Science.gov

Sample records for synthetic aperture radar

  1. SEASAT Synthetic Aperture Radar Data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M.

    1981-01-01

    The potential of radar imagery from space altitudes is discussed and the advantages of radar over passive sensor systems are outlined. Specific reference is made to the SEASAT synthetic aperture radar. Possible applications include oil spill monitoring, snow and ice reconnaissance, mineral exploration, and monitoring phenomena in the urban environment.

  2. Bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Yates, Gillian

    Synthetic aperture radar (SAR) allows all-weather, day and night, surface surveillance and has the ability to detect, classify and geolocate objects at long stand-off ranges. Bistatic SAR, where the transmitter and the receiver are on separate platforms, is seen as a potential means of countering the vulnerability of conventional monostatic SAR to electronic countermeasures, particularly directional jamming, and avoiding physical attack of the imaging platform. As the receiving platform can be totally passive, it does not advertise its position by RF emissions. The transmitter is not susceptible to jamming and can, for example, operate at long stand-off ranges to reduce its vulnerability to physical attack. This thesis examines some of the complications involved in producing high-resolution bistatic SAR imagery. The effect of bistatic operation on resolution is examined from a theoretical viewpoint and analytical expressions for resolution are developed. These expressions are verified by simulation work using a simple 'point by point' processor. This work is extended to look at using modern practical processing engines for bistatic geometries. Adaptations of the polar format algorithm and range migration algorithm are considered. The principal achievement of this work is a fully airborne demonstration of bistatic SAR. The route taken in reaching this is given, along with some results. The bistatic SAR imagery is analysed and compared to the monostatic imagery collected at the same time. Demonstrating high-resolution bistatic SAR imagery using two airborne platforms represents what I believe to be a European first and is likely to be the first time that this has been achieved outside the US (the UK has very little insight into US work on this topic). Bistatic target characteristics are examined through the use of simulations. This also compares bistatic imagery with monostatic and gives further insight into the utility of bistatic SAR.

  3. Future of synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Barath, F. T.

    1978-01-01

    The present status of the applications of Synthetic Aperture Radars (SARs) is reviewed, and the technology state-of-the art as represented by the Seasat-A and SIR-A SARs examined. The potential of SAR applications, and the near- and longer-term technology trends are assessed.

  4. Imaging synthetic aperture radar

    DOEpatents

    Burns, Bryan L.; Cordaro, J. Thomas

    1997-01-01

    A linear-FM SAR imaging radar method and apparatus to produce a real-time image by first arranging the returned signals into a plurality of subaperture arrays, the columns of each subaperture array having samples of dechirped baseband pulses, and further including a processing of each subaperture array to obtain coarse-resolution in azimuth, then fine-resolution in range, and lastly, to combine the processed subapertures to obtain the final fine-resolution in azimuth. Greater efficiency is achieved because both the transmitted signal and a local oscillator signal mixed with the returned signal can be varied on a pulse-to-pulse basis as a function of radar motion. Moreover, a novel circuit can adjust the sampling location and the A/D sample rate of the combined dechirped baseband signal which greatly reduces processing time and hardware. The processing steps include implementing a window function, stabilizing either a central reference point and/or all other points of a subaperture with respect to doppler frequency and/or range as a function of radar motion, sorting and compressing the signals using a standard fourier transforms. The stabilization of each processing part is accomplished with vector multiplication using waveforms generated as a function of radar motion wherein these waveforms may be synthesized in integrated circuits. Stabilization of range migration as a function of doppler frequency by simple vector multiplication is a particularly useful feature of the invention; as is stabilization of azimuth migration by correcting for spatially varying phase errors prior to the application of an autofocus process.

  5. Frequency agile synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Wehner, Donald R.

    1989-07-01

    A radar transmission, reception and signal processing system generates high resolution synthetic aperture radar ground maps from air or space platforms using waveforms in which frequency is changed pulse-to-pulse. The transmitted radar signal is comprised of a series N bursts with n pulses per burst wherein each of the pulsed is a fixed frequency step, delta f either above or below one or the other of the n pulses, i.e., the n pulses comprises an ordered set and further, preferably, wherein the set of n pulses is arranged in time as a random permutation of the ordered set. In each of the k sample gates for each burst the n complex samples of reflectivity are inverse Fourier transformed from frequency domain samples of reflectivity to synthetic range domain profiles to result in an array of aligned range profiles in each of k coarse range delay positions. Azimuth or cross-range processing is accomplished by thetic range cell with a suitable azimuth reference to result in a set of complex numbers that represent complex reflectivity maps of the earth's surface in that coarse range bin.

  6. Distributed synthetic aperture radar simulation

    NASA Technical Reports Server (NTRS)

    Bourgeois, B. A.

    1986-01-01

    Synthetic aperture radar (SAR) depends primarily on attainable frequency resolution rather than on large physical size of the antenna array. The distributed architecture concept (DSAR) incorporates active elements (amplifiers) at or near the elemental radiators of the array. Since SAR's are expensive to build and expensive to test, a computer modeling approach is a feasible method of predicting the quality or nature of the SAR image from the proposed system parameters. The goal of this project is to produce a DSAR simulation software package. This report describes the progress made thus far and the work which remains to be done. Extensive work on this project had been done previously by two NASA contractors. The principal task remaining involved the creation of a suitable interface between these programs and the hardware and software available at the Johnson Space Center.

  7. Differential Optical Synthetic Aperture Radar

    DOEpatents

    Stappaerts, Eddy A.

    2005-04-12

    A new differential technique for forming optical images using a synthetic aperture is introduced. This differential technique utilizes a single aperture to obtain unique (N) phases that can be processed to produce a synthetic aperture image at points along a trajectory. This is accomplished by dividing the aperture into two equal "subapertures", each having a width that is less than the actual aperture, along the direction of flight. As the platform flies along a given trajectory, a source illuminates objects and the two subapertures are configured to collect return signals. The techniques of the invention is designed to cancel common-mode errors, trajectory deviations from a straight line, and laser phase noise to provide the set of resultant (N) phases that can produce an image having a spatial resolution corresponding to a synthetic aperture.

  8. Synthetic aperture radar capabilities in development

    SciTech Connect

    Miller, M.

    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.

  9. Exploiting Decorrelations In Synthetic-Aperture Radar

    NASA Technical Reports Server (NTRS)

    Zebker, Howard A.; Villasenor, John D.

    1994-01-01

    Temporal decorrelation between synthetic-aperture-radar data acquired on subsequent passes along same or nearly same trajectory serves as measure of change in target scene. Based partly on mathematical models of statistics of correlations between first- and second-pass radar echoes. Also based partly on Fourier-transform relations between radar-system impulse response and decorrelation functions particularly those expressing decorrelation effects of rotation and horizontal shift of trajectories between two passes.

  10. Multibeam synthetic aperture radar for global oceanography

    NASA Technical Reports Server (NTRS)

    Jain, A.

    1979-01-01

    A single-frequency multibeam synthetic aperture radar concept for large swath imaging desired for global oceanography is evaluated. Each beam iilluminates a separate range and azimuth interval, and images for different beams may be separated on the basis of the Doppler spectrum of the beams or their spatial azimuth separation in the image plane of the radar processor. The azimuth resolution of the radar system is selected so that the Doppler spectrum of each beam does not interfere with the Doppler foldover due to the finite pulse repetition frequency of the radar system.

  11. Processing for spaceborne synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Lybanon, M.

    1973-01-01

    The data handling and processing in using synthetic aperture radar as a satellite-borne earth resources remote sensor is considered. The discussion covers the nature of the problem, the theory, both conventional and potential advanced processing techniques, and a complete computer simulation. It is shown that digital processing is a real possibility and suggests some future directions for research.

  12. Addressing Three Fallacies About Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Atwood, Don; Garron, Jessica

    2013-12-01

    Synthetic aperture radar (SAR) has long been recognized as a valuable tool for real-time environmental analysis and understanding of the Earth's geophysical properties. With its ability to see through clouds and to image day and night in all seasons, it can provide high-resolution data when optical sensors cannot. This capability has enabled SAR scientists to delineate flooding events, assess earthquake damage, map forest fires, rescue trapped icebreakers, and identify the extent of oil spills.

  13. Estimating vegetation biomass using synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Baronti, Stefano; Luciani, S.; Paloscia, Simonetta; Schiavon, G.; Sigismondi, S.; Solimini, Domenico

    1994-12-01

    A significant experiment for evaluating the potential of Synthetic Aperture Radar (SAR) in monitoring soil and vegetation parameters is being carried out on an agricultural area located in Central Italy. The site has been imaged in 1991 by NASA/JPL AIRSAR during the MAC-91 Campaign and subsequently by ESA/ERS-1 and NASDA JERS-1 in 1992. The sensitivity to vegetation biomass of backscattering coefficient measured by ERS-1 and JERS-1 radars is discussed and compared with the best results achieved using the multifrequency polarimetric AIRSAR data.

  14. Performance limits for Synthetic Aperture Radar.

    SciTech Connect

    Doerry, Armin Walter

    2006-02-01

    The performance of a Synthetic Aperture Radar (SAR) 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, no matter how bright the engineer tasked to generate a system design. 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 SAR system. For example, there are definite optimum frequency bands that depend on weather conditions and range, and minimum radar PRF for a fixed real antenna aperture dimension is independent of frequency. 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''.

  15. Nonlinear synthetic aperture radar imaging using a harmonic radar

    NASA Astrophysics Data System (ADS)

    Gallagher, Kyle A.; Mazzaro, Gregory J.; Ranney, Kenneth I.; Nguyen, Lam H.; Martone, Anthony F.; Sherbondy, Kelly D.; Narayanan, Ram M.

    2015-05-01

    This paper presents synthetic aperture radar (SAR) images of linear and nonlinear targets. Data are collected using a linear/nonlinear step frequency radar. We show that it is indeed possible to produce SAR images using a nonlinear radar. Furthermore, it is shown that the nonlinear radar is able to reduce linear clutter by at least 80 dB compared to a linear radar. The nonlinear SAR images also show the system's ability to detect small electronic devices in the presence of large linear clutter. The system presented here has the ability to completely ignore a 20-inch trihedral corner reflector while detecting a RF mixer with a dipole antenna attached.

  16. Soviet oceanographic synthetic aperture radar (SAR) research

    SciTech Connect

    Held, D.N.; Gasparovic, R.F.; Mansfield, A.W.; Melville, W.K.; Mollo-Christensen, E.L.; Zebker, H.A.

    1991-01-01

    Radar non-acoustic anti-submarine warfare (NAASW) became the subject of considerable scientific investigation and controversy in the West subsequent to the discovery by the Seasat satellite in 1978 that manifestations of underwater topography, thought to be hidden from the radar, were visible in synthetic aperture radar (SAR) images of the ocean. In addition, the Seasat radar produced images of ship wakes where the observed angle between the wake arms was much smaller than expected from classical Kelvin wake theory. These observations cast doubt on the radar oceanography community's ability to adequately explain these phenomena, and by extension on the ability of existing hydrodynamic and radar scattering models to accurately predict the observability of submarine-induced signatures. If one is of the opinion that radar NAASW is indeed a potentially significant tool in detecting submerged operational submarines, then the Soviet capability, as evidenced throughout this report, will be somewhat daunting. It will be shown that the Soviets have extremely fine capabilities in both theoretical and experimental hydrodynamics, that Soviet researchers have been conducting at-sea radar remote sensing experiments on a scale comparable to those of the United States for several years longer than we have, and that they have both an airborne and spaceborne SAR capability. The only discipline that the Soviet Union appears to be lacking is in the area of digital radar signal processing. If one is of the opinion that radar NAASW can have at most a minimal impact on the detection of submerged submarines, then the Soviet effort is of little consequence and poses not threat. 280 refs., 31 figs., 12 tabs.

  17. Lossless compression of synthetic aperture radar images

    SciTech Connect

    Ives, R.W.; Magotra, N.; Mandyam, G.D.

    1996-02-01

    Synthetic Aperture Radar (SAR) has been proven an effective sensor in a wide variety of applications. Many of these uses require transmission and/or processing of the image data in a lossless manner. With the current state of SAR technology, the amount of data contained in a single image may be massive, whether the application requires the entire complex image or magnitude data only. In either case, some type of compression may be required to losslessly transmit this data in a given bandwidth or store it in a reasonable volume. This paper provides the results of applying several lossless compression schemes to SAR imagery.

  18. Synthetic aperture radar processing with tiered subapertures

    SciTech Connect

    Doerry, A.W.

    1994-06-01

    Synthetic Aperture Radar (SAR) is used to form images that are maps of radar reflectivity of some scene of interest, from range soundings taken over some spatial aperture. Additionally, the range soundings are typically synthesized from a sampled frequency aperture. Efficient processing of the collected data necessitates using efficient digital signal processing techniques such as vector multiplies and fast implementations of the Discrete Fourier Transform. Inherent in image formation algorithms that use these is a trade-off between the size of the scene that can be acceptably imaged, and the resolution with which the image can be made. These limits arise from migration errors and spatially variant phase errors, and different algorithms mitigate these to varying degrees. Two fairly successful algorithms for airborne SARs are Polar Format processing, and Overlapped Subaperture (OSA) processing. This report introduces and summarizes the analysis of generalized Tiered Subaperture (TSA) techniques that are a superset of both Polar Format processing and OSA processing. It is shown how tiers of subapertures in both azimuth and range can effectively mitigate both migration errors and spatially variant phase errors to allow virtually arbitrary scene sizes, even in a dynamic motion environment.

  19. Multi-mission, autonomous, synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Walls, Thomas J.; Wilson, Michael L.; Madsen, David; Jensen, Mark; Sullivan, Stephanie; Addario, Michael; Hally, Iain

    2014-05-01

    Unmanned aerial systems (UASs) have become a critical asset in current battlespaces and continue to play an increasing role for intelligence, surveillance and reconnaissance (ISR) missions. With the development of medium-to-low altitude, rapidly deployable aircraft platforms, the ISR community has seen an increasing push to develop ISR sensors and systems with real-time mission support capabilities. This paper describes recent flight demonstrations and test results of the RASAR (Real-time, Autonomous, Synthetic Aperture Radar) sensor system. RASAR is a modular, multi-band (L and X) synthetic aperture radar (SAR) imaging sensor designed for self-contained, autonomous, real-time operation with mission flexibility to support a wide range of ISR needs within the size, weight and power constraints of Group III UASs. The sensor command and control and real-time image formation processing are designed to allow integration of RASAR into a larger, multi-intelligence system of systems. The multi-intelligence architecture and a demonstration of real-time autonomous cross-cueing of a separate optical sensor will be presented.

  20. Motion Measurement for Synthetic Aperture Radar.

    SciTech Connect

    Doerry, Armin W.

    2015-01-01

    Synthetic Aperture Radar (SAR) measures radar soundings from a set of locations typically along the flight path of a radar platform vehicle. Optimal focusing requires precise knowledge of the sounding source locations in 3 - D space with respect to the target scene. Even data driven focusing techniques (i.e. autofocus) requires some degree of initial fidelity in the measurements of the motion of the radar. These requirements may be quite stringent especially for fine resolution, long ranges, and low velocities. The principal instrument for measuring motion is typically an Inertial Measurement Unit (IMU), but these instruments have inherent limi ted precision and accuracy. The question is %22How good does an IMU need to be for a SAR across its performance space?%22 This report analytically relates IMU specifications to parametric requirements for SAR. - 4 - Acknowledgements Th e preparation of this report is the result of a n unfunded research and development activity . Although this report is an independent effort, it draws heavily from limited - release documentation generated under a CRADA with General Atomics - Aeronautical System, Inc. (GA - ASI), and under the Joint DoD/DOE Munitions Program Memorandum of Understanding. Sandia National Laboratories is a multi - program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of En ergy's National Nuclear Security Administration under contract DE - AC04 - 94AL85000.

  1. Triangulation using synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Wu, Sherman S. C.; Howington-Kraus, Annie E.

    1991-01-01

    For the extraction of topographic information about Venus from stereoradar images obtained from the Magellan Mission, a Synthetic Aperture Radar (SAR) compilation system was developed on analytical stereoplotters. The system software was extensively tested by using stereoradar images from various spacecraft and airborne radar systems, including Seasat, SIR-B, ERIM XCL, and STAR-1. Stereomodeling from radar images was proven feasible, and development is on a correct approach. During testing, the software was enhanced and modified to obtain more flexibility and better precision. Triangulation software for establishing control points by using SAR images was also developed through a joint effort with the Defense Mapping Agency. The SAR triangulation system comprises four main programs, TRIDATA, MODDATA, TRISAR, and SHEAR. The first two programs are used to sort and update the data; the third program, the main one, performs iterative statistical adjustment; and the fourth program analyzes the results. Also, input are flight data and data from the Global Positioning System and Inertial System (navigation information). The SAR triangulation system was tested with six strips of STAR-1 radar images on a VAX-750 computer. Each strip contains images of 10 minutes flight time (equivalent to a ground distance of 73.5 km); the images cover a ground width of 22.5 km. All images were collected from the same side. With an input of 44 primary control points, 441 ground control points were produced. The adjustment process converged after eight iterations. With a 6-m/pixel resolution of the radar images, the triangulation adjustment has an average standard elevation error of 81 m. Development of Magellan radargrammetry will be continued to convert both SAR compilation and triangulation systems into digital form.

  2. Weighting in digital synthetic aperture radar processing

    NASA Technical Reports Server (NTRS)

    Dicenzo, A.

    1979-01-01

    Weighting is employed in synthetic aperture radar (SAR) processing to reduce the sidelobe response at the expense of peak center response height and mainlobe resolution. The weighting effectiveness in digital processing depends not only on the choice of weighting function, but on the fineness of sampling and quantization, on the time bandwidth product, on the quadratic phase error, and on the azimuth antenna pattern. The results of simulations conducted to uncover the effect of these parameters on azimuth weighting effectiveness are presented. In particular, it is shown that multilook capabilities of future SAR systems may obviate the need for consideration of the antenna pattern, and that azimuth time-bandwidth products of over 200 are probably required before the digital results begin to approach the ideal results.

  3. Orbit determination using synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Taber, W. L.; Synnott, S. P.; Riedel, J. E.

    1986-01-01

    The use of synthetic aperture radar (SAR) images to estimate orbital parameters is studied. The SAR image formation process which requires the ability to repeatedly transmit identical signals and accurately sense the return echoes from a region of terrain is described. The orbit determination capabilities of the SAR system's observables are investigated. Five SAR observations were collected from a simulated shuttle orbit, which was circular with a latitude of 220 km and along-track velocity of 7.7 km/sec, to obtain along-track and line-of-sight direction position measurements; the simulation reveals that only three SAR observations were required to determine the position of the spacecraft to within 100 m. A prototype SAR orbit determination system was developed. The system consists of a VAX 11/780 time-shared computer, a frame buffer, topographic maps, and software for line-pixel location of an object within a SAR image and for orbit determination. The prototype is applied to the processing of a single short arc of Shuttle Imaging-Radar-B (SIR-B) data. It is observed that the SAR data is useful as orbit determination or tracking data; however, the low SNRs in the SIR-B data made feature identification difficult.

  4. Multistatic synthetic aperture radar image formation.

    PubMed

    Krishnan, V; Swoboda, J; Yarman, C E; Yazici, B

    2010-05-01

    In this paper, we consider a multistatic synthetic aperture radar (SAR) imaging scenario where a swarm of airborne antennas, some of which are transmitting, receiving or both, are traversing arbitrary flight trajectories and transmitting arbitrary waveforms without any form of multiplexing. The received signal at each receiving antenna may be interfered by the scattered signal due to multiple transmitters and additive thermal noise at the receiver. In this scenario, standard bistatic SAR image reconstruction algorithms result in artifacts in reconstructed images due to these interferences. In this paper, we use microlocal analysis in a statistical setting to develop a filtered-backprojection (FBP) type analytic image formation method that suppresses artifacts due to interference while preserving the location and orientation of edges of the scene in the reconstructed image. Our FBP-type algorithm exploits the second-order statistics of the target and noise to suppress the artifacts due to interference in a mean-square sense. We present numerical simulations to demonstrate the performance of our multistatic SAR image formation algorithm with the FBP-type bistatic SAR image reconstruction algorithm. While we mainly focus on radar applications, our image formation method is also applicable to other problems arising in fields such as acoustic, geophysical and medical imaging. PMID:20051343

  5. Georeferencing on Synthetic Aperture Radar Imagery

    NASA Astrophysics Data System (ADS)

    Esmaeilzade, M.; Amini, J.; Zakeri, S.

    2015-12-01

    Due to the SAR1 geometry imaging, SAR images include geometric distortions that would be erroneous image information and the images should be geometrically calibrated. As the radar systems are side looking, geometric distortion such as shadow, foreshortening and layover are occurred. To compensate these geometric distortions, information about sensor position, imaging geometry and target altitude from ellipsoid should be available. In this paper, a method for geometric calibration of SAR images is proposed. The method uses Range-Doppler equations. In this method, for the image georeferencing, the DEM2 of SRTM with 30m pixel size is used and also exact ephemeris data of the sensor is required. In the algorithm proposed in this paper, first digital elevation model transmit to range and azimuth direction. By applying this process, errors caused by topography such as foreshortening and layover are removed in the transferred DEM. Then, the position of the corners on original image is found base on the transferred DEM. Next, original image registered to transfer DEM by 8 parameters projective transformation. The output is the georeferenced image that its geometric distortions are removed. The advantage of the method described in this article is that it does not require any control point as well as the need to attitude and rotational parameters of the sensor. Since the ground range resolution of used images are about 30m, the geocoded images using the method described in this paper have an accuracy about 20m (subpixel) in planimetry and about 30m in altimetry. 1 Synthetic Aperture Radar 2 Digital Elevation Model

  6. Real-time beamforming synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Rincon, Rafael; Hildebrand, Peter; Hilliard, Lawrence; Bradley, Damon; Krnan, Luko; Sheikh, Salman; Lucey, Jared

    2006-09-01

    This paper discusses the concept and design of a real-time Digital Beamforming Synthetic Aperture Radar (DBSAR) for airborne applications which can achieve fine spatial resolutions and wide swaths. The development of the DBSAR enhances important scientific measurements in Earth science, and serves as a prove-of-concept for planetary exploration missions. A unique aspect of DBSAR is that it achieves fine resolutions over large swaths by synthesizing multiple cross-track beams simultaneously using digital beamforming techniques. Each beam is processed using SAR algorithms to obtain the fine ground resolution without compromising fine range and azimuth resolutions. The processor uses an FPGA-based architecture to implement digital in-phase and quadrature (I/Q) demodulation, beamforming, and range and azimuth compression. The DBSAR concept will be implemented using the airborne L-Band Imaging Scatterometer (LIS) on board the NASA P3 aircraft. The system will achieve ground resolutions of less than 30 m and swaths of 10 km from an altitude of 8 km.

  7. A Seasat-A Synthetic Aperture Imaging Radar System

    NASA Technical Reports Server (NTRS)

    Jordan, R. L.; Rodgers, D. H.

    1976-01-01

    The Seasat-A Synthetic Aperture Imaging Radar System is the first radar system of its kind designed for the study of ocean wave patterns from orbit. The basic requirement of this system is to generate continuous radar imagery with a 100-km swath with 25 m resolution from an orbital altitude of 800 km. These requirements impose unique system design problems and their solutions will be stated. The end to end data system will be described including interactions of the spacecraft, antenna, sensor, telemetry link, and data processor. The synthetic aperture radar system generates a large quantity of data (110 megabits per second) requiring the use of a dedicated data link. The data link selected for use with the synthetic aperture radar is an analog link with stable local oscillator encoding. The problems associated in telemetering the radar information with sufficient fidelity to synthesize an image on the ground will be described as well as the selected solutions to the problems.

  8. Hughes integrated synthetic aperture radar: High performance at low cost

    SciTech Connect

    Bayma, R.W.

    1996-11-01

    This paper describes the background and development of the low cost high-performance Hughes Integrated Synthetic Aperture Radar (HISAR{trademark}) which has a full range of capabilities for real-time reconnaissance, surveillance and earth resource mapping. HISAR uses advanced Synthetic Aperture Radar (SAR) technology to make operationally effective images of near photo quality, day or night and in all weather conditions. This is achieved at low cost by maximizing the use of commercially available radar and signal-processing equipment in the fabrication. Furthermore, HISAR is designed to fit into an executive-class aircraft making it available for a wide range of users. 4 refs., 8 figs.

  9. Digital Beamforming Synthetic Aperture Radar (DBSAR) Polarimetric Upgrade

    NASA Technical Reports Server (NTRS)

    Rincon, Rafael F.; Perrine, Martin; McLinden, Matthew; Valett, Susan

    2011-01-01

    The Digital Beamforming Synthetic Aperture Radar (DBSAR) is a state-of-the-art radar system developed at NASA/Goddard Space Flight Center for the development and implementation of digital beamforming radar techniques. DBSAR was recently upgraded to polarimetric operation in order to enhance its capability as a science instrument. Two polarimetric approaches were carried out which will be demonstrated in upcoming flight campaigns.

  10. Interference Mitigation Effects on Synthetic Aperture Radar Coherent Data Products

    SciTech Connect

    Musgrove, Cameron

    2015-07-01

    For synthetic aperture radars radio frequency interference from sources external to the radar system and techniques to mitigate the interference can degrade the quality of the image products. Usually the radar system designer will try to balance the amount of mitigation for an acceptable amount of interference to optimize the image quality. This dissertation examines the effect of interference mitigation upon coherent data products of fine resolution, high frequency synthetic aperture radars using stretch processing. Novel interference mitigation techniques are introduced that operate on single or multiple apertures of data that increase average coherence compared to existing techniques. New metrics are applied to evaluate multiple mitigation techniques for image quality and average coherence. The underlying mechanism for interference mitigation techniques that affect coherence is revealed.

  11. A SEASAT-A synthetic aperture imaging radar system

    NASA Technical Reports Server (NTRS)

    Jordan, R. L.; Rodgers, D. H.

    1975-01-01

    The SEASAT, a synthetic aperture imaging radar system is the first radar system of its kind designed for the study of ocean wave patterns from orbit. The basic requirement of this system is to generate continuous radar imagery with a 100 km swath with 25m resolution from an orbital altitude of 800 km. These requirements impose unique system design problems. The end to end data system described including interactions of the spacecraft, antenna, sensor, telemetry link, and data processor. The synthetic aperture radar system generates a large quantity of data requiring the use of an analog link with stable local oscillator encoding. The problems associated in telemetering the radar information with sufficient fidelity to synthesize an image on the ground is described as well as the selected solutions to the problems.

  12. Speckle reduction in synthetic-aperture-radar imagery

    NASA Astrophysics Data System (ADS)

    Harvey, E. R.; April, G. V.

    1990-07-01

    Speckle appearing in synthetic-aperture-radar images degrades the information contained in these images. Speckle noise can be suppressed by adapted local processing techniques, permitting the definition of statistical parameters inside a small window centered on each pixel of the image. Two processing algorithms are examined; the first one uses the intensity as a variable, and the second one works on a homomorphic transformation of the image intensity. A statistical model for speckle noise that takes into account correlation in multilook imagery has been used to develop these processing algorithms. Several experimental results of processed Seasat-A synthetic-aperture-radar images are discussed.

  13. Synthetic aperture radar system design for random field classification

    NASA Technical Reports Server (NTRS)

    Harger, R. O.

    1973-01-01

    An optimum design study is carried out for synthetic aperture radar systems intended for classifying randomly reflecting areas (such as agricultural fields) characterized by a reflectivity density spectral density. The problem solution is obtained, neglecting interfield interference and assuming areas of known configuration and location, as well as a certain Gaussian signal field property. The optimum processor is nonlinear, but includes conventional matched filter processing. A set of summary design curves is plotted, and is applied to the design of a satellite synthetic aperture radar system.

  14. The US open skies synthetic aperture radar (SAROS)

    SciTech Connect

    Fortner, K.R.; Hezeltine, P.L.

    1996-11-01

    This paper discusses the Synthetic Aperture Radar for Open Skies (SAROS), an airborne side-looking synthetic aperture radar (SAR) system installed on the U.S. OC-135B Open Skies Observation Aircraft. The paper discusses in detail how the SAROS is designed to meet the performance requirements and limits of the Treaty on Open Skies. The SAROS is based on the U.S. AN/APD-12 analog radar system which has been modified to digitally record radar, motion, and annotation data on magnetic tape and has been designated as the AN/APD-14. The theoretical performance of the AN/APD-12 SAR exceeds the three meter range and azimuth resolution allowed by the Treaty. The SAROS design will limit the performance of the SAR to no better than three meter`s through reduction in transmitted frequency bandwidth, reduction in azimuth bandwidth, and decimation of azimuth sampling prior to recording of the phase history data. 5 figs.

  15. Space shuttle synthetic aperture radar. [using real time

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Results of a feasibility study to investigate a digital signal processor for real-time operation with a synthetic aperture radar system aboard the space shuttle are presented. Pertinent digital processing theory, a description of the proposed system, and size, weight, power, scheduling, and development estimates are included.

  16. The Newest Oldest Data From Seasat's Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Logan, Tom; Holt, Ben; Drew, Lisa

    2014-03-01

    A new suite of digital synthetic aperture radar (SAR) imagery, featuring historic views of Earth's oceans, sea ice, volcanoes, forests, glaciers, and more, was made available in its entirety for the first time by the Alaska Satellite Facility (ASF) in midsummer 2013.

  17. Synthetic Aperture Radar Image Formation in Reconfigurable Logic

    SciTech Connect

    DUDLEY,PETER A.

    2001-06-01

    This paper studies the implementation of polar format, synthetic aperture radar image formation in modern Field Programmable Gate Arrays (FPGA's). The polar format algorithm is described in rough terms and each of the processing steps is mapped to FPGA logic. This FPGA logic is analyzed with respect to throughput and circuit size for compatibility with airborne image formation.

  18. Antenna dimensions of synthetic aperture radar systems on satellites

    NASA Technical Reports Server (NTRS)

    Richter, K. R.

    1973-01-01

    Design of a synthetic aperture radar (SAR) for a satellite must take into account the limitation in weight and dimensions of the antenna. The lower limits of the antenna area are derived from the conditions of unambiguity of the SAR system. This result is applied to estimate the antenna requirements for SARs on satellites in circular orbits of various altitudes around Earth and Venus.

  19. Synthetic aperture radar processing with polar formatted subapertures

    SciTech Connect

    Doerry, A.W.

    1994-10-01

    Synthetic Aperture Radar (SAR) uses the motion of a small real antenna to synthesize a larger aperture, and thereby achieve very fine azimuth resolution. Efficient SAR image formation requires modelling the radar echo and compensating (focusing) the delay and phase for various positions in the target scene. Polar-Format processing is one successful algorithm developed to process large scenes at fine resolutions, but is still limited, especially at resolutions near a wavelength. This paper shows how using tiers of subapertures can overcome the limitations of Polar-Format processing and increase the focused scene size substantially while using only efficient vector multiplies and Fast Fourier Transforms.

  20. Potentials for change detection using Seasat synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Bryan, M. L.

    1981-01-01

    Synthetic aperture radars (SAR) image from a non-nadir position. Thus the orientation of the target and sensor to one another is of paramount importance. This has posed problems for data interpretation and with the potentials of radar data for change detection studies. It is possible to use Seasat radar data for change detection even though the look directions are fixed for each location. Especially in areas with repeated coverage on descending or ascending orbits or where the terrain is flat and the targets nonoriented, coverage may be sufficient to provide data for change detection. Examples of Los Angeles and the Everglades of Florida help develop and support the argument.

  1. A digital calibration method for synthetic aperture radar systems

    NASA Technical Reports Server (NTRS)

    Larson, Richard W.; Jackson, P. L.; Kasischke, Eric S.

    1988-01-01

    A basic method to calibrate imagery from synthetic aperture radar (SAR) systems is presented. SAR images are calibrated by monitoring all the terms of the radar equation. This procedure includes the use of both external (calibrated reference reflectors) and internal (system-generated calibration signals) sources to monitor the total SAR system transfer function. To illustrate the implementation of the procedure, two calibrated SAR images (X-band, 3.2-cm wavelength) are presented, along with the radar cross-section measurements of specific scenes within each image. The sources of error within the SAR image calibration procedure are identified.

  2. A system model and inversion for synthetic aperture radar imaging.

    PubMed

    Soumekh, M

    1992-01-01

    A system model and its corresponding inversion for synthetic aperture radar (SAR) imaging are presented. The system model incorporates the spherical nature of a radar's radiation pattern at far field. The inverse method based on this model performs a spatial Fourier transform (Doppler processing) on the recorded signals with respect to the available coordinates of a translational radar (SAR) or target (inverse SAR). It is shown that the transformed data provide samples of the spatial Fourier transform of the target's reflectivity function. The inverse method can be modified to incorporate deviations of the radar's motion from its prescribed straight line path. The effects of finite aperture on resolution, reconstruction, and sampling constraints for the imaging problem are discussed. PMID:18296140

  3. Analysis of synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Blanchard, B. J. (Principal Investigator)

    1976-01-01

    The author has identified the following significant results. Average radar response for L-band like polarized system appeared to be related to the watershed runoff coefficients when the viewing angle was approximately 42 deg off nadir. Four requirements for radar systems used to verify applications of active microwave for water resources were identified: (1) first generation digital data will be required; (2) radar should be calibrated both internally and externally; (3) new systems should avoid radom use; and (4) images should be geometrically rectified prior to delivery to the user.

  4. Soil-penetrating synthetic aperture radar

    SciTech Connect

    Boverie, B.; Brock, B.C.; Doerry, A.W.

    1994-12-01

    This report summarizes the results for the first year of a two year Laboratory Directed Research and Development (LDRD) effort. This effort included a system study, preliminary data acquisition, and preliminary algorithm development. The system study determined the optimum frequency and bandwidth, surveyed soil parameters and targets, and defined radar cross section in lossy media. The data acquisition imaged buried objects with a rail-SAR. Algorithm development included a radar echo model, three-dimensional processing, sidelobe optimization, phase history data interpolation, and clutter estimation/cancellation.

  5. New military uses for synthetic aperture radar (SAR)

    NASA Astrophysics Data System (ADS)

    Reamer, Richard E.; Stockton, Wayne; Stromfors, Richard D.

    1993-02-01

    Loral Defense Systems-Arizona, holder of the original patent for the invention of Synthetic Aperture Radar (SAR), developed SAR to meet the military's need for an all-weather, day/night sensor that could produce high quality reconnaissance imagery in adverse weather and restricted visibility conditions. These features, and the ability to image large areas with fine resolution in a relatively short period of time make this sensor useful for many military applications. To date, however, SARs for military use have been hampered by the fact that they've been large, complex, and expensive. Additionally, they have been mounted on special purpose, single mission aircraft which are costly to operate. That situation has changed. A small, modular SAR, called Miniature Synthetic Aperture Radar (MSAR) developed by Loral can be mounted with relative ease on Unmanned Aerial Vehicles (UAV) or on multi-mission aircraft such as the F-16, F/A-18, or on the F-14.

  6. Synthetic aperture radar and digital processing: An introduction

    NASA Technical Reports Server (NTRS)

    Dicenzo, A.

    1981-01-01

    A tutorial on synthetic aperture radar (SAR) is presented with emphasis on digital data collection and processing. Background information on waveform frequency and phase notation, mixing, Q conversion, sampling and cross correlation operations is included for clarity. The fate of a SAR signal from transmission to processed image is traced in detail, using the model of a single bright point target against a dark background. Some of the principal problems connected with SAR processing are also discussed.

  7. Studies of multi-baseline spaceborne interferometric synthetic aperture radars

    NASA Technical Reports Server (NTRS)

    Li, F.; Goldstein, R.

    1987-01-01

    A set of Seasat SAR data that were obtained in nearly repeat ground track orbits is utilized to simulate the performance of spaceborne interferometric synthetic aperture radar (ISAR) systems. A qualitative assessment of the topography measurement capability is presented. A phase measurement error model is described and compared with the data obtained at various baseline separations and signal-to-noise ratios. Finally, the implications of these results on the future spaceborne ISAR design are discussed.

  8. Synthetic aperture radar/LANDSAT MSS image registration

    NASA Technical Reports Server (NTRS)

    Maurer, H. E. (Editor); Oberholtzer, J. D. (Editor); Anuta, P. E. (Editor)

    1979-01-01

    Algorithms and procedures necessary to merge aircraft synthetic aperture radar (SAR) and LANDSAT multispectral scanner (MSS) imagery were determined. The design of a SAR/LANDSAT data merging system was developed. Aircraft SAR images were registered to the corresponding LANDSAT MSS scenes and were the subject of experimental investigations. Results indicate that the registration of SAR imagery with LANDSAT MSS imagery is feasible from a technical viewpoint, and useful from an information-content viewpoint.

  9. Two-dimensional phase correction of synthetic aperture radar imagery

    SciTech Connect

    Ghiglia, D.C.; Mastin, G.A.

    1989-01-01

    A two-dimensional synthetic aperture radar (SAR) phase correction algorithm is described as a natural extension of a one-dimensional technique developed previously. It embodies many similarities to phase gradient speckle imaging and incorporates improvements in phase estimation. Diffraction limited performance has been obtained on actual SAR imagery regardless of scene content or phase error structure. The algorithm is computationally efficient, robust, and easily implemented on a general purpose computer or special purpose hardware. 13 refs., 1 fig.

  10. A data compression technique for synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Frost, V. S.; Minden, G. J.

    1986-01-01

    A data compression technique is developed for synthetic aperture radar (SAR) imagery. The technique is based on an SAR image model and is designed to preserve the local statistics in the image by an adaptive variable rate modification of block truncation coding (BTC). A data rate of approximately 1.6 bit/pixel is achieved with the technique while maintaining the image quality and cultural (pointlike) targets. The algorithm requires no large data storage and is computationally simple.

  11. Spaceborne synthetic aperture radar pilot study

    NASA Technical Reports Server (NTRS)

    1974-01-01

    A pilot study of a spaceborne sidelooking radar is summarized. The results of the system trade studies are given along with the electrical parameters for the proposed subsystems. The mechanical aspects, packaging, thermal control and dynamics of the proposed design are presented. Details of the data processor are given. A system is described that allows the data from a pass over the U. S. to be in hard copy form within two hours. Also included are the proposed schedule, work breakdown structure, and cost estimate.

  12. Ionospheric effects on synthetic aperture radar at VHF

    SciTech Connect

    Fitzgerald, T.J.

    1997-02-01

    Synthetic aperture radars (SAR) operated from airplanes have been used at VHF because of their enhanced foliage and ground penetration compared to radars operated at UHF. A satellite-borne VHF SAR would have considerable utility but in order to operate with high resolution it would have to use both a large relative bandwidth and a large aperture. The presence of the ionosphere in the propagation path of the radar will cause a deterioration of the imaging because of dispersion over the bandwidth and group path changes in the imaged area over the collection aperture. In this paper we present calculations of the effects of a deterministic ionosphere on SAR imaging for a radar operated with a 100 MHz bandwidth centered at 250 MHz and over an angular aperture of 23{degrees}. The ionosphere induces a point spread function with an approximate half-width of 150 m in the slant-range direction and of 25 m in the cross-range direction compared to the nominal resolution of 1.5 m in both directions.

  13. Optimum frequency for subsurface-imaging synthetic-aperture radar

    SciTech Connect

    Brock, B.C.; Patitz, W.E.

    1993-05-01

    A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, most conventional synthetic-aperture radars operate at higher microwave frequencies which do not significantly penetrate below the soil surface. This study attempts to provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. Since the radar return from a buried object must compete with the return from surface clutter, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell`s equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Initial results indicate that the HF spectrum (3--30 MHz), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper vhf through uhf spectrum ({approximately}100 MHz--1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.

  14. Optimum frequency for subsurface-imaging synthetic-aperture radar

    SciTech Connect

    Brock, B.C.; Patitz, W.E.

    1993-05-01

    A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, most conventional synthetic-aperture radars operate at higher microwave frequencies which do not significantly penetrate below the soil surface. This study attempts to provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. Since the radar return from a buried object must compete with the return from surface clutter, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell's equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Initial results indicate that the HF spectrum (3--30 MHz), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper vhf through uhf spectrum ([approximately]100 MHz--1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.

  15. Speckle reduction in synthetic-aperture-radar imagery.

    PubMed

    Harvey, E R; April, G V

    1990-07-01

    Speckle appearing in synthetic-aperture-radar images degrades the information contained in these images. Speckle noise can be suppressed by adapted local processing techniques, permitting the definition of statistical parameters inside a small window centered on each pixel of the image. Two processing algorithms are examined; the first one uses the intensity as a variable, and the second one works on a homomorphic transformation of the image intensity. A statistical model for speckle noise that takes into account correlation in multilook imagery has been used to develop these processing algorithms. Several experimental results of processed Seasat-A syntheticaperture-radar images are discussed. PMID:19768064

  16. Proceedings of the Third Airborne Synthetic Aperture Radar (AIRSAR) Workshop

    NASA Technical Reports Server (NTRS)

    Vanzyl, Jakob J. (Editor)

    1991-01-01

    The Third Airborne Synthetic Aperture Radar (AIRSAR) Workshop was held on 23-24 May 1991 at JPL. Thirty oral presentations were made and 18 poster papers displayed during the workshop. Papers from these 25 presentations are presented which include analyses of AIRSAR operations and studies in SAR remote sensing, ecology, hydrology, soil science, geology, oceanography, volcanology, and SAR mapping and data handling. Results from these studies indicate the direction and emphasis of future orbital radar-sensor missions that will be launched during the 1990's.

  17. Probing the Martian Subsurface with Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Campbell, B. A.; Maxwell, T. A.; Freeman, A.

    2005-01-01

    Many regions of the martian surface are covered by fine-grained materials emplaced by volcanic, fluvial, or aeolian processes. These mantling deposits likely hide ancient channel systems (particularly at smaller scale lengths) and volcanic, impact, glacial, or shoreline features. Synthetic aperture radar (SAR) offers the capability to probe meters below the surface, with imaging resolution in the 10 s of m range, to reveal the buried terrain and enhance our understanding of Mars geologic and climate history. This presentation focuses on the practical applications of a Mars orbital SAR, methods for polarimetric and interferometric radar studies, and examples of such techniques for Mars-analog sites on the Moon and Earth.

  18. Synthetic aperture radar range - Azimuth ambiguity design and constraints

    NASA Technical Reports Server (NTRS)

    Mehlis, J. G.

    1980-01-01

    Problems concerning the design of a system for mapping a planetary surface with a synthetic aperture radar (SAR) are considered. Given an ambiguity level, resolution, and swath width, the problems are related to the determination of optimum antenna apertures and the most suitable pulse repetition frequency (PRF). From the set of normalized azimuth ambiguity ratio curves, the designer can arrive at the azimuth antenna length, and from the sets of normalized range ambiguity ratio curves, he can arrive at the range aperture length or pulse repetition frequency. A procedure based on this design method is shown in an example. The normalized curves provide results for a SAR using a uniformly or cosine weighted rectangular antenna aperture.

  19. Interferometric synthetic aperture radar imagery of the Gulf Stream

    NASA Technical Reports Server (NTRS)

    Ainsworth, T. L.; Cannella, M. E.; Jansen, R. W.; Chubb, S. R.; Carande, R. E.; Foley, E. W.; Goldstein, R. M.; Valenzuela, G. R.

    1993-01-01

    The advent of interferometric synthetic aperture radar (INSAR) imagery brought to the ocean remote sensing field techniques used in radio astronomy. Whilst details of the interferometry differ between the two fields, the basic idea is the same: Use the phase information arising from positional differences of the radar receivers and/or transmitters to probe remote structures. The interferometric image is formed from two complex synthetic aperture radar (SAR) images. These two images are of the same area but separated in time. Typically the time between these images is very short -- approximately 50 msec for the L-band AIRSAR (Airborne SAR). During this short period the radar scatterers on the ocean surface do not have time to significantly decorrelate. Hence the two SAR images will have the same amplitude, since both obtain the radar backscatter from essentially the same object. Although the ocean surface structure does not significantly decorrelate in 50 msec, surface features do have time to move. It is precisely the translation of scattering features across the ocean surface which gives rise to phase differences between the two SAR images. This phase difference is directly proportional to the range velocity of surface scatterers. The constant of proportionality is dependent upon the interferometric mode of operation.

  20. Time-frequency analysis of synthetic aperture radar signals

    SciTech Connect

    Johnston, B.

    1996-08-01

    Synthetic aperture radar (SAR) has become an important tool for remote sensing of the environment. SAR is a set of digital signal processing algorithms that are used to focus the signal returned to the radar because radar systems in themselves cannot produce the high resolution images required in remote sensing applications. To reconstruct an image, several parameters must be estimated and the quality of output image depends on the degree of accuracy of these parameters. In this thesis, we derive the fundamental SAR algorithms and concentrate on the estimation of one of its critical parameters. We show that the common technique for estimating this particular parameter can sometimes lead to erroneous results and reduced quality images. We also employ time-frequency analysis techniques to examine variations in the radar signals caused by platform motion and show how these results can be used to improve output image quality.

  1. Stationary and moving target shadow characteristics in synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Raynal, Ann Marie; Bickel, Douglas L.; Doerry, Armin W.

    2014-05-01

    An occluded or dark region in synthetic aperture radar (SAR) imagery, known as a shadow, is created when incident radar energy is obstructed by a target with height from illuminating resolution cells immediately behind the target in the ground plane. Shadows depend on the physical dimensions and mobility of a target, platform and radar imaging parameters, and scene clutter. Target shadow dimensions and intensity can be important radar observables in SAR imagery for target detection, location, and tracking or even identification. Stationary target shadows can provide insight as to the physical dimensions of a target, while moving target shadows may show more accurately the location and motion of the target over time versus Doppler energy which may be shifted or smeared outside the scene. However, SAR shadows prove difficult to capture as a target or platform moves, since the quality of the no-return area may quickly be washed-out in a scene over many clutter resolution cells during an aperture. Prior work in the literature has been limited to describing partial shadow degradation effects from platform or target motion of vehicles such as static target shadow tip or interior degradation during an aperture, or shadow degradation due to target motion solely in cross-range. In this paper, we provide a more general formulation of SAR shadow dimensions and intensity for non-specific targets with an arbitrary motion.

  2. Smart antennas for space-borne synthetic aperture radars

    NASA Astrophysics Data System (ADS)

    Qin, F.; Gao, S.; Mao, C.; Wang, Z.; Patyuchenko, A.; Younis, M.; Krieger, G.

    2015-11-01

    This paper discusses smart antennas for space-borne synthetic aperture radar (SAR). First, some recent development in smart antennas for space-borne SAR is reviewed. Then, the paper presents a low-cost space-borne SAR system using digital beam forming on receive. The smart antenna system is also discussed, and some results are shown. The antenna system, consisting of a parabolic reflector and multi-feed array, is designed and optimized for dual-band dual-polarized digital beam-forming performance. The operating frequencies are at X and Ka bands with the center frequency of 9.6 and 35.75 GHz, respectively. The stacked dipoles and square patches with parasitic elements are employed as the feed elements at X and Ka bands. Dual-band antenna arrays are combined in the same aperture, which not only reduce the aperture of the feed array, but also coincide the center of dual-band feed arrays.

  3. Potentials for change detection using Seasat synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Bryan, M. L.; Clark, J.

    1984-01-01

    The use of synthetic aperture radar (SAR) images for detecting change on the earth's surface is highly dependent on target orientation, azimuth angle, and sensor depression angle. SAR data can be used for change detection when consistency is maintained in radar wavelength, polarization, azimuth directions, and off-nadir depression angle. The interaction of these parameters and the imaged surface for change detection are shown in examples drawn from (1) Los Angeles, CA, (2) southern Florida, (3) Imperial Valley, CA, (4) a desert region west of Tucson, AZ, and (5) western Kansas. SAR imagery is used to emphasize the geometric form, and roughness, of the earth's surface. As changes in the roughness of the surface occur over time, temporal SAR images will indicate those differences. Several guidelines for change detection studies using imaging radar are derived from the examples.

  4. Application of synthetic aperture radar remote sensing in Antarctica

    NASA Astrophysics Data System (ADS)

    Zhou, Chunxia; Deng, Fanghui; Wan, Lei; Wang, Zemin; E, Dongchen; Zhou, Yu

    2014-05-01

    Synthetic Aperture Radar (SAR) delivers high-resolution radar images day or night, and in all weather conditions. It also offers the capability for penetrating materials. These unique capabilities boost the application of SAR remote sensing techniques in Antarctica. Based on the key area of Chinese National Antarctic Research Expedition (CHINARE) - PANDA (Prydz Bay, Amery Ice Shelf and Dome A) section, this paper summarized the typical applications of SAR data, and discussed the crevasse detection with semi-variance analysis in the SAR images of the Grove Mountains area, DEM generation with InSAR pairs and ICESat GLAS data of the Grove Mountains area and nearby areas, and ice flow velocity derivation from D-InSAR and offset tracking of the Grove Mountains area and downstream areas in East Antarctica. The studies provide important information for Antarctic fieldwork and scientific researches. It is further confirmed that Synthetic Aperture Radar remote sensing has tremendous potential in the field of glacial geomorphology, topographic mapping and glacier dynamics, etc.

  5. Apodized RFI filtering of synthetic aperture radar images

    SciTech Connect

    Doerry, Armin Walter

    2014-02-01

    Fine resolution Synthetic Aperture Radar (SAR) systems necessarily require wide bandwidths that often overlap spectrum utilized by other wireless services. These other emitters pose a source of Radio Frequency Interference (RFI) to the SAR echo signals that degrades SAR image quality. Filtering, or excising, the offending spectral contaminants will mitigate the interference, but at a cost of often degrading the SAR image in other ways, notably by raising offensive sidelobe levels. This report proposes borrowing an idea from nonlinear sidelobe apodization techniques to suppress interference without the attendant increase in sidelobe levels. The simple post-processing technique is termed Apodized RFI Filtering (ARF).

  6. Synthetic aperture radar images with composite azimuth resolution

    DOEpatents

    Bielek, Timothy P; Bickel, Douglas L

    2015-03-31

    A synthetic aperture radar (SAR) image is produced by using all phase histories of a set of phase histories to produce a first pixel array having a first azimuth resolution, and using less than all phase histories of the set to produce a second pixel array having a second azimuth resolution that is coarser than the first azimuth resolution. The first and second pixel arrays are combined to produce a third pixel array defining a desired SAR image that shows distinct shadows of moving objects while preserving detail in stationary background clutter.

  7. Interpolated spatially variant apodization in synthetic aperture radar imagery.

    PubMed

    Yocky, D A; Jakowatz, C V; Eichel, P H

    2000-05-10

    The original formulation of spatially variant apodization for complex synthetic aperture radar imagery concentrated on integer-oversampled data. Noninteger-oversampled data presented previously [IEEE Trans. Aerosp. Electron. Syst. 31, 267 (1995)] suggested use of different weightings in the algorithm. An alternative noninteger-oversampled approach that employs the same apodization concept but uses local spatial interpolation is presented. With this approach the combined image formation, apodization, and detection of 1.3x-versus-2.0x oversampled data can be performed in half the time without loss of image quality. PMID:18345138

  8. Two target height effects on interferometric synthetic aperture radar coherence

    SciTech Connect

    YOCKY,DAVID A.; JAKOWATZ JR.,CHARLES V.

    2000-03-07

    Useful products generated from interferometric synthetic aperture radar (IFSAR) complex data include height measurement, coherent change detection, and classification. The IFSAR coherence is a spatial measure of complex correlation between two collects, a product of IFSAR signal processing. A tacit assumption in such IFSAR signal processing is that one height target exists in each range-Doppler cell. This paper presents simulations of IFSAR coherence if two targets with different heights exist in a given range-Doppler cell, a condition in IFSAR collections produced by layover. It also includes airborne IFSAR data confirming the simulation results. The paper concludes by exploring the implications of the results on IFSAR classification and height measurements.

  9. Determination of spacecraft attitude using synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Wu, C.; Curlander, J. C.; Di Cenzo, A.

    1980-01-01

    A method has been developed for precise sensor platform attitude determination which exploits the availability of synthetic aperture radar (SAR) sensors on future planned NASA earth orbiting spacecraft. Using the ephemeris along with data on planet shape and rotation, the relative motion between sensor and target area and therefore the Doppler frequency shift in the returned echo data is determined. Equations have been developed that relate the Doppler shift to the antenna attitude. The method is tested by comparing attitude predictions from SEASAT SAR digital echo data with available conventionally determined SEASAT attitude information.

  10. Digital technique for generating synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Van De Lindt, W. J.

    1977-01-01

    This paper describes a digital processing method applicable to a synthetic aperture radar, to be carried by the space shuttle or by satellites. The method uses an earth-fixed coordinate system in which corrective procedures are invoked to compensate for errors introduced by the satellite motion, earth curvature, and wavefront curvature. Among the compensations discussed are those of the coordinate system, skewness, roll, pitch, yaw, earth rotation, and others. The application of a Fast Fourier Transform in the numerical processing of the two-dimensional convolution is discussed in detail.

  11. Seasat synthetic aperture radar - Ocean wave detection capabilities

    NASA Technical Reports Server (NTRS)

    Gonzalez, F. I.; Beal, R. C.; Brown, W. E.; Deleonibus, P. S.; Sherman, J. W., III; Gower, J. F. R.; Lichy, D.; Ross, D. B.; Rufenach, C. L.; Shuchman, R. A.

    1979-01-01

    A preliminary assessment has been made of the capability of the Seasat synthetic aperture radar to detect ocean waves. Comparison with surface and aircraft measurements from five passes of the satellite over the Gulf of Alaska indicates agreement to within about 15 percent in wavelength and about 25 deg in wave direction. These results apply to waves 100 to 250 meters in length, propagating in a direction predominantly across the satellite track, in sea states with significant wave height in a range of 2 to 3.5 meters.

  12. SEASAT views oceans and sea ice with synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Fu, L. L.; Holt, B.

    1982-01-01

    Fifty-one SEASAT synthetic aperture radar (SAR) images of the oceans and sea ice are presented. Surface and internal waves, the Gulf Stream system and its rings and eddies, the eastern North Pacific, coastal phenomena, bathymetric features, atmospheric phenomena, and ship wakes are represented. Images of arctic pack and shore-fast ice are presented. The characteristics of the SEASAT SAR system and its image are described. Maps showing the area covered, and tables of key orbital information, and listing digitally processed images are provided.

  13. Efficient parallel implementation of polarimetric synthetic aperture radar data processing

    NASA Astrophysics Data System (ADS)

    Martinez, Sergio S.; Marpu, Prashanth R.; Plaza, Antonio J.

    2014-10-01

    This work investigates the parallel implementation of polarimetric synthetic aperture radar (POLSAR) data processing chain. Such processing can be computationally expensive when large data sets are processed. However, the processing steps can be largely implemented in a high performance computing (HPC) environ- ment. In this work, we studied different aspects of the computations involved in processing the POLSAR data and developed an efficient parallel scheme to achieve near-real time performance. The algorithm is implemented using message parsing interface (MPI) framework in this work, but it can be easily adapted for other parallel architectures such as general purpose graphics processing units (GPGPUs).

