic and monostatic RCS patterns for two wind turbine configurations, a horizontal axis three-blade design and a vertical axis helical design, are shown. The unique electromagnetic scattering features, the effect of materials, and methods of mitigating wind turbine clutter are also discussed.

  11. 2006 Fynmeet sea clutter measurement trial: Datasets

    CSIR Research Space (South Africa)

    Herselman, PLR

    2007-09-06

    Full Text Available -011............................................................................................................................................................................................. 25 iii Dataset CAD14-001 0 5 10 15 20 25 30 35 10 20 30 40 50 60 70 80 90 R an ge G at e # Time [s] A bs ol ut e R an ge [m ] RCS [dBm2] vs. time and range for f1 = 9.000 GHz - CAD14-001 2400 2600 2800... 40 10 20 30 40 50 60 70 80 90 R an ge G at e # Time [s] A bs ol ut e R an ge [m ] RCS [dBm2] vs. time and range for f1 = 9.000 GHz - CAD14-002 2400 2600 2800 3000 3200 3400 3600 -30 -25 -20 -15 -10 -5 0 5 10...

  12. The impact of the snow cover on sea-ice thickness products retrieved by Ku-band radar altimeters

    Science.gov (United States)

    Ricker, R.; Hendricks, S.; Helm, V.; Perovich, D. K.

    2015-12-01

    Snow on sea ice is a relevant polar climate parameter related to ocean-atmospheric interactions and surface albedo. It also remains an important factor for sea-ice thickness products retrieved from Ku-band satellite radar altimeters like Envisat or CryoSat-2, which is currently on its mission and the subject of many recent studies. Such satellites sense the height of the sea-ice surface above the sea level, which is called sea-ice freeboard. By assuming hydrostatic equilibrium and that the main scattering horizon is given by the snow-ice interface, the freeboard can be transformed into sea-ice thickness. Therefore, information about the snow load on hemispherical scale is crucial. Due to the lack of sufficient satellite products, only climatological values are used in current studies. Since such values do not represent the high variability of snow distribution in the Arctic, they can be a substantial contributor to the total sea-ice thickness uncertainty budget. Secondly, recent studies suggest that the snow layer cannot be considered as homogenous, but possibly rather featuring a complex stratigraphy due to wind compaction and/or ice lenses. Therefore, the Ku-band radar signal can be scattered at internal layers, causing a shift of the main scattering horizon towards the snow surface. This alters the freeboard and thickness retrieval as the assumption that the main scattering horizon is given by the snow-ice interface is no longer valid and introduces a bias. Here, we present estimates for the impact of snow depth uncertainties and snow properties on CryoSat-2 sea-ice thickness retrievals. We therefore compare CryoSat-2 freeboard measurements with field data from ice mass-balance buoys and aircraft campaigns from the CryoSat Validation Experiment. This unique validation dataset includes airborne laser scanner and radar altimeter measurements in spring coincident to CryoSat-2 overflights, and allows us to evaluate how the main scattering horizon is altered by the

  13. A Clinical Delineation of Tachyphemia (Cluttering)

    African Journals Online (AJOL)

    orders of speech, language and communication in general. The majority of .... of cluttering', and left a cluttering-like residue when cured. ... General rate of speech. Vegetative manifestations. Emotions. Respiration. Singing ... (a) In some families men in different generations show ... women as well as men being affected.

  14. FMCW radar system for detection and classification of small vessels in high sea state conditions

    NARCIS (Netherlands)

    Wasselin, J.-P.; Mazuel, S.; Itcia, E.; Huizing, A.G.; Theil, A.

    2012-01-01

    The ROCKWELL COLLINS France radar department is currently developing a FMCW radar system for the detection and the classification of small maritime targets in the frame of the SISMARIS, SARGOS & I2C projects. Several test campaigns have been conducted since 2009 to develop a sensor as well as an

  15. Comparison of sea-level measurements using microwave radar and subsurface pressure gauge deployed in Mandovi estuary in Goa, Central West Coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mehra, P.; Agarvadekar, Y.; Luis, R.; Nadaf, L.

    . INTRODUCTION The information about mean sea level and its variability along the coastal locations is essential for practical as well as scientific studies. However, witness to the recent disastrous consequences of Japan Tsunami (11 th March, 2011... technologies are (IOC, 2006); A stilling well and a float, Pressure system, Acoustic system and Radar system. We will briefly describe the principle of operation of Pressure and Radar system in this section, as they are the used in the present study: A...

  16. Integrating ground-penetrating radar and borehole data from a Wadden Sea barrier island

    DEFF Research Database (Denmark)

    Nielsen, Lars; Møller, I.; Nielsen, L. H.

    2009-01-01

    Sea level rise may have large implications for low-gradient barrier coastal systems. This problem motivated an integrated ground-penetrating radar (GPR) and sedimentological study of the Rømø Wadden Sea barrier island. Crossing W-E and N-S-oriented 100 MHz GPR reflection profiles with a total...... island. We document different standard processing steps which lead to increased signal-to-noise ratio, improved resolution and trustworthy GPR-to-borehole correlation. The GPR signals image the subsurface layering with a vertical resolution of ~ 0.2-0.3 m. The penetration depth of the GPR reflection...... conversion of the reflection profiles. The GPR reflections are correlated with sedimentological facies logs, and we test to which extent it is possible to map the architecture of different sedimentary units of the Rømø barrier island based on joint interpretation of the GPR and core data. Detailed...

  17. Radar Signature Calculation Facility

    Data.gov (United States)

    Federal Laboratory Consortium — FUNCTION: The calculation, analysis, and visualization of the spatially extended radar signatures of complex objects such as ships in a sea multipath environment and...

  18. An Ultra-Wideband, Microwave Radar for Measuring Snow Thickness on Sea Ice and Mapping Near-Surface Internal Layers in Polar Firn

    Science.gov (United States)

    Panzer, Ben; Gomez-Garcia, Daniel; Leuschen, Carl; Paden, John; Rodriguez-Morales, Fernando; Patel, Azsa; Markus, Thorsten; Holt, Benjamin; Gogineni, Prasad

    2013-01-01

    Sea ice is generally covered with snow, which can vary in thickness from a few centimeters to >1 m. Snow cover acts as a thermal insulator modulating the heat exchange between the ocean and the atmosphere, and it impacts sea-ice growth rates and overall thickness, a key indicator of climate change in polar regions. Snow depth is required to estimate sea-ice thickness using freeboard measurements made with satellite altimeters. The snow cover also acts as a mechanical load that depresses ice freeboard (snow and ice above sea level). Freeboard depression can result in flooding of the snow/ice interface and the formation of a thick slush layer, particularly in the Antarctic sea-ice cover. The Center for Remote Sensing of Ice Sheets (CReSIS) has developed an ultra-wideband, microwave radar capable of operation on long-endurance aircraft to characterize the thickness of snow over sea ice. The low-power, 100mW signal is swept from 2 to 8GHz allowing the air/snow and snow/ ice interfaces to be mapped with 5 c range resolution in snow; this is an improvement over the original system that worked from 2 to 6.5 GHz. From 2009 to 2012, CReSIS successfully operated the radar on the NASA P-3B and DC-8 aircraft to collect data on snow-covered sea ice in the Arctic and Antarctic for NASA Operation IceBridge. The radar was found capable of snow depth retrievals ranging from 10cm to >1 m. We also demonstrated that this radar can be used to map near-surface internal layers in polar firn with fine range resolution. Here we describe the instrument design, characteristics and performance of the radar.

  19. The Aesthetics of Junkyards and Roadside Clutter

    Directory of Open Access Journals (Sweden)

    Thomas Leddy

    2008-01-01

    Full Text Available A little more than thirty years ago, Allen Carlson argued that although the concept of "Camp" would seem to allow for the aesthetic redemption of roadside clutter and junkyards, it does not.[1] He opposes those who claim that if one takes the right attitude to roadside clutter it can be seen as aesthetic. In this essay I argue that that there is nothing wrong with this, although I will not base my argument on the idea of Camp sensibility.

  20. Radar rainfall image repair techniques

    Directory of Open Access Journals (Sweden)

    Stephen M. Wesson

    2004-01-01

    Full Text Available There are various quality problems associated with radar rainfall data viewed in images that include ground clutter, beam blocking and anomalous propagation, to name a few. To obtain the best rainfall estimate possible, techniques for removing ground clutter (non-meteorological echoes that influence radar data quality on 2-D radar rainfall image data sets are presented here. These techniques concentrate on repairing the images in both a computationally fast and accurate manner, and are nearest neighbour techniques of two sub-types: Individual Target and Border Tracing. The contaminated data is estimated through Kriging, considered the optimal technique for the spatial interpolation of Gaussian data, where the 'screening effect' that occurs with the Kriging weighting distribution around target points is exploited to ensure computational efficiency. Matrix rank reduction techniques in combination with Singular Value Decomposition (SVD are also suggested for finding an efficient solution to the Kriging Equations which can cope with near singular systems. Rainfall estimation at ground level from radar rainfall volume scan data is of interest and importance in earth bound applications such as hydrology and agriculture. As an extension of the above, Ordinary Kriging is applied to three-dimensional radar rainfall data to estimate rainfall rate at ground level. Keywords: ground clutter, data infilling, Ordinary Kriging, nearest neighbours, Singular Value Decomposition, border tracing, computation time, ground level rainfall estimation

  1. Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval

    Directory of Open Access Journals (Sweden)

    K. Guerreiro

    2017-09-01

    Full Text Available Over the past decade, sea-ice freeboard has been monitored with various satellite altimetric missions with the aim of producing long-term time series of ice thickness. While recent studies have demonstrated the capacity of the CryoSat-2 mission (2010–present to provide accurate freeboard measurements, the current estimates obtained with the Envisat mission (2002–2012 still require some large improvements. In this study, we first estimate Envisat and CryoSat-2 radar freeboard by using the exact same processing algorithms. We then analyse the freeboard difference between the two estimates over the common winter periods (November 2010–April 2011 and November 2011–March 2012. The analysis of along-track data and gridded radar freeboard in conjunction with Envisat pulse-peakiness (PP maps suggests that the discrepancy between the two sensors is related to the surface properties of sea-ice floes and to the use of a threshold retracker. Based on the relation between the Envisat pulse peakiness and the radar freeboard difference between Envisat and CryoSat-2, we produce a monthly CryoSat-2-like version of Envisat freeboard. The improved Envisat data set freeboard displays a similar spatial distribution to CryoSat-2 (RMSD  =  1.5 cm during the two ice growth seasons and for all months of the period of study. The comparison of the altimetric data sets with in situ ice draught measurements during the common flight period shows that the improved Envisat data set (RMSE  =  12–28 cm is as accurate as CryoSat-2 (RMSE  =  15–21 cm and much more accurate than the uncorrected Envisat data set (RMSE  =  178–179 cm. The comparison of the improved Envisat radar freeboard data set is then extended to the rest of the Envisat mission to demonstrate the validity of PP correction from the calibration period. The good agreement between the improved Envisat data set and the in situ ice draught data set (RMSE

  2. Comparison of CryoSat-2 and ENVISAT radar freeboard over Arctic sea ice: toward an improved Envisat freeboard retrieval

    Science.gov (United States)

    Guerreiro, Kevin; Fleury, Sara; Zakharova, Elena; Kouraev, Alexei; Rémy, Frédérique; Maisongrande, Philippe

    2017-09-01

    Over the past decade, sea-ice freeboard has been monitored with various satellite altimetric missions with the aim of producing long-term time series of ice thickness. While recent studies have demonstrated the capacity of the CryoSat-2 mission (2010-present) to provide accurate freeboard measurements, the current estimates obtained with the Envisat mission (2002-2012) still require some large improvements. In this study, we first estimate Envisat and CryoSat-2 radar freeboard by using the exact same processing algorithms. We then analyse the freeboard difference between the two estimates over the common winter periods (November 2010-April 2011 and November 2011-March 2012). The analysis of along-track data and gridded radar freeboard in conjunction with Envisat pulse-peakiness (PP) maps suggests that the discrepancy between the two sensors is related to the surface properties of sea-ice floes and to the use of a threshold retracker. Based on the relation between the Envisat pulse peakiness and the radar freeboard difference between Envisat and CryoSat-2, we produce a monthly CryoSat-2-like version of Envisat freeboard. The improved Envisat data set freeboard displays a similar spatial distribution to CryoSat-2 (RMSD = 1.5 cm) during the two ice growth seasons and for all months of the period of study. The comparison of the altimetric data sets with in situ ice draught measurements during the common flight period shows that the improved Envisat data set (RMSE = 12-28 cm) is as accurate as CryoSat-2 (RMSE = 15-21 cm) and much more accurate than the uncorrected Envisat data set (RMSE = 178-179 cm). The comparison of the improved Envisat radar freeboard data set is then extended to the rest of the Envisat mission to demonstrate the validity of PP correction from the calibration period. The good agreement between the improved Envisat data set and the in situ ice draught data set (RMSE = 13-32 cm) demonstrates the potential of the PP correction to produce accurate

  3. Surface Circulation in the Iroise Sea (W. Brittany) from High Resolution HF Radar Mapping

    Science.gov (United States)

    2013-01-01

    oceanographic conditions in many coastal regions (e.g. Bassin et al., 2005; Breivik and Sætra, 2001; Haus et al., 2000; Kaplan et al., 2005; Kovacevic et...Oceanol. Acta 22–2, 153–166. Breivik , O., Sætra, O., 2001. Real time assimilation of HF radar currents into a coastal ocean model. J. Mar. Syst. 28

  4. A 100,000 Scale Factor Radar Range.

    Science.gov (United States)

    Blanche, Pierre-Alexandre; Neifeld, Mark; Peyghambarian, Nasser

    2017-12-19

    The radar cross section of an object is an important electromagnetic property that is often measured in anechoic chambers. However, for very large and complex structures such as ships or sea and land clutters, this common approach is not practical. The use of computer simulations is also not viable since it would take many years of computational time to model and predict the radar characteristics of such large objects. We have now devised a new scaling technique to overcome these difficulties, and make accurate measurements of the radar cross section of large items. In this article we demonstrate that by reducing the scale of the model by a factor 100,000, and using near infrared wavelength, the radar cross section can be determined in a tabletop setup. The accuracy of the method is compared to simulations, and an example of measurement is provided on a 1 mm highly detailed model of a ship. The advantages of this scaling approach is its versatility, and the possibility to perform fast, convenient, and inexpensive measurements.

  5. An Improved Semi-Empirical Model for Radar Backscattering from Rough Sea Surfaces at X-Band

    Directory of Open Access Journals (Sweden)

    Taekyeong Jin

    2018-04-01

    Full Text Available We propose an improved semi-empirical scattering model for X-band radar backscattering from rough sea surfaces. This new model has a wider validity range of wind speeds than does the existing semi-empirical sea spectrum (SESS model. First, we retrieved the small-roughness parameters from the sea surfaces, which were numerically generated using the Pierson-Moskowitz spectrum and measurement datasets for various wind speeds. Then, we computed the backscattering coefficients of the small-roughness surfaces for various wind speeds using the integral equation method model. Finally, the large-roughness characteristics were taken into account by integrating the small-roughness backscattering coefficients multiplying them with the surface slope probability density function for all possible surface slopes. The new model includes a wind speed range below 3.46 m/s, which was not covered by the existing SESS model. The accuracy of the new model was verified with two measurement datasets for various wind speeds from 0.5 m/s to 14 m/s.

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

    Science.gov (United States)

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

    2017-12-01

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

  7. Sea Ice Deformation State From Synthetic Aperture Radar Imagery - Part II: Effects of Spatial Resolution and Noise Level

    DEFF Research Database (Denmark)

    Dierking, Wolfgang; Dall, Jørgen

    2008-01-01

    C- and L-band airborne synthetic aperture radar (SAR) imagery acquired at like- and cross-polarization over sea ice under winter conditions is examined with the objective to study the discrimination between level ice and ice deformation features. High-resolution low-noise data were analysed...... in the first paper. In this second paper, the main topics are the effects of spatial resolution and signal-to-noise ratio. Airborne, high-resolution SAR scenes are used to generate a sequence of images with increasingly coarser spatial resolution from 5 m to 25 m, keeping the number of looks constant....... The signal-to-noise ratio is varied between typical noise levels for airborne imagery and satellite data. Areal fraction of deformed ice and average deformation distance are determined for each image product. At L-band, the retrieved values of the areal fraction get larger as the image resolution is degraded...

  8. Experimental measurement and theoretical modeling of microwave scattering and the structure of the sea surface influencing radar observations from space

    Science.gov (United States)

    Arnold, David; Kong, J. A.

    1992-01-01

    The electromagnetic (EM) bias 'epsilon' is an error present in radar altimetry of the ocean due to the nonuniform reflection from wave troughs and crests. The EM bias is defined as the difference between the mean reflecting surface and the mean sea surface. A knowledge of the EM bias is necessary to permit error reduction in mean sea level measurements by satellite radar altimeters. Direct measurements of the EM bias were made from a Shell Offshore oil production platform in the Gulf of Mexico for a six month period during 1989 and 1990. Measurements of the EM bias were made at 5 and 14 Ghz. During the EM bias experiments by Melville et al., a wire wave gauge was used to obtain the modulation of the high frequency waves by the low frequency waves. It became apparent that the EM bias was primarily caused by the modulation of the short waves. This was reported by Arnold et al. The EM bias is explained using physical optics scattering and an empirical model for the short wave modulation. Measurements of the short wave modulation using a wire wave gauge demonstrated a linear dependence of the normalized bias on the short wave modulation strength, M. The theory accurately predicts this dependence by the relation epsilon = -alphaMH sub 1/3. The wind speed dependence of the normalized bias is explained by the dependence of the short wave modulation strength on the wind speed. While other effects such as long wave tilt and curvature will have an effect on the bias, the primary cause of the bias is shown to be due to the short wave modulation. This report will present a theory using physical optics scattering and an empirical model of the short wave modulation to estimate the EM bias. The estimated EM bias will be compared to measurements at C and Ku bands.

  9. Volcanic and Tectonic Activity in the Red Sea Region (2004-2013): Insights from Satellite Radar Interferometry and Optical Imagery

    KAUST Repository

    Xu, Wenbin

    2015-04-01

    Studying recent volcanic and tectonic events in the Red Sea region is important for improving our knowledge of the Red Sea plate boundary and for regional geohazard assessments. However, limited information has been available about the past activity due to insufficient in-situ data and remoteness of some of the activity. In this dissertation, I have used satellite remote sensing to derive new information about several recent volcanic and tectonic events in the Red Sea region. I first report on three volcanic eruptions in the southern Red Sea, the 2007-8 Jebel at Tair eruption and the 2011-12 & 2013 Zubair eruptions, which resulted in formation of two new islands. Series of high- resolution optical images were used to map the extent of lava flows and to observe and analyze the growth and destructive processes of the new islands. I used Interferometric Synthetic Aperture Radar (InSAR) data to study the evolution of lava flows, to estimate their volumes, as well as to generate ground displacements maps, which were used to model the dikes that fed the eruptions. I then report on my work of the 2009 Harrat Lunayyir dike intrusion and the 2004 Tabuk earthquake sequence in western Saudi Arabia. I used InSAR observations and stress calculations to study the intruding dike at Harrat Lunayyir, while I combined InSAR data and Bayesian estimation to study the Tabuk earthquake activity. The key findings of the thesis are: 1) The recent volcanic eruptions in the southern Red Sea indicate that the area is magmatically more active than previously acknowledged and that a rifting episode has been taken place in the southern Red Sea; 2) Stress interactions between an ascending dike intrusion and normal faulting on graben-bounding faults above the dike can inhibit vertical propagation of magma towards the surface; 3) InSAR observations can improve locations of shallow earthquakes and fault model uncertainties are useful to associate earthquake activity with mapped faults; 4). The

  10. Ground-Penetrating Radar Study of Fort Morgan Peninsula Holocene Beach Ridges as Sea-level Indicators

    Science.gov (United States)

    Philbin, A.; Frederick, B.; Blum, M. D.; Tsoflias, G. P.

    2017-12-01

    Holocene sea-level change along the northern Gulf of Mexico (GoM) coast is controversial. One view interprets basal peats from the Mississippi Delta to indicate continual sea-level (SL) rise for the GoM as a whole. An alternate view proposes that data from the subsiding delta is primarily a subsidence signal, and that sandy non-deltaic shorelines indicate that regional SL reached present elevations by the middle Holocene, with minor oscillations since then. In fact, new regional long-term subsidence records from biostratigraphic indicators display significant subsidence in deltaic areas where basal-peat data were collected, and negligible rates along the GoM shoreline to the east. However, the use of sandy progradational shorelines, commonly known as "beach ridge systems", has been criticized for a lack of precise sea-level indicators, and therefore discounted. This research focuses on developing Holocene progradational sandy shorelines along the Alabama coast in the eastern GoM as SL indicators. Sandy shorelines in this area are ideal to examine SL change because they are well preserved, sufficiently distant from the subsiding delta, well mapped, and ages are known from previous work. Two-dimensional ground-penetrating radar imaging of well-dated beach-ridge successions is used here to examine and identify changes through time in the elevation of the shoreface clinoform topset-foreset break, which represents the transition between flat-lying foreshore and seaward-dipping shoreface facies, and forms in the intertidal zone. Beach-ridge successions with optical luminescence ages of ca. 5500-4800 yrs BP display topset-foreset breaks at current mean sea-level elevation, whereas beach-ridge successions from ca. 3500-2400 yrs BP display topset-foreset breaks that are 1 m above present mean SL and the elevation of modern topset-foreset breaks. These data support the view that current sea-level was reached by the middle Holocene, and was higher than present for at least

  11. Characterization of icebergs and floating sea ice in the Yung Sund fjord in Greenland from satellite radar and optical images.

    Science.gov (United States)

    Guillaso, Stephane; Gay, Michel; Gervaise, Cedric

    2017-04-01

    At the Zackenberg site, sea ice starts to move between June and September resulting in icebergs flowing freely on the sea. Splitting into smaller parts, they reduce in size. Icebergs represent a risk for maritime transport and needs to be studied. In order to determine iceberg density per surface unit, size distribution, and movement of icebergs, we need to observe, detect, range and track them. The use of SAR images is particularly well adapted in regions where cloud cover is very present. We focused our study on the Yung Sund fjord in Greenland, where lots of icebergs and sea ice are generated during the summer. In the beginning of July, sea ice breaks up first, followed by icebergs created by the different glaciers based in the ocean. During our investigation, we noticed that the iceberg and sea ice were drifting very fast and thus, we needed to adapt our methodology. To achieve our goal, we collected all remote sensing data available in the region, principally Sentinel 1/2 and LandSAT 8 during one ice free season (from July 1st 2016 to September 30th, 2016). We developed an original approach in order to detect, characterize and track icebergs and sea ice independently from data. The iceberg detection was made using a watershed technique. The advantage of this technique is that it can be applied to both optical and radar images. For the latter, calibrated intensity is transformed into an image using a scaling function, in order to make ice brighter. Land data is masked using a topographic map. When data is segmented, a statistical test derived from the CFAR approach is performed to isolate an iceberg and floating sea ice from the ocean. Finally, a method, such SIFT or BRISK is used to identify and track the different segmented object. These approaches give a representation of the object and make the tracking easier and independent of the scale and rotation, which can occur because icebergs are dependent on ocean currents and wind. Finally, to fill in the gap

  12. Comparisons of some scattering theories with recent scatterometer measurements. [sea roughness radar model

    Science.gov (United States)

    Fung, A. K.; Dome, G.; Moore, R. K.

    1977-01-01

    The paper compares the predictions of two different types of sea scatter theories with recent scatterometer measurements which indicate the variations of the backscattering coefficient with polarization, incident angle, wind speed, and azimuth angle. Wright's theory (1968) differs from that of Chan and Fung (1977) in two major aspects: (1) Wright uses Phillips' sea spectrum (1966) while Chan and Fung use that of Mitsuyasu and Honda, and (2) Wright uses a modified slick sea slope distribution by Cox and Munk (1954) while Chan and Fung use the slick sea slope distribution of Cox and Munk defined with respect to the plane perpendicular to the look direction. Satisfactory agreements between theory and experimental data are obtained when Chan and Fung's model is used to explain the wind and azimuthal dependence of the scattering coefficient.

  13. Seasonal variability of the Red Sea, from satellite gravity, radar altimetry, and in situ observations

    Science.gov (United States)

    Wahr, John; Smeed, David A.; Leuliette, Eric; Swenson, Sean

    2014-08-01

    Seasonal variations of sea surface height (SSH) and mass within the Red Sea are caused mostly by exchange of heat with the atmosphere and by flow through the strait opening into the Gulf of Aden to the south. That flow involves a net mass transfer into the Red Sea during fall and out during spring, though in summer there is an influx of cool water at intermediate depths. Thus, summer water in the south is warmer near the surface due to higher air temperatures, but cooler at intermediate depths. Summer water in the north experiences warming by air-sea exchange only. The temperature affects water density, which impacts SSH but has no effect on mass. We study this seasonal cycle by combining GRACE mass estimates, altimeter SSH measurements, and steric contributions derived from the World Ocean Atlas temperature climatology. Among our conclusions are: mass contributions are much larger than steric contributions; the mass is largest in winter, consistent with winds pushing water into the Red Sea in fall and out during spring; the steric signal is largest in summer, consistent with surface warming; and the cool, intermediate-depth water flowing into the Red Sea in spring has little impact on the steric signal, because contributions from the lowered temperature are offset by effects of decreased salinity. The results suggest that the combined use of altimeter and GRACE measurements can provide a useful alternative to in situ data for monitoring the steric signal.

  14. A comparison of visual observations of surface oil with Synthetic Aperture Radar imagery of the Sea Empress oil spill

    Energy Technology Data Exchange (ETDEWEB)

    Jones, B.

    2001-06-15

    A comparison has been made between the visual observations of surface oil and four satellite-borne Synthetic Aperture Radar (SAR) images taken during the Sea Empress oil spill in February 1996. Whilst the basic oil slick imaging capabilities of SAR are well documented, to be of use at the time of a major oil spill, the imagery must be able to provide information on the thickness of oil. This analysis suggests that, under certain environmental conditions, this is possible. The optimum wind speed for the identification of heavy surface oil is around 5-6 m s{sup -1}. At this wind speed, light and medium sheen is not evident in the imagery and there is a distinction between the backscatter reductions due to heavy sheen and thick brown/black oil. At higher wind speeds, even thick oil slicks readily mix into the water column and their SAR signature weakens. In light winds, pattern recognition is very important to the identification of oil sticks. The images are more sensitive to the presence of sheen within the sheltered waters of Milford Haven than in the open coastal waters, indicating a possible relationship between sheen visibility in satellite-borne SAR and sea state. (author)

  15. Automatic identification of bird targets with radar via patterns produced by wing flapping

    NARCIS (Netherlands)

    Zaugg, S.; Saporta, G.; van Loon, E.; Schmaljohann, H.; Liechti, F.

    2008-01-01

    Bird identification with radar is important for bird migration research, environmental impact assessments (e.g. wind farms), aircraft security and radar meteorology. In a study on bird migration, radar signals from birds, insects and ground clutter were recorded. Signals from birds show a typical

  16. Persymmetric Adaptive Detectors of Subspace Signals in Homogeneous and Partially Homogeneous Clutter

    Directory of Open Access Journals (Sweden)

    Ding Hao

    2015-08-01

    Full Text Available In the field of adaptive radar detection, an effective strategy to improve the detection performance is to exploit the structural information of the covariance matrix, especially in the case of insufficient reference cells. Thus, in this study, the problem of detecting multidimensional subspace signals is discussed by considering the persymmetric structure of the clutter covariance matrix, which implies that the covariance matrix is persymmetric about its cross diagonal. Persymmetric adaptive detectors are derived on the basis of the one-step principle as well as the two-step Generalized Likelihood Ratio Test (GLRT in homogeneous and partially homogeneous clutter. The proposed detectors consider the structural information of the covariance matrix at the design stage. Simulation results suggest performance improvement compared with existing detectors when reference cells are insufficient. Moreover, the detection performance is assessed with respect to the effects of the covariance matrix, signal subspace dimension, and mismatched performance of signal subspace as well as signal fluctuations.

  17. The use of radar for bathymetry assessment

    OpenAIRE

    Aardoom, J.H.; Greidanus, H.S.F.

    1998-01-01

    The bottom topography in shallow seas can be observed by air- and spaceborne imaging radar. Bathymetric information derived from radar data is limited in accuracy, but radar has a good spatial coverage. The accuracy can be increased by assimilating the radar imagery into existing or insitu gathered bathymetric data. The paper reviews the concepts of bathymetry assessment by radar, the radar imaging mechanism, and the possibilities and limitations of the use of radar data in rapid assessment.

  18. Clasificación del clutter marino utilizando redes neuronales artificiales

    Directory of Open Access Journals (Sweden)

    Argel Gonzalez Padilla

    2013-04-01

    Full Text Available La detección de radar bajo la acción del clutter marino es un problema actual. La efectividad de esta detección puede ser mejorada o aún optimizada si el comportamiento estadístico de los parámetros de las señales dispersadas por la superficie del mar (clutter marino es conocida. En el presente trabajo, la mayoría de los modelos estadísticos del clutter marino bajo diferentes condiciones es dada y se logra en un solo documento de manera sintética agrupar un gran volumen de información, difícil de encontrar, y en muchos casos, de interpretar. La mayor contribución investigativa de este trabajo es la presentación de los fundamentos de un sistema auto adaptativo  para la detección de blancos de radar, basado en el reconocimiento de diferentes distribuciones que modelan las mediciones de amplituddelclutter marino, obtenida en un intervalo de tiempo dado. Realizando una clasificación más fina al especificar el rango de valores que toman los parámetros de la distribución, para el intervalo de tiempo que se analiza. Este sistema fue simulado satisfactoriamente utilizando redes neuronales.Los resultados revelaron que se puede realizar de forma efectiva el reconocimiento de distribuciones de mediciones de amplitud del clutter marino y de los parámetros de la distribución.

  19. NOAA high resolution sea surface winds data from Synthetic Aperture Radar (SAR) on the RADARSAT-2 satellite

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Synthetic Aperture Radar (SAR)-derived high resolution wind products are calculated from high resolution SAR images of normalized radar cross section (NRCS) of the...

  20. The relationship between the microwave radar cross section and both wind speed and stress: Model function studies using Frontal Air-Sea Interaction Experiment data

    Science.gov (United States)

    Weissman, David E.; Davidson, Kenneth L.; Brown, Robert A.; Friehe, Carl A.; Li, Fuk

    1994-01-01

    The Frontal Air-Sea Interaction Experiment (FASINEX) provided a unique data set with coincident airborne scatterometer measurements of the ocean surface radar cross section (RCS)(at Ku band) and near-surface wind and wind stress. These data have been analyzed to study new model functions which relate wind speed and surface friction velocity (square root of the kinematic wind stress) to the radar cross section and to better understand the processes in the boundary layer that have a strong influence on the radar backscatter. Studies of data from FASINEX indicate that the RCS has a different relation to the friction velocity than to the wind speed. The difference between the RCS models using these two variables depends on the polarization and the incidence angle. The radar data have been acquired from the Jet Propulsion Laboratory airborne scatterometer. These data span 10 different flight days. Stress measurements were inferred from shipboard instruments and from aircraft flying at low altitudes, closely following the scatterometer. Wide ranges of radar incidence angles and environmental conditions needed to fully develop algorithms are available from this experiment.

  1. A Combined EOF/Variational Approach for Mapping Radar-Derived Sea Surface Currents

    Science.gov (United States)

    2011-01-01

    gaps in the gridded SST images, which was successfully applied in Adriatic ( Alvera - Azcarate et al., 2005). Kondrashov and Chil (2006) developed...velocities. Similar to SST analysis (Beckers and Rixen, 2003: Alvera -Azcarate et al.. 2005), these modes are used to fill the gaps in HFR...and selection of the time interval for estimating the covariances becomes important. In the present study the sea surface velocity Alvera -Azcarate

  2. Past sea-level data from Lakse Bugt, Disko Island, West Greenland from ground-penetrating radar data

    Science.gov (United States)

    Souza, Priscila E.; Nielsen, Lars; Kroon, Aart; Clemmensen, Lars B.

    2016-04-01

    Beach-ridge deposits have been used as sea-level indicators in numerous studies from temperate coastal regions. However, their present surface morphology in artic regions may not accurately correspond to past sea-level, because subsequent surface erosion, solifluction processes and/or later sediment deposition may have altered the surface significantly. The internal structure of these beach ridges, however, is often well-preserved and thus constitutes an important key to reconstruction of past sea levels as seen elsewhere. In the present study, high-resolution reflection GPR data and high-precision topographic data were collected at Lakse Bugt (Disko Island, West Greenland) using a shielded 250 MHz antennae system and a RTK-Trimble R8 DGPS, respectively. Three transects were collected across a sequence of fossil, raised beach ridge deposits, and two transects were obtained across modern beach deposits at the shoreline of the mesotidal regime. Along all radar profiles we observed downlap reflection points, which we interpret to represent the boundary between sediments deposited on the beachface and sediments deposited in the upper shoreface regime. Both the upper shoreface and the beachface deposits exhibit reflection patterns dipping in the seaward direction. The beachface deposits show the strongest dip. At or just below the downlap points strong diffractions are often observed indicating the presence of a layer containing stones. These stones are large enough to generate significant signal scattering. At the present day beach a sharp transition defined by the presence of large stones is observed near the low tide water level: cobbles characterize the seaside, while the land side is characterized by sand and gravel. Therefore, it seems reasonable to conclude that downlap points observed in the GPR data serve as indicators of past low-tide levels (at the time of deposition). The downlap points show a consistent offset with respect to present surface topography

  3. The 2007-8 volcanic eruption on Jebel at Tair island (Red Sea) observed by satellite radar and optical images

    KAUST Repository

    Xu, Wenbin; Jonsson, Sigurjon

    2014-01-01

    We use high-resolution optical images and Interferometric Synthetic Aperture Radar (InSAR) data to study the September 2007-January 2008 Jebel at Tair eruption. Comparison of pre- and post-eruption optical images reveals several fresh ground fissures, a new scoria cone near the summit, and that 5.9 ± 0.1 km2 of new lava covered about half of the island. Decorrelation in the InSAR images indicates that lava flowed both to the western and to the northeastern part of the island after the start of the eruption, while later lavas were mainly deposited near the summit and onto the north flank of the volcano. From the InSAR data, we also estimate that the average thickness of the lava flows is 3.8 m, resulting in a bulk volume of around 2.2 × 107 m3. We observe no volcano-wide pre- or post-eruption uplift, which suggests that the magma source may be deep. The co-eruption interferograms, on the other hand, reveal local and rather complex deformation. We use these observations to constrain a tensile dislocation model that represents the dike intrusion that fed the eruption. The model results show that the orientation of the dike is perpendicular to the Red Sea rift, implying that the local stresses within the volcanic edifice are decoupled from the regional stress field. © 2014 Springer-Verlag Berlin Heidelberg.

  4. The 2007-8 volcanic eruption on Jebel at Tair island (Red Sea) observed by satellite radar and optical images

    KAUST Repository

    Xu, Wenbin

    2014-01-31

    We use high-resolution optical images and Interferometric Synthetic Aperture Radar (InSAR) data to study the September 2007-January 2008 Jebel at Tair eruption. Comparison of pre- and post-eruption optical images reveals several fresh ground fissures, a new scoria cone near the summit, and that 5.9 ± 0.1 km2 of new lava covered about half of the island. Decorrelation in the InSAR images indicates that lava flowed both to the western and to the northeastern part of the island after the start of the eruption, while later lavas were mainly deposited near the summit and onto the north flank of the volcano. From the InSAR data, we also estimate that the average thickness of the lava flows is 3.8 m, resulting in a bulk volume of around 2.2 × 107 m3. We observe no volcano-wide pre- or post-eruption uplift, which suggests that the magma source may be deep. The co-eruption interferograms, on the other hand, reveal local and rather complex deformation. We use these observations to constrain a tensile dislocation model that represents the dike intrusion that fed the eruption. The model results show that the orientation of the dike is perpendicular to the Red Sea rift, implying that the local stresses within the volcanic edifice are decoupled from the regional stress field. © 2014 Springer-Verlag Berlin Heidelberg.

  5. Variability in the air–sea interaction patterns and timescales within the south-eastern Bay of Biscay, as observed by HF radar data

    Directory of Open Access Journals (Sweden)

    A. Fontán

    2013-04-01

    Full Text Available Two high-frequency (HF radar stations were installed on the coast of the south-eastern Bay of Biscay in 2009, providing high spatial and temporal resolution and large spatial coverage of currents in the area for the first time. This has made it possible to quantitatively assess the air–sea interaction patterns and timescales for the period 2009–2010. The analysis was conducted using the Barnett–Preisendorfer approach to canonical correlation analysis (CCA of reanalysis surface winds and HF radar-derived surface currents. The CCA yields two canonical patterns: the first wind–current interaction pattern corresponds to the classical Ekman drift at the sea surface, whilst the second describes an anticyclonic/cyclonic surface circulation. The results obtained demonstrate that local winds play an important role in driving the upper water circulation. The wind–current interaction timescales are mainly related to diurnal breezes and synoptic variability. In particular, the breezes force diurnal currents in waters of the continental shelf and slope of the south-eastern Bay. It is concluded that the breezes may force diurnal currents over considerably wider areas than that covered by the HF radar, considering that the northern and southern continental shelves of the Bay exhibit stronger diurnal than annual wind amplitudes.

  6. Quantifying clutter: A comparison of four methods and their relationship to bat detection

    Science.gov (United States)

    Joy M. O’Keefe; Susan C. Loeb; Hoke S. Hill Jr.; J. Drew Lanham

    2014-01-01

    The degree of spatial complexity in the environment, or clutter, affects the quality of foraging habitats for bats and their detection with acoustic systems. Clutter has been assessed in a variety of ways but there are no standardized methods for measuring clutter. We compared four methods (Visual Clutter, Cluster, Single Variable, and Clutter Index) and related these...

  7. Application of phase coherent transform to cloud clutter suppression

    Energy Technology Data Exchange (ETDEWEB)

    Ng, L.C. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    This paper describes a tracking algorithm using frame-to-frame correlation with frequency domain clutter suppression. Clutter suppression was mechanized via a `Phase Coherent Transform` (PCT) approach. This approach was applied to explore the feasibility of tracking a post-boost rocket from a low earth orbit satellite with real cloud background data. Simulation results show that the PCT/correlation tracking algorithm can perform satisfactorily at signal-to-clutter ratio (SCR) as low as 5 or 7 dB.

  8. New clutter-rejection algorithm for Doppler ultrasound

    Science.gov (United States)

    Cloutier, Guy; Chen, Danmin; Durand, Louis-Gilles

    2002-04-01

    Several strategies, known as clutter or wall Doppler filtering, were proposed to remove the strong echoes produced by stationary or slow moving tissue structures from the Doppler blood flow signal. In this study, the matching pursuit (MP) method is proposed to remove clutter components. The MP method decomposes the Doppler signal into wavelet atoms that are selected in a decreasing energy order. Thus, the high-energy clutter components are extracted first. In the present study, the pulsatile Doppler signal s(n) was simulated by a sum of random-phase sinusoids. Two types of high-amplitude clutter signals were then superimposed on s(n): a time-varying low frequency component (type 1), covering systole and early diastole, and short transient clutter signals (type 2), distributed within the whole cardiac cycle. The Doppler signals were modeled with the MP method and the most dominant atoms were subtracted until the signal-to-clutter (S/C) ratio reached a maximum. For the type 1 clutter signal, the improvement in the S/C ratio was 19.0 +/- 0.6 dB, and 72.0 +/- 4.5 atoms were required to reach this performance. For the transient type 2 clutter signal, exactly 10 atoms were required and the maximum improvement in S/C ratio was 5.5 +/- 0.5 dB. These results suggest the possibility of using this signal processing approach to implement clutter rejection filters on ultrasound commercial instruments.

  9. Implementation and validation of the ISMAR High Frequency Coastal Radar Network in the Gulf of Manfredonia (Mediterranean Sea)

    DEFF Research Database (Denmark)

    Corgnati, Lorenzo; Mantovani, Carlo; Griffa, Annalisa

    2017-01-01

    are disseminated via a THREDDS catalog supporting OGC compliant distributions and protocols for data visualization, metadata interrogation and data download. HF radar velocity data were validated using in situ velocity measurements by GPS-tracked surface drifters deployed within the radar footprint. The results...... show a good agreement, with the root mean square (rms) of the difference between radial velocities from HF radar and drifters ranging between 20% - 50% of the drifter velocity rms. The HF radar data have also been compared with subsurface velocity profiles from an upward looking Acoustic Doppler...... are considered. Results show that, at least in the considered period, the velocity in the water column is well correlated, and there is a good agreement between surface HF radar and ADCP data (correlations between 0.95 - 0.75). The Gulf of Manfredonia network has been instrumental to the set up of a core...

  10. Effects of Video Exposure to Cluttering on Undergraduate Students' Perceptions of a Person Who Clutters

    Science.gov (United States)

    Farrell, Lindsey M.; Blanchet, Paul G.; Tillery, Kim L.

    2015-01-01

    Background: Previous research suggests a negative stereotype toward people with fluency disorders (i.e. stuttering and/or cluttering), although recent findings suggest that exposure to an actual person who stutters (e.g. a live or video presentation) leads to more positive perceptions of some personality traits. However, there is a paucity of…

  11. The use of radar for bathymetry assessment

    NARCIS (Netherlands)

    Aardoom, J.H.; Greidanus, H.S.F.

    1998-01-01

    The bottom topography in shallow seas can be observed by air- and spaceborne imaging radar. Bathymetric information derived from radar data is limited in accuracy, but radar has a good spatial coverage. The accuracy can be increased by assimilating the radar imagery into existing or insitu gathered

  12. Insights into factors contributing to the observability of a submarine at periscope depth by modern radar, Part 2: EM simulation of mast RCS in a realistic sea surface environment

    CSIR Research Space (South Africa)

    Smit, JC

    2012-09-01

    Full Text Available IEEE-APS Topical Conference on Antennas and Propagation in Wireless Communications (APWC), Cape Town 2-7 September 2012 Insights into factors contributing to the observability of a submarine at periscope depth by modern radar, Part 2: EM... simulation of mast RCS in a realistic sea surface environment Smit JC; Cilliers JE CSIR, Defence, Peace, Safety and Security. PO Box 395, Pretoria, 0001 Abstract Recently, a set of high resolution radar measurements were undertaken in South...

  13. Comparison of retracked coastal altimetry sea levels against high frequency radar on the continental shelf of the Great Barrier Reef, Australia

    Science.gov (United States)

    Idris, Nurul Hazrina; Deng, Xiaoli; Idris, Nurul Hawani

    2017-07-01

    Comparison of Jason-1 altimetry retracked sea levels and high frequency (HF) radar velocity is examined within the region of the Great Barrier Reef, Australia. The comparison between both datasets is not direct because the altimetry derives only the geostrophic component, while the HF radar velocity includes information on both geostrophic and ageostrophic components, such as tides and winds. The comparison of altimetry and HF radar data is performed based on the parameter of surface velocity inferred from both datasets. The results show that 48% (10 out of 21 cases) of data have high (≥0.5) spatial correlation. The mean of spatial correlation for all 21 cases is 0.43. This value is within the range (0.42 to 0.5) observed by other studies. Low correlation is observed due to disagreement in the trend of velocity signals in which sometimes they have contradictions in the signal direction and the position of the peak is shifted. In terms of standard deviation of difference and root mean square error, both datasets show reasonable agreement with ≤2.5 cm s-1.

  14. Phased-array design for MST and ST radars

    Science.gov (United States)

    Ecklund, W. L.

    1986-01-01

    All of the existing radar systems fully dedicated to clear-air radar studies use some type of phased-array antennas. The effects of beam-steering techniques including feed networks and phase shifters; sidelobe control; ground-clutter suppression; low altitude coverage; arrays with integrated radiating elements and feed networks; analysis of coaxial-collinear antennas; use of arrays with multiple beams; and array testing and measure on structural design of the antenna are discussed.