  14. Passive synthetic aperture radar imaging of ground moving targets

    NASA Astrophysics Data System (ADS)

    Wacks, Steven; Yazici, Birsen

    2012-05-01

    In this paper we present a method for imaging ground moving targets using passive synthetic aperture radar. A passive radar imaging system uses small, mobile receivers that do not radiate any energy. For these reasons, passive imaging systems result in signicant cost, manufacturing, and stealth advantages. The received signals are obtained by multiple airborne receivers collecting scattered waves due to illuminating sources of opportunity such as commercial television, radio, and cell phone towers. We describe a novel forward model and a corresponding ltered-backprojection type image reconstruction method combined with entropy optimization. Our method determines the location and velocity of multiple targets moving at dierent velocities. Furthermore, it can accommodate arbitrary imaging geometries. we present numerical simulations to verify the imaging method.

  15. Coherent optical processing of synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Cindrich, I.; Marks, J.; Klooster, A.

    1977-01-01

    Consideration is given to the data processing algorithm used in synthetic aperture radar (SAR) systems. Examples are presented of radar imagery obtained with the ERIM X-band SAR system and processed with a precision optical processor. An optical recording of the data is the input to the coherent optical processing channel. The encoding technique, spatial format, and quality of the stored data are discussed. Several optical processor configurations are outlined, noting particularly the tilted-plane system. A scanning photodetector serves to convert the optical processor output image data into an electronic signal stream. Solid-state two-dimensional photodetector arrays may provide this function at increased speeds and with greater accuracy.

  16. Precipitation mapping with an airborne synthetic aperture imaging radar

    NASA Technical Reports Server (NTRS)

    Atlas, D.; Elachi, C.; Brown, W. E., Jr.

    1977-01-01

    Use of an airborne synthetic-aperture radar (SAR) of 3.1-cm wavelength for the detection and mapping of precipitation echoes is described. Difficulties in mapping related to the incoherence of the echoes are discussed; methods of increasing resolution by Doppler filtering are suggested. Observations made with a vertical side-looking SAR system flying above a stratiform storm were found to resemble vertical cross sections obtained with conventional radar showing snow streamers, the bright band and rain. However, the actual section sampled by the SAR after filtering for zero Doppler is shown to depend upon both the relative motion of the particles and the relative winds below the aircraft. Knowledge of the relative winds, deduced from Doppler spectrum variations, and of the particle fall speeds permits the generation of horizontal and vertical cross sections displaced from the aircraft's position.

  17. Signal based motion compensation for synthetic aperture radar

    SciTech Connect

    John Kirk

    1999-06-07

    The purpose of the Signal Based Motion Compensation (SBMC) for Synthetic Aperture Radar (SAR) effort is to develop a method to measure and compensate for both down range and cross range motion of the radar in order to provide high quality focused SAR imagery in the absence of precision measurements of the platform motion. Currently SAR systems require very precise navigation sensors for motion compensation. These sensors are very expensive and are often supplied in pairs for reliability. In the case of GPS they can be jammed, further degrading performance. This makes for a potentially very expensive and possibly vulnerable SAR system. SBMC can eliminate or reduce the need for these expensive navigation sensors thus reducing the cost of budget minded SAR systems. The results on this program demonstrated the capability of the SBMC approach.

  18. Remote sensing with spaceborne synthetic aperture imaging radars: A review

    NASA Technical Reports Server (NTRS)

    Cimino, J. B.; Elachi, C.

    1983-01-01

    A review is given of remote sensing with Spaceborne Synthetic Aperture Radars (SAR's). In 1978, a spaceborne SA was flown on the SEASAT satellite. It acquired high resulution images over many regions in North America and the North Pacific. The acquired data clearly demonstrate the capability of spaceborne SARs to: image and track polar ice floes; image ocean surface patterns including swells, internal waves, current boundaries, weather boundaries and vessels; and image land features which are used to acquire information about the surface geology and land cover. In 1981, another SAR was flown on the second shuttle flight. This Shuttle Imaging Radar (SIR-A) acquired land and ocean images over many areas around the world. The emphasis of the SIR-A experiment was mainly toward geologic mapping. Some of the key results of the SIR-A experiment are given.

  19. Interference Mitigation Effects on Synthetic Aperture Radar Coherent Data Products

    SciTech Connect

    Musgrove, Cameron

    2014-05-01

    For synthetic aperture radar image products interference can degrade the quality of the images while techniques to mitigate the interference also reduce the image quality. Usually the radar system designer will try to balance the amount of mitigation for the amount of interference to optimize the image quality. This may work well for many situations, but coherent data products derived from the image products are more sensitive than the human eye to distortions caused by interference and mitigation of interference. This dissertation examines the e ect that interference and mitigation of interference has upon coherent data products. An improvement to the standard notch mitigation is introduced, called the equalization notch. Other methods are suggested to mitigation interference while improving the quality of coherent data products over existing methods.

  20. A comparison of spotlight synthetic aperture radar image formation techniques

    SciTech Connect

    Knittle, C.D.; Doren, N.E.; Jakowatz, C.V.

    1996-10-01

    Spotlight synthetic aperture radar images can be formed from the complex phase history data using two main techniques: (1) polar-to-cartesian interpolation followed by two-dimensional inverse Fourier transform (2DFFT), and (2) convolution backprojection (CBP). CBP has been widely used to reconstruct medical images in computer aided tomography, and only recently has been applied to form synthetic aperture radar imagery. It is alleged that CBP yields higher quality images because (1) all the Fourier data are used and (2) the polar formatted data is used directly to form a 2D Cartesian image and therefore 2D interpolation is not required. This report compares the quality of images formed by CBP and several modified versions of the 2DFFT method. We show from an image quality point of view that CBP is equivalent to first windowing the phase history data and then interpolating to an exscribed rectangle. From a mathematical perspective, we should expect this conclusion since the same Fourier data are used to form the SAR image. We next address the issue of parallel implementation of each algorithm. We dispute previous claims that CBP is more readily parallelizable than the 2DFFT method. Our conclusions are supported by comparing execution times between massively parallel implementations of both algorithms, showing that both experience similar decreases in computation time, but that CBP takes significantly longer to form an image.

  1. Data management approach to search and rescue synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Green, John E.; Rogers, George W.

    1997-06-01

    The NASA sponsored Search and Rescue Synthetic Aperture Radar (SAR) program seeks to use foliage penetrating synthetic aperture radar (SAR) to locate light plane crashes in remote areas. In addition to the hardware and pattern recognition issues, data management is recognized as a significant part of the overall problem. A single NASA/JPL AIRSAR polarimetric image in P, L, and C bands takes approximately 524 megabytes of storage. Algorithmic development efforts, as well as an eventual operational system, will likely require maintaining a large database of SAR imagery, as well as derived features and associated geographical information. The need for this much data is driven in large part by the complexity of the detection problem. A simple classification/detection algorithm does not currently seem feasible. Rather, a data driven approach that can incorporate local background characteristics as well as geographical information seems to be called for. This in turn makes data management a key issue. This paper presents a comprehensive data management framework suitable for the SAR problem, as well as other similar massive data set management problems.

  2. Compact, autonomous, multi-mission synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Walls, Thomas J.; Wilson, Michael L.; Madsen, David; Knight, Chad; Jensen, Mark D.; Partridge, Darin C.; Addario, Mike

    2013-05-01

    The utilization of unmanned aerial systems (UASs) for intelligence, surveillance and reconnaissance (ISR) applications continues to increase and unmanned systems have become a critical asset in current and future battlespaces. With the development of medium-to-low altitude, rapidly deployable aircraft platforms, the ISR community has seen an increasing push to develop ISR sensors and systems with real-time mission support capabilities. This paper describes the design and development of the RASAR (Real-time, Autonomous, Synthetic Aperture Radar) sensor system and presents demonstration flight test results. RASAR is a modular, multi-band (L and X) synthetic aperture radar (SAR) imaging sensor designed for self-contained, autonomous, real-time operation with mission flexibility to support a wide range of ISR needs within the size, weight and power constraints of Group III UASs. SAR waveforms are generated through direct digital synthesis enabling arbitrary waveform notching to enable operations in cluttered RF environments. RASAR is capable of simultaneous dual-channel receive to enable polarization based target discrimination. The sensor command and control and real-time image formation processing are designed to enable integration of RASAR into larger, multi-intelligence system of systems. The multi-intelligence architecture and a demonstration of real-time autonomous cross-cueing of a separate optical sensor will be presented.

  3. Synthetic aperture radar and interferometry development at Sandia National Laboratories

    SciTech Connect

    1993-04-01

    Environmental monitoring, earth-resource mapping, and military systems require broad-area imaging at high resolutions. Many times the imagery must be acquired in inclement weather or during night as well as day. Synthetic aperture radar (SAR) provides such a capability. SAR systems take advantage of the long-range propagation characteristics of radar signals and the complex information processing capability of modern digital electronics to provide high resolution imagery. SAR complements photographic and other optical imaging capabilities because of the minimum constrains on time-of-day and atmospheric conditions and because of the unique responses of terrain and cultural targets to radar frequencies. Interferometry is a method for generating a three-dimensional image of terrain. The height projection is obtained by acquiring two SAR images from two slightly differing locations. It is different from the common method of stereoscopic imaging for topography. The latter relies on differing geometric projections for triangulation to define the surface geometry whereas interferometry relies on differences in radar propagation times between the two SAR locations. This paper presents the capabilities of SAR, explains how SAR works, describes a few SAR applications, provides an overview of SAR development at Sandia, and briefly describes the motion compensation subsystem.

  4. Experiment in Onboard Synthetic Aperture Radar Data Processing

    NASA Technical Reports Server (NTRS)

    Holland, Matthew

    2011-01-01

    Single event upsets (SEUs) are a threat to any computing system running on hardware that has not been physically radiation hardened. In addition to mandating the use of performance-limited, hardened heritage equipment, prior techniques for dealing with the SEU problem often involved hardware-based error detection and correction (EDAC). With limited computing resources, software- based EDAC, or any more elaborate recovery methods, were often not feasible. Synthetic aperture radars (SARs), when operated in the space environment, are interesting due to their relevance to NASAs objectives, but problematic in the sense of producing prodigious amounts of raw data. Prior implementations of the SAR data processing algorithm have been too slow, too computationally intensive, and require too much application memory for onboard execution to be a realistic option when using the type of heritage processing technology described above. This standard C-language implementation of SAR data processing is distributed over many cores of a Tilera Multicore Processor, and employs novel Radiation Hardening by Software (RHBS) techniques designed to protect the component processes (one per core) and their shared application memory from the sort of SEUs expected in the space environment. The source code includes calls to Tilera APIs, and a specialized Tilera compiler is required to produce a Tilera executable. The compiled application reads input data describing the position and orientation of a radar platform, as well as its radar-burst data, over time and writes out processed data in a form that is useful for analysis of the radar observations.

  5. Addendum to proceedings of the 1978 Synthetic Aperture Radar Technology Conference

    NASA Technical Reports Server (NTRS)

    1978-01-01

    Various research projects on synthetic aperture radar are reported, including SAR calibration techniques. Slot arrays, sidelobe suppression, and wide swaths on satellite-borne radar were examined. The SAR applied to remote sensing was also considered.

  6. Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Radar Imagery

    SciTech Connect

    Eichel, Paul H.; Jakowatz, Jr., Charles V.; Yocky, David A.

    1999-06-29

    Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Original formulation of spatially variant anodization for complex synthetic aperture radar (SAR) imagery oversampled at twice the Nyquist rate (2.OX). Here we report a spatially interpolating, noninteger-oversampled SVA sidelobe. The pixel's apparent IPR location is assessed by comparing its value to the sum of its value plus weighted comparable for exact interpolation. However, exact interpolation implies an ideal sine interpolator3 and large components may not be necessary. Note that P is the summation of IPR diagonal values. The value of a sine IPR on the diagonals is a sine-squared; values much less than cardinal direction (m, n) values. This implies that cardinal direction interpolation requires higher precision than diagonal interpolation. Consequently, we employed a smaller set. The spatially interpolated SVA used an 8-point/4-point sine interpolator described above. Table 1 shows the Table 1 results show a two-times speed-up using the 1.3x oversampled and spatially interpolated SVA over the Figure 1d. Detected results of 1.3x oversampled sine interpolated spatially variant

  7. Synthetic aperture radar simulation for image sensitivity assessment

    NASA Astrophysics Data System (ADS)

    McCarty, Sean P.; Williams, Wayne D.; Keydel, Eric R.

    2006-05-01

    Synthetic aperture radar (SAR) is an all weather sensor that has provided breakthrough remote sensing capabilities for both civilian and military applications. SAR differs from other real-aperture sensors in that it achieves fine resolution using signal processing techniques that are based on certain assumptions about the relative dynamics between the sensor and the scene. When these assumptions are violated, the quality of the SAR imagery degrades, impacting its interpretability. This paper describes the development of a simulation testbed for evaluating the effects of SAR-specific error sources on image quality, including effects that originate with the sensor (e.g. system noise, uncompensated motion), as well as effects that originate in the scene (e.g. target motion, wind-blown trees). The simulation generates synthetic video phase history and can accommodate a variety of sensor collection trajectories, acquisition geometries, and image formation options. The simulation approach will be described, example outputs will be shown, and initial results relating simulation inputs to image quality measures will be presented.

  8. The rapid terrain visualization interferometric synthetic aperture radar sensor

    NASA Astrophysics Data System (ADS)

    Graham, Robert H.; Bickel, Douglas L.; Hensley, William H.

    2003-11-01

    The Rapid Terrain Visualization interferometric synthetic aperture radar was designed and built at Sandia National Laboratories as part of an Advanced Concept Technology Demonstration (ACTD) to "demonstrate the technologies and infrastructure to meet the Army requirement for rapid generation of digital topographic data to support emerging crisis or contingencies." This sensor is currently being operated by Sandia National Laboratories for the Joint Precision Strike Demonstration (JPSD) Project Office to provide highly accurate digital elevation models (DEMs) for military and civilian customers, both inside and outside of the United States. The sensor achieves better than DTED Level IV position accuracy in near real-time. The system is being flown on a deHavilland DHC-7 Army aircraft. This paper outlines some of the technologies used in the design of the system, discusses the performance, and will discuss operational issues. In addition, we will show results from recent flight tests, including high accuracy maps taken of the San Diego area.

  9. Moving receive beam method and apparatus for synthetic aperture radar

    DOEpatents

    Kare, Jordin T.

    2001-01-01

    A method and apparatus for improving the performance of Synthetic Aperture Radar (SAR) systems by reducing the effect of "edge losses" associated with nonuniform receiver antenna gain. By moving the receiver antenna pattern in synchrony with the apparent motion of the transmitted pulse along the ground, the maximum available receiver antenna gain can be used at all times. Also, the receiver antenna gain for range-ambiguous return signals may be reduced, in some cases, by a large factor. The beam motion can be implemented by real-time adjustment of phase shifters in an electronically-steered phased-array antenna or by electronic switching of feed horns in a reflector antenna system.

  10. Automatic aircraft landing using interferometric inverse synthetic aperture radar imaging.

    PubMed

    Soumekh, M

    1996-01-01

    This paper presents an interferometric processing of an aircraft's monostatic and bistatic inverse synthetic aperture radar (ISAR) signatures for automatic landing. The aircraft's squint angle in this ISAR imaging problem is near 90 degrees . We show that this extreme squint angle does not pose any problem for the ISAR Fourier-based (wavefront) reconstruction algorithm. In fact, the aircraft can be imaged accurately, and without any erroneous shifts in the cross-range domain, within the imposed theoretical resolution. Moreover, the algorithm is accurate enough such that one can utilize the phase of the ISAR monostatic and bistatic measurements for interferometric processing. The resultant interferometric ISAR image is used to detect undesirable rotations in the aircraft's orientation. PMID:18285222

  11. Perceptual compression of magnitude-detected synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    Gorman, John D.; Werness, Susan A.

    1994-01-01

    A perceptually-based approach for compressing synthetic aperture radar (SAR) imagery is presented. Key components of the approach are a multiresolution wavelet transform, a bit allocation mask based on an empirical human visual system (HVS) model, and hybrid scalar/vector quantization. Specifically, wavelet shrinkage techniques are used to segregate wavelet transform coefficients into three components: local means, edges, and texture. Each of these three components is then quantized separately according to a perceptually-based bit allocation scheme. Wavelet coefficients associated with local means and edges are quantized using high-rate scalar quantization while texture information is quantized using low-rate vector quantization. The impact of the perceptually-based multiresolution compression algorithm on visual image quality, impulse response, and texture properties is assessed for fine-resolution magnitude-detected SAR imagery; excellent image quality is found at bit rates at or above 1 bpp along with graceful performance degradation at rates below 1 bpp.

  12. SEASAT synthetic-aperture radar data user's manual

    NASA Technical Reports Server (NTRS)

    Pravdo, S. H.; Huneycutt, B.; Holt, B. M.; Held, D. N.

    1983-01-01

    The SEASAT Synthetic-Aperture Radar (SAR) system, the data processors, the extent of the image data set, and the means by which a user obtains this data are described and the data quality is evaluated. The user is alerted to some potential problems with the existing volume of SEASAT SAR image data, and allows him to modify his use of that data accordingly. Secondly, the manual focuses on the ultimate focuses on the ultimate capabilities of the raw data set and evaluates the potential of this data for processing into accurately located, amplitude-calibrated imagery of high resolution. This allows the user to decide whether his needs require special-purpose data processing of the SAR raw data.

  13. Topography estimation with interferometric synthetic aperture radar using fringe detection

    NASA Technical Reports Server (NTRS)

    Lin, Qian; Vesecky, John F.; Zebker, Howard A.

    1991-01-01

    Methods are presented for using Synthetic Aperture Radar (SAR) interferometry data to estimate surface topography. An expression is given to relate the elevation of a ground point to the phase difference of SAR images received from two spatially separated antennas. An iterative algorithm which solves for the position and elevation of each point in the image simultaneously is developed. One of the critical issues that determines the accuracy of the terrain mapping is the phase unwrapping. An approach to the problem by fringe line detection is proposed. The algorithms are tested with two Seasat SAR images of terrain near Yellowstone National Park. The resultant elevation map is compared with a USGS terrain elevation model. The error of the SAR elevation with respect to the digital terrain map is about 8.2 percent of the total terrain variation.

  14. Theory and design of interferometric synthetic aperture radars

    NASA Technical Reports Server (NTRS)

    Rodriguez, E.; Martin, J. M.

    1992-01-01

    A derivation of the signal statistics, an optimal estimator of the interferometric phase, and the expression necessary to calculate the height-error budget are presented. These expressions are used to derive methods of optimizing the parameters of the interferometric synthetic aperture radar system (InSAR), and are then employed in a specific design example for a system to perform high-resolution global topographic mapping with a one-year mission lifetime, subject to current technological constraints. A Monte Carlo simulation of this InSAR system is performed to evaluate its performance for realistic topography. The results indicate that this system has the potential to satisfy the stringent accuracy and resolution requirements for geophysical use of global topographic data.

  15. Performance limits for maritime Inverse Synthetic Aperture Radar (ISAR).

    SciTech Connect

    Doerry, Armin Walter

    2013-11-01

    The performance of an Inverse Synthetic Aperture Radar (ISAR) system depends on a variety of factors, many which are interdependent in some manner. In this report we specifically examine ISAR as applied to maritime targets (e.g. ships). 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 ISAR 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'.

  16. Adaptive resource allocation for synthetic aperture radars under resource constraints

    NASA Astrophysics Data System (ADS)

    Newstadt, Gregory E.; Zelnio, Edmund G.; Hero, Alfred O.

    2013-05-01

    In along-track synthetic aperture radar systems, measurements from multiple phase centers can be used to remove bright stationary clutter in order to detect and estimate moving targets in the scene. The effectiveness of this procedure can be improved by increasing the number of antennas in the system. However, due to computational and communication constraints, it may be prohibitive to use a large number of antennas. In this work, an efficient resource allocation policy is provided to exploit sparsity in the scene, namely that there are few targets relative to the size of the scene. It is shown that even with limited computational resources, one can have significant estimation and computational gains over non-adaptive strategies. Moreover, the performance of the adaptive strategy approaches that of an oracle policy as the number of the stages grows large.

  17. Seamless Synthetic Aperture Radar Archive for Interferometry Analysis

    NASA Astrophysics Data System (ADS)

    Baker, S.; Baru, C.; Bryson, G.; Buechler, B.; Crosby, C.; Fielding, E.; Meertens, C.; Nicoll, J.; Youn, C.

    2014-11-01

    The NASA Advancing Collaborative Connections for Earth System Science (ACCESS) seamless synthetic aperture radar (SAR) archive (SSARA) project is a collaboration between UNAVCO, the Alaska Satellite Facility (ASF), the Jet Propulsion Laboratory (JPL), and OpenTopography at the San Diego Supercomputer Center (SDSC) to design and implement a seamless distributed access system for SAR data and derived interferometric SAR (InSAR) data products. A unified application programming interface (API) has been created to search the SAR archives at ASF and UNAVCO, 30 and 90-m SRTM DEM data available through OpenTopography, and tropospheric data from the NASA OSCAR project at JPL. The federated query service provides users a single access point to search for SAR granules, InSAR pairs, and corresponding DEM and tropospheric data products from the four archives, as well as the ability to search and download pre-processed InSAR products from ASF and UNAVCO.

  18. Application of microprocessors to spacecraft synthetic aperture radar processing

    NASA Technical Reports Server (NTRS)

    Arens, W. E.

    1978-01-01

    A ground-based digital synthetic aperture radar (SAR) processor capable of correlating images from raw spacecraft data at real-time rates is currently under development. The processor design requirements are particularly formidable due to (1) range migration effects resulting from planetary curvature and rotation, (2) antenna beam pointing errors, and (3) variation of the Doppler reference function with changing orbital parameters. Based upon the current effort, this paper describes a candidate real-time on-board SAR processing implementation approach that might evolve for future spacecraft applications. Key features include the use of custom large scale integration (LSI) charge-coupled device (CCD) technology to accomplish the correlation functions and microprocessor technology to effect control.

  19. Semisupervised synthetic aperture radar image segmentation with multilayer superpixels

    NASA Astrophysics Data System (ADS)

    Wang, Can; Su, Weimin; Gu, Hong; Gong, Dachen

    2015-01-01

    Image segmentation plays a significant role in synthetic aperture radar (SAR) image processing. However, SAR image segmentation is challenging due to speckle. We propose a semisupervised bipartite graph method for segmentation of an SAR image. First, the multilayer over-segmentation of the SAR image, referred to as superpixels, is computed using existing segmentation algorithms. Second, an unbalanced bipartite graph is constructed in which the correlation between pixels is replaced by the texture similarity between superpixels, to reduce the dimension of the edge matrix. To also improve efficiency, we define a new method, called the combination of the Manhattan distance and symmetric Kullback-Leibler divergence, to measure texture similarity. Third, by the Moore-Penrose inverse matrix and semisupervised learning, we construct an across-affinity matrix. A quantitative evaluation using SAR images shows that the new algorithm produces significantly high-quality segmentations as compared with state-of-the-art segmentation algorithms.

  20. The Rapid Terrain Visualization interferometric synthetic aperture radar sensor.

    SciTech Connect

    Graham, Robert H.; Hensley, William Heydon, Jr.; Bickel, Douglas Lloyd

    2003-07-01

    The Rapid Terrain Visualization interferometric synthetic aperture radar was designed and built at Sandia National Laboratories as part of an Advanced Concept Technology Demonstration (ACTD) to 'demonstrate the technologies and infrastructure to meet the Army requirement for rapid generation of digital topographic data to support emerging crisis or contingencies.' This sensor is currently being operated by Sandia National Laboratories for the Joint Precision Strike Demonstration (JPSD) Project Office to provide highly accurate digital elevation models (DEMs) for military and civilian customers, both inside and outside of the United States. The sensor achieves better than DTED Level IV position accuracy in near real-time. The system is being flown on a deHavilland DHC-7 Army aircraft. This paper outlines some of the technologies used in the design of the system, discusses the performance, and will discuss operational issues. In addition, we will show results from recent flight tests, including high accuracy maps taken of the San Diego area.

  1. Gulf Stream surface convergence imaged by synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Marmorino, G. O.; Jansen, R. W.; Valenzuela, G. R.; Trump, C. L.; Lee, J. S.; Kaiser, J. A. C.

    1994-09-01

    On July 20, 1990, the north edge of the Gulf Stream (36.7°N, 72.0°W) was sampled by the R/V Cape Henlopen and simultaneously imaged by the Jet Propulsion Laboratory's airborne synthetic aperture radar (SAR). Hydrographic measurements show an abrupt surface front separating warm, salty Gulf Stream water in the south from a filament of cool, fresh (<33 practical salinity unit (psu)) water to the north. The filament lies within the stream and is likely water entrained from the continental shelf. The southern boundary of the filament is marked by increased surface wave breaking in a 100- to 200-m-wide zone, accumulations of Sargassum, and an orthogonal velocity change of 20 cm/s. The front is manifested in a sequence of SAR images as a narrow line having returns 1-2 dB higher than background. (A second, transient SAR line occurs near the northern filament boundary.) The observations are compared with model calculations of the surface wave hydrodynamics and radar scattering. The ocean waves are driven by southwesterly 8-m/s winds and interact with the front to produce primarily an enhancement of 2- to 3-m waves over a ≲200-m-wide region centered downwind of the front. Using a composite scattering radar model along with measured breaking-wave statistics, we show that the observed modulations in the radar backscatter can be accounted for through breaking-wave and tilted Bragg wave scattering effects. These results further show that SAR images of the ocean surface can be exploited for detailed study of particular ocean processes.

  2. Identifying tropical mountain wetlands with Asymmetric Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Buytaert, W.; Schumann, G.

    2009-04-01

    Land cover classification in remote areas is often done with remotely sensed data. However, on classic spectrometer data, wetlands are difficult to distinguish from neighbouring grass and shrubland vegetation, despite the differences in hydrological regime and species variety. Another problem with spectrometer data is the interference of cloud cover, which is abundant in the areas where wetlands tend to occur. Radar measurements, which are not affected by cloud cover, are sensitive to soil moisture. As such, they have the potential to identify wetlands from well drained grasslands. In this study, Asymmetric Synthetic Aperture Radar from the ESA ENVISAT satellite are used to identify wetlands in the Ecuadorian paramo ecosystem. This ecosystem occurs above the treeline (3500 m) and is characterised by highly intermingled grass- and wetlands. By comparing ASAR data from different months, hydrologically active zones can be identified. Corroboration with field observations and rain gauge data show that the areas identified with ASAR coincide with locations with a high tendency for saturation and ponding. By linking precipitation data from local raingauges with the ASAR images, the hydrological regime of the area can be characterised. This information is valuable for hydrological and ecological studies, particularly in the paramo region, which has an important water supply function and is a hotspot for biodiversity.

  3. New formulation for interferometric synthetic aperture radar for terrain mapping

    SciTech Connect

    Jakowatz, C.V. Jr.; Wahl, D.E.; Eichel, P.H.; Thompson, P.A.

    1994-04-01

    The subject of interferometric synthetic aperture radar (IFSAR) for high-accuracy terrain elevation mapping continues to gain importance in the arena of radar signal processing. Applications to problems in precision terrain-aided guidance and automatic target recognition, as well as a variety of civil applications, are being studied by a number of researchers. Not unlike many other areas of SAR processing, the subject of IFSAR can at first glance appear to be somewhat mysterious. In this paper we show how the mathematics of IFSAR for terrain elevation mapping using a pair of spotlight mode SAR collections can be derived in a very straightforward manner. Here, we employ an approach that relies entirely on three-dimensional Fourier transforms, and utilizes no reference to range equations or Doppler concepts. The result is a simplified explanation of the fundamentals of interferometry, including an easily-seen link between image domain phase difference and terrain elevation height. The derivation builds upon previous work by the authors in which a framework for spotlight mode SAR image formation based on an analogy to three-dimensional computerized axial tomography (CAT) was developed. After outlining the major steps in the mathematics, we show how a computer simulator which utilizes three-dimensional Fourier transforms can be constructed that demonstrates all of the major aspects of IFSAR from spotlight mode collections.

  4. Three-dimensional subsurface imaging synthetic aperture radar

    SciTech Connect

    Moussally, G.J.

    1995-03-01

    The objective of this applied research and development project is to develop a system known as `3-D SISAR`. This system consists of a ground penetrating radar with software algorithms designed for the detection, location, and identification of buried objects in the underground hazardous waste environments found at DOE storage sites. Three-dimensional maps of the object locations will be produced which can assist the development of remediation strategies and the characterization of the digface during remediation operations. It is expected that the 3-D SISAR will also prove useful for monitoring hydrocarbon based contaminant migration after remediation. The underground imaging technique being developed under this contract utilizes a spotlight mode Synthetic Aperture Radar (SAR) approach which, due to its inherent stand-off capability, will permit the rapid survey of a site and achieve a high degree of productivity over large areas. When deployed from an airborne platform, the stand-off techniques is also seen as a way to overcome practical survey limitations encountered at vegetated sites.

  5. Synthetic aperture radar: not just a sensor of last resort

    NASA Astrophysics Data System (ADS)

    Wells, Lars M.; Doerry, Armin W.

    2003-08-01

    Modern high-performance Synthetic Aperture Radar (SAR) systems have evolved into highly versatile, robust, and reliable tactical sensors, offering images and information not available from other sensor systems. For example, real-time images are routinely formed by the Sandia-designed General Atomics (AN/APY-8) Lynx SAR yielding 4-inch resolution at 25 km range (representing better than arc-second resolutions) in clouds, smoke, and rain. Sandia's Real-Time Visualization (RTV) program operates an Interferometric SAR (IFSAR) system that forms three-dimensional (3D) topographic maps in near real-time with National Imagery and Mapping Agency (NIMA) Digital Terrain Elevation Data (DTED) level 4 performance (3 meter post spacing with 0.8-meter height accuracy) or better. When exported to 3-D rendering software, this data allows remarkable interactive fly-through experiences. Coherent Change Detection (CCD) allows detecting tire tracks on dirt roads, foot-prints, and other minor, otherwise indiscernible ground disturbances long after their originators have left the scene. Ground Moving Target Indicator (GMTI) radar modes allow detecting and tracking moving vehicles. A Sandia program known as "MiniSAR" is developing technologies that are expected to culminate in a fully functioning, high-performance, real-time SAR that weighs less than 20 lbs. The purpose of this paper is to provide an overview of recent technology developments, as well as current on-going research and development efforts at Sandia National Laboratories.

  6. Interferometric synthetic aperture radar: building tomorrow's tools today

    USGS Publications Warehouse

    Lu, Zhong

    2006-01-01

    A synthetic aperture radar (SAR) system transmits electromagnetic (EM) waves at a wavelength that can range from a few millimeters to tens of centimeters. The radar wave propagates through the atmosphere and interacts with the Earth’s surface. Part of the energy is reflected back to the SAR system and recorded. Using a sophisticated image processing technique, called SAR processing (Curlander and McDonough, 1991), both the intensity and phase of the reflected (or backscattered) signal of each ground resolution element (a few meters to tens of meters) can be calculated in the form of a complex-valued SAR image representing the reflectivity of the ground surface. The amplitude or intensity of the SAR image is determined primarily by terrain slope, surface roughness, and dielectric constants, whereas the phase of the SAR image is determined primarily by the distance between the satellite antenna and the ground targets, slowing of the signal by the atmosphere, and the interaction of EM waves with ground surface. Interferometric SAR (InSAR) imaging, a recently developed remote sensing technique, utilizes the interaction of EM waves, referred to as interference, to measure precise distances. Very simply, InSAR involves the use of two or more SAR images of the same area to extract landscape topography and its deformation patterns.

  7. Synthetic aperture radar signal processing on the MPP

    NASA Technical Reports Server (NTRS)

    Ramapriyan, H. K.; Seiler, E. J.

    1987-01-01

    Satellite-borne Synthetic Aperture Radars (SAR) sense areas of several thousand square kilometers in seconds and transmit phase history signal data several tens of megabits per second. The Shuttle Imaging Radar-B (SIR-B) has a variable swath of 20 to 50 km and acquired data over 100 kms along track in about 13 seconds. With the simplification of separability of the reference function, the processing still requires considerable resources; high speed I/O, large memory and fast computation. Processing systems with regular hardware take hours to process one Seasat image and about one hour for a SIR-B image. Bringing this processing time closer to acquisition times requires an end-to-end system solution. For the purpose of demonstration, software was implemented on the present Massively Parallel Processor (MPP) configuration for processing Seasat and SIR-B data. The software takes advantage of the high processing speed offered by the MPP, the large Staging Buffer, and the high speed I/O between the MPP array unit and the Staging Buffer. It was found that with unoptimized Parallel Pascal code, the processing time on the MPP for a 4096 x 4096 sample subset of signal data ranges between 18 and 30.2 seconds depending on options.

  8. Fourier-domain multichannel autofocus for synthetic aperture radar.

    PubMed

    Liu, Kuang-Hung; Munson, David C

    2011-12-01

    Synthetic aperture radar (SAR) imaging suffers from image focus degradation in the presence of phase errors in the received signal due to unknown platform motion or signal propagation delays. We present a new autofocus algorithm, termed Fourier-domain multichannel autofocus (FMCA), that is derived under a linear algebraic framework, allowing the SAR image to be focused in a noniterative fashion. Motivated by the mutichannel autofocus (MCA) approach, the proposed autofocus algorithm invokes the assumption of a low-return region, which generally is provided within the antenna sidelobes. Unlike MCA, FMCA works with the collected polar Fourier data directly and is capable of accommodating wide-angle monostatic SAR and bistatic SAR scenarios. Most previous SAR autofocus algorithms rely on the prior assumption that radar's range of look angles is small so that the phase errors can be modeled as varying along only one dimension in the collected Fourier data. And, in some cases, implicit assumptions are made regarding the SAR scene. Performance of such autofocus algorithms degrades if the assumptions are not satisfied. The proposed algorithm has the advantage that it does not require prior assumptions about the range of look angles, nor characteristics of the scene. PMID:21606028

  9. Logarithmic Laplacian Prior Based Bayesian Inverse Synthetic Aperture Radar Imaging

    PubMed Central

    Zhang, Shuanghui; Liu, Yongxiang; Li, Xiang; Bi, Guoan

    2016-01-01

    This paper presents a novel Inverse Synthetic Aperture Radar Imaging (ISAR) algorithm based on a new sparse prior, known as the logarithmic Laplacian prior. The newly proposed logarithmic Laplacian prior has a narrower main lobe with higher tail values than the Laplacian prior, which helps to achieve performance improvement on sparse representation. The logarithmic Laplacian prior is used for ISAR imaging within the Bayesian framework to achieve better focused radar image. In the proposed method of ISAR imaging, the phase errors are jointly estimated based on the minimum entropy criterion to accomplish autofocusing. The maximum a posterior (MAP) estimation and the maximum likelihood estimation (MLE) are utilized to estimate the model parameters to avoid manually tuning process. Additionally, the fast Fourier Transform (FFT) and Hadamard product are used to minimize the required computational efficiency. Experimental results based on both simulated and measured data validate that the proposed algorithm outperforms the traditional sparse ISAR imaging algorithms in terms of resolution improvement and noise suppression. PMID:27136551

  10. Logarithmic Laplacian Prior Based Bayesian Inverse Synthetic Aperture Radar Imaging.

    PubMed

    Zhang, Shuanghui; Liu, Yongxiang; Li, Xiang; Bi, Guoan

    2016-01-01

    This paper presents a novel Inverse Synthetic Aperture Radar Imaging (ISAR) algorithm based on a new sparse prior, known as the logarithmic Laplacian prior. The newly proposed logarithmic Laplacian prior has a narrower main lobe with higher tail values than the Laplacian prior, which helps to achieve performance improvement on sparse representation. The logarithmic Laplacian prior is used for ISAR imaging within the Bayesian framework to achieve better focused radar image. In the proposed method of ISAR imaging, the phase errors are jointly estimated based on the minimum entropy criterion to accomplish autofocusing. The maximum a posterior (MAP) estimation and the maximum likelihood estimation (MLE) are utilized to estimate the model parameters to avoid manually tuning process. Additionally, the fast Fourier Transform (FFT) and Hadamard product are used to minimize the required computational efficiency. Experimental results based on both simulated and measured data validate that the proposed algorithm outperforms the traditional sparse ISAR imaging algorithms in terms of resolution improvement and noise suppression. PMID:27136551

  11. Mapping of boreal forest biomass from spaceborne synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Ranson, K. Jon; Sun, Guoqing; Lang, Roger H.; Chauhan, Narinder S.; Cacciola, Randal J.; Kilic, Ozlem

    1997-12-01

    As part of the Boreal-Ecosystem Atmosphere Study (BOREAS), an investigation is being made of the use of satellite data including shuttle imaging radar-C (SIR-C), X-band synthetic aperture radar (XSAR), and Landsat-Thematic Mapper data for estimating total and component aboveground woody biomass in boreal forest study sites in Canada. The goal of this paper is to present progress in mapping above ground woody biomass over portions of the BOREAS southern study area using spaceborne sensor data. Relationships of backscatter to total biomass and total biomass to foliage, branch, and bole biomass are used to estimate biomass across the landscape. The procedure involves image classification with SAR and Landsat data and development of simple mapping techniques using combinations of SAR channels. The analysis uses measurements from forest stands representing a range of biomass and structures. Field measurements included plot level mensuration (species, stem diameter, height, density, and basal area) and tree geometry measurements (leaf, branch, bole size, and angle distributions). The results indicate that aboveground biomass can be estimated to within about 1.6 kg/m2 and up to about 15 kg/m2 across the SIR-C image evaluated. A general method produced equivalent results with those obtained by treating forest type (pine, spruce, and aspen) separately. The biomass mapping was extended to bole, branch, and foliage components from relationships with total aboveground biomass developed from detailed tree measurements. Average biomass within the imaged area was estimated to be about 7.3 kg/m2 with biomass components of bole, branch, and foliage comprising 83, 12, and 5% of the total. Examination of the scaling of biomass estimates from remote sensing images of varying resolution shows that information at scales useful for ecosystem models can be obtained. In addition, the biomass estimation technique provides similar information at different image resolutions.

  12. Feasibility of Using Synthetic Aperture Radar to Aid UAV Navigation.

    PubMed

    Nitti, Davide O; Bovenga, Fabio; Chiaradia, Maria T; Greco, Mario; Pinelli, Gianpaolo

    2015-01-01

    This study explores the potential of Synthetic Aperture Radar (SAR) to aid Unmanned Aerial Vehicle (UAV) navigation when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. This problem can affect medium-altitude long-endurance (MALE) UAV class, which permits heavy and wide payloads (as required by SAR) and flights for thousands of kilometres accumulating large drifts. The basic idea is to infer position and attitude of an aerial platform by inspecting both amplitude and phase of SAR images acquired onboard. For the amplitude-based approach, the system navigation corrections are obtained by matching the actual coordinates of ground landmarks with those automatically extracted from the SAR image. When the use of SAR amplitude is unfeasible, the phase content can be exploited through SAR interferometry by using a reference Digital Terrain Model (DTM). A feasibility analysis was carried out to derive system requirements by exploring both radiometric and geometric parameters of the acquisition setting. We showed that MALE UAV, specific commercial navigation sensors and SAR systems, typical landmark position accuracy and classes, and available DTMs lead to estimated UAV coordinates with errors bounded within ±12 m, thus making feasible the proposed SAR-based backup system. PMID:26225977

  13. Feasibility of Using Synthetic Aperture Radar to Aid UAV Navigation

    PubMed Central

    Nitti, Davide O.; Bovenga, Fabio; Chiaradia, Maria T.; Greco, Mario; Pinelli, Gianpaolo

    2015-01-01

    This study explores the potential of Synthetic Aperture Radar (SAR) to aid Unmanned Aerial Vehicle (UAV) navigation when Inertial Navigation System (INS) measurements are not accurate enough to eliminate drifts from a planned trajectory. This problem can affect medium-altitude long-endurance (MALE) UAV class, which permits heavy and wide payloads (as required by SAR) and flights for thousands of kilometres accumulating large drifts. The basic idea is to infer position and attitude of an aerial platform by inspecting both amplitude and phase of SAR images acquired onboard. For the amplitude-based approach, the system navigation corrections are obtained by matching the actual coordinates of ground landmarks with those automatically extracted from the SAR image. When the use of SAR amplitude is unfeasible, the phase content can be exploited through SAR interferometry by using a reference Digital Terrain Model (DTM). A feasibility analysis was carried out to derive system requirements by exploring both radiometric and geometric parameters of the acquisition setting. We showed that MALE UAV, specific commercial navigation sensors and SAR systems, typical landmark position accuracy and classes, and available DTMs lead to estimate UAV coordinates with errors bounded within ±12 m, thus making feasible the proposed SAR-based backup system. PMID:26225977

  14. UHF Microstrip Antenna Array for Synthetic- Aperture Radar

    NASA Technical Reports Server (NTRS)

    Thomas, Robert F.; Huang, John

    2003-01-01

    An ultra-high-frequency microstrippatch antenna has been built for use in airborne synthetic-aperture radar (SAR). The antenna design satisfies requirements specific to the GeoSAR program, which is dedicated to the development of a terrain-mapping SAR system that can provide information on geology, seismicity, vegetation, and other terrain-related topics. One of the requirements is for ultra-wide-band performance: the antenna must be capable of operating with dual linear polarization in the frequency range of 350 plus or minus 80 MHz, with a peak gain of 10 dB at the middle frequency of 350 MHz and a gain of at least 8 dB at the upper and lower ends (270 and 430 MHz) of the band. Another requirement is compactness: the antenna must fit in the wingtip pod of a Gulfstream II airplane. The antenna includes a linear array of microstrip-patch radiating elements supported over square cavities. Each patch is square (except for small corner cuts) and has a small square hole at its center.

  15. Target discrimination in synthetic aperture radar using artificial neural networks.

    PubMed

    Principe, J C; Kim, M; Fisher, M

    1998-01-01

    This paper addresses target discrimination in synthetic aperture radar (SAR) imagery using linear and nonlinear adaptive networks. Neural networks are extensively used for pattern classification but here the goal is discrimination. We show that the two applications require different cost functions. We start by analyzing with a pattern recognition perspective the two-parameter constant false alarm rate (CFAR) detector which is widely utilized as a target detector in SAR. Then we generalize its principle to construct the quadratic gamma discriminator (QGD), a nonparametrically trained classifier based on local image intensity. The linear processing element of the QCD is further extended with nonlinearities yielding a multilayer perceptron (MLP) which we call the NL-QGD (nonlinear QGD). MLPs are normally trained based on the L(2) norm. We experimentally show that the L(2) norm is not recommended to train MLPs for discriminating targets in SAR. Inspired by the Neyman-Pearson criterion, we create a cost function based on a mixed norm to weight the false alarms and the missed detections differently. Mixed norms can easily be incorporated into the backpropagation algorithm, and lead to better performance. Several other norms (L(8), cross-entropy) are applied to train the NL-QGD and all outperformed the L(2) norm when validated by receiver operating characteristics (ROC) curves. The data sets are constructed from TABILS 24 ISAR targets embedded in 7 km(2) of SAR imagery (MIT/LL mission 90). PMID:18276330

  16. Lynx: A High-Resolution Synthetic Aperture Radar

    SciTech Connect

    Doerry, A.W.; Hensley, W.H.; Pace, F.; Stence, J.; Tsunoda, S.I.; Walker, B.C.; Woodring, M.

    1999-03-08

    Lynx is a high resolution, synthetic aperture radar (SAR) that has been designed and built by Sandia National Laboratories in collaboration with General Atomics (GA). Although Lynx may be operated on a wide variety of manned and unmanned platforms, it is primarily intended to be fielded on unmanned aerial vehicles. In particular, it may be operated on the Predator, I-GNAT, or Prowler II platforms manufactured by GA Aeronautical Systems, Inc. The Lynx production weight is less than 120 lb. and has a slant range of 30 km (in 4 mm/hr rain). It has operator selectable resolution and is capable of 0.1 m resolution in spotlight mode and 0.3 m resolution in stripmap mode. In ground moving target indicator mode, the minimum detectable velocity is 6 knots with a minimum target cross-section of 10 dBsm. In coherent change detection mode, Lynx makes registered, complex image comparisons either of 0.1 m resolution (minimum) spotlight images or of 0.3 m resolution (minimum) strip images. The Lynx user interface features a view manager that allows it to pan and zoom like a video camera. Lynx was developed under corporate finding from GA and will be manufactured by GA for both military and commercial applications. The Lynx system architecture will be presented and some of its unique features will be described. Imagery at the finest resolutions in both spotlight and strip modes have been obtained and will also be presented.

  17. Flight test of a synthetic aperture radar antenna using STEP

    NASA Technical Reports Server (NTRS)

    Zimcik, D. G.; Vigeron, F. R.; Ahmed, S.

    1984-01-01

    To establish confidence in its overall performance, credible information on the synthetic aperture radar antenna's mechanical properties in orbit must be obtained. However, the antenna's size, design, and operating environment make it difficult to simulate operating conditions under 1-g Earth conditions. The Space Technology Experiments Platform (STEP) offers a timely opportunity to mechanically qualify and characterize the antenna design in a representative environment. The proposed experimental configuration would employ a half-system of the full-scale RADARSAT antenna which would be mounted on the STEP platform in the orbiter cargo bay such that it could be deployed and retracted in orbit (as shown in this figure). The antenna would be subjected to typical environmental exposures while an array of targets and sensors on the antenna support structure and reflecting surface are observed and monitored. In particular, the typical environments would include deployment and retraction, dynamic response to vehicle thruster or base exciter inputs, and thermal soak and transient effects upon entering or exiting Earth eclipse. The proposed experiment would also provide generic information on the properties of large space structures in space and on techniques to obtain the desired information.

  18. Range ambiguity suppression technique for the spaceborne synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Jha, A. M.; Majmudar, Archana; Pillai, N. S.

    1988-10-01

    The aim of any spaceborne Synthetic Aperture Radar (SAR) system design is to keep the range ambiguous responses as low as possible. A higher value of range ambiguity deteriorates the SAR image quality. The wider swath requirement at higher incidence angle (greater than 45 deg) deteriorates the range ambiguity ratio (RAR) and hence the image quality of SAR quite significantly. The requirement of minimum acceptable RAR even for very nominal swath at these incidence angles may necessitate larger antenna width, very complex weighting, and highly asymmetrical antenna elevation pattern. An alternate scheme is suggested in this paper to alleviate the criticality and complexity of the design aspects for such a requirement. Here, the chirp slope of the transmitted linear frequency modulated pulses is reversed alternately. Hence, during the range compression, a significant portion of the ambiguous return is suppressed due to the mismatching with the signal reference function. The proposed method provides significant improvement in RAR and can be utilized in attaining wider swath, specifically at higher incidence angles.

  19. Synthetic aperture radar autofocus based on a bilinear model.

    PubMed

    Liu, Kuang-Hung; Wiesel, Ami; Munson, David C

    2012-05-01

    Autofocus algorithms are used to restore images in nonideal synthetic aperture radar imaging systems. In this paper, we propose a bilinear parametric model for the unknown image and the nuisance phase parameters and derive an efficient maximum-likelihood autofocus (MLA) algorithm. In the special case of a simple image model and a narrow range of look angles, MLA coincides with the successful multichannel autofocus (MCA). MLA can be interpreted as a generalization of MCA to a larger class of models with a larger range of look angles. We analyze its advantages over previous extensions of MCA in terms of identifiability conditions and noise sensitivity. As a byproduct, we also propose numerical approximations to the difficult constant modulus quadratic program that lies at the core of these algorithms. We demonstrate the superior performance of our proposed methods using computer simulations in both the correct and mismatched system models. MLA performs better than other methods, both in terms of the mean squared error and visual quality of the restored image. PMID:22249713

  20. Sources of Artefacts in Synthetic Aperture Radar Interferometry Data Sets

    NASA Astrophysics Data System (ADS)

    Becek, K.; Borkowski, A.

    2012-07-01

    In recent years, much attention has been devoted to digital elevation models (DEMs) produced using Synthetic Aperture Radar Interferometry (InSAR). This has been triggered by the relative novelty of the InSAR method and its world-famous product—the Shuttle Radar Topography Mission (SRTM) DEM. However, much less attention, if at all, has been paid to sources of artefacts in SRTM. In this work, we focus not on the missing pixels (null pixels) due to shadows or the layover effect, but rather on outliers that were undetected by the SRTM validation process. The aim of this study is to identify some of the causes of the elevation outliers in SRTM. Such knowledge may be helpful to mitigate similar problems in future InSAR DEMs, notably the ones currently being developed from data acquired by the TanDEM-X mission. We analysed many cross-sections derived from SRTM. These cross-sections were extracted over the elevation test areas, which are available from the Global Elevation Data Testing Facility (GEDTF) whose database contains about 8,500 runways with known vertical profiles. Whenever a significant discrepancy between the known runway profile and the SRTM cross-section was detected, a visual interpretation of the high-resolution satellite image was carried out to identify the objects causing the irregularities. A distance and a bearing from the outlier to the object were recorded. Moreover, we considered the SRTM look direction parameter. A comprehensive analysis of the acquired data allows us to establish that large metallic structures, such as hangars or car parking lots, are causing the outliers. Water areas or plain wet terrains may also cause an InSAR outlier. The look direction and the depression angle of the InSAR system in relation to the suspected objects influence the magnitude of the outliers. We hope that these findings will be helpful in designing the error detection routines of future InSAR or, in fact, any microwave aerial- or space-based survey. The presence of outliers in SRTM was first reported in Becek, K. (2008). Investigating error structure of shuttle radar topography mission elevation data product, Geophys. Res. Lett., 35, L15403.

  1. Understanding Volcanic Inflation of Long Valley Caldera, California, from Differential Synthetic Aperture Radar observations

    NASA Technical Reports Server (NTRS)

    Webb, F.; Hensley, S.; Rosen, P.; Langbein, J.

    1994-01-01

    The results using interferometric synthetic aperture radar(SAR) to measure the co-seismic displacement from the June 28, 1992 Landers earthquake suggest that this technique may be applicable to other problems in crustal deformation.

  2. Seamless Synthetic Aperture Radar Archive for Interferometry Analysis

    NASA Astrophysics Data System (ADS)

    Baker, S.; Meertens, C. M.; Phillips, D. A.; Crosby, C.; Fielding, E. J.; Nicoll, J.; Bryson, G.; Buechler, B.; Baru, C.

    2012-12-01

    The NASA Advancing Collaborative Connections for Earth System Science (ACCESS) Seamless Synthetic Aperture Radar (SAR) Archive (SSARA) project is a 2-year collaboration between UNAVCO/WInSAR, the Alaska Satellite Facility (ASF), the Jet Propulsion Laboratory (JPL), and the San Diego Supercomputer Center (SDSC) to design and implement a seamless distributed access system for SAR data and derived data products (i.e. terrain corrected interferograms). A seamless SAR archive increases the accessibility and the utility of SAR science data to solid Earth and cryospheric science researchers. Building on the established webs services and APIs at UNAVCO and ASF, the SSARA project will provide simple web services tools to seamlessly and effectively exchange and share space- and airborne SAR metadata, archived SAR data, and on-demand derived products between the distributed archives and individual users. Development of standard formats for data products and new QC/QA definitions will be implemented to streamline data usage and enable advanced query capabilities. The new ACCESS-developed tools will help overcome the obstacles of heterogeneous archive access protocols and data formats, data provider access policy constraints, and will also enable interoperability with key information technology development systems such as the NASA/JPL QuakeSim and ARIA projects, which provide higher level resources for geodetic data processing, data assimilation and modeling, and integrative analysis for scientific research and hazards applications. The SSARA project will significantly enhance mature IT capabilities at ASF's NASA-supported DAAC, the GEO Supersites archive, supported operationally by UNAVCO, and UNAVCO's WInSAR and EarthScope SAR archives that are supported by NASA, NSF, and the USGS in close collaboration with ESA/ESRIN.

  3. Synthetic aperture radar interferometry: a Markovian approach for phase unwrapping

    NASA Astrophysics Data System (ADS)

    Labrousse, David; Dupont, Stephane; Berthod, Marc

    1995-07-01

    Observation of interferometric images provided by Synthetic Aperture Radar satellites enables the reconstruction of Digital Elevation Model of an area. The elevation of a ground point is computed from the interferogram which is the phase difference of two signals backscattered from the same point and emitted from two different positions of the satellite. Since the phase difference may only be measured module 2 (pi) , the problem consists of estimating the unwrapped phase for each point, that is the number of complete cycles of the phase. Here, we present a solution for this problem which is based on a Markovian approach allowing a combination of global and local constraints. As in regularization technics an energy function is defined as the sum of two potential functions. The first potential measures an error with respect to an a priori model (here, the membrane model). The second potential measures an error with respect to the data (i.e. the interferogram). The optimal labeling with respect to this non-convex energy is then computed by a simulated annealing process. The computational cost of this relaxation technique is particularly heavy in phase unwrapping. This is due to the residual gray level difference between the unwrapped phase image and the data. Therefore, we first employ a deterministic algorithm, which is faster but may propagate some errors, before applying our stochastic algorithm which should correct most of those errors. This algorithm was implemented on the Connection Machine CM-200 and applied on numerous examples presenting cases of discontinuities. The results are quite satisfactory from many points of view: robustness, sensitivity to noise and presence of discontinuities.

  4. Ice island detection and characterization with airborne synthetic aperture radar

    SciTech Connect

    Jeffries, M.O.; Sackinger, W.M. )

    1990-04-15

    A 1:300,000 scale airborne synthetic aperture radar (SAR) image of an area of the Arctic Ocean adjacent to the Queen Elizabeth Islands, Canadian High Arctic, is examined to determine the number and characteristics of ice islands in the image and to assess the capability of airborne and satellite SAR to detect ice islands. Twelve ice islands have been identified, and their dimensions range from as large as 5.7 km by 8.7 km to as small as 0.15 km by 0.25 km. A significant SAR characteristic of the shelf ice portions of ice islands is a return with a ribbed texture of alternating lighter and darker grey tones resulting from the indulating shelf ice surfaces of the ice islands. The appearance of the ribbed texture varies according to the ice islands' orientation relative to the illumination direction and consequently the incidence angle. Some ice islands also include extensive areas of textureless dark tone attached to the shelf ice. The weak returns correspond to (1) multiyear landfast sea ice that was attached to the front of the Ward Hunt Ice Shelf at the time of calving and which has remained attached since then and (2) multiyear pack ice that has become attached and consolidated since the calving, indicating that ice islands can increase their area and mass significantly as they drift. Ice islands are easily discernible in SAR images and for the future SAR represents a promising technique to obtain a census of ice islands in the Arctic Ocean. However, any SAR-based census probably will be conservative because ice islands smaller than 300-400 m across are likely to remain undetected, particularly in areas of heavy ice ridging which produces strong SAR clutter.

  5. Tundra Fire Effects Mapping from Synthetic Aperture Radar Satellite Data

    NASA Astrophysics Data System (ADS)

    Jenkins, L. K.; Bourgeau-Chavez, L. L.; French, N. H.; Loboda, T. V.; Chavez, M. C.; Hawkins, S. M.

    2013-12-01

    Traditional electro-optical, satellite-based methods of fire detection and monitoring are severely limited in the arctic due to persistent cloud cover and short growing seasons. Radar data can provide an alternative to traditional electro-optical methods due to all-weather imaging capabilities. Previous research in boreal forests and current evaluation in the Alaskan tundra shows that synthetic aperture radar (SAR) data can be used successfully to map burn perimeters and distinguish burned and unburned areas within the perimeter over a longer period of time than optical sensors. Results will be presented on the use of SAR data to measure spatial variations in the microwave signature across a fire scar as well as temporally throughout the growing season and across multiple years. The extensive historical archive of ERS-1 and -2 SAR data has been used to characterize three burned areas in the tundra regions of Alaska. These fires include the 1993 Wainwright fires in the north-western part of the North Slope (Fig 1), the 1999 Uvgoon fire in the Noatak National Preserve and 2007 Anaktuvuk River fire north of the Brooks Range in the central area of the North Slope. The data record includes pre-burn, burn, and post-burn observations until the fire scars are no longer discernible on the landscape. Our results show that burned areas are visible reliably five years post burn and then faintly apparent thereafter up to 12 or more years post-burn. Conversely, our analysis of electro-optical (Landsat) imagery shows near complete obscuration of the fire scar one year post-burn (Loboda et al. 2013). Also presented are results of an analysis of the effects of post-fire soil moisture, as measured in weather and climate datasets, on the SAR signature measured from the available image data archive. Reference: Loboda, T L, N H F French, C Hight-Harf, L Jenkins, M E Miller. 2013. Mapping fire extent and burn severity in Alaskan tussock tundra: An analysis of the spectral response of tundra vegetation to wildland fire. Remote Sens. Enviro. 134:194-209. Figure 1: 1993 Wainwright fires shown one year (top) and four years (bottom) post-fire in ERS-1 SAR image

  6. High Resolution Ionospheric Mapping Using Spaceborne Synthetic Aperture Radars

    NASA Astrophysics Data System (ADS)

    Meyer, F. J.; Chotoo, K.; Roth, A. P.

    2012-12-01

    Spaceborne Synthetic Aperture Radars (SARs) are imaging radar systems that utilize the Doppler history of signals acquired during satellite flyby to produce high resolution images of the Earth. With modern sensors, operating at frequencies between about 1 GHz (L-band) and 10 GHz (X-band), radar images with resolutions in the meter to sub-meter range can be produced. The presence of the ionosphere is significantly affecting the propagation properties of the microwave signals transmitted by these systems, causing distortions of signal polarization and phase. These distortions can lead to a wide range of imaging artifacts including image range shifts, interferometric phase biases, loss of image focus, change of image geometry, and Faraday rotation. While these artifacts are particularly pronounced at L-band, they are still observable in data acquired at C- or even X-band. In recent years, a wealth of methods for measuring and correcting ionospheric influence were developed. These methods are self-calibration procedures that measure ionosphere-induced distortions to infer the two-dimensional TEC maps that affected the data. These TEC maps are then removed from the data to produce high performance SAR images. Besides being effective in correcting SAR observations, these self-calibration methods are producing high quality TEC information with sub-TECU sensitivity and sub-kilometer spatial resolution. The intent of this paper is to utilize SAR-derived ionospheric information and make the case for SAR as a data source for ionospheric research. After a short summary of ionosphere-induced distortions, the concept of TEC estimation from SAR is introduced. Here, the current state-of-the-art of ionospheric TEC estimation is presented, including Faraday rotation-based, interferometric, correlation-based, and autofocus-based techniques. For every approach, performance numbers are given that quantify the achievable TEC estimation accuracy as a function of system parameters, scene properties, and (if applicable) geographic location. Three case studies will be presented to highlight the type and quality of ionospheric information that can be retrieved: (1) The high spatial resolution of SAR-derived TEC maps is emphasized in a case study that focuses on high resolution mapping of aurora arcs in central Alaska. Here, TEC enhancements associated with aurora activity are mapped and compared to reference observations from sky cameras and GPS; (2) observations of mid-latitudal traveling ionospheric disturbances are shown to showcase the accuracy of SAR-derived TEC maps. Several SAR-based TEC mapping methods are compared to highlight their respective advantages and disadvantages regarding processing complexity and estimation accuracy; (3) a third example focuses on analyzing post-sunset scintillation phenomena in equatorial regions. SAR is used to assess the frequency of occurrence of scintillation and analyze their associated power spectra. To conclude the paper, the temporal and spatial sampling of the ionosphere provided by the fleet of current and future spaceborne SAR sensors is analyzed to provide an assessment of the global ionospheric mapping capabilities of SAR.

  7. Model-Based Information Extraction From Synthetic Aperture Radar Signals

    NASA Astrophysics Data System (ADS)

    Matzner, Shari A.

    2011-07-01

    Synthetic aperture radar (SAR) is a remote sensing technology for imaging areas of the earth's surface. SAR has been successfully used for monitoring characteristics of the natural environment such as land cover type and tree density. With the advent of higher resolution sensors, it is now theoretically possible to extract information about individual structures such as buildings from SAR imagery. This information could be used for disaster response and security-related intelligence. SAR has an advantage over other remote sensing technologies for these applications because SAR data can be collected during the night and in rainy or cloudy conditions. This research presents a model-based method for extracting information about a building -- its height and roof slope -- from a single SAR image. Other methods require multiple images or ancillary data from specialized sensors, making them less practical. The model-based method uses simulation to match a hypothesized building to an observed SAR image. The degree to which a simulation matches the observed data is measured by mutual information. The success of this method depends on the accuracy of the simulation and on the reliability of the mutual information similarity measure. Electromagnetic theory was applied to relate a building's physical characteristics to the features present in a SAR image. This understanding was used to quantify the precision of building information contained in SAR data, and to identify the inputs needed for accurate simulation. A new SAR simulation technique was developed to meet the accuracy and efficiency requirements of model-based information extraction. Mutual information, a concept from information theory, has become a standard for measuring the similarity between medical images. Its performance in the context of matching a simulation image to a SAR image was evaluated in this research, and it was found to perform well under certain conditions. The factors that affect its performance, and the model-based method overall, were found to include the size of the building and its orientation. Further refinements that expand the range of operational conditions for the method would lead to a practical tool for collecting information about buildings using SAR technology. This research was performed using SAR data from MIT-Lincoln Laboratory.

  8. Ice island detection and characterization with airborne synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Jeffries, M. O.; Sackinger, W. M.

    1990-04-01

    A 1∶300,000 scale airborne synthetic aperture radar (SAR) image of an area of the Arctic Ocean adjacent to the Queen Elizabeth Islands, Canadian High Arctic, is examined to determine the number and characteristics of ice islands in the image and to assess the capability of airborne and satellite SAR to detect ice islands. Twelve ice islands have been identified, and their dimensions range from as large as 5.7 km by 8.7 km to as small as 0.15 km by 0.25 km. A significant SAR characteristic of the shelf ice portions of ice islands is a return with a ribbed texture of alternating lighter and darker grey tones resulting from the undulating shelf ice surfaces of the ice islands. The appearance of the ribbed texture varies according to the ice islands' orientation relative to the illumination direction and consequently the incidence angle. Some ice islands also include extensive areas of textureless dark tone attached to the shelf ice. The weak returns correspond to (1) multiyear landfast sea ice that was attached to the front of the Ward Hunt Ice Shelf at the time of calving and which has remained attached since then and (2) multiyear pack ice that has become attached and consolidated since the calving, indicating that ice islands can increase their area and mass significantly as they drift. Other SAR characteristics include straight, bright returns along the edges arising from sea ice pressure ridges or shelf ice cliffs. Other physical characteristics of ice islands that make them identifiable in SAR images include their greater size and shapes longer, thinner, and more angular than those of surrounding pack ice floes. It is evident that ice islands are easily discernible in SAR images and for the future SAR represents a promising technique to obtain a census of ice islands in the Arctic Ocean. However, any SAR-based census probably will be conservative because ice islands smaller than 300-400 m across are likely to remain undetected, particularly in areas of heavy ice ridging which produces strong SAR clutter.

  9. Phase correction system for automatic focusing of synthetic aperture radar

    DOEpatents

    Eichel, Paul H.; Ghiglia, Dennis C.; Jakowatz, Jr., Charles V.

    1990-01-01

    A phase gradient autofocus system for use in synthetic aperture imaging accurately compensates for arbitrary phase errors in each imaged frame by locating highlighted areas and determining the phase disturbance or image spread associated with each of these highlight areas. An estimate of the image spread for each highlighted area in a line in the case of one dimensional processing or in a sector, in the case of two-dimensional processing, is determined. The phase error is determined using phase gradient processing. The phase error is then removed from the uncorrected image and the process is iteratively performed to substantially eliminate phase errors which can degrade the image.

  10. Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures

    NASA Astrophysics Data System (ADS)

    Bleszynski, E.; Bleszynski, M.; Jaroszewicz, T.

    2013-05-01

    An approach to autofocusing for large curved synthetic aperture radar (SAR) apertures is presented. Its essential feature is that phase corrections are being extracted not directly from SAR images, but rather from reconstructed SAR phase-history data representing windowed patches of the scene, of sizes sufficiently small to allow the linearization of the forward- and back-projection formulae. The algorithm processes data associated with each patch independently and in two steps. The first step employs a phase-gradient-type method in which phase correction compensating (possibly rapid) trajectory perturbations are estimated from the reconstructed phase history for the dominant scattering point on the patch. The second step uses phase-gradient-corrected data and extracts the absolute phase value, removing in this way phase ambiguities and reducing possible imperfections of the first stage, and providing the distances between the sensor and the scattering point with accuracy comparable to the wavelength. The features of the proposed autofocusing method are illustrated in its applications to intentionally corrupted small-scene 2006 Gotcha data. The examples include the extraction of absolute phases (ranges) for selected prominent point targets. They are then used to focus the scene and determine relative target-target distances.

  11. Synthetic aperture FM-CW radar applied to the detection of objects buried in snowpack

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yoshio; Mitsumoto, Masashi; Sengoku, Masakazu; Abe, Takeo

    1994-01-01

    This paper presents the principle of synthetic aperture frequency modulated continuous wave (FM-CW) radar and demonstrates the detection results of several objects buried in natural snowpack using the radar system. First, the synthetic aperture technique is explained with emphasis placed on showing that the Fourier transformed beat signal obtained by the FM-CW radar is equivalent to one kind of Fresnel hologram, which leads us to use SAR technique. Then a radar system operative in the microwave L-band is explored to detect objects buried in natural snowpack. Several detection results are presented demonstrating the potential capability of high resolution imaging in the azimuth direction, comparing with real aperture images.

  12. Bandwidth compression of synthetic aperture radar imagery by quantization of raw radar data

    NASA Technical Reports Server (NTRS)

    Lipes, R. G.; Butman, S. A.

    1977-01-01

    A study is made of the effects of quantization of the radar returns transmitted from aircraft or spacecraft employing a synthetic aperture radar system. The study is based on the output images obtained after one-bit, two-bit, and eight-bit quantizations and comparing the results to ground truth. In this way the degradation resulting from data or bandwidth reduction is determined. Quantization is evaluated in terms of crater scene, number of looks, and transmission error rate. It is found that two-bit quantization of raw radar data from homogeneous scenes processed to 32 looks yields nearly all the details of the original. One-bit quantization of raw radar data from homogeneous scenes processed to 32 looks yields a good visual representation of the scene but some fine detail is lost and the absolute reflectivity level is not reliable. Image quality is observed to improve with more looks and video and intermediate frequency quantization are not distinguishable even for one-bit quantizations. Image quality is not influenced by bit error rates less than about 2 to the -7th power.

  13. Synthetic-aperture imaging laser radar: laboratory demonstration and signal processing.

    PubMed

    Beck, Steven M; Buck, Joseph R; Buell, Walter F; Dickinson, Richard P; Kozlowski, David A; Marechal, Nicholas J; Wright, Timothy J

    2005-12-10

    The spatial resolution of a conventional imaging laser radar system is constrained by the diffraction limit of the telescope's aperture. We investigate a technique known as synthetic-aperture imaging laser radar (SAIL), which employs aperture synthesis with coherent laser radar to overcome the diffraction limit and achieve fine-resolution, long-range, two-dimensional imaging with modest aperture diameters. We detail our laboratory-scale SAIL testbed, digital signal-processing techniques, and image results. In particular, we report what we believe to be the first optical synthetic-aperture image of a fixed, diffusely scattering target with a moving aperture. A number of fine-resolution, well-focused SAIL images are shown, including both retroreflecting and diffuse scattering targets, with a comparison of resolution between real-aperture imaging and synthetic-aperture imaging. A general digital signal-processing solution to the laser waveform instability problem is described and demonstrated, involving both new algorithms and hardware elements. These algorithms are primarily data driven, without a priori knowledge of waveform and sensor position, representing a crucial step in developing a robust imaging system. PMID:16363787

  14. Two-dimensional and full polarimetric imaging by a synthetic aperture FM-CW radar

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Yoshio; Nishikawa, Toru; Sengoku, Masakazu; Boerner, Wolfgang-Martin

    1995-03-01

    This paper applies the principle of radar polarimetry to a synthetic aperture frequency-modulated continuous wave (FM-CW) radar and presents results based on two-dimensional (2-D) full polarimetric imaging. It is shown that the polarimetric target reflection coefficients obtained by the synthetic aperture FM-CW radar are elements of a Sinclair scattering matrix, although the coefficients are derived from a wide band signal. Using the scattering matrix optimization procedure, a 2-D polarimetric imaging experiment (including Co-Pol maximum, minimum, span, and phase imaging) of an orthogonally placed linear target set was successfully carried out in the laboratory. This result demonstrates the validity of X-band (8.2-9.2 GHz) FM-CW radar polarimetry, and it presents a demonstration of a full polarimetric 2-D FM-CW imaging radar system.

  15. Overview of independent component analysis technique with an application to synthetic aperture radar (SAR) imagery processing.

    PubMed

    Fiori, Simone

    2003-01-01

    We present an overview of independent component analysis, an emerging signal processing technique based on neural networks, with the aim to provide an up-to-date survey of the theoretical streams in this discipline and of the current applications in the engineering area. We also focus on a particular application, dealing with a remote sensing technique based on synthetic aperture radar imagery processing: we briefly review the features and main applications of synthetic aperture radar and show how blind signal processing by neural networks may be advantageously employed to enhance the quality of remote sensing data. PMID:12672440

  16. The measurement of precipitation with synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Atlas, David; Moore, Richard K.

    1987-01-01

    The radar equation for the measurement of precipitation by SAR is identical to that for a conventional radar. The achievable synthetic beamwidth, beta(s), is proportional to sigma(v)/U, the ratio of the spread of the precipitation Doppler spectrum to the platform velocity. Thus, a small beta(s) can be achieved only with small sigma(v) or from a fast-moving vehicle such as a spacecraft. Also, the along-track resolution is variable with sigma(v) and is not known. Nevertheless, the reflectivity is measured correctly. A possible approach to the measurement of sigma(v) is noted. The C-band SAR proposed for the SIR-C mission is capable of detecting a rain rate as small as 0.5 mm/h at nadir when the beam is filled. Because the cross-track beam dimension is about 20 km wide, the use of a high-resolution microwave radiometer to correct for the unfilled beam and the variation of gain across it is suggested. Alternatively, the cross-track dimension should be decreased to no more than about 5 km by increasing the antenna width and/or decreasing the wavelength.

  17. The DESDynI Synthetic Aperture Radar Array-Fed Reflector Antenna

    NASA Technical Reports Server (NTRS)

    Chamberlain, Neil; Ghaemi, Hirad; Giersch, Louis; Harcke, Leif; Hodges, Richard; Hoffman, James; Johnson, William; Jordan, Rolando; Khayatian, Behrouz; Rosen, Paul; Sadowy, Gregory; Shaffer, Scott; Shen, Yuhsyen; Veilleux, Louise; Wu, Patrick

    2010-01-01

    DESDynI is a mission being developed by NASA with radar and lidar instruments for Earth-orbit remote sensing. This paper focuses on the design of a largeaperture antenna for the radar instrument. The antenna comprises a deployable reflector antenna and an active switched array of patch elements fed by transmit/ receive modules. The antenna and radar architecture facilitates a new mode of synthetic aperture radar imaging called 'SweepSAR'. A system-level description of the antenna is provided, along with predictions of antenna performance.

  18. Servomechanism for Doppler shift compensation in optical correlator for synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Constaninides, N. J.; Bicknell, T. J. (Inventor)

    1980-01-01

    A method and apparatus for correcting Doppler shifts in synthetic aperture radar data is described. An optical correlator for synthetic aperture radar data has a means for directing a laser beam at a signal film having radar return pulse intensity information recorded on it. A resultant laser beam passes through a range telescope, an azimuth telescope, and a Fourier transform filter located between the range and azimuth telescopes, and forms an image for recording on an image film. A compensation means for Doppler shift in the radar return pulse intensity information includes a beam splitter for reflecting the modulated laser beam, after having passed through the Fourier transform filter, to a detection screen having two photodiodes mounted on it.

  19. Development of a synthetic aperture radar design approach for wide-swath implementation

    NASA Technical Reports Server (NTRS)

    Jean, B. R.

    1981-01-01

    The first phase of a study program to develop an advanced synthetic aperture radar design concept is presented. Attributes of particular importance for the system design include wide swath coverage, reduced power requirements, and versatility in the selection of frequency, polarization and incident angle. The multiple beam configuration provides imaging at a nearly constant angle of incidence and offers the potential of realizing a wide range of the attributes desired for an orbital imaging radar for Earth resources applications.

  20. A global search and rescue concept using synthetic aperture radar and passive user targets

    NASA Technical Reports Server (NTRS)

    Sivertson, W. E., Jr.

    1976-01-01

    A terrestrial search and rescue concept is defined embodying the use of passive radio-frequency reflectors in conjunction with an orbiting synthetic aperture radar to detect, identify, and locate users. An airborne radar test was conducted to evaluate the basic concept. In this test simple corner-reflector targets were successfully imaged. Results from this investigation were positive and indicate that the concept can be used to investigate new approaches focused on the development of a global search and rescue system.

  1. Method for providing a polarization filter for processing synthetic aperture radar image data

    NASA Technical Reports Server (NTRS)

    Dubois, Pascale C. (Inventor); Vanzyl, Jakob J. (Inventor)

    1990-01-01

    A polarization filter can maximize the signal-to-noise ratio of a polarimetric synthetic aperture radar (SAR) and help discriminate between targets or enhance image features, e.g., enhance contrast between different types of target. The method disclosed is based on the Stokes matrix/ Stokes vector representation, so the targets of interest can be extended targets, and the method can also be applied to the case of bistatic polarimetric radars.

  2. IFP V4.0:a polar-reformatting image formation processor for synthetic aperture radar.

    SciTech Connect

    Eichel, Paul H.

    2005-09-01

    IFP V4.0 is the fourth generation of an extraordinarily powerful and flexible image formation processor for spotlight mode synthetic aperture radar. It has been successfully utilized in processing phase histories from numerous radars and has been instrumental in the development of many new capabilities for spotlight mode SAR. This document provides a brief history of the development of IFP, a full exposition of the signal processing steps involved, and a short user's manual for the software implementing this latest iteration.

  3. Terahertz inverse synthetic aperture radar imaging using self-mixing interferometry with a quantum cascade laser.

    PubMed

    Lui, H S; Taimre, T; Bertling, K; Lim, Y L; Dean, P; Khanna, S P; Lachab, M; Valavanis, A; Indjin, D; Linfield, E H; Davies, A G; Rakić, A D

    2014-05-01

    We propose a terahertz (THz)-frequency synthetic aperture radar imaging technique based on self-mixing (SM) interferometry, using a quantum cascade laser. A signal processing method is employed which extracts and exploits the radar-related information contained in the SM signals, enabling the creation of THz images with improved spatial resolution. We demonstrate this by imaging a standard resolution test target, achieving resolution beyond the diffraction limit. PMID:24784063

  4. Basics of Polar-Format algorithm for processing Synthetic Aperture Radar images.

    SciTech Connect

    Doerry, Armin Walter

    2012-05-01

    The purpose of this report is to provide a background to Synthetic Aperture Radar (SAR) image formation using the Polar Format (PFA) processing algorithm. This is meant to be an aid to those tasked to implement real-time image formation using the Polar Format processing algorithm.

  5. Wavefront curvature limitations and compensation to polar format processing for synthetic aperture radar images.

    SciTech Connect

    Doerry, Armin Walter

    2006-01-01

    Limitations on focused scene size for the Polar Format Algorithm (PFA) for Synthetic Aperture Radar (SAR) image formation are derived. A post processing filtering technique for compensating the spatially variant blurring in the image is examined. Modifications to this technique to enhance its robustness are proposed.

  6. Ocean wave patterns under hurricane gloria: observation with an airborne synthetic-aperture radar.

    PubMed

    Elachi, C; Thompson, T W; King, D

    1977-11-11

    Surface imagery of ocean waves under Hurricane Gloria (September 1976) has been obtained with an airborne synthetic-aperture imaging radar. Observations were obtained over most of the area within a radius of 150 kilometers around the center of the eye. These direct observations made it possible to derive the wave patterns in the region around a hurricane eye. PMID:17819661

  7. A method for detection of deformations in large phase array antennas for spaceborne synthetic aperture radars

    NASA Technical Reports Server (NTRS)

    Li, F. K.

    1984-01-01

    A method to measure deformations in large, planar phased array antennas used in spaceborne synthetic aperture radars (SAR) is described. This method has the advantages that the deformation measurements can be performed anywhere in orbit and that no additional sensor is required. Indirect test results using the SEASAT SAR data indicate that this technique can detect deformations of small fractions of a wavelength.

  8. An atlas of November 1978 synthetic aperture radar digitized imagery for oil spill studies

    NASA Technical Reports Server (NTRS)

    Maurer, H. E.; Oderman, W.; Crosswell, W. F.

    1982-01-01

    A data set is described which consists of digitized synthetic aperture radar (SAR) imagery plus correlative data and some preliminary analysis results. This data set should be of value to experimenters who are interested in the SAR instrument and its application to the detection and monitoring of oil on water and other distributed targets.

  9. Eliminating Doppler Effects in Synthetic-Aperture Radar Optical Processors

    NASA Technical Reports Server (NTRS)

    Constantindes, N. J.; Bicknell, T. J.

    1984-01-01

    Pair of photodetectors generates correction signals. Instrument detects Doppler shifts in radar and corrects processing parameters so ambiguities caused by shifts not manifested as double or overlapping images.

  10. The Application of Airborne Synthetic Aperture Radar Imagery for Studying the Archaeology of the Mayan Biosphere.

    NASA Astrophysics Data System (ADS)

    Chapman, B. D.; Blom, R.; Golden, C.; Saatchi, S.

    2008-12-01

    In March of 2004, the NASA/JPL Airborne Synthetic Aperture Radar (AIRSAR) acquired data over much of the Mayan Biosphere in Guatamala. The AIRSAR system is a fully polarimetric and interferometric synthetic aperture radar (SAR) that can both accurately measure topography at high resolution (5 m pixels) but can also measure the reflected brightness of the underlying terrain. Since AIRSAR was also a three frequency radar, a comparison can also be made as to the relative brightness at the three wavelengths of radiation. One frequency in particular, P-band, has a wavelength of almost 1 meter, and may significantly penetrate the forest canopy to the underlying surface features. The work that will be presented here will comprise the first step in the data processing - generating an accurate topographic map, and evaluation of that topographic data. This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

  11. High-resolution planetary imaging via spotlight-mode synthetic aperture radar.

    NASA Astrophysics Data System (ADS)

    Webb, J. L. H.; Munson, D. C., Jr.; Stacy, N. J. S.

    1998-11-01

    The authors consider the application of a spotlight-mode synthetic aperture radar (SAR) imaging technique to the problem of high-resolution lunar imaging and other related radar astronomy problems. This approach offers improved image quality, compared with conventional processing, at the expense of slightly increased computational effort. Results of the processing of lunar data acquired with the 12.6 cm wavelength radar system at Arecibo Observatory are presented, and compared with the best available published result, by Stacy (1993), which uses focusing techniques from stripmap SAR.

  12. User guide to the Magellan synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Wall, Stephen D.; Mcconnell, Shannon L.; Leff, Craig E.; Austin, Richard S.; Beratan, Kathi K.; Rokey, Mark J.

    1995-01-01

    The Magellan radar-mapping mission collected a large amount of science and engineering data. Now available to the general scientific community, this data set can be overwhelming to someone who is unfamiliar with the mission. This user guide outlines the mission operations and data set so that someone working with the data can understand the mapping and data-processing techniques used in the mission. Radar-mapping parameters as well as data acquisition issues are discussed. In addition, this user guide provides information on how the data set is organized and where specific elements of the set can be located.

  13. Three-dimensional subsurface imaging Synthetic Aperture Radar

    SciTech Connect

    Wuenschel, E.

    1995-10-01

    This report describes the development of a system known as 3-D SISAR. This system consists of a ground penetrating radar with software algorithms designed for the detection, location, and identification of buried objects in the underground hazardous waste environments at DOE storage sites.

  14. Study of Synthetic Aperture Radar (SAR) imagery characteristics

    NASA Technical Reports Server (NTRS)

    1975-01-01

    Sources of geometric and radiometric fidelity errors in AN/APQ-102A radar imagery are discussed, along with a digital computer program to correct the distortions. The major effort, a computer program which will process digitalized recorded AN/APQ-102A phase histories into imagery, is described. All computer programs are listed.

  15. Target-adaptive polarimetric synthetic aperture radar target discrimination using maximum average correlation height filters.

    PubMed

    Sadjadi, Firooz A; Mahalanobis, Abhijit

    2006-05-01

    We report the development of a technique for adaptive selection of polarization ellipse tilt and ellipticity angles such that the target separation from clutter is maximized. From the radar scattering matrix [S] and its complex components, in phase and quadrature phase, the elements of the Mueller matrix are obtained. Then, by means of polarization synthesis, the radar cross section of the radar scatters are obtained at different transmitting and receiving polarization states. By designing a maximum average correlation height filter, we derive a target versus clutter distance measure as a function of four transmit and receive polarization state angles. The results of applying this method on real synthetic aperture radar imagery indicate a set of four transmit and receive angles that lead to maximum target versus clutter discrimination. These optimum angles are different for different targets. Hence, by adaptive control of the state of polarization of polarimetric radar, one can noticeably improve the discrimination of targets from clutter. PMID:16639454

  16. Phase unwrapping through fringe-line detection in synthetic aperture radar interferometry.

    PubMed

    Lin, Q; Vesecky, J F; Zebker, H A

    1994-01-10

    Interferometric synthetic aperture radar presents a new technology for performing high-resolution topographic mapping. One of the factors critical to mapping accuracy is phase unwrapping. This paper presents a new algorithm that unwraps phase through fringe-line detection. The algorithm is effective in preventing error propagation, it preserves the image resolution, and, in the mean time, it produces negligible local errors. An edge-segment linking approach and a curve-fitting approach are investigated, and their performances are compared. Test results of the algorithm are shown with the actual interferometric SEASAT synthetic aperture radar images over large-relief terrain near Yellowstone National Park with a short baseline, and results are shown over relatively flat terrain in Death Valley of California with a long baseline. PMID:20862009

  17. Two-dimensional phase correction of synthetic-aperture-radar imagery

    SciTech Connect

    Ghiglia, D.C.; Mastin, G.A. )

    1989-10-15

    A two-dimensional synthetic-aperture-radar (SAR) phase-correction algorithm is described as a natural extension of a one-dimensional technique developed previously. It embodies some similarities of phase-gradient speckle imaging and incorporates improvements in phase estimation. Diffraction-limited performance has been obtained on actual SAR imagery regardless of scene content or phase-error structure. The algorithm is computationally efficient, robust, and easily implemented on a general-purpose computer or special-purpose hardware.

  18. Information extraction and transmission techniques for spaceborne synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Frost, V. S.; Yurovsky, L.; Watson, E.; Townsend, K.; Gardner, S.; Boberg, D.; Watson, J.; Minden, G. J.; Shanmugan, K. S.

    1984-01-01

    Information extraction and transmission techniques for synthetic aperture radar (SAR) imagery were investigated. Four interrelated problems were addressed. An optimal tonal SAR image classification algorithm was developed and evaluated. A data compression technique was developed for SAR imagery which is simple and provides a 5:1 compression with acceptable image quality. An optimal textural edge detector was developed. Several SAR image enhancement algorithms have been proposed. The effectiveness of each algorithm was compared quantitatively.

  19. The comparison between the synthetic aperture radar imageries and the surface truth of ocean waves

    NASA Technical Reports Server (NTRS)

    Hsiao, S. V.

    1978-01-01

    Ocean waves measured offshore of Marineland, Florida, by the synthetic aperture radar (SAR) are compared with the surface truth data. The Fourier transform of SAR imageries are taken and the corrections of the wave directions and wave lengths due to the relative velocities between SAR and waves are considered. Favorable comparisons are obtained for the peak frequencies, wave directions, and directional distributions. However, the one-dimensional SAR spectra are quite different from the surface truth wave height spectra.

  20. a Robust Change Detector for Multilook Polarimetric Synthetic Aperture Radar Data

    NASA Astrophysics Data System (ADS)

    Ghanbari; Akbari; Abkar; Sahebi; Liu

    2014-10-01

    In this paper, we propose a robust unsupervised change detection algorithm for multilook polarimetric synthetic aperture radar (PolSAR) data. The Hotelling-Lawley trace (HLT) statistic is used as a test statistic to measure the similarity of two covariance matrices. The generalized Kittler and Illingworth (K&I) minimum-error thresholding algorithm is then applied on the test statistic image to accurately discriminates changed and unchanged areas. The algorithm, tested on real PolSAR images, provides satisfactory results.

  1. Mapping Ocean Surface Topography with a Synthetic-Aperture Interferometry Radar

    NASA Technical Reports Server (NTRS)

    Fu, Lee-Lueng; Rodriguez, Ernesto

    2006-01-01

    We propose to apply the technique of synthetic aperture radar interferometry to the measurement of ocean surface topography at spatial resolution approaching 1 km. The measurement will have wide ranging applications in oceanography, hydrology. and marine geophysics. The oceanographic and related societal applications are briefly discussed in the paper. To meet the requirements for oceanographic applications, the instrument must be flown in an orbit with proper sampling of ocean tides.

  2. Attitude steering for space shuttle based synthetic aperture radars

    NASA Technical Reports Server (NTRS)

    Chang, C. Y.; Curlander, J. C.

    1992-01-01

    A technique is presented to steer the antenna beam to the zero-Doppler line for a spacecraft platform which operates in a non-zero roll attitude. The purposes of employing this attitude steering technique are reduction of the Doppler centroid error caused by the variation in target elevation; reduction of the Doppler centroid bound; and reduction of the Doppler drift. It is shown that a fixed attitude sequence can be easily accommodated in the radar command sequence to achieve nearly zero-Doppler steering. Implementation of this technique improves the image quality as well as simplifies the processor design.

  3. A Synthetic Aperture Radar (SAR) for commercial applications

    NASA Astrophysics Data System (ADS)

    Bullock, B. L.; Kozma, A.

    Studies leading to the design specifications and subsequent development of a SAR built solely for commercial applications are described. Background searches were made of potential users and their requirements and the corresponding technology. The system developed is called STAR 1 (for Sea-Ice and Terrain Assessment Radar); it is an X-band system installed in a light turboprop aircraft. The data are digitally processed in real time aboard the aircraft and the image is telemetered to a ground station for immediate use. The system is currently operational and has performed a number of tasks including support of arctic drilling and engineering, iceberg detection, arctic transportation, and terrain surveys.

  4. A Dual-polarized Microstrip Subarray Antenna for an Inflatable L-band Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Zawadzki, Mark; Huang, John

    1999-01-01

    Inflatable technology has been identified as a potential solution to the problem of achieving small mass, high packaging efficiency, and reliable deployment for future NASA spaceborne synthetic aperture radar (SAR) antennas. Presently, there exists a requirement for a dual-polarized L-band SAR antenna with an aperture size of 10m x 3m, a center frequency of 1.25GHz, a bandwidth of 80MHz, electronic beam scanning, and a mass of less than 100kg. The work presented below is part of the ongoing effort to develop such an inflatable antenna array.

  5. Estimation of Canopy Water Content in Konza Parry Grasslands Using Synthetic Aperture Radar Measurements During FIFE

    NASA Technical Reports Server (NTRS)

    Saatchi, Sasan S.; van Zyl, Jacob J.; Asrar, Ghassem

    1996-01-01

    This paper presents the development of an algorithm to retrieve the canopy water contents of natural grasslands and pasture from synthetic aperture radar (SAR) measurements. The development on this algorithm involves three interrelated steps: (1) calibration of SAR data for ground topographic variations, (2) development and validation of backscatter model for cross-polarized ratio. The polarimetric radar data acquired by the Jet Propulsion Laboratory AIRSAR system during the 1989 First International Satellite land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) used for this study. The SAR data have been calibrated and corrected for the topographical effects by using the digital elevation map of the study area.

  6. Global mapping strategies for a synthetic aperture radar system in orbit about Venus

    NASA Technical Reports Server (NTRS)

    Kerridge, S. J.

    1980-01-01

    An analysis of the global mapping of Venus using a synthetic aperture radar (SAR) is presented. The geometry of the side-looking radar, the narrow swath width, and the slow rotation of Venus combine to constrain the methods required to produce such a map within the primary mapping mission of 121.5 days. Parametric studies indicate that multiple strategies can satisfy the requirements of the mission with reasonable assumptions for the total recording capacity, the downlink data rate, and the operating time of the SAR on each revolution.

  7. Synthetic aperture radar target detection, feature extraction, and image formation techniques

    NASA Technical Reports Server (NTRS)

    Li, Jian

    1994-01-01

    This report presents new algorithms for target detection, feature extraction, and image formation with the synthetic aperture radar (SAR) technology. For target detection, we consider target detection with SAR and coherent subtraction. We also study how the image false alarm rates are related to the target template false alarm rates when target templates are used for target detection. For feature extraction from SAR images, we present a computationally efficient eigenstructure-based 2D-MODE algorithm for two-dimensional frequency estimation. For SAR image formation, we present a robust parametric data model for estimating high resolution range signatures of radar targets and for forming high resolution SAR images.

  8. Synthetic Aperture Radar: The NCCS Enables Search and Rescue

    NASA Astrophysics Data System (ADS)

    2002-07-01

    For as long as planes have gone down, dedicated men and women have used ever-improving technologies to aid their search for survivors. Nearly 2,000 general aviation crashes occur each year in U.S.-and many, like the Montana incident, occur without witnesses. On average, every day in the U.S. one airplane is reported missing. The Air Force Rescue Coordination Center (AFRCC) organizes search missions for about 100 aircraft each year. Some of these are not found before the searches called off, and are discovered only by chance long after the crash. In some cases, the crash site is never found. NASA Search and Rescue Mission is using NCCS rescues to develop tools for processing radar data that can help these effort

  9. Two antenna, two pass interferometric synthetic aperture radar

    DOEpatents

    Martinez, Ana; Doerry, Armin W.; Bickel, Douglas L.

    2005-06-28

    A multi-antenna, multi-pass IFSAR mode utilizing data driven alignment of multiple independent passes can combine the scaling accuracy of a two-antenna, one-pass IFSAR mode with the height-noise performance of a one-antenna, two-pass IFSAR mode. A two-antenna, two-pass IFSAR mode can accurately estimate the larger antenna baseline from the data itself and reduce height-noise, allowing for more accurate information about target ground position locations and heights. The two-antenna, two-pass IFSAR mode can use coarser IFSAR data to estimate the larger antenna baseline. Multi-pass IFSAR can be extended to more than two (2) passes, thereby allowing true three-dimensional radar imaging from stand-off aircraft and satellite platforms.

  10. X-SAR: The X-band synthetic aperture radar on board the Space Shuttle

    NASA Technical Reports Server (NTRS)

    Werner, Marian U.

    1993-01-01

    The X-band synthetic aperture radar (X-SAR) is the German/Italian contribution to the NASA/JPL Shuttle Radar Lab missions as part of the preparation for the Earth Observation System (EOS) program. The Shuttle Radar Lab is a combination of several radars: an L-band (1.2 GHz) and a C-band (5.3 GHz) multipolarization SAR known as SIR-C (Shuttle Imaging Radar); and an X-band (9.6 GHz) vertically polarized SAR which will be operated synchronously over the same target areas to deliver calibrated multifrequency and multipolarization SAR data at multiple incidence angles from space. A joint German/Italian project office at DARA (German Space Agency) is responsible for the management of the X-SAR project. The space hardware has been developed and manufactured under industrial contract by Dornier and Alenia Spazio. Besides supporting all the technical and scientific tasks, DLR, in cooperation with ASI (Agencia Spaziale Italiano) is responsible for mission operation, calibration, and high precision SAR processing. In addition, DLR developed an airborne X-band SAR to support the experimenters with campaigns to prepare for the missions. The main advantage of adding a shorter wavelength (3 cm) radar to the SIR-C radars is the X-band radar's weaker penetration into vegetation and soil and its high sensitivity to surface roughness and associated phenomena. The performance of each of the three radars is comparable with respect to radiometric and geometric resolution.

  11. X-SAR: The X-band synthetic aperture radar on board the Space Shuttle

    NASA Astrophysics Data System (ADS)

    Werner, Marian U.

    1993-05-01

    The X-band synthetic aperture radar (X-SAR) is the German/Italian contribution to the NASA/JPL Shuttle Radar Lab missions as part of the preparation for the Earth Observation System (EOS) program. The Shuttle Radar Lab is a combination of several radars: an L-band (1.2 GHz) and a C-band (5.3 GHz) multipolarization SAR known as SIR-C (Shuttle Imaging Radar); and an X-band (9.6 GHz) vertically polarized SAR which will be operated synchronously over the same target areas to deliver calibrated multifrequency and multipolarization SAR data at multiple incidence angles from space. A joint German/Italian project office at DARA (German Space Agency) is responsible for the management of the X-SAR project. The space hardware has been developed and manufactured under industrial contract by Dornier and Alenia Spazio. Besides supporting all the technical and scientific tasks, DLR, in cooperation with ASI (Agencia Spaziale Italiano) is responsible for mission operation, calibration, and high precision SAR processing. In addition, DLR developed an airborne X-band SAR to support the experimenters with campaigns to prepare for the missions. The main advantage of adding a shorter wavelength (3 cm) radar to the SIR-C radars is the X-band radar's weaker penetration into vegetation and soil and its high sensitivity to surface roughness and associated phenomena. The performance of each of the three radars is comparable with respect to radiometric and geometric resolution.

  12. A Multi-Frequency Inverse Synthetic Aperture Radar (ISAR) Instrument to Explore the Internal Structure of Small Planetary Bodies

    NASA Astrophysics Data System (ADS)

    Deshpande, M.

    2012-10-01

    A step frequency Inverse Synthetic Aperture Radar (ISAR) instrument operating over a wide low-band frequencies is described to perform reflection/transmission tomography for imaging the internal structure of asteroids and small planetary bodies.

  13. Evaluation of synthetic aperture radar for oil-spill response. Final report, June 1992-September 1993

    SciTech Connect

    Hover, G.L.; Mastin, G.A.; Axline, R.M.; Bradley, J.D.

    1993-10-01

    This report provides a detailed evaluation of synthetic aperture radar (SAR) as a potential technology improvement over the Coast Guard's existing side-looking airborne radar (SLAR) for oil-spill surveillance applications. The U.S. Coast Guard Research and Development Center (RD Center), Environmental Safety Branch, sponsored a joint experiment including the U.S. Coast Guard, Sandia National Laboratories, and the National Oceanographic and Atmospheric Administration (NOAA), Hazardous Materials Division. Radar imaging missions were flown on six days over the coastal waters off Santa Barbara, CA, where there are constant natural seeps of oil. Both the Coast Guard SLAR and the Sandia National Laboratories SAR were employed to acquire simultaneous images of oil slicks and other natural sea surface features that impact oil-spill interpretation. Surface truth and other environmental data were also recorded during the experiment. The experiment data were processed at Sandia National Laboratories and delivered to the RD Center on a PC-based computer workstation for analysis by experiment participants. Synthetic aperture radar, Side looking airborne radar, Oil slicks.

  14. Estimates of surface roughness derived from synthetic aperture radar (SAR) data

    NASA Technical Reports Server (NTRS)

    Evans, Diane L.; Farr, Tom G.; Van Zyl, Jakob J.

    1992-01-01

    Radar remote sensing data provide a unique perspective of the earth's crust and the processes that have influenced its evolution. Physically based models are required, however, to relate the geophysical quantities being measured by the radar sensor to useful geologic information. In this study, synthetic aperture radar (SAR) data over the Cima volcanic field in the Mojave Desert of California are quantitatively connected with microtopography through inversion of a radar backscatter model. Changes in surface roughness inferred from the derived microtopography are modeled and found to be consistent with aeolian mantling as surfaces age. Estimated rates of aeolian deposition for the Cima area are compared to the Lunar Crater volcanic field in Nevada. Rates of deposition appear to be higher at Cima volcanic field, most likely because of its proximity to Soda Lake, the main source of the aeolian material.

  15. A model for forming airborne synthetic aperture radar images of underground targets

    SciTech Connect

    Doerry, A.W.

    1994-01-01

    Synthetic Aperture Radar (SAR) from an airborne platform has been proposed for imaging targets beneath the earth`s surface. The propagation of the radar`s energy within the ground, however, is much different than in the earth`s atmosphere. The result is signal refraction, echo delay, propagation losses, dispersion, and volumetric scattering. These all combine to make SAR image formation from an airborne platform much more challenging than a surface imaging counterpart. This report treats the ground as a lossy dispersive half-space, and presents a model for the radar echo based on measurable parameters. The model is then used to explore various imaging schemes, and image properties. Dynamic range is discussed, as is the impact of loss on dynamic range. Modified window functions are proposed to mitigate effects of sidelobes of shallow targets overwhelming deeper targets.

  16. Moving target detection in foliage using along track monopulse synthetic aperture radar imaging.

    PubMed

    Soumekh, M

    1997-01-01

    This paper presents a method for detecting moving targets embedded in foliage from the monostatic and bistatic synthetic aperture radar (SAR) data obtained via two airborne radars. The two radars, which are mounted on the same aircraft, have different coordinates in the along track (cross-range) domain. However, unlike the interferometric SAR systems used for topographic mapping, the two radars possess a common range and altitude (i.e., slant range). The resultant monopulse SAR images are used to construct difference and interferometric images for moving target detection. It is shown that the signatures of the stationary targets are weakened in these images. Methods for estimating a moving target's motion parameters are discussed. Results for an ultrawideband UHF SAR system are presented. PMID:18283004

  17. Method and apparatus for contour mapping using synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Goldstein, R. M.; Caro, E. R.; Wu, C. (Inventor)

    1985-01-01

    By using two SAR antennas spaced a known distance, B, and oriented at substantially the same look angle to illuminate the same target area, pixel data from the two antennas may be compared in phase to determine a difference delta phi from which a slant angle theta is determined for each pixel point from an equation Delta phi = (2 pi B/lambda)sin(theta - alpha), where lambda is the radar wavelength and alpha is the roll angle of the aircraft. The height, h, of each pixel point from the aircraft is determined from the equation h = R cos theta, and from the known altitude, a, of the aircraft above sea level, the altitude (elevation), a', of each point is determined from the difference a - h. This elevation data may be displayed with the SAR image by, for example, quantizing the elevation at increments of 100 feet starting at sea level, and color coding pixels of the same quantized elevation. The distance, d, of each pixel from the ground track of the aircraft used for the display may be determined more accurately from the equation d = R sin theta.

  18. Operational Use of Civil Space-Based Synthetic Aperture Radar (SAR)

    NASA Technical Reports Server (NTRS)

    Montgomery, Donald R. (Editor)

    1996-01-01

    Synthetic Aperture Radar (SAR) is a remote-sensing technology which uses the motion of the aircraft or spacecraft carrying the radar to synthesize an antenna aperture larger than the physical antenna to yield a high-spatial resolution imaging capability. SAR systems can thus obtain high-spatial resolution geophysical measurements of the Earth over wide surface areas, under all-weather, day/night conditions. This report was prepared to document the results of a six-month study by an Ad Hoc Interagency Working Group on the Operational Use of Civil (i.e., non-military) Space-based Synthetic Aperture Radar (SAR). The Assistant Administrator of NOAA for Satellite and Information Services convened this working group and chaired three meetings of the group over a six-month period. This action was taken in response to a request by the Associate Administrator of NASA for Mission to Planet Earth for an assessment of operational applications of SAR to be accomplished in parallel with a separate study requested of the Committee on Earth Studies of the Space Studies Board of the National Research Council on the scientific results of SAR research missions. The representatives of participating agencies are listed following the Preface. There was no formal charter for the working group or long term plans for future meetings. However, the working group may be reconstituted in the future as a coordination body for multiagency use of operational SAR systems.

  19. Conceptual performance of a satellite borne, wide swath synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Tomiyasu, K.

    1981-01-01

    A satellite borne synthetic aperture radar can image a wide swath in the order of 700 km with one-look 100-m resolution. If the design meets the ambiguity constraints at the far edge of the swath, the maximum swath width is independent of both radar wavelength and shape of the physical antenna aperture. The antenna pattern can be a pencil beam scanned in the elevation plane, or a fan beam formed by a long antenna. The scanning pencil beam antenna may be a phased array or multiple-feed reflector which may be more practical than a long antenna to image a wide swath. Design performance trade computations are presented involving resolution, swath width, antenna area, average transmitter power and digital data rate.

  20. Interferometric synthetic aperture radar and the Data Collection System Digital Terrain Elevation Demonstration

    NASA Astrophysics Data System (ADS)

    Heidelbach, Robert; Bolus, R.; Chadwick, J.

    1994-08-01

    Digital Terrain Elevations (DTE) that can be rapidly generated, and that have better fidelity and accuracy than Digital Terrain Elevation Data (DTED) Levels 1 or 2, would be extremely beneficial to Department of Defense (DOD) military operations, civil works programs, and various commercial applications. As a result, the Advanced Research Projects Agency (ARPA), along with the U.S. Army Topographic Engineering Center (TEC), are developing an Interferometric Synthetic Aperture Radar (IFSAR) elevation mapping capability. This system, the Interferometric Synthetic Aperture Radar for Digital Radar Elevations (IFSARE), is capable of collecting and providing data in all weather (reasonable), in day or night scenarios, and where obscurants are present. The IFSARE, which is currently undergoing Integration and Test, will allow for rapid on-line automatic processing of the collected digital radar data into DTE and high quality imagery. The prime contractor is the Environmental Research Institute of Michigan (ERIM). This paper addresses the proof of concept for civil works applications by analyzing a data set taken by the Wright Labs/ERIM Data Collection System (DCS). The objective was to demonstrate the capability of an IFSAR system to provide high fidelity, fine resolution DTE that can be employed in hydraulic models of the Mississippi River watershed. The demonstration was sponsored by ARPA and TEC.

  1. Feasibility study of synthetic aperture infrared laser radar techniques for imaging of static and moving objects.

    PubMed

    Yoshikado, S; Aruga, T

    1998-08-20

    Techniques for two types of 10-mum band synthetic aperture infrared laser radar using a hypothetical reference point target (RPT) are presented. One is for imaging static objects with a single two-dimensional scanning aperture. Through the simple manipulation of a reference wave phase, a desired image can be obtained merely by the two-dimensional Fourier transformation of the correlator output between the intermediate frequency signals of the reference and object waves. The other, with a one-dimensional aperture array, is for moving objects that pass across the array direction without attitude change. We performed imaging by using a two-dimensional RPT correlation method. We demonstrate the capability of these methods for imaging and evaluate the necessary conditions for signal-to-noise ratio and random phase errors in signal reception through numerical simulations in terms of feasibility. PMID:18286049

  2. Phenomenology of low probability of intercept synthetic aperture radar via Frank codes

    NASA Astrophysics Data System (ADS)

    Garren, David A.; Pace, Phillip E.; Romero, Ric A.

    2014-06-01

    This paper investigates techniques for using low probability of intercept (LPI) modulation techniques for forming synthetic aperture radar (SAR) imagery. This analysis considers a specific waveform type based upon Frank codes in providing for the LPI capability via phase shift keying (PSK) modulation. A correlation receiver that is matched to the transmitted waveform is utilized to generate a set of SAR data. This analysis demonstrates the ability to form SAR images based upon simulated radar measurements collected by a notional radar sensor that has ability to transmit and receive Frank-coded waveforms and to form SAR images based upon the results of a correlation receiver. Spotlight-mode SAR images are generated using the Frank-coded waveforms and their properties are analyzed and discussed.

  3. Shuttle synthetic aperture radar implementation study, volume 1. [flight instrument and ground data processor system for collecting raw imaged radar data

    NASA Technical Reports Server (NTRS)

    Mehlis, J. G.

    1976-01-01

    Results of an implementation study for a synthetic aperture radar for the space shuttle orbiter are described. The overall effort was directed toward the determination of the feasibility and usefulness of a multifrequency, multipolarization imaging radar for the shuttle orbiter. The radar is intended for earth resource monitoring as well as oceanographic and marine studies.

  4. Interferometric synthetic aperture radar (InSAR)—its past, present and future

    USGS Publications Warehouse

    Lu, Zhong; Kwoun, Oh-Ig; Rykhus, R.P.

    2007-01-01

    Very simply, interferometric synthetic aperture radar (InSAR) involves the use of two or more synthetic aperture radar (SAR) images of the same area to extract landscape topography and its deformation patterns. A SAR system transmits electromagnetic waves at a wavelength that can range from a few millimeters to tens of centimeters and therefore can operate during day and night under all-weather conditions. Using SAR processing technique (Curlander and McDonough, 1991), both the intensity and phase of the reflected (or backscattered) radar signal of each ground resolution element (a few meters to tens of meters) can be calculated in the form of a complex-valued SAR image that represents the reflectivity of the ground surface. The amplitude or intensity of the SAR image is determined primarily by terrain slope, surface roughness, and dielectric constants, whereas the phase of the SAR image is determined primarily by the distance between the satellite antenna and the ground targets. InSAR imaging utilizes the interaction of electromagnetic waves, referred to as interference, to measure precise distances between the satellite antenna and ground resolution elements to derive landscape topography and its subtle change in elevation.

  5. Seafloor Topography Modelling in Northern Adriatic Sea Using Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Filipponi, Federico; Taramelli, Andrea; Zucca, Francesco

    2013-03-01

    Underwater bottom topography may be visible on Synthetic Aperture Radar (SAR) images through the radar signature of ocean surface currents. Using SAR images and a limited number of echo soundings it is possible to constructs accurate depth maps, greatly reducing the costs of bathymetric surveying. Based on shallow water bathymetry synthetic aperture radar (SAR) imaging mechanism and the microwave scattering imaging model for oceanic surface features, we are working to develop a new method for shallow water depth retrieval from space-borne SAR images. Shallow waters in the northern part of Adriatic sea may represent favorable depth condition for underwater bottom topography estimation testing over large area, using SAR imagery, although such area does not show strong tidal currents. Strategy for northern Adriatic Sea seafloor modeling is presented, using the Bathymetry Assessment System (BAS). Evaluation is conducted using SAR imagery from different satellite platforms and in multitemporal framework, in cooperation with echo soundings from bathymetric surveying. Two monitoring sites supply in situ data, such as water level, current flow, wind velocity and direction. Physical conditions evaluation in the study site supports selection of the best SAR images for depth estimation. Multisensor approach will give the possibility to evaluate differences in bottom topography estimation from sensor with different characteristics.

  6. Indoor imagery with a 3D through-wall synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Svigny, Pascale; DiFilippo, David J.; Laneve, Tony; Fournier, Jonathan

    2012-06-01

    Through-wall radar imaging is an emerging technology with great interest to military and police forces operating in an urban environment. A through-wall imaging radar can potentially provide interior room layouts as well as detection and localization of targets of interest within a building. In this paper, we present our through-wall radar system mounted on the side of a vehicle and driven along a path in front of a building of interest. The vehicle is equipped with a LIDAR (Light Detection and Ranging) and motion sensors that provide auxiliary information. The radar uses an ultra wideband frequency-modulated continuous wave (FMCW) waveform to obtain high range resolution. Our system is composed of a vertical linear receive array to discriminate targets in elevation, and two transmit elements operated in a slow multiple-input multiple output (MIMO) configuration to increase the achievable elevation resolution. High resolution in the along-track direction is obtained through synthetic aperture radar (SAR) techniques. We present experimental results that demonstrate the 3-D capability of the radar. We further demonstrate target detection behind challenging walls, and imagery of internal wall features. Finally, we discuss future work.

  7. Correction of motion measurement errors beyond the range resolution of a synthetic aperture radar

    SciTech Connect

    Doerry, Armin W.; Heard, Freddie E.; Cordaro, J. Thomas

    2008-06-24

    Motion measurement errors that extend beyond the range resolution of a synthetic aperture radar (SAR) can be corrected by effectively decreasing the range resolution of the SAR in order to permit measurement of the error. Range profiles can be compared across the slow-time dimension of the input data in order to estimate the error. Once the error has been determined, appropriate frequency and phase correction can be applied to the uncompressed input data, after which range and azimuth compression can be performed to produce a desired SAR image.

  8. Two-dimensional phase correction of synthetic-aperture-radar imagery.

    PubMed

    Ghiglia, D C; Mastin, G A

    1989-10-15

    A two-dimensional synthetic-aperture-radar (SAR) phase-correction algorithm is described as a natural extension of a one-dimensional technique developed previously. It embodies some similarities of phase-gradient speckle imaging and incorporates improvements in phase estimation. Diffraction-limited performance has been obtained on actual SAR imagery regardless of scene content or phase-error structure. The algorithm is computationally efficient, robust, and easily implemented on a general-purpose computer or special-purpose hardware. PMID:19753069

  9. Efficient one-stationary bistatic synthetic aperture radar raw data generation based on Fourier analysis

    NASA Astrophysics Data System (ADS)

    Huang, Yulin; Wu, Junjie; Li, Zhongyu; Yang, Haiguang; Yang, Jianyu

    2016-01-01

    Raw data generation for synthetic aperture radar (SAR) is very powerful for designing systems and testing imaging algorithms. In this paper, a raw data generation method based on Fourier analysis for one-stationary bistatic SAR is presented. In this mode, two-dimensional (2-D) spatial variation is the major problem faced by the fast Fourier transform-based raw data generation. To deal with this problem, a 2-D linearization followed by a 2-D frequency transformation is employed in this method. This frequency transformation can reflect the 2-D spatial variation. Residual phase compensation is also discussed. Numerical simulation verifies the method.