  15. A practical algorithm for the retrieval of floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar imagery

    Directory of Open Access Journals (Sweden)

    Byongjun Hwang

    2017-07-01

    Full Text Available In this study, we present an algorithm for summer sea ice conditions that semi-automatically produces the floe size distribution of Arctic sea ice from high-resolution satellite Synthetic Aperture Radar data. Currently, floe size distribution data from satellite images are very rare in the literature, mainly due to the lack of a reliable algorithm to produce such data. Here, we developed the algorithm by combining various image analysis methods, including Kernel Graph Cuts, distance transformation and watershed transformation, and a rule-based boundary revalidation. The developed algorithm has been validated against the ground truth that was extracted manually with the aid of 1-m resolution visible satellite data. Comprehensive validation analysis has shown both perspectives and limitations. The algorithm tends to fail to detect small floes (mostly less than 100 m in mean caliper diameter compared to ground truth, which is mainly due to limitations in water-ice segmentation. Some variability in the power law exponent of floe size distribution is observed due to the effects of control parameters in the process of de-noising, Kernel Graph Cuts segmentation, thresholds for boundary revalidation and image resolution. Nonetheless, the algorithm, for floes larger than 100 m, has shown a reasonable agreement with ground truth under various selections of these control parameters. Considering that the coverage and spatial resolution of satellite Synthetic Aperture Radar data have increased significantly in recent years, the developed algorithm opens a new possibility to produce large volumes of floe size distribution data, which is essential for improving our understanding and prediction of the Arctic sea ice cover

  16. Theoretical Study of Topside Ionospheric Clutter

    Science.gov (United States)

    1992-07-15

    investigated. 4. References: Foster. J.C.. C. del Pozo. K. Groves, and J.-P. St. Maurice , Radar observations of the onlst of current drivenr instabilities... Clemmons , and F. S. Mozer, High-resolution sounding rocket observations of large-amplitude Alfvin waves, J. Geophys. Res., 95, 12157-12171, 1990. [51 Breit...equilibrium. Can. J. Phys., 38, 1114-1133, 1960. i16] Foster, J. C., C. del Pozo, K. Groves, and J.-P. St. Maurice , Radar observations of the onset of

  17. Sea-level proxies in Holocene raised beach ridge deposits (Greenland) revealed by ground-penetrating radar.

    Science.gov (United States)

    Nielsen, Lars; Bendixen, Mette; Kroon, Aart; Hede, Mikkel Ulfeldt; Clemmensen, Lars B; Weβling, Ronny; Elberling, Bo

    2017-04-19

    Identification of sea-level proxies is important for reconstruction of past sea-level variation. Methods for reconstructing Holocene relative sea-level curves are crucial for quantification of the impact of Greenland ice thickness variation on global sea level and vertical land movement. Arctic beach ridges constitute important potential archives of sea-level variation. However, their surface morphology may have undergone modification since deposition due to freezing/thawing processes and erosion, and their morphology may therefore not be trustworthy for sea-level reconstruction. Therefore, geophysical imaging is used to examine the internal structures of the beach ridges and to define a sea-level proxy unaffected by surface processes. The GPR reflections from study sites in West and South Greenland show deposition of beachface deposits and upper shoreface deposits; the contact between steeply dipping beachface reflections and less-dipping shoreface reflections is used as sea-level proxy. Numerous points are identified along GPR transects facilitating reconstruction of relative sea-level variation of hitherto unprecedented resolution. Erosional events and deformation caused by freezing/thawing processes are clearly delineated. The approach constitutes a solid base for reconstruction of relative sea-level curves affected by a well-defined vertical land movement history since the studied beach ridge systems represent long time intervals and only relatively small spatial extents.

  18. Conceptual Architecture to Measure the Effects of Subauroral Polarization Streams on Radar Operations

    Science.gov (United States)

    2016-09-01

    Institute of Technology Air University Air Education and Training Command In Partial Fulfillment of the Requirements for the Degree of Master of...and estimate how much SAPS effects radar operations, the execution of over the horizon radars and documentation of clutter should use the high- level ...for various operations will be portrayed in a systems model to show all parts involved in the measurements. The degree of radar interference due to

  19. Desk Congest Desktop Congesting Software for Desktop Clutter Congestion

    Directory of Open Access Journals (Sweden)

    Solomon A. Adepoju

    2015-06-01

    Full Text Available Abstract The computer desktop environment is a working environment which can be likened unto a users desk in homes and offices. Often times the computer desktop get cluttered with files either as shortcuts used for quick links files stored temporarily to be accessed later or just being dumped there for no vivid reasons. However previous researches have shown that cluttered desktop affects users productivity and getting these files organized is a laborious task for most users. To be able to conveniently alleviate the effect clutters have on users performances and productivity there is need for third party software that will help get the desktop environment organized in a logical and efficient manner. It is to this end that desktop decongesting software is being designed and implemented to help curb clutter problems which existing tools have only partially addressed. The system is designed using Visual Basic .Net and it proves to be effective in tackling desktop congestion problem.

  20. Inference-Based Surface Reconstruction of Cluttered Environments

    KAUST Repository

    Biggers, K.; Keyser, J.

    2012-01-01

    guided by rules for fitting high-quality surface patches obtained from these prior models. We demonstrate the application of this algorithm on several example data sets containing heavy clutter and occlusion. © 2012 IEEE.

  1. CFD Investigation of Flow Past Idealized Engine Nacelle Clutter

    National Research Council Canada - National Science Library

    Casper, Matthew S

    2007-01-01

    ...), to resolve the flow-field dynamics inside the clutter element and determine mechanisms accounting for the failure of suppressant spray droplets from traversing the array under low-speed, free-stream conditions (ReD = 1, 575...

  2. Generating Correlated Gamma Sequences for Sea-Clutter Simulation

    Science.gov (United States)

    2012-03-01

    generation of correlated Gamma random fields via SIRP theory is examined in [Conte et al. 1991, Armstrong & Griffiths 1991]. In these papers , the Gamma...2 〉2 + |〈x[n]x∗[n+ k]〉|2 . (4) Because 〈 |x|2 〉2 = z̄2 and |〈x[n]x∗[n+ k]〉|2 ≥ 0, this results in 〈z[n]z[n+ k]〉 ≥ z̄2 if the real- isation of z[n] is...linear map- ping. In a practical situation, a process with a given auto-covariance function would be specified. It is shown that by using an

  3. Polarization Techniques for Mitigation of Low Grazing Angle Sea Clutter

    Science.gov (United States)

    2017-01-01

    is better in practice. Dimitris Manolakis Acknowledgments One can undertake learning a vast, deep area of knowledge by entering its dark pool slowly...reformed English lit major can only carry a metaphor so far. There are many people deserving of my deepest thanks who happen to swim mostly in other pools...challenging to detect. Solutions posed in the literature to date have been either computationally impractical or lacked robustness. This dissertation

  4. Distribution analysis of segmented wave sea clutter in littoral environments

    CSIR Research Space (South Africa)

    Strempel, MD

    2015-10-01

    Full Text Available are then fitted against the K-distribution. It is shown that the approach can accurately describe specific sections of the wave with a reduced error between actual and estimated distributions. The improved probability density function (PDF) representation...

  5. Induced vibrations facilitate traversal of cluttered obstacles

    Science.gov (United States)

    Thoms, George; Yu, Siyuan; Kang, Yucheng; Li, Chen

    When negotiating cluttered terrains such as grass-like beams, cockroaches and legged robots with rounded body shapes most often rolled their bodies to traverse narrow gaps between beams. Recent locomotion energy landscape modeling suggests that this locomotor pathway overcomes the lowest potential energy barriers. Here, we tested the hypothesis that body vibrations induced by intermittent leg-ground contact facilitate obstacle traversal by allowing exploration of locomotion energy landscape to find this lowest barrier pathway. To mimic a cockroach / legged robot pushing against two adjacent blades of grass, we developed an automated robotic system to move an ellipsoidal body into two adjacent beams, and varied body vibrations by controlling an oscillation actuator. A novel gyroscope mechanism allowed the body to freely rotate in response to interaction with the beams, and an IMU and cameras recorded the motion of the body and beams. We discovered that body vibrations facilitated body rolling, significantly increasing traversal probability and reducing traversal time (P locomotor pathways in complex 3-D terrains.

  6. X-Band high range resolution radar measurements of sea surface forward scatter at low grazing angles

    CSIR Research Space (South Africa)

    Smit, JC

    2008-05-01

    Full Text Available in the sea surface forward scatter component exists. Based on this measurement, we propose a temporal correlation extension to an existing low-angle propagation model, together with a correlation filter structure to realize the correlation extension...

  7. Global Infrasound Association Based on Probabilistic Clutter Categorization

    Science.gov (United States)

    Arora, Nimar; Mialle, Pierrick

    2016-04-01

    The IDC advances its methods and continuously improves its automatic system for the infrasound technology. The IDC focuses on enhancing the automatic system for the identification of valid signals and the optimization of the network detection threshold by identifying ways to refine signal characterization methodology and association criteria. An objective of this study is to reduce the number of associated infrasound arrivals that are rejected from the automatic bulletins when generating the reviewed event bulletins. Indeed, a considerable number of signal detections are due to local clutter sources such as microbaroms, waterfalls, dams, gas flares, surf (ocean breaking waves) etc. These sources are either too diffuse or too local to form events. Worse still, the repetitive nature of this clutter leads to a large number of false event hypotheses due to the random matching of clutter at multiple stations. Previous studies, for example [1], have worked on categorization of clutter using long term trends on detection azimuth, frequency, and amplitude at each station. In this work we continue the same line of reasoning to build a probabilistic model of clutter that is used as part of NETVISA [2], a Bayesian approach to network processing. The resulting model is a fusion of seismic, hydroacoustic and infrasound processing built on a unified probabilistic framework. References: [1] Infrasound categorization Towards a statistics based approach. J. Vergoz, P. Gaillard, A. Le Pichon, N. Brachet, and L. Ceranna. ITW 2011 [2] NETVISA: Network Processing Vertically Integrated Seismic Analysis. N. S. Arora, S. Russell, and E. Sudderth. BSSA 2013

  8. Past sea-level data from Lakse Bugt, Disko Island, West Greenland from ground-penetrating radar data

    DEFF Research Database (Denmark)

    Emerich Souza, Priscila; Nielsen, Lars; Kroon, Aart

    Beach-ridge deposits have been used as sea-level indicators in numerous studies from temperate coastal regions. However, their present surface morphology in artic regions may not accurately correspond to past sea-level, because subsequent surface erosion, solifluction processes and/or later...... sediment deposition may have altered the surface significantly. The internal structure of these beach ridges, however, is often well-preserved and thus constitutes an important key to reconstruction of past sea levels as seen elsewhere. In the present study, high-resolution reflection GPR data and high......-precision topographic data were collected at Lakse Bugt (Disko Island, West Greenland) using a shielded 250 MHz antennae system and a RTK-Trimble R8 DGPS, respectively. Three transects were collected across a sequence of fossil, raised beach ridge deposits, and two transects were obtained across modern beach deposits...

  9. Testing sea-level markers observed in ground-penetrating radar data from Feddet, south-eastern Denmark

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Nielsen, Lars; Clemmensen, Lars B

    2012-01-01

    a number of profile lines across less than c. 60 years old berm, beach ridge and swale structures at the Feddet peninsula. The GPR images allow us to interpret internal sedimentary architecture, and here we focus especially on the identification of downlapping reflections, which are interpreted to mark...... fluctuations in past sea level due to variations in tidal effects and meteorological conditions (isostatic rebound is expected to have a minimal effect on Feddet (Hansen et al., 2011)). Comparison with existing time series of measurements of actual sea level from the Danish Maritime Safety Administration (from...

  10. Radar Scan Methods in Modern Multifunctional Radars

    Directory of Open Access Journals (Sweden)

    V. N. Skosyrev

    2014-01-01

    Full Text Available Considered urgent task of organizing the review space in modern multifunctional radar systems shall review the space in a wide range of elevation angles from minus 5 to 60-80 degrees and 360 degrees azimuth. MfRLS this type should provide an overview of the zone for a limited time (2-3 sec, detecting a wide range of subtle high and low-flying targets. The latter circumstance requires the organization to select targets against the background of reflections from the underlying surface and local objects (MP. When providing an overview of the space taken into account the need to increase not only the noise immunity, and survivability.Two variants of the review of space in the elevation plane in the solid-state AESA radar. In the first case the overview space narrow beam by one beam. In the second - the transfer of DNA is formed, covering the whole sector of responsibility in elevation and at the reception beam is formed in spetsvychislitele (CB as a result of the signal processing of digitized after emitters antenna web. The estimations of the parameters specific to the multifunction radar SAM air and missile defense. It is shown that in a number of practically important cases, preference should be given clearly one of the methods described review of space.The functional scheme with AESA radar for both variants of the review. Necessary to analyze their differences. Contains the problem of increasing the cost of MfRLS with digital beamforming DNA with increasing bandwidth probing signal being processed.Noted drawbacks of MfRLS with digital beamforming beam. Including: reduced accuracy of the coordinates at low elevation angles, the complexity of the organization of thermal regime of the solid element base using quasi-continuous signal with a low duty cycle. Shows their fundamentally unavoidable in the steppe and desert areas with uneven terrain (Kazakhstan, China, the Middle East.It is shown that for MfRLS working in strong clutter, more preferably

  11. Monitoring of sinkholes and subsidence affecting the Jordanian coast of the Dead Sea through Synthetic Aperture Radar data and last generation Sentinel-1 data

    Science.gov (United States)

    Tessari, Giulia; Riccardi, Paolo; Lecci, Daniele; Pasquali, Paolo; Floris, Mario

    2017-04-01

    Since the mid-1980s the coast of the Dead Sea is affected by sinkholes occurring over and around the emerged mud and salt flats. Strong subsidence and landslides also affect some segments of the coast. Nowadays, several thousands of sinkholes attest that the degradation of the Dead Sea coast is worsening. Furthermore, soil deformations are interesting the main streets running along both the Israeli and Jordanian sides of the Dead Sea. These hazards are due to the dramatic dropping of the Dead Sea level, characterized by an increasing rate from about 60 cm/yr in the 1970s up to 1 m/yr in the 2000s, which provokes a lowering of the fresh-saline groundwater interface, replacing the hypersaline groundwater with fresh water and causing a consequent erosion of the subsurface salt layers. Subsidence, sinkholes, river erosion and landslides damage bridges, roads, dikes, houses, factories worsening this ongoing disaster. One of the most emblematic effects is the catastrophic collapse of a 12-km newly constructed dyke, located on the Lisan Peninsula (Jordan), occurred in 2000. Differential Interferometric Synthetic Aperture Radar (DInSAR) techniques and Advanced stacking DInSAR techniques (A-DInSAR) were applied to investigate sinkholes and subsidence affecting the Jordanian coast of the Dead Sea. The use of SAR data already proof to be efficient on the risk management of the area, allowing to identify a vulnerable portion of an Israeli highway, averting a possible collapse. Deformation analysis has been focused on the Ghor Al Haditha area and Lisan peninsula, located in the South-Eastern part of the lake coast. The availability of a huge database of SAR data, since the beginning of the 90s, allowed to observe the evolution of the displacements which are damaging this area. Furthermore, last generation Sentinel-1 data, acquired by the ESA mission, were processed to obtain information about the recent evolution of the subsidence and sinkholes affecting the study area, from

  12. Public attitudes toward-and identification of-cluttering and stuttering in Norway and Puerto Rico.

    Science.gov (United States)

    St Louis, Kenneth O; Sønsterud, Hilda; Carlo, Edna J; Heitmann, Ragnhild R; Kvenseth, Helene

    2014-12-01

    The study sought to compare public attitudes toward cluttering versus stuttering in Norway and Puerto Rico and to compare respondents' identification of persons known with these fluency disorders. After reading lay definitions of cluttering and stuttering, three samples of adults from Norway and three from Puerto Rico rated their attitudes toward cluttering and/or stuttering on modified versions of the POSHA-Cl (for cluttering) and POSHA-S (for stuttering). They also identified children and adults whom they knew who either or both manifested cluttering or stuttering. Attitudes toward cluttering were essentially unaffected by rating either cluttering only or combined cluttering and stuttering on the same questionnaire in both countries. The same was also true of stuttering. Attitudes were very similar toward both disorders although slightly less positive for cluttering. Norwegian attitudes toward both disorders were generally more positive than Puerto Rican attitudes. The average respondent identified slightly more than one fluency disorder, a higher percentage for stuttering than cluttering and higher for adults than children. Cluttering-stuttering was rarely identified. Given a lay definition, this study confirmed that adults from diverse cultures hold attitudes toward cluttering that are similar to-but somewhat less positive than-their attitudes toward stuttering. It also confirmed that adults can identify cluttering among people they know, although less commonly than stuttering. Design controls in this study assured that consideration of stuttering did not affect either the attitudes or identification results for cluttering. The reader will be able to: (a) describe the effects-or lack thereof-of considerations of stuttering on attitudes toward cluttering; (b) describe differences in public identification of children and adults who either clutter or stutter; (c) describe differences between attitudes toward cluttering and stuttering in Norway and Puerto Rico

  13. Quantum radar

    CERN Document Server

    Lanzagorta, Marco

    2011-01-01

    This book offers a concise review of quantum radar theory. Our approach is pedagogical, making emphasis on the physics behind the operation of a hypothetical quantum radar. We concentrate our discussion on the two major models proposed to date: interferometric quantum radar and quantum illumination. In addition, this book offers some new results, including an analytical study of quantum interferometry in the X-band radar region with a variety of atmospheric conditions, a derivation of a quantum radar equation, and a discussion of quantum radar jamming.This book assumes the reader is familiar w

  14. Science requirements for free-flying imaging radar (FIREX) experiment for sea ice, renewable resources, nonrenewable resources and oceanography

    Science.gov (United States)

    Carsey, F.

    1982-01-01

    A future bilateral SAR program was studied. The requirements supporting a SAR mission posed by science and operations in sea-ice-covered waters, oceanography, renewable resources, and nonrenewable resources are addressed. The instrument, mission, and program parameters were discussed. Research investigations supporting a SAR flight and the subsequent overall mission requirements and tradeoffs are summarized.

  15. Volcanic and Tectonic Activity in the Red Sea Region (2004-2013): Insights from Satellite Radar Interferometry and Optical Imagery

    KAUST Repository

    Xu, Wenbin

    2015-01-01

    due to insufficient in-situ data and remoteness of some of the activity. In this dissertation, I have used satellite remote sensing to derive new information about several recent volcanic and tectonic events in the Red Sea region. I first report

  16. Inference-Based Surface Reconstruction of Cluttered Environments

    KAUST Repository

    Biggers, K.

    2012-08-01

    We present an inference-based surface reconstruction algorithm that is capable of identifying objects of interest among a cluttered scene, and reconstructing solid model representations even in the presence of occluded surfaces. Our proposed approach incorporates a predictive modeling framework that uses a set of user-provided models for prior knowledge, and applies this knowledge to the iterative identification and construction process. Our approach uses a local to global construction process guided by rules for fitting high-quality surface patches obtained from these prior models. We demonstrate the application of this algorithm on several example data sets containing heavy clutter and occlusion. © 2012 IEEE.

  17. Radar Chart

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — The Radar Chart collection is an archived product of summarized radar data. The geographic coverage is the 48 contiguous states of the United States. These hourly...

  18. Doppler Radar Vital Signs Detection Method Based on Higher Order Cyclostationary.

    Science.gov (United States)

    Yu, Zhibin; Zhao, Duo; Zhang, Zhiqiang

    2017-12-26

    Due to the non-contact nature, using Doppler radar sensors to detect vital signs such as heart and respiration rates of a human subject is getting more and more attention. However, the related detection-method research meets lots of challenges due to electromagnetic interferences, clutter and random motion interferences. In this paper, a novel third-order cyclic cummulant (TOCC) detection method, which is insensitive to Gaussian interference and non-cyclic signals, is proposed to investigate the heart and respiration rate based on continuous wave Doppler radars. The k -th order cyclostationary properties of the radar signal with hidden periodicities and random motions are analyzed. The third-order cyclostationary detection theory of the heart and respiration rate is studied. Experimental results show that the third-order cyclostationary approach has better estimation accuracy for detecting the vital signs from the received radar signal under low SNR, strong clutter noise and random motion interferences.

  19. Radar Fundamentals, Presentation

    OpenAIRE

    Jenn, David

    2008-01-01

    Topics include: introduction, radar functions, antennas basics, radar range equation, system parameters, electromagnetic waves, scattering mechanisms, radar cross section and stealth, and sample radar systems.

  20. Notch Filter Analysis and Its Application in Passive Coherent Location Radar (in English

    Directory of Open Access Journals (Sweden)

    Li Ji-chuan

    2015-01-01

    Full Text Available The Normalized Least-Mean-Squares (NLMS algorithm is widely used to cancel the direct and multiple path interferences in Passive Coherent Location (PCL radar systems. This study proposes that the interference cancelation using the NLMS algorithm and the calculation of the radar Cross Ambiguity Function (CAF can be modeled as a notch filter, with the notch located at zero Doppler frequency in the surface of the radar CAF. The analysis shows that the notch’s width and depth are closely related to the step size of the NLMS algorithm. Subsequently, the effect of the notch in PCL radar target detection is analyzed. The results suggest that the detection performance of the PCL radar deteriorates because of the wide notch. Furthermore, the Nonuniform NLMS (NNLMS algorithm is proposed for removing the clutter with the Doppler frequency by using notch filtering. A step-size matrix is adopted to mitigate the low Doppler frequency clutter and lower the floor of the radar CAF. With the step-size matrix, can be obtained notches of different depths and widths in different range units of the CAF, which can filter the low Doppler frequency clutter. In addition, the convergence rate of the NNLMS algorithm is better than that of the traditional NLMS algorithm. The validity of the NNLMS algorithm is verified by experimental results.

  1. Local region power spectrum-based unfocused ship detection method in synthetic aperture radar images

    Science.gov (United States)

    Wei, Xiangfei; Wang, Xiaoqing; Chong, Jinsong

    2018-01-01

    Ships on synthetic aperture radar (SAR) images will be severely defocused and their energy will disperse into numerous resolution cells under long SAR integration time. Therefore, the image intensity of ships is weak and sometimes even overwhelmed by sea clutter on SAR image. Consequently, it is hard to detect the ships from SAR intensity images. A ship detection method based on local region power spectrum of SAR complex image is proposed. Although the energies of the ships are dispersed on SAR intensity images, their spectral energies are rather concentrated or will cause the power spectra of local areas of SAR images to deviate from that of sea surface background. Therefore, the key idea of the proposed method is to detect ships via the power spectra distortion of local areas of SAR images. The local region power spectrum of a moving target on SAR image is analyzed and the way to obtain the detection threshold through the probability density function (pdf) of the power spectrum is illustrated. Numerical P- and L-band airborne SAR ocean data are utilized and the detection results are also illustrated. Results show that the proposed method can well detect the unfocused ships, with a detection rate of 93.6% and a false-alarm rate of 8.6%. Moreover, by comparing with some other algorithms, it indicates that the proposed method performs better under long SAR integration time. Finally, the applicability of the proposed method and the way of parameters selection are also discussed.

  2. Radar rainfall estimation in a hilly environment and implications for runoff modeling

    Science.gov (United States)

    Hazenberg, Pieter; Leijnse, Hidde; Uijlenhoet, Remko

    2010-05-01

    Radars are known for their ability to obtain a wealth of information about the spatial stormfield characteristics. Unfortunately, rainfall estimates obtained by this instrument are known to be affected by multiple sources of error. Especially for stratiform precipitation systems, the quality of radar rainfall estimates starts to decrease at relatively close ranges. In the current study the hydrological potential of weather radar is analyzed during a winter half-year for the hilly region of the Belgian Ardennes. A correction algorithm is proposed taking into account attenuation, ground clutter, anomalous propagation, the vertical profile of reflectivity (VPR) and advection. No final bias correction with respect to rain gauge data were implemented, because that does not add to a better understanding of the quality of the radar. Largest quality improvements in the radar data are obtained by ground clutter removal. The influence of VPR correction and advection depends on the precipitation system observed. Overall, the radar shows an underestimation as compared to the rain gauges, which becomes smaller after averaging at the scale of the medium-sized Ourthe catchment. Remaining differences between both devices can mainly be attributed to an improper choice of the Z-R relationship. Conceptual rainfall-runoff simulations show similar results using either catchment average radar or rain gauge data, although the largest discharge peak observed, is seriously underestimated when applying radar data. Overall, for hydrological applications corrected weather radar information in a hilly environment can be used up to 70 km during a winter half-year.

  3. Social Radar

    Science.gov (United States)

    2012-01-01

    RTA HFM-201/RSM PAPER 3 - 1 © 2012 The MITRE Corporation. All Rights Reserved. Social Radar Barry Costa and John Boiney MITRE Corporation...defenders require an integrated set of capabilities that we refer to as a “ social radar.” Such a system would support strategic- to operational-level...situation awareness, alerting, course of action analysis, and measures of effectiveness for each action undertaken. Success of a social radar

  4. Planetary Radar

    Science.gov (United States)

    Neish, Catherine D.; Carter, Lynn M.

    2015-01-01

    This chapter describes the principles of planetary radar, and the primary scientific discoveries that have been made using this technique. The chapter starts by describing the different types of radar systems and how they are used to acquire images and accurate topography of planetary surfaces and probe their subsurface structure. It then explains how these products can be used to understand the properties of the target being investigated. Several examples of discoveries made with planetary radar are then summarized, covering solar system objects from Mercury to Saturn. Finally, opportunities for future discoveries in planetary radar are outlined and discussed.

  5. Synthetic range profiling, ISAR imaging of sea vessels and feature extraction, using a multimode radar to classify targets: initial results from field trials

    CSIR Research Space (South Africa)

    Abdul Gaffar, MY

    2011-04-01

    Full Text Available tanazi@kacst.edu.sa, aazamil@kacst.edu.sa Abstract?This paper describes the design and working principles of an experimental multimode radar with a stepped-frequency Synthetic Range Profiling (SRP) and Inverse Synthetic Aperture Radar (ISAR...

  6. Multi-contact Variable-Compliance Manipulation in Extreme Clutter

    Science.gov (United States)

    2014-06-16

    house to find eggs and young. (b) When noodling , people find catfish holes from which to pull fish out. (c)-(d) A person makes contact along his...Figure 7: Haptic Map of detected rigid contacts. by mapping all the rigid taxels at every time- instant . For visualizing the haptic map, we use point...the environment while reaching into clutter. (a) A raccoon reaches into a bird house to find eggs and young. (b) When noodling , people find catfish

  7. Trade Mark Cluttering: An Exploratory Report Commissioned by UKIPO

    OpenAIRE

    von Graevenitz, Georg; Greenhalgh, Christine; Helmers, Christian; Schautschick, Philipp

    2012-01-01

    This report explores the problem of “cluttering” of trade mark registers. The report consists of two parts: the first presents a conceptual discussion of “cluttering” of trade mark registers. The second part provides an exploratory empirical analysis of trade mark applications at the UK Intellectual Property Office (UKIPO) and the European trade mark office (OHIM). This part contains results of a descriptive and an econometric analysis. According to our definition, cluttering arises where fir...

  8. Enhanced Algorithms for EO/IR Electronic Stabilization, Clutter Suppression, and Track-Before-Detect for Multiple Low Observable Targets

    Science.gov (United States)

    Tartakovsky, A.; Brown, A.; Brown, J.

    The paper describes the development and evaluation of a suite of advanced algorithms which provide significantly-improved capabilities for finding, fixing, and tracking multiple ballistic and flying low observable objects in highly stressing cluttered environments. The algorithms have been developed for use in satellite-based staring and scanning optical surveillance suites for applications including theatre and intercontinental ballistic missile early warning, trajectory prediction, and multi-sensor track handoff for midcourse discrimination and intercept. The functions performed by the algorithms include electronic sensor motion compensation providing sub-pixel stabilization (to 1/100 of a pixel), as well as advanced temporal-spatial clutter estimation and suppression to below sensor noise levels, followed by statistical background modeling and Bayesian multiple-target track-before-detect filtering. The multiple-target tracking is performed in physical world coordinates to allow for multi-sensor fusion, trajectory prediction, and intercept. Output of detected object cues and data visualization are also provided. The algorithms are designed to handle a wide variety of real-world challenges. Imaged scenes may be highly complex and infinitely varied -- the scene background may contain significant celestial, earth limb, or terrestrial clutter. For example, when viewing combined earth limb and terrestrial scenes, a combination of stationary and non-stationary clutter may be present, including cloud formations, varying atmospheric transmittance and reflectance of sunlight and other celestial light sources, aurora, glint off sea surfaces, and varied natural and man-made terrain features. The targets of interest may also appear to be dim, relative to the scene background, rendering much of the existing deployed software useless for optical target detection and tracking. Additionally, it may be necessary to detect and track a large number of objects in the threat cloud

  9. Comet radar explorer

    Science.gov (United States)

    Farnham, Tony; Asphaug, Erik; Barucci, Antonella; Belton, Mike; Bockelee-Morvan, Dominique; Brownlee, Donald; Capria, Maria Teresa; Carter, Lynn; Chesley, Steve; Farnham, Tony; Gaskell, Robert; Gim, Young; Heggy, Essam; Herique, Alain; Klaasen, Ken; Kofman, Wlodek; Kreslavsky, Misha; Lisse, Casey; Orosei, Roberto; Plaut, Jeff; Scheeres, Dan

    will enjoy significant simplifying benefits compared to using the same instrument for Mars or lunar radar science: (1) The proximity of operations leads to a much higher signal to noise, as much as +30 dB. (2) The lack of an ionosphere simplifies data modeling and analysis. (3) The body is globally illuminated during every data acquisition, minimizing ambiguity or 'clutter' and allowing for tomographic reconstruction. What is novel is the data processing, where instead of a planar radargram approach we coherently process the data into an image of the deep interior. CORE thus uses a MARSIS-SHARAD heritage radar to make coherent reflection sounding measurements, a 'CAT SCAN' of a comet nucleus. What is unique about this mission compared to the Mars radars mentioned above, is that the target is a finite mass of dirty ice in free space, rather than a sheet of dirty ice draped on a planet surface. The depth of penetration (kilometers), attainable resolution (decameters), and the target materials, are more or less the same. This means that the science story is robust, and the radar implementation is robust. The target is comet 10P/Tempel 2, discovered by Wilhelm Tempel in 1873 and observed on most apparitions since. It has been extensively studied, in part because of interest as a CRAF target in the mid-1980s, and much is known about it. Tempel 2 is one of the largest known comet nuclei, 16×8×8 km (about the same size as Halley) [1] and has rotation period 8.9 hours [3,5,6,7,9]. The spin state is evolving with time, spinning up by ˜10 sec per perihelion pass [5,7]. The comet is active, but not exceedingly so, especially given its size. The water production is measured at ˜ 4 × 1028 mol/sec at its peak [2], a factor of 25 lower than comet Halley, and it is active over only ˜2% of its surface. The dust environment is well known, producing a factor of ˜100 less dust than Halley. Comet References: [1] A'Hearn et al., ApJ 347, 1155, 1989 [2] Feldman and Festou, ACM 1991, p

  10. Performance of high-resolution X-band radar for rainfall measurement in The Netherlands

    Directory of Open Access Journals (Sweden)

    C. Z. van de Beek

    2010-02-01

    Full Text Available This study presents an analysis of 195 rainfall events gathered with the X-band weather radar SOLIDAR and a tipping bucket rain gauge network near Delft, The Netherlands, between May 1993 and April 1994. The aim of this paper is to present a thorough analysis of a climatological dataset using a high spatial (120 m and temporal (16 s resolution X-band radar. This makes it a study of the potential for high-resolution rainfall measurements with non-polarimetric X-band radar over flat terrain. An appropriate radar reflectivity – rain rate relation is derived from measurements of raindrop size distributions and compared with radar – rain gauge data. The radar calibration is assessed using a long-term comparison of rain gauge measurements with corresponding radar reflectivities as well as by analyzing the evolution of the stability of ground clutter areas over time. Three different methods for ground clutter correction as well as the effectiveness of forward and backward attenuation correction algorithms have been studied. Five individual rainfall events are discussed in detail to illustrate the strengths and weaknesses of high-resolution X-band radar and the effectiveness of the presented correction methods. X-band radar is found to be able to measure the space-time variation of rainfall at high resolution, far greater than what can be achieved by rain gauge networks or a typical operational C-band weather radar. On the other hand, SOLIDAR can suffer from receiver saturation, wet radome attenuation as well as signal loss along the path. During very strong convective situations the signal can even be lost completely. In combination with several rain gauges for quality control, high resolution X-band radar is considered to be suitable for rainfall monitoring over relatively small (urban catchments. These results offer great prospects for the new high resolution polarimetric doppler X-band radar IDRA.

  11. Energy Based Clutter Filtering for Vector Flow Imaging

    DEFF Research Database (Denmark)

    Villagómez Hoyos, Carlos Armando; Jensen, Jonas; Ewertsen, Caroline

    2017-01-01

    for obtaining vector flow measurements, since the spectra overlaps at high beam-to-flow angles. In this work a distinct approach is proposed, where the energy of the velocity spectrum is used to differentiate among the two signals. The energy based method is applied by limiting the amplitude of the velocity...... spectrum function to a predetermined threshold. The effect of the clutter filtering is evaluated on a plane wave (PW) scan sequence in combination with transverse oscillation (TO) and directional beamforming (DB) for velocity estimation. The performance of the filter is assessed by comparison...

  12. Radar rainfall estimation of stratiform winter precipitation in the Belgian Ardennes

    Science.gov (United States)

    Hazenberg, P.; Leijnse, H.; Uijlenhoet, R.

    2011-02-01

    Radars are known for their ability to obtain a wealth of information about spatial storm field characteristics. Unfortunately, rainfall estimates obtained by this instrument are known to be affected by multiple sources of error. Especially for stratiform precipitation systems, the quality of radar rainfall estimates starts to decrease at relatively close ranges. In the current study, the hydrological potential of weather radar is analyzed during a winter half-year for the hilly region of the Belgian Ardennes. A correction algorithm is proposed which corrects the radar data for errors related to attenuation, ground clutter, anomalous propagation, the vertical profile of reflectivity (VPR), and advection. No final bias correction with respect to rain gauge data was implemented because such an adjustment would not add to a better understanding of the quality of the radar data. The impact of the different corrections is assessed using rainfall information sampled by 42 hourly rain gauges. The largest improvement in the quality of the radar data is obtained by correcting for ground clutter. The impact of VPR correction and advection depends on the spatial variability and velocity of the precipitation system. Overall during the winter period, the radar underestimates the amount of precipitation as compared to the rain gauges. Remaining differences between both instruments can be attributed to spatial and temporal variability in the type of precipitation, which has not been taken into account.

  13. Radar Search and Detection With the CASA 212 S43 Aircraft

    National Research Council Canada - National Science Library

    Borges, Jose M

    2004-01-01

    .... The model can use given periscope radar cross section data, or roughly calculate radar cross section given assumptions about exposed periscope height above the sea-surface and sea-state conditions. Submarine evasion due to radar counter-detection is also modeled.

  14. Weather Radar Stations

    Data.gov (United States)

    Department of Homeland Security — These data represent Next-Generation Radar (NEXRAD) and Terminal Doppler Weather Radar (TDWR) weather radar stations within the US. The NEXRAD radar stations are...

  15. Beach-ridge architecture constrained by beach topography and Ground-Penetrating Radar, Itilleq (Lakse Bugt), Disko, Greenland – Implications for sea-level reconstructions

    DEFF Research Database (Denmark)

    Emerich Souza, Priscila; Kroon, Aart; Nielsen, Lars

    2018-01-01

    Detailed topographical data and high-resolution ground-penetrating radar (GPR) reflection data are presented from the present-day beach and across successive raised beach-ridges at Itilleq (Disko, West Greenland). In the western part of our study area, the present low-tide level is well-marked by......Detailed topographical data and high-resolution ground-penetrating radar (GPR) reflection data are presented from the present-day beach and across successive raised beach-ridges at Itilleq (Disko, West Greenland). In the western part of our study area, the present low-tide level is well...... beach-ridge GPR profiles. Most of them are located at the boundary between a unit with reflection characteristics representing palaeo foreshore deposits, and a deeper and more complex radar unit characterized by diffractions, which, however, is not penetrated to large depths by the GPR signals. Based...

  16. 5 year radar-based rainfall statistics: disturbances analysis and development of a post-correction scheme for the German radar composite

    Science.gov (United States)

    Wagner, A.; Seltmann, J.; Kunstmann, H.

    2015-02-01

    A radar-based rainfall statistic demands high quality data that provide realistic precipitation amounts in space and time. Instead of correcting single radar images, we developed a post-correction scheme for long-term composite radar data that corrects corrupted areas, but preserves the original precipitation patterns. The post-correction scheme is based on a 5 year statistical analysis of radar composite data and its constituents. The accumulation of radar images reveals artificial effects that are not visible in the individual radar images. Some of them are already inherent to single radar data such as the effect of increasing beam height, beam blockage or clutter remnants. More artificial effects are introduced in the process of compositing such as sharp gradients at the boundaries of overlapping areas due to different beam heights and resolution. The cause of these disturbances, their behaviour with respect to reflectivity level, season or altitude is analysed based on time-series of two radar products: the single radar reflectivity product PX for each of the 16 radar systems of the German Meteorological Service (DWD) for the time span 2000 to 2006 and the radar composite product RX of DWD from 2005 through to 2009. These statistics result in additional quality information on radar data that is not available elsewhere. The resulting robust characteristics of disturbances, e.g. the dependency of the frequencies of occurrence of radar reflectivities on beam height, are then used as a basis for the post-correction algorithm. The scheme comprises corrections for shading effects and speckles, such as clutter remnants or overfiltering, as well as for systematic differences in frequencies of occurrence of radar reflectivities between the near and the far ranges of individual radar sites. An adjustment to rain gauges is also included. Applying this correction, the Root-Mean-Square-Error for the comparison of radar derived annual rain amounts with rain gauge data

  17. The Development of the ITU-R Terrestrial Clutter Loss Model

    DEFF Research Database (Denmark)

    Medbo, Jonas; Larsson, Christina; Olsson, Bengt Erik

    2018-01-01

    The ITU-R has recently published a new Recommendation giving methods for the estimation of clutter loss at frequencies between 30 MHz and 100 GHz. This paper provides an overview of the methods. In particular, the derivation and form of the new clutter model for terrestrial paths is described in ...

  18. Object Recognition in Clutter: Cortical Responses Depend on the Type of Learning

    Directory of Open Access Journals (Sweden)

    Jay eHegdé

    2012-06-01

    Full Text Available Theoretical studies suggest that the visual system uses prior knowledge of visual objects to recognize them in visual clutter, and posit that the strategies for recognizing objects in clutter may differ depending on whether or not the object was learned in clutter to begin with. We tested this hypothesis using functional magnetic resonance imaging (fMRI of human subjects. We trained subjects to recognize naturalistic, yet novel objects in strong or weak clutter. We then tested subjects’ recognition performance for both sets of objects in strong clutter. We found many brain regions that were differentially responsive to objects during object recognition depending on whether they were learned in strong or weak clutter. In particular, the responses of the left fusiform gyrus reliably reflected, on a trial-to-trial basis, subjects’ object recognition performance for objects learned in the presence of strong clutter. These results indicate that the visual system does not use a single, general-purpose mechanism to cope with clutter. Instead, there are two distinct spatial patterns of activation whose responses are attributable not to the visual context in which the objects were seen, but to the context in which the objects were learned.

  19. Bistatic Forward Scattering Radar Detection and Imaging

    Directory of Open Access Journals (Sweden)

    Hu Cheng

    2016-06-01

    Full Text Available Forward Scattering Radar (FSR is a special type of bistatic radar that can implement image detection, imaging, and identification using the forward scattering signals provided by the moving targets that cross the baseline between the transmitter and receiver. Because the forward scattering effect has a vital significance in increasing the targets’ Radar Cross Section (RCS, FSR is quite advantageous for use in counter stealth detection. This paper first introduces the front line technology used in forward scattering RCS, FSR detection, and Shadow Inverse Synthetic Aperture Radar (SISAR imaging and key problems such as the statistical characteristics of forward scattering clutter, accurate parameter estimation, and multitarget discrimination are then analyzed. Subsequently, the current research progress in FSR detection and SISAR imaging are described in detail, including the theories and experiments. In addition, with reference to the BeiDou navigation satellite, the results of forward scattering experiments in civil aircraft detection are shown. Finally, this paper considers future developments in FSR target detection and imaging and presents a new, promising technique for stealth target detection.

  20. Minefield overwatch using moving target indicator radar

    Science.gov (United States)

    Donadio, Anthony; Ewing, Robert; Kenneally, William J.; Santapietro, John J.

    1999-07-01

    Traditional antipersonnel land mines are an effective military tool, but they are unable to distinguish friend from foe, or civilian from military personnel. The concept described here uses an advanced moving target indicator (MTI) radar to scan the minefield in order to detect movement towards or within the minefield, coupled with visual identification by a human operator and a communication link for command and control. Selected mines in the minefield can then be activated by means of the command link. In order to demonstrate this concept, a 3D, interactive simulation has been developed. This simulation builds on previous work by integrating a detailed analytical model of an MTI radar. This model has been tailored to the specific application of detection of slowly moving dismounted entities immersed in ground clutter. The model incorporates the effects of internal scatterer motion and antenna scanning modulation in order to provide a realistic representation of the detection problem in this environment. The angle information on the MTI target detection is then passed to a virtual 3D sight which cues a human operator to the target location. In addition, radar propagation effects and an experimental design in which the radar itself is used as a command link are explored.

  1. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

    Science.gov (United States)

    Hyun, Eugin; Jin, Young-Seok; Lee, Jong-Hun

    2016-01-01

    For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW) radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT) is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method. PMID:26805835

  2. A Pedestrian Detection Scheme Using a Coherent Phase Difference Method Based on 2D Range-Doppler FMCW Radar

    Directory of Open Access Journals (Sweden)

    Eugin Hyun

    2016-01-01

    Full Text Available For an automotive pedestrian detection radar system, fast-ramp based 2D range-Doppler Frequency Modulated Continuous Wave (FMCW radar is effective for distinguishing between moving targets and unwanted clutter. However, when a weak moving target such as a pedestrian exists together with strong clutter, the pedestrian may be masked by the side-lobe of the clutter even though they are notably separated in the Doppler dimension. To prevent this problem, one popular solution is the use of a windowing scheme with a weighting function. However, this method leads to a spread spectrum, so the pedestrian with weak signal power and slow Doppler may also be masked by the main-lobe of clutter. With a fast-ramp based FMCW radar, if the target is moving, the complex spectrum of the range- Fast Fourier Transform (FFT is changed with a constant phase difference over ramps. In contrast, the clutter exhibits constant phase irrespective of the ramps. Based on this fact, in this paper we propose a pedestrian detection for highly cluttered environments using a coherent phase difference method. By detecting the coherent phase difference from the complex spectrum of the range-FFT, we first extract the range profile of the moving pedestrians. Then, through the Doppler FFT, we obtain the 2D range-Doppler map for only the pedestrian. To test the proposed detection scheme, we have developed a real-time data logging system with a 24 GHz FMCW transceiver. In laboratory tests, we verified that the signal processing results from the proposed method were much better than those expected from the conventional 2D FFT-based detection method.

  3. Applying volumetric weather radar data for rainfall runoff modeling: The importance of error correction.

    Science.gov (United States)

    Hazenberg, P.; Leijnse, H.; Uijlenhoet, R.; Delobbe, L.; Weerts, A.; Reggiani, P.

    2009-04-01

    In the current study half a year of volumetric radar data for the period October 1, 2002 until March 31, 2003 is being analyzed which was sampled at 5 minutes intervals by C-band Doppler radar situated at an elevation of 600 m in the southern Ardennes region, Belgium. During this winter half year most of the rainfall has a stratiform character. Though radar and raingauge will never sample the same amount of rainfall due to differences in sampling strategies, for these stratiform situations differences between both measuring devices become even larger due to the occurrence of a bright band (the point where ice particles start to melt intensifying the radar reflectivity measurement). For these circumstances the radar overestimates the amount of precipitation and because in the Ardennes bright bands occur within 1000 meter from the surface, it's detrimental effects on the performance of the radar can already be observed at relatively close range (e.g. within 50 km). Although the radar is situated at one of the highest points in the region, very close to the radar clutter is a serious problem. As a result both nearby and farther away, using uncorrected radar results in serious errors when estimating the amount of precipitation. This study shows the effect of carefully correcting for these radar errors using volumetric radar data, taking into account the vertical reflectivity profile of the atmosphere, the effects of attenuation and trying to limit the amount of clutter. After applying these correction algorithms, the overall differences between radar and raingauge are much smaller which emphasizes the importance of carefully correcting radar rainfall measurements. The next step is to assess the effect of using uncorrected and corrected radar measurements on rainfall-runoff modeling. The 1597 km2 Ourthe catchment lies within 60 km of the radar. Using a lumped hydrological model serious improvement in simulating observed discharges is found when using corrected radar

  4. Modified-hybrid optical neural network filter for multiple object recognition within cluttered scenes

    Science.gov (United States)

    Kypraios, Ioannis; Young, Rupert C. D.; Chatwin, Chris R.

    2009-08-01

    Motivated by the non-linear interpolation and generalization abilities of the hybrid optical neural network filter between the reference and non-reference images of the true-class object we designed the modifiedhybrid optical neural network filter. We applied an optical mask to the hybrid optical neural network's filter input. The mask was built with the constant weight connections of a randomly chosen image included in the training set. The resulted design of the modified-hybrid optical neural network filter is optimized for performing best in cluttered scenes of the true-class object. Due to the shift invariance properties inherited by its correlator unit the filter can accommodate multiple objects of the same class to be detected within an input cluttered image. Additionally, the architecture of the neural network unit of the general hybrid optical neural network filter allows the recognition of multiple objects of different classes within the input cluttered image by modifying the output layer of the unit. We test the modified-hybrid optical neural network filter for multiple objects of the same and of different classes' recognition within cluttered input images and video sequences of cluttered scenes. The filter is shown to exhibit with a single pass over the input data simultaneously out-of-plane rotation, shift invariance and good clutter tolerance. It is able to successfully detect and classify correctly the true-class objects within background clutter for which there has been no previous training.

  5. Modern Approaches to the Computation of the Probability of Target Detection in Cluttered Environments

    Science.gov (United States)

    Meitzler, Thomas J.

    The field of computer vision interacts with fields such as psychology, vision research, machine vision, psychophysics, mathematics, physics, and computer science. The focus of this thesis is new algorithms and methods for the computation of the probability of detection (Pd) of a target in a cluttered scene. The scene can be either a natural visual scene such as one sees with the naked eye (visual), or, a scene displayed on a monitor with the help of infrared sensors. The relative clutter and the temperature difference between the target and background (DeltaT) are defined and then used to calculate a relative signal -to-clutter ratio (SCR) from which the Pd is calculated for a target in a cluttered scene. It is shown how this definition can include many previous definitions of clutter and (DeltaT). Next, fuzzy and neural -fuzzy techniques are used to calculate the Pd and it is shown how these methods can give results that have a good correlation with experiment. The experimental design for actually measuring the Pd of a target by observers is described. Finally, wavelets are applied to the calculation of clutter and it is shown how this new definition of clutter based on wavelets can be used to compute the Pd of a target.

  6. Advancement of High Resolution Radar Polarimetry in Target Verses Clutter Detection, Discrimination, Classification: A. Basic Theory and Modeling of Polarimetric Clutter Phenomenology.

    Science.gov (United States)

    1988-07-15

    Bio . data available upon request) Mr. Brian D. James, Ph.D. (candidate) Computer Data Processing Engineer Responsible for supervising UIC-.EECS/CL DEC...city and surrounding parks such as the Bell Tower, the marvellous Shaanxi Prcvincial Museum with its impressive forest of steles and stone carvings

  7. Estimation of past sea-level variations based on ground-penetrating radar mapping of beach-ridges - preliminary results from Feddet, Faxe Bay, eastern Denmark

    DEFF Research Database (Denmark)

    Hede, Mikkel Ulfeldt; Nielsen, Lars; Clemmensen, Lars B

    2011-01-01

    Estimates of past sea-level variations based on different methods and techniques have been presented in a range of studies, including interpretation of beach ridge characteristics. In Denmark, Holocene beach ridge plains have been formed during the last c. 7700 years, a period characterised by both...... isostatic uplift and changes in eustatic sea-level, and therefore represent an archive of past relative sea-level variations. Here, we present preliminary results from investigation of beach ridges from Feddet, a small peninsula located in Faxe Bay (Baltic Sea) in the eastern part of Denmark. Feddet has...... been chosen as a key-locality in this project, as it is located relatively close to the current 0-isobase of isostatic rebound. GPR reflection data have been acquired with shielded 250 MHz Sensors & software antennae along a number of profile lines across beach ridge and swale structures of the Feddet...

  8. COMPARING IMAGE-BASED METHODS FOR ASSESSING VISUAL CLUTTER IN GENERALIZED MAPS

    Directory of Open Access Journals (Sweden)

    G. Touya

    2015-08-01

    Full Text Available Map generalization abstracts and simplifies geographic information to derive maps at smaller scales. The automation of map generalization requires techniques to evaluate the global quality of a generalized map. The quality and legibility of a generalized map is related to the complexity of the map, or the amount of clutter in the map, i.e. the excessive amount of information and its disorganization. Computer vision research is highly interested in measuring clutter in images, and this paper proposes to compare some of the existing techniques from computer vision, applied to generalized maps evaluation. Four techniques from the literature are described and tested on a large set of maps, generalized at different scales: edge density, subband entropy, quad tree complexity, and segmentation clutter. The results are analyzed against several criteria related to generalized maps, the identification of cluttered areas, the preservation of the global amount of information, the handling of occlusions and overlaps, foreground vs background, and blank space reduction.

  9. Hardware in the loop radar environment simulation on wideband DRFM platforms

    CSIR Research Space (South Africa)

    Strydom, JJ

    2012-10-01

    Full Text Available @csir.co.za, dnaiker@csir.co.za, kolivier@csir.co.za Keywords: DRFM, ECM, Complex Targets, Clutter, HIL, radar environment, simulation. Abstract This paper describes the development and testing of a digital radio frequency memory (DRFM) kernel, as well... as follows: Section 2 describes the design of a high performance DRFM kernel. Section 3 describes the integration of this kernel into a radar environment simulator system. Sections 4, 5 and 6 then present the generation of realistic targets, ECM...

  10. RADAR PPI Scope Overlay

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — RADAR PPI Scope Overlays are used to position a RADAR image over a station at the correct resolution. The archive maintains several different RADAR resolution types,...

  11. Exploratory Data Analysis of Synthetic Aperture Radar (SAR Measurements to Distinguish the Sea Surface Expressions of Naturally-Occurring Oil Seeps from Human-Related Oil Spills in Campeche Bay (Gulf of Mexico

    Directory of Open Access Journals (Sweden)

    Gustavo de Araújo Carvalho

    2017-12-01

    Full Text Available An Exploratory Data Analysis (EDA aims to use Synthetic Aperture Radar (SAR measurements for discriminating between two oil slick types observed on the sea surface: naturally-occurring oil seeps versus human-related oil spills—the use of satellite sensors for this task is poorly documented in scientific literature. A long-term RADARSAT dataset (2008–2012 is exploited to investigate oil slicks in Campeche Bay (Gulf of Mexico. Simple Classification Algorithms to distinguish the oil slick type are designed based on standard multivariate data analysis techniques. Various attributes of geometry, shape, and dimension that describe the oil slick Size Information are combined with SAR-derived backscatter coefficients—sigma-(σo, beta-(βo, and gamma-(γo naught. The combination of several of these characteristics is capable of distinguishing the oil slick type with ~70% of overall accuracy, however, the sole and simple use of two specific oil slick’s Size Information (i.e., area and perimeter is equally capable of distinguishing seeps from spills. The data mining exercise of our EDA promotes a novel idea bridging petroleum pollution and remote sensing research, thus paving the way to further investigate the satellite synoptic view to express geophysical differences between seeped and spilled oil observed on the sea surface for systematic use.

  12. Effects of clutter on information processing deficits in individuals with hoarding disorder.

    Science.gov (United States)

    Raines, Amanda M; Timpano, Kiara R; Schmidt, Norman B

    2014-09-01

    Current cognitive behavioral models of hoarding view hoarding as a multifaceted problem stemming from various information processing deficits. However, there is also reason to suspect that the consequences of hoarding may in turn impact or modulate deficits in information processing. The current study sought to expand upon the existing literature by manipulating clutter to examine whether the presence of a cluttered environment affects information processing. Participants included 34 individuals with hoarding disorder. Participants were randomized into a clutter or non-clutter condition and asked to complete various neuropsychological tasks of memory and attention. Results revealed that hoarding severity was associated with difficulties in sustained attention. However, individuals in the clutter condition relative to the non-clutter condition did not experience greater deficits in information processing. Limitations include the cross-sectional design and small sample size. The current findings add considerably to a growing body of literature on the relationships between information processing deficits and hoarding behaviors. Research of this type is integral to understanding the etiology and maintenance of hoarding. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Managing Clutter in a High Pulse Rate Echolocation System

    Directory of Open Access Journals (Sweden)

    Jacob Isbell

    2018-03-01

    Full Text Available The use of echolocation for navigating in dense, cluttered environments is a challenge due to the need for rapid sampling of nearby objects in the face of delayed echoes from distant objects. In the wild, echolocating bats frequently encounter this situation when leaving the roost or while hunting. If long-delay echoes from a distant object are received after the next pulse is sent out, these “aliased” echoes appear as close-range phantom objects. Little is known about how bats cope with these situations. In this work, we demonstrate a novel strategy to manage aliasing in cases where a single target is actively being tracked at close range. This paper presents three reactive strategies for a high pulse-rate sonar system to combat aliased echoes: (1 changing the interpulse interval to move the aliased echoes away in time from the tracked target, (2 changing positions to create a geometry without aliasing, and (3 a phase-based, transmission beam-shaping strategy to illuminate the target and not the aliasing object.

  14. Numerical method for IR background and clutter simulation

    Science.gov (United States)

    Quaranta, Carlo; Daniele, Gina; Balzarotti, Giorgio

    1997-06-01

    The paper describes a fast and accurate algorithm of IR background noise and clutter generation for application in scene simulations. The process is based on the hypothesis that background might be modeled as a statistical process where amplitude of signal obeys to the Gaussian distribution rule and zones of the same scene meet a correlation function with exponential form. The algorithm allows to provide an accurate mathematical approximation of the model and also an excellent fidelity with reality, that appears from a comparison with images from IR sensors. The proposed method shows advantages with respect to methods based on the filtering of white noise in time or frequency domain as it requires a limited number of computation and, furthermore, it is more accurate than the quasi random processes. The background generation starts from a reticule of few points and by means of growing rules the process is extended to the whole scene of required dimension and resolution. The statistical property of the model are properly maintained in the simulation process. The paper gives specific attention to the mathematical aspects of the algorithm and provides a number of simulations and comparisons with real scenes.

  15. Shape-assisted body reorientation enhances trafficability through cluttered terrain

    Science.gov (United States)

    Li, Chen; Pullin, Andrew; Haldane, Duncan; Fearing, Ronald; Full, Robert

    2014-11-01

    Many birds and fishes have slender, streamlined bodies that reduce fluid dynamic drag and allow fast and efficient locomotion. Similarly, numerous terrestrial animals run through cluttered terrain where 3-D, multi-component obstacles like grass, bushes, trees, walls, doors, and pillars also resist motion, but it is unknown whether their body shape plays a major role. Here, we challenged discoid cockroaches that possess a rounded, thin, nearly ellipsoidal body to run through tall, narrowly spaced, grass-like beams. The animals primarily rolled their body to the side to maneuver through the obstacle gaps. Reduction of body roundness by artificial shells inhibited this side roll maneuver, resulting in a lower traversal probability and a longer traversal time (P exoskeleton shell to a legged robot of a nearly cuboidal body. The rounded shell enabled the robot to use passive side rolling to maneuver through beams. To explain the mechanism, we developed a simple physics model to construct an energy landscape of the body-terrain interaction, which allowed estimation of body forces and torques exerted by the beams. Our model revealed that, by passive interaction with the terrain, a rounded body (ellipsoid) rolled more easily than an angular body (cuboid) to access energy valleys between energy barriers caused by obstacles. Our study is the first to demonstrate that a terradynamically ``streamlined'' shape can reduce terrain resistance and enhance trafficability by assisting body reorientation.

  16. Research at the Stanford Center for Radar Astronomy

    Science.gov (United States)

    1972-01-01

    The research is reported in the applications of radar and radio techniques to the study of the solar system, and to space programs. Experiments reported include: bistatic-radar on Apollo missions, development of an unmanned geophysical observatory in the Antartic, Bragg scattering probes of sea states, characteristics of dense solar wind disturbances, and satellite communications for Alaska.

  17. Radar and Lidar Radar DEM

    Science.gov (United States)

    Liskovich, Diana; Simard, Marc

    2011-01-01

    Using radar and lidar data, the aim is to improve 3D rendering of terrain, including digital elevation models (DEM) and estimates of vegetation height and biomass in a variety of forest types and terrains. The 3D mapping of vegetation structure and the analysis are useful to determine the role of forest in climate change (carbon cycle), in providing habitat and as a provider of socio-economic services. This in turn will lead to potential for development of more effective land-use management. The first part of the project was to characterize the Shuttle Radar Topography Mission DEM error with respect to ICESat/GLAS point estimates of elevation. We investigated potential trends with latitude, canopy height, signal to noise ratio (SNR), number of LiDAR waveform peaks, and maximum peak width. Scatter plots were produced for each variable and were fitted with 1st and 2nd degree polynomials. Higher order trends were visually inspected through filtering with a mean and median filter. We also assessed trends in the DEM error variance. Finally, a map showing how DEM error was geographically distributed globally was created.

  18. Comparison of sea-level measurements between microwave radar and subsurface pressure gauge deployed at select locations along the coast of India

    Digital Repository Service at National Institute of Oceanography (India)

    Mehra, P.; Desai, R.G.P.; Joseph, A.; VijayKumar, K.; Agarvadekar, Y.; Luis, R.; Nadaf, L.

    for publication Mar. 13, 2013; published online May 3, 2013. 1 Introduction Information on sea level and its variability along coastal locations is essential for operational applications as well as scientific studies. Apart from safer navigational and coastal... provides several benefits, such as remote monitoring of individual stations, remote health monitoring to aid timely main- tenance, and periodic arrival of data streams from all stations at a single central server. The ICON data could be assimilated to real...

  19. Minimum redundancy MIMO radars

    OpenAIRE

    Chen, Chun-Yang; Vaidyanathan, P. P.

    2008-01-01

    The multiple-input multiple-output (MIMO) radar concept has drawn considerable attention recently. In the traditional single-input multiple-output (SIMO) radar system, the transmitter emits scaled versions of a single waveform. However, in the MIMO radar system, the transmitter transmits independent waveforms. It has been shown that the MIMO radar can be used to improve system performance. Most of the MIMO radar research so far has focused on the uniform array. However, i...

  20. A clutter removal method for the Doppler ultrasound signal based on a nonlinear diffusion equation

    International Nuclear Information System (INIS)

    Li Peng; Xin Pengcheng; Bian Zhengzhong; Yu Gang

    2008-01-01

    Strong clutter components produced by stationary and slow-moving tissue structures render the lower frequency part of the spectrogram useless and degrade the accuracy of clinical ultrasound indices. An adaptive method based on the nonlinear forward-and-backward diffusion equation (FAB-DE) is proposed to remove strong clutter components from the contaminated Doppler signal. The clutter signal is extracted first by the FAB-DE accurately, in which the nonlinear diffusion coefficient function of the FAB-DE locally adjusts according to signal features and the diffusion adaptively switches between forward and backward mode. The present method has been validated by simulated and realistic pulse wave Doppler signals, and compared with the conventional high pass filter and the matching pursuit method. The simulation results, including spectrogram, mean velocity error, standard deviation of mean velocity and signal-to-clutter ratio of a decontaminated signal, demonstrate that the present FAB-DE method can remove clutter sufficiently and retain more low blood components simultaneously as compared with the other two methods. Results of the realistic Doppler blood signal, including spectrogram and low-frequency part of the spectrum, support the conclusion drawn from simulation cases

  1. Signs of depth-luminance covariance in 3-D cluttered scenes.

    Science.gov (United States)

    Scaccia, Milena; Langer, Michael S

    2018-03-01

    In three-dimensional (3-D) cluttered scenes such as foliage, deeper surfaces often are more shadowed and hence darker, and so depth and luminance often have negative covariance. We examined whether the sign of depth-luminance covariance plays a role in depth perception in 3-D clutter. We compared scenes rendered with negative and positive depth-luminance covariance where positive covariance means that deeper surfaces are brighter and negative covariance means deeper surfaces are darker. For each scene, the sign of the depth-luminance covariance was given by occlusion cues. We tested whether subjects could use this sign information to judge the depth order of two target surfaces embedded in 3-D clutter. The clutter consisted of distractor surfaces that were randomly distributed in a 3-D volume. We tested three independent variables: the sign of the depth-luminance covariance, the colors of the targets and distractors, and the background luminance. An analysis of variance showed two main effects: Subjects performed better when the deeper surfaces were darker and when the color of the target surfaces was the same as the color of the distractors. There was also a strong interaction: Subjects performed better under a negative depth-luminance covariance condition when targets and distractors had different colors than when they had the same color. Our results are consistent with a "dark means deep" rule, but the use of this rule depends on the similarity between the color of the targets and color of the 3-D clutter.

  2. Performance test and verification of an off-the-shelf automated avian radar tracking system.

    Science.gov (United States)

    May, Roel; Steinheim, Yngve; Kvaløy, Pål; Vang, Roald; Hanssen, Frank

    2017-08-01

    Microwave radar is an important tool for observation of birds in flight and represents a tremendous increase in observation capability in terms of amount of surveillance space that can be covered at relatively low cost. Based on off-the-shelf radar hardware, automated radar tracking systems have been developed for monitoring avian movements. However, radar used as an observation instrument in biological research has its limitations that are important to be aware of when analyzing recorded radar data. This article describes a method for exploring the detection capabilities of a dedicated short-range avian radar system used inside the operational Smøla wind-power plant. The purpose of the testing described was to find the maximum detection range for various sized birds, while controlling for the effects of flight tortuosity, flight orientation relative to the radar and ground clutter. The method was to use a dedicated test target in form of a remotely controlled unmanned aerial vehicle (UAV) with calibrated radar cross section (RCS), which enabled the design of virtually any test flight pattern within the area of interest. The UAV had a detection probability of 0.5 within a range of 2,340 m from the radar. The detection performance obtained by the RCS-calibrated test target (-11 dBm 2 , 0.08 m 2 RCS) was then extrapolated to find the corresponding performance of differently sized birds. Detection range depends on system sensitivity, the environment within which the radar is placed and the spatial distribution of birds. The avian radar under study enables continuous monitoring of bird activity within a maximum range up to 2 km dependent on the size of the birds in question. While small bird species may be detected up to 0.5-1 km, larger species may be detected up to 1.5-2 km distance from the radar.

  3. Facial expression, size, and clutter: Inferences from movie structure to emotion judgments and back.

    Science.gov (United States)

    Cutting, James E; Armstrong, Kacie L

    2016-04-01

    The perception of facial expressions and objects at a distance are entrenched psychological research venues, but their intersection is not. We were motivated to study them together because of their joint importance in the physical composition of popular movies-shots that show a larger image of a face typically have shorter durations than those in which the face is smaller. For static images, we explore the time it takes viewers to categorize the valence of different facial expressions as a function of their visual size. In two studies, we find that smaller faces take longer to categorize than those that are larger, and this pattern interacts with local background clutter. More clutter creates crowding and impedes the interpretation of expressions for more distant faces but not proximal ones. Filmmakers at least tacitly know this. In two other studies, we show that contemporary movies lengthen shots that show smaller faces, and even more so with increased clutter.

  4. Adaptive radar resource management

    CERN Document Server

    Moo, Peter

    2015-01-01

    Radar Resource Management (RRM) is vital for optimizing the performance of modern phased array radars, which are the primary sensor for aircraft, ships, and land platforms. Adaptive Radar Resource Management gives an introduction to radar resource management (RRM), presenting a clear overview of different approaches and techniques, making it very suitable for radar practitioners and researchers in industry and universities. Coverage includes: RRM's role in optimizing the performance of modern phased array radars The advantages of adaptivity in implementing RRMThe role that modelling and

  5. Radar and ARPA manual

    CERN Document Server

    Bole, A G

    2013-01-01

    Radar and ARPA Manual focuses on the theoretical and practical aspects of electronic navigation. The manual first discusses basic radar principles, including principles of range and bearing measurements and picture orientation and presentation. The text then looks at the operational principles of radar systems. Function of units; aerial, receiver, and display principles; transmitter principles; and sitting of units on board ships are discussed. The book also describes target detection, Automatic Radar Plotting Aids (ARPA), and operational controls of radar systems, and then discusses radar plo

  6. Analysis of measured L-band airborne land clutter from the Western Cape region of South Africa

    CSIR Research Space (South Africa)

    De Witt, JJ

    2014-10-01

    Full Text Available -band Airborne Land Clutter from the Western Cape region of South Africa J.J. de Witt and J.J. Strydom Abstract: This paper presents backscatter analysis of L-band land clutter data, measured from an airborne platform, over various terrain types...

  7. Linking sardine recruitment in coastal areas to ocean currents using surface drifters and HF radar. A case study in the Gulf of Manfredonia, Adriatic Sea

    DEFF Research Database (Denmark)

    Sciascia, Roberta; Berta, Maristella; Carlson, Daniel Frazier

    2017-01-01

    Understanding the role of ocean currents in the recruitment of commercially and ecologically important fish is an important step towards developing sustainable resource management guidelines. To this end, we attempt to elucidate the role of surface ocean transport in supplying recruits of sardine...... (Sardinus pilchardus) to the Gulf of Manfredonia, a known recruitment area in the Adriatic Sea. Sardine early life history stages (ELHS) were collected during two cruises to provide observational estimates of age-size relationship and of their passive pelagic larval duration (PPLD). We combine these PPLDs...... in the Gulf is characterized by repeated pulses from remote SAs. This is the first attempt to describe the processes related to Lagrangian connection to, and retention in, the Gulf of Manfredonia that will be complemented in the future using validated numerical ocean models and biophysical models....

  8. Analysis of Radar Doppler Signature from Human Data

    Directory of Open Access Journals (Sweden)

    M. ANDRIĆ

    2014-04-01

    Full Text Available This paper presents the results of time (autocorrelation and time-frequency (spectrogram analyses of radar signals returned from the moving human targets. When a radar signal falls on the human target which is moving toward or away from the radar, the signals reflected from different parts of his body produce a Doppler shift that is proportional to the velocity of those parts. Moving parts of the body causes the characteristic Doppler signature. The main contribution comes from the torso which causes the central Doppler frequency of target. The motion of arms and legs induces modulation on the returned radar signal and generates sidebands around the central Doppler frequency, referred to as micro-Doppler signatures. Through analyses on experimental data it was demonstrated that the human motion signature extraction is better using spectrogram. While the central Doppler frequency can be determined using the autocorrelation and the spectrogram, the extraction of the fundamental cadence frequency using the autocorrelation is unreliable when the target is in the clutter presence. It was shown that the fundamental cadence frequency increases with increasing dynamic movement of people and simultaneously the possibility of its extraction is proportional to the degree of synchronization movements of persons in the group.

  9. Radar Weather Observation

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Radar Weather Observation is a set of archived historical manuscripts stored on microfiche. The primary source of these radar weather observations manuscript records...

  10. ISTEF Laser Radar Program

    National Research Council Canada - National Science Library

    Stryjewski, John

    1998-01-01

    The BMDO Innovative Science and Technology Experimentation Facility (BMDO/ISTEF) laser radar program is engaged in an ongoing program to develop and demonstrate advanced laser radar concepts for Ballistic Missile Defense (BMD...

  11. Weather Radar Impact Zones

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — These data represent an inventory of the national impacts of wind turbine interference with NEXRAD radar stations. This inventory was developed by the NOAA Radar...

  12. Detection and identification of human targets in radar data

    Science.gov (United States)

    Gürbüz, Sevgi Z.; Melvin, William L.; Williams, Douglas B.

    2007-04-01

    Radar offers unique advantages over other sensors, such as visual or seismic sensors, for human target detection. Many situations, especially military applications, prevent the placement of video cameras or implantment seismic sensors in the area being observed, because of security or other threats. However, radar can operate far away from potential targets, and functions during daytime as well as nighttime, in virtually all weather conditions. In this paper, we examine the problem of human target detection and identification using single-channel, airborne, synthetic aperture radar (SAR). Human targets are differentiated from other detected slow-moving targets by analyzing the spectrogram of each potential target. Human spectrograms are unique, and can be used not just to identify targets as human, but also to determine features about the human target being observed, such as size, gender, action, and speed. A 12-point human model, together with kinematic equations of motion for each body part, is used to calculate the expected target return and spectrogram. A MATLAB simulation environment is developed including ground clutter, human and non-human targets for the testing of spectrogram-based detection and identification algorithms. Simulations show that spectrograms have some ability to detect and identify human targets in low noise. An example gender discrimination system correctly detected 83.97% of males and 91.11% of females. The problems and limitations of spectrogram-based methods in high clutter environments are discussed. The SNR loss inherent to spectrogram-based methods is quantified. An alternate detection and identification method that will be used as a basis for future work is proposed.

  13. Novel radar techniques and applications

    CERN Document Server

    Klemm, Richard; Lombardo, Pierfrancesco; Nickel, Ulrich

    2017-01-01

    Novel Radar Techniques and Applications presents the state-of-the-art in advanced radar, with emphasis on ongoing novel research and development and contributions from an international team of leading radar experts. This volume covers: Real aperture array radar; Imaging radar and Passive and multistatic radar.

  14. Principles of modern radar systems

    CERN Document Server

    Carpentier, Michel H

    1988-01-01

    Introduction to random functions ; signal and noise : the ideal receiver ; performance of radar systems equipped with ideal receivers ; analysis of the operating principles of some types of radar ; behavior of real targets, fluctuation of targets ; angle measurement using radar ; data processing of radar information, radar coverage ; applications to electronic scanning antennas to radar ; introduction to Hilbert spaces.

  15. Frequency Diverse Array Radar Signal Processing via Space-Range-Doppler Focus (SRDF Method

    Directory of Open Access Journals (Sweden)

    Chen Xiaolong

    2018-04-01

    Full Text Available To meet the urgent demand of low-observable moving target detection in complex environments, a novel method of Frequency Diverse Array (FDA radar signal processing method based on Space-Rang-Doppler Focusing (SRDF is proposed in this paper. The current development status of the FDA radar, the design of the array structure, beamforming, and joint estimation of distance and angle are systematically reviewed. The extra degrees of freedom provided by FDA radar are fully utilizsed, which include the Degrees Of Freedom (DOFs of the transmitted waveform, the location of array elements, correlation of beam azimuth and distance, and the long dwell time, which are also the DOFs in joint spatial (angle, distance, and frequency (Doppler dimensions. Simulation results show that the proposed method has the potential of improving target detection and parameter estimation for weak moving targets in complex environments and has broad application prospects in clutter and interference suppression, moving target refinement, etc..

  16. A new low-cost 10 ns pulsed K(a)-band radar.

    Science.gov (United States)

    Eskelinen, Pekka; Ylinen, Juhana

    2011-07-01

    Two Gunn oscillators, conventional intermediate frequency building blocks, and a modified GaAs diode detector are combined to form a portable monostatic 10 ns instrumentation radar for outdoor K(a)-band radar cross section measurements. At 37.8 GHz the radar gives +20 dBm output power and its tangential sensitivity is -76 dBm. Processing bandwidth is 125 MHz, which also allows for some frequency drift in the Gunn devices. Intra-pulse frequency chirp is less than 15 MHz. All functions are steered by a microcontroller. First measurements convince that the construction has a reasonable ability to reduce close-to-ground surface clutter and gives an effective way of resolving target detail. This is beneficial especially when amplitude fluctuations disturb measurements with longer pulses. The new unit operates on 12 V dc, draws a current of less than 3 A, and weighs 5 kg.

  17. Software Radar Technology

    Directory of Open Access Journals (Sweden)

    Tang Jun

    2015-08-01

    Full Text Available In this paper, the definition and the key features of Software Radar, which is a new concept, are proposed and discussed. We consider the development of modern radar system technology to be divided into three stages: Digital Radar, Software radar and Intelligent Radar, and the second stage is just commencing now. A Software Radar system should be a combination of various modern digital modular components conformed to certain software and hardware standards. Moreover, a software radar system with an open system architecture supporting to decouple application software and low level hardware would be easy to adopt "user requirements-oriented" developing methodology instead of traditional "specific function-oriented" developing methodology. Compared with traditional Digital Radar, Software Radar system can be easily reconfigured and scaled up or down to adapt to the changes of requirements and technologies. A demonstration Software Radar signal processing system, RadarLab 2.0, which has been developed by Tsinghua University, is introduced in this paper and the suggestions for the future development of Software Radar in China are also given in the conclusion.

  18. Breaking through the clutter : Benefits of advertisement originality and familiarity for brand attention and memory

    NARCIS (Netherlands)

    Pieters, R; Warlop, L; Wedel, M

    Rising levels of advertising competition have made it increasingly difficult to attract and hold consumers' attention and to establish strong memory traces for the advertised brand. A common communication strategy to break through this competitive clutter is to increase ad originality However, ad

  19. A clinical delineation of tachyphemia (cluttering) | Op't Hof | South ...

    African Journals Online (AJOL)

    Cluttering constitutes one of the most important disorders of speech, language and communication in general. The majority of c1utterers are themselves unaware of the disorder. The problems of definition, symptomatology, aetiology and relationship to stuttering and hereditary aspects, are discussed. A preliminary case ...

  20. Improved covariance matrix estimation in spectrally inhomogeneous sea clutter with application to adaptive small boat detection.

    CSIR Research Space (South Africa)

    Herselman, PL

    2008-09-01

    Full Text Available and that is necessary to set the threshold χt as a function of the steering vector Doppler fd. Improvements to the estimation technique are suggested and evaluated where a more localised M is estimated using either frequency agility or the immediate time history... of frequency, calculated as NIM2(fd) = E{z(fd)2}/E2{z(fd)} , (3) where z(fd) is the power spectral density at fd. This is often used to quantify the Rayleigh-likeness of the envelope 0 5 10 15 −500 −250 0 250 500 Doppler frequency [Hz ] NIM2Time [s...

  1. The Solar System: a cluttered laboratory for gravity research

    International Nuclear Information System (INIS)

    Reasenberg, R.D.

    1982-01-01

    In the second half century following the birth of Einstein, there was rapid technological change in the approach taken for testing theories of gravitation. Visual sightings of planets have been superseded by radar observations and radio observations which now provide interplanetary distance measurements with an uncertainty equivalent to a few meters. Using delay data made possible by the Viking Mission to Mars, Shapiro's time delay test has been performed, yielding (1+γ)/2 = 1+-10 -3 . However, even if an optimistic assumption is made about further improvements in the analysis of these data, it is found that the Viking Relativity Experiment cannot be used to discriminate among currently viable theories. A second-order test is required. POINTS is a proposed astrometric satellite that could be used to perform a second-order light deflection experiment. This Earth-orbiting instrument would use two optical interferometers to measure the angular separations between pairs of stars. Deployment and use of this satellite during the 1990's is possible. (Auth.)

  2. Application of in situ observations, high frequency radars, and ocean color, to study suspended matter, particulate carbon, and dissolved organic carbon fluxes in coastal waters of the Barents Sea - the NORDFLUX project

    Science.gov (United States)

    Stramska, Malgorzata; Yngve Børsheim, Knut; Białogrodzka, Jagoda; Cieszyńska, Agata; Ficek, Dariusz; Wereszka, Marzena

    2016-04-01

    There is still a limited knowledge about suspended and dissolved matter fluxes transported from coastal regions into the open sea regions in the Arctic. The land/sea interface is environmentally important and sensitive to climate change. Important biogeochemical material entering the oceans (including carbon) passes through this interface, but too little is known about the efficiency of this transport. Our goal in the NORDFLUX program is to improve quantitative understanding of the environmental feedbacks involved in these processes through an interdisciplinary study with innovative in situ observations. Completed work includes two in situ experiments in the Norwegian fiord (Porsangerfjorden) in the summers of 2014 and 2015. Experiments used research boat for collection of water samples and in situ bio-optical data, an autonomous glider, mooring with T S sensors, and a high frequency radar system. We have used these data to derive spatial maps of water temperature, salinity, surface currents, chlorophyll fluorescence, dissolved organic matter (DOM) fluorescence, and inherent optical properties (IOPs) of the water. The interpretation of these data in terms of suspended matter concentration and composition is possible by in situ 'calibrations' using water samples from discrete hydrographic stations. Total suspended matter (TSM), particulate carbon (POC and PIC), and dissolved organic carbon (DOC) concentrations together with measured water currents will allow us to estimate reservoirs and fluxes. Concentrations and fluxes will be related to physical conditions and meteorological data. An important aspect of this project is the work on regional ocean color algorithms. Global ocean color (OC) algorithms currently used by NASA do not perform sufficiently well in coastal Case 2 waters. Our data sets will allow us to derive such local algorithms. We will then use these algorithms for interpretation of OC data in terms of TSM concentrations and composition and DOC. After

  3. Understanding radar systems

    CERN Document Server

    Kingsley, Simon

    1999-01-01

    What is radar? What systems are currently in use? How do they work? This book provides engineers and scientists with answers to these critical questions, focusing on actual radar systems in use today. It is a perfect resource for those just entering the field, or as a quick refresher for experienced practitioners. The book leads readers through the specialized language and calculations that comprise the complex world of radar engineering as seen in dozens of state-of-the-art radar systems. An easy to read, wide ranging guide to the world of modern radar systems.

  4. Pulse Doppler radar

    CERN Document Server

    Alabaster, Clive

    2012-01-01

    This book is a practitioner's guide to all aspects of pulse Doppler radar. It concentrates on airborne military radar systems since they are the most used, most complex, and most interesting of the pulse Doppler radars; however, ground-based and non-military systems are also included. It covers the fundamental science, signal processing, hardware issues, systems design and case studies of typical systems. It will be a useful resource for engineers of all types (hardware, software and systems), academics, post-graduate students, scientists in radar and radar electronic warfare sectors and milit

  5. New Cloud and Precipitation Research Avenues Enabled by low-cost Phased-array Radar Technology

    Science.gov (United States)

    Kollias, P.; Oue, M.; Fridlind, A. M.; Matsui, T.; McLaughlin, D. J.

    2017-12-01

    For over half a century, radars operating in a wide range of frequencies have been the primary source of observational insights of clouds and precipitation microphysics and dynamics and contributed to numerous significant advancements in the field of cloud and precipitation physics. The development of multi-wavelength and polarization diversity techniques has further strengthened the quality of microphysical and dynamical retrievals from radars and has assisted in overcoming some of the limitations imposed by the physics of scattering. Atmospheric radars have historically employed a mechanically-scanning dish antenna and their ability to point to, survey, and revisit specific points or regions in the atmosphere is limited by mechanical inertia. Electronically scanned, or phased-array, radars capable of high-speed, inertialess beam steering, have been available for several decades, but the cost of this technology has limited its use to military applications. During the last 10 years, lower power and lower-cost versions of electronically scanning radars have been developed, and this presents an attractive and affordable new tool for the atmospheric sciences. The operational and research communities are currently exploring phased array advantages in signal processing (i.e. beam multiplexing, improved clutter rejection, cross beam wind estimation, adaptive sensing) and science applications (i.e. tornadic storm morphology studies). Here, we will present some areas of atmospheric research where inertia-less radars with ability to provide rapid volume imaging offers the potential to advance cloud and precipitation research. We will discuss the added value of single phased-array radars as well as networks of these radars for several problems including: multi-Doppler wind retrieval techniques, cloud lifetime studies and aerosol-convection interactions. The performance of current (dish) and future (e-scan) radar systems for these atmospheric studies will be evaluated using

  6. A quantitative analysis of the impact of wind turbines on operational Doppler weather radar data

    Science.gov (United States)

    Norin, L.

    2015-02-01

    In many countries wind turbines are rapidly growing in numbers as the demand for energy from renewable sources increases. The continued deployment of wind turbines can, however, be problematic for many radar systems, which are easily disturbed by turbines located in the radar line of sight. Wind turbines situated in the vicinity of Doppler weather radars can lead to erroneous precipitation estimates as well as to inaccurate wind and turbulence measurements. This paper presents a quantitative analysis of the impact of a wind farm, located in southeastern Sweden, on measurements from a nearby Doppler weather radar. The analysis is based on 6 years of operational radar data. In order to evaluate the impact of the wind farm, average values of all three spectral moments (the radar reflectivity factor, absolute radial velocity, and spectrum width) of the nearby Doppler weather radar were calculated, using data before and after the construction of the wind farm. It is shown that all spectral moments, from a large area at and downrange from the wind farm, were impacted by the wind turbines. It was also found that data from radar cells far above the wind farm (near 3 km altitude) were affected by the wind farm. It is shown that this in part can be explained by detection by the radar sidelobes and by scattering off increased levels of dust and turbulence. In a detailed analysis, using data from a single radar cell, frequency distributions of all spectral moments were used to study the competition between the weather signal and wind turbine clutter. It is shown that, when weather echoes give rise to higher reflectivity values than those of the wind farm, the negative impact of the wind turbines is greatly reduced for all spectral moments.

  7. Meteo-marine parameters for highly variable environment in coastal regions from satellite radar images

    Science.gov (United States)

    Pleskachevsky, A. L.; Rosenthal, W.; Lehner, S.

    2016-09-01

    The German Bight of the North Sea is the area with highly variable sea state conditions, intensive ship traffic and with a high density of offshore installations, e.g. wind farms in use and under construction. Ship navigation and the docking on offshore constructions is impeded by significant wave heights HS > 1.3 m. For these reasons, improvements are required in recognition and forecasting of sea state HS in the range 0-3 m. Thus, this necessitates the development of new methods to determine the distribution of meteo-marine parameters from remote sensing data with an accuracy of decimetres for HS. The operationalization of these methods then allows the robust automatic processing in near real time (NRT) to support forecast agencies by providing validations for model results. A new empirical algorithm XWAVE_C (C = coastal) for estimation of significant wave height from X-band satellite-borne Synthetic Aperture Radar (SAR) data has been developed, adopted for coastal applications using TerraSAR-X (TS-X) and Tandem-X (TD-X) satellites in the German Bight and implemented into the Sea Sate Processor (SSP) for fully automatic processing for NRT services. The algorithm is based on the spectral analysis of subscenes and the model function uses integrated image spectra parameters as well as local wind information from the analyzed subscene. The algorithm is able to recognize and remove the influence of non-sea state produced signals in the Wadden Sea areas such as dry sandbars as well as nonlinear SAR image distortions produced by e.g. short wind waves and breaking waves. Also parameters of very short waves, which are not visible in SAR images and produce only unsystematic clutter, can be accurately estimated. The SSP includes XWAVE_C, a pre-filtering procedure for removing artefacts such as ships, seamarks, buoys, offshore constructions and slicks, and an additional procedure performing a check of results based on the statistics of the whole scene. The SSP allows an

  8. MARSnet: Mission-aware Autonomous Radar Sensor Network for Future Combat Systems 12/8/06 to 12/31/09

    Science.gov (United States)

    2010-01-01

    Channels are frequency dependent. It has been observed that the intervening materials, such as foliage and soil , have dielectric properties that are...equipment in a strong clutter background, such as foliage, soil cover or building has been a long-standing subject of intensive study. It is believed...foliage enviroment , and observed that the path-loss exponent is very high because it has rich scattering. Index Terms : Channel modeling, radar, UWB channel

  9. Detection of Multiple Stationary Humans Using UWB MIMO Radar

    Directory of Open Access Journals (Sweden)

    Fulai Liang

    2016-11-01

    Full Text Available Remarkable progress has been achieved in the detection of single stationary human. However, restricted by the mutual interference of multiple humans (e.g., strong sidelobes of the torsos and the shadow effect, detection and localization of the multiple stationary humans remains a huge challenge. In this paper, ultra-wideband (UWB multiple-input and multiple-output (MIMO radar is exploited to improve the detection performance of multiple stationary humans for its multiple sight angles and high-resolution two-dimensional imaging capacity. A signal model of the vital sign considering both bi-static angles and attitude angle of the human body is firstly developed, and then a novel detection method is proposed to detect and localize multiple stationary humans. In this method, preprocessing is firstly implemented to improve the signal-to-noise ratio (SNR of the vital signs, and then a vital-sign-enhanced imaging algorithm is presented to suppress the environmental clutters and mutual affection of multiple humans. Finally, an automatic detection algorithm including constant false alarm rate (CFAR, morphological filtering and clustering is implemented to improve the detection performance of weak human targets affected by heavy clutters and shadow effect. The simulation and experimental results show that the proposed method can get a high-quality image of multiple humans and we can use it to discriminate and localize multiple adjacent human targets behind brick walls.

  10. Comparison between HF radar current data and moored ADCP currentmeter

    International Nuclear Information System (INIS)

    Cosoli, S.

    2005-01-01

    A preliminary assessment of accuracy of a two-sites shore-based HF Radar network along the Venice Lagoon littoral was attempted by means of comparison with a 57.5 day-long ADCP current time series for the period September-October 2002. Results showed that radar measurements were accurate ( O . The main differences between the HF radar and surface ADCP currents can be explained in terms of random errors affecting the measurement technique and the daily sea breeze forcing, since low-pass filtering of current time series significantly improved the correlation and decreased the RMS of the differences between the two measured data set. Comparison of the semidiurnal (M2, S2) tidal band suggested good agreement between tidal ellipse amplitudes. Wind forcing on a daily time-scale (sea-breeze) was associated with larger differences between radar and ADCP currents at a diurnal band due to the presence of a vertical shear in the surface layer

  11. Simulación de un sistema radar MTI no coherente

    OpenAIRE

    Quesada Pereira, Fernando Daniel; Gómez Tornero, José Luis; Cañete Rebenaque, David; Pascual García, Juan; Álvarez Melcón , Alejandro

    2004-01-01

    En este artículo presentamos un algoritmo de cálculo simple que sirve para simular el funcionamiento de un Radar para Detección de Blancos Móviles (MTI), basado en detección no coherente. El sistema se basa en el almacenamiento en memoria del video crudo recibido en varios barridos en la antena. Posteriormente se aplica un cancelador a la señal almacenada entre los diferentes barridos. El procedimiento desarrollado sirve para generar de forma artificial el clutter fijo de montañas, a...

  12. Registration-Based Range-Dependence Compensation for Bistatic STAP Radars

    Directory of Open Access Journals (Sweden)

    Lapierre Fabian D

    2005-01-01

    Full Text Available We address the problem of detecting slow-moving targets using space-time adaptive processing (STAP radar. Determining the optimum weights at each range requires data snapshots at neighboring ranges. However, in virtually all configurations, snapshot statistics are range dependent, meaning that snapshots are nonstationary with respect to range. This results in poor performance. In this paper, we propose a new compensation method based on registration of clutter ridges and designed to work on a single realization of the stochastic snapshot at each range. The method has been successfully tested on simulated, stochastic snapshots. An evaluation of performance is presented.

  13. Detection and localization of multiple short range targets using FMCW radar signal

    KAUST Repository

    Jardak, Seifallah

    2016-07-26

    In this paper, a 24 GHz frequency-modulated continuous wave radar is used to detect and localize both stationary and moving targets. Depending on the application, the implemented software offers different modes of operation. For example, it can simply output raw data samples for advanced offline processing or directly carry out a two dimensional fast Fourier transform to estimate the location and velocity of multiple targets. To suppress clutter and detect only moving targets, two methods based on the background reduction and the slow time processing techniques are implemented. A trade-off between the two methods is presented based on their performance and the required processing time. © 2016 IEEE.

  14. Improvement of Automated Identification of the Heart Wall in Echocardiography by Suppressing Clutter Component

    Science.gov (United States)

    Takahashi, Hiroki; Hasegawa, Hideyuki; Kanai, Hiroshi

    2013-07-01

    For the facilitation of analysis and elimination of the operator dependence in estimating the myocardial function in echocardiography, we have previously developed a method for automated identification of the heart wall. However, there are misclassified regions because the magnitude-squared coherence (MSC) function of echo signals, which is one of the features in the previous method, is sensitively affected by the clutter components such as multiple reflection and off-axis echo from external tissue or the nearby myocardium. The objective of the present study is to improve the performance of automated identification of the heart wall. For this purpose, we proposed a method to suppress the effect of the clutter components on the MSC of echo signals by applying an adaptive moving target indicator (MTI) filter to echo signals. In vivo experimental results showed that the misclassified regions were significantly reduced using our proposed method in the longitudinal axis view of the heart.

  15. An Improved Sequential Initiation Method for Multitarget Track in Clutter with Large Noise Measurement

    Directory of Open Access Journals (Sweden)

    Daxiong Ji

    2014-01-01

    Full Text Available This paper proposes an improved sequential method for underwater multiple objects tracks initiation in clutter, estimating the initial position for the trajectory. The underwater environment is complex and changeable, and the sonar data are not very ideal. When the detection distance is far, the error of measured data is also great. Besides that, the clutter has a grave effect on the tracks initiation. So it is hard to initialize a track and estimate the initial position. The new tracks initiation is that when at least six of ten points meet the requirements, then we determine that there is a new track and the initial states of the parameters are estimated by the linear least square method. Compared to the conventional tracks initiation methods, our method not only considers the kinematics information of targets, but also regards the error of the sonar sensors as an important element. Computer simulations confirm that the performance of our method is very nice.