  10. A digital system to produce imagery from SAR data. [Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Wu, C.

    1976-01-01

    This paper describes a digital processing algorithm and its associated system design for producing images from Synthetic Aperture Radar (SAR) data. The proposed system uses the Fast Fourier Transform (FFT) approach to perform the two-dimensional correlation process. The range migration problem, which is often a major obstacle to efficient processing, can be alleviated by approximating the locus of echoes from a point target by several linear segments. SAR data corresponding to each segment is correlated separately, and the results are coherently summed to produce full-resolution images. This processing approach exhibits greatly improved computation efficiency relative to conventional digital processing methods.

  11. Generation of topographic terrain models utilizing synthetic aperture radar and surface level data

    NASA Technical Reports Server (NTRS)

    Imhoff, Marc L. (Inventor)

    1991-01-01

    Topographical terrain models are generated by digitally delineating the boundary of the region under investigation from the data obtained from an airborne synthetic aperture radar image and surface elevation data concurrently acquired either from an airborne instrument or at ground level. A set of coregistered boundary maps thus generated are then digitally combined in three dimensional space with the acquired surface elevation data by means of image processing software stored in a digital computer. The method is particularly applicable for generating terrain models of flooded regions covered entirely or in part by foliage.

  12. A study of image quality for radar image processing. [synthetic aperture radar imagery

    NASA Technical Reports Server (NTRS)

    King, R. W.; Kaupp, V. H.; Waite, W. P.; Macdonald, H. C.

    1982-01-01

    Methods developed for image quality metrics are reviewed with focus on basic interpretation or recognition elements including: tone or color; shape; pattern; size; shadow; texture; site; association or context; and resolution. Seven metrics are believed to show promise as a way of characterizing the quality of an image: (1) the dynamic range of intensities in the displayed image; (2) the system signal-to-noise ratio; (3) the system spatial bandwidth or bandpass; (4) the system resolution or acutance; (5) the normalized-mean-square-error as a measure of geometric fidelity; (6) the perceptual mean square error; and (7) the radar threshold quality factor. Selective levels of degradation are being applied to simulated synthetic radar images to test the validity of these metrics.

  13. Multibeam single frequency synthetic aperture radar processor for imaging separate range swaths

    NASA Technical Reports Server (NTRS)

    Jain, A. (Inventor)

    1982-01-01

    A single-frequency multibeam synthetic aperture radar for large swath imaging is disclosed. Each beam illuminates a separate ""footprint'' (i.e., range and azimuth interval). The distinct azimuth intervals for the separate beams produce a distinct Doppler frequency spectrum for each beam. After range correlation of raw data, an optical processor develops image data for the different beams by spatially separating the beams to place each beam of different Doppler frequency spectrum in a different location in the frequency plane as well as the imaging plane of the optical processor. Selection of a beam for imaging may be made in the frequency plane by adjusting the position of an aperture, or in the image plane by adjusting the position of a slit. The raw data may also be processed in digital form in an analogous manner.

  14. Reduction and coding of synthetic aperture radar data with Fourier transforms

    NASA Technical Reports Server (NTRS)

    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.

  15. Concepts and Technologies for Synthetic Aperture Radar from MEO and Geosynchronous orbits

    NASA Technical Reports Server (NTRS)

    Edelstein, Wendy N.; Madsen, Soren; Moussessian, Alina; Chen, Curtis

    2004-01-01

    The area accessible from a spaceborne imaging radar, e.g. a synthetic aperture radar (SAR), generally increases with the elevation of the satellite while the map coverage rate is a more complicated function of platform velocity and beam agility. The coverage of a low Earth orbit (LEO) satellite is basically given by the fast ground velocity times the relatively narrow swath width. The instantaneously accessible area will be limited to some hundreds of kilometers away from the sub-satellite point. In the other extreme, the sub-satellite point of a SAR in geosynchronous orbit will move relatively slowly, while the area which can be accessed at any given time is very large, reaching thousands of kilometers from the subsatellite point. To effective1y use the accessibility provided by a high vantage point, very large antennas with electronically steered beams are required.

  16. Real-time optical processor for synthetic aperture radar image formation

    SciTech Connect

    Stalker, K.T.; Molley, P.A.; Dickey, F.M.

    1987-01-01

    An acousto-optic processor which forms synthetic aperture radar images in real-time is described. It employs a space and time integrating architecture to perform the required two dimensional matched filtering operation as a sequence of one dimensional processes. The matched filtering in range is performed on each radar return pulse using the acousto-optic device. The azimuthal matched filtering is performed using a fixed reference mask and a charge-coupled device operating in the time delay and integrate mode. This fixed mask architecture has been modified to include a background subtraction capability to reduce the effects of unwanted bias terms on image quality. The effectiveness of this technique will be analyzed for two different time bandwidth product cases. SAR imagery formed using the real-time optical processor is also presented.

  17. A sea surface height estimator using synthetic aperture radar complex imagery

    NASA Technical Reports Server (NTRS)

    Harger, R. O.

    1983-01-01

    A method is developed for estimating the sea surface height using the complex imagery from synthetic aperture radar (SAR). Algorithms are developed for the envelope and phase demodulation, regression, and filtering of the SAR complex imagery and are applied to simulated and actual satellite radar SEASAT-SAR data. A simulation of a simplified stationary scene is utilized in order to establish tentative sufficient conditions on large-scale SAR and sampling parameters for the accurate estimation of the scale structure's height. It is shown that the algorithm accurately estimated a long wavelength low-amplitude sea height structure present in the SEASAT-SAR data, which was determined to be consistent with observations.

  18. Speckle statistics in synthetic aperture radar (SAR) imagery with correlated looks

    NASA Astrophysics Data System (ADS)

    April, G. V.; Harvey, E. R.

    1988-01-01

    The high resolution in synthetic aperture radar (SAR) systems is reduced by the speckle appearing in the images. This speckle noise is generated by the coherent processing of radar signals and exists in all types of coherent imaging systems. The statistical properties of speckle noise in a four-look Seasat SAR image are studied to show evidence of correlation between underlying looks resulting in correlated values for adjacent pixels in the final image. Concentrating on homogeneous areas of the image, experimental determination of the SNR and of the probability density of the recorded intensity is performed. It is shown that the intensity fluctuations due to speckle noise in homogeneous areas are not gamma distributed. A model incorporating the empirical correlation coefficient is extracted from experimental data.

  19. Tradeoffs among several synthetic aperture radar image quality parameters - Results of a user survey study

    NASA Technical Reports Server (NTRS)

    Li, F. K.; Bryan, M. L.

    1983-01-01

    The imagery obtained with the aid of synthetic aperture radars (SAR) has been applied to several remote sensing disciplines such as geologic feature mapping, oceanic phenomena studies, and land use and urban morphology studies. The successful SAR experiment on Seasat and the Shuttle demonstrated the feasibility of global radar mapping at relatively high resolution from a spaceborn platform. The present investigation is concerned with the requirements of and the tradeoffs among several SAR image quality parameters. The results are presented from a survey study concerning the interpretability of a set of SAR images. The data used to generate these images were obtained by the Seasat SAR experiments. Attention is given to image scenes and the simulation experiment, image interpretation survey results, multiple-looks, the number of looks vs resolution, and number of bits vs resolution.

  20. Real-time implementation of frequency-modulated continuous-wave synthetic aperture radar imaging using field programmable gate array

    NASA Astrophysics Data System (ADS)

    Quan, Yinghui; Li, Yachao; Hu, Guibin; Xing, Mengdao

    2015-06-01

    A new miniature linear frequency-modulated continuous-wave radar which mounted on an unmanned aerial vehicle is presented. It allows the accomplishment of high resolution synthetic aperture radar imaging in real-time. Only a Kintex-7 field programmable gate array from Xilinx is utilized for whole signal processing of sophisticated radar imaging algorithms. The proposed hardware architecture achieves remarkable improvement in integration, power consumption, volume, and computing performance over its predecessor designs. The realized design is verified by flight campaigns.

  1. Factors governing selection of operating frequency for subsurface- imaging synthetic-aperture radar

    SciTech Connect

    Brock, B.C.; Patitz, W.E.

    1993-12-31

    A subsurface-imaging synthetic-aperture radar (SISAR) has potential for application in areas as diverse as non-proliferation programs for nuclear weapons to environmental monitoring. However, subsurface imaging is complicated by propagation loss in the soil and surface-clutter response. Both the loss and surface-clutter response depend on the operating frequency. This paper examines several factors which provide a basis for determining optimum frequencies and frequency ranges which will allow synthetic-aperture imaging of buried targets. No distinction can be made between objects at different heights when viewed with a conventional imaging radar (which uses a one-dimensional synthetic aperture), and the return from a buried object must compete with the return from the surface clutter. Thus, the signal-to-clutter ratio is an appropriate measure of performance for a SISAR. A parameter-based modeling approach is used to model the complex dielectric constant of the soil from measured data obtained from the literature. Theoretical random-surface scattering models, based on statistical solutions to Maxwell`s equations, are used to model the clutter. These models are combined to estimate the signal-to-clutter ratio for canonical targets buried in several soil configurations. Results indicate that the HF spectrum (3--30), although it could be used to detect certain targets under some conditions, has limited practical value for use with SISAR, while the upper VIHF through UHF spectrum ({approximately}100 MHz - 1 GHz) shows the most promise for a general purpose SISAR system. Recommendations are included for additional research.

  2. Swell dissipation from 10 years of Envisat advanced synthetic aperture radar in wave mode

    NASA Astrophysics Data System (ADS)

    Stopa, Justin E.; Ardhuin, Fabrice; Husson, Romain; Jiang, Haoyu; Chapron, Bertrand; Collard, Fabrice

    2016-04-01

    Swells are found in all oceans and strongly influence the wave climate and air-sea processes. The poorly known swell dissipation is the largest source of error in wave forecasts and hindcasts. We use synthetic aperture radar data to identify swell sources and trajectories, allowing a statistically significant estimation of swell dissipation. We mined the entire Envisat mission 2003-2012 to find suitable storms with swells (13 < T < 18 s) that are observed several times along their propagation. This database of swell events provides a comprehensive view of swell extending previous efforts. The analysis reveals that swell dissipation weakly correlates with the wave steepness, wind speed, orbital wave velocity, and the relative direction of wind and waves. Although several negative dissipation rates are found, there are uncertainties in the synthetic aperture radar-derived swell heights and dissipation rates. An acceptable range of the swell dissipation rate is -0.1 to 6 × 10-7 m-1 with a median of 1 × 10-7 m-1.

  3. Change Detection in Synthetic Aperture Radar Images Based on Deep Neural Networks.

    PubMed

    Gong, Maoguo; Zhao, Jiaojiao; Liu, Jia; Miao, Qiguang; Jiao, Licheng

    2016-01-01

    This paper presents a novel change detection approach for synthetic aperture radar images based on deep learning. The approach accomplishes the detection of the changed and unchanged areas by designing a deep neural network. The main guideline is to produce a change detection map directly from two images with the trained deep neural network. The method can omit the process of generating a difference image (DI) that shows difference degrees between multitemporal synthetic aperture radar images. Thus, it can avoid the effect of the DI on the change detection results. The learning algorithm for deep architectures includes unsupervised feature learning and supervised fine-tuning to complete classification. The unsupervised feature learning aims at learning the representation of the relationships between the two images. In addition, the supervised fine-tuning aims at learning the concepts of the changed and unchanged pixels. Experiments on real data sets and theoretical analysis indicate the advantages, feasibility, and potential of the proposed method. Moreover, based on the results achieved by various traditional algorithms, respectively, deep learning can further improve the detection performance. PMID:26068879

  4. Anisotropic diffusion for speckle filtering of polarimetric synthetic aperture radar imagery

    NASA Astrophysics Data System (ADS)

    Sun, Sheng; Tian, Jinwen; Liu, Zhusong; Cai, Nian

    2013-01-01

    The mission of speckle filtering is more intricate for a polarimetric synthetic aperture radar (SAR) system than for a single polarization SAR system. A new speckle filter that employs nonlinear anisotropic diffusion is proposed. The speckle filtering principles in a polarimetric SAR system are thoroughly investigated. Our study demonstrates that preservation of polarimetric properties and reduction of speckle level are very important clauses among those principles. Anisotropic diffusion outperforms window-based filters because it utilizes a diffusion tensor that can bias the direction of diffusion toward the orientation of interesting features. The procedure of diffusion is iterative, so it can lead to a gradual alleviation of speckle noise. The parameters for diffusion are flexible and adjustable, thus the filtering results are controllable according to the requirements of specific applications. Multidimensional and vector-valued model is combined with local statistics based on polarimetric SAR configuration. The experimental results on electromagnetics institute synthetic aperture radar (EMISAR) datasets show that the proposed filter has good performance in speckle reduction and preservation of polarimetric properties.

  5. Onboard Data Compression of Synthetic Aperture Radar Data: Status and Prospects

    NASA Technical Reports Server (NTRS)

    Klimesh, Matthew A.; Moision, Bruce

    2008-01-01

    Synthetic aperture radar (SAR) instruments on spacecraft are capable of producing huge quantities of data. Onboard lossy data compression is commonly used to reduce the burden on the communication link. In this paper an overview is given of various SAR data compression techniques, along with an assessment of how much improvement is possible (and practical) and how to approach the problem of obtaining it. Synthetic aperture radar (SAR) instruments on spacecraft are capable of acquiring huge quantities of data. As a result, the available downlink rate and onboard storage capacity can be limiting factors in mission design for spacecraft with SAR instruments. This is true both for Earth-orbiting missions and missions to more distant targets such as Venus, Titan, and Europa. (Of course for missions beyond Earth orbit downlink rates are much lower and thus potentially much more limiting.) Typically spacecraft with SAR instruments use some form of data compression in order to reduce the storage size and/or downlink rate necessary to accommodate the SAR data. Our aim here is to give an overview of SAR data compression strategies that have been considered, and to assess the prospects for additional improvements.

  6. Multi-frequency synthetic-aperture imaging with a lightweight ground penetrating radar system

    NASA Astrophysics Data System (ADS)

    Koppenjan, Steven K.; Allen, Curt M.; Gardner, Duane; Wong, Howard R.; Lee, Hua; Lockwood, Stephanie J.

    2000-03-01

    The detection of buried objects, particularly hazardous waste containers and unexploded ordnance (UXO), has gained significant interest in the Unites States in the late 1990s. The desire to remediate the thousands of sites worldwide has become an increasing concern and the application of radar to this problem has received renewed attention. The US Department of Energy's Special Technologies Laboratory (STL), operated by Bechtel Nevada, has developed several frequency-modulated, continuous-wave (FM-CW) ground penetrating radar (GPR) units. To meet technical requirements for higher-resolution data, STL and the University of California, Santa Barbara (UCSB) is investigating advanced GPR hardware, signal processing, and synthetic-aperture imaging with the development of an innovative system. The goal is to design and fabricate a lightweight, battery-operated unit that does not require surface contact, can be operated by a novice user, and can achieve improved resolution. The latter is accomplished by using synthetic-aperture imaging, which forms the subsurface images by fully utilizing the data sequences collectively along a scan path. We also present the backward propagation algorithm as the basic structure of the multiple-frequency tomographic imaging technique, and the conventional fast Fourier transform (FFT) method which can be described as a degenerated case of the model where the computation procedure is approximated under the narrow-beam assumption.

  7. Bistatic synthetic aperture radar imaging using ultraNarrowband continuous waveforms.

    PubMed

    Wang, Ling; Yazici, Birsen

    2012-08-01

    We consider synthetic aperture radar (SAR) imaging using ultra-narrowband continuous waveforms (CW). Due to the high Doppler resolution of CW signals, we refer to this imaging modality as Doppler Synthetic Aperture Radar (DSAR). We present a novel model and an image formation method for the bistatic DSAR for arbitrary imaging geometries. Our bistatic DSAR model is formed by correlating the translated version of the received signal with a scaled or frequencyshifted version of the transmitted CW signal over a finite time window. High frequency analysis of the resulting model shows that the correlated signal is the projections of the scene reflectivity onto the bistatic iso-Doppler curves. We next use microlocal techniques to develop a filtered-backprojection (FBP) type image reconstruction method. The FBP inversion results in backprojection of the correlated signal onto the bistatic iso- Doppler curves as opposed to the bistatic iso-range curves, performed in the traditional wideband SAR imaging. We show that our method takes advantage of the velocity, as well as the acceleration of the antennas in certain directions to form a high resolution SAR image. Our bistatic DSAR imaging method is applicable for arbitrary flight trajectories, nonflat topography, and can accommodate system related parameters. We present resolution analysis and extensive numerical experiments to demonstrate the performance of our imaging method. PMID:22481825

  8. Footprints of storms on the sea: A view from spaceborne synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Atlas, David

    1994-01-01

    Synthetic aperture radar (SAR) on board Seasat observed images of stormlike echoes on the sea in 1978. The core of these images is usually an echo-free hole which is attributed to the damping of the short (30-cm) radar detectable gravity waves by the intense rain in the storm core. Although 'the beating down of waves by rain' is consistent with observations by seafarers and with the first scientific explanation of the phenomenon by Reynolds (1875), neither theory nor experiment has provided definitive support. One experiment appears to provide the key; it shows that the kenetic energy of the rain produces sufficient turbulence in a thin fresh water layer to damp 30-cm waves in 10-20 s, thus producing the echo-free hole. A sequence of positive feedbacks then serves to damp the longer waves. The angular dependence of the sea surface echo cross sections seen by Seasat SAR outside the echo-free hole indicates winds diverging from the downdraft induced by the intense rain core. The wind-generated waves and associated echoes extend out to a sharply defined gust front. The sea surface footprint thus mimics the features of a storm microburst. The variations in surface radar cross section due to a combination of rain and wind effects impacts spaceborne measurements of surface winds by scatterometry and rainfall measurements by radar. Portions of this synthesis remain speculative but serve as hypotheses for further research.

  9. An algorithm for operational flood mapping from Synthetic Aperture Radar (SAR) data using fuzzy logic

    NASA Astrophysics Data System (ADS)

    Pulvirenti, L.; Pierdicca, N.; Chini, M.; Guerriero, L.

    2011-02-01

    An algorithm developed to map flooded areas from synthetic aperture radar imagery is presented in this paper. It is conceived to be inserted in the operational flood management system of the Italian Civil Protection and can be used in an almost automatic mode or in an interactive mode, depending on the user's needs. The approach is based on the fuzzy logic that is used to integrate theoretical knowledge about the radar return from inundated areas taken into account by means of three electromagnetic scattering models, with simple hydraulic considerations and contextual information. This integration aims at allowing a user to cope with situations, such as the presence of vegetation in the flooded area, in which inundation mapping from satellite radars represents a difficult task. The algorithm is designed to work with radar data at L, C, and X frequency bands and employs also ancillary data, such as a land cover map and a digital elevation model. The flood mapping procedure is tested on an inundation that occurred in Albania on January 2010 using COSMO-SkyMed very high resolution X-band SAR data.

  10. Experimental evaluation of cursors for B-2 Synthetic Aperture Radar (SAR) application

    NASA Astrophysics Data System (ADS)

    Irvin, Janet G.; Doyal, Jeffrey A.; Sharp, Earl D.; Lasalvia, James M.

    1993-12-01

    The purpose of the current study was to evaluate the current and two alternative cursors for B-2 Synthetic Aperture Radar (SAR) imagery application and to recommend an alternative design. This study was conducted in response to problems crewmembers are experiencing with the current cursor on the B-2 SAR display. In particular, the design of the current radar cursor (i.e., the width of the cursor bars) makes it difficult to accomplish fine cursor positioning (i.e., accurate placement of the cursor within the desired one pixel of the target.) This affects the accuracy of radar updates and impacts the precision of the navigation and bombing solutions. The experiment evaluated the current cursor and two alternative designs in terms of designation speed and accuracy. Eighteen subjects completed experimental trials in which they performed a SAR radar update procedure (i.e., identified and designated specified aim points). This procedure was conducted using simulated SAR imagery presented on a multipurpose display unit (MDU) within the Computer-Assisted Procedures Trainer (CAPT) residentat Armstrong Laboratory. The results indicated that one of the alternative cursor designs elicited significantly higher designation accuracy (mean error = 1.94 pixels) than the current cursor (mean error = 2.36 pixels) or the second alternative cursor (mean error = 2.28 pixels). Designation speed did not vary significantly across cursors. Subjective data and comments gathered from subjects supported these findings, with the most accurate alternative cursor being rated as very effective and the current cursor being rated as 'somewhat ineffective.'

  11. Monitoring and Mapping Hydroperiod in the South Florida Everglades Using Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Cohen, A.; Wdowinski, S.; Kim, S.

    2008-05-01

    Mapping the hydroperiod of the south Florida Everglades requires detailed spatial and temporal information on changing water levels. Water levels in south Florida are currently being recorded on a regular basis by a network of stage stations; however the complexities of this unique ecosystem create a challenge for understanding and representing the hydrologic cycle at a regional scale using point-source data alone. Incorporating space-based radar data can potentially improve the accuracy of mapping surface inundation patterns and hydroperiod in the Everglades. This research builds on previous studies revealing patterns in radar backscatter (a measurement of the strength of the radar return signal) corresponding with ground features such as changing water levels and vegetation types. We use Synthetic Aperture Radar (SAR) images, in conjunction with daily stage values, to expand upon this research. Our approach is to observe backscatter and water levels along a series of profile lines traversing the Shark River Slough, a wetland depression in the Everglades National Park. Using a profile analysis allows us to observe an area within the Everglades that experiences a relatively large variation in seasonal inundation levels while emphasizing the changes that occur over different types of vegetation. Preliminary results reveal a positive correlation between backscatter and water level in the slough area, which is dominated by marsh interspersed with tree islands, and an inverse correlation in the area east of the slough, which is higher in elevation and consists primarily of herbaceous vegetation. As research in this area progresses, these findings will be incorporated into a rule-based method of classifying radar images in terms of levels of inundation and mapping hydroperiod in the Florida Everglades.

  12. Measurement of Oceanwaves by Airborne Synthetic Aperture Radar using Cross-Track Interferometry Technique

    NASA Astrophysics Data System (ADS)

    Nadai, A.; Umehara, T.; Uratsuka, S.; Sudo, N.

    2012-12-01

    The continuous monitoring of oceanwaves in wide area is difficult by any in-site method. The synthetic aperture radar (SAR) is one of powerful tools to monitor the oceanwaves. The measurement technique of oceanwaves using SAR is investigated using the analysis of the spatial pattern in the intensity image. The intensity method has some disadvantages like that the radar cross section is not related to the oceanwaves directly, that the intensity relation between the measured wave components depends strongly on the geometry of observation, and that the wave height is not able to measure. The cross-track interferometry is a technique to measure the topographic information of the earth surface. In this study, the cross-track interferometry technique is applied to the measurement of ocean waves. The National Institute of Information and Communications Technology has been developed a dual-frequency airborne SAR system named Pi-SAR, in corroboration with the JAXA. The cross-track interferometric function of X-band radar of Pi-SAR can measure the land topography with accuracy of 2m. The oceanwave components measured using the cross-track interferometric method agrees well with those using the intensity method. The intensity relation between the measured wave components using the cross-track interferometry technique is independent to the observation geometry. The results by thecross-track interferometry technique also agree with the in-situ data measured by the buoy and the supersonic wave meters.

  13. Rain effects on the hurricane observations over the ocean by C-band Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Zhang, Guosheng; Li, Xiaofeng; Perrie, William; Zhang, Biao; Wang, Lei

    2016-01-01

    A composite radar scattering model composed of the atmosphere radiative transfer model, and the ocean surface Bragg wave theory is developed to analyze the impact of hurricane rain on the normalized radar-backscatter cross section (NRCS) measured in the VV and cross-polarized C-band Synthetic Aperture Radar (SAR) channels. The model results are validated against SAR and SFMR measured wind speeds and rain rates for two hurricane cases. The contribution of rain to the NRCS is backscatter from two parts: the atmosphere column and the ocean surface. In the atmosphere, microwave attenuation and the rain-induced volume backscattering are simulated by the model. We find that the impact of raindrops in the atmosphere is almost negligible for the VV polarization, but important for the cross polarization. On the ocean surface, comparisons between our model and other existing models without rain lead to the conclusion that the VV polarization NRCS can be simulated reasonably well without considering the non-Bragg scattering mechanisms. Similar to the wave breaking mechanism, the microwave diffraction on the craters, crowns, and stalks, produced by rain drops, is also negligible for VV polarization. However, the non-Bragg scattering is important for the cross-polarized NRCS simulations. Finally, we performed simulations to understand the VV-polarized NRCS behavior under different wind speeds at various rain rates.

  14. Imaging targets embedded in a lossy half space with Synthetic Aperture Radar

    SciTech Connect

    Doerry, A.W.; Brock, B.C.; Boverie, B.; Cress, D.

    1994-05-01

    This paper addresses theoretical aspects of forming images from an airborne Synthetic Aperture Radar (SAR) of targets buried below the earth`s surface. Soil is generally a lossy, dispersive medium, with wide ranging variability in these attributes depending on soil type, moisture content, and a host of other physical properties. Focussing a SAR subsurface image presents new dimensions of complexity relative to its surface-image counterpart, even when the soil`s properties are known. This paper treats the soil as a lossy, dispersive half space, and presents a practical model for the radar echo-delay time to point scatterers within it. This model is then used to illustrate effects of refraction, dispersion, and attenuation on a SAR`s phase histories, and the resulting image. Various data collection geometries and processing strategies are examined for both 2-Dimensional and 3-Dimensional SAR images. The conclusions from this work are that (1) focussing a SAR image must generally take into account both refraction and dispersion, (2) resolving targets at different depths in lossy soils requires perhaps unprecedented sidelobe attenuation, that for some soils may only be achievable with specialized window functions, (3) the impulse response of the soil itself places a practical limit on the usable bandwidth of the radar, and (4) dynamic ranges and sensitivities will need to be orders of magnitude greater than typical surface-imaging SARs, leading to significant impact on SAR parameters, for example compressing the usable range of pulse repetition frequencies (PRFs).

  15. Universal multifractal scaling of synthetic aperture radar images of sea-ice

    SciTech Connect

    Falco, T.; Francis, F.; Lovejoy, S.; Schertzer, D.; Kerman, B.; Drinkwater, M.

    1996-07-01

    Multifrequency, multipolarization imaging radar scattering coefficient data sets, acquired by synthetic aperture radar (SAR) over sea-ice, were studied in order to reveal their scale-invariant properties. Two distinct scenes were acquired at C-band (5.6 cm) and L-band (25 cm) wavelengths for three different linear polarizations (HH, VV, and HV). These sea-ice radar scattering coefficient fields were investigated by applying both Fourier and multifractal analysis techniques. The (multi) scaling of the data is clearly exhibited in both scenes for all three polarizations at L-band and for the HV polarization at C-band. The fields presenting this symmetry were found to be well described by universal multifractals. The corresponding parameters {alpha}, C{sub 1}, and H were determined for all these fields and were found to vary little with only the parameter H (characterizing the degree of nonconservation) displaying some systematic sensitivity to polarization. The values found for the universal multifractal parameters are {alpha} {approx} 1.85 {+-} 0.05, C{sub 1} {approx} 0.0086 {+-} 0.0041, and H {approx} {minus}0.15 {+-} 0.05.

  16. Spatial variations of ocean wave directional spectra from the Seasat synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Beal, R. C.; Gerling, T. W.; Irvine, D. E.; Monaldo, F. M.; Tilley, D. G.

    1986-01-01

    Seasat synthetic aperture radar ocean wave spectra for a 900-km pass are analyzed and interpreted in the context of both their probable generation sources and their surface current and bathymetric modifiers. Systematic vector wavenumber variations of several times the standard error of determination (about 1.5 percent in magnitude and 0.9 deg in direction) occur along the entire 900-km pass. The large-scale spatial variation of a 200-m swell system can be accurately accounted for as a result of dispersion from a distant storm. The more local variations are qualitatively well correlated in position with known currents and bathymetry but show systematic biases that appear partly due to an environmentally dependent instrument transfer function in the regions of high current and highest sea state. There is also substantial evidence that a large angular deviation in the center of the pass is the result of a mesoscale eddy just to the east.

  17. The Use of Multiple-Polarization Data in Foliage Penetrating (FOPEN) Synthetic Aperture Radar (SAR) Applications

    SciTech Connect

    RICHARDS,JOHN A.

    2002-07-01

    Foliage penetrating (FOPEN) synthetic aperture radar (SAR) systems are capable of producing images of targets concealed under a foliage canopy. The quality and interpretability of these images, however, is generally limited by dense foliage clutter and by fundamental foliage-induced image degradation. Use of a polarimetric SAR to provide multiple polarization channels can mitigate these effects by offering target and scene information beyond that provided by a single-polarization SAR. This paper presents the results of a literature survey to investigate the use of multiple-polarization data in conjunction with FOPEN SAR applications. The effects of foliage propagation on SAR image quality are briefly summarized. Various approaches to multiple-polarization-based FOPEN target detection are described. Although literature concerning FOPEN target recognition is scarce, the use of multiple-polarization data for in-the-clear target recognition is described. The applicability of various target detection and recognition applications for use with concealed target SAR (CTSAR) imagery is considered.

  18. New experiments in inverse synthetic aperture radar image exploitation for maritime surveillance

    NASA Astrophysics Data System (ADS)

    Sadjadi, Firooz A.

    2014-06-01

    This paper provides a summary of recent experimental study in using signatures obtained via polarimetric inverse synthetic aperture radar (ISAR) for classification of small boats in littoral environments. First step in discerning the intention of any small boat is to classify and fingerprint it so it can be observed over an extended period of time. Currently, ISAR techniques are used for large ship classification. Large ships tend to have a rich set of discernible features making classification straightforward. However, small boats rarely have a rich set of discernible features, and are more vulnerable to motion-based range migration that leads to severe signature blurring, thus making classification more challenging. The emphasis of this paper is on the development and use of several enhancement methods for polarimetric ISAR imagery of small boats followed by a target classification study whereby the enhanced signatures of two boats were used to extract several separability metrics to ascertain the effectiveness of these distance measure for target classification.

  19. Deep source model for Nevado del Ruiz Volcano, Colombia, constrained by interferometric synthetic aperture radar observations

    NASA Astrophysics Data System (ADS)

    Lundgren, Paul; Samsonov, Sergey V.; López Velez, Cristian Mauricio; Ordoñez, Milton

    2015-06-01

    Nevado del Ruiz is part of a large volcano complex in the northern Andes of Colombia. Interferometric synthetic aperture radar observations from the RADARSAT-2 satellite since 2011 show steady inflation of the volcano since 2012 at 3-4 cm/yr. The broad (>20 km) deformation pattern from both ascending and descending track data constrain source models for either point or spheroidal sources, both located at >14 km beneath the surface (mean elevation 4.2 km) and 10 km SW of Nevado del Ruiz, below nearby Santa Isabel Volcano. Stress change computations for both sources in the context of a compressive regional stress indicate that dikes propagating from the source should become trapped in sills, possibly leading to a more complex pathway to the surface and explaining the significant lateral separation of the source and Nevado del Ruiz Volcano.

  20. Evaluation of a new wavelet-based compression algorithm for synthetic aperture radar images

    NASA Astrophysics Data System (ADS)

    Tian, Jun; Guo, Haitao; Wells, Raymond O., Jr.; Burrus, C. Sidney; Odegard, Jan E.

    1996-06-01

    In this paper we will discuss the performance of a new wavelet based embedded compression algorithm on synthetic aperture radar (SAR) image data. This new algorithm uses index coding on the indices of the discrete wavelet transform of the image data and provides an embedded code to successively approximate it. Results on compressing still images, medical images as well as seismic traces indicate that the new algorithm performs quite competitively with other image compression algorithms. The evaluation for SAR image compression of it will be presented in this paper. One advantage of the new algorithm presented here is that the compressed data is encoded in such a way as to facilitate processing in the compressed wavelet domain, which is a significant aspect considering the rate at which SAR data is collected and the desire to process the data 'near real time'.

  1. Swarm intelligence and fractals in dual-pol synthetic aperture radar image change detection

    NASA Astrophysics Data System (ADS)

    Aghababaee, Hossein; Tzeng, Yu-Chang; Amini, Jalal

    2012-01-01

    We present a novel systematic method for change detection in dual polarimetric (Dual-pol) synthetic aperture radar (SAR) images based on swarm intelligence techniques and fractal geometry. As the two main algorithms of swarm intelligence, ant colony optimization (ACO) and particle swarm optimization (PSO) have great potential in change detection. Additionally, fractal geometry appears to be a highly effective means of characterizing textural features in Dual-pol SAR images. The proposed method exploits fractal images to form a new difference image. Fractal images are computed based on wavelet multiresolution analysis. Moreover, by minimizing an optimal function value in the iteration process, the changes are detected by applying ACO and PSO to the difference image. Experimental results of detecting changes in Dual-pol SAR images reveal that the proposed method is a highly effective and efficient means of change detection in Dual-pol SAR images.

  2. On the focusing issue of synthetic aperture radar imaging of ocean waves

    SciTech Connect

    Bruning, C. ); Alpers, W.R. ); Schroter, J.G. )

    1991-01-01

    It is now widely accepted that the imaging of ocean surface waves by synthetic aperture radar (SAR) can be adequately described by velocity bunching theory in conjunction with the two-scale wave model. However, it has been conjectured that this theory is incapable of explaining why, under certain conditions, the image contrast of airborne SAR imagery of ocean waves can be enhanced by defocusing the SAR processor. It this were true it would raise serious doubts about the validity of the velocity bunching theory to describe the SAR imaging of ocean waves. In this paper the velocity bunching theory is defended. It is shown that image contrast enhancement by defocusing can also be obtained by this theory, which does not require the introduction of the phase or group velocity of the long ocean waves as a basic element of the SAR imaging theory.

  3. Noise and speckle reduction in synthetic aperture radar imagery by nonparametric Wiener filtering.

    PubMed

    Caprari, R S; Goh, A S; Moffatt, E K

    2000-12-10

    We present a Wiener filter that is especially suitable for speckle and noise reduction in multilook synthetic aperture radar (SAR) imagery. The proposed filter is nonparametric, not being based on parametrized analytical models of signal statistics. Instead, the Wiener-Hopf equation is expressed entirely in terms of observed signal statistics, with no reference to the possibly unobservable pure signal and noise. This Wiener filter is simple in concept and implementation, exactly minimum mean-square error, and directly applicable to signal-dependent and multiplicative noise. We demonstrate the filtering of a genuine two-look SAR image and show how a nonnegatively constrained version of the filter substantially reduces ringing. PMID:18354677

  4. Scene estimation from speckled synthetic aperture radar imagery: Markov-random-field approach.

    PubMed

    Lankoande, Ousseini; Hayat, Majeed M; Santhanam, Balu

    2006-06-01

    A novel Markov-random-field model for speckled synthetic aperture radar (SAR) imagery is derived according to the physical, spatial statistical properties of speckle noise in coherent imaging. A convex Gibbs energy function for speckled images is derived and utilized to perform speckle-compensating image estimation. The image estimation is formed by computing the conditional expectation of the noisy image at each pixel given its neighbors, which is further expressed in terms of the derived Gibbs energy function. The efficacy of the proposed technique, in terms of reducing speckle noise while preserving spatial resolution, is studied by using both real and simulated SAR imagery. Using a number of commonly used metrics, the performance of the proposed technique is shown to surpass that of existing speckle-noise-filtering methods such as the Gamma MAP, the modified Lee, and the enhanced Frost. PMID:16715145

  5. Multibeam single frequency synthetic aperture radar processor for imaging separate range swaths

    NASA Technical Reports Server (NTRS)

    Jain, A. (Inventor)

    1979-01-01

    A method and apparatus are described for single frequency multibeam imaging of multiple strips of range swath at high range intervals for those applications where it is desirable to cover a range swath much greater than is possible for a given interpulse interval. Data from a single frequency synthetic aperture radar (in which beam parameters are adjusted so that the return from each successive swath is received during successive interpulse periods) are separated in Dopple frequency for the return from each beam at the frequency plane of the processor. Alternatively, the image formed by each beam may be spatially separated in the azimuth direction and successively selected by positioning an appropriate slit in the recording plane of the processor.

  6. A comparative study on synthetic aperture radar and optical imagery of ocean waves

    NASA Technical Reports Server (NTRS)

    Banner, M. L.; Jain, A.; Stromberg, W.

    1983-01-01

    The ocean imaging capability of synthetic aperture radar (SAR) is examined in terms of an intercomparison between simultaneous, spatially collocated images of a coastal ocean scene, as recorded by aerial photography and aircraft-borne SAR. Based on a detailed study of these images, this paper examines various local features of oceanographic interest as they are imaged by the two methods. This provides information not available in the usual comparisons of normalized SAR and single point buoy spectra. In addition, aspects of the intensity wavenumber spectra of the two images are examined and discussed. An interesting and surprising conclusion arising from the comparison study is the ability of the SAR to image accurately non-uniform (possibly nonlinear) wave features which are imaged by the aerial photography. This result should have important implications on the development of SAR imaging models and the interpretation of the effect of ocean surface motion on the SAR images.

  7. An adaptive quantization method for burst mode synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Joo, T. H.; Held, D. N.

    1985-01-01

    Synthetic aperture radar (SAR) has high data rate because it collects and processes the data coherently. The data rate limitation of the system has to be satisfied while maintaining good image quality. Thus, a quantizer with minimum data rate and high SNR should be employed. An adaptive quantization method is proposed for the burst mode SAR. This adaptive quantizer uses uniformly quantized data to select a subset of bits which is equivalent to changing the step size of the uniform quantizer. A simple implementation which uses the previous burst data to compute the local statistics for the bit selection is presented. The use of previous burst simplifies the implementation because it does not require storage or delay; however, an abrupt change in the terrain could result in incorrect bit selection. An error analysis of this implementation and comparison of two burst mode SAR images formed using the uniformly quantized and adaptively quantized data is presented.

  8. Method and apparatus for Delta Kappa synthetic aperture radar measurement of ocean current

    NASA Technical Reports Server (NTRS)

    Jain, A. (Inventor)

    1985-01-01

    A synthetic aperture radar (SAR) employed for delta k measurement of ocean current from a spacecraft without the need for a narrow beam and long observation times. The SAR signal is compressed to provide image data for different sections of the chirp band width, equivalent to frequencies and a common area for the separate image fields is selected. The image for the selected area at each frequency is deconvolved to obtain the image signals for the different frequencies and the same area. A product of pairs of signals is formed, Fourier transformed and squared. The spectrum thus obtained from different areas for the same pair of frequencies are added to provide an improved signal to noise ratio. The shift of the peak from the center of the spectrum is measured and compared to the expected shift due to the phase velocity of the Bragg scattering wave. Any difference is a measure of current velocity v sub o (delta k).

  9. General adaptive-neighborhood technique for improving synthetic aperture radar interferometric coherence estimation.

    PubMed

    Vasile, Gabriel; Trouvé, Emmanuel; Ciuc, Mihai; Buzuloiu, Vasile

    2004-08-01

    A new method for filtering the coherence map issued from synthetic aperture radar (SAR) interferometric data is presented. For each pixel of the interferogram, an adaptive neighborhood is determined by a region-growing technique driven by the information provided by the amplitude images. Then pixels in the derived adaptive neighborhood are complex averaged to yield the filtered value of the coherence, after a phase-compensation step is performed. An extension of the algorithm is proposed for polarimetric interferometric SAR images. The proposed method has been applied to both European Remote Sensing (ERS) satellite SAR images and airborne high-resolution polarimetric interferometric SAR images. Both subjective and objective performance analysis, including coherence edge detection, shows that the proposed method provides better results than the standard phase-compensated fixed multilook filter and the Lee adaptive coherence filter. PMID:15330474

  10. Some examples of detection of oceanic mesoscale eddies by the Seasat synthetic-aperture radar

    NASA Technical Reports Server (NTRS)

    Fu, L.-L.; Holt, B.

    1983-01-01

    This note presents images of three dynamically different regions in the ocean to demonstrate the variety of mesoscale variabilities detected by the Seasat synthetic-aperture radar (SAR). South of the Grand Banks of Newfoundland, a cold eddy is observed to form as the result of the southward intrusion of Labrador Sea water, perhaps having led to the birth of a Gulf Stream extension ring. Off the northern coast of California, features resulting from the offshore intrusions of cold upwelling water are observed. Two topographically generated eddies are detected near Misteriosa Bank on the Cayman Ridge in the northwestern Caribbean. Comparisons are made with concurrent NOAA-5 infrared images whenever the eddies have thermal signatures.

  11. Implementation of a fast time-domain processor for FMCW Synthetic Aperture Radar data

    NASA Astrophysics Data System (ADS)

    Frioud, Max; Wellig, Peter; Stanko, Stephan; Meier, Erich

    2015-10-01

    For the purpose of getting sensitive information relevant to civil or military security, high-resolution airborne Synthetic Aperture Radar (SAR) provides the possibility to organize missions at short notice regardless of the daylight and of the weather conditions. The use of compact millimeter-wave FMCW SAR systems allows reaching these goals more safely and at lower cost using unmanned lightweight platforms. As a counterpart these platforms are relatively unstable, making the data-processing more difficult. In order to reach optimum focusing quality also in unfavorable flight conditions or for highly non-linear tracks we developed a fast Time-Domain Processor that relies on parallelization using the GPU resources. A production areal processing rate as high as 6 km2/h using 20 cm ground pixel spacing on a single PC station was achieved. The processing quality and efficiency is demonstrated using real data from the MIRANDA35 Ka-band SAR system.

  12. Comparison of synthetic aperture radar and impact-echo imaging for detecting delamination in concrete

    NASA Astrophysics Data System (ADS)

    Popovics, J. S.; Ham, S.; Ghasr, M. T.; Zoughi, R.

    2014-02-01

    In this paper we evaluate the utility of microwave and mechanical wave nondestructive testing techniques to detect delamination in reinforced concrete bridge deck mock-up samples. The mechanical wave tests comprise air-coupled impact-echo measurements, while the microwave measurements comprise three-dimensional synthetic aperture radar imaging using wideband reflectometery in the frequency range of 1-4 GHz. The results of these investigations are presented in terms of images that are generated from these data. Based on a comparison of the results, we show that the two methods are complementary, in that provide distinct capabilities for defect detection. More specifically, the former approach is unable to detect depth of a delaminated region, while the latter may provide this information. Therefore, the two methods may be used in a complementary fashion (i.e., data fusion) to give more comprehensive information about the 3D location of delamination.

  13. Bistatic synthetic aperture radar imaging using wide-bandwidth continuous-wave sources

    NASA Astrophysics Data System (ADS)

    Soumekh, Mehrdad

    1998-10-01

    Monostatic and bistatic Synthetic Aperture Radar (SAR) imaging systems with Wide-Bandwidth Continuous-Wave (WB-CW) sources have been utilized for military reconnaissance. WB-CW sources are less susceptible than FM-CW sources to Electronic Counter Measures (ECM). The main shortcoming of the WB-CW microwave illumination is that its resultant SAR echoed signal is not composed of distinct Doppler spreading around specific tones; this creates difficulties to formulate the image formation in the WB-CW SAR systems via the conventional pulse or FM-CW SAR imaging algorithms. The current paper outlines a Time Domain Correlation (TDC) processing method and a Fourier-based processing method for image formation in WB-CW monostatic and bistatic SAR systems. Results are provided.

  14. National Aeronautics and Space Administration and the Indian Space Research Organisation Synthetic Aperture Radar Mission Concept

    NASA Astrophysics Data System (ADS)

    Bawden, G. W.; Rosen, P. A.; Dubayah, R.; Hager, B. H.; Joughin, I. R.

    2014-12-01

    The U.S. National Aeronautics and Space Administration and the Indian Space Research Organisation are planning a synthetic aperture radar (currently named NISAR) mission for launch in 2020. The mission is a dual L- and S-band polarimetric SAR satellite with a 12-day interferometric orbit and 240 km wide ground swath. The 3-year mission will have a circular sun synchronous orbit (6 am and 6 pm) with a 98° inclination and 747 km altitude that will provide systematic global coverage. Its primary science objectives are to: measure solid Earth surface deformation (earthquakes, volcanic unrest, land subsidence/uplift, landslides); track and understand cryosphere dynamics (glaciers, ice sheets, sea ice, and permafrost); characterize and track changes in vegetation structure and wetlands for understanding ecosystem dynamics and carbon cycle; and support global disaster response. We will describe the current mission concept: the satellite design/capabilities, spacecraft, launch vehicle, and data flow.

  15. Comparison of synthetic aperture radar and impact-echo imaging for detecting delamination in concrete

    SciTech Connect

    Popovics, J. S.; Ham, S.; Ghasr, M. T.; Zoughi, R.

    2014-02-18

    In this paper we evaluate the utility of microwave and mechanical wave nondestructive testing techniques to detect delamination in reinforced concrete bridge deck mock-up samples. The mechanical wave tests comprise air-coupled impact-echo measurements, while the microwave measurements comprise three-dimensional synthetic aperture radar imaging using wideband reflectometery in the frequency range of 1–4 GHz. The results of these investigations are presented in terms of images that are generated from these data. Based on a comparison of the results, we show that the two methods are complementary, in that provide distinct capabilities for defect detection. More specifically, the former approach is unable to detect depth of a delaminated region, while the latter may provide this information. Therefore, the two methods may be used in a complementary fashion (i.e., data fusion) to give more comprehensive information about the 3D location of delamination.

  16. SIR-C L-band/C-band dual-polarization synthetic aperture radar antennas

    NASA Astrophysics Data System (ADS)

    Rait, Gary L.

    1993-08-01

    The SIR-C/X-SAR experiment, a joint effort of NASA, DARA/DLR, and ASI, is a multi- frequency, multi-polarization synthetic aperture radar (SAR) system for spaceborne scientific Earth imaging scheduled for initial launch in April 1994. Its predecessors include the L-Band, single-polarization Seasat, SIR-A, and SIR-B missions of the late 70's and early 80's. Since SIR-C/X-SAR is intended to be the predecessor to the multi-frequency, multi-polarization EOS SAR satellite, it serves to demonstrate and validate various advanced SAR architectures and data products. This paper documents the architecture and performance of the SIR-C L-Band and C-Band active SAR arrays, with emphasis on RF test results and expected performance. Performance at the array level is extrapolated from measurements at the T/R module and antenna subarray levels.

  17. On the soil roughness parameterization problem in soil moisture retrieval of bare surfaces from Synthetic Aperture Radar 1959

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Synthetic Aperture Radar has shown its large potential for retrieving soil moisture maps at regional scales. However, since the backscattered signal is determined by several surface characteristics, the retrieval of soil moisture is an ill-posed problem when using single configuration imagery. Unles...

  18. Eigenvector method for maximum-likelihood estimation of phase errors in synthetic-aperture-radar imagery

    SciTech Connect

    Jakowatz, C.V. Jr.; Wahl, D.E. )

    1993-12-01

    We develop a maximum-likelihood (ML) algorithm for estimation and correction (autofocus) of phase errors induced in synthetic-aperture-radar (SAR) imagery. Here, M pulse vectors in the range-compressed domain are used as input for simultaneously estimating M[minus]1 phase values across the aperture. The solution involves an eigenvector of the sample covariance matrix of the range-compressed data. The estimator is then used within the basic structure of the phase gradient autofocus (PGA) algorithm, replacing the original phase-estimation kernel. We show that, in practice, the new algorithm provides excellent restorations to defocused SAR imagery, typically in only one or two iterations. The performance of the new phase estimator is demonstrated essentially to achieve the Cramer--Rao lower bound on estimation-error variance for all but very small values of target-to-clutter ratio. We also show that for the case in which M is equal to 2, the ML estimator is similar to that of the original PGA method but achieves better results in practice, owing to a bias inherent in the original PGA phase-estimation kernel. Finally, we discuss the relationship of these algorithms to the shear-averaging and spatial-correlation methods, two other phase-correction techniques that utilize the same phase-estimation kernel but that produce substantially poorer performance because they do not employ several fundamental signal-processing steps that are critical to the algorithms of the PGA class.

  19. Moving Target Indication via RADARSAT-2 Multichannel Synthetic Aperture Radar Processing

    NASA Astrophysics Data System (ADS)

    Chiu, S.; Dragošević, M. V.

    2009-12-01

    With the recent launches of the German TerraSAR-X and the Canadian RADARSAT-2, both equipped with phased array antennas and multiple receiver channels, synthetic aperture radar, ground moving target indication (SAR-GMTI) data are now routinely being acquired from space. Defence R&D Canada has been conducting SAR-GMTI trials to assess the performance and limitations of the RADARSAT-2 GMTI system. Several SAR-GMTI modes developed for RADARSAT-2 are described and preliminary test results of these modes are presented. Detailed equations of motion of a moving target for multiaperture spaceborne SAR geometry are derived and a moving target parameter estimation algorithm developed for RADARSAT-2 (called the Fractrum Estimator) is presented. Limitations of the simple dual-aperture SAR-GMTI mode are analysed as a function of the signal-to-noise ratio and target speed. Recently acquired RADARSAT-2 GMTI data are used to demonstrate the capability of different system modes and to validate the signal model and the algorithm.

  20. Simulating the effects of long-range collection on synthetic aperture radar imagery

    NASA Astrophysics Data System (ADS)

    Richards, John A.

    2009-05-01

    Synthetic aperture radar (SAR) images exhibit a fundamental inverse relationship between image quality and collection range: various metrics and visual inspection clearly indicate that SAR image quality deteriorates as collection range increases. Standoff constraints typically dictate long-range imaging geometries for operational use of fielded SAR sensors. At the same time, system validation and data volume considerations typically dictate short-range imaging geometries for non-operational SAR data collections. This presents a conundrum for the developers of SAR exploitation applications: despite the fact that a sensor may be used exclusively at long ranges in operational settings, most or all of the data available for application development and testing may have been collected at short range. The lack of long-range imagery for development and testing can lead to a variety of problems, potentially including not only poor robustness to range-induced image-quality degradation, but even total failure if longer-range imagery invalidates fundamental algorithmic assumptions. We propose a method for simulating the effects of longer-range collection using shorter-range SAR images. This method incorporates the predominant contributing factors to range-induced image-quality degradation, including various signal-attenuation and aperture-decoherence effects. We present examples demonstrating our approach.

  1. On the convergence of the phase gradient autofocus algorithm for synthetic aperture radar imaging

    SciTech Connect

    Hicks, M.J.

    1996-01-01

    Synthetic Aperture Radar (SAR) imaging is a class of coherent range and Doppler signal processing techniques applied to remote sensing. The aperture is synthesized by recording and processing coherent signals at known positions along the flight path. Demands for greater image resolution put an extreme burden on requirements for inertial measurement units that are used to maintain accurate pulse-to-pulse position information. The recently developed Phase Gradient Autofocus algorithm relieves this burden by taking a data-driven digital signal processing approach to estimating the range-invariant phase aberrations due to either uncompensated motions of the SAR platform or to atmospheric turbulence. Although the performance of this four-step algorithm has been demonstrated, its convergence has not been modeled mathematically. A new sensitivity study of algorithm performance is a necessary step towards this model. Insights that are significant to the application of this algorithm to both SAR and to other coherent imaging applications are developed. New details on algorithm implementation identify an easily avoided biased phase estimate. A new algorithm for defining support of the point spread function is proposed, which promises to reduce the number of iterations required even for rural scenes with low signal-to-clutter ratios.

  2. Joint azimuth and elevation localization estimates in 3D synthetic aperture radar scenarios

    NASA Astrophysics Data System (ADS)

    Pepin, Matthew

    2015-05-01

    The location of point scatterers in Synthetic Aperture Radar (SAR) data is exploited in several modern analyzes including persistent scatter tracking, terrain deformation, and object identification. The changes in scatterers over time (pulse-to-pulse including vibration and movement, or pass-to-pass including direct follow on, time of day, and season), can be used to draw more information about the data collection. Multiple pass and multiple antenna SAR scenarios have extended these analyzes to location in three dimensions. Either multiple passes at different elevation angles may be .own or an antenna array with an elevation baseline performs a single pass. Parametric spectral estimation in each dimension allows sub-pixel localization of point scatterers in some cases additionally exploiting the multiple samples in each cross dimension. The accuracy of parametric estimation is increased when several azimuth passes or elevations (snapshots) are summed to mitigate measurement noise. Inherent range curvature across the aperture however limits the accuracy in the range dimension to that attained from a single pulse. Unlike the stationary case where radar returns may be averaged the movement necessary to create the synthetic aperture is only approximately (to pixel level accuracy) removed to form SAR images. In parametric estimation increased accuracy is attained when two dimensions are used to jointly estimate locations. This paper involves jointly estimating azimuth and elevation to attain increased accuracy 3D location estimates. In this way the full 2D array of azimuth and elevation samples is used to obtain the maximum possible accuracy. In addition the independent dimension collection geometry requires choosing which dimension azimuth or elevation attains the highest accuracy while joint estimation increases accuracy in both dimensions. When maximum parametric estimation accuracy in azimuth is selected the standard interferometric SAR scenario results. When maximum estimation accuracy in elevation is selected the multiple baseline interferometric SAR scenario results. Use of a 2D parametric estimation method attains the best accuracy possible in both dimensions. When in some scenarios particularly the orbital case where the azimuth dimension is only approximately linear the full accuracy increase of linear joint azimuth and elevation is not fully attained. Images and point cloud estimates are shown for several linear and orbital SAR scenarios. Images provide a visual representation of the data while the quantitative point cloud data is a direct input for the multiple analyzes listed earlier.

  3. Determining the mixing of oil and sea water using polarimetric synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Minchew, Brent

    2012-08-01

    Knowledge of the characteristics of spilled oil in the ocean is important for cleanup operations, predictions of the impact on wildlife, and studies of the nature of the ocean surface and currents. Herein I discuss a method for evaluating the characteristics of oil in a marine environment using synthetic aperture radar (SAR) and present a new, simple classification, called the oil/water mixing index (Mdex), to quickly assess the results. I link the Mdex results to the Bonn Agreement for Oil Appearance Codes (BAOAC) for aerial observers and demonstrate the Mdex on Uninhabited Aerial Vehicle SAR (UAVSAR) data collected June 23, 2010 over the former site of the Deepwater Horizon (DWH) drilling rig. The Mdex map shows a more heterogeneous oil swath than do radar backscatter images and features within the oil are consistent with features present in previously published, near-coincident optical imagery. The Mdex results indicate that most of the oil near the DWH was mixed with sea water to a minimum depth of a few millimeters, though some areas containing relatively thin films are observed.