  16. Phased-array radar design application of radar fundamentals

    CERN Document Server

    Jeffrey, Thomas

    2009-01-01

    Phased-Array Radar Design is a text-reference designed for electrical engineering graduate students in colleges and universities as well as for corporate in-house training programs for radar design engineers, especially systems engineers and analysts who would like to gain hands-on, practical knowledge and skills in radar design fundamentals, advanced radar concepts, trade-offs for radar design and radar performance analysis.

  17. Doppler radar physiological sensing

    CERN Document Server

    Lubecke, Victor M; Droitcour, Amy D; Park, Byung-Kwon; Singh, Aditya

    2016-01-01

    Presents a comprehensive description of the theory and practical implementation of Doppler radar-based physiological monitoring. This book includes an overview of current physiological monitoring techniques and explains the fundamental technology used in remote non-contact monitoring methods. Basic radio wave propagation and radar principles are introduced along with the fundamentals of physiological motion and measurement. Specific design and implementation considerations for physiological monitoring radar systems are then discussed in detail. The authors address current research and commercial development of Doppler radar based physiological monitoring for healthcare and other applications.

  18. PTBS segmentation scheme for synthetic aperture radar

    Science.gov (United States)

    Friedland, Noah S.; Rothwell, Brian J.

    1995-07-01

    The Image Understanding Group at Martin Marietta Technologies in Denver, Colorado has developed a model-based synthetic aperture radar (SAR) automatic target recognition (ATR) system using an integrated resource architecture (IRA). IRA, an adaptive Markov random field (MRF) environment, utilizes information from image, model, and neighborhood resources to create a discrete, 2D feature-based world description (FBWD). The IRA FBWD features are peak, target, background and shadow (PTBS). These features have been shown to be very useful for target discrimination. The FBWD is used to accrue evidence over a model hypothesis set. This paper presents the PTBS segmentation process utilizing two IRA resources. The image resource (IR) provides generic (the physics of image formation) and specific (the given image input) information. The neighborhood resource (NR) provides domain knowledge of localized FBWD site behaviors. A simulated annealing optimization algorithm is used to construct a `most likely' PTBS state. Results on simulated imagery illustrate the power of this technique to correctly segment PTBS features, even when vehicle signatures are immersed in heavy background clutter. These segmentations also suppress sidelobe effects and delineate shadows.

  19. Drama techniques as part of cluttering therapy according to the verbotonal method

    OpenAIRE

    Hercigonja Salamoni, Darija; Rendulić, Ana

    2017-01-01

    Cluttering is a syndrome characterised by a wide range of symptoms. It always contains one or more key elements such as abnormally fast speech rate, greater than expected number of disfluencies, reduced intelligibility due to over-coarticulation and indistinct articulation, inappropriate brakes in speech pattern, monotone speech, disturbance in language planning, etc. Drama activities and storytelling share a number of features that allow spontaneous use during therapy process and detachment ...

  20. Radar Plan Position Indicator Scope

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — Radar Plan Position Indicator Scope is the collection of weather radar imagery for the period prior to the beginning of the Next Generation Radar (NEXRAD) system...

  1. Influence of visual clutter on the effect of navigated safety inspection: a case study on elevator installation.

    Science.gov (United States)

    Liao, Pin-Chao; Sun, Xinlu; Liu, Mei; Shih, Yu-Nien

    2018-01-11

    Navigated safety inspection based on task-specific checklists can increase the hazard detection rate, theoretically with interference from scene complexity. Visual clutter, a proxy of scene complexity, can theoretically impair visual search performance, but its impact on the effect of safety inspection performance remains to be explored for the optimization of navigated inspection. This research aims to explore whether the relationship between working memory and hazard detection rate is moderated by visual clutter. Based on a perceptive model of hazard detection, we: (a) developed a mathematical influence model for construction hazard detection; (b) designed an experiment to observe the performance of hazard detection rate with adjusted working memory under different levels of visual clutter, while using an eye-tracking device to observe participants' visual search processes; (c) utilized logistic regression to analyze the developed model under various visual clutter. The effect of a strengthened working memory on the detection rate through increased search efficiency is more apparent in high visual clutter. This study confirms the role of visual clutter in construction-navigated inspections, thus serving as a foundation for the optimization of inspection planning.

  2. Age differences in search of web pages: the effects of link size, link number, and clutter.

    Science.gov (United States)

    Grahame, Michael; Laberge, Jason; Scialfa, Charles T

    2004-01-01

    Reaction time, eye movements, and errors were measured during visual search of Web pages to determine age-related differences in performance as a function of link size, link number, link location, and clutter. Participants (15 young adults, M = 23 years; 14 older adults, M = 57 years) searched Web pages for target links that varied from trial to trial. During one half of the trials, links were enlarged from 10-point to 12-point font. Target location was distributed among the left, center, and bottom portions of the screen. Clutter was manipulated according to the percentage of used space, including graphics and text, and the number of potentially distracting nontarget links was varied. Increased link size improved performance, whereas increased clutter and links hampered search, especially for older adults. Results also showed that links located in the left region of the page were found most easily. Actual or potential applications of this research include Web site design to increase usability, particularly for older adults.

  3. A New Conflict Resolution Method for Multiple Mobile Robots in Cluttered Environments With Motion-Liveness.

    Science.gov (United States)

    Shahriari, Mohammadali; Biglarbegian, Mohammad

    2018-01-01

    This paper presents a new conflict resolution methodology for multiple mobile robots while ensuring their motion-liveness, especially for cluttered and dynamic environments. Our method constructs a mathematical formulation in a form of an optimization problem by minimizing the overall travel times of the robots subject to resolving all the conflicts in their motion. This optimization problem can be easily solved through coordinating only the robots' speeds. To overcome the computational cost in executing the algorithm for very cluttered environments, we develop an innovative method through clustering the environment into independent subproblems that can be solved using parallel programming techniques. We demonstrate the scalability of our approach through performing extensive simulations. Simulation results showed that our proposed method is capable of resolving the conflicts of 100 robots in less than 1.23 s in a cluttered environment that has 4357 intersections in the paths of the robots. We also developed an experimental testbed and demonstrated that our approach can be implemented in real time. We finally compared our approach with other existing methods in the literature both quantitatively and qualitatively. This comparison shows while our approach is mathematically sound, it is more computationally efficient, scalable for very large number of robots, and guarantees the live and smooth motion of robots.

  4. Combined radar and telemetry system

    Energy Technology Data Exchange (ETDEWEB)

    Rodenbeck, Christopher T.; Young, Derek; Chou, Tina; Hsieh, Lung-Hwa; Conover, Kurt; Heintzleman, Richard

    2017-08-01

    A combined radar and telemetry system is described. The combined radar and telemetry system includes a processing unit that executes instructions, where the instructions define a radar waveform and a telemetry waveform. The processor outputs a digital baseband signal based upon the instructions, where the digital baseband signal is based upon the radar waveform and the telemetry waveform. A radar and telemetry circuit transmits, simultaneously, a radar signal and telemetry signal based upon the digital baseband signal.

  5. Aspects of Radar Polarimetry

    OpenAIRE

    LÜNEBURG, Ernst

    2002-01-01

    This contribution is a tutorial introduction to the phenomenological theory of radar polarimetry for the coherent scatter case emphasizing monostatic backscattering and forward scattering (transmission). Characteristic similarities and differences between radar polarimetry and optical polarimetry and the role of linear and antilinear operators (time-reversal) are pointed out and typical polarimetric invariants are identified.

  6. Java Radar Analysis Tool

    Science.gov (United States)

    Zaczek, Mariusz P.

    2005-01-01

    Java Radar Analysis Tool (JRAT) is a computer program for analyzing two-dimensional (2D) scatter plots derived from radar returns showing pieces of the disintegrating Space Shuttle Columbia. JRAT can also be applied to similar plots representing radar returns showing aviation accidents, and to scatter plots in general. The 2D scatter plots include overhead map views and side altitude views. The superposition of points in these views makes searching difficult. JRAT enables three-dimensional (3D) viewing: by use of a mouse and keyboard, the user can rotate to any desired viewing angle. The 3D view can include overlaid trajectories and search footprints to enhance situational awareness in searching for pieces. JRAT also enables playback: time-tagged radar-return data can be displayed in time order and an animated 3D model can be moved through the scene to show the locations of the Columbia (or other vehicle) at the times of the corresponding radar events. The combination of overlays and playback enables the user to correlate a radar return with a position of the vehicle to determine whether the return is valid. JRAT can optionally filter single radar returns, enabling the user to selectively hide or highlight a desired radar return.

  7. Determination of radar MTF

    Energy Technology Data Exchange (ETDEWEB)

    Chambers, D. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The ultimate goal of the Current Meter Array (CMA) is to be able to compare the current patterns detected with the array with radar images of the water surface. The internal wave current patterns modulate the waves on the water surface giving a detectable modulation of the radar cross-section (RCS). The function relating the RCS modulations to the current patterns is the Modulation Transfer Function (MTF). By comparing radar images directly with co-located CMA measurements the MTF can be determined. In this talk radar images and CMA measurements from a recent experiment at Loch Linnhe, Scotland, will be used to make the first direct determination of MTF for an X and S band radar at low grazing angles. The technical problems associated with comparing radar images to CMA data will be explained and the solution method discussed. The results suggest the both current and strain rate contribute equally to the radar modulation for X band. For S band, the strain rate contributes more than the current. The magnitude of the MTF and the RCS modulations are consistent with previous estimates when the wind is blowing perpendicular to the radar look direction.

  8. On the feasibility of space-based radar ice sounding of the Antarctic ice sheet at P-band

    DEFF Research Database (Denmark)

    Dall, Jørgen; Kusk, Anders; Corr, Hugh

    . In this study the feasibility of space-based radar ice sounding is assessed. A two-step approach is applied: (1) Key ice sheet parameters are estimated from the airborne POLARIS data acquired in Antarctica. (2) The performance of potential space-based ice sounding radars is simulated based on the estimated ice...... data analysis estimating the scattering patterns via the Doppler spectra of the POLARIS data. The scattering patterns of the ice surfaces are relevant because the geometry of a space-based radar increases the risk that off-nadir surface clutter masks the nadir depth-signal of interest. Currently...... the ice sheet model is being established and validated. At the symposium measured and simulated satellite waveforms will be compared, and the feasibility of space-based ice sounding will be addressed....

  9. Principles of modern radar radar applications

    CERN Document Server

    Scheer, James A

    2013-01-01

    Principles of Modern Radar: Radar Applications is the third of the three-volume seriesof what was originally designed to be accomplished in one volume. As the final volumeof the set, it finishes the original vision of a complete yet bounded reference for radartechnology. This volume describes fifteen different system applications or class ofapplications in more detail than can be found in Volumes I or II.As different as the applications described, there is a difference in how these topicsare treated by the authors. Whereas in Volumes I and II there is strict adherence tochapter format and leve

  10. Theory and Measurement of Signal-to-Noise Ratio in Continuous-Wave Noise Radar.

    Science.gov (United States)

    Stec, Bronisław; Susek, Waldemar

    2018-05-06

    Determination of the signal power-to-noise power ratio on the input and output of reception systems is essential to the estimation of their quality and signal reception capability. This issue is especially important in the case when both signal and noise have the same characteristic as Gaussian white noise. This article considers the problem of how a signal-to-noise ratio is changed as a result of signal processing in the correlation receiver of a noise radar in order to determine the ability to detect weak features in the presence of strong clutter-type interference. These studies concern both theoretical analysis and practical measurements of a noise radar with a digital correlation receiver for 9.2 GHz bandwidth. Firstly, signals participating individually in the correlation process are defined and the terms signal and interference are ascribed to them. Further studies show that it is possible to distinguish a signal and a noise on the input and output of a correlation receiver, respectively, when all the considered noises are in the form of white noise. Considering the above, a measurement system is designed in which it is possible to represent the actual conditions of noise radar operation and power measurement of a useful noise signal and interference noise signals—in particular the power of an internal leakage signal between a transmitter and a receiver of the noise radar. The proposed measurement stands and the obtained results show that it is possible to optimize with the use of the equipment and not with the complex processing of a noise signal. The radar parameters depend on its prospective application, such as short- and medium-range radar, ground-penetrating radar, and through-the-wall detection radar.

  11. Progress in coherent laser radar

    Science.gov (United States)

    Vaughan, J. M.

    1986-01-01

    Considerable progress with coherent laser radar has been made over the last few years, most notably perhaps in the available range of high performance devices and components and the confidence with which systems may now be taken into the field for prolonged periods of operation. Some of this increasing maturity was evident at the 3rd Topical Meeting on Coherent Laser Radar: Technology and Applications. Topics included in discussions were: mesoscale wind fields, nocturnal valley drainage and clear air down bursts; airborne Doppler lidar studies and comparison of ground and airborne wind measurement; wind measurement over the sea for comparison with satellite borne microwave sensors; transport of wake vortices at airfield; coherent DIAL methods; a newly assembled Nd-YAG coherent lidar system; backscatter profiles in the atmosphere and wavelength dependence over the 9 to 11 micrometer region; beam propagation; rock and soil classification with an airborne 4-laser system; technology of a global wind profiling system; target calibration; ranging and imaging with coherent pulsed and CW system; signal fluctuations and speckle. Some of these activities are briefly reviewed.

  12. BALTRAD Advanced Weather Radar Networking

    Directory of Open Access Journals (Sweden)

    Daniel Michelson

    2018-03-01

    Full Text Available BALTRAD software exchanges weather-radar data internationally, operationally, and in real-time, and it processes the data using a common toolbox of algorithms available to every node in the decentralized radar network. This approach enables each node to access and process its own and international data to meet its local needs. The software system is developed collaboratively by the BALTRAD partnership, mostly comprising the national Meteorological and Hydrological institutes in the European Union’s Baltic Sea Region. The most important sub-systems are for data exchange, data management, scheduling and event handling, and data processing. C, Java, and Python languages are used depending on the sub-system, and sub-systems communicate using well-defined interfaces. Software is available from a dedicated Git server. BALTRAD software has been deployed throughout Europe and more recently in Canada. Funding statement: From 2009–2014, the BALTRAD and BALTRAD+ projects were part-financed by the European Union (European Regional Development Fund and European Neighbourhood and Partnership Instrument, with project numbers #009 and #101, respectively.

  13. Prediction of buried mine-like target radar signatures using wideband electromagnetic modeling

    Energy Technology Data Exchange (ETDEWEB)

    Warrick, A.L.; Azevedo, S.G.; Mast, J.E.

    1998-04-06

    Current ground penetrating radars (GPR) have been tested for land mine detection, but they have generally been costly and have poor performance. Comprehensive modeling and experimentation must be done to predict the electromagnetic (EM) signatures of mines to access the effect of clutter on the EM signature of the mine, and to understand the merit and limitations of using radar for various mine detection scenarios. This modeling can provide a basis for advanced radar design and detection techniques leading to superior performance. Lawrence Livermore National Laboratory (LLNL) has developed a radar technology that when combined with comprehensive modeling and detection methodologies could be the basis of an advanced mine detection system. Micropower Impulse Radar (MIR) technology exhibits a combination of properties, including wideband operation, extremely low power consumption, extremely small size and low cost, array configurability, and noise encoded pulse generation. LLNL is in the process of developing an optimal processing algorithm to use with the MIR sensor. In this paper, we use classical numerical models to obtain the signature of mine-like targets and examine the effect of surface roughness on the reconstructed signals. These results are then qualitatively compared to experimental data.

  14. Weather radar performance monitoring using a metallic-grid ground-scatterer

    Science.gov (United States)

    Falconi, Marta Tecla; Montopoli, Mario; Marzano, Frank Silvio; Baldini, Luca

    2017-10-01

    The use of ground return signals is investigated for checks on the calibration of power measurements of a polarimetric C-band radar. To this aim, a peculiar permanent single scatterer (PSS) consisting of a big metallic roof with a periodic mesh grid structure and having a hemisphere-like shape is considered. The latter is positioned in the near-field region of the weather radar and its use, as a reference calibrator, shows fairly good results in terms of reflectivity and differential reflectivity monitoring. In addition, the use of PSS indirectly allows to check for the radar antenna de-pointing which is another issue usually underestimated when dealing with weather radars. Because of the periodic structure of the considered PSS, simulations of its electromagnetic behavior were relatively easy to perform. To this goal, we used an electromagnetic Computer-Aided-Design (CAD) with an ad-hoc numerical implementation of a full-wave solution to model our PSS in terms of reflectivity and differential reflectivity factor. Comparison of model results and experimental measurements are then shown in this work. Our preliminary investigation can pave the way for future studies aiming at characterizing ground-clutter returns in a more accurate way for radar calibration purposes.

  15. Acquisition and use of Orlando, Florida and Continental Airbus radar flight test data

    Science.gov (United States)

    Eide, Michael C.; Mathews, Bruce

    1992-01-01

    Westinghouse is developing a lookdown pulse Doppler radar for production as the sensor and processor of a forward looking hazardous windshear detection and avoidance system. A data collection prototype of that product was ready for flight testing in Orlando to encounter low level windshear in corroboration with the FAA-Terminal Doppler Weather Radar (TDWR). Airborne real-time processing and display of the hazard factor were demonstrated with TDWR facilitated intercepts and penetrations of over 80 microbursts in a three day period, including microbursts with hazard factors in excess of .16 (with 500 ft. PIREP altitude loss) and the hazard factor display at 6 n.mi. of a visually transparent ('dry') microburst with TDWR corroborated outflow reflectivities of +5 dBz. Range gated Doppler spectrum data was recorded for subsequent development and refinement of hazard factor detection and urban clutter rejection algorithms. Following Orlando, the data collection radar was supplemental type certified for in revenue service on a Continental Airlines Airbus in an automatic and non-interferring basis with its ARINC 708 radar to allow Westinghouse to confirm its understanding of commercial aircraft installation, interface realities, and urban airport clutter. A number of software upgrades, all of which were verified at the Receiver-Transmitter-Processor (RTP) hardware bench with Orlando microburst data to produce desired advanced warning hazard factor detection, included some preliminary loads with automatic (sliding window average hazard factor) detection and annunciation recording. The current (14-APR-92) configured software is free from false and/or nuisance alerts (CAUTIONS, WARNINGS, etc.) for all take-off and landing approaches, under 2500 ft. altitude to weight-on-wheels, into all encountered airports, including Newark (NJ), LAX, Denver, Houston, Cleveland, etc. Using the Orlando data collected on hazardous microbursts, Westinghouse has developed a lookdown pulse Doppler

  16. The physical basis for estimating wave-energy spectra with the radar ocean-wave spectrometer

    Science.gov (United States)

    Jackson, Frederick C.

    1987-01-01

    The derivation of the reflectivity modulation spectrum of the sea surface for near-nadir-viewing microwave radars using geometrical optics is described. The equations required for the derivation are presented. The derived reflectivity modulation spectrum provides data on the physical basis of the radar ocean-wave spectrometer measurements of ocean-wave directional spectra.

  17. Radar-to-Radar Interference Suppression for Distributed Radar Sensor Networks

    Directory of Open Access Journals (Sweden)

    Wen-Qin Wang

    2014-01-01

    Full Text Available Radar sensor networks, including bi- and multi-static radars, provide several operational advantages, like reduced vulnerability, good system flexibility and an increased radar cross-section. However, radar-to-radar interference suppression is a major problem in distributed radar sensor networks. In this paper, we present a cross-matched filtering-based radar-to-radar interference suppression algorithm. This algorithm first uses an iterative filtering algorithm to suppress the radar-to-radar interferences and, then, separately matched filtering for each radar. Besides the detailed algorithm derivation, extensive numerical simulation examples are performed with the down-chirp and up-chirp waveforms, partially overlapped or inverse chirp rate linearly frequency modulation (LFM waveforms and orthogonal frequency division multiplexing (ODFM chirp diverse waveforms. The effectiveness of the algorithm is verified by the simulation results.

  18. Radar remote sensing in biology

    Science.gov (United States)

    Moore, Richard K.; Simonett, David S.

    1967-01-01

    The present status of research on discrimination of natural and cultivated vegetation using radar imaging systems is sketched. The value of multiple polarization radar in improved discrimination of vegetation types over monoscopic radars is also documented. Possible future use of multi-frequency, multi-polarization radar systems for all weather agricultural survey is noted.

  19. Novel radar techniques and applications

    CERN Document Server

    Klemm, Richard; Koch, Wolfgang

    2017-01-01

    Novel Radar Techniques and Applications presents the state-of-the-art in advanced radar, with emphasis on ongoing novel research and development and contributions from an international team of leading radar experts. This volume covers: Waveform diversity and cognitive radar and Target tracking and data fusion.

  20. A novel through-wall respiration detection algorithm using UWB radar.

    Science.gov (United States)

    Li, Xin; Qiao, Dengyu; Li, Ye; Dai, Huhe

    2013-01-01

    Through-wall respiration detection using Ultra-wideband (UWB) impulse radar can be applied to the post-disaster rescue, e.g., searching living persons trapped in ruined buildings after an earthquake. Since strong interference signals always exist in the real-life scenarios, such as static clutter, noise, etc., while the respiratory signal is very weak, the signal to noise and clutter ratio (SNCR) is quite low. Therefore, through-wall respiration detection using UWB impulse radar under low SNCR is a challenging work in the research field of searching survivors after disaster. In this paper, an improved UWB respiratory signal model is built up based on an even power of cosine function for the first time. This model is used to reveal the harmonic structure of respiratory signal, based on which a novel high-performance respiration detection algorithm is proposed. This novel algorithm is assessed by experimental verification and simulation and shows about a 1.5dB improvement of SNR and SNCR.

  1. Radar and electronic navigation

    CERN Document Server

    Sonnenberg, G J

    2013-01-01

    Radar and Electronic Navigation, Sixth Edition discusses radar in marine navigation, underwater navigational aids, direction finding, the Decca navigator system, and the Omega system. The book also describes the Loran system for position fixing, the navy navigation satellite system, and the global positioning system (GPS). It reviews the principles, operation, presentations, specifications, and uses of radar. It also describes GPS, a real time position-fixing system in three dimensions (longitude, latitude, altitude), plus velocity information with Universal Time Coordinated (UTC). It is accur

  2. Wind farm radar study

    International Nuclear Information System (INIS)

    Davies, N.G.

    1995-01-01

    This report examines the possible degradations of radar performance that may be caused by the presence of a wind turbine generator within the radar coverage area. A brief literature survey reviews the previously published work, which is mainly concerned with degradation of broadcast TV reception. Estimates are made of wind turbine generator scattering cross-sections, and of the time and Doppler characteristics of the echo signals from representative wind turbine generator. The general characteristics of radar detection and tracking methods are described, and the behaviour of such systems in the presence of strong returns from a wind turbine generator (or an array of them) is discussed. (author)

  3. Radar observations of Mercury

    International Nuclear Information System (INIS)

    Harmon, J.K.; Campbell, D.B.

    1988-01-01

    Some of the radar altimetry profiles of Mercury obtained on the basis of data from the Arecibo Observatory are presented. In these measurements, the delay-Doppler method was used to measure altitudes along the Doppler equator, rather than to map radar reflectivity. The profiles, derived from observations made over a 6-yr period, provide extensive coverage over a restricted equatorial band and permit the identification of radar signatures for features as small as 50-km diameter craters and 1-km-high arcuate scarps. The data allowed identification of large-scale topographic features such as smooth plains subsidence zones and major highland regions

  4. Radar cross section

    CERN Document Server

    Knott, Gene; Tuley, Michael

    2004-01-01

    This is the second edition of the first and foremost book on this subject for self-study, training, and course work. Radar cross section (RCS) is a comparison of two radar signal strengths. One is the strength of the radar beam sweeping over a target, the other is the strength of the reflected echo sensed by the receiver. This book shows how the RCS ?gauge? can be predicted for theoretical objects and how it can be measured for real targets. Predicting RCS is not easy, even for simple objects like spheres or cylinders, but this book explains the two ?exact? forms of theory so well that even a

  5. Radar Remote Sensing

    Science.gov (United States)

    Rosen, Paul A.

    2012-01-01

    This lecture was just a taste of radar remote sensing techniques and applications. Other important areas include Stereo radar grammetry. PolInSAR for volumetric structure mapping. Agricultural monitoring, soil moisture, ice-mapping, etc. The broad range of sensor types, frequencies of observation and availability of sensors have enabled radar sensors to make significant contributions in a wide area of earth and planetary remote sensing sciences. The range of applications, both qualitative and quantitative, continue to expand with each new generation of sensors.

  6. Logarithmic r-θ mapping for hybrid optical neural network filter for multiple objects recognition within cluttered scenes

    Science.gov (United States)

    Kypraios, Ioannis; Young, Rupert C. D.; Chatwin, Chris R.; Birch, Phil M.

    2009-04-01

    θThe window unit in the design of the complex logarithmic r-θ mapping for hybrid optical neural network filter can allow multiple objects of the same class to be detected within the input image. Additionally, the architecture of the neural network unit of the complex logarithmic r-θ mapping for hybrid optical neural network filter becomes attractive for accommodating the recognition of multiple objects of different classes within the input image by modifying the output layer of the unit. We test the overall filter for multiple objects of the same and of different classes' recognition within cluttered input images and video sequences of cluttered scenes. Logarithmic r-θ mapping for hybrid optical neural network filter is shown to exhibit with a single pass over the input data simultaneously in-plane rotation, out-of-plane rotation, scale, log r-θ map translation and shift invariance, and good clutter tolerance by recognizing correctly the different objects within the cluttered scenes. We record in our results additional extracted information from the cluttered scenes about the objects' relative position, scale and in-plane rotation.

  7. NOAA Laboratory for Satellite Altimetry Sea Level Rise Products: Global and regional sea level time series and trend maps for the major ocean basins and marginal seas, based on measurements from satellite radar altimeters, from 1992-12-17 to 2017-08-11 (NCEI Accession 0125535)

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This archival package contains global and regional mean sea level time series and trend maps calculated on a continual basis since December 1992 by Laboratory for...

  8. Improved Laser Vibration Radar

    National Research Council Canada - National Science Library

    Hilaire, Pierre

    1998-01-01

    .... This thesis reconfigured an existing CO2 laboratory laser radar system that is capable of measuring the frequencies of vibration of a simulated target into a more compact and rugged form for field testing...

  9. Weather radars – the new eyes for offshore wind farms?

    DEFF Research Database (Denmark)

    Trombe, Pierre-Julien; Pinson, Pierre; Vincent, Claire Louise

    2014-01-01

    Offshore wind fluctuations are such that dedicated prediction and control systems are needed for optimizing the management of wind farms in real-time. In this paper, we present a pioneer experiment – Radar@Sea – in which weather radars are used for monitoring the weather at the Horns Rev offshore...... inputs to prediction systems for anticipating changes in the wind fluctuation dynamics, generating improved wind power forecasts and developing specific control strategies. However, integrating weather radar observations into automated decision support systems is not a plug-and-play task...... observed at Horns Rev and (iv) we discuss the future perspectives for weather radars in wind energy. Copyright © 2013 John Wiley & Sons, Ltd....

  10. Phased-array radars

    Science.gov (United States)

    Brookner, E.

    1985-02-01

    The operating principles, technology, and applications of phased-array radars are reviewed and illustrated with diagrams and photographs. Consideration is given to the antenna elements, circuitry for time delays, phase shifters, pulse coding and compression, and hybrid radars combining phased arrays with lenses to alter the beam characteristics. The capabilities and typical hardware of phased arrays are shown using the US military systems COBRA DANE and PAVE PAWS as examples.

  11. Radar detection of Vesta

    International Nuclear Information System (INIS)

    Ostro, S.J.; Cornell University, Ithaca, N.Y.); Campbell, D.B.; Pettengill, G.H.

    1980-01-01

    Asteroid 4 Vesta was detected on November 6, 1979 with the Arecibo Observatory's S-band (12.6-cm-wavelength) radar. The echo power spectrum, received in the circular polarization opposite to that transmitted, yields a radar cross section of (0.2 + or - 0.1)pi a-squared, for a 272 km. The data are too noisy to permit derivation of Vesta's rotation period

  12. Downhole pulse radar

    Science.gov (United States)

    Chang, Hsi-Tien

    1987-09-28

    A borehole logging tool generates a fast rise-time, short duration, high peak-power radar pulse having broad energy distribution between 30 MHz and 300 MHz through a directional transmitting and receiving antennas having barium titanate in the electromagnetically active region to reduce the wavelength to within an order of magnitude of the diameter of the antenna. Radar returns from geological discontinuities are sampled for transmission uphole. 7 figs.

  13. Segmentation of vessels cluttered with cells using a physics based model.

    Science.gov (United States)

    Schmugge, Stephen J; Keller, Steve; Nguyen, Nhat; Souvenir, Richard; Huynh, Toan; Clemens, Mark; Shin, Min C

    2008-01-01

    Segmentation of vessels in biomedical images is important as it can provide insight into analysis of vascular morphology, topology and is required for kinetic analysis of flow velocity and vessel permeability. Intravital microscopy is a powerful tool as it enables in vivo imaging of both vasculature and circulating cells. However, the analysis of vasculature in those images is difficult due to the presence of cells and their image gradient. In this paper, we provide a novel method of segmenting vessels with a high level of cell related clutter. A set of virtual point pairs ("vessel probes") are moved reacting to forces including Vessel Vector Flow (VVF) and Vessel Boundary Vector Flow (VBVF) forces. Incorporating the cell detection, the VVF force attracts the probes toward the vessel, while the VBVF force attracts the virtual points of the probes to localize the vessel boundary without being distracted by the image features of the cells. The vessel probes are moved according to Newtonian Physics reacting to the net of forces applied on them. We demonstrate the results on a set of five real in vivo images of liver vasculature cluttered by white blood cells. When compared against the ground truth prepared by the technician, the Root Mean Squared Error (RMSE) of segmentation with VVF and VBVF was 55% lower than the method without VVF and VBVF.

  14. Coordinate-Based Clustering Method for Indoor Fingerprinting Localization in Dense Cluttered Environments

    Directory of Open Access Journals (Sweden)

    Wen Liu

    2016-12-01

    Full Text Available Indoor positioning technologies has boomed recently because of the growing commercial interest in indoor location-based service (ILBS. Due to the absence of satellite signal in Global Navigation Satellite System (GNSS, various technologies have been proposed for indoor applications. Among them, Wi-Fi fingerprinting has been attracting much interest from researchers because of its pervasive deployment, flexibility and robustness to dense cluttered indoor environments. One challenge, however, is the deployment of Access Points (AP, which would bring a significant influence on the system positioning accuracy. This paper concentrates on WLAN based fingerprinting indoor location by analyzing the AP deployment influence, and studying the advantages of coordinate-based clustering compared to traditional RSS-based clustering. A coordinate-based clustering method for indoor fingerprinting location, named Smallest-Enclosing-Circle-based (SEC, is then proposed aiming at reducing the positioning error lying in the AP deployment and improving robustness to dense cluttered environments. All measurements are conducted in indoor public areas, such as the National Center For the Performing Arts (as Test-bed 1 and the XiDan Joy City (Floors 1 and 2, as Test-bed 2, and results show that SEC clustering algorithm can improve system positioning accuracy by about 32.7% for Test-bed 1, 71.7% for Test-bed 2 Floor 1 and 73.7% for Test-bed 2 Floor 2 compared with traditional RSS-based clustering algorithms such as K-means.

  15. Coordinate-Based Clustering Method for Indoor Fingerprinting Localization in Dense Cluttered Environments.

    Science.gov (United States)

    Liu, Wen; Fu, Xiao; Deng, Zhongliang

    2016-12-02

    Indoor positioning technologies has boomed recently because of the growing commercial interest in indoor location-based service (ILBS). Due to the absence of satellite signal in Global Navigation Satellite System (GNSS), various technologies have been proposed for indoor applications. Among them, Wi-Fi fingerprinting has been attracting much interest from researchers because of its pervasive deployment, flexibility and robustness to dense cluttered indoor environments. One challenge, however, is the deployment of Access Points (AP), which would bring a significant influence on the system positioning accuracy. This paper concentrates on WLAN based fingerprinting indoor location by analyzing the AP deployment influence, and studying the advantages of coordinate-based clustering compared to traditional RSS-based clustering. A coordinate-based clustering method for indoor fingerprinting location, named Smallest-Enclosing-Circle-based (SEC), is then proposed aiming at reducing the positioning error lying in the AP deployment and improving robustness to dense cluttered environments. All measurements are conducted in indoor public areas, such as the National Center For the Performing Arts (as Test-bed 1) and the XiDan Joy City (Floors 1 and 2, as Test-bed 2), and results show that SEC clustering algorithm can improve system positioning accuracy by about 32.7% for Test-bed 1, 71.7% for Test-bed 2 Floor 1 and 73.7% for Test-bed 2 Floor 2 compared with traditional RSS-based clustering algorithms such as K-means.

  16. PMHT Approach for Multi-Target Multi-Sensor Sonar Tracking in Clutter.

    Science.gov (United States)

    Li, Xiaohua; Li, Yaan; Yu, Jing; Chen, Xiao; Dai, Miao

    2015-11-06

    Multi-sensor sonar tracking has many advantages, such as the potential to reduce the overall measurement uncertainty and the possibility to hide the receiver. However, the use of multi-target multi-sensor sonar tracking is challenging because of the complexity of the underwater environment, especially the low target detection probability and extremely large number of false alarms caused by reverberation. In this work, to solve the problem of multi-target multi-sensor sonar tracking in the presence of clutter, a novel probabilistic multi-hypothesis tracker (PMHT) approach based on the extended Kalman filter (EKF) and unscented Kalman filter (UKF) is proposed. The PMHT can efficiently handle the unknown measurements-to-targets and measurements-to-transmitters data association ambiguity. The EKF and UKF are used to deal with the high degree of nonlinearity in the measurement model. The simulation results show that the proposed algorithm can improve the target tracking performance in a cluttered environment greatly, and its computational load is low.

  17. Assessment of the Performance of the Chilbolton 3-GHz Advanced Meteorological Radar for Cloud-Top-Height Retrieval.

    Science.gov (United States)

    Naud, C. M.; Muller, J.-P.; Slack, E. C.; Wrench, C. L.; Clothiaux, E. E.

    2005-06-01

    The Chilbolton 3-GHz Advanced Meteorological Radar (CAMRa), which is mounted on a fully steerable 25-m dish, can provide three-dimensional information on the presence of hydrometeors. The potential for this radar to make useful measurements of low-altitude liquid water cloud structure is investigated. To assess the cloud-height assignment capabilities of the 3-GHz radar, low-level cloud-top heights were retrieved from CAMRa measurements made between May and July 2003 and were compared with cloud-top heights retrieved from a vertically pointing 94-GHz radar that operates alongside CAMRa. The average difference between the 94- and 3-GHz radar-derived cloud-top heights is shown to be -0.1 ± 0.4 km. To assess the capability of 3-GHz radar scans to be used for satellite-derived cloud-top-height validation, multiangle imaging spectroradiometer (MISR) cloud-top heights were compared with both 94- and 3-GHz radar retrievals. The average difference between 94-GHz radar and MISR cloud-top heights is shown to be 0.1 ± 0.3 km, while the 3-GHz radar and MISR average cloud-top-height difference is shown to be -0.2 ± 0.6 km. In assessing the value of the CAMRa measurements, the problems associated with low-reflectivity values from stratiform liquid water clouds, ground clutter, and Bragg scattering resulting from turbulent mixing are all addressed. It is shown that, despite the difficulties, the potential exists for CAMRa measurements to contribute significantly to liquid water cloud-top-height retrievals, leading to the production of two-dimensional transects (i.e., maps) of cloud-top height.

  18. CAMEX-4 TOGA RADAR V1

    Data.gov (United States)

    National Aeronautics and Space Administration — The TOGA radar dataset consists of browse and radar data collected from the TOGA radar during the CAMEX-4 experiment. TOGA is a C-band linear polarized doppler radar...

  19. Lava flows in mare imbrium: An evaluation of anomalously low earth-based radar reflectivity

    Science.gov (United States)

    Schaber, G.G.; Thompson, T.W.; Zisk, S.H.

    1975-01-01

    The lunar maria reflect two to five times less Earth-based radar power than the highlands, the spectrally blue maria surfaces returning the lowest power levels. This effect of weakening signal return has been attributed to increased signal absorption related to the electrical and magnetic characteristics of the mineral ilmenite (FeTiO3). The surface of Mare Imbrium contains some of the most distinct red-blue colorimetric boundaries and depolarized 70 cm wavelength reflectivity variations on the near side of the Moon. The weakest levels of both 3.8 cm and 70 cm reflectivity within Imbrium are confined to regional mare surfaces of the blue spectral type that can be recognized as stratigraphically unique flow surfaces. Frequency distributions of the 70 cm polarized and depolarized radar return power for five mare surfaces within the basin indicate that signal absorption, and probably the ilmenite content, increases generally from the beginning of the Imbrian Period to the end of the Eratosthenian Period with slight reversal between the end of the Imbrian and beginning of the Eratosthenian. TiO2 calibrated radar reflectivity curves can be utilized for lunar maria geochemical mapping in the same manner as the TiO2 calibrated spectral reflectivity curves of Charette et al. (1974). The long wavelength radar data may be a sensitive indicator of mare chemical variations as it is unaffected by the normal surface rock clutter that includes ray materials from large impact craters. ?? 1975 D. Reidel Publishing Company.

  20. Portable concealed weapon detection using millimeter-wave FMCW radar imaging

    Science.gov (United States)

    Johnson, Michael A.; Chang, Yu-Wen

    2001-02-01

    Unobtrusive detection of concealed weapons on persons or in abandoned bags would provide law enforcement a powerful tool to focus resources and increase traffic throughput in high- risk situations. We have developed a fast image scanning 94 GHz radar system that is suitable for portable operation and remote viewing of radar data. This system includes a novel fast image-scanning antenna that allows for the acquisition of medium resolution 3D millimeter wave images of stationary targets with frame times on order of one second. The 3D radar data allows for potential isolation of concealed weapons from body and environmental clutter such as nearby furniture or other people. The radar is an active system so image quality is not affected indoors, emitted power is however very low so there are no health concerns for operator or targets. The low power operation is still sufficient to penetrate heavy clothing or material. Small system size allows for easy transport and rapid deployment of the system as well as an easy migration path to future hand held systems.

  1. Random Forest Application for NEXRAD Radar Data Quality Control

    Science.gov (United States)

    Keem, M.; Seo, B. C.; Krajewski, W. F.

    2017-12-01

    Identification and elimination of non-meteorological radar echoes (e.g., returns from ground, wind turbines, and biological targets) are the basic data quality control steps before radar data use in quantitative applications (e.g., precipitation estimation). Although WSR-88Ds' recent upgrade to dual-polarization has enhanced this quality control and echo classification, there are still challenges to detect some non-meteorological echoes that show precipitation-like characteristics (e.g., wind turbine or anomalous propagation clutter embedded in rain). With this in mind, a new quality control method using Random Forest is proposed in this study. This classification algorithm is known to produce reliable results with less uncertainty. The method introduces randomness into sampling and feature selections and integrates consequent multiple decision trees. The multidimensional structure of the trees can characterize the statistical interactions of involved multiple features in complex situations. The authors explore the performance of Random Forest method for NEXRAD radar data quality control. Training datasets are selected using several clear cases of precipitation and non-precipitation (but with some non-meteorological echoes). The model is structured using available candidate features (from the NEXRAD data) such as horizontal reflectivity, differential reflectivity, differential phase shift, copolar correlation coefficient, and their horizontal textures (e.g., local standard deviation). The influence of each feature on classification results are quantified by variable importance measures that are automatically estimated by the Random Forest algorithm. Therefore, the number and types of features in the final forest can be examined based on the classification accuracy. The authors demonstrate the capability of the proposed approach using several cases ranging from distinct to complex rain/no-rain events and compare the performance with the existing algorithms (e

  2. Location detection and tracking of moving targets by a 2D IR-UWB radar system.

    Science.gov (United States)

    Nguyen, Van-Han; Pyun, Jae-Young

    2015-03-19

    In indoor environments, the Global Positioning System (GPS) and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB) technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB) radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF) is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking.

  3. Location Detection and Tracking of Moving Targets by a 2D IR-UWB Radar System

    Directory of Open Access Journals (Sweden)

    Van-Han Nguyen

    2015-03-01

    Full Text Available In indoor environments, the Global Positioning System (GPS and long-range tracking radar systems are not optimal, because of signal propagation limitations in the indoor environment. In recent years, the use of ultra-wide band (UWB technology has become a possible solution for object detection, localization and tracking in indoor environments, because of its high range resolution, compact size and low cost. This paper presents improved target detection and tracking techniques for moving objects with impulse-radio UWB (IR-UWB radar in a short-range indoor area. This is achieved through signal-processing steps, such as clutter reduction, target detection, target localization and tracking. In this paper, we introduce a new combination consisting of our proposed signal-processing procedures. In the clutter-reduction step, a filtering method that uses a Kalman filter (KF is proposed. Then, in the target detection step, a modification of the conventional CLEAN algorithm which is used to estimate the impulse response from observation region is applied for the advanced elimination of false alarms. Then, the output is fed into the target localization and tracking step, in which the target location and trajectory are determined and tracked by using unscented KF in two-dimensional coordinates. In each step, the proposed methods are compared to conventional methods to demonstrate the differences in performance. The experiments are carried out using actual IR-UWB radar under different scenarios. The results verify that the proposed methods can improve the probability and efficiency of target detection and tracking.

  4. A positioning system with no line-of-sight restrictions for cluttered environments

    Science.gov (United States)

    Prigge, Eric A.

    Accurate sensing of vehicle location and attitude is a fundamental requirement in many mobile-robot applications, but is a very challenging problem in the cluttered and unstructured environment of the real world. Many existing indoor positioning systems are limited in workspace and robustness because they require clear lines of sight or do not provide absolute, drift-free measurements. Examples include overhead vision systems, where an unobstructed view must be maintained between robot and camera, and inertial systems, where the measurements drift over time. The research presented in this dissertation provides a new location- and attitude-sensing system designed specifically to meet the challenges of operation in a realistic, cluttered indoor environment, such as that of an office building or warehouse. The system is not limited by line-of-sight restrictions and produces drift-free measurements throughout a three-dimensional operating volume that can span a large building. Accuracy of several centimeters and a few degrees is delivered at 10 Hz, and any number of the small sensor units can be in operation, all providing estimates in a common reference frame. This positioning system is based on extremely-low-frequency magnetic fields, which have excellent characteristics for penetrating line-of-sight obstructions. Beacons located throughout the workspace create the low-level fields. A sensor unit on the mobile robot samples the local magnetic field and processes the measurements to determine its location and attitude. This research overcomes limitations in existing magnetic-based systems. The design of the signal structure, based on pseudorandom codes, enables the use of multiple, distributed L-beacons and greatly expands coverage volume. The development of real-time identification and correction methods mitigates the impact of distortions caused by materials in the environment. A novel solution algorithm combats both challenges, providing increased coverage volume

  5. Ground penetrating radar

    CERN Document Server

    Daniels, David J

    2004-01-01

    Ground-penetrating radar has come to public attention in recent criminal investigations, but has actually been a developing and maturing remote sensing field for some time. In the light of recent expansion of the technique to a wide range of applications, the need for an up-to-date reference has become pressing. This fully revised and expanded edition of the best-selling Surface-Penetrating Radar (IEE, 1996) presents, for the non-specialist user or engineer, all the key elements of this technique, which span several disciplines including electromagnetics, geophysics and signal processing. The

  6. Heritability and Genetic Relationship of Adult Self-Reported Stuttering, Cluttering and Childhood Speech-Language Disorders

    DEFF Research Database (Denmark)

    Fagnani, Corrado; Fibiger, Steen; Skytthe, Axel

    2011-01-01

    Genetic influence and mutual genetic relationship for adult self-reported childhood speech-language disorders, stuttering, and cluttering were studied. Using nationwide questionnaire answers from 34,944 adult Danish twins, a multivariate biometric analysis based on the liability-threshold model w...

  7. Developing the fuzzy c-means clustering algorithm based on maximum entropy for multitarget tracking in a cluttered environment

    Science.gov (United States)

    Chen, Xiao; Li, Yaan; Yu, Jing; Li, Yuxing

    2018-01-01

    For fast and more effective implementation of tracking multiple targets in a cluttered environment, we propose a multiple targets tracking (MTT) algorithm called maximum entropy fuzzy c-means clustering joint probabilistic data association that combines fuzzy c-means clustering and the joint probabilistic data association (PDA) algorithm. The algorithm uses the membership value to express the probability of the target originating from measurement. The membership value is obtained through fuzzy c-means clustering objective function optimized by the maximum entropy principle. When considering the effect of the public measurement, we use a correction factor to adjust the association probability matrix to estimate the state of the target. As this algorithm avoids confirmation matrix splitting, it can solve the high computational load problem of the joint PDA algorithm. The results of simulations and analysis conducted for tracking neighbor parallel targets and cross targets in a different density cluttered environment show that the proposed algorithm can realize MTT quickly and efficiently in a cluttered environment. Further, the performance of the proposed algorithm remains constant with increasing process noise variance. The proposed algorithm has the advantages of efficiency and low computational load, which can ensure optimum performance when tracking multiple targets in a dense cluttered environment.

  8. Systems and Methods for Radar Data Communication

    Science.gov (United States)

    Bunch, Brian (Inventor); Szeto, Roland (Inventor); Miller, Brad (Inventor)

    2013-01-01

    A radar information processing system is operable to process high bandwidth radar information received from a radar system into low bandwidth radar information that may be communicated to a low bandwidth connection coupled to an electronic flight bag (EFB). An exemplary embodiment receives radar information from a radar system, the radar information communicated from the radar system at a first bandwidth; processes the received radar information into processed radar information, the processed radar information configured for communication over a connection operable at a second bandwidth, the second bandwidth lower than the first bandwidth; and communicates the radar information from a radar system, the radar information communicated from the radar system at a first bandwidth.

  9. Human walking estimation with radar

    NARCIS (Netherlands)

    Dorp, Ph. van; Groen, F.C.A.

    2003-01-01

    Radar can be used to observe humans that are obscured by objects such as walls. These humans cannot be visually observed. The radar measurements are used to animate an obscured human in virtual reality. This requires detailed information about the motion. The radar measurements give detailed

  10. Probing Small Lakes on Titan Using the Cassini RADAR Altimeter

    Science.gov (United States)

    Mastrogiuseppe, M.; Poggiali, V.; Hayes, A.; Lunine, J. I.; Seu, R.; Lorenz, R. D.; Mitri, G.; Mitchell, K. L.; Janssen, M. A.; Casarano, D.; Notarnicola, C.; Le Gall, A. A.

    2017-12-01

    The T126 Cassini's final flyby of Titan has offered a unique opportunity to observe an area in the Northern Polar terrain, where several small - medium size (10 - 50 km) hydrocarbon lakes are present and have been previously imaged by Cassini. The successful observation allowed the radar to operate at the closest approach over several small lakes, using its altimetry mode for the investigation of depth and liquid composition. Herein we present the result of a dedicate processing previously applied to altimetric data acquired over Ligeia Mare where the radar revealed the bathymetry and composition of the sea [1,2]. We show that, the optimal geometry condition met during the T126 fly-by allowed the radar to probe Titan's lakes revealing that such small liquid bodies can exceed one-hundred meters of depth. [1] M. Mastrogiuseppe et al. (2014, Mar.). The bathymetry of a Titan Sea. Geophysical Research Letters. [Online]. 41 (5), pp. 1432-1437. Available: http://dx.doi.org/10.1002/2013GL058618 [2] M.Mastrogiuseppe et al. (2016, Oct). Radar Sounding Using the Cassini Altimeter: Waveform Modeling and Monte Carlo Approach for Data Inversion of Observations of Titan's Seas, IEEE Transactions On Geoscience And Remote Sensing, Vol. 54, No. 10, doi: 10.1109/TGRS.2016.2563426.

  11. IFT&E Industry Report Wind Turbine-Radar Interference Test Summary.

    Energy Technology Data Exchange (ETDEWEB)

    Karlson, Benjamin; LeBlanc, Bruce Philip.; Minster, David G; Estill, Milford; Miller, Bryan Edward; Busse, Franz (MIT LL); Keck, Chris (MIT LL); Sullivan, Jonathan (MIT LL); Brigada, David (MIT LL); Parker, Lorri (MIT LL); Younger, Richard (MIT LL); Biddle, Jason (MIT LL)

    2014-10-01

    Wind turbines have grown in size and capacity with today's average turbine having a power capacity of around 1.9 MW, reaching to heights of over 495 feet from ground to blade tip, and operating with speeds at the tip of the blade up to 200 knots. When these machines are installed within the line-of-sight of a radar system, they can cause significant clutter and interference, detrimentally impacting the primary surveillance radar (PSR) performance. The Massachusetts Institute of Technology's Lincoln Laboratory (MIT LL) and Sandia National Laboratories (SNL) were co-funded to conduct field tests and evaluations over two years in order to: I. Characterize the impact of wind turbines on existing Program-of-Record (POR) air surveillance radars; II. Assess near-term technologies proposed by industry that have the potential to mitigate the interference from wind turbines on radar systems; and III. Collect data and increase technical understanding of interference issues to advance development of long-term mitigation strategies. MIT LL and SNL managed the tests and evaluated resulting data from three flight campaigns to test eight mitigation technologies on terminal (short) and long-range (60 nmi and 250 nmi) radar systems. Combined across the three flight campaigns, more than 460 of hours of flight time were logged. This paper summarizes the Interagency Field Test & Evaluation (IFT&E) program and publicly- available results from the tests. It will also discuss the current wind turbine-radar interference evaluation process within the government and a proposed process to deploy mitigation technologies.

  12. Door recognition in cluttered building interiors using imagery and lidar data

    Science.gov (United States)

    Díaz-Vilariño, L.; Martínez-Sánchez, J.; Lagüela, S.; Armesto, J.; Khoshelham, K.

    2014-06-01

    Building indoors reconstruction is an active research topic due to the importance of the wide range of applications to which they can be subjected, from architecture and furniture design, to movies and video games editing, or even crime scene investigation. Among the constructive elements defining the inside of a building, doors are important entities in applications like routing and navigation, and their automated recognition is advantageous e.g. in case of large multi-storey buildings with many office rooms. The inherent complexity of the automation of the recognition process is increased by the presence of clutter and occlusions, difficult to avoid in indoor scenes. In this work, we present a pipeline of techniques used for the reconstruction and interpretation of building interiors using information acquired in the form of point clouds and images. The methodology goes in depth with door detection and labelling as either opened, closed or furniture (false positive)

  13. Door recognition in cluttered building interiors using imagery and lidar data

    Directory of Open Access Journals (Sweden)

    L. Díaz-Vilariño

    2014-06-01

    Full Text Available Building indoors reconstruction is an active research topic due to the importance of the wide range of applications to which they can be subjected, from architecture and furniture design, to movies and video games editing, or even crime scene investigation. Among the constructive elements defining the inside of a building, doors are important entities in applications like routing and navigation, and their automated recognition is advantageous e.g. in case of large multi-storey buildings with many office rooms. The inherent complexity of the automation of the recognition process is increased by the presence of clutter and occlusions, difficult to avoid in indoor scenes. In this work, we present a pipeline of techniques used for the reconstruction and interpretation of building interiors using information acquired in the form of point clouds and images. The methodology goes in depth with door detection and labelling as either opened, closed or furniture (false positive

  14. Unified Theoretical Frame of a Joint Transmitter-Receiver Reduced Dimensional STAP Method for an Airborne MIMO Radar

    Directory of Open Access Journals (Sweden)

    Guo Yiduo

    2016-10-01

    Full Text Available The unified theoretical frame of a joint transmitter-receiver reduced dimensional Space-Time Adaptive Processing (STAP method is studied for an airborne Multiple-Input Multiple-Output (MIMO radar. First, based on the transmitted waveform diverse characteristics of the transmitted waveform of the airborne MIMO radar, a uniform theoretical frame structure for the reduced dimensional joint adaptive STAP is constructed. Based on it, three reduced dimensional STAP fixed structures are established. Finally, three reduced rank STAP algorithms, which are suitable for a MIMO system, are presented corresponding to the three reduced dimensional STAP fixed structures. The simulations indicate that the joint adaptive algorithms have preferable clutter suppression and anti-interference performance.

  15. The Complexity of Background Clutter Affects Nectar Bat Use of Flower Odor and Shape Cues.

    Directory of Open Access Journals (Sweden)

    Nathan Muchhala

    Full Text Available Given their small size and high metabolism, nectar bats need to be able to quickly locate flowers during foraging bouts. Chiropterophilous plants depend on these bats for their reproduction, thus they also benefit if their flowers can be easily located, and we would expect that floral traits such as odor and shape have evolved to maximize detection by bats. However, relatively little is known about the importance of different floral cues during foraging bouts. In the present study, we undertook a set of flight cage experiments with two species of nectar bats (Anoura caudifer and A. geoffroyi and artificial flowers to compare the importance of shape and scent cues in locating flowers. In a training phase, a bat was presented an artificial flower with a given shape and scent, whose position was constantly shifted to prevent reliance on spatial memory. In the experimental phase, two flowers were presented, one with the training-flower scent and one with the training-flower shape. For each experimental repetition, we recorded which flower was located first, and then shifted flower positions. Additionally, experiments were repeated in a simple environment, without background clutter, or a complex environment, with a background of leaves and branches. Results demonstrate that bats visit either flower indiscriminately with simple backgrounds, with no significant difference in terms of whether they visit the training-flower odor or training-flower shape first. However, in a complex background olfaction was the most important cue; scented flowers were consistently located first. This suggests that for well-exposed flowers, without obstruction from clutter, vision and/or echolocation are sufficient in locating them. In more complex backgrounds, nectar bats depend more heavily on olfaction during foraging bouts.

  16. Path Planning for Non-Circular, Non-Holonomic Robots in Highly Cluttered Environments.

    Science.gov (United States)

    Samaniego, Ricardo; Lopez, Joaquin; Vazquez, Fernando

    2017-08-15

    This paper presents an algorithm for finding a solution to the problem of planning a feasible path for a slender autonomous mobile robot in a large and cluttered environment. The presented approach is based on performing a graph search on a kinodynamic-feasible lattice state space of high resolution; however, the technique is applicable to many search algorithms. With the purpose of allowing the algorithm to consider paths that take the robot through narrow passes and close to obstacles, high resolutions are used for the lattice space and the control set. This introduces new challenges because one of the most computationally expensive parts of path search based planning algorithms is calculating the cost of each one of the actions or steps that could potentially be part of the trajectory. The reason for this is that the evaluation of each one of these actions involves convolving the robot's footprint with a portion of a local map to evaluate the possibility of a collision, an operation that grows exponentially as the resolution is increased. The novel approach presented here reduces the need for these convolutions by using a set of offline precomputed maps that are updated, by means of a partial convolution, as new information arrives from sensors or other sources. Not only does this improve run-time performance, but it also provides support for dynamic search in changing environments. A set of alternative fast convolution methods are also proposed, depending on whether the environment is cluttered with obstacles or not. Finally, we provide both theoretical and experimental results from different experiments and applications.

  17. Netted LPI RADARs

    Science.gov (United States)

    2011-09-01

    CHALLENGES ............................66 1. Radar Processing Gain ........................66 2. High Sensitivity Requirement .................68 B...Relationship Between Network Space and Challenges .....................................127 Figure 42. Maneuverability................................129...virtually any kind of terrain. It has five modes: Normal, Weather, ECCM, LPI, and Very Low Clearance ( VLC ). Pictures of the LANTIRN pod aboard and F-16

  18. Detectability of underground electrical cables junction with a ground penetrating radar: electromagnetic simulation and experimental measurements

    Science.gov (United States)

    Liu, Xiang; serhir, mohammed; kameni, abelin; lambert, marc; pichon, lionel

    2016-04-01

    For a company like Electricity De France (EDF), being able to detect accurately using non-destructive methods the position of the buried junction between two underground cables is a crucial issue. The junction is the linking part where most maintenance operations are carried out. The challenge of this work is to conduct a feasibility study to confirm or deny the relevance of Ground Penetrating Radar (GPR) to detect these buried junctions in their actual environment against clutter. Indeed, the cables are buried in inhomogeneous medium at around 80cm deep. To do this, the study is conducted in a numerical environment. We use the 3D simulation software CST MWS to model a GPR scenario. In this simulation, we place the already optimized bowtie antennas operating in the frequency band [0.5 GHz - 3 GHz] in front of wet soil (dispersive) and dry soil where the underground cable is placed at 80cm deep. We collect the amplitude and phase of the reflected waves in order to detect the contrast provoked by the geometric dimensions variation of the cable [1] (diameter of the cable is 48mm and the diameter of the junction 74mm). The use of an ultra-wideband antenna is necessary to reconcile resolution and penetration of electromagnetic waves in the medium to be characterized. We focus on the performance of the GPR method according to the characteristics of the surrounding medium in which the electric cables are buried, the polarization of the Tx and Rx antennas. The experimental measurement collected in the EDF site will be presented. The measured data are processed using the clutter reduction method based on digital filtering [2]. We aim at showing that using the developed bowtie antennas that the GPR technique is well adapted for the cable junction localization even in cluttered environment. References [1] D. J. Daniels, "Surface-Penetrating Radar", London, IEE 1996. [2] Potin, D.; Duflos, E.; Vanheeghe, P., "Landmines Ground-Penetrating Radar Signal Enhancement by Digital

  19. Space radar image of Mauna Loa, Hawaii

    Science.gov (United States)

    1995-01-01

    This image of the Mauna Loa volcano on the Big Island of Hawaii shows the capability of imaging radar to map lava flows and other volcanic structures. Mauna Loa has erupted more than 35 times since the island was first visited by westerners in the early 1800s. The large summit crater, called Mokuaweoweo Caldera, is clearly visible near the center of the image. Leading away from the caldera (towards top right and lower center) are the two main rift zones shown here in orange. Rift zones are areas of weakness within the upper part of the volcano that are often ripped open as new magma (molten rock) approaches the surface at the start of an eruption. The most recent eruption of Mauna Loa was in March and April 1984, when segments of the northeast rift zones were active. If the height of the volcano was measured from its base on the ocean floor instead of from sea level, Mauna Loa would be the tallest mountain on Earth. Its peak (center of the image) rises more than 8 kilometers (5 miles) above the ocean floor. The South Kona District, known for cultivation of macadamia nuts and coffee, can be seen in the lower left as white and blue areas along the coast. North is toward the upper left. The area shown is 41.5 by 75 kilometers (25.7 by 46.5 miles), centered at 19.5 degrees north latitude and 155.6 degrees west longitude. The image was acquired by the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/ X-SAR) aboard the space shuttle Endeavour on its 36th orbit on October 2, 1994. The radar illumination is from the left of the image. The colors in this image were obtained using the following radar channels: red represents the L-band (horizontally transmitted and received); green represents the L-band (horizontally transmitted, vertically received); blue represents the C-band (horizontally transmitted, vertically received). The resulting color combinations in this radar image are caused by differences in surface roughness of the lava flows. Smoother flows

  20. Polarimetric C-Band SAR Observations of Sea Ice in the Greenland Sea

    DEFF Research Database (Denmark)

    Thomsen, Bjørn Bavnehøj; Nghiem, S.V.; Kwok, R.

    1998-01-01

    The fully polarimetric EMISAR acquired C-band radar signatures of sea ice in the Greenland Sea during a campaign in March 1995. The authors present maps of polarimetric signatures over an area containing various kinds of ice and discuss the use of polarimetric SAR for identification of ice types...

  1. Introducing Switching Ordered Statistic CFAR Type I in Different Radar Environments

    Directory of Open Access Journals (Sweden)

    Saeed Erfanian

    2009-01-01

    Full Text Available In this paper, a new CFAR detector based on a switching algorithm and OS-CFAR for nonhomogeneous background environments is introduced. The new detector is named Switching Ordered Statistic CFAR type I (SOS CFAR I. The SOS CFAR I selects a set of suitable cells and then with the help of the ordering method, estimates the unknown background noise level. The proposed detector does not require any prior information about the background environment and uses cells with similar statistical specifications to estimate the background noise. The performance of SOS CFAR I is evaluated and compared with other detectors such as CA-CFAR, GO-CFAR, SO-CFAR, and OS-CFAR for the Swerling I target model in homogeneous and nonhomogeneous noise environments such as those with multiple interference and clutter edges. The results show that SOS CFAR I detectors considerably reduce the problem of excessive false alarm probability near clutter edges while maintaining good performance in other environments. Also, simulation results confirm the achievement of an optimum detection threshold in homogenous and nonhomogeneous radar environments by the mentioned processor.

  2. Tsunami Arrival Detection with High Frequency (HF Radar

    Directory of Open Access Journals (Sweden)

    Donald Barrick

    2012-05-01

    Full Text Available Quantitative real-time observations of a tsunami have been limited to deep-water, pressure-sensor observations of changes in the sea surface elevation and observations of sea level fluctuations at the coast, which are essentially point measurements. Constrained by these data, models have been used for predictions and warning of the arrival of a tsunami, but to date no system exists for local detection of an actual incoming wave with a significant warning capability. Networks of coastal high frequency (HF-radars are now routinely observing surface currents in many countries. We report here on an empirical method for the detection of the initial arrival of a tsunami, and demonstrate its use with results from data measured by fourteen HF radar sites in Japan and USA following the magnitude 9.0 earthquake off Sendai, Japan, on 11 March 2011. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends on the bathymetry: the wider the shallow continental shelf, the greater this time. We compare arrival times at the radars with those measured by neighboring tide gauges. Arrival times measured by the radars preceded those at neighboring tide gauges by an average of 19 min (Japan and 15 min (USA The initial water-height increase due to the tsunami as measured by the tide gauges was moderate, ranging from 0.3 to 2 m. Thus it appears possible to detect even moderate tsunamis using this method. Larger tsunamis could obviously be detected further from the coast. We find that tsunami arrival within the radar coverage area can be announced 8 min (i.e., twice the radar spectral time resolution after its first appearance. This can provide advance warning of the tsunami approach to the coastline locations.

  3. A review of array radars

    Science.gov (United States)

    Brookner, E.

    1981-10-01

    Achievements in the area of array radars are illustrated by such activities as the operational deployment of the large high-power, high-range-resolution Cobra Dane; the operational deployment of two all-solid-state high-power, large UHF Pave Paws radars; and the development of the SAM multifunction Patriot radar. This paper reviews the following topics: array radars steered in azimuth and elevation by phase shifting (phase-phase steered arrays); arrays steered + or - 60 deg, limited scan arrays, hemispherical coverage, and omnidirectional coverage arrays; array radars steering electronically in only one dimension, either by frequency or by phase steering; and array radar antennas which use no electronic scanning but instead use array antennas for achieving low antenna sidelobes.

  4. FMWC Radar for Breath Detection

    DEFF Research Database (Denmark)

    Suhr, Lau Frejstrup; Tafur Monroy, Idelfonso; Vegas Olmos, Juan José

    We report on the experimental demonstration of an FMCW radar operating in the 25.7 - 26.6 GHz range with a repetition rate of 500 sweeps per second. The radar is able to track the breathing rate of an adult human from a distance of 1 meter. The experiments have utilized a 50 second recording window...... to accurately track the breathing rate. The radar utilizes a saw tooth modulation format and a low latency receiver. A breath tracking radar is useful both in medical scenarios, diagnosing disorders such as sleep apnea, and for home use where the user can monitor its health. Breathing is a central part of every...... radar chip which, through the use of a simple modulation scheme, is able to measure the breathing rate of an adult human from a distance. A high frequency output makes sure that the radar cannot penetrate solid obstacles which is a wanted feature in private homes where people therefore cannot measure...

  5. Basic study for tsunami detection with DBF ocean radar

    International Nuclear Information System (INIS)

    Sakai, Shin'ichi; Matsuyama, Masafumi; Okuda, Kouzou; Uehara, Fumihiro

    2015-01-01

    To develop early tsunami warning system utilizing ocean radars, the evaluation of the variety of measuring coverage and data accuracy is indispensable in real oceans. The field observation was carried out at 5 minutes interval with two digital beam forming ocean radars with VHF band from 2012 to 2014 in the sea of Enshu. The high data acquisition areas are found in the extent of 17 km off the coast on a hill site and of 13 km on a low ground site. The measured current by the ocean radar were well correlated with that by the current-meter in the depth of 2 m near the coast with the correlation coefficient of ∼0.6. It is inferred that the main factor of difference in both data sets was due to the presence of wind-driven current through the multi-regression analysis with both current data and wind data. In addition, the order of the temporal current deviations as to the representative time-scale of one hour is about 5 cm/s under the ordinary sea conditions, which suggest that ocean radars could sufficiently detect the current deviation due to grant tsunami. (author)

  6. Gaussian mixture probability hypothesis density filter for multipath multitarget tracking in over-the-horizon radar

    Science.gov (United States)

    Qin, Yong; Ma, Hong; Chen, Jinfeng; Cheng, Li

    2015-12-01

    Conventional multitarget tracking systems presume that each target can produce at most one measurement per scan. Due to the multiple ionospheric propagation paths in over-the-horizon radar (OTHR), this assumption is not valid. To solve this problem, this paper proposes a novel tracking algorithm based on the theory of finite set statistics (FISST) called the multipath probability hypothesis density (MP-PHD) filter in cluttered environments. First, the FISST is used to derive the update equation, and then Gaussian mixture (GM) is introduced to derive the closed-form solution of the MP-PHD filter. Moreover, the extended Kalman filter (EKF) is presented to deal with the nonlinear problem of the measurement model in OTHR. Eventually, the simulation results are provided to demonstrate the effectiveness of the proposed filter.

  7. Radar Image, Hokkaido, Japan

    Science.gov (United States)

    2000-01-01

    The southeast part of the island of Hokkaido, Japan, is an area dominated by volcanoes and volcanic caldera. The active Usu Volcano is at the lower right edge of the circular Lake Toya-Ko and near the center of the image. The prominent cone above and to the left of the lake is Yotei Volcano with its summit crater. The city of Sapporo lies at the base of the mountains at the top of the image and the town of Yoichi -- the hometown of SRTM astronaut Mamoru Mohri -- is at the upper left edge. The bay of Uchiura-Wan takes up the lower center of the image. In this image, color represents elevation, from blue at the lowest elevations to white at the highest. The radar image has been overlaid to provide more details of the terrain. Due to a processing problem, an island in the center of this crater lake is missing and will be properly placed when further SRTM swaths are processed. The horizontal banding in this image is a processing artifact that will be removed when the navigation information collected by SRTM is fully calibrated. This image was acquired by the Shuttle Radar Topography Mission (SRTM) aboard the Space Shuttle Endeavour, launched on February 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect three-dimensional measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter-long (200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between the National Aeronautics and Space Administration (NASA), the National Imagery and Mapping Agency (NIMA) of the U.S. Department of Defense (DoD), and the German and Italian space agencies. It is managed by NASA's Jet Propulsion Laboratory, Pasadena, CA, for NASA's Earth Science Enterprise, Washington, DC. Size: 100 by 150 kilometers (62

  8. Satellite-Surface Perspectives of Air Quality and Aerosol-Cloud Effects on the Environment: An Overview of 7-SEAS BASELInE

    Science.gov (United States)

    Tsay, Si-Chee; Maring, Hal B.; Lin, Neng-Huei; Buntoung, Sumaman; Chantara, Somporn; Chuang, Hsiao-Chi; Gabriel, Philip M.; Goodloe, Colby S.; Holben, Brent N.; Hsiao, Ta-Chih; hide

    2016-01-01

    The objectives of 7-SEASBASELInE (Seven SouthEast Asian Studies Biomass-burning Aerosols and Stratocumulus Environment: Lifecycles and Interactions Experiment) campaigns in spring 2013-2015 were to synergize measurements from uniquely distributed ground-based networks (e.g., AERONET (AErosol RObotic NETwork)), MPLNET ( NASA Micro-Pulse Lidar Network)) and sophisticated platforms (e.g.,SMARTLabs (Surface-based Mobile Atmospheric Research and Testbed Laboratories), regional contributing instruments), along with satellite observations retrievals and regional atmospheric transport chemical models to establish a critically needed database, and to advance our understanding of biomass-burning aerosols and trace gases in Southeast Asia (SEA). We present a satellite-surface perspective of 7-SEASBASELInE and highlight scientific findings concerning: (1) regional meteorology of moisture fields conducive to the production and maintenance of low-level stratiform clouds over land; (2) atmospheric composition in a biomass-burning environment, particularly tracers-markers to serve as important indicators for assessing the state and evolution of atmospheric constituents; (3) applications of remote sensing to air quality and impact on radiative energetics, examining the effect of diurnal variability of boundary-layer height on aerosol loading; (4) aerosol hygroscopicity and ground-based cloud radar measurements in aerosol-cloud processes by advanced cloud ensemble models; and (5) implications of air quality, in terms of toxicity of nanoparticles and trace gases, to human health. This volume is the third 7-SEAS special issue (after Atmospheric Research, vol. 122, 2013; and Atmospheric Environment, vol. 78, 2013) and includes 27 papers published, with emphasis on air quality and aerosol-cloud effects on the environment. BASELInE observations of stratiform clouds over SEA are unique, such clouds are embedded in a heavy aerosol-laden environment and feature characteristically greater

  9. Radar techniques using array antennas

    CERN Document Server

    Wirth, Wulf-Dieter

    2013-01-01

    Radar Techniques Using Array Antennas is a thorough introduction to the possibilities of radar technology based on electronic steerable and active array antennas. Topics covered include array signal processing, array calibration, adaptive digital beamforming, adaptive monopulse, superresolution, pulse compression, sequential detection, target detection with long pulse series, space-time adaptive processing (STAP), moving target detection using synthetic aperture radar (SAR), target imaging, energy management and system parameter relations. The discussed methods are confirmed by simulation stud

  10. Expertise Effects in Face-Selective Areas are Robust to Clutter and Diverted Attention, but not to Competition.

    Science.gov (United States)

    McGugin, Rankin Williams; Van Gulick, Ana E; Tamber-Rosenau, Benjamin J; Ross, David A; Gauthier, Isabel

    2015-09-01

    Expertise effects for nonface objects in face-selective brain areas may reflect stable aspects of neuronal selectivity that determine how observers perceive objects. However, bottom-up (e.g., clutter from irrelevant objects) and top-down manipulations (e.g., attentional selection) can influence activity, affecting the link between category selectivity and individual performance. We test the prediction that individual differences expressed as neural expertise effects for cars in face-selective areas are sufficiently stable to survive clutter and manipulations of attention. Additionally, behavioral work and work using event related potentials suggest that expertise effects may not survive competition; we investigate this using functional magnetic resonance imaging. Subjects varying in expertise with cars made 1-back decisions about cars, faces, and objects in displays containing one or 2 objects, with only one category attended. Univariate analyses suggest car expertise effects are robust to clutter, dampened by reducing attention to cars, but nonetheless more robust to manipulations of attention than competition. While univariate expertise effects are severely abolished by competition between cars and faces, multivariate analyses reveal new information related to car expertise. These results demonstrate that signals in face-selective areas predict expertise effects for nonface objects in a variety of conditions, although individual differences may be expressed in different dependent measures depending on task and instructions. © The Author 2014. Published by Oxford University Press. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

  11. Object Extraction in Cluttered Environments via a P300-Based IFCE

    Directory of Open Access Journals (Sweden)

    Xiaoqian Mao

    2017-01-01

    Full Text Available One of the fundamental issues for robot navigation is to extract an object of interest from an image. The biggest challenges for extracting objects of interest are how to use a machine to model the objects in which a human is interested and extract them quickly and reliably under varying illumination conditions. This article develops a novel method for segmenting an object of interest in a cluttered environment by combining a P300-based brain computer interface (BCI and an improved fuzzy color extractor (IFCE. The induced P300 potential identifies the corresponding region of interest and obtains the target of interest for the IFCE. The classification results not only represent the human mind but also deliver the associated seed pixel and fuzzy parameters to extract the specific objects in which the human is interested. Then, the IFCE is used to extract the corresponding objects. The results show that the IFCE delivers better performance than the BP network or the traditional FCE. The use of a P300-based IFCE provides a reliable solution for assisting a computer in identifying an object of interest within images taken under varying illumination intensities.

  12. Clutter-free Visualization of Large Point Symbols at Multiple Scales by Offset Quadtrees

    Directory of Open Access Journals (Sweden)

    ZHANG Xiang

    2016-08-01

    Full Text Available To address the cartographic problems in map mash-up applications in the Web 2.0 context, this paper studies a clutter-free technique for visualizing large symbols on Web maps. Basically, a quadtree is used to select one symbol in each grid cell at each zoom level. To resolve the symbol overlaps between neighboring quad-grids, multiple offsets are applied to the quadtree and a voting strategy is used to compute the significant level of symbols for their selection at multiple scales. The method is able to resolve spatial conflicts without explicit conflict detection, thus enabling a highly efficient processing. Also the resulting map forms a visual hierarchy of semantic importance. We discuss issues such as the relative importance, symbol-to-grid size ratio, and effective offset schemes, and propose two extensions to make better use of the free space available on the map. Experiments were carried out to validate the technique,which demonstrates its robustness and efficiency (a non-optimal implementation leads to a sub-second processing for datasets of a 105 magnitude.

  13. Three-dimensional model-based object recognition and segmentation in cluttered scenes.

    Science.gov (United States)

    Mian, Ajmal S; Bennamoun, Mohammed; Owens, Robyn

    2006-10-01

    Viewpoint independent recognition of free-form objects and their segmentation in the presence of clutter and occlusions is a challenging task. We present a novel 3D model-based algorithm which performs this task automatically and efficiently. A 3D model of an object is automatically constructed offline from its multiple unordered range images (views). These views are converted into multidimensional table representations (which we refer to as tensors). Correspondences are automatically established between these views by simultaneously matching the tensors of a view with those of the remaining views using a hash table-based voting scheme. This results in a graph of relative transformations used to register the views before they are integrated into a seamless 3D model. These models and their tensor representations constitute the model library. During online recognition, a tensor from the scene is simultaneously matched with those in the library by casting votes. Similarity measures are calculated for the model tensors which receive the most votes. The model with the highest similarity is transformed to the scene and, if it aligns accurately with an object in the scene, that object is declared as recognized and is segmented. This process is repeated until the scene is completely segmented. Experiments were performed on real and synthetic data comprised of 55 models and 610 scenes and an overall recognition rate of 95 percent was achieved. Comparison with the spin images revealed that our algorithm is superior in terms of recognition rate and efficiency.

  14. Reinforcement Learning with Autonomous Small Unmanned Aerial Vehicles in Cluttered Environments

    Science.gov (United States)

    Tran, Loc; Cross, Charles; Montague, Gilbert; Motter, Mark; Neilan, James; Qualls, Garry; Rothhaar, Paul; Trujillo, Anna; Allen, B. Danette

    2015-01-01

    We present ongoing work in the Autonomy Incubator at NASA Langley Research Center (LaRC) exploring the efficacy of a data set aggregation approach to reinforcement learning for small unmanned aerial vehicle (sUAV) flight in dense and cluttered environments with reactive obstacle avoidance. The goal is to learn an autonomous flight model using training experiences from a human piloting a sUAV around static obstacles. The training approach uses video data from a forward-facing camera that records the human pilot's flight. Various computer vision based features are extracted from the video relating to edge and gradient information. The recorded human-controlled inputs are used to train an autonomous control model that correlates the extracted feature vector to a yaw command. As part of the reinforcement learning approach, the autonomous control model is iteratively updated with feedback from a human agent who corrects undesired model output. This data driven approach to autonomous obstacle avoidance is explored for simulated forest environments furthering autonomous flight under the tree canopy research. This enables flight in previously inaccessible environments which are of interest to NASA researchers in Earth and Atmospheric sciences.

  15. A Low-Complexity Algorithm for Static Background Estimation from Cluttered Image Sequences in Surveillance Contexts

    Directory of Open Access Journals (Sweden)

    Reddy Vikas

    2011-01-01

    Full Text Available Abstract For the purposes of foreground estimation, the true background model is unavailable in many practical circumstances and needs to be estimated from cluttered image sequences. We propose a sequential technique for static background estimation in such conditions, with low computational and memory requirements. Image sequences are analysed on a block-by-block basis. For each block location a representative set is maintained which contains distinct blocks obtained along its temporal line. The background estimation is carried out in a Markov Random Field framework, where the optimal labelling solution is computed using iterated conditional modes. The clique potentials are computed based on the combined frequency response of the candidate block and its neighbourhood. It is assumed that the most appropriate block results in the smoothest response, indirectly enforcing the spatial continuity of structures within a scene. Experiments on real-life surveillance videos demonstrate that the proposed method obtains considerably better background estimates (both qualitatively and quantitatively than median filtering and the recently proposed "intervals of stable intensity" method. Further experiments on the Wallflower dataset suggest that the combination of the proposed method with a foreground segmentation algorithm results in improved foreground segmentation.

  16. Audio-visual speech timing sensitivity is enhanced in cluttered conditions.

    Directory of Open Access Journals (Sweden)

    Warrick Roseboom

    2011-04-01

    Full Text Available Events encoded in separate sensory modalities, such as audition and vision, can seem to be synchronous across a relatively broad range of physical timing differences. This may suggest that the precision of audio-visual timing judgments is inherently poor. Here we show that this is not necessarily true. We contrast timing sensitivity for isolated streams of audio and visual speech, and for streams of audio and visual speech accompanied by additional, temporally offset, visual speech streams. We find that the precision with which synchronous streams of audio and visual speech are identified is enhanced by the presence of additional streams of asynchronous visual speech. Our data suggest that timing perception is shaped by selective grouping processes, which can result in enhanced precision in temporally cluttered environments. The imprecision suggested by previous studies might therefore be a consequence of examining isolated pairs of audio and visual events. We argue that when an isolated pair of cross-modal events is presented, they tend to group perceptually and to seem synchronous as a consequence. We have revealed greater precision by providing multiple visual signals, possibly allowing a single auditory speech stream to group selectively with the most synchronous visual candidate. The grouping processes we have identified might be important in daily life, such as when we attempt to follow a conversation in a crowded room.

  17. Surface Current Measurements In Terra Nova Bay By Hf Radar

    Science.gov (United States)

    Flocco, D.; Falco, P.; Wadhams, P.; Spezie, G.

    We present the preliminary results of a field experiment carried out within frame- work of the CLIMA project of the Italian National Programme for Antarctic Research (PNRA) and in cooperation with the Scott Polar Research Institute of Cambridge. Dur- ing the second period (02/12/1999-23/01/2000) of the XV Italian expedition a coastal radar was used to characterize the current field in the area of Terra Nova Bay (TNB). One of the aims of the CLIMA (Climatic Long-term Interactions for the Mass balance in Antarctica) project is to determine the role of the polynya in the sea ice mass bal- ance, water structure and local climate. The OSCR-II experiment was planned in order to provide surface current measurements in the area of TNB polynya, one of the most important coastal polynya of the Ross Sea. OSCR (Ocean Surface Current Radar) is a shore based, remote sensing system designed to measure sea surface currents in coastal waters. Two radar sites (a master and a slave) provide with radial current mea- surements; data combined from both sites yield the total current vector. Unfortunately the master and slave stations did not work together throughout the whole period of the experiment. A description of the experiment and a discussion of the results, will be proposed.

  18. Analysis of sea-surface radar signatures by means of wavelet-based edge detection and detection of regularities; Analyse von Radarsignaturen der Meeresoberflaeche mittels auf Wavelets basierender Kantenerkennung und Regularitaetsbestimmung

    Energy Technology Data Exchange (ETDEWEB)

    Wolff, U. [GKSS-Forschungszentrum Geesthacht GmbH (Germany). Inst. fuer Gewaesserphysik

    2000-07-01

    The derivation and implementation of an algorithm for edge detection in images and for the detection of the Lipschitz regularity in edge points are described. The method is based on the use of the wavelet transform for edge detection at different resolutions. The Lipschitz regularity is a measure that characterizes the edges. The description of the derivation is first performed in one dimension. The approach of Mallat is formulated consistently and proved. Subsequently, the two-dimensional case is addressed, for which the derivation, as well as the description of the algorithm, is analogous. The algorithm is applied to detect edges in nautical radar images using images collected at the island of Sylt. The edges discernible in the images and the Lipschitz values provide information about the position and nature of spatial variations in the depth of the seafloor. By comparing images from different periods of measurement, temporal changes in the bottom structures can be localized at different resolutions and interpreted. The method is suited to the monitoring of coastal areas. It is an inexpensive way to observe long-term changes in the seafloor character. Thus, the results of this technique may be used by the authorities responsible for coastal protection to decide whether measures should be taken or not. (orig.)

  19. Broadview Radar Altimetry Toolbox

    Science.gov (United States)

    Garcia-Mondejar, Albert; Escolà, Roger; Moyano, Gorka; Roca, Mònica; Terra-Homem, Miguel; Friaças, Ana; Martinho, Fernando; Schrama, Ernst; Naeije, Marc; Ambrózio, Américo; Restano, Marco; Benveniste, Jérôme

    2017-04-01

    The universal altimetry toolbox, BRAT (Broadview Radar Altimetry Toolbox) which can read all previous and current altimetry missions' data, incorporates now the capability to read the upcoming Sentinel3 L1 and L2 products. ESA endeavoured to develop and supply this capability to support the users of the future Sentinel3 SAR Altimetry Mission. BRAT is a collection of tools and tutorial documents designed to facilitate the processing of radar altimetry data. This project started in 2005 from the joint efforts of ESA (European Space Agency) and CNES (Centre National d'Etudes Spatiales), and it is freely available at http://earth.esa.int/brat. The tools enable users to interact with the most common altimetry data formats. The BratGUI is the frontend for the powerful command line tools that are part of the BRAT suite. BRAT can also be used in conjunction with MATLAB/IDL (via reading routines) or in C/C++/Fortran via a programming API, allowing the user to obtain desired data, bypassing the dataformatting hassle. BRAT can be used simply to visualise data quickly, or to translate the data into other formats such as NetCDF, ASCII text files, KML (Google Earth) and raster images (JPEG, PNG, etc.). Several kinds of computations can be done within BRAT involving combinations of data fields that the user can save for posterior reuse or using the already embedded formulas that include the standard oceanographic altimetry formulas. The Radar Altimeter Tutorial, that contains a strong introduction to altimetry, shows its applications in different fields such as Oceanography, Cryosphere, Geodesy, Hydrology among others. Included are also "use cases", with step-by-step examples, on how to use the toolbox in the different contexts. The Sentinel3 SAR Altimetry Toolbox shall benefit from the current BRAT version. While developing the toolbox we will revamp of the Graphical User Interface and provide, among other enhancements, support for reading the upcoming S3 datasets and specific

  20. Doppler radar flowmeter

    Science.gov (United States)

    Petlevich, Walter J.; Sverdrup, Edward F.

    1978-01-01

    A Doppler radar flowmeter comprises a transceiver which produces an audio frequency output related to the Doppler shift in frequency between radio waves backscattered from particulate matter carried in a fluid and the radiated radio waves. A variable gain amplifier and low pass filter are provided for amplifying and filtering the transceiver output. A frequency counter having a variable triggering level is also provided to determine the magnitude of the Doppler shift. A calibration method is disclosed wherein the amplifier gain and frequency counter trigger level are adjusted to achieve plateaus in the output of the frequency counter and thereby allow calibration without the necessity of being able to visually observe the flow.

  1. Imaging with Synthetic Aperture Radar

    CERN Document Server

    Massonnet, Didier

    2008-01-01

    Describing a field that has been transformed by the recent availability of data from a new generation of space and airborne systems, the authors offer a synthetic geometrical approach to the description of synthetic aperture radar, one that addresses physicists, radar specialists, as well as experts in image processing.  

  2. Terahertz radar cross section measurements

    DEFF Research Database (Denmark)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-01-01

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar...

  3. Performance indicators modern surveillance radar

    NARCIS (Netherlands)

    Nooij, P.N.C.; Theil, A.

    2014-01-01

    Blake chart computations are widely employed to rank detection coverage capabilities of competitive search radar systems. Developed for comparable 2D radar systems with a mechanically rotating reflector antenna, it was not necessary to regard update rate and plot quality in Blake's chart. To

  4. On the radar cross section (RCS) prediction of vehicles moving on the ground

    International Nuclear Information System (INIS)

    Sabihi, Ahmad

    2014-01-01

    As readers should be aware, Radar Cross Section depends on the factors such as: Wave frequency and polarization, Target dimension, angle of ray incidence, Target’s material and covering, Type of radar system as monostatic or bistatic, space in which contains target and propagating waves, and etc. Having moved or stationed in vehicles can be effective in RCS values. Here, we investigate effective factors in RCS of moving targets on the ground or sea. Image theory in electromagnetic applies to be taken into account RCS of a target over the ground or sea

  5. On the radar cross section (RCS) prediction of vehicles moving on the ground

    Energy Technology Data Exchange (ETDEWEB)

    Sabihi, Ahmad [Department of Mathematical Sciences, Sharif University of Technology, Tehran (Iran, Islamic Republic of)

    2014-12-10

    As readers should be aware, Radar Cross Section depends on the factors such as: Wave frequency and polarization, Target dimension, angle of ray incidence, Target’s material and covering, Type of radar system as monostatic or bistatic, space in which contains target and propagating waves, and etc. Having moved or stationed in vehicles can be effective in RCS values. Here, we investigate effective factors in RCS of moving targets on the ground or sea. Image theory in electromagnetic applies to be taken into account RCS of a target over the ground or sea.

  6. 100 years of radar

    CERN Document Server

    Galati, Gaspare

    2016-01-01

    This book offers fascinating insights into the key technical and scientific developments in the history of radar, from the first patent, taken out by Hülsmeyer in 1904, through to the present day. Landmark events are highlighted and fascinating insights provided into the exceptional people who made possible the progress in the field, including the scientists and technologists who worked independently and under strict secrecy in various countries across the world in the 1930s and the big businessmen who played an important role after World War II. The book encourages multiple levels of reading. The author is a leading radar researcher who is ideally placed to offer a technical/scientific perspective as well as a historical one. He has taken care to structure and write the book in such a way as to appeal to both non-specialists and experts. The book is not sponsored by any company or body, either formally or informally, and is therefore entirely unbiased. The text is enriched by approximately three hundred ima...

  7. Improved estimation of heavy rainfall by weather radar after reflectivity correction and accounting for raindrop size distribution variability

    Science.gov (United States)

    Hazenberg, Pieter; Leijnse, Hidde; Uijlenhoet, Remko

    2015-04-01

    Between 25 and 27 August 2010 a long-duration mesoscale convective system was observed above the Netherlands, locally giving rise to rainfall accumulations exceeding 150 mm. Correctly measuring the amount of precipitation during such an extreme event is important, both from a hydrological and meteorological perspective. Unfortunately, the operational weather radar measurements were affected by multiple sources of error and only 30% of the precipitation observed by rain gauges was estimated. Such an underestimation of heavy rainfall, albeit generally less strong than in this extreme case, is typical for operational weather radar in The Netherlands. In general weather radar measurement errors can be subdivided into two groups: (1) errors affecting the volumetric reflectivity measurements (e.g. ground clutter, radar calibration, vertical profile of reflectivity) and (2) errors resulting from variations in the raindrop size distribution that in turn result in incorrect rainfall intensity and attenuation estimates from observed reflectivity measurements. A stepwise procedure to correct for the first group of errors leads to large improvements in the quality of the estimated precipitation, increasing the radar rainfall accumulations to about 65% of those observed by gauges. To correct for the second group of errors, a coherent method is presented linking the parameters of the radar reflectivity-rain rate (Z-R) and radar reflectivity-specific attenuation (Z-k) relationships to the normalized drop size distribution (DSD). Two different procedures were applied. First, normalized DSD parameters for the whole event and for each precipitation type separately (convective, stratiform and undefined) were obtained using local disdrometer observations. Second, 10,000 randomly generated plausible normalized drop size distributions were used for rainfall estimation, to evaluate whether this Monte Carlo method would improve the quality of weather radar rainfall products. Using the

  8. Application of HF Radar in Hazard Management

    Directory of Open Access Journals (Sweden)

    Mal Heron

    2016-01-01

    Full Text Available A review is given of the impact that HF radars are having on the management of coastal hazards. Maps of surface currents can be produced every 10–20 minutes which, in real time, improve navigation safety in restricted areas commonly found near ports and harbours. The time sequence of surface current maps enables Lagrangian tracking of small parcels of surface water, which enables hazard mitigation in managing suspended sediments in dredging, in emergency situations where flotsam and other drifting items need to be found, and in pollution control. The surface current measurement capability is used to assist tsunami warnings as shown by the phased-array data from Chile following the Great Tohoku Earthquake in 2011. The newly launched Tsunami Warning Center in Oman includes a network of phased-array HF radars to provide real-time tsunami monitoring. Wind direction maps can be used to locate the position of cold fronts in the open ocean and to monitor the timing and strength of sea-breeze fronts in key locations.