  4. Synthetic aperture radar and natural disasters: Hazard mapping using full polarimetry

    NASA Astrophysics Data System (ADS)

    Czuchlewski, Kristina Rodriguez

    This thesis focuses on developing algorithms for radar-based natural disaster response. We demonstrate that fully-polarimetric Synthetic Aperture Radar (SAR) can be used to assess natural disasters involving terrain resurfacing such as landslides, volcanic eruptions and fires. These hazards often temporarily remove a natural vegetation cover and, in doing so, modify the physical properties of the land surface. This land-cover disturbance causes a detectable change in dominant microwave scattering mechanism for the areas affected. SAR has operational advantages over optical sensors for rapid disaster assessment because of its day/night acquisition capability; its ability to "see through" smoke, clouds and dust; and its side-looking viewing geometry, which is an advantage whenever data collection directly above the site would prove dangerous. To assess the usefulness of fully-polarimetric SAR, we apply a uniform approach to map (1) landslides resulting from the 1999 Mw 7.6 Chi-Chi earthquake in Taiwan, (2) volcanic flows from the major 1996 eruption of Manam Volcano in Papua New Guinea, and (3) the extent of damage from the summer 2002 Rodeo-Chediski wildfire in Arizona, USA. We then reexamine the data from Manam Island and Taiwan to determine the effects of a polarization preserving speckle reduction filter. Our results demonstrate the potential utility of fully polarimetric SAR for hazard mapping and disaster response.

  5. Detection of regolith buried water stream channels on Mars with the help of synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Rzhiga, O. N.

    2009-09-01

    A major theme in the study of Mars is the search for evidence that water was present in the past or is present today, either at or below the surface. Biological life is connected to water. Hence much research is focused on the detection of water stream channels, which in the past flowed on Mars. In these areas, the petrified remains of the former life on Mars may be found. These channels may be under the regolith layer; however, the radio wave penetrating ability allows for the detection of these channels under the regolith. In this work, a model based on the geometrical optics representations of signal formation from the reflection of radio waves from the regolith buried channel is developed. It is supposed, that on Mars bedrock (ledge rocks) are closed by regolith. Using certain assumptions of the electric properties of the regolith and bedrock, a radar image of the channel can be constructed. The optimum wavelength for detection of the channels, now buried by the regolith, is determined. The analysis of the reflected signal level dependence on the angle from which the synthetic aperture radar is directed at the planet's surface is carried out. Is established, that the optimum wavelength for detection of regolith buried channels sharply depends on tangent of regolith losses angle and thickness of its upper layer. Depending on parameter C describing degree of surface roughness in scale, which is more than wavelength, the optimum wavelength changes little.

  6. Ground-penetrating synthetic-aperture radar for wide-area airborne minefield detection

    NASA Astrophysics Data System (ADS)

    Moussally, George J.; Fries, Robert W.; Bortins, Richard

    2004-09-01

    This paper describes data collection and test results from an airborne ground penetrating radar (GPR) sensor operating as a synthetic aperture radar (SAR). Tests were undertaken to investigate the sensor's capability to support wide-area airborne minefield detection. The sensor was installed on a rotorcraft unmanned aerial vehicle (UAV). Flight tests occurred in 2002/3 at several US Army test sites containing minefields comprised of diverse types of anti-tank landmines, both metallic and low-metallic, that were buried and surface-laid. Data was collected using two side-look SAR modes: strip-map and spotlight. Strip-map mode data was collected using linear flight paths. Spotlight mode data was collected over a path surrounding the survey region allowing the sensor to collect minefield data over a full 360° view in azimuth. Data collected in strip-map mode was processed to form two-dimensional SAR imagery of the minefields. Three dimensional images were generated by processing the 360° spotlight mode data. The images were generated in a geo-referenced coordinate system to allow direct comparison of the imagery with surveyed ground truth. The sensor system is described and the flight tests that were undertaken are explained. Examples of SAR imagery from the flight tests are presented and compared to surveyed ground truth.

  7. A 2D wavenumber domain phase model for ground moving vehicles in synthetic aperture radar imagery

    NASA Astrophysics Data System (ADS)

    Marechal, Nicholas; Dickinson, Richard; Karamyan, Grant

    2013-05-01

    In this paper, fundamental phase characteristics of moving vehicles in synthetic aperture radar (SAR) data are reviewed. A 2D phase model for a moving point scatterer is expressed in terms of range and azimuth wavenumbers. The moving point scatterer impulse response is then the 2D Fourier transform of the associated complex sinusoid. Numerical computation of the 2D phase for arbitrary relative radar-point scatter motion is organized as a composition of functions expressing time, frequency and angle in terms of wavenumber vectors. An analytic model for the phase is subsequently derived in the special case that the Doppler cone angle is 90°. With that model it is observed that the map from velocity and acceleration to quadratic phase is not one-to-one and therefore the associated inverse problem is ill-posed. An example of moving vehicle Doppler energy dispersion and corresponding phase measured in clutter suppressed SAR image data is provided. Clutter suppression is achieved by application of spacetime adaptive processing.

  8. Early Warning Monitoring of Natural and Engineered Slopes with Ground-Based Synthetic-Aperture Radar

    NASA Astrophysics Data System (ADS)

    Atzeni, C.; Barla, M.; Pieraccini, M.; Antolini, F.

    2015-01-01

    The first application of ground-based interferometric synthetic-aperture radar (GBInSAR) for slope monitoring dates back 13 years. Today, GBInSAR is used internationally as a leading-edge tool for near-real-time monitoring of surface slope movements in landslides and open pit mines. The success of the technology relies mainly on its ability to measure slope movements rapidly with sub-millimetric accuracy over wide areas and in almost any weather conditions. In recent years, GBInSAR has experienced significant improvements, due to the development of more advanced radar techniques in terms of both data processing and sensor performance. These improvements have led to widespread diffusion of the technology for early warning monitoring of slopes in both civil and mining applications. The main technical features of modern SAR technology for slope monitoring are discussed in this paper. A comparative analysis with other monitoring technologies is also presented along with some recent examples of successful slope monitoring.

  9. Nonlinear techniques in optical synthetic aperture radar image generation and target recognition.

    PubMed

    Weaver, S; Wagner, K

    1995-07-10

    One of the most successful optical signal-processing applications to date has been the use of optical processors to convert synthetic aperture radar (SAR) data into images of the radar reflectivity of the ground. We have demonstrated real-time input to a high-space-bandwidth optical SAR imagegeneration system by using a dynamic organic holographic recording medium and SAR phase-history data. Real-time speckle reduction in optically processed SAR imagery has been accomplished by the use of multilook averaging to achieve nonlinear modulus-squared accumulation of subaperture images. We designed and assembled an all-optical system that accomplished real-time target recognition in SAR imagery. This system employed a simple square-law nonlinearity in the form of an optically addressed spatial light modulator at the SAR image plane to remove the effects of speckle phase profiles returned from complex SAR targets. The detection stage enabled the creation of an optical SAR automatic target recognition system as a nonlinear cascade of an optical SAR image generator and an optical correlator. PMID:21052221

  10. A High Resolution, Light-Weight, Synthetic Aperture Radar for UAV Application

    SciTech Connect

    Doerry, A.W.; Hensley, W.H.; Stence, J.; Tsunoda, S.I. Pace, F.; Walker, B,C.; Woodring, M.

    1999-05-27

    (U) Sandia National Laboratories in collaboration with General Atomics (GA) has designed and built a high resolution, light-weight, Ku-band Synthetic Aperture Radar (SAR) known as "Lynx". Although Lynx can be operated on a wide variety of manned and unmanned platforms, its design is optimized for use on medium altitude Unmanned Aerial Vehicles (UAVS). In particular, it can be operated on the Predator, I-GNAT, and Prowler II platforms manufactured by GA. (U) The radar production weight is less than 120 lb and operates within a 3 GHz band from 15.2 GHz to 18.2 GHz with a peak output power of 320 W. Operating range is resolution and mode dependent but can exceed 45 km in adverse weather (4 mm/hr rain). Lynx has operator selectable resolution and is capable of 0.1 m resolution in spotlight mode and 0.3 m resolution in stripmap mode, over substantial depression angles (5 to 60 deg) and squint angles (broadside ±45 deg). Real-time Motion Compensation is implemented to allow high-quality image formation even during vehicle turns and other maneuvers.

  11. New autofocus technique for wideband wide-angle synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Kirk, David; Maloney, Paul

    1998-09-01

    A small difference between the true range to the scatterer and that estimated from the radar time delay results in defocusing of Synthetic Aperture Radar (SAR) imagery in both cross-range and range directions. The amount of defocusing is a function of the integration angle and range resolution. SARs with large integration angles and high range resolution are particularly sensitive to the range error. In the UltraWide Band P-3 SAR, for example, there is an error in the knowledge of the absolute range on the order of 100 m, which results in a very poorly focused images. The current processing procedure is to form multiple SAR images using a different range estimate to form each image, where the range estimates used span the expected variation in the range error. The SAR image with the best image quality is used. This is clearly a very time consuming approach and not suitable for a real-time system. This paper describes a new technique called Autofocus Estimation of Range Error which employs a conventional autofocus algorithm to estimate the phase error in a poorly focused image and then converts this into an estimate of the absolute range. The image is then reprocessed with the improved absolute range estimate. This paper discusses how this technique is implemented and demonstrates the improvement in image quality that can be achieved with this technique as opposed to using conventional autofocus techniques.

  12. Analysis Of Atmoshperic Effects On X-Band Synthetic Aperture Radar Observations And Precipitations Estimation

    NASA Astrophysics Data System (ADS)

    Mori, S.; Pulvirenti, L.; Marzano, F. S.; Pierdicca, N.

    2013-12-01

    This paper proposes a new methodology for the detection and quantitative estimation of intense atmospheric precipitations on images acquired by Synthetic Aperture Radars (SARs) operating at X-Band wavelengths. The proposed methodology consists of two successive steps. The first one allows detecting and distinguishing areas subjected to intense precipitation events, permanent water surfaces, flood areas and snow coverage. The second step derives an estimation of the precipitation rate using the event attenuation estimated at the previous step. This methodology is applied on two COSMO-SkyMed (CSK) satellite case studies. The first one is relative to a severe precipitation weather event, occurred in northwestern Italy (close to Liguria region) on November 3-8, 2011. The second one is relative to Hurricane “Irene” event, occurred in Eastern United States (close to Delaware) on late August 2011. In both cases X-SAR echoes and estimated rain rate is compared with corresponding products derived by available ground Weather Radars (WRs). The correlation of the precipitating cloud fields between CSK X-SAR and WR images is significant in all case studies.

  13. SAR-EDU - An education initiative for applied Synthetic Aperture Radar remote sensing

    NASA Astrophysics Data System (ADS)

    Eckardt, Robert; Richter, Nicole; Auer, Stefan; Eineder, Michael; Roth, Achim; Hajnsek, Irena; Walter, Diana; Braun, Matthias; Motagh, Mahdi; Pathe, Carsten; Pleskachevsky, Andrey; Thiel, Christian; Schmullius, Christiane

    2013-04-01

    Since the 1970s, radar remote sensing techniques have evolved rapidly and are increasingly employed in all fields of earth sciences. Applications are manifold and still expanding due to the continuous development of new instruments and missions as well as the availability of very high-quality data. The trend worldwide is towards operational employment of the various algorithms and methods that have been developed. However, the utilization of operational services does not keep up yet with the rate of technical developments and the improvements in sensor technology. With the enhancing availability and variety of space borne Synthetic Aperture Radar (SAR) data and a growing number of analysis algorithms the need for a vital user community is increasing. Therefore the German Aerospace Center (DLR) together with the Friedrich-Schiller-University Jena (FSU) and the Technical University Munich (TUM) launched the education initiative SAR-EDU. The aim of the project is to facilitate access to expert knowledge in the scientific field of radar remote sensing. Within this effort a web portal will be created to provide seminar material on SAR basics, methods and applications to support both, lecturers and students. The overall intension of the project SAR-EDU is to provide seminar material for higher education in radar remote sensing covering the topic holistically from the very basics to the most advanced methods and applications that are available. The principles of processing and interpreting SAR data are going to be taught using test data sets and open-source as well as commercial software packages. The material that is provided by SAR-EDU will be accessible at no charge from a DLR web portal. The educational tool will have a modular structure, consisting of separate modules that broach the issue of a particular topic. The aim of the implementation of SAR-EDU as application-oriented radar remote sensing educational tool is to advocate the development and wider use of operational services on the base of pre-existing algorithms and sensors on the one hand, and to aid the extension of radar remote sensing techniques to a broader field of application on the other. SAR-EDU therefore combines the knowledge, expertise and experience of an excellent German consortium.

  14. Real-time implementation of frequency-modulated continuous-wave synthetic aperture radar imaging using field programmable gate array.

    PubMed

    Quan, Yinghui; Li, Yachao; Hu, Guibin; Xing, Mengdao

    2015-06-01

    A new miniature linear frequency-modulated continuous-wave radar which mounted on an unmanned aerial vehicle is presented. It allows the accomplishment of high resolution synthetic aperture radar imaging in real-time. Only a Kintex-7 field programmable gate array from Xilinx is utilized for whole signal processing of sophisticated radar imaging algorithms. The proposed hardware architecture achieves remarkable improvement in integration, power consumption, volume, and computing performance over its predecessor designs. The realized design is verified by flight campaigns. PMID:26133857

  15. Ionospheric Effects on Spaceborne Synthetic Aperture Radar and a New Capability of Imaging the Ionosphere From Space

    NASA Astrophysics Data System (ADS)

    Pi, Xiaoqing

    2015-11-01

    This article reviews research activities and results in a new field, where ionospheric effects on spaceborne synthetic aperture radar have been investigated and techniques of imaging the ionosphere using the same radar are also explored. The research was originally to minimize ionospheric-induced distortions and contaminations in Earth remote sensing observations. As a product, the radar-based high-resolution ionospheric imaging from a low Earth orbit satellite can also benefit studies of space weather effects on the ionospheric density distribution in essentially all latitude regions, which would provide useful information to studies of coupling of the magnetosphere, ionosphere, and thermosphere.

  16. Application of equalization notch to improve synthetic aperture radar coherent data products

    NASA Astrophysics Data System (ADS)

    Musgrove, Cameron; West, James C.

    2015-05-01

    Interference and interference mitigation techniques degrade synthetic aperture radar (SAR) coherent data products. Radars utilizing stretch processing present a unique challenge for many mitigation techniques because the interference signal itself is modified through stretch processing from its original signal characteristics. Many sources of interference, including constant tones, are only present within the fast-time sample data for a limited number of samples, depending on the radar and interference bandwidth. Adaptive filtering algorithms to estimate and remove the interference signal that rely upon assuming stationary interference signal characteristics can be ineffective. An effective mitigation method, called notching, forces the value of the data samples containing interference to zero. However, as the number of data samples set to zero increases, image distortion and loss of resolution degrade both the image product and any second order image products. Techniques to repair image distortions,1 are effective for point-like targets. However, these techniques are not designed to model and repair distortions in SAR image terrain. Good terrain coherence is important for SAR second order image products because terrain occupies the majority of many scenes. For the case of coherent change detection it is the terrain coherence itself that determines the quality of the change detection image. This paper proposes an unique equalization technique that improves coherence over existing notching techniques. First, the proposed algorithm limits mitigation to only the samples containing interference, unlike adaptive filtering algorithms, so the remaining samples are not modified. Additionally, the mitigation adapts to changing interference power such that the resulting correction equalizes the power across the data samples. The result is reduced distortion and improved coherence for the terrain. SAR data demonstrates improved coherence from the proposed equalization correction over existing notching methods for chirped interference sources.

  17. Validation of cresis synthetic aperture radar processor and optimal processing parameters

    NASA Astrophysics Data System (ADS)

    Smith, Logan Sanders

    Sounding the ice sheets of Greenland and Antarctica is a vital component in determining the effect of global warming on sea level rise. Of particular importance are measurements of the bedrock topography of the outlet glaciers that transport ice from the ice sheet's interior to the margin where it calves into icebergs, contributing to sea level rise. These outlet glaciers are difficult to sound due to crevassing caused by the relatively fast movement of the ice in the glacial channel and higher signal attenuation caused by warmer ice. The Center for Remote Sensing of Ice Sheets (CReSIS) uses multi-channel airborne radars which employ methods for achieving better resolution and signal-to-noise ratio (SNR) to better sound outlet glaciers. Synthetic aperture radar (SAR) techniques are used in the along-track dimension, pulse compression in the range dimension, and an antenna array in the cross-track dimension. CReSIS has developed the CReSIS SAR processor (CSARP) to effectively and efficiently process the data collected by these radars in each dimension. To validate the performance of this processor a SAR simulator was developed with the functionality to test the implementation of the processing algorithms in CSARP. In addition to the implementation of this simulator for validation of processing the data in the along-track, cross-track and range dimensions, there are a number of data-dependent processing steps that can affect the quality of the final data product. CSARP was tested with an ideal simulated point target in white Gaussian noise. The SNR change achieved by range compression, azimuth compression, array combination with and without matched filtering, and lever arm application were all within .2 dB of the theoretical expectation. Channel equalization, when paired with noise-based matched filtering, provided 1-2 dB of gain on average but significantly less than the expected gain. Extending the SAR aperture length to sound bedrock will improve the along-track resolution, but at the expense of SNR. Increasing the taper of a window in the fast-time and slow-time will slightly improve the SNR of the data. Changing the relative permittivity used to process the data improved the resulting SNR by no more than 0.025 dB for the test dataset.

  18. Study of the Effects of Target Geometry on Synthetic Aperture Radar Images using Simulation Studies

    NASA Astrophysics Data System (ADS)

    Tummala, K.; Jha, A. K.; Kumar, S.

    2014-11-01

    Synthetic aperture radar technology has revolutionized earth observation with very high resolutions of below 5m, making it possible to distinguish individual urban features like buildings and even cars on the surface of the earth. But, the difficulty in interpretation of these images has hindered their use. The geometry of target objects and their orientation with respect to the SAR sensor contribute enormously to unexpected signatures on SAR images. Geometry of objects can cause single, double or multiple reflections which, in turn, affect the brightness value on the SAR images. Occlusions, shadow and layover effects are present in the SAR images as a result of orientation of target objects with respect to the incident microwaves. Simulation of SAR images is the best and easiest way to study and understand the anomalies. This paper discusses synthetic aperture radar image simulation, with the study of effect of target geometry as the main aim. Simulation algorithm has been developed in the time domain to provide greater modularity and to increase the ease of implementation. This algorithm takes into account the sensor and target characteristics, their locations with respect to the earth, 3-dimensional model of the target, sensor velocity, and SAR parameters. two methods have been discussed to obtain position and velocity vectors of SAR sensor - the first, from the metadata of real SAR image used to verify the simulation algorithm, and the second, from satellite orbital parameters. Using these inputs, the SAR image coordinates and backscatter coefficients for each point on the target are calculated. The backscatter coefficients at target points are calculated based on the local incidence angles using Muhleman's backscatter model. The present algorithm has been successfully implemented on radarsat-2 image of San Francisco bay area. Digital elevation models (DEMs) of the area under consideration are used as the 3d models of the target area. DEMs of different resolutions have been used to simulate SAR images in order to study how the target models affect the accuracy of simulation algorithm. The simulated images have been compared with radarsat-2 images to observe the efficiency of the simulation algorithm in accurately representing the locations and extents of different objects in the target area. The simulated algorithm implemented in this paper has given satisfactory results as the simulated images accurately show the different features present in the DEM of the target area.

  19. Modeling atmospheric precipitation impact on synthetic aperture radar imagery at X and Ka bands

    NASA Astrophysics Data System (ADS)

    Mori, Saverio; Polverari, Federica; Pulvirenti, Luca; Montopoli, Mario; Pierdicca, Nazzareno; Marzano, Frank S.

    2014-10-01

    Spaceborne synthetic aperture radars (SARs) operating at X-band and above allow observations of Earth surface at very high spatial resolution. Moreover, recent polarimetric SARs enable the complete characterization of target scattering and extinction properties. Nowadays several spaceborne X-band SAR systems are operative, and plans exist for systems operating at higher frequency bands (i.e. Ku, Ka and W). Although higher frequencies may have interesting and distinctive applications, atmospheric effects, especially in precipitating conditions, may affect the surface SAR response in both the signal amplitude and its phase, as assessed by numerous works in the last years. A valid tool to analyze and characterize the SAR response in these conditions is represented by forward modeling, where a known synthetic scenario, which is described by user-selected surface and atmospheric conditions, is considered. Thus, the SAR echoes corresponding to the synthetic scenarios are simulated using electromagnetic models. In this work a 3-D realistic polarimetric SAR response numerical simulator is presented. The proposed model framework accounts for the SAR slant observing geometry and it is able to characterize the polarimetric response both in amplitude and phase. In this work we have considered both X and Ka bands, thus exploring the atmospheric effects for the present and future polarimetric systems. The atmospheric conditions are simulated using the System for Atmospheric Modeling (SAM) which is an high-resolution mesoscale model. SAM is used to define the three-dimensional distribution of hydrometeors which are among the inputs used in the Hydrometeor Ensemble Scattering Simulator (HESS) T-Matrix which allow simulating the SAR signal due to the atmospheric component. The SAR surface component is, instead, simulated by a Semi Empirical Model (SEM) for bare-soils conditions and SEAWIND2 two-scale model for ocean surfaces. The proposed methodology has been applied in this work to assess the sensitivity of the considered frequency bands to different hydrometeor spatial distributions above some examples surface backgrounds.

  20. Spaceborne Synthetic Aperture Radar (SAR) Doppler anomalies due to volcanic eruption induced phenomena

    NASA Astrophysics Data System (ADS)

    de Michele, Marcello; Raucoules, Daniel; Minet, Christian

    2015-04-01

    In the frame of the EU funded "MEDSUV" supersite project, we use multiple SAR data to investigate Doppler anomalies in the SAR signal occurring during volcanic eruptions. In Synthetic Aperture Radar, variations in the Electro Magnetic Waves travel time results in a change in the Doppler frequency that adds up to the one that is naturally generated by the relative motion between the platform and the ground targets. Within the SAR system, frequencies modulations control the image focusing along the two fundamental SAR directions, the azimuth (i.e. the platform motion direction) and the range (i. e. the sensor looking direction). During the synthetic aperture process (the so called image focusing) a target on the surface is seen along different paths. In standard focusing processing it is assumed both that ground targets are stationary and that between the sensor and the target the medium is the vacuum or a totally homogeneous medium. Therefore, if there is a significant path delay variation along the paths to a specific target this can result either in image defocusing or in pixel misregistration or both. It has been shown that SAR Doppler history anomalies can occur over volcanic areas. The goal of this study is to highlight Doppler history anomalies occurring during the SAR image formation over active volcanoes on a number of test cases. To do so, we apply a sub-aperture cross correlation algorithm on Single Look Complex data. Practically, we measure any pixel misregistration between two sub-looks of the same SAR acquisition. If a pixel shift occurs, it means that the expected radar wave path has been lengthened (or shortened) during the time when ground surface scatterers were illuminated by the sensor radiation either by a ground feature velocity (e. g. water flows, vehicles) or it is refracted by a strong medium discontinuity in the air (volcanic ash plume?). If a Doppler history anomaly is detected by the sub-aperture cross correlation, we try to explore whether it is possible to distinguish between signal delays due to the presence of a volcanic ash plume and the signal delays due to other volcano-related phenomena (such as lahars, lava flows velocity, ice melts, ocean currents induced/modified by lahars discharges), or simply non volcano-related natural phenomena such as ocean currents and river flows. We focus on the largest eruption producing an ash plume in the last decade, the 2010 Eyjafjallajokull eruption in Iceland by using a selected set of data from the German Space Agency (DLR) TerraSAR-X sensor. The first outcome of this analysis is that our methodology to detect Doppler anomalies on TerraSAR-X data works at least for extended surface motions signatures (ocean swell). A preliminary analysis of the results, allows us to reasonably state that we do not see a flashy impact of the ash plume on the Doppler history of the SAR data. We see sporadic, spatially discontinuous Doppler anomalies around the volcanic edifice and on the top, but it is premature to link those to the presence of a volcanic ash plume. On the other hand, our results put into evidence Doppler shifts reasonably due to eruption-induced ice melts, lahars, river discharge and consequent modification of the near shore ocean currents. These signals worth a deeper analysis as these natural eruption-induced phenomena heavily impact the surrounding environment. Besides, further investigations have to be performed both on archived C-band SAR on Etna volcano and, particularly important, on the new SENTINEL-1 data and its specific TOPSAR mode that could be more complex to use for such applications.

  1. Monitoring Changes in Aboveground Biomass in Loblolly Pine Forests Using Multichannel Synthetic Aperture Radar Data

    NASA Astrophysics Data System (ADS)

    Kasischke, Eric Stewart

    A study was conducted to evaluate using synthetic aperture radar (SAR) for estimating aboveground biomass in loblolly pine (Pinus taeda L.) forests. The data set for this experiment was a multiple-frequency (C-, L- and P-band), polarimetric SAR data set collected by the NASA/JPL AIRSAR System over the Duke University Research Forest located near Durham, North Carolina. In addition to the SAR data set, a set of ground measurements were collected to describe the tree geometry and biomass characteristics from 59 different stands consisting principally of loblolly pine within the Duke Forest. The aboveground, dry weight woody biomass in these test stands ranges from < 1 to >50 kg-m^2. The first analysis performed on this data set was to produce algorithms to estimate both dry and wet weight biomasses for each of the test stands, and to distribute this biomass amongst various tree components (e.g., boles, branches, and needles/leaves) as well as the different layers within the tree canopy (e.g., canopy, subcanopy and understory) in order to better relate biomass to the radar backscattering measurements. This was accomplished by development of allometric equations to estimate biomass for individual trees, from which stand estimates on an aerial basis were derived. The biomass estimates were then statistically correlated with radar backscatter (sigma ^circ) measurements derived from the SAR data set. It was found that sigma^ circ at a variety of radar frequencies (P, L, and C-bands) and linear-polarization combinations (HH, HV, and VV) were significantly correlated (at a level of significance of p = 0.001) to either individual biomass components (e.g., bole biomass, branch biomass, needle/leaf biomass, etc.) or multiple combinations of these components. While the correlations were significant at all linear polarizations at L- and P-bands, they were only significant in the cross -polarized channel at C-band. Finally, a two-step method was developed to estimate aboveground biomass from multichannel SAR data. The error estimate (coefficient of variation) for the various biomass components ranged between 16% and 27%. It is concluded that the pine stand biomasses (dry weight) for which these algorithms are valid range between 15 and 40 kg-m ^{2}.

  2. Spatial Estimation of Soil Moisture Using Synthetic Aperture Radar in Alaska

    NASA Astrophysics Data System (ADS)

    Meade, N. G.; Hinzman, L. D.; Kane, D. L.

    1999-01-01

    A spatially distributed Model of Arctic Thermal and Hydrologic processes (MATH) has been developed. One of the attributes of this model is the spatial and temporal prediction of soil moisture in the active layer. The spatially distributed output from this model required verification data obtained through remote sensing to assess performance at the watershed scale independently. Therefore, a neural network was trained to predict soil moisture contents near the ground surface. The input to train the neural network is synthetic aperture radar (SAR) pixel value, and field measurements of soil moisture, and vegetation, which were used as a surrogate for surface roughness. Once the network was trained, soil moisture predictions were made based on SAR pixel value and vegetation. These results were then used for comparison with results from the hydrologic model. The quality of neural network input was less than anticipated. Our digital elevation model (DEM) was not of high enough resolution to allow exact co-registration with soil moisture measurements; therefore, the statistical correlations were not as good as hoped. However, the spatial pattern of the SAR derived soil moisture contents compares favorably with the hydrologic MATH model results. Primary surface parameters that effect SAR include topography, surface roughness, vegetation cover and soil texture. Single parameters that are considered to influence SAR include incident angle of the radar, polarization of the radiation, signal strength and returning signal integration, to name a few. These factors influence the reflectance, but if one adequately quantifies the influences of terrain and roughness, it is considered possible to extract information on soil moisture from SAR imagery analysis and in turn use SAR imagery to validate hydrologic models

  3. Indoor experimental facility for airborne synthetic aperture radar (SAR) configurations - rail-SAR

    NASA Astrophysics Data System (ADS)

    Kirose, Getachew; Phelan, Brian R.; Sherbondy, Kelly D.; Ranney, Kenneth I.; Koenig, Francois; Narayanan, Ram M.

    2014-05-01

    The Army Research Laboratory (ARL) is developing an indoor experimental facility to evaluate and assess airborne synthetic-aperture-radar-(SAR)-based detection capabilities. The rail-SAR is located in a multi-use facility that also provides a base for research and development in the area of autonomous robotic navigation. Radar explosive hazard detection is one key sensordevelopment area to be investigated at this indoor facility. In particular, the mostly wooden, multi-story building houses a two (2) story housing structure and an open area built over a large sandbox. The housing structure includes reconfigurable indoor walls which enable the realization of multiple See-Through-The-Wall (STTW) scenarios. The open sandbox, on the other hand, allows for surface and buried explosive hazard scenarios. The indoor facility is not rated for true explosive hazard materials so all targets will need to be inert and contain surrogate explosive fills. In this paper we discuss the current system status and describe data collection exercises conducted using canonical targets and frequencies that may be of interest to designers of ultra-wideband (UWB) airborne, ground penetrating SAR systems. A bi-static antenna configuration will be used to investigate the effects of varying airborne SAR parameters such as depression angle, bandwidth, and integration angle, for various target types and deployment scenarios. Canonical targets data were used to evaluate overall facility capabilities and limitations. These data is analyzed and summarized for future evaluations. Finally, processing techniques for dealing with RF multi-path and RFI due to operating inside the indoor facility are described in detail. Discussion of this facility and its capabilities and limitations will provide the explosive hazard community with a great airborne platform asset for sensor to target assessment.

  4. New configuration of guided-wave electro-optic correlator for synthetic-aperture radar applications

    NASA Astrophysics Data System (ADS)

    Armenise, Mario N.; Passaro, Vittorio M. N.; Conese, Tiziana; Matteo, Anna M.

    1992-08-01

    In the last few years, a considerable effort in the optoelectronics research field has been spent for the development of a number of guided-wave active and passive components, such as laser diodes, electrooptic modulators, acoustooptic transducers, photodetectors, microlens array, and so on, for fabricating optical devices and circuits for signal processing and computing. The interest related to optical processors is particularly due to a lower power consumption, reduced size, cost and weight, and high throughput with respect to the corresponding electronic processors. In particular, synthetic aperture radar (SAR) applications are well suited for an optics-based processing technique implementation, because the synthesis of the object image, performed by correlating the received radar signal with a reference signal, is equivalent to the optical reconstruction of the Fresnel diffraction pattern of the same object, illuminated with coherent light. Guided-wave optical processors, including acousto-optic transducers and CCD cells, can be successfully applied to the reconstruction of two- dimensional images by using both spatial and time integration. In this paper, we present the theoretical investigation, design, and simulation of a new LiNbO3 guided-wave optical correlator suitable for real-time SAR applications. It is based on a complex interferometric structure, involving four aperiodic phase-reversal traveling wave modulators. The electrode structure is designed in order to reproduce the product signal between the received and reference voltages, which is then time-integrated by a suitable photodetector. The filtered signal coming from the detector is proportional to the final correlation function, which can be electronically registered and multiplexed on a two-dimensional matrix by sum-and-shift procedure. Thus, the processor performs the correlation function between the reference signal and the received signal when they are applied to laser diode and to the electrodes as driving voltage, respectively.

  5. Foldbelt exploration with synthetic aperture radar (SAR) in Papua New Guinea

    SciTech Connect

    Ellis, J.M.; Pruett, F.D.

    1987-05-01

    Synthetic aperture radar (SAR) is being successfully used within the southern fold and thrust belt of Papua New Guinea to map surface structure and stratigraphy and to help plan a hydrocarbon exploration program. The airborne SAR imagery, along with other surface data, is used as a primary exploration tool because acquisition of acceptable seismic data is extremely costly due to extensive outcrops of Tertiary Darai Limestone which develops rugged karst topography. Most anticlines in the licenses are capped with this deeply karstified limestone. The region is ideally suited to geologic analysis using remote sensing technology. The area is seldom cloud free and is covered with tropical rain forest, and geologic field studies are limited. The widespread karst terrain is exceedingly dangerous, if not impossible, to traverse on the ground. SAR is used to guide ongoing field work, modeling of subsurface structure, and selection of well locations. SAR provides their explorationists with an excellent data base because (1) structure is enhanced with low illumination, (2) resolution is 6 x 12 m, (3) digital reprocessing is possible, (4) clouds are penetrated by the SAR, and (5) the survey was designed for stereoscopic photogeology. Landsat images and vertical aerial photographs complement SAR but provide subdued structural information because of minimal shadowing (due to high sun angles) and the jungle cover. SAR imagery reveals large-scale mass wasting that has led to a reevaluation of previously acquired field data. Lithologies can be recognized by textural and tonal changes on the SAR images despite near-continuous canopy of jungle. Reprocessing and contrast stretching of the digital radar imagery provide additional geologic information.

  6. Removal of systematic seasonal atmospheric signal from interferometric synthetic aperture radar ground deformation time series

    NASA Astrophysics Data System (ADS)

    Samsonov, Sergey V.; Trishchenko, Alexander P.; Tiampo, Kristy; González, Pablo J.; Zhang, Yu; Fernández, José

    2014-09-01

    Applying the Multidimensional Small Baseline Subset interferometric synthetic aperture radar algorithm to about 1500 Envisat and RADARSAT-2 interferograms spanning 2003-2013, we computed time series of ground deformation over Naples Bay Area in Italy. Two active volcanoes, Vesuvius and Campi Flegrei, are located in this area in close proximity to the densely populated city of Naples. For the first time, and with remarkable clarity, we observed decade-long elevation-dependent seasonal oscillations of the vertical displacement component with a peak-to-peak amplitude of up to 3.0 cm, substantially larger than the long-term deformation rate (<0.6 cm/yr). Analysis, utilizing surface weather and radiosonde data, linked observed oscillations with seasonal fluctuations of water vapor, air pressure, and temperature in the lower troposphere. The modeled correction is in a good agreement with observed results. The mean, absolute, and RMS differences are 0.014 cm, 0.073 cm, and 0.087 cm, respectively. Atmospherically corrected time series confirmed continuing subsidence at Vesuvius previously observed by geodetic techniques.

  7. Synthetic aperture radar imagery of airports and surrounding areas: Philadelphia Airport

    NASA Technical Reports Server (NTRS)

    Onstott, Robert G.; Gineris, Denise J.

    1990-01-01

    The statistical description of ground clutter at an airport and in the surrounding area is addressed. These data are being utilized in a program to detect microbursts. Synthetic Aperture Radar (SAR) data were collected at the Philadelphia Airport. These data and the results of the clutter study are described. This 13 km x 10 km scene was imaged at 9.38 GHz and HH-polarization and contained airport grounds and facilities (6 percent), industrial (14 percent), residential (14 percent), fields (10 percent), forest (8 percent), and water (33 percent). Incidence angles ranged from 40 to 84 deg. Even at the smallest incidence angles, the distributed targets such as forest, fields, water, and residential rarely had mean scattering coefficients greater than -10 dB. Eighty-seven percent of the image had scattering coefficients less than -17.5 dB. About 1 percent of the scattering coefficients exceeded 0 dB, with about 0.1 percent above 10 dB. Sources which produced the largest cross sections were largely confined to the airport grounds and areas highly industrialized. The largest cross sections were produced by observing broadside large buildings surrounded by smooth surfaces.

  8. Synthetic Aperture Radar Imagery of Airports and Surrounding Areas: Denver Stapleton International Airport

    NASA Technical Reports Server (NTRS)

    Onstott, Robert G.; Gineris, Denise J.

    1990-01-01

    This is the third in a series of three reports which address the statistical description of ground clutter at an airport and in the surrounding area. These data are being utilized in a program to detect microbursts. Synthetic aperture radar (SAR) data were collected at the Denver Stapleton Airport using a set of parameters which closely match those which are anticipated to be utilized by an aircraft on approach to an airport. These data and the results of the clutter study are described. Scenes of 13 x 10 km were imaged at 9.38 GHz and HH-, VV-, and HV-polarizations, and contain airport grounds and facilities (up to 14 percent), cultural areas (more than 50 percent), and rural areas (up to 6 percent). Incidence angles range from 40 to 84 deg. At the largest depression angles the distributed targets, such as forest, fields, water, and residential, rarely had mean scattering coefficients greater than -10 dB. From 30 to 80 percent of an image had scattering coefficients less than -20 dB. About 1 to 10 percent of the scattering coefficients exceeded 0 dB, and from 0 to 1 percent above 10 dB. In examining the average backscatter coefficients at large angles, the clutter types cluster according to the following groups: (1) terminals (-3 dB), (2) city and industrial (-7 dB), (3) warehouse (-10 dB), (4) urban and residential (-14 dB), and (5) grass (-24 dB).

  9. Operational and research use of spaceborne synthetic aperture radar at NOAA/NESDIS

    NASA Astrophysics Data System (ADS)

    Clemente-Coln, P.; Pichel, W. G.; Friedman, K. S.; Li, X.; Arabini, E.; Tseng, W.; Bertoia, C. A.; Monaldo, F. M.; Wackerman, C. C.

    2003-04-01

    RADARSAT-1 synthetic aperture radar (SAR) satellite data acquired under a U.S-Canada agreement have proven very beneficial to National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite, Data, and Information Service (NESDIS) and to the National Ice Center (NIC) - a multi-agency operational center representing the Department of Defense (Navy), the Department of Commerce (NOAA), and the Department of Transportation (Coast Guard) - in support of a variety of environmental research and monitoring activities. RADARSAT-1 SAR imagery is the main data stream used by NIC to produce sea ice analysis products operationally. A project to demonstrate additional near real-time SAR applications in Alaska began in the fall of 1999. The Alaska SAR Demonstration (AKDEMO) has provided and infrastructure to validate and test prototype SAR products that respond to critical needs in the region not satisfied with other observational data available. Other projects supported by RADARSAT-1 SAR data include the StormWatch Project lead by The Johns Hopkins University Applied Physics Laboratory; the HurricaneWatch Project conducted in partnership with the Canada Centre for Remote Sensing (CCRS), the Canadian Space Agency (CSA), and the NOAA Atlantic Oceanographic and Metoeorological Laboratory (AOML); as well as several coastal dynamics, pollution and flooding monitoring and research activities. A review and highlights of our SAR experience along with future plans to utilize operationally data from newly available and future satellite missions are presented in this paper.

  10. Multibaseline polarimetric synthetic aperture radar tomography of forested areas using wavelet-based distribution compressive sensing

    NASA Astrophysics Data System (ADS)

    Liang, Lei; Li, Xinwu; Gao, Xizhang; Guo, Huadong

    2015-01-01

    The three-dimensional (3-D) structure of forests, especially the vertical structure, is an important parameter of forest ecosystem modeling for monitoring ecological change. Synthetic aperture radar tomography (TomoSAR) provides scene reflectivity estimation of vegetation along elevation coordinates. Due to the advantages of super-resolution imaging and a small number of measurements, distribution compressive sensing (DCS) inversion techniques for polarimetric SAR tomography were successfully developed and applied. This paper addresses the 3-D imaging of forested areas based on the framework of DCS using fully polarimetric (FP) multibaseline SAR interferometric (MB-InSAR) tomography at the P-band. A new DCS-based FP TomoSAR method is proposed: a new wavelet-based distributed compressive sensing FP TomoSAR method (FP-WDCS TomoSAR method). The method takes advantage of the joint sparsity between polarimetric channel signals in the wavelet domain to jointly inverse the reflectivity profiles in each channel. The method not only allows high accuracy and super-resolution imaging with a low number of acquisitions, but can also obtain the polarization information of the vertical structure of forested areas. The effectiveness of the techniques for polarimetric SAR tomography is demonstrated using FP P-band airborne datasets acquired by the ONERA SETHI airborne system over a test site in Paracou, French Guiana.

  11. On the detection of crevasses in glacial ice with synthetic-aperture radar.

    SciTech Connect

    Brock, Billy C.

    2010-02-01

    The intent of this study is to provide an analysis of the scattering from a crevasse in Antarctic ice, utilizing a physics-based model for the scattering process. Of primary interest is a crevasse covered with a snow bridge, which makes the crevasse undetectable in visible-light images. It is demonstrated that a crevasse covered with a snow bridge can be visible in synthetic-aperture-radar (SAR) images. The model of the crevasse and snow bridge incorporates a complex dielectric permittivity model for dry snow and ice that takes into account the density profile of the glacier. The surface structure is based on a fractal model that can produce sastrugi-like features found on the surface of Antarctic glaciers. Simulated phase histories, computed with the Shooting and Bouncing Ray (SBR) method, are processed into SAR images. The viability of the SBR method for predicting scattering from a crevasse covered with a snow bridge is demonstrated. Some suggestions for improving the model are given.

  12. Method and apparatus for reducing range ambiguity in synthetic aperture radar

    DOEpatents

    Kare, Jordin T.

    1999-10-26

    A modified Synthetic Aperture Radar (SAR) system with reduced sensitivity to range ambiguities, and which uses secondary receiver channels to detect the range ambiguous signals and subtract them from the signal received by the main channel. Both desired and range ambiguous signals are detected by a main receiver and by one or more identical secondary receivers. All receivers are connected to a common antenna with two or more feed systems offset in elevation (e.g., a reflector antenna with multiple feed horns or a phased array with multiple phase shift networks. The secondary receiver output(s) is (are) then subtracted from the main receiver output in such a way as to cancel the ambiguous signals while only slightly attenuating the desired signal and slightly increasing the noise in the main channel, and thus does not significantly affect the desired signal. This subtraction may be done in real time, or the outputs of the receivers may be recorded separately and combined during signal processing.

  13. Land subsidence detection using synthetic aperture radar (SAR) in Sidoarjo Mudflow area

    NASA Astrophysics Data System (ADS)

    Yulyta, Sendy Ayu; Taufik, Muhammad; Hayati, Noorlaila

    2016-05-01

    According to BPLS (Badan Penanggulangan Lumpur Sidoarjo) which is the Sidoarjo Mudflow Management Agency, land subsidence occurred in Porong, Sidoarjo was caused by the rocks bearing capacity decreasing which led by the mud outpouring since 2006. The subsidence varies in many ways depends on the radius of location from the mud flow center point and the geological structure. One of the most efficient technologies to monitor this multi temporal phenomenon is using the Synthetic Aperture Radar (SAR) as an applicative Spatial Geodesy. This study used 4 (four) times series L-Band ALOS PALSAR from 2008 to 2011 Fine Beam Single data (February 2008, January 2009 and February 2010 and January 2011) which then processed by the Differential SAR Interferometry (DInSAR) method to obtain the deformation vector at a radius of 1.5 km from the center of mudflow. The result showed that there was a significant subsidence which annually occurred on southern and western area of Sidoarjo mud flow. The deformation vector that occurred in the year 2008-2011 was up to 20 cm/year or 0.05 cm/day. For verification purpose, we also compared the result obtained from the SAR detection with the data measured by Global Position System (GPS) and some deformation monitoring results obtained from another researchs. The comparison showed a correlation that the subsidence occurred on the same location.

  14. Reducing scalloping in synthetic aperture radar images using a composite image transform

    NASA Astrophysics Data System (ADS)

    Landmark, Knut; Solberg, Anne H. S.

    2015-10-01

    In burst mode SAR imaging, echo intensity depends on the target's azimuth position in the antenna pattern. As a result, an amplitude modulation known as scalloping may appear, particularly in ScanSAR images of ocean areas. A denoising method, recently developed for multibeam bathymetry, can be used to reduce residual scalloping in ScanSAR images. The algorithm is analogous to a band-stop filter in the frequency domain. Here, the transform is the composition of an edge detection operator and a discrete Radon transform (DRT). The edge operator accentuates fine-scale intensity changes; the DRT focuses linear features, as each DRT component is the sum of pixel intensities along a linear graph. A descalloping filter is implemented in the DRT domain by suppressing the range direction. The restored image is obtained by applying the inverse composite transform. First, a rapidly converging iterative pseudo-inverse DRT is computed. The edge operator is a spatial filter based on a discrete approximation of the Laplace operator, but modified to make the operator invertible. The method was tested on ocean scene ScanSAR images from the Envisat Advanced Synthetic Aperture Radar. The scalloping effect was significantly reduced, with no apparent distortion or smoothing of physical features.

  15. Elastic rebound following the Kocaeli earthquake, Turkey, recorded using synthetic aperture radar interferometry

    USGS Publications Warehouse

    Mayer, Larry; Lu, Zhong

    2001-01-01

    A basic model incorporating satellite synthetic aperture radar (SAR) interferometry of the fault rupture zone that formed during the Kocaeli earthquake of August 17, 1999, documents the elastic rebound that resulted from the concomitant elastic strain release along the North Anatolian fault. For pure strike-slip faults, the elastic rebound function derived from SAR interferometry is directly invertible from the distribution of elastic strain on the fault at criticality, just before the critical shear stress was exceeded and the fault ruptured. The Kocaeli earthquake, which was accompanied by as much as ∼5 m of surface displacement, distributed strain ∼110 km around the fault prior to faulting, although most of it was concentrated in a narrower and asymmetric 10-km-wide zone on either side of the fault. The use of SAR interferometry to document the distribution of elastic strain at the critical condition for faulting is clearly a valuable tool, both for scientific investigation and for the effective management of earthquake hazard.

  16. Analysis of data acquired by synthetic aperture radar over Dade County, Florida, and Acadia Parish, Louisiana

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1983-01-01

    Results of digital processing of airborne X-band synthetic aperture radar (SAR) data acquired over Dade County, Florida, and Acadia Parish, Louisiana are presented. The goal was to investigate the utility of SAR data for land cover mapping and area estimation under the AgRISTARS Domestic Crops and Land Cover Project. In the case of the Acadia Paris study area, LANDSAT multispectral scanner (MSS) data were also used to form a combined SAR and MSS data set. The results of accuracy evaluation for the SAR, MSS, and SAR/MSS data using supervised classification show that the combined SAR/MSS data set results in an improved classification accuracy of the five land cover classes as compared with SAR-only and MSS-only data sets. In the case of the Dade County study area, the results indicate that both HH and VV polarization data are highly responsive to the row orientation of the row crop but not to the specific vegetation which forms the row structure. On the other hand, the HV polarization data are relatively insensitive to the orientation of row crop. Therefore, the HV polarization data may be used to discriminate the specific vegetation that forms the row structure.

  17. Potential use of hybrid synthetic aperture radar polarimetry in Earth surface monitoring

    NASA Astrophysics Data System (ADS)

    Trisasongko, Bambang H.

    2015-09-01

    To observe delicate Earth surface continuously, satellite-based monitoring system is required. Especially in tropical region, Synthetic Aperture Radar (SAR) is necessitated considering its ability to penetrate cloud and other atmospheric attenuations. Recent fully polarimetric SAR has been exploited. Nonetheless, this mode of imaging consumes higher amount of energy, which is one of the main issues in satellite-based platform. In this paper, a study exploiting hybrid (also known as compact) polarization is presented. Comparison to fully polarimetric mode of SAR is made using polarimetric decomposition. This research indicates that single signal transmission in hybrid polarization cannot fully replace fully-polarized mode. This suggests that hybrid polarization should be limitedly applied to geo-biophysical applications such as biomass or soil moisture estimation. However, for general land cover discrimination and monitoring, hybrid polarimetry is fairly useful. Analysis of transformed divergence on decomposition parameters entropy, alpha angle and anisotropy shows that hybrid polarization successfully discriminates major land cover types with some degrees of confidence.

  18. On the relationship between the generalized likelihood ratio test and backprojection for synthetic aperture radar imaging

    NASA Astrophysics Data System (ADS)

    Voccola, K.; Yazici, B.; Ferrara, M.; Cheney, M.

    2009-05-01

    In synthetic aperture radar (SAR) imaging, a scene of interest is illuminated by electromagnetic waves. The aim is to reconstruct an image of the scene from the measurement of the scattered waves using airborne antenna(s). There are many imaging systems which are built upon this notion such as mono-static SAR, bi-static SAR, and hitchhiker SAR. For these modalities, there are analytic reconstruction algorithms based on backprojection. Backprojection-based algorithms have the advantage of putting the visible edges of the scene at the right location and orientation in the reconstructed images. On the other hand, there is also a SAR imaging method based on the generalized likelihood-ratio test (GLRT). In particular we consider the problem of detecting a target at an unknown location. In the GLRT, the presence of a target in the scene is determined based on the likelihood-ratio test. Since the location of the target is not known, the GLRT test statistic is calculated for each position in the scene and the location corresponding to the maximum test statistic indicates the location of a potential target. In this paper, we show that the backprojection-based analytic reconstruction methods include as a special case the GLRT method. We show that the GLRT test statistic is related to the reflectivity of the scene when a backprojection-based reconstruction algorithm is used.

  19. Polarimetric synthetic aperture radar image unsupervised classification method based on artificial immune system

    NASA Astrophysics Data System (ADS)

    Jie, Yu; Gang, Wang; Teng, Zhu; Xiaojuan, Li; Qin, Yan

    2014-01-01

    An unsupervised classification method based on the H/α classifier and artificial immune system (AIS) is proposed to overcome the inefficiencies that arise when traditional classification methods deal with polarimetric synthetic aperture radar (PolSAR) data having large numbers of overlapping pixels and excess polarimetric information. The method is composed of two steps. First, Cloude-Pottier decomposition is used to obtain the entropy H and the scattering angle α. The classification result based on the H/α plane is used to initialize the AIS algorithm. Second, to obtain accurate results, the AIS clonal selection algorithm is used to perform an iterative calculation. As a self-organizing, self-recognizing, and self-optimizing algorithm, the AIS is able to obtain a global optimal solution and better classification results by making use of both the scattering mechanism of ground features and polarimetric scattering characteristics. The effectiveness and feasibility of this method are demonstrated by experiments using a NASA-JPL PolSAR image and a high-resolution PolSAR image of Lingshui autonomous county in Hainan Province.

  20. Determining snow depth using Ku-band interferometric synthetic aperture radar (InSAR)

    NASA Astrophysics Data System (ADS)

    Evans, J. R.; Kruse, F. A.; Bickel, D. L.; Dunkel, Ralf

    2014-05-01

    Monitoring seasonal snow accumulation is important for evaluation of snow models, for short- and long-term snow cover monitoring, and for both military and civilian activities in cold climates. Improved spatial analysis of snow depth and volume can help decision makers plan for future events and mitigate risk. Current snow depth measurement methods fall short of operational requirements. This research explored a new approach for determining snow depth using Ku-band multi-pass (monostatic) airborne interferometric synthetic aperture radar (InSAR). A perturbation method that isolated and compared high frequency terrain phase to elevation was used to generate Snow-Off and Snow-On DEMs from the InSAR phase data. Differencing the InSAR DEMs determined elevation change caused by accumulated snow. Comparison of InSAR snow depths to manual snow depth measurements indicated average InSAR snow depth errors of -8cm, 95cm, -49cm, 176cm, 87cm, and 42cm for six SAR pairs. The source of these errors appears to be mostly related to uncorrected slope and tilt in fitted low frequency planes. Results show that this technique has promise but accuracy could be substantially improved by the use of bistatic SAR systems, which would allow for more stable and measurable interferometric baselines.

  1. An approach for detecting changes related to natural disasters using Synthetic Aperture Radar data

    NASA Astrophysics Data System (ADS)

    Milisavljevic, N.; Closson, D.; Holecz, F.; Collivignarelli, F.; Pasquali, P.

    2015-04-01

    Land-cover changes occur naturally in a progressive and gradual way, but they may happen rapidly and abruptly sometimes. Very high resolution remote sensed data acquired at different time intervals can help in analyzing the rate of changes and the causal factors. In this paper, we present an approach for detecting changes related to disasters such as an earthquake and for mapping of the impact zones. The approach is based on the pieces of information coming from SAR (Synthetic Aperture Radar) and on their combination. The case study is the 22 February 2011 Christchurch earthquake. The identification of damaged or destroyed buildings using SAR data is a challenging task. The approach proposed here consists in finding amplitude changes as well as coherence changes before and after the earthquake and then combining these changes in order to obtain richer and more robust information on the origin of various types of changes possibly induced by an earthquake. This approach does not need any specific knowledge source about the terrain, but if such sources are present, they can be easily integrated in the method as more specific descriptions of the possible classes. A special task in our approach is to develop a scheme that translates the obtained combinations of changes into ground information. Several algorithms are developed and validated using optical remote sensing images of the city two days after the earthquake, as well as our own ground-truth data. The obtained validation results show that the proposed approach is promising.

  2. A fast level set method for synthetic aperture radar ocean image segmentation.

    PubMed

    Huang, Xiaoxia; Huang, Bo; Li, Hongga

    2009-01-01

    Segmentation of high noise imagery like Synthetic Aperture Radar (SAR) images is still one of the most challenging tasks in image processing. While level set, a novel approach based on the analysis of the motion of an interface, can be used to address this challenge, the cell-based iterations may make the process of image segmentation remarkably slow, especially for large-size images. For this reason fast level set algorithms such as narrow band and fast marching have been attempted. Built upon these, this paper presents an improved fast level set method for SAR ocean image segmentation. This competent method is dependent on both the intensity driven speed and curvature flow that result in a stable and smooth boundary. Notably, it is optimized to track moving interfaces for keeping up with the point-wise boundary propagation using a single list and a method of fast up-wind scheme iteration. The list facilitates efficient insertion and deletion of pixels on the propagation front. Meanwhile, the local up-wind scheme is used to update the motion of the curvature front instead of solving partial differential equations. Experiments have been carried out on extraction of surface slick features from ERS-2 SAR images to substantiate the efficacy of the proposed fast level set method. PMID:22399940

  3. A neural network for enhancing boundaries and surfaces in synthetic aperture radar images.

    PubMed

    Mingolla, Ennio; Ross, William; Grossberg, Stephen

    1999-04-01

    A neural network system for boundary segmentation and surface representation, inspired by a new local-circuit model of visual processing in the cerebral cortex, is used to enhance images of range data gathered by a synthetic aperture radar (SAR) sensor. Boundary segmentation is accomplished by an improved Boundary Contour System (BCS) model which completes coherent boundaries that retain their sensitivity to image contrasts and locations. A Feature Contour System (FCS) model compensates for local contrast variations and uses the compensated signals to diffusively fill-in surface regions within the BCS boundaries. Image noise pixels that are not supported by BCS boundaries are hereby eliminated. More generally, BCS/FCS processing normalizes input dynamic range, reduces noise, and enhances contrasts between surface regions. BCS/FCS processing hereby makes structures such as motor vehicles, roads, and buildings more salient to human observers than in original imagery. The new BCS model improves image enhancement with significant reductions in processing time and complexity over previous BCS applications. The new system also outperforms several established techniques for image enhancement. PMID:12662691

  4. Digital processing considerations for extraction of ocean wave image spectra from raw synthetic aperture radar data

    NASA Technical Reports Server (NTRS)

    Lahaie, I. J.; Dias, A. R.; Darling, G. D.

    1984-01-01

    The digital processing requirements of several algorithms for extracting the spectrum of a detected synthetic aperture radar (SAR) image from the raw SAR data are described and compared. The most efficient algorithms for image spectrum extraction from raw SAR data appear to be those containing an intermediate image formation step. It is shown that a recently developed compact formulation of the image spectrum in terms of the raw data is computationally inefficient when evaluated directly, in comparison with the classical method where matched-filter image formation is an intermediate result. It is also shown that a proposed indirect procedure for digitally implementing the same compact formulation is somewhat more efficient than the classical matched-filtering approach. However, this indirect procedure includes the image formation process as part of the total algorithm. Indeed, the computational savings afforded by the indirect implementation are identical to those obtained in SAR image formation processing when the matched-filtering algorithm is replaced by the well-known 'dechirp-Fourier transform' technique. Furthermore, corrections to account for slant-to-ground range conversion, spherical earth, etc., are often best implemented in the image domain, making intermediate image formation a valuable processing feature.

  5. Observation of sea-ice dynamics using synthetic aperture radar images: Automated analysis

    NASA Technical Reports Server (NTRS)

    Vesecky, John F.; Samadani, Ramin; Smith, Martha P.; Daida, Jason M.; Bracewell, Ronald N.

    1988-01-01

    The European Space Agency's ERS-1 satellite, as well as others planned to follow, is expected to carry synthetic-aperture radars (SARs) over the polar regions beginning in 1989. A key component in utilization of these SAR data is an automated scheme for extracting the sea-ice velocity field from a time sequence of SAR images of the same geographical region. Two techniques for automated sea-ice tracking, image pyramid area correlation (hierarchical correlation) and feature tracking, are described. Each technique is applied to a pair of Seasat SAR sea-ice images. The results compare well with each other and with manually tracked estimates of the ice velocity. The advantages and disadvantages of these automated methods are pointed out. Using these ice velocity field estimates it is possible to construct one sea-ice image from the other member of the pair. Comparing the reconstructed image with the observed image, errors in the estimated velocity field can be recognized and a useful probable error display created automatically to accompany ice velocity estimates. It is suggested that this error display may be useful in segmenting the sea ice observed into regions that move as rigid plates of significant ice velocity shear and distortion.

  6. Enhanced Feature Based Mosaicing Technique for Visually and Geometrically Degraded Airborne Synthetic Aperture Radar Images

    NASA Astrophysics Data System (ADS)

    Manikandan, S.; Vardhini, J. P.

    2015-11-01

    In airborne synthetic aperture radar (SAR), there was a major problem encountered in the area of image mosaic in the absence of platform information and sensor information (geocoding), when SAR is applied in large-scale scene and the platform faces large changes. In order to enhance real-time performance and robustness of image mosaic, enhancement based Speeded-Up Robust Features (SURF) mosaic method for airborne SAR is proposed in this paper. SURF is a novel scale-invariant and rotation-invariant feature. It is perfect in its high computation, speed and robustness. In this paper, When the SAR image is acquired, initially the image is enhanced by using local statistic techniques and SURF is applied for SAR image matching accord to its characteristic, and then acquires its invariant feature for matching. In the process of image matching, the nearest neighbor rule for initial matching is used, and the wrong points of the matches are removed through RANSAC fitting algorithm. The proposed algorithm is implemented in different SAR images with difference in scale change, rotation change and noise. The proposed algorithm is compared with other existing algorithms and the quantitative and qualitative measures are calculated and tabulated. The proposed algorithm is robust to changes and the threshold is varied accordingly to increase the matching rate more than 95 %.

  7. Traces of pyroclastic flows and lahars detected with satellite synthetic aperture radars

    NASA Astrophysics Data System (ADS)

    Nishida, K.; Terunuma, T.; Amada, T.; Sato, I.; Urai, M.

    2001-05-01

    Rapid detection of traces of pyroclastic flow and lahar is important for disaster prevention and mitigation in a volcanic area. For this purpose, we developed some methods by using the L-band synthetic aperture radar (SAR) on JERS-1 satellite. The following three methods were tested and evaluated against actual volcanic events in Mt. Unzen 1991-1995 eruption in Japan: a) Back-scatter analysis, b) coherence analysis, and c) SAR interferometry. The method b) with coherence analysis showed the highest capability of detection of pyroclastic flows and lahars in the following two manners: Case 1) A pair of SAR images taken both before and after the event gives particularly low coherence over the trace of the flows. Case 2) A pair of SAR images taken just after the event gives particularly high coherence over the trace of the flows than other slopes. The change of land surface status realizes the Case 1 with low coherence, whereas the bare surface of the sediments contributes to the Case 2 with high coherence.

  8. Characterizing geolocation ambiguity responses in synthetic aperture radar: ground moving target indication

    NASA Astrophysics Data System (ADS)

    Holston, Matthew E.; Minardi, Michael J.; Temple, Michael A.; Saville, Michael A.

    2007-04-01

    Single-channel synthetic aperture radar (SAR) can provide high quality, focused images of moving targets by utilizing advanced SAR-GMTI techniques that focus all constant velocity targets into a three-dimensional space indexed by range, cross-range and cross-range velocity. However, an inherent geolocation ambiguity exists in that multiple, distinct moving targets may posses identical range versus time responses relative to a constant velocity collection platform. Although these targets are uniquely located within a four-dimensional space (x-position, y-position, x-velocity, and y-velocity), their responses are focused and mapped to the same three-dimensional position in the SAR-GMTI image cube. Previous research has shown that circular SAR (CSAR) collection geometry is one way to break this ambiguity and creates a four-dimensional detection space. This research determines the target resolution available in the detection space as a function of different collection parameters. A metric is introduced to relate the resolvability of multiple target responses for various parametric combinations, i.e., changes in key collection parameters such as integration time, slant range, look angle, and carrier frequency.

  9. Research on synthetic aperture radar imaging technology of one-dimensional layered rough surfaces

    NASA Astrophysics Data System (ADS)

    Ji, Wei-Jie; Tong, Chuang-Ming

    2013-02-01

    A quick and exact imaging method for one-dimensional layered rough surfaces is proposed in this paper to study the scattering characteristics of a layered medium that exists widely in nature. The boundary integral equations of layered rough surfaces are solved by using the propagation-inside-layer expansion combined with the forward and backward spectral acceleration method (PILE+FB-SA), and the back scattering data are obtained. Then, a conventional synthetic aperture radar (SAR) imaging procedure called back projection method is used to generate a two-dimensional (2D) image of the layered rough surfaces. Combined with the relative dielectric permittivity of realistic soil, the random rough surfaces with Gauss spectrum are used to simulate the layered medium with rough interfaces. Since the back scattering data are computed by using the fast numerical method, this method can be used to study layered rough surfaces with any parameter, which has a great application value in the detection and remote sensing areas.

  10. Parameter estimation and imaging of moving targets in bistatic synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Li, Yu; Huang, Puming; Yang, Zhimei; Lin, Chenchen

    2016-01-01

    In high-resolution bistatic synthetic aperture radar (SAR) systems, parameter estimation is essential to moving target imaging quality. However, precise parameters are difficult to obtain without priori information due to the relative along-track and across-track velocities between the moving target and platforms that change with time. A parameter estimation and imaging approach for moving targets is proposed. First, slant range and relative velocities expression are deduced based on the geometry of bistatic SAR model with one stationary configuration. Then, range curvature term are compensated skillfully by fitting the range-compressed curve in two-dimensional time domain, meanwhile, the initial estimated range walk slope can be achieved. Finally, precise Doppler centroid is estimated through searching for the maximum contrast with folding search algorithm, which is giving consideration to both searching precision and computational complexity. Thus, the proposed algorithm provides an effective way for parameter estimation and imaging of moving target without prior information and interpolation operation. Experimental results show the effectiveness of the proposed method.

  11. Detection of Built-Up Areas Using Polarimetric Synthetic Aperture Radar Data and Hyperspectral Image

    NASA Astrophysics Data System (ADS)

    Bordbari, R.; Maghsoudi, Y.; Salehi, M.

    2015-12-01

    Polarimetric synthetic aperture radar (POLSAR) is an advantageous data for information extraction about objects and structures by using the wave scattering and polarization properties. Hyperspectral remote sensing exploits the fact that all materials reflect, absorb, and emit electromagnetic energy, at specific wavelengths, in distinctive patterns related to their molecular composition. As a result of their fine spectral resolution, Hyperspectral image (HIS) sensors provide a significant amount of information about the physical and chemical composition of the materials occupying the pixel surface. In target detection applications, the main objective is to search the pixels of an HSI data cube for the presence of a specific material (target). In this research, a hierarchical constrained energy minimization (hCEM) method using 5 different adjusting parameters has been used for target detection from hyperspectral data. Furthermore, to detect the built-up areas from POLSAR data, building objects discriminated from surrounding natural media presented on the scene using Freeman polarimetric target decomposition (PTD) and the correlation coefficient between co-pol and cross-pol channels. Also, target detection method has been implemented based on the different polarization basis for using the more information. Finally a majority voting method has been used for fusing the target maps. The polarimetric image C-band SAR data acquired by Radarsat-2, over San Francisco Bay area was used for the evaluation of the proposed method.

  12. Synthetic aperture radar image formation from compressed data using a new computation technique

    NASA Astrophysics Data System (ADS)

    Chabries, Douglas M.; Christiansen, Richard W.; Jackson, Philip L.; Read, Christopher J.; Arnold, David V.

    1988-10-01

    A convolution technique is proposed that allows direct reconstruction of the processed synthetic-aperture radar (SAR) image from the digitally-sampled, block-encoded raw data. This computational compression technique reduces the number of arithmetic operations from that required by fast Fourier transform (FFT) convolution for SAR processing. SAR phase histories are block encoded and directly processed into an image where only arithmetic additions are required for the processing. For SAR data previously block encoded, the processing time is reduced by a factor of 100 or more. A speedup of three times over SAR processing by FFT convolution has been demonstrated when both computation of the block encoding and subsequent direct processing are included in the time. SAR image quality measurements for a method of block encoding called vector quantization at compression ratios ranging from 5:1 to 50:1 show image degradation proportional to the compression ratio. For a 5:1 compression radio, image quality measurements show minimal degradation.

  13. Two new methods based on contourlet transform for despeckling synthetic aperture radar images

    NASA Astrophysics Data System (ADS)

    Kiani, Mohammad; Ghofrani, Sedigheh

    2014-01-01

    We propose two methods for speckle suppression of synthetic aperture radar (SAR) images. The first method is based on Bayesian shrinkage and is a thresholding technique. The main problem of applying Bayesian shrinkage in a transformed domain, such as contourlet transform (CT), is finding the optimum threshold value. According to our experimental results, contourlet coefficients are affected by noise differently. It means that some contourlet coefficients belong to the specific sub-bands that are more robust against noise. We use this newfound property to determine the optimum threshold value and to develop our proposed method, which is named the weighted Bayesian shrinkage in contourlet domain. The second method, named the NSCT-GΓD, is a model-based approach using a two-sided generalized Gamma distribution (GΓD) to model the statistics of nonsubsampled contourlet transform (NSCT) coefficients. We use the Bayesian maximum a posteriori estimator to find NSCT despeckled coefficients. Experimental results carried out on both artificially speckled images and the true SAR images show that our two proposed methods outperform other approaches via two point of views, speckle noise reduction and image quality preservation.

  14. Spatially variant interference suppression method based on superresolution algorithm for synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Suwa, Kei; Wakayama, Toshio

    2011-06-01

    Synthetic Aperture Radar (SAR) often suffers from interference signal from various radio sources. In general, notch filters or band elimination filters have been utilized to eliminate such interference signal; however, if the bandwidth of the interference signal is relatively wide, the gap in the spectrum caused by the band elimination filter could significantly degrade the original image. We propose an algorithm to suppress relatively wide bandwidth interference while maintaining the image quality. In the algorithm, spatially variant interference suppression filter is generated based on the signal of interference free band, then the filter is applied to the interference contaminated image. Unlike the band elimination filter, the spatially variant interference suppression filter preserves the signal component within the interference contaminated band; therefore, the image distortion caused by the spectrum gap can be largely eliminated. The algorithm has been tested with a simulated interference contaminated image generated from the real 10cm resolution airborne Ku band SAR image and a TerraSAR-X image. It has been shown that while conventional band elimination filter would degrade the image quality, the image quality of the interference suppressed image obtained by the proposed algorithm is satisfactory.

  15. Synthetic Aperture Radar (sar) and Optical Imagery Data Fusion: Crop Yield Analysis in Southeast Asia

    NASA Astrophysics Data System (ADS)

    Parks, S. M.

    2012-08-01

    With the expanding energy crisis and rising food prices, crop yield analysis in Southeast Asia is an increasingly important topic in this region. Rice is the most important food crop in Southeast Asia and the ability to accurately predict crop yields during a growing season is useful for decision-makers, aid providers, and commercial trade organizations. The use of optical satellite image data by itself is difficult due to the almost constant cloud in many parts of Southeast Asia. However, Synthetic Aperture Radar (SAR), or SAR data, which can image the Earth's surface through cloud cover, is suitable for many agricultural purposes, such as the detection of rice fields, and the identification of different crop species. Crop yield analysis is difficult in this region due to many factors. Rice cropping systems are often characterized by the type of rice planted, the size of rice field, the sowing dates for different fields, different types of rice cropping systems from one area to another, as well as cultural practices such as sowing and transplanting. This paper will discuss the use of SAR data fused with optical imagery to improve the ability to perform crop yield analysis on rice crops in Southeast Asia.

  16. High-performance synthetic aperture radar image formation on commodity multicore architectures

    NASA Astrophysics Data System (ADS)

    McFarlin, Daniel S.; Franchetti, Franz; Püschel, Markus; Moura, José M. F.

    2009-05-01

    Synthetic Aperture Radar (SAR) image processing platforms have to process increasingly large datasets under and hard real-time deadlines. Upgrading these platforms is expensive. An attractive solution to this problem is to couple high performance, general-purpose Commercial-Off-The-Shelf (COTS) architectures such as IBM's Cell BE and Intel's Core with software implementations of SAR algorithms. While this approach provides great flexibility, achieving the requisite performance is difficult and time-consuming. The reason is the highly parallel nature and general complexity of modern COTS microarchitectures. To achieve the best performance, developers have to interweave of various complex optimizations including multithreading, the use of SIMD vector extensions, and careful tuning to the memory hierarchy. In this paper, we demonstrate the computer generation of high performance code for SAR implementations on Intel's multicore platforms based on the Spiral framework and system. The key is to express SAR and its building blocks in Spiral's formal domain-specific language to enable automatic vectorization, parallelization, and memory hierarchy tuning through rewriting at a high abstraction level and automatic exploration of choices. We show that Spiral produces code for the latest Intel quadcore platforms that surpasses competing hand-tuned implementations on the Cell Blade, an architecture with twice as many cores and three times the memory bandwidth. Specifically, we show an average performance of 39 Gigaflops/sec for 16-Megapixel and 100-Megapixel SAR images with runtimes of 0.56 and 3.76 seconds respectively.

  17. Poyang Lake wetland vegetation biomass inversion using polarimetric RADARSAT-2 synthetic aperture radar data

    NASA Astrophysics Data System (ADS)

    Shen, Guozhuang; Liao, Jingjuan; Guo, Huadong; Liu, Ju

    2015-01-01

    Poyang Lake is the largest freshwater lake in China and one of the most important wetlands in the world. Vegetation, an important component of wetland ecosystems, is one of the main sources of the carbon in the atmosphere. Biomass can quantify the contribution of wetland vegetation to carbon sinks and carbon sources. Synthetic aperture radar (SAR), which can operate in all day and weather conditions and penetrate vegetation to some extent, can be used to retrieve information about vegetation structure and the aboveground biomass. In this study, RADARSAT-2 polarimetric SAR data were used to retrieve aboveground vegetation biomass in the Poyang Lake wetland. Based on the canopy backscatter model, the vegetation backscatter characteristics in the C-band were studied, and a good relation between simulated backscatter and backscatter in the RADARSAT-2 imagery was achieved. Using the backscatter model, pairs of training data were built and used to train the back propagation artificial neural network. The biomass was retrieved using this ANN and compared with the field survey results. The root-mean-square error in the biomass estimation was 45.57 g/m2. This shows that the combination of the model and polarimetric decomposition components can efficiently improve the inversion precision.

  18. Synthetic aperture radar image of agricultural fields with surface drainage network: simulation and spatial information retreival

    NASA Astrophysics Data System (ADS)

    Meunier, Francois; Meunier, Jean; Cavayas, Francois

    2001-10-01

    We develop a 3-D model to simulate the synthetic aperture radar (SAR) image formation process of an undulated vegetation canopy such as corn grown in fields with large periodic drainage reliefs. We explain how the simulated SAR image of undulated vegetation medium is obtained by the convolution of a 2-D slice of the 3-D simulated SAR system point spread function [(PSF), emulating the SAR beam modeled by a cosine modulated Gaussian], with the 2-D projection of the observed undulated vegetation canopy (modeled with scatterers randomly distributed in 3-D undulated space) followed by the extraction of each look envelope, the summation of looks, and sampling in azimuthal and range directions. Our model is useful to study the parameters involved in the formation and the analysis of SAR images of undulated vegetation medium. Validation of simulations made with actual SAR images shows that undulated corn crop canopies are well characterized by the mean contrast of the backscattered amplitude, the shape parameter (alpha) of the K distribution, the coefficient of variation, and the autocorrelation function of the backscattered amplitude. These experiments also show that the discrimination of corn parcels with or without subsurface drainage and the monitoring of the corn plant height differential across the drainage ridge during the growing season are possible.

  19. Adaptive multiparameter spectral feature analysis for synthetic aperture radar target recognition

    NASA Astrophysics Data System (ADS)

    Zhang, Xiangrong; Jiao, Licheng; Zhou, Sisi; Zhou, Nan; Feng, Jie

    2012-08-01

    A feature extraction algorithm based on spectral clustering with adaptive multiparameters is proposed for synthetic aperture radar automatic target recognition (SAR-ATR). Spectral clustering has been widely applied in computer vision for its good performance. Meanwhile, the spectral mapping step in it has the property of feature space transformation. Spectral clustering based target feature extraction for SAR-ATR is constructed according to the framework of out-of-sample extensions in weighted kernel principal component analysis. To avoid the scaling parameter selection in spectral feature analysis (SFA) and eliminate the influence of scaling parameter on feature extraction performance as well, the multiple scaling parameters are calculated adaptively by local neighborhoods. Because the local statistics of the neighborhood of each point are taken into consideration, its performance is better than using only one fixed parameter. Based on the extracted features, target recognition is performed by the support vector machine for its good generalization capability. The experimental results show that the multiparameter SFA outperforms the principal component analysis, kernel principal component analysis and SFA with the selected scaling parameter for SAR target recognition in terms of recognition accuracy.

  20. Agricultural crop harvest progress monitoring by fully polarimetric synthetic aperture radar imagery

    NASA Astrophysics Data System (ADS)

    Yang, Hao; Zhao, Chunjiang; Yang, Guijun; Li, Zengyuan; Chen, Erxue; Yuan, Lin; Yang, Xiaodong; Xu, Xingang

    2015-01-01

    Dynamic mapping and monitoring of crop harvest on a large spatial scale will provide critical information for the formulation of optimal harvesting strategies. This study evaluates the feasibility of C-band polarimetric synthetic aperture radar (PolSAR) for monitoring the harvesting progress of oilseed rape (Brassica napus L.) fields. Five multitemporal, quad-pol Radarsat-2 images and one optical ZY-1 02C image were acquired over a farmland area in China during the 2013 growing season. Typical polarimetric signatures were obtained relying on polarimetric decomposition methods. Temporal evolutions of these signatures of harvested fields were compared with the ones of unharvested fields in the context of the entire growing cycle. Significant sensitivity was observed between the specific polarimetric parameters and the harvest status of oilseed rape fields. Based on this sensitivity, a new method that integrates two polarimetric features was devised to detect the harvest status of oilseed rape fields using a single image. The validation results are encouraging even for the harvested fields covered with high residues. This research demonstrates the capability of PolSAR remote sensing in crop harvest monitoring, which is a step toward more complex applications of PolSAR data in precision agriculture.

  1. Wide area, coarse resolution imaging with satellite-borne synthetic aperture radars in low-earth and geosynchronous orbits

    NASA Technical Reports Server (NTRS)

    Tomiyasu, K.

    1981-01-01

    The LEOSAR (low-earth-orbit synthetic aperture radar) can map around the earth, while the GEOSAR (geosynchronous synthetic aperture radar) can map a large global area bounded in both longitudinal and latitudinal ranges. This paper presents the mapping capabilities and power requirements of both LEOSAR and GEOSAR. For a low-earth-orbit SAR, images of swath widths of the order of 700 km are possible with 100-m resolution and 300 watts of average transmitter power at 9375 MHz. From a SAR in a 50-deg inclined geosynchronous circular orbit, the contiguous United States can be imaged in about 6.4 hours with 100-m resolution, 345 watts of average transmitter power, and a data rate of 6 megabits/sec at 2450 MHz.

  2. Automatic target recognition (ATR) performance on wavelet-compressed synthetic aperture radar (SAR) imagery

    NASA Astrophysics Data System (ADS)

    Hoffelder, Michael; Tian, Jun

    2000-08-01

    With the large amount of image data that can be produced in real-time by new synthetic aperture radar (SAR) platforms, such as Global Hawk, compression techniques will be needed for both transmission and storage of this data. Also to keep image analysts (IA's) from being overwhelmed, high-speed automatic target cueing and/or recognition (ATC, ATR) systems will be needed to help exploit this large amount of data in real-time. Past SAR image compression studies have used subjective visual ratings and/or statistical measures such as mean-squared-error (MSE) to compare compression performance. Statistical metrics are much more appealing than unreproducible biased visual interpretations. However, the use of statistical metrics, such as MSE, has practical limitations on SAR imagery due to the high frequency speckle noise that is characteristic. In this case, the MSE metric is dominated by how well the noise speckle is preserved -- a statistic that is of no consequence. Since the large amount of data that dictates the need for compression also dictates the need for ATR, a meaningful statistic would be ATR performance. This ATR performance metric would emphasize how well pixels on target are preserved. Therefore, we have investigated ATR performance using a wavelet compression technique, since this technique has achieved very high compression on other types of imagery. We have used the Rice University Computational Mathematics Laboratory's wavelet compression algorithm in conjunction with a 'synthetic discriminant function' (SDF) based ATR algorithm. The SDF technique was developed at Carnegie Mellon University and successfully applied to SAR imagery by the Northrop Grumman Science & Technology Center. This combination allows ATR performance to be parameterized as a function of compression rate. The SAR data used for this research was taken from the public-released MSTAR target and clutter data set. We show results for both target detection and target identification versus false alarms for varying compression rates.

  3. Refining low-quality digital elevation models using synthetic aperture radar interferometry

    NASA Astrophysics Data System (ADS)

    Seymour, Michael Shawn

    Two-pass synthetic aperture radar (SAR) interferometry (InSAR) is a technique for processing the phase difference between coincident SAR images to obtain the range difference from the two radars to a common point on the earth's surface. The accuracy of the range difference measurement is in the order of one millimeter, and this range information can be processed to obtain digital elevation models (DEMs) of the surface topography. The objective of this thesis is to use supplemental information in the form of a coarse DEM to make the InSAR processing more accurate and more automatic. We achieve this objective by developing a new algorithm which incorporates the coarse DEM directly into the processing stream, with the result that phase unwrapping and geometry estimation are performed accurately and reliably. While the accuracy of each input DEM point is not very high, the large number of them provide adequate geometric accuracy, particularly as an automatic algorithm can register them directly to the radar data. There are two key steps in the new algorithm. First of all, the satellite geometry is estimated from the DEM and interferometric phase. This is done with a non-linear, iterative optimization algorithm without having to unwrap the phase. Second, the input DEM along with the refined satellite geometry are used to create a model of the unwrapped interferogram phase that should be received from the two satellite passes. When this phase is wrapped, and compared with the measured phase, a differential interferogram is obtained which represents the difference between the coarse input DEM and the topography as measured by the satellite. The information in the unwrapped interferogram is used to refine the grid spacing and vertical accuracy of the coarse DEM. We have used mathematical analysis and simulation to develop the algorithm, to obtain statistical quality measures and to understand what system parameters affect the accuracy of the DEM results. We find that the main factors affecting accuracy are the interferometer's sensitivity of phase to height and the number of available DEM points, including the size and variability of the input DEMs' errors. We have successfully applied the DEM refinement algorithm to ERS Tandem Mission and RADARSAT-1 data. The generated InSAR DEMs had standard deviations of 12 to 20 meters compared to a control DEM with approximately 3 meters standard deviation. The output InSAR-enhanced DEMs had two to four times improvement in height accuracy compared with the input DEMs. We have demonstrated that one can generate reliable estimates of topography for standard SAR scenes without having access to precision orbit data. (Abstract shortened by UMI.)

  4. On the extraction of directional sea-wave spectra from synthetic- aperture radar-signal arrays without matched filtering.

    USGS Publications Warehouse

    Wildey, R.L.

    1980-01-01

    An economical method of digitally extracting sea-wave spectra from synthetic-aperture radar-signal records, which can be performed routinely in real or near-real time with the reception of telemetry from Seasat satellites, would be of value to a variety of scientific disciplines. This paper explores techniques for such data extraction and concludes that the mere fact that the desired result is devoid of phase information does not, of itself, lead to a simplification in data processing because of the nature of the modulation performed on the radar pulse by the backscattering surface. -from Author

  5. Digital Beamforming Synthetic Aperture Radar (DBSAR): Performance Analysis During the Eco-3D 2011 and Summer 2012 Flight Campaigns

    NASA Technical Reports Server (NTRS)

    Rincon, Rafael F.; Fatoyinbo, Temilola; Carter, Lynn; Ranson, K. Jon; Vega, Manuel; Osmanoglu, Batuhan; Lee, SeungKuk; Sun, Guoqing

    2014-01-01

    The Digital Beamforming Synthetic Aperture radar (DBSAR) is a state-of-the-art airborne radar developed at NASA/Goddard for the implementation, and testing of digital beamforming techniques applicable to Earth and planetary sciences. The DBSAR measurements have been employed to study: The estimation of vegetation biomass and structure - critical parameters in the study of the carbon cycle; The measurement of geological features - to explore its applicability to planetary science by measuring planetary analogue targets. The instrument flew two test campaigns over the East coast of the United States in 2011, and 2012. During the campaigns the instrument operated in full polarimetric mode collecting data from vegetation and topography features.

  6. Rapid, repeat-sample monitoring of crustal deformations and environmental phenomena with the Uninhabited Aerial Vehicle Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Smith, R. C.

    2006-12-01

    The Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) is a precision repeat-pass Interferometric Synthetic Aperture Radar (InSAR) mission being developed by the Jet Propulsion Laboratory and the Dryden Flight Research Center in support of NASAs Science Mission Directorate. UAVSARs unique ability to fly a repeatable flight path, along with an electronically steerable array, allows interferometric data to be obtained with accuracies measured in millimeters. Deploying the radar on an airborne platform will also allow for radar images to be collected and compared with images from the same area taken hours or even years later - providing for long-term trending and near-real-time notification of changes and deformations. UAVSARs data processing algorithms will provide for near-real time data reduction providing disaster planning and response teams with highly accurate data to aid in the prediction of, and response to, natural phenomena. UAVSAR data can be applied to increasing our understanding of the processes behind solid earth, cryosphere, carbon cycle and other areas of interest in earth science. Technologies developed for UAVSAR may also be applicable to a future earth-orbiting InSAR mission and possibly for missions to the Moon or Mars. The UAVSAR is expected to fly on a Gulfstream III aircraft this winter, followed by a flight test program lasting until the second half of 2007. Following radar calibration and data reduction activities, the platform will be ready for science users in the summer of 2008.

  7. Rapid, Repeat-sample Monitoring of Crustal Deformations and Environmental Phenomena with the Uninhabited Aerial Vehicle Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Smith, Robert C.

    2006-01-01

    The Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) is a precision repeat-pass Interferometric Synthetic Aperture Radar (InSAR) mission being developed by the Jet Propulsion Laboratory and the Dryden Flight Research Center in support of NASA s Science Mission Directorate. UAVSAR's unique ability to fly a repeatable flight path, along with an electronically steerable array, allows interferometric data to be obtained with accuracies measured in millimeters. Deploying the radar on an airborne platform will also allow for radar images to be collected and compared with images from the same area taken hours or even years later - providing for long-term trending and near real-time notification of changes and deformations. UAVSAR s data processing algorithms will provide for near-real time data reduction providing disaster planning and response teams with highly accurate data to aid in the prediction of, and response to, natural phenomena. UAVSAR data can be applied to increasing our understanding of the processes behind solid earth, cryosphere, carbon cycle and other areas of interest in earth science. Technologies developed for UAVSAR may also be applicable to a future earth-orbiting InSAR mission and possibly for missions to the Moon or Mars. The UAVSAR is expected to fly on a Gulfstream III aircraft this winter, followed by a flight test program lasting until the second half of 2007. Following radar calibration and data reduction activities, the platform will be ready for science users in the summer of 2008.

  8. Fine Resolution Topographic Mapping of the Jovian Moons: A Ka-Band High Resolution Topographic Mapping Interferometric Synthetic Aperture Radar

    NASA Technical Reports Server (NTRS)

    Madsen, S. N.; Carsey, F. D.; Turtle, E. P.

    2003-01-01

    The topographic data set obtained by MOLA has provided an unprecedented level of information about Mars' geologic features. The proposed flight of JIMO provides an opportunity to accomplish a similar mapping of and comparable scientific discovery for the Jovian moons through use of an interferometric imaging radar analogous to the Shuttle radar that recently generated a new topographic map of Earth. A Ka-band single pass across-track synthetic aperture radar (SAR) interferometer can provide very high resolution surface elevation maps. The concept would use two antennas mounted at the ends of a deployable boom (similar to the Shuttle Radar Topographic Mapper) extended orthogonal to the direction of flight. Assuming an orbit altitude of approximately 100km and a ground velocity of approximately 1.5 km/sec, horizontal resolutions at the 10 meter level and vertical resolutions at the sub-meter level are possible.

  9. Fine resolution topographic mapping of the Jovian moons: a Ka-band high resolution topographic mapping interferometric synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Madsen, Soren N.; Carsey, Frank D.; Turtle, Elizabeth P.

    2003-01-01

    The topographic data set obtained by MOLA has provided an unprecedented level of information about Mars' geologic features. The proposed flight of JIMO provides an opportunity to accomplish a similar mapping of and comparable scientific discovery for the Jovian moons through us of an interferometric imaging radar analogous to the Shuttle radar that recently generated a new topographic map of Earth. A Ka-band single pass across-track synthetic aperture radar (SAR) interferometer can provide very high resolution surface elevation maps. The concept would use two antennas mounted at the ends of a deployable boom (similar to the Shuttle Radar Topographic Mapper) extended orthogonal to the direction of flight. Assuming an orbit altitude of approximately 100 km and a ground velocity of approximately 1.5 km/sec, horizontal resolutions at the 10 meter level and vertical resolutions at the sub-meter level are possible.

  10. Constructing accurate maps of atmospheric water vapor by combining interferometric synthetic aperture radar and GNSS observations

    NASA Astrophysics Data System (ADS)

    Alshawaf, Fadwa; Hinz, Stefan; Mayer, Michael; Meyer, Franz J.

    2015-02-01

    Over the past 20years, repeat-pass spaceborne interferometric synthetic aperture radar (InSAR) has been widely used as a geodetic technique to generate maps of the Earth's topography and to measure the Earth's surface deformation. In this paper, we present a new approach to exploit microwave data from InSAR, particularly Persistent Scatterer InSAR (PSI), and Global Navigation Satellite Systems (GNSS) to derive maps of the absolute water vapor content in the Earth's atmosphere. Atmospheric water vapor results in a phase shift in the InSAR interferogram, which if successfully separated from other phase components provides valuable information about its distribution. PSI produces precipitable water vapor (PWV) difference maps of a high spatial density, which can be inverted using the least squares method to retrieve PWV maps at each SAR acquisition time. These maps do not contain the absolute (total) PWV along the signal path but only a part of it. The components eliminated by forming interferograms or phase filtering during PSI data processing are reconstructed using GNSS phase observations. The approach is applied to build maps of absolute PWV by combining data from InSAR and GNSS over the region of Upper Rhine Graben in Germany and France. For validation, we compared the derived PWV maps with PWV maps measured by the optical sensor MEdium-Resolution Imaging Spectrometer. The results show strong spatial correlation with values of uncertainty of less than 1.5mm. Continuous grids of PWV are then produced by applying the kriging geostatistical interpolation technique that exploits the spatial correlations between the PWV observations.

  11. Maritime surveillance with synthetic aperture radar (SAR) and automatic identification system (AIS) onboard a microsatellite constellation

    NASA Astrophysics Data System (ADS)

    Peterson, E. H.; Zee, R. E.; Fotopoulos, G.

    2012-11-01

    New developments in small spacecraft capabilities will soon enable formation-flying constellations of small satellites, performing cooperative distributed remote sensing at a fraction of the cost of traditional large spacecraft missions. As part of ongoing research into applications of formation-flight technology, recent work has developed a mission concept based on combining synthetic aperture radar (SAR) with automatic identification system (AIS) data. Two or more microsatellites would trail a large SAR transmitter in orbit, each carrying a SAR receiver antenna and one carrying an AIS antenna. Spaceborne AIS can receive and decode AIS data from a large area, but accurate decoding is limited in high traffic areas, and the technology relies on voluntary vessel compliance. Furthermore, vessel detection amidst speckle in SAR imagery can be challenging. In this constellation, AIS broadcasts of position and velocity are received and decoded, and used in combination with SAR observations to form a more complete picture of maritime traffic and identify potentially non-cooperative vessels. Due to the limited transmit power and ground station downlink time of the microsatellite platform, data will be processed onboard the spacecraft. Herein we present the onboard data processing portion of the mission concept, including methods for automated SAR image registration, vessel detection, and fusion with AIS data. Georeferencing in combination with a spatial frequency domain method is used for image registration. Wavelet-based speckle reduction facilitates vessel detection using a standard CFAR algorithm, while leaving sufficient detail for registration of the filtered and compressed imagery. Moving targets appear displaced from their actual position in SAR imagery, depending on their velocity and the image acquisition geometry; multiple SAR images acquired from different locations are used to determine the actual positions of these targets. Finally, a probabilistic inference model combines the SAR target data with transmitted AIS data, taking into account nearest-neighbor position matches and uncertainty models of each observation.

  12. Synthetic aperture radar-based techniques and reconfigurable antenna design for microwave imaging of layered structures

    NASA Astrophysics Data System (ADS)

    Fallahpour, Mojtaba

    In the past several decades, a number of microwave imaging techniques have been developed for detecting embedded objects (targets) in a homogeneous media. New applications such as nondestructive testing of layered composite structures, through-wall and medical imaging require more advanced imaging systems and image reconstruction algorithms (post-processing) suitable for imaging inhomogeneous (i.e., layered) media. Currently-available imaging algorithms are not always robust, easy to implement, and fast. Synthetic aperture radar (SAR) techniques are some of the more prominent approaches for image reconstruction when considering low loss and homogeneous media. To address limitations of SAR imaging, when interested in imaging an embedded object in an inhomogeneous media with loss, two different methods are introduced, namely; modified piecewise SAR (MPW-SAR) and Wiener filter-based layered SAR (WL-SAR). From imaging system hardware point-of-view, microwave imaging systems require suitable antennas for signal transmission and data collection. A reconfigurable antenna which its characteristics can be dynamically changed provide significant flexibility in terms of beam-forming, reduction in unwanted noise and multiplicity of use including for imaging applications. However, despite these potentially advantageous characteristics, the field of reconfigurable antenna design is fairly new and there is not a methodical design procedure. This issue is addressed by introducing an organized design method for a reconfigurable antenna capable of operating in several distinct frequency bands. The design constraints (e.g., size and gain) can also be included. Based on this method, a novel reconfigurable coplanar waveguide-fed slot antenna is designed to cover several different frequency bands while keeping the antenna size as small as possible.

  13. Using Synthetic Aperture Radar to Study River Ice Breakup on the Kuparuk River, Northern Alaska

    NASA Astrophysics Data System (ADS)

    Floyd, A.; Prakash, A.; Meyer, F. J.; Gens, R.; Liljedahl, A. K.

    2012-12-01

    A combined use of remote sensing techniques and in-situ measurements is an effective approach to study Arctic hydrology, given the vastness, complexity, and logistical challenges posed by most Arctic watersheds. Remote sensing techniques can provide tools to assess the geospatial variations that form the integrated response of a river system and, therefore, provide important details to study one of the effects of climate change on the remote Arctic environment. This study investigates the breakup response of the Kuparuk River on the North Slope of Alaska using synthetic aperture radar (SAR). Imagery and runoff data collected during the spring and summer months between 2001 and 2010 from the Lower Kuparuk River are included in the analysis, which totals 65 SAR images. Image processing results have been calibrated with in-situ stream gauge data provided by USGS gauging station 15896000, on the Lower Kuparuk River, near the town of Deadhorse, Alaska. A time series was assembled to examine the breakup initiation in the subsets through statistical analysis. Images were stacked, geocoded using a Fast Fourier Transform, subset, masked, and divided into subsections. The statistics of each subsection were then compiled and analyzed. Arctic river breakup is a dynamic process. Therefore, we expected drastic change in river surface conditions to correspond to a large variance in backscatter between river subsections. However, before and after breakup we expected image subsections to have largely homogenous statistics. This was verified in nearly all of the image sets, although some variance still existed before and after the breakup event as a result of other conflicting variables. Changes in wind velocity, water depth, and size of point bars all contributed to these confounding variances. Combined with a comprehensive field campaign, SAR imagery interpretations have the potential to develop into a useful monitoring tool for monitoring Arctic rivers and developing resource management plans for neighboring communities.

  14. Observation of melt onset on multiyear Arctic sea ice using the ERS 1 synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Winebrenner, D. P.; Nelson, E. D.; Colony, R.; West, R. D.

    1994-01-01

    We present nearly coincident observations of backscattering from the Earth Remote-Sensing Satellite (ERS) 1 synthetic aperture radar (SAR) and of near-surface temperature from six drifting buoys in the Beaufort Sea, showing that the onset of melting in snow on multiyear sea ice is clearly detectable in the SAR data. Melt onset is marked by a clean, steep decrease in the backscattering cross section of multiyear ice at 5.3 GHz and VV polarization. We investigate the scattering physics responsible for the signature change and find that the cross section decrease is due solely to the appearance of liquid water in the snow cover overlying the ice. A thin layer of moist snow is sufficient to cause the observed decrease. We present a prototype algorithm to estimate the date of melt onset using the ERS 1 SAR and apply the algorithm first to the SAR data for which we have corresponding buoy temperatures. The melt onset dates estimated by the SAR algorithm agree with those obtained independently from the temperature data to within 4 days or less, with the exception of one case in which temperatures oscillated about 0 C for several weeks. Lastly, we apply the algorithm to the entire ERS 1 SAR data record acquired by the Alaska SAR Facility for the Beaufort Sea north of 73 deg N during the spring of 1992, to produce a map of the dates of melt onset over an area roughly 1000 km on a side. The progression of melt onset is primarily poleward but shows a weak meridional dependence at latitudes of approximately 76 deg-77 deg N. Melting begins in the southern part of the study region on June 13 and by June 20 has progressed to the northermost part of the region.

  15. Modeling Water Flow in the Everglades Wetlands Using Interferometric Synthetic Aperture Radar (InSAR)Observations

    NASA Astrophysics Data System (ADS)

    Garcia-Martinez, R.; Miralles-Wilhelm, F.; Wdowinski, S.

    2005-05-01

    New space-based Interferometric Synthetic Aperture Radar (InSAR) observations of the Everglades wetlands provide high spatial resolution maps of water level changes that are essential for improved modeling efforts of surface water sheetflow. In this study, we model the Everglades' Water Conservation Area 1 (WCA-1), which is used to restore, protect, and preserve water resources and wildlife in southern Florida. We use a 2-D surface flow finite element model that considers the vegetation cover as a spatially roughness variable, topography data and influence of peripheral canals. The model provides the water elevation and velocity field throughout the conservation areas, based on rainfall record, discharge inputs and outflows through managed hydraulic structures. Our study focuses on two InSAR observed water level change patterns in WCA-1 acquired during two seasons and different weather conditions. The first pattern describes water level changes in the spring of 1998, showing a radial change caused mainly due to flow along the peripheral canals. The second pattern describes longitudinal change occurring in the fall of 2004, in the peak of hurricanes season, which caused abrupt flow income into the conservation areas. In order to improve the model results, we use a two-step procedure to calculate the vegetation roughness coefficient, which varies both in space and time. The first step includes a Supervised Image Analysis classification of WCA-1 according to remotely sensed determined vegetation maps. The estimated values are assigned to the model for the initial run. In the second step, we use an iterative procedure adjusting the vegetation roughness coefficients until the modeled water level changes agree with the InSAR observations. This technique of coupling high spatial resolution InSAR images with numerical modeling allows improved predictive abilities in the WCA under different weather scenarios, thus helping water resources managers and operators in their decision making.

  16. Coal mining induced land subsidence monitoring using multiband spaceborne differential interferometric synthetic aperture radar data

    NASA Astrophysics Data System (ADS)

    Yue, Huanyin; Liu, Guang; Guo, Huadong; Li, Xinwu; Kang, Zhizhong; Wang, Runfeng; Zhong, Xuelian

    2011-01-01

    The differential interferometric synthetic aperture radar (SAR)(DInSAR) technique has been applied to the earth surface deformation monitoring in many areas. In this paper, the DInSAR technique is used to process the spaceborne SAR data including C band ENVISAT ASAR, L band JERS SAR, and ALOS PALSAR data to derive the temporal land subsidence information in the Fengfeng coal mine area, Hebei province in China. Since JERS and ALOS do not have precise orbit, an orbit adjustment must be accomplished before the DInSAR interferogram was formed. Twenty-three differential interferograms are derived to show the temporal change of the land subsidence range and position. At the acquisition time of ENVISAT ASAR, the leveling in the Dashucun coal mine in Fengfeng area was carried, the historical excavation data in 8 coal mines in Fengfeng area from 1992 to 2007 were collected as well. In our analysis, the DInSAR results are compared with leveling data and historical excavation data. The comparison results show the DInSAR subsidence results are consistent with the leveling results and the historical excavation data, and the L band DInSAR shows more advantages than C band in the coal mining induced subsidence monitoring in a rural area. The feasibility and limitations in coal mining induced subsidence monitoring with DInSAR are analyzed, and the possibility of underground mining activity monitoring by spaceborne InSAR data is evaluated. The experimental results show that both C and L band can accomplish monitoring mining area subsidence, but C band has more restricted conditions of its perpendicular baseline. In order to get a satisfactory outcome in mining area subsidence by the DInSAR method, the time series of SAR images of every visit and SAR deformation interferograms should be archived.

  17. Integration of optical and Synthetic Aperture Radar (SAR) imagery for delivering operational annual crop inventories

    NASA Astrophysics Data System (ADS)

    McNairn, Heather; Champagne, Catherine; Shang, Jiali; Holmstrom, Delmar; Reichert, Gordon

    Agriculture plays a critical role within Canada's economy and, as such, sustainability of this sector is of high importance. Targeting and monitoring programs designed to promote economic and environmental sustainability are a vital component within Canada's agricultural policy. A hierarchy of land information, including up to date information on cropping practices, is needed to measure the impacts of programs on land use decision-making and to gauge the environmental and economic benefits of these investments. A multi-year, multi-site research activity was completed to develop a robust methodology to inventory crops across Canada's large and diverse agricultural landscapes. To move towards operational implementation the methodology must deliver accurate crop inventories, with consistency and reliability. In order to meet these operational requirements and to mitigate risk associated with reliance on a single data source, the methodology integrated both optical and Synthetic Aperture Radar (SAR) imagery. The results clearly demonstrated that multi-temporal satellite data can successfully classify crops for a variety of cropping systems present across Canada. Overall accuracies of at least 85% were achieved, and most major crops were also classified to this level of accuracy. Although multi-temporal optical data would be the preferred data source for crop classification, a SAR-optical dataset (two Envisat ASAR images and one optical image) provided acceptable accuracies and will mitigate risk associated with operational implementation. The preferred dual-polarization mode would be VV-VH. Not only were these promising classification results repeated year after year, but the target accuracies were met consistently for multiple sites across Canada, all with varying cropping systems.

  18. Synthetic aperture radar image formation for the moving-target and near-field bistatic cases

    NASA Astrophysics Data System (ADS)

    Ding, Yu

    This dissertation addresses topics in two areas of synthetic aperture radar (SAR) image formation: time-frequency based SAR imaging of moving targets and a fast backprojection (BP) algorithm for near-field bistatic SAR imaging. SAR imaging of a moving target is a challenging task due to unknown motion of the target. We approach this problem in a theoretical way, by analyzing the Wigner-Ville distribution (WVD) based SAR imaging technique. We derive approximate closed-form expressions for the point-target response of the SAR imaging system, which quantify the image resolution, and show how the blurring in conventional SAR imaging can be eliminated, while the target shift still remains. Our analyses lead to accurate prediction of the target position in the reconstructed images. The derived expressions also enable us to further study additional aspects of WVD-based SAR imaging. Bistatic SAR imaging is more involved than the monostatic SAR case, because of the separation of the transmitter and the receiver, and possibly the changing bistatic geometry. For near-field bistatic SAR imaging, we develop a novel fast BP algorithm, motivated by a newly proposed fast BP algorithm in computer tomography. First we show that the BP algorithm is the spatial-domain counterpart of the benchmark o -- k algorithm in bistatic SAR imaging, yet it avoids the frequency-domain interpolation in the o -- k algorithm, which may cause artifacts in the reconstructed image. We then derive the band-limited property for BP methods in both monostatic and bistatic SAR imaging, which is the basis for developing the fast BP algorithm. We compare our algorithm with other frequency-domain based algorithms, and show that it achieves better reconstructed image quality, while having the same computational complexity as that of the frequency-domain based algorithms.

  19. Fault Creep along the Southern San Andreas from Interferometric Synthetic Aperture Radar, Permanent Scatterers, and Stacking

    NASA Technical Reports Server (NTRS)

    Lyons, Suzanne; Sandwell, David

    2003-01-01

    Interferometric synthetic aperture radar (InSAR) provides a practical means of mapping creep along major strike-slip faults. The small amplitude of the creep signal (less than 10 mm/yr), combined with its short wavelength, makes it difficult to extract from long time span interferograms, especially in agricultural or heavily vegetated areas. We utilize two approaches to extract the fault creep signal from 37 ERS SAR images along the southem San Andreas Fault. First, amplitude stacking is utilized to identify permanent scatterers, which are then used to weight the interferogram prior to spatial filtering. This weighting improves correlation and also provides a mask for poorly correlated areas. Second, the unwrapped phase is stacked to reduce tropospheric and other short-wavelength noise. This combined processing enables us to recover the near-field (approximately 200 m) slip signal across the fault due to shallow creep. Displacement maps fiom 60 interferograms reveal a diffuse secular strain buildup, punctuated by localized interseismic creep of 4-6 mm/yr line of sight (LOS, 12-18 mm/yr horizontal). With the exception of Durmid Hill, this entire segment of the southern San Andreas experienced right-lateral triggered slip of up to 10 cm during the 3.5-year period spanning the 1992 Landers earthquake. The deformation change following the 1999 Hector Mine earthquake was much smaller (4 cm) and broader than for the Landers event. Profiles across the fault during the interseismic phase show peak-to-trough amplitude ranging from 15 to 25 mm/yr (horizontal component) and the minimum misfit models show a range of creeping/locking depth values that fit the data.

  20. Hierarchical ship detection and recognition with high-resolution polarimetric synthetic aperture radar imagery

    NASA Astrophysics Data System (ADS)

    Lang, Haitao; Zhang, Jie; Zhang, Ting; Zhao, Di; Meng, Junmin

    2014-01-01

    Ship surveillance by remote sensing technology has become a valuable tool for protecting marine environments. In recent years, the successful launch of advanced synthetic aperture radar (SAR) sensors that have high resolution and multipolarimetric modes has enabled researchers to use SAR imagery for not only ship detection but also ship category recognition. A hierarchical ship detection and recognition scheme is proposed. The complementary information obtained from multipolarimetric modes is used to improve both the detection precision and the recognition accuracy. In the ship detection stage, a three-class fuzzy c-means clustering algorithm is used to calculate the segmenting threshold for prescreening ship candidates. To reduce the false alarm rate (FAR), we use a two-step discrimination strategy. In the first step, we fuse the detection results from multipolarimetric channels to reduce the speckle noise, ambiguities, sidelobes, and other sources of interference. In the second step, we use a binary classifier, which is trained with prior data collected on ships and nonships, to reduce the FAR even further. In the ship category recognition stage, we concatenate texture-based descriptors extracted from multiple polarmetric channels to construct a robust ship representation for category recognition. Furthermore, we construct and release a ship category database with real SAR data. We hope that it can be used to promote investigations of SAR ship recognition in the remote sensing and related academic communities. The proposed method is validated by a comprehensive experimental comparison to the state-of-the-art methods. The validation procedure showed that the proposed method outperforms all of the competing methods by about 5% and 15% in terms of ship detection and recognition, respectively.

  1. Earth Surface Change as Viewed by the Spaceborne Imaging Radar-C. X-Band Synthetic Aperture Radar (SIR-C/X-SAR) and shuttle Hand-Held Photographs

    NASA Technical Reports Server (NTRS)

    Evans, D. L.; Stofan, E. R.; Jones, T. D.; Godwin, L.

    1994-01-01

    The Spaceborne Imaging Radar-C, X-Band Synthetic Aperture Radar (SIR-C/X-SAR) was launched on space shuttle Endeavour at 7:05 AM EDT, Saturday, April 9, 1994 as part of the Space Radar Lab (SRL-1). Soon after launch, the radars were activated and began arount the clock operations which lasted for the next 10 days.

  2. Tracking Changes in Coastal and Nearshore Morphology in the Southern Beaufort Sea Using Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Solomon, S. M.; Fraser, P.; Whalen, D.

    2007-12-01

    Nearshore morphology in the Mackenzie Delta region of the Beaufort Sea is poorly known because much of the region is very shallow (< 2 m) and the water is highly turbid. Synthetic Aperture Radar (SAR) has been used to map nearshore morphology of lakes in Alaska by taking advantage of the ability of radar waves to penetrate freshwater ice. This technique has been extended to the Mackenzie Delta nearshore region where winter ice forms from river water that is sufficiently fresh so as to be transparent at SAR frequencies. SAR allows the delineation of sea ice that freezes to the seabed (bottom-fast ice or BFI). A time series of imagery throughout a winter depicts the progressive growth of areas where BFI occurs and if sea ice thickness is known at the time of imaging, the delineation of BFI zones represents a proxy for bathymetry. Progressive development of BFI was mapped through the winters of 2003-07 and isolated images from other years are available. The nearshore morphology of the region as revealed by BFI mapping is characterized by extensive nearshore shoals that form at the mouths of active distributaries and are separated by wide, slightly deeper embayments. Narrow channels can be seen to transect the shoals both aligned with and orthogonal to the river outflow. Detailed images from thick ice years depict channels fanning out to feed distributary mouth bars. Comparison of images acquired over more than 10 years suggest that shoal migration can exceed 100 m per year and channel incision of the shoals to depths of >5 m has occurred. The BFI imagery suggests that there is sufficient room beneath the sea ice cover to permit river discharge to reach the shelf without requiring extensive networks of sub- ice channels. The distribution of bottomfast ice also constrains discharge during winter and spring. High inflows occurring during winter surges may lift the ice canopy or over flow onto the surface of the ice disrupting transportation networks. Negative surges in winter can seal off channels. Rising spring discharge is routed over the surface of the nearshore ice when the capacity of the constrained sub-ice drainage network is exceeded causing extensive flooding of the ice surface and strudel drainage to occur.

  3. Monitoring flooding and vegetation on seasonally inundated floodplains with multifrequency polarimetric synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Hess, Laura Lorraine

    The ability of synthetic aperture radar to detect flooding and vegetation structure was evaluated for three seasonally inundated floodplain sites supporting a broad variety of wetland and upland vegetation types: two reaches of the Solimoes floodplain in the central Amazon, and the Magela Creek floodplain in Northern Territory, Australia. For each site, C- and L-band polarimetric Shuttle Imaging Radar-C (SIR-C) data was obtained at both high- and low-water stages. Inundation status and vegetation structure were documented simultaneous with the SIR-C acquisitions using low-altitude videography and ground measurements. SIR-C images were classified into cover states defined by vegetation physiognomy and presence of standing water, using a decision-tree model with backscattering coefficients at HH, VV, and HV polarizations as input variables. Classification accuracy was assessed using user's accuracy, producer's accuracy, and kappa coefficient for a test population of pixels. At all sites, both C- and L-band were necessary to accurately classify cover types with two dates. HH polarization was most. useful for distinguishing flooded from non-flooded vegetation (C-HH for macrophyte versus pasture, L-HH for flooded versus non-flooded forest), and cross-polarized L-band data provided the best separation between woody and non-woody vegetation. Increases in L-HH backscattering due to flooding were on the order of 3--4 dB for closed-canopy varzea and igapo forest, and 4--7 dB, for open Melaleuca woodland. The broad range of physiognomies and stand structures found in both herbaceous and woody wetland communities, combined with the variation in the amount of emergent canopy caused by water level fluctuations and phenologic changes, resulted in a large range in backscattering characteristics of wetland communities both within and between sites. High accuracies cannot be achieved for these communities using single-date, single-band, single-polarization data, particularly in the case of distinguishing flooded macrophyte from non-flooded forest vegetation. However, the large changes in backscattering caused by flooding make it possible to achieve good accuracies (>85%) using multi-temporal data. Where river stage records are available, SAR-based maps of inundation status on a series of dates can be linked to long-term stage data to define wetland habitat types based on flooding regime and low-water vegetation cover.

  4. Monitoring delta subsidence with Interferometric Synthetic Aperture Radar (InSAR)

    NASA Astrophysics Data System (ADS)

    Higgins, S.; Overeem, I.; Syvitski, J. P.

    2014-12-01

    Can subsidence in river deltas be monitored in near real-time at the spatial and temporal resolution needed for informing critical management decisions? Interferometric Synthetic Radar Aperture (InSAR) is a satellite-based technique that can map ground deformation with millimeter-scale vertical resolution over thousands of square kilometers. InSAR has enormous potential to shed light on the dynamics of actively subsiding deltas, but the technique is not commonly applied outside of major cities due to the difficulty of performing InSAR in wet, vegetated settings. Given these limitations, how can InSAR best serve the global effort to monitor sinking deltas? Here, an overview of InSAR processing is provided that addresses delta-specific challenges, including frequent cloud-cover in tropical areas; noisy signals in wetlands and flooded fields; dense forests that interact unpredictably with different radar wavelengths; flat landscapes that hinder image stacking algorithms; rapid urban development that can render Digital Elevation Models (DEMs) inaccurate; and a lack of in situ GPS (Global Positioning System) receivers for InSAR calibration. InSAR has unique value for monitoring subsidence in deltas, and some natural and anthropogenic drivers of subsidence can be resolved by InSAR. High-resolution InSAR measurements from the Ganges-Brahmaputra Delta (GBD) are then presented and validated against GPS data. Surface motion is shown to reflect subsurface stratigraphy, and sediment compaction is shown to be the most important factor in this delta on short (non-tectonic) timescales. Average compaction rates throughout the eastern delta range from 0 to > 18 mm/y, varying by more than an order of magnitude depending on the ages and grain sizes of surface and subsurface sediment layers. Fastest subsidence is observed in Holocene organic-rich mud, and slowest subsidence is observed along the Meghna River and in areas with surface or subsurface sand deposits. Although groundwater extraction rates are high in Dhaka, much of the city is built on a consolidated Pleistocene terrace that appears to compact little even under sustained drawdown. This has minimized the impact of anthropogenic fluid extraction in the Dhaka region.