  9. Enabling UAV Navigation with Sensor and Environmental Uncertainty in Cluttered and GPS-Denied Environments

    Directory of Open Access Journals (Sweden)

    Fernando Vanegas

    2016-05-01

    Full Text Available Unmanned Aerial Vehicles (UAV can navigate with low risk in obstacle-free environments using ground control stations that plan a series of GPS waypoints as a path to follow. This GPS waypoint navigation does however become dangerous in environments where the GPS signal is faulty or is only present in some places and when the airspace is filled with obstacles. UAV navigation then becomes challenging because the UAV uses other sensors, which in turn generate uncertainty about its localisation and motion systems, especially if the UAV is a low cost platform. Additional uncertainty affects the mission when the UAV goal location is only partially known and can only be discovered by exploring and detecting a target. This navigation problem is established in this research as a Partially-Observable Markov Decision Process (POMDP, so as to produce a policy that maps a set of motion commands to belief states and observations. The policy is calculated and updated on-line while flying with a newly-developed system for UAV Uncertainty-Based Navigation (UBNAV, to navigate in cluttered and GPS-denied environments using observations and executing motion commands instead of waypoints. Experimental results in both simulation and real flight tests show that the UAV finds a path on-line to a region where it can explore and detect a target without colliding with obstacles. UBNAV provides a new method and an enabling technology for scientists to implement and test UAV navigation missions with uncertainty where targets must be detected using on-line POMDP in real flight scenarios.

  10. Enabling UAV Navigation with Sensor and Environmental Uncertainty in Cluttered and GPS-Denied Environments.

    Science.gov (United States)

    Vanegas, Fernando; Gonzalez, Felipe

    2016-05-10

    Unmanned Aerial Vehicles (UAV) can navigate with low risk in obstacle-free environments using ground control stations that plan a series of GPS waypoints as a path to follow. This GPS waypoint navigation does however become dangerous in environments where the GPS signal is faulty or is only present in some places and when the airspace is filled with obstacles. UAV navigation then becomes challenging because the UAV uses other sensors, which in turn generate uncertainty about its localisation and motion systems, especially if the UAV is a low cost platform. Additional uncertainty affects the mission when the UAV goal location is only partially known and can only be discovered by exploring and detecting a target. This navigation problem is established in this research as a Partially-Observable Markov Decision Process (POMDP), so as to produce a policy that maps a set of motion commands to belief states and observations. The policy is calculated and updated on-line while flying with a newly-developed system for UAV Uncertainty-Based Navigation (UBNAV), to navigate in cluttered and GPS-denied environments using observations and executing motion commands instead of waypoints. Experimental results in both simulation and real flight tests show that the UAV finds a path on-line to a region where it can explore and detect a target without colliding with obstacles. UBNAV provides a new method and an enabling technology for scientists to implement and test UAV navigation missions with uncertainty where targets must be detected using on-line POMDP in real flight scenarios.

  11. The effects of size, clutter, and complexity on vanishing-point distances in visual imagery.

    Science.gov (United States)

    Hubbard, T L; Baird, J C

    1993-01-01

    The portrayal of vanishing-point distances in visual imagery was examined in six experiments. In all experiments, subjects formed visual images of squares, and the squares were to be oriented orthogonally to subjects' line of sight. The squares differed in their level of surface complexity, and were either undivided, divided into 4 equally sized smaller squares, or divided into 16 equally sized smaller squares. Squares also differed in stated referent size, and ranged from 3 in. to 128 ft along each side. After subjects had formed an image of a specified square, they transformed their image so that the square was portrayed to move away from them. Eventually, the imaged square was portrayed to be so far away that if it were any further away, it could not be identified. Subjects estimated the distance to the square that was portrayed in their image at that time, the vanishing-point distance, and the relationship between stated referent size and imaged vanishing-point distance was best described by a power function with an exponent less than 1. In general, there were trends for exponents (slopes on log axes) to increase slightly and for multiplicative constants (y intercepts on log axes) to decrease as surface complexity increased. No differences in exponents or in multiplicative constants were found when the vanishing-point was approached from either subthreshold or suprathreshold directions. When clutter in the form of additional imaged objects located to either side of the primary imaged object was added to the image, the exponent of the vanishing-point function increased slightly and the multiplicative constant decreased. The success of a power function (and the failure of the size-distance invariance hypothesis) in describing the vanishing-point distance function calls into question the notions (a) that a constant grain size exists in the imaginal visual field at a given location and (b) that grain size specifies a lower limit in the storage of information in

  12. POLCAL - POLARIMETRIC RADAR CALIBRATION

    Science.gov (United States)

    Vanzyl, J.

    1994-01-01

    Calibration of polarimetric radar systems is a field of research in which great progress has been made over the last few years. POLCAL (Polarimetric Radar Calibration) is a software tool intended to assist in the calibration of Synthetic Aperture Radar (SAR) systems. In particular, POLCAL calibrates Stokes matrix format data produced as the standard product by the NASA/Jet Propulsion Laboratory (JPL) airborne imaging synthetic aperture radar (AIRSAR). POLCAL was designed to be used in conjunction with data collected by the NASA/JPL AIRSAR system. AIRSAR is a multifrequency (6 cm, 24 cm, and 68 cm wavelength), fully polarimetric SAR system which produces 12 x 12 km imagery at 10 m resolution. AIRSTAR was designed as a testbed for NASA's Spaceborne Imaging Radar program. While the images produced after 1991 are thought to be calibrated (phase calibrated, cross-talk removed, channel imbalance removed, and absolutely calibrated), POLCAL can and should still be used to check the accuracy of the calibration and to correct it if necessary. Version 4.0 of POLCAL is an upgrade of POLCAL version 2.0 released to AIRSAR investigators in June, 1990. New options in version 4.0 include automatic absolute calibration of 89/90 data, distributed target analysis, calibration of nearby scenes with calibration parameters from a scene with corner reflectors, altitude or roll angle corrections, and calibration of errors introduced by known topography. Many sources of error can lead to false conclusions about the nature of scatterers on the surface. Errors in the phase relationship between polarization channels result in incorrect synthesis of polarization states. Cross-talk, caused by imperfections in the radar antenna itself, can also lead to error. POLCAL reduces cross-talk and corrects phase calibration without the use of ground calibration equipment. Removing the antenna patterns during SAR processing also forms a very important part of the calibration of SAR data. Errors in the

  13. Flood Monitoring using X-band Dual-polarization Radar Network

    Science.gov (United States)

    Chandrasekar, V.; Wang, Y.; Maki, M.; Nakane, K.

    2009-09-01

    sensitivity and fast temporal update across the coverage. Strong clutter is expected from buildings in the neighborhood which act as perfect reflectors. The reduction in radar size enables flexible deployment, such as rooftop installation, with small infrastructure requirement, which is critical in a metropolitan region. Dual-polarization based technologies can be implemented for real-time mitigation of rain attenuations and accurate estimation of rainfall. The NSF Engineering Research Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) is developing the technologies and the systems for network centric weather observation. The Differential propagation phase (Kdp) has higher sensitivity at X-band compared to S and C band. It is attractive to use Kdp to derive Quantitative Precipitation Estimation (QPE) because it is immune to rain attenuation, calibration biases, partial beam blockage, and hail contamination. Despite the advantage of Kdp for radar QPE, the estimation of Kdp itself is a challenge as the range derivative of the differential propagation phase profiles. An adaptive Kdp algorithm was implemented in the CASA IP1 testbed that substantially reduces the fluctuation in light rain and the bias at heavy rain. The Kdp estimation also benefits from the higher resolution in the IP1 radar network. The performance of the IP1 QPE product was evaluated for all major rain events against the USDA Agriculture Research Service's gauge network (MicroNet) in the Little Washita watershed, which comprises 20 weather stations in the center of the test bed. The cross-comparison with gauge measurements shows excellent agreement for the storm events during the Spring Experiments of 2007 and 2008. The hourly rainfall estimates compared to the gauge measurements have a very small bias of few percent and a normalized standard error of 21%. The IP1 testbed was designed with overlapping coverage among its radar nodes. The study area is covered by multiple radars and the aspect of

  14. Statistical analysis and modelling of weather radar beam propagation conditions in the Po Valley (Italy

    Directory of Open Access Journals (Sweden)

    A. Fornasiero

    2006-01-01

    Full Text Available Ground clutter caused by anomalous propagation (anaprop can affect seriously radar rain rate estimates, particularly in fully automatic radar processing systems, and, if not filtered, can produce frequent false alarms. A statistical study of anomalous propagation detected from two operational C-band radars in the northern Italian region of Emilia Romagna is discussed, paying particular attention to its diurnal and seasonal variability. The analysis shows a high incidence of anaprop in summer, mainly in the morning and evening, due to the humid and hot summer climate of the Po Valley, particularly in the coastal zone. Thereafter, a comparison between different techniques and datasets to retrieve the vertical profile of the refractive index gradient in the boundary layer is also presented. In particular, their capability to detect anomalous propagation conditions is compared. Furthermore, beam path trajectories are simulated using a multilayer ray-tracing model and the influence of the propagation conditions on the beam trajectory and shape is examined. High resolution radiosounding data are identified as the best available dataset to reproduce accurately the local propagation conditions, while lower resolution standard TEMP data suffers from interpolation degradation and Numerical Weather Prediction model data (Lokal Model are able to retrieve a tendency to superrefraction but not to detect ducting conditions. Observing the ray tracing of the centre, lower and upper limits of the radar antenna 3-dB half-power main beam lobe it is concluded that ducting layers produce a change in the measured volume and in the power distribution that can lead to an additional error in the reflectivity estimate and, subsequently, in the estimated rainfall rate.

  15. Interception of LPI radar signals

    Science.gov (United States)

    Lee, Jim P.

    1991-11-01

    Most current radars are designed to transmit short duration pulses with relatively high peak power. These radars can be detected easily by the use of relatively modest EW intercept receivers. Three radar functions (search, anti-ship missile (ASM) seeker, and navigation) are examined to evaluate the effectiveness of potential low probability of intercept (LPI) techniques, such as waveform coding, antenna profile control, and power management that a radar may employ against current Electronic Warfare (EW) receivers. The general conclusion is that it is possible to design a LPI radar which is effective against current intercept EW receivers. LPI operation is most easily achieved at close ranges and against a target with a large radar cross section. The general system sensitivity requirement for the detection of current and projected LPI radars is found to be on the order of -100 dBmi which cannot be met by current EW receivers. Finally, three potential LPI receiver architectures, using channelized, superhet, and acousto-optic receivers with narrow RF and video bandwidths are discussed. They have shown some potential in terms of providing the sensitivity and capability in an environment where both conventional and LPI signals are present.

  16. Observation of snowfall with a low-power FM-CW K-band radar (Micro Rain Radar)

    Science.gov (United States)

    Kneifel, Stefan; Maahn, Maximilian; Peters, Gerhard; Simmer, Clemens

    2011-06-01

    Quantifying snowfall intensity especially under arctic conditions is a challenge because wind and snow drift deteriorate estimates obtained from both ground-based gauges and disdrometers. Ground-based remote sensing with active instruments might be a solution because they can measure well above drifting snow and do not suffer from flow distortions by the instrument. Clear disadvantages are, however, the dependency of e.g. radar returns on snow habit which might lead to similar large uncertainties. Moreover, high sensitivity radars are still far too costly to operate in a network and under harsh conditions. In this paper we compare returns from a low-cost, low-power vertically pointing FM-CW radar (Micro Rain Radar, MRR) operating at 24.1 GHz with returns from a 35.5 GHz cloud radar (MIRA36) for dry snowfall during a 6-month observation period at an Alpine station (Environmental Research Station Schneefernerhaus, UFS) at 2,650 m height above sea level. The goal was to quantify the potential and limitations of the MRR in relation to what is achievable by a cloud radar. The operational MRR procedures to derive standard radar variables like effective reflectivity factor ( Z e) or the mean Doppler velocity ( W) had to be modified for snowfall since the MRR was originally designed for rain observations. Since the radar returns from snowfall are weaker than from comparable rainfall, the behavior of the MRR close to its detection threshold has been analyzed and a method is proposed to quantify the noise level of the MRR based on clear sky observations. By converting the resulting MRR- Z e into 35.5 GHz equivalent Z e values, a remaining difference below 1 dBz with slightly higher values close to the noise threshold could be obtained. Due to the much higher sensitivity of MIRA36, the transition of the MRR from the true signal to noise can be observed, which agrees well with the independent clear sky noise estimate. The mean Doppler velocity differences between both radars

  17. Radar signal analysis and processing using Matlab

    CERN Document Server

    Mahafza, Bassem R

    2008-01-01

    Offering radar-related software for the analysis and design of radar waveform and signal processing, this book provides comprehensive coverage of radar signals and signal processing techniques and algorithms. It contains numerous graphical plots, common radar-related functions, table format outputs, and end-of-chapter problems. The complete set of MATLAB[registered] functions and routines are available for download online.

  18. Comparison of sea-ice freeboard distributions from aircraft data and cryosat-2

    DEFF Research Database (Denmark)

    Ricker, Robert; Hendricks, Stefan; Helm, Veit

    2012-01-01

    highly accurate range measurements. During the CryoSat Validation Experiment (CryoVEx) 2011 in the Lincoln Sea Cryosat-2 underpasses were accomplished with two aircraft which carried an airborne laser scanner, a radar altimeter and an electromagnetic induction device for direct sea ice thickness...... retrieval. Both aircraft flew in close formation at the same time of a CryoSat-2 overpass. This is a study about the comparison of the sea-ice freeboard distribution of laser scanner and radar altimeter measurements with the CryoSat-2 product within the multi-year sea ice region of the Lincoln Sea in spring...

  19. Radar observations of asteroids

    International Nuclear Information System (INIS)

    Ostro, S.J.

    1989-01-01

    This paper describes echoes from 33 main-belt asteroids (MBAs) and 19 near-Earth asteroids (NEAs) have provided a wealth of new information about these objects such as sizes, shapes, spin vectors, and such surface characteristics as decimeter-scale morphology, topographic relief, regolith porosity and metal concentrations. On average, small NEAs are much rougher at decimeter scales than MBAs, comets or terrestrial planets. Some of the largest MBAs (e.g., 1 Ceres and 2 Pallas ) are smoother than the moon at decimeter scales but much rougher than the Moon at some much larger scale. There is at least a five-fold variation in the radar albedos of MBAs, implying substantial variations in the surface porosities or metal concentrations of these objects. The highest MBA albedo estimate, for 16 Psyche, is consistent with a metal concentration near unity and lunar porosities

  20. Under the Radar

    CERN Document Server

    Goss, WM

    2010-01-01

    This is the biography of Ruby Payne-Scott (1912 to 1981). As the first female radio astronomer (and one of the first people in the world to consider radio astronomy), she made classic contributions to solar radio physics. She also played a major role in the design of the Australian government's Council for Scientific and Industrial Research radars, which were in turn of vital importance in the Southwest Pacific Theatre in World War II and were used by Australian, US and New Zealand personnel. From a sociological perspective, her career also offers many examples of the perils of being a female academic in the first half of the 20th century. Written in an engaging style and complemented by many historical photographs this book gives a fascinating insight into the beginning of radio astronomy and the role of a pioneering woman in astronomy.

  1. Material integrity verification radar

    International Nuclear Information System (INIS)

    Koppenjan, S.K.

    1999-01-01

    The International Atomic Energy Agency (IAEA) has the need for verification of 'as-built' spent fuel-dry storage containers and other concrete structures. The IAEA has tasked the Special Technologies Laboratory (STL) to fabricate, test, and deploy a stepped-frequency Material Integrity Verification Radar (MIVR) system to nondestructively verify the internal construction of these containers. The MIVR system is based on previously deployed high-frequency, ground penetrating radar (GPR) systems that have been developed by STL for the U.S. Department of Energy (DOE). Whereas GPR technology utilizes microwave radio frequency energy to create subsurface images, MTVR is a variation for which the medium is concrete instead of soil. The purpose is to nondestructively verify the placement of concrete-reinforcing materials, pipes, inner liners, and other attributes of the internal construction. The MIVR system underwent an initial field test on CANDU reactor spent fuel storage canisters at Atomic Energy of Canada Limited (AECL), Chalk River Laboratories, Ontario, Canada, in October 1995. A second field test at the Embalse Nuclear Power Plant in Embalse, Argentina, was completed in May 1996. The DOE GPR also was demonstrated at the site. Data collection and analysis were performed for the Argentine National Board of Nuclear Regulation (ENREN). IAEA and the Brazilian-Argentine Agency for the Control and Accounting of Nuclear Material (ABACC) personnel were present as observers during the test. Reinforcing materials were evident in the color, two-dimensional images produced by the MIVR system. A continuous pattern of reinforcing bars was evident and accurate estimates on the spacing, depth, and size were made. The potential uses for safeguard applications were jointly discussed. The MIVR system, as successfully demonstrated in the two field tests, can be used as a design verification tool for IAEA safeguards. A deployment of MIVR for Design Information Questionnaire (DIQ

  2. Air and spaceborne radar systems an introduction

    CERN Document Server

    Lacomme, Philippe; Hardange, Jean-Philippe; Normant, Eric

    2001-01-01

    A practical tool on radar systems that will be of major help to technicians, student engineers and engineers working in industry and in radar research and development. The many users of radar as well as systems engineers and designers will also find it highly useful. Also of interest to pilots and flight engineers and military command personnel and military contractors. """"This introduction to the field of radar is intended for actual users of radar. It focuses on the history, main principles, functions, modes, properties and specific nature of modern airborne radar. The book examines radar's

  3. Signal processing in noise waveform radar

    CERN Document Server

    Kulpa, Krzysztof

    2013-01-01

    This book is devoted to the emerging technology of noise waveform radar and its signal processing aspects. It is a new kind of radar, which use noise-like waveform to illuminate the target. The book includes an introduction to basic radar theory, starting from classical pulse radar, signal compression, and wave radar. The book then discusses the properties, difficulties and potential of noise radar systems, primarily for low-power and short-range civil applications. The contribution of modern signal processing techniques to making noise radar practical are emphasized, and application examples

  4. Introduction to radar target recognition

    CERN Document Server

    Tait, P

    2006-01-01

    This new text provides an overview of the radar target recognition process and covers the key techniques being developed for operational systems. It is based on the fundamental scientific principles of high resolution radar, and explains how the techniques can be used in real systems, taking into account the characteristics of practical radar system designs and component limitations. It also addresses operational aspects, such as how high resolution modes would fit in with other functions such as detection and tracking. Mathematics is kept to a minimum and the complex techniques and issues are

  5. Seasonal variations in active microwave signatures of sea ice in the Greenland Sea during 1992 and 1993

    DEFF Research Database (Denmark)

    Thomsen, Bjørn Bavnehøj; Skriver, Henning; Pedersen, Leif Toudal

    1995-01-01

    into the research of other statistical features of the sea ice than the mean value and also their seasonal variations. This paper investigates the backscatter coefficient and texture of different sea ice types and water by using calibrated precision images (PRI) acquired by the synthetic aperture radar (SAR...

  6. Active Listening in a Bat Cocktail Party: Adaptive Echolocation and Flight Behaviors of Big Brown Bats, Eptesicus fuscus, Foraging in a Cluttered Acoustic Environment.

    Science.gov (United States)

    Warnecke, Michaela; Chiu, Chen; Engelberg, Jonathan; Moss, Cynthia F

    2015-09-01

    In their natural environment, big brown bats forage for small insects in open spaces, as well as in vegetation and in the presence of acoustic clutter. While searching and hunting for prey, bats experience sonar interference, not only from densely cluttered environments, but also from calls of conspecifics foraging in close proximity. Previous work has shown that when two bats compete for a single prey item in a relatively open environment, one of the bats may go silent for extended periods of time, which can serve to minimize sonar interference between conspecifics. Additionally, pairs of big brown bats have been shown to adjust frequency characteristics of their vocalizations to avoid acoustic interference in echo processing. In this study, we extended previous work by examining how the presence of conspecifics and environmental clutter influence the bat's echolocation behavior. By recording multichannel audio and video data of bats engaged in insect capture in open and cluttered spaces, we quantified the bats' vocal and flight behaviors. Big brown bats flew individually and in pairs in an open and cluttered room, and the results of this study shed light on the different strategies that this species employs to negotiate a complex and dynamic environment. © 2015 S. Karger AG, Basel.

  7. Hyperspectral target detection analysis of a cluttered scene from a virtual airborne sensor platform using MuSES

    Science.gov (United States)

    Packard, Corey D.; Viola, Timothy S.; Klein, Mark D.

    2017-10-01

    The ability to predict spectral electro-optical (EO) signatures for various targets against realistic, cluttered backgrounds is paramount for rigorous signature evaluation. Knowledge of background and target signatures, including plumes, is essential for a variety of scientific and defense-related applications including contrast analysis, camouflage development, automatic target recognition (ATR) algorithm development and scene material classification. The capability to simulate any desired mission scenario with forecast or historical weather is a tremendous asset for defense agencies, serving as a complement to (or substitute for) target and background signature measurement campaigns. In this paper, a systematic process for the physical temperature and visible-through-infrared radiance prediction of several diverse targets in a cluttered natural environment scene is presented. The ability of a virtual airborne sensor platform to detect and differentiate targets from a cluttered background, from a variety of sensor perspectives and across numerous wavelengths in differing atmospheric conditions, is considered. The process described utilizes the thermal and radiance simulation software MuSES and provides a repeatable, accurate approach for analyzing wavelength-dependent background and target (including plume) signatures in multiple band-integrated wavebands (multispectral) or hyperspectrally. The engineering workflow required to combine 3D geometric descriptions, thermal material properties, natural weather boundary conditions, all modes of heat transfer and spectral surface properties is summarized. This procedure includes geometric scene creation, material and optical property attribution, and transient physical temperature prediction. Radiance renderings, based on ray-tracing and the Sandford-Robertson BRDF model, are coupled with MODTRAN for the inclusion of atmospheric effects. This virtual hyperspectral/multispectral radiance prediction methodology has been

  8. Japan Tsunami Current Flows Observed by HF Radars on Two Continents

    Directory of Open Access Journals (Sweden)

    Toshiyuki Awaji

    2011-08-01

    Full Text Available Quantitative real-time observations of a tsunami have been limited to deep-water, pressure-sensor observations of changes in the sea surface elevation and observations of sea level fluctuations at the coast, which are essentially point measurements. Constrained by these data, models have been used for predictions and warning of the arrival of a tsunami, but to date no detailed verification of flow patterns nor area measurements have been possible. Here we present unique HF-radar area observations of the tsunami signal seen in current velocities as the wave train approaches the coast. Networks of coastal HF-radars are now routinely observing surface currents in many countries and we report clear results from five HF radar sites spanning a distance of 8,200 km on two continents following the magnitude 9.0 earthquake off Sendai, Japan, on 11 March 2011. We confirm the tsunami signal with three different methodologies and compare the currents observed with coastal sea level fluctuations at tide gauges. The distance offshore at which the tsunami can be detected, and hence the warning time provided, depends on the bathymetry: the wider the shallow continental shelf, the greater this time. Data from these and other radars around the Pacific rim can be used to further develop radar as an important tool to aid in tsunami observation and warning as well as post-processing comparisons between observation and model predictions.

  9. Radar spectrum opportunities for cognitive communications transmission

    OpenAIRE

    Wang, L; McGeehan, JP; Williams, C; Doufexi, A

    2008-01-01

    In relation to opportunistic access to radar spectrum, the impact of the radar on a communication system is investigated in this paper. This paper illustrates that by exploring the spatial and temporal opportunities in the radar spectrum and therefore improving the tolerance level to radar interference, a substantial increase on the throughput of a communication system is possible. Results are presented regarding the impact of swept radars on a WiMAX system. The results show the impact of SIR...

  10. Exploring inner structure of Titan's dunes from Cassini Radar observations

    Science.gov (United States)

    Sharma, P.; Heggy, E.; Farr, T. G.

    2013-12-01

    Linear dunes discovered in the equatorial regions of Titan by the Cassini-Huygens mission are morphologically very similar to many terrestrial linear dune fields. These features have been compared with terrestrial longitudinal dune fields like the ones in Namib desert in western Africa. This comparison is based on the overall parallel orientation of Titan's dunes to the predominant wind direction on Titan, their superposition on other geomorphological features and the way they wrap around topographic obstacles. Studying the internal layering of dunes has strong implications in understanding the hypothesis for their origin and evolution. In Titan's case, although the morphology of the dunes has been studied from Cassini Synthetic Aperture Radar (SAR) images, it has not been possible to investigate their internal structure in detail as of yet. Since no radar sounding data is available for studying Titan's subsurface yet, we have developed another technique to examine the inner layering of the dunes. In this study, we utilize multiple complementary radar datasets, including radar imaging data for Titan's and Earth's dunes and Ground Penetrating Radar (GPR)/radar sounding data for terrestrial dunes. Based on dielectric mixing models, we suggest that the Cassini Ku-band microwaves should be able to penetrate up to ~ 3 m through Titan's dunes, indicating that the returned radar backscatter signal would include contributions from both surface and shallow subsurface echoes. This implies that the shallow subsurface properties can be retrieved from the observed radar backscatter (σ0). In our analysis, the variation of the radar backscatter as a function of dune height is used to provide an insight into the layering in Titan's dunes. We compare the variation of radar backscatter with elevation over individual dunes on Titan and analogous terrestrial dunes in three sites (Great Sand Sea, Siwa dunes and Qattaniya dunes) in the Egyptian Sahara. We observe a strong, positive

  11. Radar search and detection with the CASA 212 S43 aircraft

    OpenAIRE

    Landa Borges, José Manuel

    2004-01-01

    Approved for public release; distribution in unlimited. This research develops a detection rate model to analyze the effectiveness of the RDR 1500B search radar installed in the CASA 212 S43 aircraft belonging to Venezuelan Naval Aviation. The model is based on a search and detection mission to find a diesel submarine executing an incursion inside the Venezuelan Caribbean Sea area, assumed to be intermittently operating with periscopes or masts exposed above the sea surface. The analysis o...

  12. On the Design of Radar Corner Reflectors for Deformation Monitoring in Multi-Frequency InSAR

    Directory of Open Access Journals (Sweden)

    Matthew C. Garthwaite

    2017-06-01

    Full Text Available Trihedral corner reflectors are being increasingly used as point targets in deformation monitoring studies using interferometric synthetic aperture radar (InSAR techniques. The frequency and size dependence of the corner reflector Radar Cross Section (RCS means that no single design can perform equally in all the possible imaging modes and radar frequencies available on the currently orbiting Synthetic Aperture Radar (SAR satellites. Therefore, either a corner reflector design tailored to a specific data type or a compromise design for multiple data types is required. In this paper, I outline the practical and theoretical considerations that need to be made when designing appropriate radar targets, with a focus on supporting multi-frequency SAR data. These considerations are tested by performing field experiments on targets of different size using SAR images from TerraSAR-X, COSMO-SkyMed and RADARSAT-2. Phase noise behaviour in SAR images can be estimated by measuring the Signal-to-Clutter ratio (SCR in individual SAR images. The measured SCR of a point target is dependent on its RCS performance and the influence of clutter near to the deployed target. The SCR is used as a metric to estimate the expected InSAR displacement error incurred by the design of each target and to validate these observations against theoretical expectations. I find that triangular trihedral corner reflectors as small as 1 m in dimension can achieve a displacement error magnitude of a tenth of a millimetre or less in medium-resolution X-band data. Much larger corner reflectors (2.5 m or greater are required to achieve the same displacement error magnitude in medium-resolution C-band data. Compromise designs should aim to satisfy the requirements of the lowest SAR frequency to be used, providing that these targets will not saturate the sensor of the highest frequency to be used. Finally, accurate boresight alignment of the corner reflector can be critical to the overall

  13. Solid-state radar switchboard

    Science.gov (United States)

    Thiebaud, P.; Cross, D. C.

    1980-07-01

    A new solid-state radar switchboard equipped with 16 input ports which will output data to 16 displays is presented. Each of the ports will handle a single two-dimensional radar input, or three ports will accommodate a three-dimensional radar input. A video switch card of the switchboard is used to switch all signals, with the exception of the IFF-mode-control lines. Each card accepts inputs from up to 16 sources and can pass a signal with bandwidth greater than 20 MHz to the display assigned to that card. The synchro amplifier of current systems has been eliminated and in the new design each PPI receives radar data via a single coaxial cable. This significant reduction in cabling is achieved by adding a serial-to-parallel interface and a digital-to-synchro converter located at the PPI.

  14. SMAP RADAR Calibration and Validation

    Science.gov (United States)

    West, R. D.; Jaruwatanadilok, S.; Chaubel, M. J.; Spencer, M.; Chan, S. F.; Chen, C. W.; Fore, A.

    2015-12-01

    The Soil Moisture Active Passive (SMAP) mission launched on Jan 31, 2015. The mission employs L-band radar and radiometer measurements to estimate soil moisture with 4% volumetric accuracy at a resolution of 10 km, and freeze-thaw state at a resolution of 1-3 km. Immediately following launch, there was a three month instrument checkout period, followed by six months of level 1 (L1) calibration and validation. In this presentation, we will discuss the calibration and validation activities and results for the L1 radar data. Early SMAP radar data were used to check commanded timing parameters, and to work out issues in the low- and high-resolution radar processors. From April 3-13 the radar collected receive only mode data to conduct a survey of RFI sources. Analysis of the RFI environment led to a preferred operating frequency. The RFI survey data were also used to validate noise subtraction and scaling operations in the radar processors. Normal radar operations resumed on April 13. All radar data were examined closely for image quality and calibration issues which led to improvements in the radar data products for the beta release at the end of July. Radar data were used to determine and correct for small biases in the reported spacecraft attitude. Geo-location was validated against coastline positions and the known positions of corner reflectors. Residual errors at the time of the beta release are about 350 m. Intra-swath biases in the high-resolution backscatter images are reduced to less than 0.3 dB for all polarizations. Radiometric cross-calibration with Aquarius was performed using areas of the Amazon rain forest. Cross-calibration was also examined using ocean data from the low-resolution processor and comparing with the Aquarius wind model function. Using all a-priori calibration constants provided good results with co-polarized measurements matching to better than 1 dB, and cross-polarized measurements matching to about 1 dB in the beta release. During the

  15. Adaptive Radar Signal Processing-The Problem of Exponential Computational Cost

    National Research Council Canada - National Science Library

    Rangaswamy, Muralidhar

    2003-01-01

    .... Extensions to handle the case of non-Gaussian clutter statistics are presented. Current challenges of limited training data support, computational cost, and severely heterogeneous clutter backgrounds are outlined...

  16. Bistatic High Frequency Radar Ocean Surface Cross Section for an FMCW Source with an Antenna on a Floating Platform

    Directory of Open Access Journals (Sweden)

    Yue Ma

    2016-01-01

    Full Text Available The first- and second-order bistatic high frequency radar cross sections of the ocean surface with an antenna on a floating platform are derived for a frequency-modulated continuous wave (FMCW source. Based on previous work, the derivation begins with the general bistatic electric field in the frequency domain for the case of a floating antenna. Demodulation and range transformation are used to obtain the range information, distinguishing the process from that used for a pulsed radar. After Fourier-transforming the autocorrelation and comparing the result with the radar range equation, the radar cross sections are derived. The new first- and second-order antenna-motion-incorporated bistatic radar cross section models for an FMCW source are simulated and compared with those for a pulsed source. Results show that, for the same radar operating parameters, the first-order radar cross section for the FMCW waveform is a little lower than that for a pulsed source. The second-order radar cross section for the FMCW waveform reduces to that for the pulsed waveform when the scattering patch limit approaches infinity. The effect of platform motion on the radar cross sections for an FMCW waveform is investigated for a variety of sea states and operating frequencies and, in general, is found to be similar to that for a pulsed waveform.

  17. The NASA Polarimetric Radar (NPOL)

    Science.gov (United States)

    Petersen, Walter A.; Wolff, David B.

    2013-01-01

    Characteristics of the NASA NPOL S-band dual-polarimetric radar are presented including its operating characteristics, field configuration, scanning capabilities and calibration approaches. Examples of precipitation science data collections conducted using various scan types, and associated products, are presented for different convective system types and previous field campaign deployments. Finally, the NASA NPOL radar location is depicted in its home base configuration within the greater Wallops Flight Facility precipitation research array supporting NASA Global Precipitation Measurement Mission ground validation.

  18. European coordination for coastal HF radar data in EMODnet Physics

    Science.gov (United States)

    Mader, Julien; Novellino, Antonio; Gorringe, Patrick; Griffa, Annalisa; Schulz-Stellenfleth, Johannes; Montero, Pedro; Montovani, Carlo; Ayensa, Garbi; Vila, Begoña; Rubio, Anna; Sagarminaga, Yolanda

    2015-04-01

    Historically, joint effort has been put on observing open ocean, organizing, homogenizing, sharing and reinforcing the impact of the acquired information based on one technology: ARGO with profilers Argo floats, EuroSites, ESONET-NoE, FixO3 for deep water platforms, Ferrybox for stations in ships of opportunities, and GROOM for the more recent gliders. This kind of networking creates synergies and makes easier the implementation of this source of data in the European Data exchange services like EMODnet, ROOSs portals, or any applied services in the Blue economy. One main targeted improvement in the second phase of EMODnet projects is the assembling of data along coastline. In that sense, further coordination is recommended between platform operators around a specific technology in order to make easier the implementation of the data in the platforms (4th EuroGOOS DATAMEQ WG). HF radar is today recognized internationally as a cost-effective solution to provide high spatial and temporal resolution current maps (depending on the instrument operation frequency, covering from a few kilometres offshore up to 200 km) that are needed for many applications for issues related to ocean surface drift or sea state characterization. Significant heterogeneity still exists in Europe concerning technological configurations, data processing, quality standards and data availability. This makes more difficult the development of a significant network for achieving the needed accessibility to HF Radar data for a pan European use. EuroGOOS took the initiative to lead and coordinate activities within the various observation platforms by establishing a number of Ocean Observing Task Teams such as HF-Radars. The purpose is to coordinate and join the technological, scientific and operational HF radar communities at European level. The goal of the group is on the harmonization of systems requirements, systems design, data quality, improvement and proof of the readiness and standardization of

  19. Sparsity-Based Space-Time Adaptive Processing Using OFDM Radar

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Satyabrata [ORNL

    2012-01-01

    We propose a sparsity-based space-time adaptive processing (STAP) algorithm to detect a slowly-moving target using an orthogonal frequency division multiplexing (OFDM) radar. We observe that the target and interference spectra are inherently sparse in the spatio-temporal domain, and hence we exploit that sparsity to develop an efficient STAP technique. In addition, the use of an OFDM signal increases the frequency diversity of our system, as different scattering centers of a target resonate at different frequencies, and thus improves the target detectability. First, we formulate a realistic sparse-measurement model for an OFDM radar considering both the clutter and jammer as the interfering sources. Then, we show that the optimal STAP-filter weight-vector is equal to the generalized eigenvector corresponding to the minimum generalized eigenvalue of the interference and target covariance matrices. To estimate the target and interference covariance matrices, we apply a residual sparse-recovery technique that enables us to incorporate the partially known support of the sparse vector. Our numerical results demonstrate that the sparsity-based STAP algorithm, with considerably lesser number of secondary data, produces an equivalent performance as the other existing STAP techniques.

  20. OFDM Radar Space-Time Adaptive Processing by Exploiting Spatio-Temporal Sparsity

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Satyabrata [ORNL

    2013-01-01

    We propose a sparsity-based space-time adaptive processing (STAP) algorithm to detect a slowly-moving target using an orthogonal frequency division multiplexing (OFDM) radar. We observe that the target and interference spectra are inherently sparse in the spatio-temporal domain. Hence, we exploit that sparsity to develop an efficient STAP technique that utilizes considerably lesser number of secondary data and produces an equivalent performance as the other existing STAP techniques. In addition, the use of an OFDM signal increases the frequency diversity of our system, as different scattering centers of a target resonate at different frequencies, and thus improves the target detectability. First, we formulate a realistic sparse-measurement model for an OFDM radar considering both the clutter and jammer as the interfering sources. Then, we apply a residual sparse-recovery technique based on the LASSO estimator to estimate the target and interference covariance matrices, and subsequently compute the optimal STAP-filter weights. Our numerical results demonstrate a comparative performance analysis of the proposed sparse-STAP algorithm with four other existing STAP methods. Furthermore, we discover that the OFDM-STAP filter-weights are adaptable to the frequency-variabilities of the target and interference responses, in addition to the spatio-temporal variabilities. Hence, by better utilizing the frequency variabilities, we propose an adaptive OFDM-waveform design technique, and consequently gain a significant amount of STAP-performance improvement.

  1. Contribution of long-term accounting for raindrop size distribution variations on quantitative precipitation estimation by weather radar: Disdrometers vs parameter optimization

    Science.gov (United States)

    Hazenberg, P.; Uijlenhoet, R.; Leijnse, H.

    2015-12-01

    Volumetric weather radars provide information on the characteristics of precipitation at high spatial and temporal resolution. Unfortunately, rainfall measurements by radar are affected by multiple error sources, which can be subdivided into two main groups: 1) errors affecting the volumetric reflectivity measurements (e.g. ground clutter, vertical profile of reflectivity, attenuation, etc.), and 2) errors related to the conversion of the observed reflectivity (Z) values into rainfall intensity (R) and specific attenuation (k). Until the recent wide-scale implementation of dual-polarimetric radar, this second group of errors received relatively little attention, focusing predominantly on precipitation type-dependent Z-R and Z-k relations. The current work accounts for the impact of variations of the drop size distribution (DSD) on the radar QPE performance. We propose to link the parameters of the Z-R and Z-k relations directly to those of the normalized gamma DSD. The benefit of this procedure is that it reduces the number of unknown parameters. In this work, the DSD parameters are obtained using 1) surface observations from a Parsivel and Thies LPM disdrometer, and 2) a Monte Carlo optimization procedure using surface rain gauge observations. The impact of both approaches for a given precipitation type is assessed for 45 days of summertime precipitation observed within The Netherlands. Accounting for DSD variations using disdrometer observations leads to an improved radar QPE product as compared to applying climatological Z-R and Z-k relations. However, overall precipitation intensities are still underestimated. This underestimation is expected to result from unaccounted errors (e.g. transmitter calibration, erroneous identification of precipitation as clutter, overshooting and small-scale variability). In case the DSD parameters are optimized, the performance of the radar is further improved, resulting in the best performance of the radar QPE product. However

  2. Observing and Modelling the HighWater Level from Satellite Radar Altimetry During Tropical Cyclones

    DEFF Research Database (Denmark)

    Deng, Xiaoli; Gharineiat, Zahra; Andersen, Ole Baltazar

    2016-01-01

    This paper investigates the capability of observing tropical cyclones using satellite radar altimetry. Two representative cyclones Yasi (February 2011) and Larry (March 2006) in the northeast Australian coastal area are selected based also on available tide gauge sea level measurements. It is sho...

  3. Airborne Lidar and Radar Measurments In and Around Greenland CryoVEx 2006

    DEFF Research Database (Denmark)

    Stenseng, Lars; Hvidegaard, Sine Munk; Skourup, Henriette

    Air Greenland. The main purpose was to collect coincident ASIRAS and laser data at validation sites placed on land ice and sea ice in the Arctic area and offer logistic support to ground teams. The data collected will be important for the understanding of CryoSat-2 radar signals. A number...

  4. Investigation of image enhancement techniques for the development of a self-contained airborne radar navigation system

    Science.gov (United States)

    Phatak, A. V.; Karmali, M. S.

    1983-01-01

    This study was devoted to an investigation of the feasibility of applying advanced image processing techniques to enhance radar image characteristics that are pertinent to the pilot's navigation and guidance task. Millimeter (95 GHz) wave radar images for the overwater (i.e., offshore oil rigs) and overland (Heliport) scenario were used as a data base. The purpose of the study was to determine the applicability of image enhancement and scene analysis algorithms to detect and improve target characteristics (i.e., manmade objects such as buildings, parking lots, cars, roads, helicopters, towers, landing pads, etc.) that would be helpful to the pilot in determining his own position/orientation with respect to the outside world and assist him in the navigation task. Results of this study show that significant improvements in the raw radar image may be obtained using two dimensional image processing algorithms. In the overwater case, it is possible to remove the ocean clutter by thresholding the image data, and furthermore to extract the target boundary as well as the tower and catwalk locations using noise cleaning (e.g., median filter) and edge detection (e.g., Sobel operator) algorithms.

  5. wradlib - an Open Source Library for Weather Radar Data Processing

    Science.gov (United States)

    Pfaff, Thomas; Heistermann, Maik; Jacobi, Stephan

    2014-05-01

    Even though weather radar holds great promise for the hydrological sciences, offering precipitation estimates with unrivaled spatial and temporal resolution, there are still problems impeding its widespread use, among which are: almost every radar data set comes with a different data format with public reading software being available only rarely. standard products as issued by the meteorological services often do not serve the needs of original research, having either too many or too few corrections applied. Especially when new correction methods are to be developed, researchers are often forced to start from scratch having to implement many corrections in addition to those they are actually interested in. many algorithms published in the literature cannot be recreated using the corresponding article only. Public codes, providing insight into the actual implementation and how an approach deals with possible exceptions are rare. the radial scanning setup of weather radar measurements produces additional challenges, when it comes to visualization or georeferencing of this type of data. Based on these experiences, and in the hope to spare others at least some of these tedious tasks, wradlib offers the results of the author's own efforts and a growing number of community-supplied methods. wradlib is designed as a Python library of functions and classes to assist users in their analysis of weather radar data. It provides solutions for all tasks along a typical processing chain leading from raw reflectivity data to corrected, georeferenced and possibly gauge adjusted quantitative precipitation estimates. There are modules for data input/output, data transformation including Z/R transformation, clutter identification, attenuation correction, dual polarization and differential phase processing, interpolation, georeferencing, compositing, gauge adjustment, verification and visualization. The interpreted nature of the Python programming language makes wradlib an ideal tool

  6. Cassini RADAR at Titan : Results in 2013/2014

    Science.gov (United States)

    Lorenz, Ralph D.; Cassini RadarTeam

    2014-05-01

    Since the last EGU meeting, several Cassini flybys of Titan have featured significant RADAR observations. These include T91 and T92 (May/July 2013) with SAR and altimetry observations of Ligeia Mare. The latter have placed tight constraints on surface roughness (Zebker et al., in press), showing that wind-driven waves were not present. A remarkable altimetry analysis by Mastrogiuseppe et al. (submitted) detects a bottom echo from the bed of Ligeia, only possible if the liquid is exceptionally radar-transparent. This opens the way to wider radar bathymetry analyses of the northern seas. SAR coverage, augmented by some distant HiSAR observations, has now allowed construction of a more-or-less complete map of the northern polar region. This map now defines the extent of the northern lakes and seas, permitting oceanographic studies. T95 (October 2013) made SAR observations of the impact crater Selk (previously observed by VIMS and RADAR). As well as a closer view of this rather polygonal crater, the observation shows dramatic change in the dune orientation around the crater and its ejecta blanket. The T98 encounter is due to occur in February 2014, and will feature the last prime SAR observation of Ontario Lacus, giving a good baseline for change detection against prior observations. Additionally, close-approach observations (mandated to avoid solar heating constraints on other instruments) will give high-resolution altimetry data on the Shangri-La dunes. Preliminary results may be available in time for the meeting, at which this solicted talk will review analyses of these and other observations.

  7. Results from the search-lidar demonstrator project for detection of small Sea-Surface targets

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Putten, F.J.M. van; Cohen, L.H.; Kemp, R.A.W.; Franssen, G.C.

    2009-01-01

    Coastal surveillance and naval operations in the littoral both have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and a low velocity that makes them hard to detect by radar. Typical threats include jet skis, FIAC's, and speedboats. Previous lidar

  8. Search-Lidar Demonstrator for Detection of Small Sea-Surface Targets

    NARCIS (Netherlands)

    Heuvel, J.C. van den; Bekman, H.H.P.T.; Putten, F.J.M. van; Cohen, L.H.; Schleijpen, H.M.A.

    2008-01-01

    Coastal surveillance and naval operations in the littoral both have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and a low velocity that makes them hard to detect by radar. Typical threats include jet skis, FIAC’s, and speedboats. Lidar

  9. Synergetic Combination of Radar Information and Gauge Measurements - with the Conflict between Two Types of Data Being Removed via Displacement and Downscaling

    Science.gov (United States)

    Yan, J.; Bardossy, A.

    2017-12-01

    Rain gauges are the foundation in hydrology to collect rainfall data, however, gauge measurements alone are limited at representing the complete rainfall distribution. On the other hand, the reliability of radar data is often limited because of the errors in the radar signal (e.g. clutter, variation of the vertical reflectivity profile, beam blockage, attenuation, etc). Thus, merging radar information and gauge rainfall measurements is in an area of active research. The merging method proposed here is to use the radar data in its [0, 1] format (p-value). The actual precipitation values come from the gauge measurements. At each measurement location, two types of data are available, the radar p-value and the gauge measurement in mm. It happens very frequently that there exists a contradiction between these two types of data. A very likely reason is the influence of the unknown process between the radar measurement height and the surface onto which the hydrometeors fall. A method for quantification of the impact of the unknown process is proposed to fix the conflict, but only to a certain degree. Another possible source that can explain the discrepancy between these two types of data is discretization, i.e., the spatial variability cannot be identified by coarse discretization. Thus, downscaling is also considered to further remove the conflict. Based on the p-value from the radar data and the precipitation from the gauge measurements, a distribution function can be built up. The ultimate goal is to simulate the precipitation field for nowcasting purpose. The conditions to be fulfilled by the simulated field is as the following: honoring the measurements at the gauge locations; sharing a similar pattern with the radar image; preserving the inherent covariance structure. The simulation approach employed here is random mixing. The study domain is located in Reutlingen, Baden-Wuerttemberg, Germany (Latitude 48.49N, Longitude 9.20E). The radar data are obtained from a C

  10. Hurricane Rita Track Radar Image with Topographic Overlay

    Science.gov (United States)

    2005-01-01

    [figure removed for brevity, see original site] Animation About the animation: This simulated view of the potential effects of storm surge flooding on Galveston and portions of south Houston was generated with data from the Shuttle Radar Topography Mission. Although it is protected by a 17-foot sea wall against storm surges, flooding due to storm surges caused by major hurricanes remains a concern. The animation shows regions that, if unprotected, would be inundated with water. The animation depicts flooding in one-meter increments. About the image: The Gulf Coast from the Mississippi Delta through the Texas coast is shown in this satellite image from NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) overlain with data from the Shuttle Radar Topography Mission (SRTM), and the predicted storm track for Hurricane Rita. The prediction from the National Weather Service was published Sept. 22 at 4 p.m. Central Time, and shows the expected track center in black with the lighter shaded area indicating the range of potential tracks the storm could take. Low-lying terrain along the coast has been highlighted using the SRTM elevation data, with areas within 15 feet of sea level shown in red, and within 30 feet in yellow. These areas are more at risk for flooding and the destructive effects of storm surge and high waves. Data used in this image were acquired by the Shuttle Radar Topography Mission aboard the Space Shuttle Endeavour, launched on Feb. 11, 2000. SRTM used the same radar instrument that comprised the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) that flew twice on the Space Shuttle Endeavour in 1994. SRTM was designed to collect 3-D measurements of the Earth's surface. To collect the 3-D data, engineers added a 60-meter (approximately 200-foot) mast, installed additional C-band and X-band antennas, and improved tracking and navigation devices. The mission is a cooperative project between NASA, the National Geospatial

  11. Borehole radar diffraction tomography

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Seong Jun; Kim, Jung Ho; Yi, Myeong Jong; Chung, Seung Hwan; Lee, Hee Il [Korea Institute of Geology Mining and Materials, Taejon (Korea, Republic of)

    1997-12-01

    Tomography is widely used as imaging method for determining subsurface structure. Among the reconstruction algorithms for tomographic imaging, travel time tomography is almost applied to imaging subsurface. But isolated small body comparable with the wavelength could not be well recognized by travel time tomography. Other tomographic method are need to improve the imaging process. In the study of this year, diffraction tomography was investigated. The theory for diffraction tomography is based on the 1st-order Born approximation. Multisource holography, which is similar to Kirchihoff migration, is compared with diffraction tomography. To improve 1st-order Born diffraction tomography, two kinds of filter designed from multisource holography and 2-D green function, respectively, applied on the reconstructed image. The algorithm was tested for the numerical modeling data of which algorithm consists of the analytic computation of radar signal in transmitter and receiver regions and 2-D FDM scheme for the propagation of electromagnetic waves in media. The air-filled cavity model to show a typical diffraction pattern was applied to diffraction tomography imaging, and the result shows accurate location and area of cavity. But the calculated object function is not well matched the real object function, because the air-filled cavity model is not satisfied week scattered inhomogeneity for 1st born approximation, and the error term is included in estimating source wavelet from received signals. In spite of the object function error, the diffraction tomography assist for interpretation of subsurface as if conducted with travel time tomography. And the fracture model was tested, 1st born diffraction tomographic image is poor because of limited view angle coverage and violation of week scatter assumption, but the filtered image resolve the fracture somewhat better. The tested diffraction tomography image confirms effectiveness of filter for enhancing resolution. (author). 14

  12. Hydrologic applications of weather radar

    Science.gov (United States)

    Seo, Dong-Jun; Habib, Emad; Andrieu, Hervé; Morin, Efrat

    2015-12-01

    By providing high-resolution quantitative precipitation information (QPI), weather radars have revolutionized hydrology in the last two decades. With the aid of GIS technology, radar-based quantitative precipitation estimates (QPE) have enabled routine high-resolution hydrologic modeling in many parts of the world. Given the ever-increasing need for higher-resolution hydrologic and water resources information for a wide range of applications, one may expect that the use of weather radar will only grow. Despite the tremendous progress, a number of significant scientific, technological and engineering challenges remain to realize its potential. New challenges are also emerging as new areas of applications are discovered, explored and pursued. The purpose of this special issue is to provide the readership with some of the latest advances, lessons learned, experiences gained, and science issues and challenges related to hydrologic applications of weather radar. The special issue features 20 contributions on various topics which reflect the increasing diversity as well as the areas of focus in radar hydrology today. The contributions may be grouped as follows:

  13. Marine parameters from synergy of optical and radar satellite data

    Science.gov (United States)

    Lehner, S.; Hoja, D.; Schulz-Stellenfleth, J.

    In 2001 the European Space Agency ESA will launch the earth observation satellite ENVISAT. It will carry several instruments that provide new opportunities to measure oceanographic variables. Together, they represent the main measurement techniques of satellite oceanography, and complement each other in an ideal manner. These instruments are to be used in synergy to: Improve the analysis of measured wind and ocean wave fields, and thereby improve weather forecasting at weather centers; Determine the extent and variables of sea ice and develop a five-day sea ice prediction model, to support maritime shipping and offshore activities; Monitor and map sediment and suspended matter transport in coastal regions, especially in areas with large river estuaries, which greatly affects shipping lanes, harbors, and dredging activities; Monitor hydrobiological and bio-geochemical variables related to water quality in coastal regions and large inland waters, which affects ecology, coastal development, aquaculture, drinking water supplies, and tourism. To prepare the oceanographic community to make best use of the ENVISAT sensors in the pre-launch phase, existing algorithms to derive marine parameters are used and validated using data from the ERS SAR, the ERS RA, SeaWiFS and IRS MOS sensors now in operation. Derived products are used to address problems that can best be tackled using the synergy of radar and optical data, such as the effect of surface slicks on radar wind measurements, of sea state on ocean color, of wind and waves on the resuspension of suspended matter, and of wind and waves on sea ice variables.

  14. Application of model-based spectral analysis to wind-profiler radar observations

    Energy Technology Data Exchange (ETDEWEB)

    Boyer, E. [ENS, Cachan (France). LESiR; Petitdidier, M.; Corneil, W. [CETP, Velizy (France); Adnet, C. [THALES Air Dfense, Bagneux (France); Larzabal, P. [ENS, Cachan (France). LESiR; IUT, Cachan (France). CRIIP

    2001-08-01

    A classical way to reduce a radar's data is to compute the spectrum using FFT and then to identify the different peak contributions. But in case an overlapping between the different echoes (atmospheric echo, clutter, hydrometer echo..) exists, Fourier-like techniques provide poor frequency resolution and then sophisticated peak-identification may not be able to detect the different echoes. In order to improve the number of reduced data and their quality relative to Fourier spectrum analysis, three different methods are presented in this paper and applied to actual data. Their approach consists of predicting the main frequency-components, which avoids the development of very sophisticated peak-identification algorithms. The first method is based on cepstrum properties generally used to determine the shift between two close identical echoes. We will see in this paper that this method cannot provide a better estimate than Fourier-like techniques in an operational use. The second method consists of an autoregressive estimation of the spectrum. Since the tests were promising, this method was applied to reduce the radar data obtained during two thunderstorms. The autoregressive method, which is very simple to implement, improved the Doppler-frequency data reduction relative to the FFT spectrum analysis. The third method exploits a MUSIC algorithm, one of the numerous subspace-based methods, which is well adapted to estimate spectra composed of pure lines. A statistical study of performances of this method is presented, and points out the very good resolution of this estimator in comparison with Fourier-like techniques. Application to actual data confirms the good qualities of this estimator for reducing radar's data. (orig.)

  15. Joint Efforts Towards European HF Radar Integration

    Science.gov (United States)

    Rubio, A.; Mader, J.; Griffa, A.; Mantovani, C.; Corgnati, L.; Novellino, A.; Schulz-Stellenfleth, J.; Quentin, C.; Wyatt, L.; Ruiz, M. I.; Lorente, P.; Hartnett, M.; Gorringe, P.

    2016-12-01

    During the past two years, significant steps have been made in Europe for achieving the needed accessibility to High Frequency Radar (HFR) data for a pan-European use. Since 2015, EuroGOOS Ocean Observing Task Teams (TT), such as HFR TT, are operational networks of observing platforms. The main goal is on the harmonization of systems requirements, systems design, data quality, improvement and proof of the readiness and standardization of HFR data access and tools. Particular attention is being paid by HFR TT to converge from different projects and programs toward those common objectives. First, JERICO-NEXT (Joint European Research Infrastructure network for Coastal Observatory - Novel European eXpertise for coastal observaTories, H2020 2015 Programme) will contribute on describing the status of the European network, on seeking harmonization through exchange of best practices and standardization, on developing and giving access to quality control procedures and new products, and finally on demonstrating the use of such technology in the general scientific strategy focused by the Coastal Observatory. Then, EMODnet (European Marine Observation and Data Network) Physics started to assemble HF radar metadata and data products within Europe in a uniform way. This long term program is providing a combined array of services and functionalities to users for obtaining free of charge data, meta-data and data products on the physical conditions of European sea basins and oceans. Additionally, the Copernicus Marine Environment Monitoring Service (CMEMS) delivers from 2015 a core information service to any user related to 4 areas of benefits: Maritime Safety, Coastal and Marine Environment, Marine Resources, and Weather, Seasonal Forecasting and Climate activities. INCREASE (Innovation and Networking for the integration of Coastal Radars into EuropeAn marine SErvices - CMEMS Service Evolution 2016) will set the necessary developments towards the integration of existing European

  16. Extended Target Recognition in Cognitive Radar Networks

    Directory of Open Access Journals (Sweden)

    Xiqin Wang

    2010-11-01

    Full Text Available We address the problem of adaptive waveform design for extended target recognition in cognitive radar networks. A closed-loop active target recognition radar system is extended to the case of a centralized cognitive radar network, in which a generalized likelihood ratio (GLR based sequential hypothesis testing (SHT framework is employed. Using Doppler velocities measured by multiple radars, the target aspect angle for each radar is calculated. The joint probability of each target hypothesis is then updated using observations from different radar line of sights (LOS. Based on these probabilities, a minimum correlation algorithm is proposed to adaptively design the transmit waveform for each radar in an amplitude fluctuation situation. Simulation results demonstrate performance improvements due to the cognitive radar network and adaptive waveform design. Our minimum correlation algorithm outperforms the eigen-waveform solution and other non-cognitive waveform design approaches.

  17. German Radar Observation Shuttle Experiment (ROSE)

    Science.gov (United States)

    Sleber, A. J.; Hartl, P.; Haydn, R.; Hildebrandt, G.; Konecny, G.; Muehlfeld, R.

    1984-01-01

    The success of radar sensors in several different application areas of interest depends on the knowledge of the backscatter of radar waves from the targets of interest, the variance of these interaction mechanisms with respect to changing measurement parameters, and the determination of the influence of he measuring systems on the results. The incidence-angle dependency of the radar cross section of different natural targets is derived. Problems involved by the combination of data gained with different sensors, e.g., MSS-, TM-, SPOTand SAR-images are analyzed. Radar cross-section values gained with ground-based radar spectrometers and spaceborne radar imaging, and non-imaging scatterometers and spaceborne radar images from the same areal target are correlated. The penetration of L-band radar waves into vegetated and nonvegetated surfaces is analyzed.

  18. NOAA NEXt-Generation RADar (NEXRAD) Products

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset consists of Level III weather radar products collected from Next-Generation Radar (NEXRAD) stations located in the contiguous United States, Alaska,...

  19. MST radar data-base management

    Science.gov (United States)

    Wickwar, V. B.

    1983-01-01

    Data management for Mesospheric-Stratospheric-Tropospheric, (MST) radars is addressed. An incoherent-scatter radar data base is discussed in terms of purpose, centralization, scope, and nature of the data base management system.

  20. Design of multi-frequency CW radars

    CERN Document Server

    Jankiraman, Mohinder

    2007-01-01

    This book deals with the basic theory for design and analysis of Low Probability of Intercept (LPI) radar systems. The design of one such multi-frequency high resolution LPI radar, PANDORA, is covered.

  1. Modern approach to relativity theory (radar formulation)

    International Nuclear Information System (INIS)

    Strel'tsov, V.N.

    1991-01-01

    The main peculiarities of the radar formulation of the relativity theory are presented. This formulation operates with the retarded (light) distances and relativistic or radar length introduced on their basis. 21 refs.; 1 tab

  2. Meteor detection on ST (MST) radars

    International Nuclear Information System (INIS)

    Avery, S.K.

    1987-01-01

    The ability to detect radar echoes from backscatter due to turbulent irregularities of the radio refractive index in the clear atmosphere has lead to an increasing number of established mesosphere - stratosphere - troposphere (MST or ST) radars. Humidity and temperature variations are responsible for the echo in the troposphere and stratosphere and turbulence acting on electron density gradients provides the echo in the mesosphere. The MST radar and its smaller version, the ST radar, are pulsed Doppler radars operating in the VHF - UHF frequency range. These echoes can be used to determine upper atmosphere winds at little extra cost to the ST radar configuration. In addition, the meteor echoes can supplement mesospheric data from an MST radar. The detection techniques required on the ST radar for delineating meteor echo returns are described

  3. North and northeast Greenland ice discharge from satellite radar interferometry

    DEFF Research Database (Denmark)

    Rignot, E.J.; Gogineni, S.P.; Krabill, W.B.

    1997-01-01

    Ice discharge from north and northeast Greenland calculated from satellite radar interferometry data of 14 outlet glaciers is 3.5 times that estimated from iceberg production. The satellite estimates, obtained at the grounding line of the outlet glaciers, differ from those obtained at the glacier...... front, because basal melting is extensive at the underside of the floating glacier sections. The results suggest that the north and northeast parts of the Greenland ice sheet may be thinning and contributing positively to sea-level rise....

  4. Generic framework for vessel detection and tracking based on distributed marine radar image data

    Science.gov (United States)

    Siegert, Gregor; Hoth, Julian; Banyś, Paweł; Heymann, Frank

    2018-04-01

    Situation awareness is understood as a key requirement for safe and secure shipping at sea. The primary sensor for maritime situation assessment is still the radar, with the AIS being introduced as supplemental service only. In this article, we present a framework to assess the current situation picture based on marine radar image processing. Essentially, the framework comprises a centralized IMM-JPDA multi-target tracker in combination with a fully automated scheme for track management, i.e., target acquisition and track depletion. This tracker is conditioned on measurements extracted from radar images. To gain a more robust and complete situation picture, we are exploiting the aspect angle diversity of multiple marine radars, by fusing them a priori to the tracking process. Due to the generic structure of the proposed framework, different techniques for radar image processing can be implemented and compared, namely the BLOB detector and SExtractor. The overall framework performance in terms of multi-target state estimation will be compared for both methods based on a dedicated measurement campaign in the Baltic Sea with multiple static and mobile targets given.

  5. SAR Ambiguity Study for the Cassini Radar

    Science.gov (United States)

    Hensley, Scott; Im, Eastwood; Johnson, William T. K.

    1993-01-01

    The Cassini Radar's synthetic aperture radar (SAR) ambiguity analysis is unique with respect to other spaceborne SAR ambiguity analyses owing to the non-orbiting spacecraft trajectory, asymmetric antenna pattern, and burst mode of data collection. By properly varying the pointing, burst mode timing, and radar parameters along the trajectory this study shows that the signal-to-ambiguity ratio of better than 15 dB can be achieved for all images obtained by the Cassini Radar.

  6. Radar operation in a hostile electromagnetic environment

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-03-01

    Radar ISR does not always involve cooperative or even friendly targets. An adversary has numerous techniques available to him to counter the effectiveness of a radar ISR sensor. These generally fall under the banner of jamming, spoofing, or otherwise interfering with the EM signals required by the radar sensor. Consequently mitigation techniques are prudent to retain efficacy of the radar sensor. We discuss in general terms a number of mitigation techniques.

  7. Radar reflection off extensive air showers

    CERN Document Server

    Stasielak, J; Bertaina, M; Blümer, J; Chiavassa, A; Engel, R; Haungs, A; Huege, T; Kampert, K -H; Klages, H; Kleifges, M; Krömer, O; Ludwig, M; Mathys, S; Neunteufel, P; Pekala, J; Rautenberg, J; Riegel, M; Roth, M; Salamida, F; Schieler, H; Šmída, R; Unger, M; Weber, M; Werner, F; Wilczyński, H; Wochele, J

    2012-01-01

    We investigate the possibility of detecting extensive air showers by the radar technique. Considering a bistatic radar system and different shower geometries, we simulate reflection of radio waves off the static plasma produced by the shower in the air. Using the Thomson cross-section for radio wave reflection, we obtain the time evolution of the signal received by the antennas. The frequency upshift of the radar echo and the power received are studied to verify the feasibility of the radar detection technique.

  8. Compressive sensing for urban radar

    CERN Document Server

    Amin, Moeness

    2014-01-01

    With the emergence of compressive sensing and sparse signal reconstruction, approaches to urban radar have shifted toward relaxed constraints on signal sampling schemes in time and space, and to effectively address logistic difficulties in data acquisition. Traditionally, these challenges have hindered high resolution imaging by restricting both bandwidth and aperture, and by imposing uniformity and bounds on sampling rates.Compressive Sensing for Urban Radar is the first book to focus on a hybrid of two key areas: compressive sensing and urban sensing. It explains how reliable imaging, tracki

  9. Principles of modern radar advanced techniques

    CERN Document Server

    Melvin, William

    2012-01-01

    Principles of Modern Radar: Advanced Techniques is a professional reference for practicing engineers that provides a stepping stone to advanced practice with in-depth discussions of the most commonly used advanced techniques for radar design. It will also serve advanced radar academic and training courses with a complete set of problems for students as well as solutions for instructors.

  10. Efficient Ways to Learn Weather Radar Polarimetry

    Science.gov (United States)

    Cao, Qing; Yeary, M. B.; Zhang, Guifu

    2012-01-01

    The U.S. weather radar network is currently being upgraded with dual-polarization capability. Weather radar polarimetry is an interdisciplinary area of engineering and meteorology. This paper presents efficient ways to learn weather radar polarimetry through several basic and practical topics. These topics include: 1) hydrometeor scattering model…

  11. Radar geomorphology of coastal and wetland environments

    Science.gov (United States)

    Lewis, A. J.; Macdonald, H. C.

    1973-01-01

    Details regarding the collection of radar imagery over the past ten years are considered together with the geomorphic, geologic, and hydrologic data which have been extracted from radar imagery. Recent investigations were conducted of the Louisiana swamp marsh and the Oregon coast. It was found that radar imagery is a useful tool to the scientist involved in wetland research.

  12. 46 CFR 184.404 - Radars.

    Science.gov (United States)

    2010-10-01

    ... within one mile of land must be fitted with a FCC Type Accepted general marine radar system for surface... Federal Communications Commission (FCC) type accepted general marine radar system for surface navigation... 46 Shipping 7 2010-10-01 2010-10-01 false Radars. 184.404 Section 184.404 Shipping COAST GUARD...

  13. Recommendation on Transition from Primary/Secondary Radar to Secondary- Only Radar Capability

    Science.gov (United States)

    1994-10-01

    Radar Beacon Performance Monitor RCIU Remote Control Interface Unit RCL Remote Communications Link R E&D Research, Engineering and Development RML Radar...rate. 3.1.2.5 Maintenance The current LRRs have limited remote maintenance monitoring (RMM) capabilities via the Remote Control Interface Unit ( RCIU ...1, -2 and FPS-20 radars required an upgrade of some of the radar subsystems, namely the RCIU to respond as an RMS and the CD to interface with radar

  14. The impact of reflectivity correction and accounting for raindrop size distribution variability to improve precipitation estimation by weather radar for an extreme low-land mesoscale convective system

    Science.gov (United States)

    Hazenberg, Pieter; Leijnse, Hidde; Uijlenhoet, Remko

    2014-11-01

    Between 25 and 27 August 2010 a long-duration mesoscale convective system was observed above the Netherlands, locally giving rise to rainfall accumulations exceeding 150 mm. Correctly measuring the amount of precipitation during such an extreme event is important, both from a hydrological and meteorological perspective. Unfortunately, the operational weather radar measurements were affected by multiple sources of error and only 30% of the precipitation observed by rain gauges was estimated. Such an underestimation of heavy rainfall, albeit generally less strong than in this extreme case, is typical for operational weather radar in The Netherlands. In general weather radar measurement errors can be subdivided into two groups: (1) errors affecting the volumetric reflectivity measurements (e.g. ground clutter, radar calibration, vertical profile of reflectivity) and (2) errors resulting from variations in the raindrop size distribution that in turn result in incorrect rainfall intensity and attenuation estimates from observed reflectivity measurements. A stepwise procedure to correct for the first group of errors leads to large improvements in the quality of the estimated precipitation, increasing the radar rainfall accumulations to about 65% of those observed by gauges. To correct for the second group of errors, a coherent method is presented linking the parameters of the radar reflectivity-rain rate (Z - R) and radar reflectivity-specific attenuation (Z - k) relationships to the normalized drop size distribution (DSD). Two different procedures were applied. First, normalized DSD parameters for the whole event and for each precipitation type separately (convective, stratiform and undefined) were obtained using local disdrometer observations. Second, 10,000 randomly generated plausible normalized drop size distributions were used for rainfall estimation, to evaluate whether this Monte Carlo method would improve the quality of weather radar rainfall products. Using the

  15. Environmental studies of the Arabian Sea using remote sensing, GIS and GPS techniques

    Digital Repository Service at National Institute of Oceanography (India)

    Saxena, A.

    Fig 4. Principle of Radar altimetry 17 Fig 5. Block diagram of ArcGIS platform 20 CHAPTER IV RESULT AND DISCUSSION CHAPTER II TOOL FOR STUDY Fig 6. Seasonal Variation of Sea Surface Temperature 24 Fig 7. Seasonal... from any major rivers, the excessive evaporation over precipitation (E-P) as well as proximity to the Red Sea and Persian Gulf makes the surface salinity of Arabian Sea high, in excess of 36psu (practical salinity unit). Motivation Arabian Sea...

  16. X-Band wave radar system for monitoring and risk management of the coastal infrastructures

    Science.gov (United States)

    Ludeno, Giovanni; Soldovieri, Francesco; Serafino, Francesco

    2017-04-01

    The presence of the infrastructures in coastal region entails an increase of the sea level and the shift of the sediment on the bottom with a continuous change of the coastline. In order to preserve the coastline, it has been necessary to resort the use of applications coastal engineering, as the construction of the breakwaters for preventing the coastal erosion. In this frame, the knowledge of the sea state parameters, as wavelength, period and significant wave height and of surface current and bathymetry can be used for the harbor operations and to prevent environmental disasters. In the last years, the study of the coastal phenomena and monitoring of the sea waves impact on the coastal infrastructures through the analysis of images acquired by marine X-band radars is of great interest [1-3]. The possibility to observe the sea surface from radar images is due to the fact that the X-band electromagnetic waves interact with the sea capillary waves (Bragg resonance), which ride on the gravity waves. However, the image acquired by a X-band radar is not the direct representation of the sea state, but it represents the sea surface as seen by the radar. Accordingly, to estimate the sea state parameters as, direction, wavelength, period of dominant waves, the significant wave height as well as the bathymetry and surface current, through a time stack of radar data are required advanced data processing procedures. In particular, in the coastal areas due to the non-uniformity of sea surface current and bathymetry fields is necessary a local analysis of the sea state parameters. In order to analyze the data acquired in coastal area an inversion procedure defined "Local Method" is adopted, which is based on the spatial partitioning of the investigated area in partially overlapping sub-areas. In addition, the analysis of the sea spectrum of each sub-area allows us to retrieve the local sea state parameters. In particular, this local analysis allows us to detect the reflected

  17. The ISMAR high frequency coastal radar network: Monitoring surface currents for management of marine resources

    DEFF Research Database (Denmark)

    Carlson, Daniel Frazier

    2015-01-01

    The Institute of Marine Sciences (ISMAR) of the National Research Council of Italy (CNR) established a High Frequency (HF) Coastal Radar Network for the measurement of the velocity of surface currents in coastal seas. The network consists of four HF radar systems located on the coast of the Gargano...... Promontory (Southern Adriatic, Italy). The network has been operational since May 2013 and covers an area of approximately 1700 square kilometers in the Gulf of Manfredonia. Quality Assessment (QA) procedures are applied for the systems deployment and maintenance and Quality Control (QC) procedures...

  18. Application of borehole radar to South Africa’s Ultra-Deep gold mining environment

    CSIR Research Space (South Africa)

    Trickett, JC

    2000-05-01

    Full Text Available ), the collar of which is located at a depth of 3.3 km below datum1. LIB boreholes are used to probe totally undeveloped blocks of ground and, being semi-parallel to reef, are ideal for the application of Borehole Radar. By applying Borehole Radar from... the target reef; viz. 1 For the Witwatersrand Basin Gold Mines, the datum is ? 1829 m above sea level. Ventersdorp Contact Reef (VCR), twice. It was drilled at 45? downwards into the hangingwall...

  19. Análisis y estudio del radar Ramet AD9

    OpenAIRE

    López Jiménez, José Manuel

    2009-01-01

    El proyecto está basado en un estudio completo y detallado del radar RAMET modelo AD9. Las autoridades de tráfico catalanas, a través del Servei Català del Trànsit, están introduciendo en nuestras carreteras este tipo de cinemómetro desde el año 2007, para el control de tráfico en carretera. El hecho de ser una novedad dentro de nuestro entorno hace que su desconocimiento sobre su composición y sus peculiaridades respecto a otro tipo de radares sea interesante realizar este estudio....

  20. Quantifying South East Asia's forest degradation using latest generation optical and radar satellite remote sensing

    Science.gov (United States)

    Broich, M.; Tulbure, M. G.; Wijaya, A.; Weisse, M.; Stolle, F.

    2017-12-01

    Deforestation and forest degradation form the 2nd largest source of anthropogenic CO2 emissions. While deforestation is being globally mapped with satellite image time series, degradation remains insufficiently quantified. Previous studies quantified degradation for small scale, local sites. A method suitable for accurate mapping across large areas has not yet been developed due to the variability of the low magnitude and short-lived degradation signal and the absence of data with suitable resolution properties. Here we use a combination of newly available streams of free optical and radar image time series acquired by NASA and ESA, and HPC-based data science algorithms to innovatively quantify degradation consistently across Southeast Asia (SEA). We used Sentinel1 c-band radar data and NASA's new Harmonized Landsat8 (L8) Sentinel2 (S2) product (HLS) for cloud free optical images. Our results show that dense time series of cloud penetrating Sentinel 1 c-band radar can provide degradation alarm flags, while the HLS product of cloud-free optical images can unambiguously confirm degradation alarms. The detectability of degradation differed across SEA. In the seasonal forest of continental SEA the reliability of our radar-based alarm flags increased as the variability in landscape moisture decreases in the dry season. We reliably confirmed alarms with optical image time series during the late dry season, where degradation in open canopy forests becomes detectable once the undergrowth vegetation has died down. Conversely, in insular SEA landscape moisture is low, the radar time series generated degradation alarms flags with moderate to high reliability throughout the year, further confirmed with the HLS product. Based on the HLS product we can now confirm degradation within time series provides better results than either one on its own. Our results provide significant information with application for carbon trading policy and land management.

  1. Radioprotection and radar: practical aspects

    International Nuclear Information System (INIS)

    Pepersack, J.P.

    1979-01-01

    The author, on basis of his experience in radar-radioprotection, exposes the standard and security norms and recommendations to be applied for the preventive adapation of the work-areas as well as for the follow-up of the exposed workers. (author)

  2. Radar-based collision avoidance for unmanned surface vehicles

    Science.gov (United States)

    Zhuang, Jia-yuan; Zhang, Lei; Zhao, Shi-qi; Cao, Jian; Wang, Bo; Sun, Han-bing

    2016-12-01

    Unmanned surface vehicles (USVs) have become a focus of research because of their extensive applications. To ensure safety and reliability and to perform complex tasks autonomously, USVs are required to possess accurate perception of the environment and effective collision avoidance capabilities. To achieve these, investigation into realtime marine radar target detection and autonomous collision avoidance technologies is required, aiming at solving the problems of noise jamming, uneven brightness, target loss, and blind areas in marine radar images. These technologies should also satisfy the requirements of real-time and reliability related to high navigation speeds of USVs. Therefore, this study developed an embedded collision avoidance system based on the marine radar, investigated a highly real-time target detection method which contains adaptive smoothing algorithm and robust segmentation algorithm, developed a stable and reliable dynamic local environment model to ensure the safety of USV navigation, and constructed a collision avoidance algorithm based on velocity obstacle (V-obstacle) which adjusts the USV's heading and speed in real-time. Sea trials results in multi-obstacle avoidance firstly demonstrate the effectiveness and efficiency of the proposed avoidance system, and then verify its great adaptability and relative stability when a USV sailing in a real and complex marine environment. The obtained results will improve the intelligent level of USV and guarantee the safety of USV independent sailing.

  3. Synthetic aperture radar capabilities in development

    Energy Technology Data Exchange (ETDEWEB)

    Miller, M. [Lawrence Livermore National Lab., CA (United States)

    1994-11-15

    The Imaging and Detection Program (IDP) within the Laser Program is currently developing an X-band Synthetic Aperture Radar (SAR) to support the Joint US/UK Radar Ocean Imaging Program. The radar system will be mounted in the program`s Airborne Experimental Test-Bed (AETB), where the initial mission is to image ocean surfaces and better understand the physics of low grazing angle backscatter. The Synthetic Aperture Radar presentation will discuss its overall functionality and a brief discussion on the AETB`s capabilities. Vital subsystems including radar, computer, navigation, antenna stabilization, and SAR focusing algorithms will be examined in more detail.

  4. Radar application in void and bar detection

    International Nuclear Information System (INIS)

    Amry Amin Abas; Mohamad Pauzi Ismail; Suhairy Sani

    2003-01-01

    Radar is one of the new non-destructive testing techniques for concrete and structures inspection. Radar is a non-ionizing electromagnetic wave that can penetrate deep into concrete or soil in about several tenths of meters. Method of inspection using radar enables us to perform high resolution detection, imaging and mapping of subsurface concrete and soil condition. This paper will discuss the use of radar for void and bar detection and sizing. The samples used in this paper are custom made samples and comparison will be made to validate the use of radar in detecting, locating and also size determination of voids and bars. (Author)

  5. A Radar Climatology for Germany - a 16-year high resolution precipitation data and its possibilities

    Science.gov (United States)

    Walawender, Ewelina; Winterrath, Tanja; Brendel, Christoph; Hafer, Mario; Junghänel, Thomas; Klameth, Anna; Weigl, Elmar; Becker, Andreas

    2017-04-01

    One of the main features of heavy precipitation events is their small-scale distribution. Despite a local occurrence, these intensive rainfalls may, however, cause most serious damage and have significant impact on the whole river basin area resulting in e.g. flash floods or urban flooding. Thus, it is of great importance not only to detect the life-cycle of extreme precipitation during its occurrence but also to collect precise climatological information on such events. The German weather service (Deutscher Wetterdienst) operates a very dense network of more than 2000 weather stations collecting data on precipitation. It is however not sufficient for detecting spatially limited phenomena. Thanks to radar data, current monitoring of such events is possible. A quality control process is applied to real-time radar products, however only automatic rain gauges data can be used in the adjustment procedure. To merge both radar data and all available rain gauges data, the radar climatology dataset was established. Within the framework of a project financed by the federal agencies' strategic alliance 'Adaptation to Climate Change', 16 years (2001-2016) of radar data have been reanalyzed in order to gain a homogenous, quality-controlled, high-resolution precipitation data set suitable for analyzing extreme events in a climatological approach. Additional corrections methods (e.g. clutter, spokes and beam height correction) were defined and used for the reprocessing procedure to enhance the data quality. Although the time series is still rather short for a climatology, for the first time the data set allows an insight into e.g. the distribution, size, life cycle, and duration of extreme events that cannot be measured by point measurements alone. All radar climatology products share the same spatial and temporal coverage. The whole dataset has been produced for the area of Germany. With the relatively high spatial resolution of 1km, the data can be used as a component of wide

  6. The study of fresh-water lake ice using multiplexed imaging radar

    Science.gov (United States)

    Leonard, Bryan M.; Larson, R.W.

    1975-01-01

    The study of ice in the upper Great Lakes, both from the operational and the scientific points of view, is receiving continued attention. Quantitative and qualitative field work is being conducted to provide the needed background for accurate interpretation of remotely sensed data. The data under discussion in this paper were obtained by a side-looking multiplexed airborne radar (SLAR) supplemented with ground-truth data.Because of its ability to penetrate adverse weather, radar is an especially important instrument for monitoring ice in the upper Great Lakes. It has previously been shown that imaging radars can provide maps of ice cover in these areas. However, questions concerning both the nature of the surfaces reflecting radar energy and the interpretation of the radar imagery continually arise.Our analysis of ice in Whitefish Bay (Lake Superior) indicates that the combination of the ice/water interlace and the ice/air interface is the major contributor to the radar backscatter as seen on the imagery At these frequencies the ice has a very low relative dielectric permittivity (types studied include newly formed black ice, pancake ice, and frozen and consolidated pack and brash ice.Although ice thickness cannot be measured directly from the received signals, it is suspected that by combining the information pertaining to radar backscatter with data on the meteorological and sea-state history of the area, together with some basic ground truth, better estimates of the ice thickness may be provided. In addition, certain ice features (e.g. ridges, ice-foot formation, areas of brash ice) may be identified with reasonable confidence. There is a continued need for additional ground work to verify the validity of imaging radars for these types of interpretations.

  7. Radar meteor rates and solar activity

    International Nuclear Information System (INIS)

    Prikryl, P.

    1983-01-01

    The short-term variation of diurnal radar meteor rates with solar activity represented by solar microwave flux Fsub(10.7), and sunspots relative number Rsub(z), is investigated. Applying the superposed-epoch analysis to the observational material of radar meteor rates from Christchurch (1960-61 and 1963-65), a decrease in the recorded radar rates is found during days of enhanced solar activity. No effect of geomagnetic activity similar to the one reported for the Swedish and Canadian radar meteor data was found by the author in the Christchurch data. A possible explanation of the absence of the geomagnetic effect on radar meteor rates from New Zealand due to a lower echo ceiling height of the Christchurch radar is suggested. The variation of the atmospheric parameters as a possible cause of the observed variation in radar meteor rates is also discussed. (author)

  8. Bathymetry Determination via X-Band Radar Data: A New Strategy and Numerical Results

    Directory of Open Access Journals (Sweden)

    Francesco Soldovieri

    2010-07-01

    Full Text Available This work deals with the question of sea state monitoring using marine X-band radar images and focuses its attention on the problem of sea depth estimation. We present and discuss a technique to estimate bathymetry by exploiting the dispersion relation for surface gravity waves. This estimation technique is based on the correlation between the measured and the theoretical sea wave spectra and a simple analysis of the approach is performed through test cases with synthetic data. More in detail, the reliability of the estimate technique is verified through simulated data sets that are concerned with different values of bathymetry and surface currents for two types of sea spectrum: JONSWAP and Pierson-Moskowitz. The results show how the estimated bathymetry is fairly accurate for low depth values, while the estimate is less accurate as the bathymetry increases, due to a less significant role of the bathymetry on the sea surface waves as the water depth increases.

  9. Active Sensing Air Pressure Using Differential Absorption Barometric Radar

    Science.gov (United States)

    Lin, B.

    2016-12-01

    Tropical storms and other severe weathers cause huge life losses and property damages and have major impacts on public safety and national security. Their observations and predictions need to be significantly improved. This effort tries to develop a feasible active microwave approach that measures surface air pressure, especially over open seas, from space using a Differential-absorption BArometric Radar (DiBAR) operating at 50-55 GHz O2 absorption band in order to constrain assimilated dynamic fields of numerical weather Prediction (NWP) models close to actual conditions. Air pressure is the most important variable that drives atmospheric dynamics, and currently can only be measured by limited in-situ observations over oceans. Even over land there is no uniform coverage of surface air pressure measurements. Analyses show that with the proposed space radar the errors in instantaneous (averaged) pressure estimates can be as low as 4mb ( 1mb) under all weather conditions. NASA Langley research team has made substantial progresses in advancing the DiBAR concept. The feasibility assessment clearly shows the potential of surface barometry using existing radar technologies. The team has also developed a DiBAR system design, fabricated a Prototype-DiBAR (P-DiBAR) for proof-of-concept, conducted laboratory, ground and airborne P-DiBAR tests. The flight test results are consistent with the instrumentation goals. The precision and accuracy of radar surface pressure measurements are within the range of the theoretical analysis of the DiBAR concept. Observational system simulation experiments for space DiBAR performance based on the existing DiBAR technology and capability show substantial improvements in tropical storm predictions, not only for the hurricane track and position but also for the hurricane intensity. DiBAR measurements will provide us an unprecedented level of the prediction and knowledge on global extreme weather and climate conditions.

  10. Real-data tests of a single-Doppler radar assimilation system

    Science.gov (United States)

    Nehrkorn, Thomas; Hegarty, James; Hamill, Thomas M.

    1994-06-01

    Real data tests of a single-Doppler radar data assimilation and forecast system have been conducted for a Florida sea breeze case. The system consists of a hydrostatic mesoscale model used for prediction of the preconvective boundary layer, an objective analysis that combines model first guess fields with radar derived horizontal winds, a thermodynamic retrieval scheme that obtains temperature information from the three-dimensional wind field and its temporal evolution, and a Newtonian nudging scheme for forcing the model forecast to closer agreement with the analysis. As was found in earlier experiments with simulated data, assimilation using Newtonian nudging benefits from temperature data in addition to wind data. The thermodynamic retrieval technique was successful in retrieving a horizontal temperature gradient from the radar-derived wind fields that, when assimilated into the model, led to a significantly improved forecast of the seabreeze strength and position.

  11. Penn State Radar Systems: Implementation and Observations

    Science.gov (United States)

    Urbina, J. V.; Seal, R.; Sorbello, R.; Kuyeng, K.; Dyrud, L. P.

    2014-12-01

    Software Defined Radio/Radar (SDR) platforms have become increasingly popular as researchers, hobbyists, and military seek more efficient and cost-effective means for radar construction and operation. SDR platforms, by definition, utilize a software-based interface for configuration in contrast to traditional, hard-wired platforms. In an effort to provide new and improved radar sensing capabilities, Penn State has been developing advanced instruments and technologies for future radars, with primary objectives of making such instruments more capable, portable, and more cost effective. This paper will describe the design and implementation of two low-cost radar systems and their deployment in ionospheric research at both low and mid-latitudes. One radar has been installed near Penn State campus, University Park, Pennsylvania (77.97°W, 40.70°N), to make continuous meteor observations and mid-latitude plasma irregularities. The second radar is being installed in Huancayo (12.05°S, -75.33°E), Peru, which is capable of detecting E and F region plasma irregularities as well as meteor reflections. In this paper, we examine and compare the diurnal and seasonal variability of specular, non- specular, and head-echoes collected with these two new radar systems and discuss sampling biases of each meteor observation technique. We report our current efforts to validate and calibrate these radar systems with other VHF radars such as Jicamarca and SOUSY. We also present the general characteristics of continuous measurements of E-region and F-region coherent echoes using these modern radar systems and compare them with coherent radar events observed at other geographic mid-latitude radar stations.

  12. Radar observations of Comet Halley

    International Nuclear Information System (INIS)

    Campbell, D.B.; Harmon, J.K.; Shapiro, I.I.

    1989-01-01

    Five nights of Arecibo radar observations of Comet Halley are reported which reveal a feature in the overall average spectrum which, though weak, seems consistent with being an echo from the comet. The large radar cross section and large bandwidth of the feature suggest that the echo is predominantly from large grains which have been ejected from the nucleus. Extrapolation of the dust particle size distribution to large grain sizes gives a sufficient number of grains to account for the echo. The lack of a detectable echo from the nucleus, combined with estimates of its size and rotation rate from spacecraft encounters and other data, indicate that the nucleus has a surface of relatively high porosity. 33 references

  13. Terahertz radar cross section measurements.

    Science.gov (United States)

    Iwaszczuk, Krzysztof; Heiselberg, Henning; Jepsen, Peter Uhd

    2010-12-06

    We perform angle- and frequency-resolved radar cross section (RCS) measurements on objects at terahertz frequencies. Our RCS measurements are performed on a scale model aircraft of size 5-10 cm in polar and azimuthal configurations, and correspond closely to RCS measurements with conventional radar on full-size objects. The measurements are performed in a terahertz time-domain system with freely propagating terahertz pulses generated by tilted pulse front excitation of lithium niobate crystals and measured with sub-picosecond time resolution. The application of a time domain system provides ranging information and also allows for identification of scattering points such as weaponry attached to the aircraft. The shapes of the models and positions of reflecting parts are retrieved by the filtered back projection algorithm.

  14. Multichannel surface clutter suppression: East Antarctica P-band SAR ice sounding in the presence of grating lobes

    DEFF Research Database (Denmark)

    Bekaert, David; Gebert, Nicolas; Lin, Chung-Chi

    2014-01-01

    with the European Space Agency's P-band POLarimetric Airborne Radar Ice Sounder (POLARIS). The 4 m long antenna of POLARIS enables simultaneous reception of up to four across-track channels. It was operated in 2011 over Antarctica at a high flight altitude of 3200 m. Different coherent weighting techniques...

  15. Construction of Polarimetric Radar-Based Reference Rain Maps for the Iowa Flood Studies Campaign

    Science.gov (United States)

    Petersen, Walt; Krajewski, Witek; Wolff, David; Gatlin, Patrick

    2015-04-01

    to efforts using the NPOL radar dataset. The initial portions of the "process" involved dual-polarimetric quality control procedures which employed standard phase and correlation-based approaches to removal of clutter and non-meteorological echo. Calculation of a scale-adaptive KDP was accomplished using the method of Wang and Chandrasekar (2009; J. Atmos. Oceanic Tech.). A dual-polarimetric blockage algorithm based on Lang et al. (2009; J. Atmos. Oceanic Tech.) was then implemented to correct radar reflectivity and differential reflectivity at low elevation angles. Next, hydrometeor identification algorithms were run to identify liquid and ice hydrometeors. After the quality control and data preparation steps were completed several different dual-polarimetric rain estimation algorithms were employed to estimate rainfall rates using rainfall scans collected approximately every two to three minutes throughout the campaign. These algorithms included a polarimetrically-tuned Z-R algorithm that adjusts for drop oscillations (via Bringi et al., 2004, J. Atmos. Oceanic Tech.), and several different hybrid polarimetric variable approaches, including one that made use of parameters tuned to IFloodS 2D Video Disdrometer measurements. Finally, a hybrid scan algorithm was designed to merge the rain rate estimates from multiple low level elevation angle scans (where blockages could not be appropriately corrected) in order to create individual low-level rain maps. Individual rain maps at each time step were subsequently accumulated over multiple time scales for comparison to gauge network data. The comparison results and overall error character depended strongly on rain event type, polarimetric estimator applied, and range from the radar. We will present the outcome of these comparisons and their impact on constructing composited "reference" rainfall maps at select time and space scales.