  5. Coastal oceanography applications of spaceborne synthetic aperture radar (SAR) in the Middle Atlantic Bight (MAB)

    NASA Astrophysics Data System (ADS)

    Clemente-Colon, Pablo

    2002-09-01

    This study provides basic interpretative tools necessary to understand spaceborne synthetic aperture radar (SAR) observations of ocean surface signatures in the Middle Atlantic Bight (MAB). The research focuses on SAR imaged features related to dynamical processes over the continental shelf and near-shelf region. Particular attention is given to signatures acquired during summer upwelling. Other processes and features addressed include the detection of coastal plumes and fronts, oceanic internal waves, bathymetric features, as well as ocean surface atmospheric signatures prevalent in SAR imagery. The ability of SAR to detect upwelling conditions and track their evolution in the MAB is demonstrated. The connection between localized low backscatter and seasonal upwelling in the coastal zone is established for the first time using spaceborne SAR together with supporting in situ and satellite thermal and ocean color data. Reduced backscatter over areas of active upwelling is attributed to a combination of factors including water viscosity, atmospheric stability, and the presence of biogenic slicks. Low backscatter patterns imaged by SAR are found to match upwelling patterns in satellite sea surface temperature (SST) observations. The abundance of slick filaments within upwelling areas is frequently indicated by SAR and supports satellite ocean color observations of enhanced biological activity resulting from upwelling-enhanced nutrient availability. Backscatter sensitivity to SST under slick-free conditions is investigated. A coefficient of thermal stability is defined using a simplified thermal front model. The coefficient parameterizes the change in backscatter as a function of boundary layer stability and wind speed. Its dependence on wind speed and on the atmospheric diabatic state is found to be similar to that of the drag coefficient. Values for the coefficient of thermal stability are also in general agreement with previous results based on tower radar observations. The ability of SAR sea surface roughness observations to capture outflow patterns from multiple estuarine sources along the MAB coast is documented. In particular, the spaceborne imaging of a Delaware Bay twin-front plume is shown and its recurrent nature confirmed. Spaceborne SAR imaging of estuarine outflow patterns is found to be consistent with available airborne data and historical in situ salinity observations.

  6. The observation of ocean surface phenomena using imagery from the SEASAT synthetic aperture radar: An assessment

    NASA Astrophysics Data System (ADS)

    Vesecky, John F.; Stewart, Robert H.

    1982-04-01

    Over the period July 4 to October 10, 1978, the SEASAT synthetic aperture radar (SAR) gathered 23 cm wavelength radar images of some 108 km2 of the earth's surface, mainly of ocean areas, at 25-40 m resolution. Our assessment is in terms of oceanographic and ocean monitoring objectives and is directed toward discovering the proper role of SAR imagery in these areas of interest. In general, SAR appears to have two major and somewhat overlapping roles: first, quantitative measurement of ocean phenomena, like long gravity waves and wind fields, as well as measurement of ships; second, exploratory observations of large-scale ocean phenomena, such as the Gulf Stream and its eddies, internal waves, and ocean fronts. These roles are greatly enhanced by the ability of 23 cm SAR to operate day or night and through clouds. To begin we review some basics of synthetic aperture radar and its implementation on the SEASAT spacecraft. SEASAT SAR imagery of the ocean is fundamentally a map of the radar scattering characteristics of 30 cm wavelength ocean waves, distorted in some cases by ocean surface motion. We discuss how wind stress, surface currents, long gravity waves, and surface films modulate the scattering properties of these resonant waves with particular emphasis on the mechanisms that could produce images of long gravity waves. Doppler effects by ocean motion are also briefly described. Measurements of long (wavelength ?100 m) gravity waves, using SEASAT SAR imagery, are compared with surface measurements during several experiments. Combining these results we find that dominant wavelength and direction are measured by SEASAT SAR within 12% and 15, respectively. However, we note that ocean waves are not always visible in SAR images and discuss detection criteria in terms of wave height, length, and direction. SAR estimates of omnidirectional wave height spectra made by assuming that SAR image intensity is proportional to surface height fluctuations are more similar to corresponding surface measurements of wave height spectra than to wave slope spectra. Because SEASAT SAR images show the radar cross section ? of 30 cm waves (neglecting doppler effects), and because these waves are raised by wind stress on the ocean surface, wind measurements are possible. Comparison between wind speeds estimated from SEASAT SAR imagery and from the SEASAT satellite scatterometer (SASS) agreed to within 0.7 m s- over a 350-km comparison track and for wind speeds from 2 to 15 m s-. The great potential of SAR wind measurements lies in studying the spatial structure of the wind field over a range of spatial scales of from ?1 km to ?100 km. At present, the spatial and temporal structure of ocean wind fields is largely unknown. Because SAR responds to short waves whose energy density is a function of wind stress at the surface rather than wind speed at some distance above the surface, variations in image intensity may also reflect changes in air-sea temperature difference (thus complicating wind measurements by SAR). Because SAR images show the effects of surface current shear, air-sea temperature difference, and surface films through their modulation of the 30 cm waves, SEASAT images can be used to locate and study the Gulf Stream and related warm water rings, tidal flows at inlets, internal waves, and slicks resulting from surface films. In many of these applications, SAR provides a remote sensing capability that is complementary to infrared imagery because the two techniques sense largely different properties, namely, surface roughness and temperature. Both stationary ships and moving ships with their attendant wakes are often seen in SAR images. Ship images can be used to estimate ship size, heading, and speed. However, ships known to be in areas imaged by SAR are not always detectable. Clearly, a variety of factors, such as image resolution, ship size, sea state, and winds could affect ship detection. Overall, the role of SAR imagery in oceanography is definitely evolving at this time, but its ultimate role is unclear. We have assessed the ability of SEASAT SAR to measure a variety of ocean phenomena and have commented briefly on applications. In the end, oceanographers and others will have to judge from these capabilities the proper place for SAR in oceanography and remote sensing of the ocean.

  7. Detection of flooded urban areas in high resolution Synthetic Aperture Radar images using double scattering

    NASA Astrophysics Data System (ADS)

    Mason, David; Giustarini, Laura; Garcia-Pintado, Javier; Cloke, Hannah

    2014-05-01

    Flooding is a particular hazard in urban areas worldwide due to the increased risks to life and property in these regions. SAR sensors are often used to image flooding because of their all-weather day-night capability, and now possess sufficient resolution to image urban flooding. The flood extents extracted from the images may be used for flood relief management and improved urban flood inundation modelling. A difficulty with using SAR for urban flood detection is that, due to its side-looking nature, substantial areas of urban ground surface may not be visible to the SAR due to radar layover and shadow caused by buildings and taller vegetation. While most flooding along roads perpendicular to the satellite direction of travel may be detected successfully, a good deal of the flooding along roads parallel to it will remain unseen. Considering the latter, an area of flooded road in front of the wall of a building on the farther side of a road from the satellite track may be allocated to the same range bin as the wall, causing layover which generally results in a strong return, and a possible misclassification of flooded ground as un-flooded. This paper investigates whether urban flooding can be detected in layover regions using double scattering [1]. If the road in a layover region is flooded, backscatter due to the double scattering from sensor to road to wall to sensor (or vice versa) should be stronger than if the road is not flooded. The method estimates double scattering strengths using a SAR image in conjunction with a high resolution LiDAR height map of the urban area. A SAR simulator is applied to the LiDAR data to generate maps of layover and shadow, and estimate the positions of double scattering curves in the SAR image. Observations of double scattering strengths were compared to the predictions from an electromagnetic scattering model, for both the case of a single image containing flooding, and a change detection case in which the flooded image was compared to an un-flooded image of the same area acquired with the same radar parameters. The method proved successful in detecting double scattering due to flooding in the single-image case, for which flooded double scattering curves were detected with 100% classification accuracy (albeit using a small sample set) and un-flooded curves with 91% classification accuracy. The same measures of success were achieved using change detection between flooded and un-flooded images. Depending on the particular flooding situation, the method could lead to improved detection of flooding in urban areas. 1. Mason DC, Giustarini L, Garcia-Pintado J (2014). Detection of flooded urban areas in high resolution Synthetic Aperture Radar images using double scattering. Int. J. Applied Earth Observation and Geoscience, 28C (May 2014), 150-159.

  8. Gulf Coast Subsidence: Integration of Geodesy, Geophysical Modeling, and Interferometric Synthetic Aperture Radar Observations

    NASA Astrophysics Data System (ADS)

    Blom, R. G.; Chapman, B. D.; Deese, R.; Dokka, R. K.; Fielding, E. J.; Hawkins, B.; Hensley, S.; Ivins, E. R.; Jones, C. E.; Kent, J. D.; Liu, Z.; Lohman, R.; Zheng, Y.

    2012-12-01

    The vulnerability of the US Gulf Coast has received increased attention in the years since hurricanes Katrina and Rita. Agencies responsible for the long-term protection of lives and infrastructure require precise estimates of future subsidence and sea level rise. A quantitative, geophysically based methodology can provide such estimates by incorporating geological data, geodetic measurements, geophysical models of non-elastic mechanical behavior at depth, and geographically comprehensive deformation monitoring made possible with measurements from Interferometric Synthetic Aperture Radar (InSAR). To be effective, results must be available to user agencies in a format suitable for integration within existing decision-support processes. Work to date has included analysis of historical and continuing ground-based geodetic measurements. These reveal a surprising degree of complexity, including regions that are subsiding at rates faster than those considered for hurricane protection planning of New Orleans and other coastal communities (http://www.mvn.usace.army.mil/pdf/hps_verticalsettlement.pdf) as well as Louisiana's coastal restoration strategies (http://www.coast2050.gov/2050reports.htm) (Dokka, 2011, J. Geophys. Res., 116, B06403, doi:10.1029/2010JB008008). Traditional geodetic measurements provide precise information at single points, while InSAR observations provide geographically comprehensive measurements of surface deformation at lower vertical precision. Available InSAR data sources include X-, C- and L-band satellite, and NASA/JPL airborne UAVSAR L-band data. The Gulf Coast environment is very challenging for InSAR techniques, especially with systems not designed for interferometry. For example, the shorter wavelength C-band data decorrelates over short time periods requiring more elaborate time-series analysis techniques, with which we've had some success. Meanwhile, preliminary analysis of limited L-Band ALOS/PALSAR satellite data show promise; unfortunately this Japanese satellite system failed in April 2011. We now have multiple airborne UAVSAR repeat pass interferometry data sets under analysis (http://uavsar.jpl.nasa.gov/) . UAVSAR interferogram processing has proven problematic in this environment, and new acquisitions are planned at shorter temporal intervals to yield improved results. Combining the geodetic and InSAR data can constrain geophysical models of crustal behavior, leading to quantitative predictions of future subsidence. Model results to date show good agreement between geodetic measurements and geophysically reasonable parameters including sediment load and ~130 m post-glacial sea level rise. We review work to date and present newly acquired UAVSAR data.

  9. Novel guided-wave electro-optic processor for synthetic aperture radar imaging

    NASA Astrophysics Data System (ADS)

    Armenise, Mario N.; Passaro, Vittorio M.

    1994-06-01

    We present the theoretical investigation of a novel architecture of a LiNbO3 guided-wave optical processor suitable for real-time microwave imaging in on-board synthetic aperture radar (SAR) applications, using a moving platform on either an aircraft or a spacecraft. The new configuration, which is basically interferometric, includes four Mach-Zehnder modulators, each characterized by an additional aperiodic phase-reversal traveling wave modulator. The electrode configuration is appropriately designed to reproduce the product of the base-band SAR received echoes and two reference signals and, then, to perform both the range and azimuth compression. The two product signals are separately time integrated by two fast photodetectors. The sampled signals coming out of the detectors include both the required product signals and intermodulation products and are electronically filtered for reproducing the correct product with no amplitude distortion. At this stage, the signals are multiplexed and registered on a 2D buffer to reproduce the final correlation functions for the range and azimuth directions. Because of the serial multiplication between the received echoes and reference signals, the circuit can operate with very long data streams. Our proposed processor can reproduce the images coming from ground features using a conventional chirp pulse SAR system with the antenna beam looking at 90 deg from the direction of platform motion. The circuit can operate at a free-space wavelength of 1.3 micrometers with a radiofrequency of 410 MHz, a response time/bandwidth ratio of approximately equals 10-5 microsecond(s) /MHz, a linear dynamic range of approximately equals 50 dB, and an SNR approximately equals 8 dB, assuming chirp pulses as reference signals. The circuit performance is evaluated by considering lithium niobate as the substrate material and two different waveguide fabrication techniques: titanium indiffusion (Ti:LiNbO3) and proton exchange with annealing (APE:LiNbO3). The best results in terms of linear dynamic range and optical losses are obtained by the titanium indiffused channel waveguides. We calculated in any fabrication condition a swath range resolution of d(sigma) approximately equals 10 m in airborne simulation and about 60 m in the satellite simulation, whereas the azimuth resolution is about d(rho) equals 1.5 and 6 m, respectively. Significant improvements in terms of SNR (90%) and SAR resolution (50%) are obtained by using binary pseudorandom sequences as reference signals, i.e., approximately equals 15 dB, (Delta) (sigma) equals 2 and < 58 m, (Delta) (rho) approximately equals 1.5 and 6 m, respectively.

  10. Oil Spill Detection and Tracking Using Lipschitz Regularity and Multiscale Techniques in Synthetic Aperture Radar Imagery

    NASA Astrophysics Data System (ADS)

    Ajadi, O. A.; Meyer, F. J.

    2014-12-01

    Automatic oil spill detection and tracking from Synthetic Aperture Radar (SAR) images is a difficult task, due in large part to the inhomogeneous properties of the sea surface, the high level of speckle inherent in SAR data, the complexity and the highly non-Gaussian nature of amplitude information, and the low temporal sampling that is often achieved with SAR systems. This research presents a promising new oil spill detection and tracking method that is based on time series of SAR images. Through the combination of a number of advanced image processing techniques, the develop approach is able to mitigate some of these previously mentioned limitations of SAR-based oil-spill detection and enables fully automatic spill detection and tracking across a wide range of spatial scales. The method combines an initial automatic texture analysis with a consecutive change detection approach based on multi-scale image decomposition. The first step of the approach, a texture transformation of the original SAR images, is performed in order to normalize the ocean background and enhance the contrast between oil-covered and oil-free ocean surfaces. The Lipschitz regularity (LR), a local texture parameter, is used here due to its proven ability to normalize the reflectivity properties of ocean water and maximize the visibly of oil in water. To calculate LR, the images are decomposed using two-dimensional continuous wavelet transform (2D-CWT), and transformed into Holder space to measure LR. After texture transformation, the now normalized images are inserted into our multi-temporal change detection algorithm. The multi-temporal change detection approach is a two-step procedure including (1) data enhancement and filtering and (2) multi-scale automatic change detection. The performance of the developed approach is demonstrated by an application to oil spill areas in the Gulf of Mexico. In this example, areas affected by oil spills were identified from a series of ALOS PALSAR images acquired in 2010. The comparison showed exceptional performance of our method. This method can be applied to emergency management and decision support systems with a need for real-time data, and it shows great potential for rapid data analysis in other areas, including volcano detection, flood boundaries, forest health, and wildfires.

  11. High-resolution synthetic aperture radar experiments for ATR development and performance prediction

    NASA Astrophysics Data System (ADS)

    Westerkamp, Lori A.; Morrison, S. A.; Wild, Thomas J.; Mossing, John C.

    2002-08-01

    Commercial availability of very high-resolution synthetic aperture radar (SAR) imagery will enable development of automatic target recognition (ATR) algorithms to exploit its rich information content. This availability also permits exploration of both empirical and first principles approaches for predicting ATR performance. This paper describes a recent collection of high resolution SAR imagery. It details the operating conditions represented by the data and provides recommended experiments designed to challenge ATR algorithms and performance prediction. This set of information, along with the imagery, is contained in a Problem Set that will be made available to the community. The imagery is from a Deputy Under Secretary of Defense (DUSD) for Science and Technology (S&T) sponsored collection using the Sandia National Laboratory and General Atomics Lynx Sensor. The Lynx is now available as a commercial off-the-shelf (COTS) sensor. It was designed for use in medium-altitude UAVs and manned platforms. It operates at Ku-band frequency in stripmap, spotlight, and ground moving target indicator modes. Imagery in this collection was collected at 4' resolution and was then also reprocessed to 1' resolution. The collection included several military vehicles with significant variation in target, sensor, and background conditions. Defined experiments in the Problem Set present ATR algorithm development challenges by defining development (training) sets with limited representation of operating conditions and test sets that explore the algorithm's ability to extend to more complex operating conditions. These challenges are critical to military employment of ATR because the real world contains much more variability than it will be possible to explicitly address in an algorithm. For example, neither the storage nor the search through an exhaustive bay of templates is achievable for any realistic application. Thus, advanced developments that allow robust performance in denied conditions will accelerate the transition of ATR to the field. Additional experiments in the Problem Set present challenges in ATR performance prediction. Here, the development imagery provides empirical data to support development of prediction approaches. Test imagery provides an opportunity to validate the prediction technique's ability to, for example, interpolate or extrapolate performance.

  12. Routine Ocean Monitoring With Synthetic Aperture Radar Imagery Obtained From the Alaska Satellite Facility

    NASA Astrophysics Data System (ADS)

    Pichel, W. G.; Clemente-Colon, P.; Li, X.; Friedman, K.; Monaldo, F.; Thompson, D.; Wackerman, C.; Scott, C.; Jackson, C.; Beal, R.; McGuire, J.; Nicoll, J.

    2006-12-01

    The Alaska Satellite Facility (ASF) has been processing synthetic aperture radar (SAR) data for research and for near-real-time applications demonstrations since shortly after the launch of the European Space Agency's ERS-1 satellite in 1991. The long coastline of Alaska, the vast extent of ocean adjacent to Alaska, a scarcity of in-situ observations, and the persistence of cloud cover all contribute to the need for all-weather ocean observations in the Alaska region. Extensive experience with SAR product processing algorithms and SAR data analysis techniques, and a growing sophistication on the part of SAR data and product users have amply demonstrated the value of SAR instruments in providing this all-weather ocean observation capability. The National Oceanic and Atmospheric Administration (NOAA) has been conducting a near-real-time applications demonstration of SAR ocean and hydrologic products in Alaska since September 1999. This Alaska SAR Demonstration (AKDEMO) has shown the value of SAR-derived, high-resolution (sub kilometer) ocean surface winds to coastal weather forecasting and the understanding of coastal wind phenomena such as gap winds, barrier jets, vortex streets, and lee waves. Vessel positions and ice information derived from SAR imagery have been used for management of fisheries, protection of the fishing fleet, enforcement of fisheries regulations, and protection of endangered marine mammals. Other ocean measurements, with potentially valuable applications, include measurement of wave state (significant wave height, dominant wave direction and wavelength, and wave spectra), mapping of oil spills, and detection of shallow-water bathymetric features. In addition to the AKDEMO, ASF-processed SAR imagery is being used: (1) in the Gulf of Mexico for hurricane wind studies, and post-hurricane oil-spill and oil-platform analyses (the latter employing ship-detection algorithms for detection of changes in oil-platform locations); (2) in the North Pacific to help locate convergence zones for marine debris detection (i.e., the GhostNet project); (3) in marine sanctuaries for internal wave climatology in support of marine ecosystem studies, and vessel detection for sanctuary protection; and (4) in coastal areas for ocean feature mapping (eddies, river plumes, upwelling, fronts). These applications demonstrations have added to our understanding of ocean and atmospheric processes and their interaction, particularly in the coastal environment. A much improved knowledge of the highly variable nature of coastal winds such as gap winds and barrier jets is a good example of the contribution that SAR imagery and derived products have made to our understanding of coastal processes.

  13. Using Synthetic Aperture Radar Wind Measurements to support Offshore Wind Parks

    NASA Astrophysics Data System (ADS)

    Schneiderhan, T.; Lehner, S.; Horstmann, J.; Koch, W.; Schulz-Stellenfleth, J.

    2003-04-01

    In all countries with shallow coastal waters and a strong mean wind speed offshore wind parks are planned and built. The fast development of wind energy production in Europe led to an installation of more than 18 000 MW by the end of the year 2001. The installed offshore power up to date is about 100 MW. In the near future many projects for wind farms with an output of more than 5000 MW are planned. Some of these projects are already under construction. Offshore wind parks are showing a big potential for future energy production and solving ecological problems in reducing the CO^2 output. The construction and maintenance of offshore wind parks has to face the tough environmental conditions of the open sea resulting extensive maintenance and money. Therefore reliable forecast in particular of the wind and the ocean wave fields is essential. Space borne SAR data as acquired by the ERS satellites or the new ENVISAT satellite, launched in March 2002, provide two dimensional wind fields with a sub-kilometre resolution and a coverage of up to 500 by 500 km in the wide swath mode. They are thus ideally suited to investigate the spatial fine structure like e.g. turbulence in the wake of wind parks, which is an important factor in the optimal siting of wind farms. Due to their high coverage and resolution SAR data can provide information on the impact of the single turbines on the wind field experienced by the neighbouring turbines as well as the effect of the whole wind park on the local climate. This study shows the potential of two dimensional high resolution wind fields measured with space borne synthetic aperture radar to support the construction and operation of wind farms. The data can be used to minimize fatigue loading due to wind gusts as well as to provide short term power forecasts in order to optimise the power output. Examples of wind fields around the already existing offshore wind parks Utgrunden (South of Sweden) and Horns Rev (West of Denmark) and the first German site under construction Borkum West (North of Borkum Island) are given.

  14. River Delta Subsidence Measured with Interferometric Synthetic Aperture Radar (InSAR)

    NASA Astrophysics Data System (ADS)

    Higgins, Stephanie

    This thesis addresses the need for high-resolution subsidence maps of major world river deltas. Driven by a combination of rising water, sediment compaction, and reduced sediment supply due to damming and flood control, many deltas are sinking relative to sea level. A lack of data constraining rates and patterns of subsidence has made it difficult to determine the relative contributions of each factor in any given delta, however, or to assess whether the primary drivers of land subsidence are natural or anthropogenic. In recent years, Interferometric Synthetic Aperture Radar (InSAR) has emerged as a satellite-based technique that can map ground deformation with mm-scale accuracy over thousands of square kilometers. These maps could provide critical insight into the drivers of subsidence in deltas, but InSAR is not typically applied to non-urban delta areas due to the difficulties of performing the technique in wet, vegetated settings. This thesis addresses those difficulties and achieves high-resolution measurements of ground deformation in rural deltaic areas. Chapter 1 introduces the processes that drive relative sea level rise in river deltas and investigates open questions in delta subsidence research. Chapter 2 assesses the performance of InSAR in delta settings and reviews interferogram generation in the context of delta analysis, presenting delta-specific processing details and guiding interpretation in these challenging areas. Chapter 3 applies Differential (D-) InSAR to the coast of the Yellow River Delta in China. Results show that subsidence rates are as high as 250 mm/y due to groundwater extraction at aquaculture facilities, a rate that exceeds local and global average sea level rise by nearly two orders of magnitude and suggests a significant hazard for Asian megadeltas. Chapter 4 applies interferometric stacking and Small Baseline Subset (SBAS)-InSAR to the Ganges-Brahmaputra Delta, Bangladesh. Results show that stratigraphy controls subsidence in this delta, with concentrated local deformation surrounding Dhaka caused by compaction of the youngest strata. Chapter 5 summarizes and concludes this thesis.

  15. Investigations of the glacier surface properties and ice velocity of the south Patagonian icefield from synthetic aperture radar (SAR)

    NASA Astrophysics Data System (ADS)

    Forster, Richard Robert

    Shuttle imaging radar C/X band synthetic aperture radar (SIR-C/X-SAR) views of the South Patagonian Icefield in southern Chile and Argentina demonstrate the ability of spaceborne multiparameter radar to detect climatically driven changes in the snow and ice conditions on glaciers, observe the effects of weather on the glacier surface, and measure the ice velocity. The SIR-C/X-SAR system aboard space shuttle Endeavor acquired images during two 11-day missions in April and October 1994. The radar signatures of differing snow and ice conditions are distinctive and homogeneous over large areas of the ice fields and are interpreted by correlating the radar characteristics with elevation of the snow and ice surfaces and with changes in the meteorological conditions. We are able to define four "radar glacier zones": The spatial changes in the radar glacier zones between April and October are consistent with colder temperatures recorded in October, producing drier snow conditions at lower elevations than in April. SIR-C/X-SAR imaged a portion of the SPI for five successive days during both the April and October missions. A significant meteorological event occurred during each mission, including a major storm in April and a sharp temperature decrease in October. Ground station and satellite meteorological, and hydrological data are combined with the daily X-SAR images to interpret changes in glacier surface conditions caused by meteorological events. The changes in the radar-defined glacier zones due to the April precipitation event are subtle while the October temperature drop causes significant backscatter increases. Our results suggest that trends in HPS glacier surface and near surface conditions observable from spaceborne SARs are not significantly masked by precipitation events. Interferometric synthetic aperture radar (InSAR) data of a portion of the Hielo Patagonico Sur (HPS), Chile were collected over a four day span in October 1994 and used to generate an ice velocity map. The three outlet glaciers in the radar scene act as ice streams within the icefield flanked by slower moving ice. A flow divide between two of the glaciers is mapped by locating a narrow band of near-zero ice velocity. Horizontal ice surface velocity profiles calculated along flowlines show there is a high degree of spatial variability in velocity along the center-lines with velocities reaching over 2.5 m/day. Longitudinal strain rates, calculated from these velocities, at the locations of the initiation of crevassing agree with theoretical values computed for ice fracture under longitudinal tension.

  16. Inverse synthetic aperture radar imaging for concealed object detection on a naturally walking person

    NASA Astrophysics Data System (ADS)

    Zhuravlev, Andrey; Ivashov, Sergey; Razevig, Vladimir; Vasiliev, Igor; Bechtel, Timothy

    2014-05-01

    This paper describes the architecture of a microwave radar system intended for imaging concealed objects under clothing as a subject walks through the inspection area. The system uses the principle of inverse aperture which is achieved by a person's movement past a stationary microwave sensor array. In the system, the vertical resolution is achieved by arranging microwave sensors vertically while the horizontal resolution is due to the subject's horizontal motion. The positioning of the objects is achieved by employing a synchronous video sensor that allows coherent radar signal processing. A possible radar signal processing technique based on signal accumulation is described. Numerical experiments are conducted with the described object trajectory model. The influence of positioning errors attributed to the video positioning system is also modeled numerically. An experimental setup is designed and proposed to evaluate the suggested signal processing techniques on real data with an electro-mechanical scanner and single transceiver. It is suggested that the signal acquisition with the system can be accomplished using the stop motion technique, in which a series of changing stationary scenes is sampled and processed. Experimental radar images are demonstrated for stationary objects with concealed items and considered as reference images. Further development of the system is suggested.

  17. Surface Ruptures and Building Damage of the 2003 Bam, Iran, Earthquake Mapped by Satellite Synthetic Aperture Radar Interferometric Correlation

    NASA Technical Reports Server (NTRS)

    Fielding, Eric J.; Talebian, M.; Rosen, P. A.; Nazari, H.; Jackson, J. A.; Ghorashi, M.; Walker, R.

    2005-01-01

    We use the interferometric correlation from Envisat synthetic aperture radar (SAR) images to map the details of the surface ruptures related to the 26 December 2003 earthquake that devastated Bam, Iran. The main strike-slip fault rupture south of the city of Bam has a series of four segments with left steps shown by a narrow line of low correlation in the coseismic interferogram. This also has a clear expression in the field because of the net extension across the fault. Just south of the city limits, the surface strain becomes distributed over a width of about 500 m, probably because of a thicker layer of soft sedimentary material.

  18. A comparative study on the current de-speckle methods for polarimetric synthetic aperture radar imagery processing

    NASA Astrophysics Data System (ADS)

    Xu, Zhijia; Sun, Sheng; Yang, Changcai; Zhang, Xiaobo

    2015-12-01

    Speckle filtering seems to be a never-ending topic for polarimetric synthetic aperture radar imagery processing. Constantly emerging literatures demonstrate that this issue deserves further research effort, especially in the context of much more high spatial resolution. A comparative study will be performed in this paper for recently proposed method such as non-local SAR speckle filtering, Extended Sigma filter proposed by Lee, non-local means filter, Bilateral filter, and so on. Their performance on spatial details preserving and polarimetric properties preserving should be measured thoroughly. Further more the computing performance on large-scale dataset should also be measured.

  19. A user's manual for the NASA/JPL synthetic aperture radar and the NASA/JPL L and C band scatterometers

    NASA Technical Reports Server (NTRS)

    Thompson, T. W.

    1983-01-01

    Airborne synthetic aperture radars and scatterometers are operated with the goals of acquiring data to support shuttle imaging radars and support ongoing basic active microwave remote sensing research. The aircraft synthetic aperture radar is an L-band system at the 25-cm wavelength and normally operates on the CV-990 research aircraft. This radar system will be upgraded to operate at both the L-band and C-band. The aircraft scatterometers are two independent radar systems that operate at 6.3-cm and 18.8-cm wavelengths. They are normally flown on the C-130 research aircraft. These radars will be operated on 10 data flights each year to provide data to NASA-approved users. Data flights will be devoted to Shuttle Imaging Radar-B (SIR-B) underflights. Standard data products for the synthetic aperture radars include both optical and digital images. Standard data products for the scatterometers include computer compatible tapes with listings of radar cross sections (sigma-nought) versus angle of incidence. An overview of these radars and their operational procedures is provided by this user's manual.

  20. An Integrated Navigation System using GPS Carrier Phase for Real-Time Airborne Synthetic Aperture Radar (SAR)

    SciTech Connect

    Fellerhoff, J. Rick; Kim, Theodore J.; Kohler, Stewart M.

    1999-06-24

    A Synthetic Aperture Radar (SAR) requires accu- rate measurement of the motion of the imaging plat- form to produce well-focused images with minimal absolute position error. The motion measurement (MoMeas) system consists of a inertial measurement unit (IMU) and a P-code GPS receiver that outputs corrected ephemeris, L1 & L2 pseudoranges, and L1 & L2 carrier phase measurements. The unknown initial carrier phase biases to the GPS satellites are modeled as states in an extended Kalman filter and the resulting integrated navigation solution has po- sition errors that change slowly with time. Position error drifts less than 1- cm/sec have been measured from the SAR imagery for various length apertures.

  1. Inverse synthetic aperture radar imaging of maneuvering target based on cubic chirps model with time-varying amplitudes

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Zhang, Qingxiang; Zhao, Bin

    2016-01-01

    Inverse synthetic aperture radar (ISAR) imaging of maneuvering target is a main topic in the field of radar signal processing, and the received signal in a range bin can usually be characterized as multicomponent cubic chirps with constant amplitudes after motion compensation. In fact, the phenomenon of migration through resolution cell (MTRC) often occurs for the target's complex motion, and this will induce the time-varying character for the amplitudes of cubic chirps. An algorithm for the parameters estimation of multicomponent cubic chirps with time-varying amplitudes based on the extension form of match Fourier transform is proposed, and by using it in ISAR imaging of maneuvering target, the quality of images can be improved significantly compared with the constant amplitudes model. Results of simulated and real data validate the effectiveness of the algorithm in this paper.

  2. Space based topographic mapping experiment using Seasat synthetic aperture radar and LANDSAT 3 return beam vidicon imagery

    NASA Technical Reports Server (NTRS)

    Mader, G. L.

    1981-01-01

    A technique for producing topographic information is described which is based on same side/same time viewing using a dissimilar combination of radar imagery and photographic images. Common geographic areas viewed from similar space reference locations produce scene elevation displacements in opposite direction and proper use of this characteristic can yield the perspective information necessary for determination of base to height ratios. These base to height ratios can in turn be used to produce a topographic map. A test area covering the Harrisburg, Pennsylvania region was observed by synthetic aperture radar on the Seasat satellite and by return beam vidicon on by the LANDSAT - 3 satellite. The techniques developed for the scaling re-orientation and common registration of the two images are presented along with the topographic determination data. Topographic determination based exclusively on the images content is compared to the map information which is used as a performance calibration base.

  3. On the Soil Roughness Parameterization Problem in Soil Moisture Retrieval of Bare Surfaces from Synthetic Aperture Radar

    PubMed Central

    Verhoest, Niko E.C; Lievens, Hans; Wagner, Wolfgang; Álvarez-Mozos, Jesús; Moran, M. Susan; Mattia, Francesco

    2008-01-01

    Synthetic Aperture Radar has shown its large potential for retrieving soil moisture maps at regional scales. However, since the backscattered signal is determined by several surface characteristics, the retrieval of soil moisture is an ill-posed problem when using single configuration imagery. Unless accurate surface roughness parameter values are available, retrieving soil moisture from radar backscatter usually provides inaccurate estimates. The characterization of soil roughness is not fully understood, and a large range of roughness parameter values can be obtained for the same surface when different measurement methodologies are used. In this paper, a literature review is made that summarizes the problems encountered when parameterizing soil roughness as well as the reported impact of the errors made on the retrieved soil moisture. A number of suggestions were made for resolving issues in roughness parameterization and studying the impact of these roughness problems on the soil moisture retrieval accuracy and scale.

  4. The derivation of a sub-canopy digital terrain model of a flooded forest using synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Imhoff, Marc Lee; Gesch, Dean B.

    1990-01-01

    Synthetic aperture radar data from the Shuttle Imaging Radar-B Mission were combined with the tide surface information to create a digital terrain model for a 70-km by 40-km section of the Mouths of the Ganges forests in southern Bangladesh. The dominance of the interaction phenomenon (canopy to surface or surface to canopy reflection) in flooded forests was exploited to create sub-canopy flood boundary maps for two different tide times. The boundary maps were digitally combined in x, y, z space with tide elevation models created from tide gauge data gridding the survey site and used as input to interpolation routines to create a terrain model. The end product represents a significant step in our ability to characterize the topography and hydrology of wetland ecosystems. The model derived here can be used for simulating tidal flow and nutrient transport from the forest to the marine habitat.

  5. Observation of Planetary Oceans with Fully Polarimetric Synthetic Aperture Radar (SAR)

    NASA Astrophysics Data System (ADS)

    Moon, Wooil M.

    Synthetic Aperture Radar (SAR) is one of the most cost effective and powerful all weather tools for observation of planetary surface without sun light. The SAR systems can observe planetary surfaces with the very high resolution and large spatial coverage. We have developed and improved the algorithms for extracting quantitative information on geophysical parameters using various types of SAR data available on Earth's surface, both space-borne SAR (ERS-1/2, RADARSAT, and ENVISAT ASAR) and airborne SAR (NASA(JPL) AIRSAR). SAR is the only system that can provide a synoptic view of find wind fields near the coastal area on Earth. Many SAR images including RADARSAT and ENVISAT ASAR's alternating polarization mode and wide swath mode were to investigate the ability of retrieving sea surface wind field and the results are quite accurate and operationally acceptable. We installed corner reflectors on the nearby beach to calibrate the SAR data, and we obtained in-situ measurements from the several coast-based automatic weather systems and ocean buoys. Using the simultaneously acquired polarization ENVISAT ASAR data (HH and VV), the most appropriate polarization ratio was evaluated and applied for improving the wind retrieval model. In addition, the best combinations depending on given sea states and incidence angle ranges were investigated. The characteristics of short-period and long-period (near-inertial) internal waves are also investigated with several space-borne SAR systems. The possibility of inferring characteristics of the interior ocean dynamics from the SAR image associated with internal solitary waves was tested using a hydrodynamic interaction model (action balance equation) and a radar backscattering model (two-scale tilted Bragg model). These models were used iteratively to fit the observed SAR data to the simulated SAR. The estimated results were compared with in-situ measurements. The typical scales and the spatial and temporal characteristics of internal waves observed in the western part of the East Sea test area were also estimated from more than 140 SAR images. On the other hand, very long wave patterns (13-10 km) were observed in two successively acquired ENVISAT ASAR images and interpreted as near-inertial internal waves based on the hydrographic data. The Along Track Interferometric SAR (ATI-SAR), utilizing two SAR antennas separated along the platform flight direction and combined interferometrically, was also tested and validated to derive ocean surface current and wave information. The phase of ATI-SAR is related to the line-of-sight velocity of the water scatterers. The surface current extraction from the ATI-SAR velocity is still an open question, because the Doppler shift is not simply proportional to the component of the mean surface current. It also includes other types of contributions associated with the phase velocity of the Bragg waves and orbital motions of all ocean waves that are longer than Bragg waves. For accurate current estimation, a new and practically useful method was developed using simultaneously measured L- and C-band ATI-SAR data. The influence of Bragg resonant waves and long ocean wave motions on the ATI-SAR velocity according to the radar-frequency was analyzed and effectively eliminated. The method was applied to NASA(JPL) L- and C-band ATI-SAR measurements. The resulting ocean surface current vectors were compared with in situ measurements collected by an RCM (Recording Current Meter). Furthermore, ocean surface wave information was extracted from the ATI-SAR data using a quasi-linear transform. The limitations of the transform were also discussed. The basic principles and the results of these multi-disciplinary observation approaches on the Earth's ocean may be extended to investigate other terrestrial planetary surface observation in the solar system. With recent launching of several fully polarimetric SAR systems such as ALOS, TerraSAR-X and RADARSAT-2, we now have the real opportunities, which we can further extend our application capabilities on Earth to other terrestrial planets.

  6. Interferometric inverse synthetic aperture radar imaging for space targets based on wideband direct sampling using two antennas

    NASA Astrophysics Data System (ADS)

    Tian, Biao; Liu, Yang; Xu, Shiyou; Chen, Zengping

    2014-01-01

    Interferometric inverse synthetic aperture radar (InISAR) imaging provides complementary information to monostatic inverse synthetic aperture radar (ISAR) imaging. This paper proposes a new InISAR imaging system for space targets based on wideband direct sampling using two antennas. The system is easy to realize in engineering since the motion trajectory of space targets can be known in advance, which is simpler than that of three receivers. In the preprocessing step, high speed movement compensation is carried out by designing an adaptive matched filter containing speed that is obtained from the narrow band information. Then, the coherent processing and keystone transform for ISAR imaging are adopted to reserve the phase history of each antenna. Through appropriate collocation of the system, image registration and phase unwrapping can be avoided. Considering the situation not to be satisfied, the influence of baseline variance is analyzed and compensation method is adopted. The corresponding size can be achieved by interferometric processing of the two complex ISAR images. Experimental results prove the validity of the analysis and the three-dimensional imaging algorithm.

  7. Monitoring deformation at The Geysers geothermal field, California using C-band and X-band Interferometric Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Vasco, D. W.; Rutqvist, J.; Dobson, P. F.; Oldenburg, C. M.; Ferretti, A.; Rucci, A.; Novali, F.; Garcia, J.; Walters, M.; Hartline, C.

    2012-12-01

    Using two distinct sets of interferometric synthetic aperture radar (InSAR) data and permanent scatterer analysis we are able to resolve deformation at The Geysers geothermal field. The first set of observations utilize archived European Space Agency (ESA) C-band synthetic aperture radar (SAR) data from 1992 through 1999 to image the long-term and large-scale subsidence in the geothermal field. The peak subsidence rate of 51.5 mm/year agrees with previous estimates from leveling and global positioning system observations. Data from a second set of measurements, acquired by a recently tasked TerraSar-X satellite, extend from May 2011 until April 2012 and overlap the C-band data spatially but not temporally. The higher frequency X-band data provides a much higher density of permanent scatters (1122 per square kilometer) than the lower frequency C-band data (12 per square kilometer) over the area surrounding an enhanced geothermal system (EGS) injection well. The EGS injection well is part of an EGS demonstration project in the northern portion of The Geysers field. The X-band InSAR observations are sensitive to some 1 to 2 cm of deformation induced by water injected into the EGS well starting in October 2011. The temporal variation of the deformation is compatible with the displacement history calculated using coupled numerical modeling of the water injection.

  8. Monitoring deformation at the Geysers Geothermal Field, California using C-band and X-band interferometric synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Vasco, D. W.; Rutqvist, Jonny; Ferretti, Alessandro; Rucci, Alessio; Bellotti, Fernando; Dobson, Patrick; Oldenburg, Curtis; Garcia, Julio; Walters, Mark; Hartline, Craig

    2013-06-01

    We resolve deformation at The Geysers Geothermal Field using two distinct sets of interferometric synthetic aperture radar (InSAR) data. The first set of observations utilize archived European Space Agency C-band synthetic aperture radar data from 1992 through 1999 to image the long-term and large-scale subsidence at The Geysers. The peak range velocity of approximately 50 mm/year agrees with previous estimates from leveling and global positioning system observations. Data from a second set of measurements, acquired by TerraSAR-X satellites, extend from May 2011 until April 2012 and overlap the C-band data spatially but not temporally. These X-band data, analyzed using a combined permanent and distributed scatterer algorithm, provide a higher density of scatterers (1122 per square kilometer) than do the C-band data (12 per square kilometer). The TerraSAR-X observations resolve 1 to 2 cm of deformation due to water injection into a Northwest Geysers enhanced geothermal system well, initiated on October 2011. The temporal variation of the deformation is compatible with estimates from coupled numerical modeling.

  9. A-Differential Synthetic Aperture Radar Interferometry analysis of a Deep Seated Gravitational Slope Deformation occurring at Bisaccia (Italy).

    PubMed

    Di Martire, Diego; Novellino, Alessandro; Ramondini, Massimo; Calcaterra, Domenico

    2016-04-15

    This paper presents the results of an investigation on a Deep Seated Gravitational Slope Deformation (DSGSD), previously only hypothesized by some authors, affecting Bisaccia, a small town located in Campania region, Italy. The study was conducted through the integration of conventional methods (geological-geomorphological field survey, air-photo interpretation) and an Advanced-Differential Interferometry Synthetic Aperture Radar (A-DInSAR) technique. The DSGSD involves a brittle lithotype (conglomerates of the Ariano Irpino Supersynthem) resting over a Structurally Complex Formation (Varycoloured Clays of Calaggio Formation). At Bisaccia, probably as a consequence of post-cyclic recompression phenomena triggered by reiterated seismic actions, the rigid plate made up of conglomeratic sediments resulted to be split in five portions, showing different rates of displacements, whose deformations are in the order of some centimeter/year, thus inducing severe damage to the urban settlement. A-DInSAR techniques confirmed to be a reliable tool in monitoring slow-moving landslides. In this case 96 ENVIronmental SATellite-Advanced Synthetic Aperture Radar (ENVISAT-ASAR) images, in ascending and descending orbits, have been processed using SUBSOFT software, developed by the Remote Sensing Laboratory (RSLab) group from the Universitat Politècnica de Catalunya (UPC). The DInSAR results, coupled with field survey, supported the analysis of the instability mechanism and confirmed the historical record of the movements already available for the town. PMID:26849321

  10. Observation of wave refraction at an ice edge by synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Vachon, Paris W.; Peng, Chih Y.

    1991-01-01

    In this note the refraction of waves at the ice edge is studied by using aircraft synthesis aperture radar (SAR). Penetration of a dominant swell from open ocean into the ice cover was observed by SAR during the Labrador Ice Margin Experiment (LIMEX), conducted on the marginal ice zone (MIZ) off the east coast of Newfoundland, Canada, in March 1987. At an ice edge with a large curvature, the dominant swell component disappeared locally in the SAR imagery. Six subscenes of waves in the MIZ from the SAR image have been processed, revealing total reflection, refraction, and energy reduction of the ocean waves by the ice cover. The observed variations of wave spectra from SAR near the ice edge are consistent with the model prediction of wave refraction at the ice edge due to the change of wave dispersion relation in ice developed by Liu and Mollo-Christensen (1988).

  11. Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report

    NASA Technical Reports Server (NTRS)

    Evans, Diane L. (Editor); Plaut, Jeffrey (Editor)

    1996-01-01

    The Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) is the most advanced imaging radar system to fly in Earth orbit. Carried in the cargo bay of the Space Shuttle Endeavour in April and October of 1994, SIR-C/X-SAR simultaneously recorded SAR data at three wavelengths (L-, C-, and X-bands; 23.5, 5.8, and 3.1 cm, respectively). The SIR-C/X-SAR Science Team consists of 53 investigator teams from more than a dozen countries. Science investigations were undertaken in the fields of ecology, hydrology, ecology, and oceanography. This report contains 44 investigator team reports and several additional reports from coinvestigators and other researchers.

  12. Impact of ground mover motion and windowing on stationary and moving shadows in synthetic aperture radar imagery

    NASA Astrophysics Data System (ADS)

    Miller, J.; Bishop, E.; Doerry, A.; Raynal, A. M.

    2015-05-01

    This paper describes the impact of ground mover motion and windowing on stationary and moving shadows in Synthetic Aperture Radar (SAR) and video SAR mode imagery. The technique provides a foundation for optimizing algorithms that detect ground movers in SAR imagery. The video SAR mode provides a persistent view of a scene centered at the Motion Compensation Point (MCP). The radar platform follows a circular flight path. Detecting a stationary shadow in a SAR image is important because the shadow indicates a detection of an object with a height component near the shadow. Similarly, the detection of a shadow that moves from frame to frame indicates the detection of a ground mover at the location of the moving shadow. An approach analyzes the impact of windowing in calculating the brightness of a pixel in a stationary, finite-sized shadow region. An extension of the approach describes the pixel brightness for a moving shadow as a function of its velocity. The pixel brightness provides an upper bound on the Probability of Detection (PD) and a lower bound on the Probability of False Alarm (PFA) for a finite-sized, stationary or moving shadow in the presence of homogeneous, ideal clutter. Synthetic data provides shadow characteristics for a radar scenario that lend themselves for detecting a ground mover. The paper presents 2011-2014 flight data collected by General Atomics Aeronautical Systems, Inc. (GA-ASI).

  13. A comparison of spatial sampling techniques enabling first principles modeling of a synthetic aperture RADAR imaging platform

    NASA Astrophysics Data System (ADS)

    Gartley, Michael; Goodenough, Adam; Brown, Scott; Kauffman, Russel P.

    2010-04-01

    Simulation of synthetic aperture radar (SAR) imagery may be approached in many different ways. One method treats a scene as a radar cross section (RCS) map and simply evaluates the radar equation, convolved with a system impulse response to generate simulated SAR imagery. Another approach treats a scene as a series of primitive geometric shapes, for which a closed form solution for the RCS exists (such as boxes, spheres and cylinders), and sums their contribution at the antenna level by again solving the radar equation. We present a ray-tracing approach to SAR image simulation that treats a scene as a series of arbitrarily shaped facetized objects, each facet potentially having a unique radio frequency optical property and time-varying location and orientation. A particle based approach, as compared to a wave based approach, presents a challenge for maintaining coherency of sampled scene points between pulses that allows the reconstruction of an exploitable image from the modeled complex phase history. We present a series of spatial sampling techniques and their relative success at producing accurate phase history data for simulations of spotlight, stripmap and SAR-GMTI collection scenarios.

  14. Two-beam coupling correlation synthetic aperture radar image recognition with power-law scattering centers pre-enhancement

    NASA Astrophysics Data System (ADS)

    Haji-saeed, Bahareh; Khoury, Jed; Woods, Charles L.; Kierstead, John

    2008-03-01

    Synthetic radar image recognition is an area of interest for military applications including automatic target recognition, air traffic control, and remote sensing. Here a dynamic range compression two-beam coupling joint transform correlator for detecting synthetic aperture radar (SAR) targets is utilized. The joint input image consists of a pre-power-law, enhanced scattering center of the input image and a linearly synthesized power-law enhanced scattering center template. Enhancing the scattering center of both the synthetic template and the input image furnishes the conditions for achieving dynamic range compression correlation in two-beam coupling. Dynamic range compression: (a) enhances the signal to noise ratio, (b) enhances the high frequencies relative to low frequencies, and (c) converts the noise to high frequency components. This improves the correlation peak intensity to the mean of the surrounding noise significantly. Dynamic range compression correlation has already been demonstrated to outperform many optimal correlation filters in detecting signals in severe noise environments. The performance is evaluated via established metrics, such as peak-to-correlation energy (PCE), Horner efficiency and correlation peak intensity. The results showed significant improvement as the power increased.

  15. Landslide Investigations at Salmon Falls Creek Canyon in Idaho Using Satellite-Based Multitemporal Interferometric Synthetic Aperture Radar Techniques

    NASA Astrophysics Data System (ADS)

    Necsoiu, M.; Hooper, D. M.; Mcginnis, R. N.

    2014-12-01

    Landslides are a common worldwide natural hazard. Due to the difficulties of preventing landslides or mitigating their impacts, it is vital to know the locations of potential slide areas and their states of activity, especially for those situations where property, infrastructure, and human lives are at risk. This study improves understanding of the rate of movement and the lateral extent of the active domain of a landslide complex within Salmon Falls Creek Canyon near Twin Falls, Idaho. The research investigates the feasibility of (i) using high-resolution multitemporal Interferometric Synthetic Aperture Radar (InSAR) techniques to detect slow, nonlinear landslide displacement, and (ii) developing a work-flow that maximizes the accuracy of InSAR techniques while minimizing the number of Synthetic Aperture Radar (SAR) datasets. The results provide (i) new insights into landslide displacement and rate of change over two decades; (ii) an assessment of change at a finer spatial resolution with similar or greater accuracy than previous studies that incorporated field and optical-based remote sensing; and (iii) improved geostatistical analysis of two separate landslides within the Salmon Falls Creek Canyon complex. These InSAR results show that the headwall block and transverse scarp had the highest mean annual velocity in the radar line-of-site direction. Line-of-site movement velocity in the toe and body of the landslide was less. Additionally, we interpret that lateral translation may have been greater in the body and toe compared to the headwall region due to the curved shape of the landside detachment surface.

  16. Status and future of laser scanning, synthetic aperture radar and hyperspectral remote sensing data for forest biomass assessment

    NASA Astrophysics Data System (ADS)

    Koch, Barbara

    2010-11-01

    This is a review of the latest developments in different fields of remote sensing for forest biomass mapping. The main fields of research within the last decade have focused on the use of small footprint airborne laser scanning systems, polarimetric synthetic radar interferometry and hyperspectral data. Parallel developments in the field of digital airborne camera systems, digital photogrammetry and very high resolution multispectral data have taken place and have also proven themselves suitable for forest mapping issues. Forest mapping is a wide field and a variety of forest parameters can be mapped or modelled based on remote sensing information alone or combined with field data. The most common information required about a forest is related to its wood production and environmental aspects. In this paper, we will focus on the potential of advanced remote sensing techniques to assess forest biomass. This information is especially required by the REDD (reducing of emission from avoided deforestation and degradation) process. For this reason, new types of remote sensing data such as fullwave laser scanning data, polarimetric radar interferometry (polarimetric systhetic aperture interferometry, PolInSAR) and hyperspectral data are the focus of the research. In recent times, a few state-of-the-art articles in the field of airborne laser scanning for forest applications have been published. The current paper will provide a state-of-the-art review of remote sensing with a particular focus on biomass estimation, including new findings with fullwave airborne laser scanning, hyperspectral and polarimetric synthetic aperture radar interferometry. A synthesis of the actual findings and an outline of future developments will be presented.

  17. Analysis of urban area land cover using SEASAT Synthetic Aperture Radar data

    NASA Technical Reports Server (NTRS)

    Henderson, F. M. (Principal Investigator)

    1980-01-01

    Digitally processed SEASAT synthetic aperture raar (SAR) imagery of the Denver, Colorado urban area was examined to explore the potential of SAR data for mapping urban land cover and the compatability of SAR derived land cover classes with the United States Geological Survey classification system. The imagery is examined at three different scales to determine the effect of image enlargement on accuracy and level of detail extractable. At each scale the value of employing a simplistic preprocessing smoothing algorithm to improve image interpretation is addressed. A visual interpretation approach and an automated machine/visual approach are employed to evaluate the feasibility of producing a semiautomated land cover classification from SAR data. Confusion matrices of omission and commission errors are employed to define classification accuracies for each interpretation approach and image scale.

  18. Inverse synthetic aperture radar processing using parametric time-frequency estimators Phase I

    SciTech Connect

    Candy, J.V., LLNL

    1997-12-31

    This report summarizes the work performed for the Office of the Chief of Naval Research (ONR) during the period of 1 September 1997 through 31 December 1997. The primary objective of this research was aimed at developing an alternative time-frequency approach which is recursive-in-time to be applied to the Inverse Synthethic Aperture Radar (ISAR) imaging problem discussed subsequently. Our short term (Phase I) goals were to: 1. Develop an ISAR stepped-frequency waveform (SFWF) radar simulator based on a point scatterer vehicular target model incorporating both translational and rotational motion; 2. Develop a parametric, recursive-in-time approach to the ISAR target imaging problem; 3. Apply the standard time-frequency short-term Fourier transform (STFT) estimator, initially to a synthesized data set; and 4. Initiate the development of the recursive algorithm. We have achieved all of these goals during the Phase I of the project and plan to complete the overall development, application and comparison of the parametric approach to other time-frequency estimators (STFT, etc.) on our synthesized vehicular data sets during the next phase of funding. It should also be noted that we developed a batch minimum variance translational motion compensation (TMC) algorithm to estimate the radial components of target motion (see Section IV). This algorithm is easily extended to recursive solution and will probably become part of the overall recursive processing approach to solve the ISAR imaging problem. Our goals for the continued effort are to: 1. Develop and extend a complex, recursive-in-time, time- frequency parameter estimator based on the recursive prediction error method (RPEM) using the underlying Gauss- Newton algorithms. 2. Apply the complex RPEM algorithm to synthesized ISAR data using the above simulator. 3. Compare the performance of the proposed algorithm to standard time-frequency estimators applied to the same data sets.

  19. Short-range verification experiment of a trial one-dimensional synthetic aperture infrared laser radar operated in the 10-microm band.