  16. Construction of Polarimetric Radar-Based Reference Rain Maps for the Iowa Flood Studies Campaign

    Science.gov (United States)

    Petersen, Walter; Wolff, David; Krajewski, Witek; Gatlin, Patrick

    2015-01-01

    to efforts using the NPOL radar dataset. The initial portions of the "process" involved dual-polarimetric quality control procedures which employed standard phase and correlation-based approaches to removal of clutter and non-meteorological echo. Calculation of a scale-adaptive KDP was accomplished using the method of Wang and Chandrasekar (2009; J. Atmos. Oceanic Tech.). A dual-polarimetric blockage algorithm based on Lang et al. (2009; J. Atmos. Oceanic Tech.) was then implemented to correct radar reflectivity and differential reflectivity at low elevation angles. Next, hydrometeor identification algorithms were run to identify liquid and ice hydrometeors. After the quality control and data preparation steps were completed several different dual-polarimetric rain estimation algorithms were employed to estimate rainfall rates using rainfall scans collected approximately every two to three minutes throughout the campaign. These algorithms included a polarimetrically-tuned Z-R algorithm that adjusts for drop oscillations (via Bringi et al., 2004, J. Atmos. Oceanic Tech.), and several different hybrid polarimetric variable approaches, including one that made use of parameters tuned to IFloodS 2D Video Disdrometer measurements. Finally, a hybrid scan algorithm was designed to merge the rain rate estimates from multiple low level elevation angle scans (where blockages could not be appropriately corrected) in order to create individual low-level rain maps. Individual rain maps at each time step were subsequently accumulated over multiple time scales for comparison to gauge network data. The comparison results and overall error character depended strongly on rain event type, polarimetric estimator applied, and range from the radar. We will present the outcome of these comparisons and their impact on constructing composited "reference" rainfall maps at select time and space scales.

  17. Automated Ground Penetrating Radar hyperbola detection in complex environment

    Science.gov (United States)

    Mertens, Laurence; Lambot, Sébastien

    2015-04-01

    Ground Penetrating Radar (GPR) systems are commonly used in many applications to detect, amongst others, buried targets (various types of pipes, landmines, tree roots ...), which, in a cross-section, present theoretically a particular hyperbolic-shaped signature resulting from the antenna radiation pattern. Considering the large quantity of information we can acquire during a field campaign, a manual detection of these hyperbolas is barely possible, therefore we have a real need to have at our disposal a quick and automated detection of these hyperbolas. However, this task may reveal itself laborious in real field data because these hyperbolas are often ill-shaped due to the heterogeneity of the medium and to instrumentation clutter. We propose a new detection algorithm for well- and ill-shaped GPR reflection hyperbolas especially developed for complex field data. This algorithm is based on human recognition pattern to emulate human expertise to identify the hyperbolas apexes. The main principle relies in a fitting process of the GPR image edge dots detected with Canny filter to analytical hyperbolas, considering the object as a punctual disturbance with a physical constraint of the parameters. A long phase of observation of a large number of ill-shaped hyperbolas in various complex media led to the definition of smart criteria characterizing the hyperbolic shape and to the choice of accepted value ranges acceptable for an edge dot to correspond to the apex of a specific hyperbola. These values were defined to fit the ambiguity zone for the human brain and present the particularity of being functional in most heterogeneous media. Furthermore, the irregularity is particularly taken into account by defining a buffer zone around the theoretical hyperbola in which the edge dots need to be encountered to belong to this specific hyperbola. First, the method was tested in laboratory conditions over tree roots and over PVC pipes with both time- and frequency-domain radars

  18. Radar Control Optimal Resource Allocation

    Science.gov (United States)

    2015-07-13

    Dartmouth, Nova Scotia, Canada by the McMaster University Intelligent PIXel (IPIX) X-band Polarimetric Coherent Radar during the OHGR - Dartmouth...following coefficients [ q2, 4p22q, 12p12q, 12p11q, 12|P | ] (26) for A4 and [ q2, 4p22q, 4q(3 p12 + r22), 12(p11q + p22r22 − qr12), 12(|P |+ 2r22p12

  19. Radar channel balancing with commutation

    Energy Technology Data Exchange (ETDEWEB)

    Doerry, Armin Walter

    2014-02-01

    When multiple channels are employed in a pulse-Doppler radar, achieving and maintaining balance between the channels is problematic. In some circumstances the channels may be commutated to achieve adequate balance. Commutation is the switching, trading, toggling, or multiplexing of the channels between signal paths. Commutation allows modulating the imbalance energy away from the balanced energy in Doppler, where it can be mitigated with filtering.

  20. Radar-based hail detection

    Czech Academy of Sciences Publication Activity Database

    Skripniková, Kateřina; Řezáčová, Daniela

    2014-01-01

    Roč. 144, č. 1 (2014), s. 175-185 ISSN 0169-8095 R&D Projects: GA ČR(CZ) GAP209/11/2045; GA MŠk LD11044 Institutional support: RVO:68378289 Keywords : hail detection * weather radar * hail damage risk Subject RIV: DG - Athmosphere Sciences, Meteorology Impact factor: 2.844, year: 2014 http://www.sciencedirect.com/science/article/pii/S0169809513001804

  1. Radar-eddy current GPR

    OpenAIRE

    A. O. Abramovych

    2014-01-01

    Introduction. At present there are many electrical schematic metal detectors (the most common kind of ground penetrating radar), which are differ in purpose. Each scheme has its own advantages and disadvantages compared to other schemes. Designing metal detector problem of optimal selection of functional units most schemes can only work with a narrow range of special purpose units. Functional units used in circuits can be replaced by better ones, but specialization schemes do not provide such...

  2. On the design and construction of drifting-mine test targets for sonar, radar and electro-optical detection experiments

    NARCIS (Netherlands)

    Dol, H.S.

    2014-01-01

    The timely detection of small hazardous objects at the sea surface, such as drifting mines, is challenging for ship-mounted sensor systems, both for underwater sensor systems like sonar and above-water sensor systems like radar and electro-optics (lidar, infrared/visual cameras). This is due to the

  3. Detecting and classifying low probability of intercept radar

    CERN Document Server

    Pace, Philip E

    2008-01-01

    This revised and expanded second edition brings you to the cutting edge with new chapters on LPI radar design, including over-the-horizon radar, random noise radar, and netted LPI radar. You also discover critical LPI detection techniques, parameter extraction signal processing techniques, and anti-radiation missile design strategies to counter LPI radar.

  4. Oil Slick Characterization Using Synthetic Aperture Radar

    Science.gov (United States)

    Jones, C. E.; Breivik, O.; Brekke, C.; Skrunes, S.; Holt, B.

    2015-12-01

    Oil spills are a hazard worldwide with potential of causing high impact disasters, and require an active oil spill response capability to protect personnel, the ecosystem, and the energy supply. As the amount of oil in traditionally accessible reserves decline, there will be increasing oil extraction from the Arctic and deep-water wells, both new sources with high risk and high cost for monitoring and response. Although radar has long been used for mapping the spatial extent of oil slicks, it is only since the Deepwater Horizon spill that synthetic aperture radar (SAR) has been shown capable of characterizing oil properties within a slick, and therefore useful for directing response to the recoverable thicker slicks or emulsions. Here we discuss a 2015 Norwegian oil-on-water spill experiment in which emulsions of known quantity and water-to-oil ratio along with a look-alike slick of plant oil were released in the North Sea and imaged with polarimetric SAR (PolSAR) by NASA's UAVSAR instrument for several hours following release. During the experiment, extensive in situ measurements were made from ship or aircraft with meteorological instruments, released drift buoys, and optical/IR imagers. The experiment was designed to provide validation data for development of a physical model relating polarization-dependent electromagnetic scattering to the dielectric properties of oil mixed with ocean water, which is the basis for oil characterization with SAR. Data were acquired with X-, C-, and L-band satellite-based SARs to enable multi-frequency comparison of characterization capabilities. In addition, the data are used to develop methods to differentiate mineral slicks from biogenic look-alikes, and to better understand slick weathering and dispersion. The results will provide a basis for modeling oil-in-ice spills, currently a high priority for nations involved in Arctic oil exploration. Here we discuss the Norwegian experiment, the validation data, and the results of

  5. Improving Weather Radar Precipitation Estimates by Combining two Types of Radars

    DEFF Research Database (Denmark)

    Nielsen, Jesper Ellerbæk; Thorndahl, Søren Liedtke; Rasmussen, Michael R.

    2014-01-01

    This paper presents a demonstration of how Local Area Weather Radar (LAWR) X-band measurements can be combined with meteorological C–band measurements into a single radar product. For this purpose, a blending method has been developed which combines the strengths of the two radar systems. Combining...... the two radar types achieves a radar product with both long range and high temporal resolution. It is validated that the blended radar product performs better than the individual radars based on ground observations from laser disdrometers. However, the data combination is challenged by lower performance...... of the LAWR. Although both radars benefits from the data combination, it is also found that advection based temporal interpolation is a more favourable method for increasing the temporal resolution of meteorological C–band measurements....

  6. Radar probing of the auroral plasma

    International Nuclear Information System (INIS)

    Brekke, A.

    1977-01-01

    The European Incoherent Scatter Radar in the Auroral Zone (EISCAT) is an intereuropean organization planning to install an incoherent scatter radar system in Northern Scandinavia. It is supported by Finland, France, Norway, Great Britain, Sweden and West Germany, and its headquarters is in Kiruna, Sweden. The radar is planned to be operating in 1979. In order to introduce students and young scientists to the incoherent scatter radar technique, a summer school was held in Tromsoe, from 5th to 13th June 1975. In these proceedings an introduction to the basic theory of fluctuations in a plasma is given. Some of the present incoherent scatter radars now in use are presented and special considerations with respect to the planned EISACT facility are discussed. Reviews of some recent results and scientific problems relevant to EISCAT are also presented and finally a presentation of some observational techniques complementary to incoherent scatter radars is included. (Ed.)

  7. Structural analysis of lunar subsurface with Chang'E-3 lunar penetrating radar

    Science.gov (United States)

    Lai, Jialong; Xu, Yi; Zhang, Xiaoping; Tang, Zesheng

    2016-01-01

    Geological structure of the subsurface of the Moon provides valuable information on lunar evolution. Recently, Chang'E-3 has utilized lunar penetrating radar (LPR), which is equipped on the lunar rover named as Yutu, to detect the lunar geological structure in Northern Imbrium (44.1260N, 19.5014W) for the first time. As an in situ detector, Chang'E-3 LPR has relative higher horizontal and vertical resolution and less clutter impact compared to spaceborne radars and earth-based radars. In this work, we analyze the LPR data at 500 MHz transmission frequency to obtain the shallow subsurface structure of the landing area of Chang'E-3 in Mare Imbrium. Filter method and amplitude recovery algorithms are utilized to alleviate the adverse effects of environment and system noises and compensate the amplitude losses during signal propagation. Based on the processed radar image, we observe numerous diffraction hyperbolae, which may be caused by discrete reflectors beneath the lunar surface. Hyperbolae fitting method is utilized to reverse the average dielectric constant to certain depth (ε bar). Overall, the estimated ε bar increases with the depth and ε bar could be classified into three categories. Average ε bar of each category is 2.47, 3.40 and 6.16, respectively. Because of the large gap between the values of ε bar of neighboring categories, we speculate a three-layered structure of the shallow surface of LPR exploration region. One possible geological picture of the speculated three-layered structure is presented as follows. The top layer is weathered layer of ejecta blanket with its average thickness and bound on error is 0.95±0.02 m. The second layer is the ejecta blanket of the nearby impact crater, and the corresponding average thickness is about 2.30±0.07 m, which is in good agreement with the two primary models of ejecta blanket thickness as a function of distance from the crater center. The third layer is regarded as a mixture of stones and soil. The

  8. The Comet Radar Explorer Mission

    Science.gov (United States)

    Asphaug, Erik; Belton, Mike; Bockelee-Morvan, Dominique; Chesley, Steve; Delbo, Marco; Farnham, Tony; Gim, Yonggyu; Grimm, Robert; Herique, Alain; Kofman, Wlodek; Oberst, Juergen; Orosei, Roberto; Piqueux, Sylvain; Plaut, Jeff; Robinson, Mark; Sava, Paul; Heggy, Essam; Kurth, William; Scheeres, Dan; Denevi, Brett; Turtle, Elizabeth; Weissman, Paul

    2014-11-01

    Missions to cometary nuclei have revealed major geological surprises: (1) Global scale layers - do these persist through to the interior? Are they a record of primary accretion? (2) Smooth regions - are they landslides originating on the surface? Are they cryovolcanic? (3) Pits - are they impact craters or sublimation pits, or rooted in the interior? Unambiguous answers to these and other questions can be obtained by high definition 3D radar reflection imaging (RRI) of internal structure. RRI can answer many of the great unknowns in planetary science: How do primitive bodies accrete? Are cometary nuclei mostly ice? What drives their spectacular activity and evolution? The Comet Radar Explorer (CORE) mission will image the detailed internal structure of the nucleus of 10P/Tempel 2. This ~16 x 8 x 7 km Jupiter Family Comet (JFC), or its parent body, originated in the outer planets region possibly millions of years before planet formation. CORE arrives post-perihelion and observes the comet’s waning activity from safe distance. Once the nucleus is largely dormant, the spacecraft enters a ~20-km dedicated Radar Mapping Orbit (RMO). The exacting design of the RRI experiment and the precise navigation of RMO will achieve a highly focused 3D radar reflection image of internal structure, to tens of meters resolution, and tomographic images of velocity and attenuation to hundreds of meters resolution, tied to the gravity model and shape. Visible imagers will produce maps of the surface morphology, albedo, color, texture, and photometric response, and images for navigation and shape determination. The cameras will also monitor the structure and dynamics of the coma, and its dusty jets, allowing their correlation in 3D with deep interior structures and surface features. Repeated global high-resolution thermal images will probe the near-surface layers heated by the Sun. Derived maps of thermal inertia will be correlated with the radar boundary response, and photometry and

  9. Radar imaging of Saturn's rings

    Science.gov (United States)

    Nicholson, Philip D.; French, Richard G.; Campbell, Donald B.; Margot, Jean-Luc; Nolan, Michael C.; Black, Gregory J.; Salo, Heikki J.

    2005-09-01

    We present delay-Doppler images of Saturn's rings based on radar observations made at Arecibo Observatory between 1999 and 2003, at a wavelength of 12.6 cm and at ring opening angles of 20.1°⩽|B|⩽26.7°. The average radar cross-section of the A ring is ˜77% relative to that of the B ring, while a stringent upper limit of 3% is placed on the cross-section of the C ring and 9% on that of the Cassini Division. These results are consistent with those obtained by Ostro et al. [1982, Icarus 49, 367-381] from radar observations at |B|=21.4°, but provide higher resolution maps of the rings' reflectivity profile. The average cross-section of the A and B rings, normalized by their projected unblocked area, is found to have decreased from 1.25±0.31 to 0.74±0.19 as the rings have opened up, while the circular polarization ratio has increased from 0.64±0.06 to 0.77±0.06. The steep decrease in cross-section is at variance with previous radar measurements [Ostro et al., 1980, Icarus 41, 381-388], and neither this nor the polarization variations are easily understood within the framework of either classical, many-particle-thick or monolayer ring models. One possible explanation involves vertical size segregation in the rings, whereby observations at larger elevation angles which see deeper into the rings preferentially see the larger particles concentrated near the rings' mid-plane. These larger particles may be less reflective and/or rougher and thus more depolarizing than the smaller ones. Images from all four years show a strong m=2 azimuthal asymmetry in the reflectivity of the A ring, with an amplitude of ±20% and minima at longitudes of 67±4° and 247±4° from the sub-Earth point. We attribute the asymmetry to the presence of gravitational wakes in the A ring as invoked by Colombo et al. [1976, Nature 264, 344-345] to explain the similar asymmetry long seen at optical wavelengths. A simple radiative transfer model suggests that the enhancement of the azimuthal

  10. Corrections for the effects of significant wave height and attitude on Geosat radar altimeter measurements

    Science.gov (United States)

    Hayne, G. S.; Hancock, D. W., III

    1990-01-01

    Range estimates from a radar altimeter have biases which are a function of the significant wave height (SWH) and the satellite attitude angle (AA). Based on results of prelaunch Geosat modeling and simulation, a correction for SWH and AA was already applied to the sea-surface height estimates from Geosat's production data processing. By fitting a detailed model radar return waveform to Geosat waveform sampler data, it is possible to provide independent estimates of the height bias, the SWH, and the AA. The waveform fitting has been carried out for 10-sec averages of Geosat waveform sampler data over a wide range of SWH and AA values. The results confirm that Geosat sea-surface-height correction is good to well within the original dm-level specification, but that an additional height correction can be made at the level of several cm.

  11. Textural features for radar image analysis

    Science.gov (United States)

    Shanmugan, K. S.; Narayanan, V.; Frost, V. S.; Stiles, J. A.; Holtzman, J. C.

    1981-01-01

    Texture is seen as an important spatial feature useful for identifying objects or regions of interest in an image. While textural features have been widely used in analyzing a variety of photographic images, they have not been used in processing radar images. A procedure for extracting a set of textural features for characterizing small areas in radar images is presented, and it is shown that these features can be used in classifying segments of radar images corresponding to different geological formations.

  12. Signal compression in radar using FPGA

    OpenAIRE

    Escamilla Hemández, Enrique; Kravchenko, Víctor; Ponomaryov, Volodymyr; Duchen Sánchez, Gonzalo; Hernández Sánchez, David

    2010-01-01

    We present the hardware implementation of radar real time processing procedures using a simple, fast technique based on FPGA (Field Programmable Gate Array) architecture. This processing includes different window procedures during pulse compression in synthetic aperture radar (SAR). The radar signal compression processing is realized using matched filter, and classical and novel window functions, where we focus on better solution for minimum values of sidelobes. The proposed architecture expl...

  13. Pedestrian recognition using automotive radar sensors

    OpenAIRE

    A. Bartsch; F. Fitzek; R. H. Rasshofer

    2012-01-01

    The application of modern series production automotive radar sensors to pedestrian recognition is an important topic in research on future driver assistance systems. The aim of this paper is to understand the potential and limits of such sensors in pedestrian recognition. This knowledge could be used to develop next generation radar sensors with improved pedestrian recognition capabilities. A new raw radar data signal processing algorithm is proposed that allows deep insight...

  14. Signal-to-solar clutter calculations of AK-47 muzzle flash at various spectral bandpasses near the potassium D1/D2 doublet

    Science.gov (United States)

    Klett, Karl K., Jr.

    2010-04-01

    An analysis was performed, using MODTRAN, to determine the best filters to use for detecting the muzzle flash of an AK-47 in daylight conditions in the desert. Filters with bandwidths of 0.05, 0.1, 0.5, 1.0, 3.0, and 5.0 nanometers (nm) were analyzed to understand how the optical bandwidth affects the signal-to-solar clutter ratio. These filters were evaluated near the potassium D1 and D2 doublet emission lines that occur at 769.89 and 766.49 nm respectively that are observed where projectile propellants are used. The maximum spectral radiance, from the AK-47 muzzle flash, is 1.88 x 10-2 W/cm2 str micron, and is approximately equal to the daytime atmospheric spectral radiance. The increased emission, due to the potassium doublet lines, and decreased atmospheric transmission, due to oxygen absorption, combine to create a condition where the signal-to-solar clutter ratio is greater than 1. The 3 nm filter, has a signal-to-solar clutter ratio of 2.09 when centered at 765.37 nm and provides the best combination of both cost and signal sensitivity.

  15. Radar reflection off extensive air showers

    Directory of Open Access Journals (Sweden)

    Werner F.

    2013-06-01

    Full Text Available We investigate the possibility of detecting extensive air showers by the radar technique. Considering a bistatic radar system and different shower geometries, we simulate reflection of radio waves off the static plasma produced by the shower in the air. Using the Thomson cross-section for radio wave reflection, we obtain the time evolution of the signal received by the antennas. The frequency upshift of the radar echo and the power received are studied to verify the feasibility of the radar detection technique.

  16. Reduction and coding of synthetic aperture radar data with Fourier transforms

    Science.gov (United States)

    Tilley, David G.

    1995-01-01

    Recently, aboard the Space Radar Laboratory (SRL), the two roles of Fourier Transforms for ocean image synthesis and surface wave analysis have been implemented with a dedicated radar processor to significantly reduce Synthetic Aperture Radar (SAR) ocean data before transmission to the ground. The object was to archive the SAR image spectrum, rather than the SAR image itself, to reduce data volume and capture the essential descriptors of the surface wave field. SAR signal data are usually sampled and coded in the time domain for transmission to the ground where Fourier Transforms are applied both to individual radar pulses and to long sequences of radar pulses to form two-dimensional images. High resolution images of the ocean often contain no striking features and subtle image modulations by wind generated surface waves are only apparent when large ocean regions are studied, with Fourier transforms, to reveal periodic patterns created by wind stress over the surface wave field. Major ocean currents and atmospheric instability in coastal environments are apparent as large scale modulations of SAR imagery. This paper explores the possibility of computing complex Fourier spectrum codes representing SAR images, transmitting the coded spectra to Earth for data archives and creating scenes of surface wave signatures and air-sea interactions via inverse Fourier transformations with ground station processors.

  17. Specification for a surface-search radar-detection-range model

    Science.gov (United States)

    Hattan, Claude P.

    1990-09-01

    A model that predicts surface-search radar detection range versus a variety of combatants has been developed at the Naval Ocean Systems Center. This model uses a simplified ship radar cross section (RCS) model and the U.S. Navy Oceanographic and Atmospheric Mission Library Standard Electromagnetic Propagation Model. It provides the user with a method of assessing the effects of the environment of the performance of a surface-search radar system. The software implementation of the model is written in ANSI FORTRAN 77, with MIL-STD-1753 extensions. The program provides the user with a table of expected detection ranges when the model is supplied with the proper environmental radar system inputs. The target model includes the variation in RCS as a function of aspect angle and the distribution of reflected radar energy as a function of height above the waterline. The modeled propagation effects include refraction caused by a multisegmented refractivity profile, sea-surface roughness caused by local winds, evaporation ducting, and surface-based ducts caused by atmospheric layering.

  18. Annual Greenland Accumulation Rates (2009-2012) from Airborne Snow Radar

    Science.gov (United States)

    Koenig, Lora S.; Ivanoff, Alvaro; Alexander, Patrick M.; MacGregor, Joseph A.; Fettweis, Xavier; Panzer, Ben; Paden, John D.; Forster, Richard R.; Das, Indrani; McConnell, Joseph R.; hide

    2016-01-01

    Contemporary climate warming over the Arctic is accelerating mass loss from the Greenland Ice Sheet through increasing surface melt, emphasizing the need to closely monitor its surface mass balance in order to improve sea-level rise predictions. Snow accumulation is the largest component of the ice sheet's surface mass balance, but in situ observations thereof are inherently sparse and models are difficult to evaluate at large scales. Here, we quantify recent Greenland accumulation rates using ultra-wideband (2-6.5 gigahertz) airborne snow radar data collected as part of NASA's Operation IceBridge between 2009 and 2012. We use a semi-automated method to trace the observed radiostratigraphy and then derive annual net accumulation rates for 2009-2012. The uncertainty in these radar-derived accumulation rates is on average 14 percent. A comparison of the radarderived accumulation rates and contemporaneous ice cores shows that snow radar captures both the annual and longterm mean accumulation rate accurately. A comparison with outputs from a regional climate model (MAR - Modele Atmospherique Regional for Greenland and vicinity) shows that this model matches radar-derived accumulation rates in the ice sheet interior but produces higher values over southeastern Greenland. Our results demonstrate that snow radar can efficiently and accurately map patterns of snow accumulation across an ice sheet and that it is valuable for evaluating the accuracy of surface mass balance models.

  19. Dependency of human target detection performance on clutter and quality of supporting image analysis algorithms in a video surveillance task

    Science.gov (United States)

    Huber, Samuel; Dunau, Patrick; Wellig, Peter; Stein, Karin

    2017-10-01

    Background: In target detection, the success rates depend strongly on human observer performances. Two prior studies tested the contributions of target detection algorithms and prior training sessions. The aim of this Swiss-German cooperation study was to evaluate the dependency of human observer performance on the quality of supporting image analysis algorithms. Methods: The participants were presented 15 different video sequences. Their task was to detect all targets in the shortest possible time. Each video sequence showed a heavily cluttered simulated public area from a different viewing angle. In each video sequence, the number of avatars in the area was altered to 100, 150 and 200 subjects. The number of targets appearing was kept at 10%. The number of marked targets varied from 0, 5, 10, 20 up to 40 marked subjects while keeping the positive predictive value of the detection algorithm at 20%. During the task, workload level was assessed by applying an acoustic secondary task. Detection rates and detection times for the targets were analyzed using inferential statistics. Results: The study found Target Detection Time to increase and Target Detection Rates to decrease with increasing numbers of avatars. The same is true for the Secondary Task Reaction Time while there was no effect on Secondary Task Hit Rate. Furthermore, we found a trend for a u-shaped correlation between the numbers of markings and RTST indicating increased workload. Conclusion: The trial results may indicate useful criteria for the design of training and support of observers in observational tasks.

  20. Scattering from extended targets in range-dependent fluctuating ocean-waveguides with clutter from theory and experiments.

    Science.gov (United States)

    Jagannathan, Srinivasan; Küsel, Elizabeth T; Ratilal, Purnima; Makris, Nicholas C

    2012-08-01

    Bistatic, long-range measurements of acoustic scattered returns from vertically extended, air-filled tubular targets were made during three distinct field experiments in fluctuating continental shelf waveguides. It is shown that Sonar Equation estimates of mean target-scattered intensity lead to large errors, differing by an order of magnitude from both the measurements and waveguide scattering theory. The use of the Ingenito scattering model is also shown to lead to significant errors in estimating mean target-scattered intensity in the field experiments because they were conducted in range-dependent ocean environments with large variations in sound speed structure over the depth of the targets, scenarios that violate basic assumptions of the Ingenito model. Green's theorem based full-field modeling that describes scattering from vertically extended tubular targets in range-dependent ocean waveguides by taking into account nonuniform sound speed structure over the target's depth extent is shown to accurately describe the statistics of the targets' scattered field in all three field experiments. Returns from the man-made targets are also shown to have a very different spectral dependence from the natural target-like clutter of the dominant fish schools observed, suggesting that judicious multi-frequency sensing may often provide a useful means of distinguishing fish from man-made targets.

  1. Robust frequency diversity based algorithm for clutter noise reduction of ultrasonic signals using multiple sub-spectrum phase coherence

    Energy Technology Data Exchange (ETDEWEB)

    Gongzhang, R.; Xiao, B.; Lardner, T.; Gachagan, A. [Centre for Ultrasonic Engineering, University of Strathclyde, Glasgow, G1 1XW (United Kingdom); Li, M. [School of Engineering, University of Glasgow, Glasgow, G12 8QQ (United Kingdom)

    2014-02-18

    This paper presents a robust frequency diversity based algorithm for clutter reduction in ultrasonic A-scan waveforms. The performance of conventional spectral-temporal techniques like Split Spectrum Processing (SSP) is highly dependent on the parameter selection, especially when the signal to noise ratio (SNR) is low. Although spatial beamforming offers noise reduction with less sensitivity to parameter variation, phased array techniques are not always available. The proposed algorithm first selects an ascending series of frequency bands. A signal is reconstructed for each selected band in which a defect is present when all frequency components are in uniform sign. Combining all reconstructed signals through averaging gives a probability profile of potential defect position. To facilitate data collection and validate the proposed algorithm, Full Matrix Capture is applied on the austenitic steel and high nickel alloy (HNA) samples with 5MHz transducer arrays. When processing A-scan signals with unrefined parameters, the proposed algorithm enhances SNR by 20dB for both samples and consequently, defects are more visible in B-scan images created from the large amount of A-scan traces. Importantly, the proposed algorithm is considered robust, while SSP is shown to fail on the austenitic steel data and achieves less SNR enhancement on the HNA data.

  2. Information-Aided Smart Schemes for Vehicle Flow Detection Enhancements of Traffic Microwave Radar Detectors

    Directory of Open Access Journals (Sweden)

    Tan-Jan Ho

    2016-07-01

    Full Text Available For satisfactory traffic management of an intelligent transport system, it is vital that traffic microwave radar detectors (TMRDs can provide real-time traffic information with high accuracy. In this study, we develop several information-aided smart schemes for traffic detection improvements of TMRDs in multiple-lane environments. Specifically, we select appropriate thresholds not only for removing noise from fast Fourier transforms (FFTs of regional lane contexts but also for reducing FFT side lobes within each lane. The resulting FFTs of reflected vehicle signals and those of clutter are distinguishable. We exploit FFT and lane-/or time stamp-related information for developing smart schemes, which mitigate adverse effects of lane-crossing FFT side lobes of a vehicle signal. As such, the proposed schemes can enhance the detection accuracy of both lane vehicle flow and directional traffic volume. On-site experimental results demonstrate the advantages and feasibility of the proposed methods, and suggest the best smart scheme.

  3. Full Waveform Analysis for Long-Range 3D Imaging Laser Radar

    Directory of Open Access Journals (Sweden)

    Wallace AndrewM

    2010-01-01

    Full Text Available The new generation of 3D imaging systems based on laser radar (ladar offers significant advantages in defense and security applications. In particular, it is possible to retrieve 3D shape information directly from the scene and separate a target from background or foreground clutter by extracting a narrow depth range from the field of view by range gating, either in the sensor or by postprocessing. We discuss and demonstrate the applicability of full-waveform ladar to produce multilayer 3D imagery, in which each pixel produces a complex temporal response that describes the scene structure. Such complexity caused by multiple and distributed reflection arises in many relevant scenarios, for example in viewing partially occluded targets, through semitransparent materials (e.g., windows and through distributed reflective media such as foliage. We demonstrate our methodology on 3D image data acquired by a scanning time-of-flight system, developed in our own laboratories, which uses the time-correlated single-photon counting technique.

  4. PAPR-Constrained Pareto-Optimal Waveform Design for OFDM-STAP Radar

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Satyabrata [ORNL

    2014-01-01

    We propose a peak-to-average power ratio (PAPR) constrained Pareto-optimal waveform design approach for an orthogonal frequency division multiplexing (OFDM) radar signal to detect a target using the space-time adaptive processing (STAP) technique. The use of an OFDM signal does not only increase the frequency diversity of our system, but also enables us to adaptively design the OFDM coefficients in order to further improve the system performance. First, we develop a parametric OFDM-STAP measurement model by considering the effects of signaldependent clutter and colored noise. Then, we observe that the resulting STAP-performance can be improved by maximizing the output signal-to-interference-plus-noise ratio (SINR) with respect to the signal parameters. However, in practical scenarios, the computation of output SINR depends on the estimated values of the spatial and temporal frequencies and target scattering responses. Therefore, we formulate a PAPR-constrained multi-objective optimization (MOO) problem to design the OFDM spectral parameters by simultaneously optimizing four objective functions: maximizing the output SINR, minimizing two separate Cramer-Rao bounds (CRBs) on the normalized spatial and temporal frequencies, and minimizing the trace of CRB matrix on the target scattering coefficients estimations. We present several numerical examples to demonstrate the achieved performance improvement due to the adaptive waveform design.

  5. Fast comparison of IS radar code sequences for lag profile inversion

    Directory of Open Access Journals (Sweden)

    M. S. Lehtinen

    2008-08-01

    Full Text Available A fast method for theoretically comparing the posteriori variances produced by different phase code sequences in incoherent scatter radar (ISR experiments is introduced. Alternating codes of types 1 and 2 are known to be optimal for selected range resolutions, but the code sets are inconveniently long for many purposes like ground clutter estimation and in cases where coherent echoes from lower ionospheric layers are to be analyzed in addition to standard F-layer spectra.

    The method is used in practice for searching binary code quads that have estimation accuracy almost equal to that of much longer alternating code sets. Though the code sequences can consist of as few as four different transmission envelopes, the lag profile estimation variances are near to the theoretical minimum. Thus the short code sequence is equally good as a full cycle of alternating codes with the same pulse length and bit length. The short code groups cannot be directly decoded, but the decoding is done in connection with more computationally expensive lag profile inversion in data analysis.

    The actual code searches as well as the analysis and real data results from the found short code searches are explained in other papers sent to the same issue of this journal. We also discuss interesting subtle differences found between the different alternating codes by this method. We assume that thermal noise dominates the incoherent scatter signal.

  6. Ship Detection and Measurement of Ship Motion by Multi-Aperture Synthetic Aperture Radar

    Science.gov (United States)

    2014-06-01

    otherwise they would break. Both transverse and torsional modes are present and are driven by the ship structure, the shape of the sea surface, bow slamming...used, the ship’s loading and the ship’s operation [11], [16]. Very large vessels are the most flexible . The schematic shown in Figure 4 [12] provides...different orientations and thin (with respect to a radar wavelength) rods and cables act as linear diffraction centers. The orientation of the

  7. Sea Dragon

    National Research Council Canada - National Science Library

    1997-01-01

    .... In preparation for these changes, the Navy is exploring new command and control relationships, and the Marine Corps established Sea Dragon to experiment with emerging technologies, operational...

  8. Radar network communication through sensing of frequency hopping

    Science.gov (United States)

    Dowla, Farid; Nekoogar, Faranak

    2013-05-28

    In one embodiment, a radar communication system includes a plurality of radars having a communication range and being capable of operating at a sensing frequency and a reporting frequency, wherein the reporting frequency is different than the sensing frequency, each radar is adapted for operating at the sensing frequency until an event is detected, each radar in the plurality of radars has an identification/location frequency for reporting information different from the sensing frequency, a first radar of the radars which senses the event sends a reporting frequency corresponding to its identification/location frequency when the event is detected, and all other radars in the plurality of radars switch their reporting frequencies to match the reporting frequency of the first radar upon detecting the reporting frequency switch of a radar within the communication range. In another embodiment, a method is presented for communicating information in a radar system.

  9. The NASA radar entomology program at Wallops Flight Center

    Science.gov (United States)

    Vaughn, C. R.

    1979-01-01

    NASA contribution to radar entomology is presented. Wallops Flight Center is described in terms of its radar systems. Radar tracking of birds and insects was recorded from helicopters for airspeed and vertical speed.

  10. Detection of oil spills near offshore installations using synthetic aperture radar (SAR)

    International Nuclear Information System (INIS)

    Espedal, H.A.; Johannessen, O.M.

    2000-01-01

    Remote sensing using synthetic aperture radar (SAR) is attracting increasing interest for the detection of oil spills from offshore oil installations. Three systems are already operating and three more are planned. SAR can provide high spatial resolution and is not affected by the time of day or cloud conditions. Examples of images obtained from UK and Norwegian offshore installations are shown and their interpretation are explained. SAR image analysis is used by a satellite-based oil spill monitoring service covering the Norwegian sector of the North Sea and part of the North Sea, the Norwegian Sea and the Baltic Sea. An algorithm has been developed at the Nansen Environmental and Remote Sensing Centre (NERSC) in Norway to help distinguish between oil spills, natural films, current shear zones and rain cells

  11. Method for radar detection of persons wearing wires

    OpenAIRE

    Fox, William P.

    2014-01-01

    8,730,098 B1 Methods are described for radar detection of persons wearing wires using radar spectra data including the vertical polarization (VV) radar cross section and the horizontal polarization (HH) radar cross section for a person. In one embodiment, the ratio of the vertical polarization (VV) radar cross section to the horizontal polarization (HH) radar cross section for a person is compared to a detection threshold to determine whether the person is wearing wire...

  12. An X-Band Radar System for Bathymetry and Wave Field Analysis in a Harbour Area

    Directory of Open Access Journals (Sweden)

    Giovanni Ludeno

    2015-01-01

    Full Text Available Marine X-band radar based systems are well tested to provide information about sea state and bathymetry. It is also well known that complex geometries and non-uniform bathymetries provide a much bigger challenge than offshore scenarios. In order to tackle this issue a retrieval method is proposed, based on spatial partitioning of the data and the application of the Normalized Scalar Product (NSP, which is an innovative procedure for the joint estimation of bathymetry and surface currents. The strategy is then applied to radar data acquired around a harbour entrance, and results show that the reconstructed bathymetry compares well with ground truth data obtained by an echo-sounder campaign, thus proving the reliability of the whole procedure. The spectrum thus retrieved is then analysed to show the evidence of reflected waves from the harbour jetties, as confirmed by chain of hydrodynamic models of the sea wave field. The possibility of using a land based radar to reveal sea wave reflection is entirely new and may open up new operational applications of the system.

  13. Array-Based Ultrawideband through-Wall Radar: Prediction and Assessment of Real Radar Abilities

    Directory of Open Access Journals (Sweden)

    Nadia Maaref

    2013-01-01

    Full Text Available This paper deals with a new through-the-wall (TTW radar demonstrator for the detection and the localisation of people in a room (in a noncooperative way with the radar situated outside but in the vicinity of the first wall. After modelling the propagation through various walls and quantifying the backscattering by the human body, an analysis of the technical considerations which aims at defining the radar design is presented. Finally, an ultrawideband (UWB frequency modulated continuous wave (FMCW radar is proposed, designed, and implemented. Some representative trials show that this radar is able to localise and track moving people behind a wall in real time.

  14. Pocket radar guide key facts, equations, and data

    CERN Document Server

    Curry, G Richard

    2010-01-01

    ThePocket Radar Guideis a concise collection of key radar facts and important radar data that provides you with necessary radar information when you are away from your office or references. It includes statements and comments on radar design, operation, and performance; equations describing the characteristics and performance of radar systems and their components; and tables with data on radar characteristics and key performance issues.It is intended to supplement other radar information sources by providing a pocket companion to refresh memory and provide details whenever you need them such a

  15. Customizable Digital Receivers for Radar

    Science.gov (United States)

    Moller, Delwyn; Heavey, Brandon; Sadowy, Gregory

    2008-01-01

    Compact, highly customizable digital receivers are being developed for the system described in 'Radar Interferometer for Topographic Mapping of Glaciers and Ice Sheets' (NPO-43962), NASA Tech Briefs, Vol. 31, No. 7 (August 2007), page 72. The receivers are required to operate in unison, sampling radar returns received by the antenna elements in a digital beam-forming (DBF) mode. The design of these receivers could also be adapted to commercial radar systems. At the time of reporting the information for this article, there were no commercially available digital receivers capable of satisfying all of the operational requirements and compact enough to be mounted directly on the antenna elements. A provided figure depicts the overall system of which the digital receivers are parts. Each digital receiver includes an analog-to-digital converter (ADC), a demultiplexer (DMUX), and a field-programmable gate array (FPGA). The ADC effects 10-bit band-pass sampling of input signals having frequencies up to 3.5 GHz. The input samples are demultiplexed at a user-selectable rate of 1:2 or 1:4, then buffered in part of the FPGA that functions as a first-in/first-out (FIFO) memory. Another part of the FPGA serves as a controller for the ADC, DMUX, and FIFO memory and as an interface between (1) the rest of the receiver and (2) a front-panel data port (FPDP) bus, which is an industry-standard parallel data bus that has a high data-rate capability and multichannel configuration suitable for DBF. Still other parts of the FPGA in each receiver perform signal-processing functions. The digital receivers can be configured to operate in a stand-alone mode, or in a multichannel mode as needed for DBF. The customizability of the receiver makes it applicable to a broad range of system architectures. The capability for operation of receivers in either a stand-alone or a DBF mode enables the use of the receivers in an unprecedentedly wide variety of radar systems.

  16. Visual Attention to Radar Displays

    Science.gov (United States)

    Moray, N.; Richards, M.; Brophy, C.

    1984-01-01

    A model is described which predicts the allocation of attention to the features of a radar display. It uses the growth of uncertainty and the probability of near collision to call the eye to a feature of the display. The main source of uncertainty is forgetting following a fixation, which is modelled as a two dimensional diffusion process. The model was used to predict information overload in intercept controllers, and preliminary validation obtained by recording eye movements of intercept controllers in simulated and live (practice) interception.

  17. Radar Methods in Urban Environments

    Science.gov (United States)

    2016-10-26

    and A. Nehorai, "A low-complexity multi-target tracking algorithm in urban environments using sparse modeling ,’’ Signal Processing, Vol. 92, pp. 2199...AFRL-AFOSR-VA-TR-2016-0344 Radar Methods in Urban Environments Arye Nehorai WASHINGTON UNIVERSITY THE Final Report 10/26/2016 DISTRIBUTION A...of information   if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ORGANIZATION . 1. REPORT DATE

  18. RADARSAT-1 synthetic aperture radar analysis

    Energy Technology Data Exchange (ETDEWEB)

    Simecek-Beatty, D. [National Oceanic and Atmospheric Adminstration, National Ocean Service, Seattle, WA (United States). Office of Response and Restoration; Pichel, W.G. [National Oceanic and Atmospheric Administration, National Environmental Satellite, Data and Information Service, Camp Springs, MD (United States). Office of Research and Applications

    2006-07-01

    The M/V Selendang Ayu grounded off Unalaska Island in Alaska on December 8, 2004, and spilled over 1270 m{sup 3} of oil and an unknown quantity of soybeans. The freighter grounded nearshore in a high-wave energy zone along a remote and rugged coastline, a terrain which can cause difficulties for remote sensors in detecting oil slicks. In addition, guano, kelp beds, whale and fish sperm, and releases from fishing activities generated biogenic films on the sea surface that had a signature similar to that of petroleum films. RADARSAT-1 synthetic aperture radar (SAR) imagery was used as part of the response effort to assist in the pollution monitoring effort. This paper described the methodology and results of the RADARSAT-1 analysis. Detailed information on the spill response was reported daily, and provided an opportunity to compare field observations with RADARSAT-1 SAR imagery. Observers recorded observations onto electronic maps during 35 aerial surveillance flights. Fifty-seven incident reports describing the vessel status were also used for comparison. Using screening criteria for the favorable wind and wave conditions, 37 images were available for viewing the wreck, and 22 images were acceptable for oil slick viewing. Image analysis for the wreck suggested that the sensor has the resolution and capability to monitor a grounded freighter. Visual inspection of the images showed that SAR can capture changes in vessel status, such as the gradual sinking of the bow. However, SAR's oil slick detection capability was disappointing due to the significant number of biogenic films in the nearshore areas of Alaska. It was concluded that future work should concentrate on developing a ranking system to indicate analysis confidence that a particular image does in fact contain a petroleum pocket. 25 refs., 2 tabs., 10 figs.

  19. SeaWinds - Oceans, Land, Polar Regions

    Science.gov (United States)

    1999-01-01

    The SeaWinds scatterometer on the QuikScat satellite makes global radar measurements -- day and night, in clear sky and through clouds. The radar data over the oceans provide scientists and weather forecasters with information on surface wind speed and direction. Scientists also use the radar measurements directly to learn about changes in vegetation and ice extent over land and polar regions.This false-color image is based entirely on SeaWinds measurements obtained over oceans, land, and polar regions. Over the ocean, colors indicate wind speed with orange as the fastest wind speeds and blue as the slowest. White streamlines indicate the wind direction. The ocean winds in this image were measured by SeaWinds on September 20, 1999. The large storm in the Atlantic off the coast of Florida is Hurricane Gert. Tropical storm Harvey is evident as a high wind region in the Gulf of Mexico, while farther west in the Pacific is tropical storm Hilary. An extensive storm is also present in the South Atlantic Ocean near Antarctica.The land image was made from four days of SeaWinds data with the aid of a resolution enhancement algorithm developed by Dr. David Long at Brigham Young University. The lightest green areas correspond to the highest radar backscatter. Note the bright Amazon and Congo rainforests compared to the dark Sahara desert. The Amazon River is visible as a dark line running horizontally though the bright South American rain forest. Cities appear as bright spots on the images, especially in the U.S. and Europe.The image of Greenland and the north polar ice cap was generated from data acquired by SeaWinds on a single day. In the polar region portion of the image, white corresponds to the largest radar return, while purple is the lowest. The variations in color in Greenland and the polar ice cap reveal information about the ice and snow conditions present.NASA's Earth Science Enterprise is a long-term research and technology program designed to examine Earth

  20. Ultra-wideband radar sensors and networks

    Science.gov (United States)

    Leach, Jr., Richard R; Nekoogar, Faranak; Haugen, Peter C

    2013-08-06

    Ultra wideband radar motion sensors strategically placed in an area of interest communicate with a wireless ad hoc network to provide remote area surveillance. Swept range impulse radar and a heart and respiration monitor combined with the motion sensor further improves discrimination.