    PubMed

    Yoshikado, S; Aruga, T

    2000-03-20

    A trial one-dimensional (1-D) synthetic aperture infrared laser radar (SAILR) system for imaging static objects, with two CO(2) lasers as a transmitter and a local oscillator for heterodyne detection, was constructed. It has a single receiving aperture mounted on a linearly movable stage with a length of 1 m and a position accuracy of 1 microm. In an indoor short-range experiment to confirm the fundamental functions of the system and demonstrate its unique imaging process we succeeded in obtaining 1-D synthetic aperture images of close specular point targets with theoretically expected resolution. PMID:18338026

  20. Investigating the backscatter contrast anomaly in synthetic aperture radar (SAR) imagery of the dunes along the Israel-Egypt border

    NASA Astrophysics Data System (ADS)

    Rozenstein, Offer; Siegal, Zehava; Blumberg, Dan G.; Adamowski, Jan

    2016-04-01

    The dune field intersected by the Israel-Egypt borderline has attracted many remote sensing studies over the years because it exhibits unique optical phenomena in several domains, from the visual to the thermal infrared. These phenomena are the result of land-use policies implemented by the two countries, which have differing effects on the two ecosystems. This study explores the surface properties that affect radar backscatter, namely the surface roughness and dielectric properties, in order to determine the cause for the variation across the border. The backscatter contrast was demonstrated for SIR-C, the first synthetic aperture radar (SAR) sensor to capture this phenomenon, as well as ASAR imagery that coincides with complementary ground observations. These field observations along the border, together with an aerial image from the same year as the SIR-C acquisition were used to analyze differences in vegetation patterns that can affect the surface roughness. The dielectric permittivity of two kinds of topsoil (sand, biocrust) was measured in the field and in the laboratory. The results suggest that the vegetation structure and spatial distribution differ between the two sides of the border in a manner that is consistent with the radar observations. The dielectric permittivity of sand and biocrust was found to be similar, although they are not constant across the radar spectral region (50 MHz-20 GHz). These findings support the hypothesis that changes to the vegetation, as a consequence of the different land-use practices in Israel and Egypt, are the cause for the radar backscatter contrast across the border.

  1. Three-dimensional subsurface imaging synthetic aperture radar (3D SISAR). Final report, September 22, 1993--September 22, 1996

    SciTech Connect

    1998-12-31

    The concept developed under this applied research and development contract is a novel Ground Penetrating Radar system capable of remotely detecting, analyzing, and mapping buried waste containers from a mobile platform. From the testing and analysis performed to date, the 3-D SISAR has achieved the detection, accurate location, and three-dimensional imaging of buried test objects from a stand-off geometry. Tests have demonstrated that underground objects have been located to within 0.1 meter of their actual position. This work validates that the key elements of the approach are performing as anticipated. The stand-off synthetic aperture radar (SAR) methodology has been demonstrated to be a feasible approach as a remote sensing technique. The radar sensor constructed under this project is providing adequate quality data for imaging, and the matched filters have been demonstrated to provide enhanced target detection. Additional work is on-going in the area of underground propagation and scattering phenomena to provide enhanced depth performance, as the current imaging results have been limited to a few feet of depth underground.

  2. Characterization of L-band synthetic aperture radar (SAR) backscatter from floating and grounded thermokarst lake ice in Arctic Alaska

    NASA Astrophysics Data System (ADS)

    Engram, M.; Anthony, K. W.; Meyer, F. J.; Grosse, G.

    2013-11-01

    Radar remote sensing is a well-established method to discriminate lakes retaining liquid-phase water beneath winter ice cover from those that do not. L-band (23.6 cm wavelength) airborne radar showed great promise in the 1970s, but spaceborne synthetic aperture radar (SAR) studies have focused on C-band (5.6 cm) SAR to classify lake ice with no further attention to L-band SAR for this purpose. Here, we examined calibrated L-band single- and quadrature-polarized SAR returns from floating and grounded lake ice in two regions of Alaska: the northern Seward Peninsula (NSP) where methane ebullition is common in lakes and the Arctic Coastal Plain (ACP) where ebullition is relatively rare. We found average backscatter intensities of -13 dB and -16 dB for late winter floating ice on the NSP and ACP, respectively, and -19 dB for grounded ice in both regions. Polarimetric analysis revealed that the mechanism of L-band SAR backscatter from floating ice is primarily roughness at the ice-water interface. L-band SAR showed less contrast between floating and grounded lake ice than C-band; however, since L-band is sensitive to ebullition bubbles trapped by lake ice (bubbles increase backscatter), this study helps elucidate potential confounding factors of grounded ice in methane studies using SAR.

  3. The evolution of convective storms from their footprints on the sea as viewed by synthetic aperture radar from space

    NASA Technical Reports Server (NTRS)

    Atlas, David; Black, Peter G.

    1994-01-01

    SEASAT synthetic aperture radar (SAR) echoes from the sea have previously been shown to be the result of rain and winds produced by convective stroms; rain damps the surface waves and causes ech-free holes, while the diverging winds associated with downdraft generate waves and associated echoes surrounding the holes. Gust fronts are also evident. Such a snapshot from 8 July 1978 has been examined in conjunction with ground-based radar. This leads to the conclusion that the SAR storm footprints resulted from storm processes that occurred up to an hour or more prior to the snapshot. A sequence of events is discerned from the SAR imagery in which new cell growth is triggered in between the converging outflows of two preexisting cells. In turn, the new cell generates a mini-squall line along its expanding gust front. While such phenomena are well known over land, the spaceborne SAR now allows important inferences to be made about the nature and frequency of convective storms over the oceans. The storm effects on the sea have significant implications for spaceborne wind scatterometry and rainfall measurements. Some of the findings herein remain speculative because of the great distance to the Miami weather radar-the only source of corroborative data.

  4. Image registration of interferometric inverse synthetic aperture radar imaging system based on joint respective window sampling and modified motion compensation

    NASA Astrophysics Data System (ADS)

    Tian, Biao; Shi, Si; Liu, Yang; Xu, Shiyou; Chen, Zengping

    2015-01-01

    We propose a new image registration method based on joint respective window sampling (RWS) and modified motion compensation (MMC) in an interferometric inverse synthetic aperture radar (InISAR) imaging system using two antennas. The causation and quantitative analysis of the offset between two ISAR images of different antennas along the baseline are analyzed. In the proposed method, the RWS method, according to the measured distance between the target and different antennas, compensates the offset in the range direction. The MMC method is adopted to eliminate the offset in the Doppler direction. Simulation results demonstrate that the offset between the two ISAR images can be compensated effectively, consequently achieving a high-quality three-dimensional InISAR image.

  5. Inversion of synthetic aperture radar interferograms for sourcesof production-related subsidence at the Dixie Valley geothermalfield

    SciTech Connect

    Foxall, B.; Vasco, D.W.

    2006-07-01

    We used synthetic aperture radar interferograms to imageground subsidence that occurred over the Dixie Valley geothermal fieldduring different time intervals between 1992 and 1997. Linear elasticinversion of the subsidence that occurred between April, 1996 and March,1997 revealed that the dominant sources of deformation during this timeperiod were large changes in fluid volumes at shallow depths within thevalley fill above the reservoir. The distributions of subsidence andsubsurface volume change support a model in which reduction in pressureand volume of hot water discharging into the valley fill from localizedupflow along the Stillwater range frontal fault is caused by drawdownwithin the upflow zone resulting from geothermal production. Our resultsalso suggest that an additional source of fluid volume reduction in theshallow valley fill might be similar drawdown within piedmont faultzones. Shallow groundwater flow in the vicinity of the field appears tobe controlled on the NW by a mapped fault and to the SW by a lineament ofas yet unknown origin.

  6. Reservoir monitoring and characterization using satellite geodetic data: Interferometric Synthetic Aperture Radar observations from the Krechba field, Algeria

    SciTech Connect

    Vasco, D.W.; Ferretti, Alessandro; Novali, Fabrizio

    2008-05-01

    Deformation in the material overlying an active reservoir is used to monitor pressure change at depth. A sequence of pressure field estimates, eleven in all, allow us to construct a measure of diffusive travel time throughout the reservoir. The dense distribution of travel time values means that we can construct an exactly linear inverse problem for reservoir flow properties. Application to Interferometric Synthetic Aperture Radar (InSAR) data gathered over a CO{sub 2} injection in Algeria reveals pressure propagation along two northwest trending corridors. An inversion of the travel times indicates the existence of two northwest-trending high permeability zones. The high permeability features trend in the same direction as the regional fault and fracture zones. Model parameter resolution estimates indicate that the features are well resolved.

  7. Linear dispersion relation and depth sensitivity to swell parameters: application to synthetic aperture radar imaging and bathymetry.

    PubMed

    Boccia, Valentina; Renga, Alfredo; Rufino, Giancarlo; D'Errico, Marco; Moccia, Antonio; Aragno, Cesare; Zoffoli, Simona

    2015-01-01

    Long gravity waves or swell dominating the sea surface is known to be very useful to estimate seabed morphology in coastal areas. The paper reviews the main phenomena related to swell waves propagation that allow seabed morphology to be sensed. The linear dispersion is analysed and an error budget model is developed to assess the achievable depth accuracy when Synthetic Aperture Radar (SAR) data are used. The relevant issues and potentials of swell-based bathymetry by SAR are identified and discussed. This technique is of particular interest for characteristic regions of the Mediterranean Sea, such as in gulfs and relatively close areas, where traditional SAR-based bathymetric techniques, relying on strong tidal currents, are of limited practical utility. PMID:25789333

  8. Linear Dispersion Relation and Depth Sensitivity to Swell Parameters: Application to Synthetic Aperture Radar Imaging and Bathymetry

    PubMed Central

    Boccia, Valentina; Renga, Alfredo; Rufino, Giancarlo; D'Errico, Marco; Moccia, Antonio; Aragno, Cesare; Zoffoli, Simona

    2015-01-01

    Long gravity waves or swell dominating the sea surface is known to be very useful to estimate seabed morphology in coastal areas. The paper reviews the main phenomena related to swell waves propagation that allow seabed morphology to be sensed. The linear dispersion is analysed and an error budget model is developed to assess the achievable depth accuracy when Synthetic Aperture Radar (SAR) data are used. The relevant issues and potentials of swell-based bathymetry by SAR are identified and discussed. This technique is of particular interest for characteristic regions of the Mediterranean Sea, such as in gulfs and relatively close areas, where traditional SAR-based bathymetric techniques, relying on strong tidal currents, are of limited practical utility. PMID:25789333

  9. Automatic target classification of man-made objects in synthetic aperture radar images using Gabor wavelet and neural network

    NASA Astrophysics Data System (ADS)

    Vasuki, Perumal; Roomi, S. Mohamed Mansoor

    2013-01-01

    Processing of synthetic aperture radar (SAR) images has led to the development of automatic target classification approaches. These approaches help to classify individual and mass military ground vehicles. This work aims to develop an automatic target classification technique to classify military targets like truck/tank/armored car/cannon/bulldozer. The proposed method consists of three stages via preprocessing, feature extraction, and neural network (NN). The first stage removes speckle noise in a SAR image by the identified frost filter and enhances the image by histogram equalization. The second stage uses a Gabor wavelet to extract the image features. The third stage classifies the target by an NN classifier using image features. The proposed work performs better than its counterparts, like K-nearest neighbor (KNN). The proposed work performs better on databases like moving and stationary target acquisition and recognition against the earlier methods by KNN.

  10. Airborne synthetic aperture acoustic imaging.

    PubMed

    Soumekh, M

    1997-01-01

    This paper presents a system model and inversion for airborne synthetic aperture acoustic (SAA) imaging. The system model accurately represents the intercation of the acoustic source and the target region at near range values. Moreover, the model incorporates the fact that the relative speed of the vehicle's (transmitter/receiver) with respect to the target region is comparable to the acoustic wave propagation speed. The inversion utilizes the principle of spectral decomposition of spherical phase functions to develop a wavefront reconstruction method from SAA data. Processing issues and selection of appropriate acoustic FM-CW sources are discussed. Results are provided that exhibit the superior accuracy of the proposed SAA system model and inversion over their synthetic aperture radar (SAR) counterpart in which the vehicle's speed is assumed to be much smaller than the wave propagation speed. PMID:18282912

  11. Joint use of multiple Synthetic Aperture Radar imagery for the detection of bivalve beds and morphological changes on intertidal flats

    NASA Astrophysics Data System (ADS)

    Gade, Martin; Melchionna, Sabrina

    2016-03-01

    We analyzed a large amount of high-resolution Synthetic Aperture Radar (SAR) data of dry-fallen intertidal flats on the German North Sea coast with respect to the imaging of sediments, macrophytes, and mussels. TerraSAR-X and Radarsat-2 images of four test areas acquired from 2008 to 2013 form the basis for the present investigation and are used to demonstrate that pairs of SAR images, if combined through basic algebraic operations, can already provide indicators for morphological changes and for bivalve (oyster and mussel) beds. Multi-temporal analyses of series of SAR images allow detecting bivalve beds, since the radar backscattering from those beds is generally high, whereas that from sediments may vary with imaging geometry and environmental conditions. Our results further show evidence that also single-acquisition, dual-polarization SAR imagery can be used in this respect. The polarization coefficient (i.e., the ratio of the difference and the sum of both co-polarizations) can be used to infer indicators for oyster and blue-mussel beds.

  12. Investigating ground deformation and subsidence in northern Metro Manila, Philippines using Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR)

    NASA Astrophysics Data System (ADS)

    Eco, R. C.; Lagmay, A. A.; Bato, M. P.

    2011-12-01

    The extent of ground deformation and subsidence in northern Metro Manila was examined using Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR) technique. Using the Stanford Method for Persistent Scatterers/Multi-Temporal InSAR (StaMPS/MTI) software, we processed 21 descending ENVISAT radar imageries taken from 2003 to 2006. The processed interferograms show high coherence due to the high density of PS points in the region of interest. The PSInSAR processing reveals several areas in northern Metro Manila, specifically in Caloocan, Malabon, Navotas and Valenzuela-collectively known as CAMANAVA-that exhibit deformation characteristics similar to that of ground subsidence. Results show that the areas manifesting apparent subsidence are moving with a maximum rate of 4.38 cm/year relative to the satellite. This is consistent with the geodetic surveying results from 1979 to 2009 showing subsidence of approximately 1 meter or 3.33 cm/year per year. Government data also identify these areas as among those with the highest rates of groundwater extraction in Metro Manila, suggesting the possibility of anthropogenic activities as the major cause of subsidence. With this study, we hope to get a better understanding of the nature of subsidence affecting parts of northern Metro Manila. Doing so would help mitigate the effects of potential flood disasters.

  13. Retrieval and Evaluation of Wind Vectors and Advective Surface Velocities from Synthetic Aperture Radar and Infrared Radiometer Data

    NASA Astrophysics Data System (ADS)

    Carvajal, Gisela; Eriksson, Leif E. B.

    Analysis of ocean surface dynamics has been proven to be of vital importance in many areas (e.g. shipping, fishing). Two important parameters to describe the ocean dynamics are the wind velocity (speed and direction) and advective surface velocities (ocean current velocity). These parameters are currently provided operationally by forecast models, surface sensors (e.g. buoys, coastal radar) and satellite sensors. However, coverage limitations, low resolution and limited temporal availability impose a need for implementation and evaluation of new data sources and techniques for estimation of these parameters. In this paper we implement and evaluate known techniques for determination of wind and ocean current velocity from satellite data. Wind is determined from Synthetic Aperture Radar (SAR) data by applying two algo-rithms. First, the Local Gradient method is implemented to extract wind direction from the SAR data, and then the CMOD-5 Geophysical Model Function of the backscatter is inverted to obtain the wind speed as a function of the wind direction and the incidence angle. Current propagation is estimated by analyzing the Sea Surface Temperature propagation in two consec-utive infrared images of the same area from the Advanced Very High Resolution Radiometer. The evaluation shows a good agreement between estimated wind vectors from SAR and scat-terometer data. Comparison with merged ocean current estimates is addressed. The methods will be implemented in the maritime security service provided by the SECTRONIC project funded by the EU 7th framework program.

  14. Tracking lava flow emplacement on the east rift zone of Kilauea, Hawai’i with synthetic aperture radar (SAR) coherence

    USGS Publications Warehouse

    Dietterich, Hannah R.; Poland, Michael P.; Schmidt, David; Cashman, Katharine V.; Sherrod, David R.; Espinosa, Arkin Tapia

    2012-01-01

    Lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior. Although maps are traditionally created through field surveys, remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location. Synthetic aperture radar (SAR) imagery, in particular, can detect changes in a flow field by comparing two images collected at different times with SAR coherence. New lava flows radically alter the scattering properties of the surface, making the radar signal decorrelated in SAR coherence images. We describe a new technique, SAR Coherence Mapping (SCM), to map lava flows automatically from coherence images independent of look angle or satellite path. We use this approach to map lava flow emplacement during the Pu‘u ‘Ō‘ō-Kupaianaha eruption at Kīlauea, Hawai‘i. The resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows, as well as the locations of active flow paths. However, the SCM technique is only moderately successful at mapping flows that enter vegetation, which is also often decorrelated between successive SAR images. Along with measurements of planform morphology, we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness. Finally, we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post-emplacement flow subsidence.

  15. Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California

    USGS Publications Warehouse

    Galloway, D.L.; Hudnut, K.W.; Ingebritsen, S.E.; Phillips, S.P.; Peltzer, G.; Rogez, F.; Rosen, P.A.

    1998-01-01

    Interferometric synthetic aperture radar (InSAR) has great potential to detect and quantify land subsidence caused by aquifer system compaction. InSAR maps with high spatial detail and resolution of range displacement (??10 mm in change of land surface elevation) were developed for a groundwater basin (~103 km2) in Antelope Valley, California, using radar data collected from the ERS-1 satellite. These data allow comprehensive comparison between recent (1993-1995) subsidence patterns and those detected historically (1926-1992) by more traditional methods. The changed subsidence patterns are generally compatible with recent shifts in land and water use. The InSAR-detected patterns are generally consistent with predictions based on a coupled model of groundwater flow and aquifer system compaction. The minor inconsistencies may reflect our imperfect knowledge of the distribution and properties of compressible sediments. When used in conjunction with coincident measurements of groundwater levels and other geologic information, InSAR data may be useful for constraining parameter estimates in simulations of aquifer system compaction.

  16. Seasonal sea ice melt pond fraction and pond freezing estimation using dual-polarisation C-band synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Scharien, R. K.; Landy, J.; Howell, S.; Warner, K.; Barber, D. G.

    2014-12-01

    Sea ice melt ponds play an important role in spring-summer radiation absorption and upper ocean warming, light transmittance and under-ice primary production, and biogeochemical exchanges. With a larger portion of Arctic first-year sea ice (FYI) compared to multiyear ice observed in recent years comes the expectation of greater melt pond fraction due to the absence of topographical controls on FYI. Despite progress in our understanding and modelling of pond fraction evolution and coupled processes at the local scale, a reliable means for monitoring variations at regional or greater scales, uninhibited by cloud cover, is lacking. In this study we demonstrate the ability of dual-polarisation C-band synthetic aperture radar (SAR) for estimating pond fraction and freezing conditions on level FYI in the Canadian Arctic Archipelago. We use a combination of in situ C-band scatterometer and radar-scale surface roughness observations to study the dual-polarisation channel (VV+HH and HV+HH) and channel ratio characteristics of individual melt ponds and ice patches. Aerial surveys of pond fraction are used to evaluate retrieval approaches from Radarsat-2 SAR fine quad-polarisation mode imagery. Accurate retrievals of pond fraction are found using the VV/HH polarisation ratio during melting conditions. Results demonstrate the potential of dual-polarisation SAR for regional scale observations with temporal frequency suitable for contributing to process-scale studies and improvements to model parameterizations.

  17. Road-Aided Ground Slowly Moving Target 2D Motion Estimation for Single-Channel Synthetic Aperture Radar

    PubMed Central

    Wang, Zhirui; Xu, Jia; Huang, Zuzhen; Zhang, Xudong; Xia, Xiang-Gen; Long, Teng; Bao, Qian

    2016-01-01

    To detect and estimate ground slowly moving targets in airborne single-channel synthetic aperture radar (SAR), a road-aided ground moving target indication (GMTI) algorithm is proposed in this paper. First, the road area is extracted from a focused SAR image based on radar vision. Second, after stationary clutter suppression in the range-Doppler domain, a moving target is detected and located in the image domain via the watershed method. The target’s position on the road as well as its radial velocity can be determined according to the target’s offset distance and traffic rules. Furthermore, the target’s azimuth velocity is estimated based on the road slope obtained via polynomial fitting. Compared with the traditional algorithms, the proposed method can effectively cope with slowly moving targets partly submerged in a stationary clutter spectrum. In addition, the proposed method can be easily extended to a multi-channel system to further improve the performance of clutter suppression and motion estimation. Finally, the results of numerical experiments are provided to demonstrate the effectiveness of the proposed algorithm. PMID:26999140

  18. Road-Aided Ground Slowly Moving Target 2D Motion Estimation for Single-Channel Synthetic Aperture Radar.

    PubMed

    Wang, Zhirui; Xu, Jia; Huang, Zuzhen; Zhang, Xudong; Xia, Xiang-Gen; Long, Teng; Bao, Qian

    2016-01-01

    To detect and estimate ground slowly moving targets in airborne single-channel synthetic aperture radar (SAR), a road-aided ground moving target indication (GMTI) algorithm is proposed in this paper. First, the road area is extracted from a focused SAR image based on radar vision. Second, after stationary clutter suppression in the range-Doppler domain, a moving target is detected and located in the image domain via the watershed method. The target's position on the road as well as its radial velocity can be determined according to the target's offset distance and traffic rules. Furthermore, the target's azimuth velocity is estimated based on the road slope obtained via polynomial fitting. Compared with the traditional algorithms, the proposed method can effectively cope with slowly moving targets partly submerged in a stationary clutter spectrum. In addition, the proposed method can be easily extended to a multi-channel system to further improve the performance of clutter suppression and motion estimation. Finally, the results of numerical experiments are provided to demonstrate the effectiveness of the proposed algorithm. PMID:26999140

  19. An Interferometric Ka-band Synthetic Aperture Radar: A New Technique for Glacier and Ice- sheet Topography Mapping

    NASA Astrophysics Data System (ADS)

    Moller, D. K.; Aaron, K.; Gim, Y.; Heavey, B.; Hodges, R.; Nicolson, A.; Rengarajan, S.; Rignot, E.; Rogez, F.; Sadowy, G.; Simard, M.; Zawadzki, M.

    2006-12-01

    The estimation of the mass balance of ice sheets and glaciers on Earth is a problem of considerable scientific and societal importance. The Greenland and Antarctic ice sheets together hold enough ice to raise global sea level by 80 m. The annual exchange of mass on the ice sheets is equivalent to 8mm/yr sea level, so that any fluctuation in that level of exchange is significant on the global scale. A key measurement to understanding, monitoring and forecasting these changes is ice-surface topography, both for ice-sheet and glacial regions. As such NASA identified "ice topographic mapping instruments capable of providing precise elevation and detailed imagery data for measurements on glacial scales for detailed monitoring of ice sheet, and glacier changes" as a science priority for the most recent ESTO- Instrument Incubator Program (IIP) opportunities. Funded under this opportunity is the technological development for a Ka-Band (35GHz) single-pass digitally beamformed interferometric synthetic aperture radar (InSAR). Unique to this concept is the ability to map a significant swath impervious of cloud cover with measurement accuracies comparable to lidar altimeters but with variable resolution as appropriate to the differing scales-of-interest over ice-sheets and glaciers. By diverging from the more traditional profiling measurements employed to date (ie radar altimeters and lidars) we are able to offer the potential to significantly advance the spaciotemporal observational capabilities of both ice sheets and glaciers. Dubbed the Glacier and Land Ice Surface Topography Interferometer (GLISTIN), the instrument and mission presents several significant challenges. In particular, under the IIP program we are designing, building and demonstrating a large Ka-band antenna array with integrated digital receivers and utilizing digital beamforming to preserve both antenna gain and swath. These technology items will ultimately be integrated into a complete interferometric ground-based system and demonstrated from the local JPL mesa antenna range. While the demonstration addresses the key technology hurdles, an additional component to this program is to address the systematic and geophysical calibration issues that will arise for a dedicated mission of this type. We discuss our proposed calibration methodology and present several of the critical issues, including correction of systematic errors and surface and volume decorrelation effects. We conclude with a discussion of the impact of snow penetration on the height measurements, and discuss a proposed campaign to field a Ka-band interferometric synthetic aperture radar based on the Jet Propulsion Laboratory's new "UAVSAR" platform.

  20. Detecting Faults in Southern California using Computer-Vision Techniques and Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) Interferometry

    NASA Astrophysics Data System (ADS)

    Barba, M.; Rains, C.; von Dassow, W.; Parker, J. W.; Glasscoe, M. T.

    2013-12-01

    Knowing the location and behavior of active faults is essential for earthquake hazard assessment and disaster response. In Interferometric Synthetic Aperture Radar (InSAR) images, faults are revealed as linear discontinuities. Currently, interferograms are manually inspected to locate faults. During the summer of 2013, the NASA-JPL DEVELOP California Disasters team contributed to the development of a method to expedite fault detection in California using remote-sensing technology. The team utilized InSAR images created from polarimetric L-band data from NASA's Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) project. A computer-vision technique known as 'edge-detection' was used to automate the fault-identification process. We tested and refined an edge-detection algorithm under development through NASA's Earthquake Data Enhanced Cyber-Infrastructure for Disaster Evaluation and Response (E-DECIDER) project. To optimize the algorithm we used both UAVSAR interferograms and synthetic interferograms generated through Disloc, a web-based modeling program available through NASA's QuakeSim project. The edge-detection algorithm detected seismic, aseismic, and co-seismic slip along faults that were identified and compared with databases of known fault systems. Our optimization process was the first step toward integration of the edge-detection code into E-DECIDER to provide decision support for earthquake preparation and disaster management. E-DECIDER partners that will use the edge-detection code include the California Earthquake Clearinghouse and the US Department of Homeland Security through delivery of products using the Unified Incident Command and Decision Support (UICDS) service. Through these partnerships, researchers, earthquake disaster response teams, and policy-makers will be able to use this new methodology to examine the details of ground and fault motions for moderate to large earthquakes. Following an earthquake, the newly discovered faults can be paired with infrastructure overlays, allowing emergency response teams to identify sites that may have been exposed to damage. The faults will also be incorporated into a database for future integration into fault models and earthquake simulations, improving future earthquake hazard assessment. As new faults are mapped, they will further understanding of the complex fault systems and earthquake hazards within the seismically dynamic state of California.

  1. Differential synthetic aperture radar interferometry for landslide monitoring: a priori GIS based assessment of feasibility

    NASA Astrophysics Data System (ADS)

    Plank, S.; Singer, J.; Minet, Ch.; Thuro, K.

    2012-04-01

    In the last two decades differential radar interferometry (D-InSAR) has proven to be a powerful remote sensing technique for detection and deformation monitoring of landslides with an accuracy of a few millimeters. However, due to the inclined imaging geometry, areas with a topographic relief (where landslides usually occur) appear heavily distorted in the radar image. Thereby slopes inclined towards the radar sensor appear shortened (foreshortening) and in extreme even can cause an overlapping of different radar signals (layover effect); slopes oriented away from the radar seem stretched (elongation) or even can be shadowed by a steep mountain (shadowing). These effects limit or even prohibit the use of a radar image for interferometric applications. Besides these geometric distortions, the land cover has great influence on the applicability of differential radar interferometry. For example vegetation-free areas such as buildings and rocks show high coherence values over a long time period (high stability of their backscattering properties), whereas areas covered by vegetation, especially forests, have varying backscattering properties at different times (e.g. due to wind; temporal decorrelation). Areas with high coherence values in the radar interferogram are better suited for D-InSAR applications. To date prior to an investigation using D-InSAR these limiting effects usually are only roughly estimated, sometimes leading to disappointing results when the actual radar images are analyzed. Therefore we present a GIS routine, which based on freely available digital elevation model (DEM) data (SRTM) not only accurately predicts the areas in which layover and shadowing will occur, but also determines the percentage of measurability of the movement of a landslide (portion oriented in radar line of sight) for a given radar acquisition geometry. Additionally land cover classification data (e.g. CORINE) is used to evaluate the influence of the landslide's land cover on D-InSAR deformation measurements. This GIS routine is very flexible as each type of DEM data and land cover data available for the area of interest can be used. For instance by using a high resolution lasercan DEM, we were able to show a very high accurate prediction of areas affected by layover and shadowing, even exceeding the accuracy of the layover/shadow calculations of DLR's standard method (Geocoded Incidence Angle Mask). Thus by using this new GIS application, it is possible to assess the feasibility of D-InSAR landslide deformation measurements in a certain region quite accurately prior to the expensive actual radar data is ordered.

  2. Development of NASA's Next Generation L-Band Digital Beamforming Synthetic Aperture Radar (DBSAR-2)

    NASA Technical Reports Server (NTRS)

    Rincon, Rafael; Fatoyinbo, Temilola; Osmanoglu, Batuhan; Lee, Seung-Kuk; Ranson, K. Jon; Marrero, Victor; Yeary, Mark

    2014-01-01

    NASA's Next generation Digital Beamforming SAR (DBSAR-2) is a state-of-the-art airborne L-band radar developed at the NASA Goddard Space Flight Center (GSFC). The instrument builds upon the advanced architectures in NASA's DBSAR-1 and EcoSAR instruments. The new instrument employs a 16-channel radar architecture characterized by multi-mode operation, software defined waveform generation, digital beamforming, and configurable radar parameters. The instrument has been design to support several disciplines in Earth and Planetary sciences. The instrument was recently completed, and tested and calibrated in a anechoic chamber.

  3. A method for constraining canopy height using single-polarization L-band Interferometric Synthetic Aperture Radar (InSAR)

    NASA Astrophysics Data System (ADS)

    Prush, V. B.; Lohman, R.

    2012-12-01

    Over the past two decades, interferometric synthetic aperture radar (InSAR) has proven to be a useful technique for observing a wide range of sources of crustal motion, including groundwater extraction and deformation related to volcanic processes and earthquakes. In this study we introduce a new method for the application of InSAR to the determination of canopy height in forests where extensive clearcutting has occurred. Our region of study is the Pacific Northwest, specifically Washington and Oregon, where clearcutting has been a common logging technique since the earliest days of the timber industry in the region. We analyzed twenty-nine interferograms of the Pacific Northwest in this study. The interferograms were processed using single-polarization Synthetic Aperture Radar (SAR) data acquired by the Advanced Land Observation Satellite (ALOS). ALOS data is acquired at L-band (~24 cm), which provides high coherence in a region that is heavily forested and has high relief. Regions that have undergone clearcutting within the past 10 to 15 years are characterized in the interferograms by quasi-rectangular regions of line-of-sight phase change between clearcuts and the surrounding standing forest. This phase difference correlates linearly with interferometric baseline, allowing us to attribute the observed phase difference between clearcut areas and standing forest to an effective digital elevation model (DEM) error. By focusing only on the phase change over the short spatial scale between standing forest and adjacent regions that have been logged, we remove the effect of longer spatial scale atmospheric noise and satellite orbital errors. A ratio of Landsat 5 Thematic Mapper (TM) bands 2 and 7 (0.52-0.60 and 2.08-2.35 μm, respectively) was used to identify and remove areas that were logged during the timespan of the SAR data (2007 to 2011). We present a map of canopy height throughout the western coast of Oregon and Washington. Observed canopy heights are consistent with local ground surveys and previous remote-sensing studies. Our methods provide an independent measurement of canopy height and will aid in ongoing efforts to constrain the global carbon budget. Estimates of canopy height will likely be improved by the addition of new data through the advent of the next generation of SAR missions, such as the proposed DESDynI mission. These methods will also be useful for removing a prominent non-tectonic signal observed in the Pacific Northwest so that InSAR data will be of more utility in forthcoming tectonic studies.

  4. SAR (Synthetic Aperture Radar). Earth observing system. Volume 2F: Instrument panel report

    NASA Technical Reports Server (NTRS)

    1987-01-01

    The scientific and engineering requirements for the Earth Observing System (EOS) imaging radar are provided. The radar is based on Shuttle Imaging Radar-C (SIR-C), and would include three frequencies: 1.25 GHz, 5.3 GHz, and 9.6 GHz; selectable polarizations for both transmit and receive channels; and selectable incidence angles from 15 to 55 deg. There would be three main viewing modes: a local high-resolution mode with typically 25 m resolution and 50 km swath width; a regional mapping mode with 100 m resolution and up to 200 km swath width; and a global mapping mode with typically 500 m resolution and up to 700 km swath width. The last mode allows global coverage in three days. The EOS SAR will be the first orbital imaging radar to provide multifrequency, multipolarization, multiple incidence angle observations of the entire Earth. Combined with Canadian and Japanese satellites, continuous radar observation capability will be possible. Major applications in the areas of glaciology, hydrology, vegetation science, oceanography, geology, and data and information systems are described.

  5. Automatic position calculating imaging radar with low-cost synthetic aperture sensor for imaging layered media

    DOEpatents

    Mast, Jeffrey E.

    1998-01-01

    An imaging system for analyzing structures comprises a radar transmitter and receiver connected to a timing mechanism that allows a radar echo sample to be taken at a variety of delay times for each radar pulse transmission. The radar transmitter and receiver are coupled to a position determining system that provides the x,y position on a surface for each group of samples measured for a volume from the surface. The radar transmitter and receiver are moved about the surface to collect such groups of measurements from a variety of x,y positions. Return signal amplitudes represent the relative reflectivity of objects within the volume and the delay in receiving each signal echo represents the depth at which the object lays in the volume and the propagation speeds of the intervening material layers. Successively deeper z-planes are backward propagated from one layer to the next with an adjustment for variations in the expected propagation velocities of the material layers that lie between adjacent z-planes.

  6. Automatic position calculating imaging radar with low-cost synthetic aperture sensor for imaging layered media

    DOEpatents

    Mast, J.E.

    1998-08-18

    An imaging system for analyzing structures comprises a radar transmitter and receiver connected to a timing mechanism that allows a radar echo sample to be taken at a variety of delay times for each radar pulse transmission. The radar transmitter and receiver are coupled to a position determining system that provides the x,y position on a surface for each group of samples measured for a volume from the surface. The radar transmitter and receiver are moved about the surface to collect such groups of measurements from a variety of x,y positions. Return signal amplitudes represent the relative reflectivity of objects within the volume and the delay in receiving each signal echo represents the depth at which the object lays in the volume and the propagation speeds of the intervening material layers. Successively deeper z-planes are backward propagated from one layer to the next with an adjustment for variations in the expected propagation velocities of the material layers that lie between adjacent z-planes. 10 figs.

  7. Inverse synthetic aperture radar imagery of a man with a rocket propelled grenade launcher

    NASA Astrophysics Data System (ADS)

    Tran, Chi N.; Innocenti, Roberto; Kirose, Getachew; Ranney, Kenneth I.; Smith, Gregory

    2004-08-01

    As the Army moves toward more lightly armored Future Combat System (FCS) vehicles, enemy personnel will present an increasing threat to U.S. soldiers. In particular, they face a very real threat from adversaries using shoulder-launched, rocket propelled grenade (RPG). The Army Research Laboratory has utilized its Aberdeen Proving Ground (APG) turntable facility to collect very high resolution, fully polarimetric Ka band radar data at low depression angles of a man holding an RPG. In this paper, we examine the resulting low resolution and high resolution range profiles; and based on the observed radar cross section (RCS) value, we attempt to determine the utility of Ka band radar for detecting enemy personnel carrying RPG launchers.

  8. Near-Subsurface Science from a Digital Beamforming Polarimetric Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Carter, L. M.; Rincon, R. F.

    2015-10-01

    Many important questions in planetary science depends on our ability to detect and map surface and subsurface layers of planetary bodies. We are developing a P-band (435 MHz, 70 cm wavelength) digital beamforming radar, called Space Exploration SAR (SESAR), capable of providing the measurement flexibility needed to address multiple types of science goals. SESAR will provide high spatial resolution imaging, full polarimetry, multibeam scatterometry and altimetry of planetary targets such as the Moon and Mars by using beamforming technology that can adjust the radar experiment to meet the specific science goals of each target.

  9. Synthetic aperture wavefront sensing

    NASA Astrophysics Data System (ADS)

    Bará, Salvador; Arines, Justo; Pailos, Eliseo

    2014-06-01

    We propose the synthetic aperture wavefront sensing approach. It is based on acquiring several sets of measurements of the wavefront slopes by displacing sequentially the microlens array with respect to the unknown wavefront. These measurements are stacked together and processed as if obtained with a single-sampling array with an effective number of subpupils equal to the product of the number of microlenses by the number of displacements. We analyze and compare the performance of this approach with the method of modal coefficient averaging. The comparison is made in terms of the squared wavefront reconstruction error, spatially averaged over the pupil and statistically averaged over the noise and the aberrations of the population. We focused our attention on its applications to eye aberrometry. Our numerical results were obtained for a population statistics consistent with a wide sample of young adult eyes using different sampling grids and with several signal-to-noise ratios. They indicate that the synthetic aperture wavefront sensing is affected by less bias and noise propagation than the averaging method, providing smaller mean-squared estimation error. The number of complete Zernike radial orders that can be estimated using the synthetic aperture approach is consistently higher than that allowed by the conventional method.

  10. Off-line processing of ERS-1 synthetic aperture radar data with high precision and high throughput

    NASA Technical Reports Server (NTRS)

    Gredel, J.; Markwitz, W.; Noack, W.; Schreier, G.

    1986-01-01

    The first European remote sensing satellite ERS-1 will be launched by the European Space Agency (ESA) in 1989. The expected lifetime is two to three years. The spacecraft sensors will primarily support ocean investigations and to a limited extent also land applications. Prime sensor is the Active Microwave Instrumentation (AMI) operating in C-Band either as Synthetic Aperture Radar (SAR) or as Wave-Scatterometer and simultaneously as Wind-Scatterometer. In Europe there will be two distinct types of processing for ERS-1 SAR data, Fast Delivery Processing and Precision Processing. Fast Delivery Proceessing will be carried out at the ground stations and up to three Fast Delivery products per pass will be delivered to end users via satellite within three hours after data acquisition. Precision Processing will be carried out in delayed time and products will not be generated until several days or weeks after data acquisition. However, a wide range of products will be generated by several Processing and Archiving Facilities (PAF) in a joint effort coordinated by ESA. The German Remote Sensing Data Center (Deutsches Fernerkundungsdatenzentrum DFD) will develop and operate one of these facilities. The related activities include the acquisition, processing and evaluation of such data for scientific, public and commercial users. Based on this experience the German Remote Sensing Data Center is presently performing a Phase-B study regarding the development of a SAR processor for ERS-1. The conceptual design of this processing facility is briefly outlined.

  11. Inversion of Synthetic Aperture Radar Interferograms for Sources of Production-Related Subsidence at the Dixie Valley Geothermal Field

    SciTech Connect

    Foxall, W; Vasco, D

    2003-02-07

    We used synthetic aperture radar interferograms to image ground subsidence that occurred over the Dixie Valley geothermal field during different time intervals between 1992 and 1997. Linear elastic inversion of the subsidence that occurred between April, 1996 and March, 1997 revealed that the dominant sources of deformation during this time period were large changes in fluid volumes at shallow depths within the valley fill above the reservoir. The distributions of subsidence and subsurface volume change support a model in which reduction in pressure and volume of hot water discharging into the valley fill from localized upflow along the Stillwater range frontal fault is caused by drawdown within the upflow zone resulting from geothermal production. Our results also suggest that an additional source of fluid volume reduction in the shallow valley fill might be similar drawdown within piedmont fault zones. Shallow groundwater flow in the vicinity of the field appears to be controlled on the NW by a mapped fault and to the SW by a lineament of as yet unknown origin.

  12. Synthetic aperture radar imagery of airports and surrounding areas: Study of clutter at grazing angles and their polarimetric properties

    NASA Technical Reports Server (NTRS)

    Onstott, Robert G.; Gineris, Denise J.; Clinthorne, James T.

    1991-01-01

    The statistical description of ground clutter at an airport and in the surrounding area is addressed. These data are being utilized in a program to detect microbursts. Synthetic aperture radar data were collected at the Denver Stapleton Airport. Mountain terrain data were examined to determine if they may potentially contribute to range ambiguity problems and degrade microburst detection. Results suggest that mountain clutter may not present a special problem source. The examination of clutter at small grazing angles was continued by examining data collected at especially low altitudes. Cultural objects such as buildings produce strong sources of backscatter at angles of about 85 deg, with responses of 30 dB to 60 dB above the background. Otherwise there are a few sources which produce significant scatter. The polarization properties of hydrospheres and clutter were examined with the intent of determining the optimum polarization. This polarization was determined to be dependent upon the ratio of VV and HH polarizations of both rain and ground clutter.

  13. Coastal flood inundation monitoring with Satellite C-band and L-band Synthetic Aperture Radar data

    USGS Publications Warehouse

    Ramsey, Elijah W., III; Rangoonwala, Amina; Bannister, Terri

    2013-01-01

    Satellite Synthetic Aperture Radar (SAR) was evaluated as a method to operationally monitor the occurrence and distribution of storm- and tidal-related flooding of spatially extensive coastal marshes within the north-central Gulf of Mexico. Maps representing the occurrence of marsh surface inundation were created from available Advanced Land Observation Satellite (ALOS) Phased Array type L-Band SAR (PALSAR) (L-band) (21 scenes with HH polarizations in Wide Beam [100 m]) data and Environmental Satellite (ENVISAT) Advanced SAR (ASAR) (C-band) data (24 scenes with VV and HH polarizations in Wide Swath [150 m]) during 2006-2009 covering 500 km of the Louisiana coastal zone. Mapping was primarily based on a decrease in backscatter between reference and target scenes, and as an extension of previous studies, the flood inundation mapping performance was assessed by the degree of correspondence between inundation mapping and inland water levels. Both PALSAR- and ASAR-based mapping at times were based on suboptimal reference scenes; however, ASAR performance seemed more sensitive to reference-scene quality and other types of scene variability. Related to water depth, PALSAR and ASAR mapping accuracies tended to be lower when water depths were shallow and increased as water levels decreased below or increased above the ground surface, but this pattern was more pronounced with ASAR. Overall, PALSAR-based inundation accuracies averaged 84% (n = 160), while ASAR-based mapping accuracies averaged 62% (n = 245).

  14. Range ambiguity suppression for multiple-input, multiple-output synthetic aperture radar system using azimuth phase coding technique

    NASA Astrophysics Data System (ADS)

    Guo, Lei; Wang, Robert; Deng, Yunkai; Wang, Wei; Luo, Xiulian

    2014-01-01

    For synthetic aperture radar (SAR), range ambiguity causes a great deterioration in imaging performance. To suppress range ambiguity, the azimuth phase coding (APC) technique stands out for its effectiveness with a low implementation complexity among the available approaches. With proper phase modulation and demodulation, the position of an ambiguous signal is shifted in Doppler spectrum and then part of the ambiguity can be filtered out by an azimuth filter. However, since the suppression performance heavily depends on the system oversampling rate, the APC technique cannot achieve the same suppression performance for a multichannel SAR system compared with a single-channel SAR system. A method to suppress the range ambiguity for multiple-input, multiple-output (MIMO) SAR system based on APC technique is presented. By taking advantage of more phase centers of the MIMO SAR, a proper azimuth beamformer weight vector can be computed to null out the ambiguity position in the azimuth frequency domain and reconstruct the useful signal; thus most of the ambiguity components can be significantly suppressed. Finally, the simulation results validate the effectiveness of the proposed method.

  15. Analysis of ERS 1 synthetic aperture radar data of frozen lakes in northern Montana and implications for climate studies

    USGS Publications Warehouse

    Hall, Dorothy K.; Fagre, Daniel B.; Klasner, Fritz; Linebaugh, Gregg; Liston, Glen E.

    1994-01-01

    Lakes that freeze each winter are good indicators of regional climate change if key parameters, such as freeze-up and breakup date and maximum ice thickness, are measured over a decade-scale time frame. Synthetic aperture radar (SAR) satellite data have proven to be especially useful for measurement of climatologically significant parameters characteristic of frozen lakes. In this paper, five lakes in Glacier National Park, Montana, have been studied both in the field and using Earth Remote-Sensing Satellite (ERS) 1 SAR data during the 1992-1993 winter. The lakes are characterized by clear ice, sometimes with tubular or rounded bubbles, and often with a layer of snow ice on top of the clear ice. They are also often snow covered. Freeze-up is detected quite easily using ERS 1 SAR data as soon as a thin layer of ice forms. The effect of snow ice on the backscatter is thought to be significant but is, as yet, undetermined. On the five lakes studied, relative backscatter was found to increase with ice thickness until a maximum was reached in February. Breakup, an often ill-defined occurrence, is difficult to detect because surface water causes the SAR signal to be absorbed, thus masking the ice below. Comparison of the bubble structure of thaw lakes in northern Alaska with lakes in northern Montana has shown that the ice structure is quite different, and this difference may contribute to differential SAR signature evolution in the lakes of the two areas.

  16. Characterization of L-band synthetic aperture radar (SAR) backscatter from floating and grounded lake ice in arctic Alaska

    NASA Astrophysics Data System (ADS)

    Engram, M.; Anthony, K. W.; Meyer, F. J.; Grosse, G.

    2013-05-01

    Synthetic aperture radar (SAR) backscatter from floating lake ice is high, in contrast to low backscatter values from lake ice that is frozen completely to the lake bed (grounded ice). Knowledge of floating vs. grounded lake ice is useful for determining winter water supply, fish habitat, heat transfer to permafrost, and to observe changes in perennial lake ice status that could correlate with variations in local climate. Here, we compare calibrated L-band (23.6 cm wavelength) single- and L-band quadrature-polarized SAR return to the backscatter intensity of C-band (5.6 cm wavelength) SAR from floating and grounded lake ice over two regions in Alaska. Our primary goal was to determine if C or L-band is more useful to distinguish floating from grounded lake ice. C-band SAR showed far greater contrast between floating and grounded lake ice, making it the preferred wavelength for identifying lake ice regimes. L-band SAR backscatter was much lower from floating ice than C-band and it was different for our two study regions. Furthermore, since L-band is sensitive to ebullition bubbles trapped by lake ice (bubbles increase backscatter), this study helps to elucidate potential confounding factors of bubbles in efforts to detect floating vs. grounded ice using L-band SAR.

  17. Atmospheric corrections in interferometric synthetic aperture radar surface deformation - a case study of the city of Mendoza, Argentina

    NASA Astrophysics Data System (ADS)

    Balbarani, S.; Euillades, P. A.; Euillades, L. D.; Casu, F.; Riveros, N. C.

    2013-09-01

    Differential interferometry is a remote sensing technique that allows studying crustal deformation produced by several phenomena like earthquakes, landslides, land subsidence and volcanic eruptions. Advanced techniques, like small baseline subsets (SBAS), exploit series of images acquired by synthetic aperture radar (SAR) sensors during a given time span. Phase propagation delay in the atmosphere is the main systematic error of interferometric SAR measurements. It affects differently images acquired at different days or even at different hours of the same day. So, datasets acquired during the same time span from different sensors (or sensor configuration) often give diverging results. Here we processed two datasets acquired from June 2010 to December 2011 by COSMO-SkyMed satellites. One of them is HH-polarized, and the other one is VV-polarized and acquired on different days. As expected, time series computed from these datasets show differences. We attributed them to non-compensated atmospheric artifacts and tried to correct them by using ERA-Interim global atmospheric model (GAM) data. With this method, we were able to correct less than 50% of the scenes, considering an area where no phase unwrapping errors were detected. We conclude that GAM-based corrections are not enough for explaining differences in computed time series, at least in the processed area of interest. We remark that no direct meteorological data for the GAM-based corrections were employed. Further research is needed in order to understand under what conditions this kind of data can be used.

  18. Method for detecting surface motions and mapping small terrestrial or planetary surface deformations with synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Gabriel, Andrew K. (Inventor); Goldstein, Richard M. (Inventor); Zebker, Howard A. (Inventor)

    1990-01-01

    A technique based on synthetic aperture radar (SAR) interferometry is used to measure very small (1 cm or less) surface deformations with good resolution (10 m) over large areas (50 km). It can be used for accurate measurements of many geophysical phenomena, including swelling and buckling in fault zones, residual, vertical and lateral displacements from seismic events, and prevolcanic swelling. Two SAR images are made of a scene by two spaced antennas and a difference interferogram of the scene is made. After unwrapping phases of pixels of the difference interferogram, surface motion or deformation changes of the surface are observed. A second interferogram of the same scene is made from a different pair of images, at least one of which is made after some elapsed time. The second interferogram is then compared with the first interferogram to detect changes in line of sight position of pixels. By resolving line of sight observations into their vector components in other sets of interferograms along at least one other direction, lateral motions may be recovered in their entirety. Since in general, the SAR images are made from flight tracks that are separated, it is not possible to distinguish surface changes from the parallax caused by topography. However, a third image may be used to remove the topography and leave only the surface changes.

  19. Wave propagation in the marginal ice zone: Model predictions and comparisons with buoy and synthetic aperture radar data

    NASA Astrophysics Data System (ADS)

    Liu, Antony K.; Holt, Benjamin; Vachon, Paris W.

    1991-03-01

    In this paper the ocean wave dispersion relation and viscous attenuation by a sea ice cover are studied for waves propagating into the marginal ice zone (MIZ). The derivation of the dispersion relation and the viscous attenuation by an ice sheet are discussed for waves under flexure and pack compression. In the MIZ, the flexure effect is important for short waves. For a fixed wave period the changes in wavelength and group velocity as a function of ice thickness are significant. In turn, the exponential wave attenuation rate shows a rollover at short wave periods, whereby the rapid increase in wave attenuation rate with decreasing wave period slows down or even turns into a decrease. The Labrador Ice Margin Experiment (LIMEX), conducted on the MIZ off the east coast of Newfoundland, Canada, in March 1987, provides us with aircraft synthetic aperture radar (SAR) imagery, wave buoy, and ice property data. On the basis of the wave number spectrum from the SAR data and the concurrent wave frequency spectrum from the ocean buoy data and accelerometer data on the ice during LIMEX '87, the dispersion relation has been estimated and compared with a model. Wave energy attenuation rates are estimated from SAR data and the ice motion package data which were deployed at the ice edge and into the ice pack, and compared with the model. The model-data comparisons are reasonably good for the ice conditions observed during LIMEX '87. Some previously reported data of wave attenuation in the MIZ are revisited for model comparison.

  20. Assessing short- and long-time displacements in the Venice coastland by synthetic aperture radar interferometric point target analysis

    NASA Astrophysics Data System (ADS)

    Teatini, Pietro; Strozzi, Tazio; Tosi, Luigi; Wegmüller, Urs; Werner, Charles; Carbognin, Laura

    2007-03-01

    The Venice Lagoon in Italy is a unique environment vulnerable to loss in surface elevation relative to the mean sea level. We present detailed synthetic aperture radar (SAR) interferometric analyses on persistent point targets for the historical center of Venice, the tourist area of Sottomarina, and the Zennare farmland close to the southern lagoon edge. The selected areas are characterized by different degrees of development and our analyses show the remarkable capability of SAR Interferometric Point Target Analysis (IPTA) to map land displacement rates in densely urbanized zones and to detect movement information on isolated structures with a mm/year accuracy. A detailed analysis of the time series from 1992 to 2000 provided by IPTA shows that the vertical component of the measured displacements are the superposition of a short timescale, generally seasonal, movement on the order of 1 cm that is likely related to the fluctuation of environmental variables (temperature, piezometric head in the aquifer system underlying the lagoon, sea/lagoon water level) and a long-term ground deformation associated with building construction, the geomorphology of the area, and the human development of natural resources. If Venice is confirmed to be generally stable, significant long-term subsidence on the order of 4 mm/year is detected at the Sottomarina coastland. The highest displacement rates, of up to 8-10 mm/year, are recorded in the farmland bounding the lagoon margin where the movements are found to be highly site-specific.

  1. Delineation of inundated area and vegetation along the Amazon floodplain with the SIR-C synthetic aperture radar

    SciTech Connect

    Hess, L.L.; Melack, J.M.; Filoso, S.; Wang, Y.

    1995-07-01

    Floodplain inundation and vegetation along the Negro and Amazon rivers near Manaus, Brazil were accurately delineated using multi-frequency, polarimetric synthetic aperture radar (SAR) data from the April and October 1994 SIR-C missions. A decision-tree model was used to formulate rules for a supervised classification into five categories: water, clearing (pasture), aquatic macrophyte (floating meadow), nonflooded forest, and flooded forest. Classified images were produced and tested within three days of SIR-C data acquisition. Both C-band (5.7 cm) and L-band (24 cm) wavelengths were necessary to distinguish the cover types. HH polarization was most useful for distinguishing flooded from nonflooded vegetation (C-HH for macrophyte versus pasture, and L-HH for flooded versus nonflooded forest), and cross-polarized L-band data provided the best separation between woody and nonwoody vegetation. Between the April and October missions, the Amazon River level fell about 3.6 m and the portion of the study area covered by flooded forest decreased from 23% to 12%. This study demonstrates the ability of multifrequency SAR to quantify in near realtime the extent of inundation on forested floodplains, and its potential application for timely monitoring of flood events.

  2. Monitoring cyanobacteria-dominant algal blooms in eutrophicated Taihu Lake in China with synthetic aperture radar images

    NASA Astrophysics Data System (ADS)

    Wang, Ganlin; Li, Junsheng; Zhang, Bing; Shen, Qian; Zhang, Fangfang

    2015-01-01

    Monitoring algal blooms by optical remote sensing is limited by cloud cover. In this study, synthetic aperture radar (SAR) was deployed with the aim of monitoring cyanobacteria-dominant algal blooms in Taihu Lake in cloudy weather. The study shows that dark regions in the SAR images caused by cyanobacterial blooms damped the microwave backscatter of the lake surface and were consistent with the regions of algal blooms in quasi-synchronous optical images, confirming the applicability of SAR for detection of surface blooms. Low backscatter may also be associated with other factors such as low wind speeds, resulting in interference when monitoring algal blooms using SAR data alone. After feature extraction and selection, the dark regions were classified by the support vector machine method with an overall accuracy of 67.74%. SAR can provide a reference point for monitoring cyanobacterial blooms in the lake, particularly when weather is not suitable for optical remote sensing. Multi-polarization and multi-band SAR can be considered for use in the future to obtain more accurate information regarding algal blooms from SAR data.

  3. Analysis of SAR Image Quality Degradation due to Pointing and Stability Error of Synthetic Aperture Radar Satellite

    NASA Astrophysics Data System (ADS)

    Chun, Yong Sik; Ra, Sung Woong

    2008-12-01

    Image chain analysis of synthetic aperture radar (SAR) satellite is one of the primary activities for satellite design because SAR image quality depends on spacecraft bus performance as well as SAR payload. Especially, satellite pointing and stability error make worst effect on the original SAR image quality which is implemented by SAR payload design. In this research, Image chain analysis S/W was developed in order to analyze the SAR image quality degradation due to satellite pointing and stability error. This S/W consists of orbit model, attitude control model, SAR payload model, clutter model, and SAR processor. SAR raw data, which includes total 25 point targets in the scene of 5km × 5km swath width, was generated and then processed for analysis. High resolution mode (spotlight), of which resolution is 1m, was applied. The results of image chain analysis show that radiometric accuracy is the most degraded due to the pointing error. Therefore, the successful design of attitude control subsystem in spacecraft bus for enhancing the pointing accuracy is most important for image quality.

  4. On the retrieval of significant wave heights from spaceborne Synthetic Aperture Radar using the Max-Planck Institut algorithm.

    PubMed

    Violante-Carvalho, Nelson

    2005-12-01

    Synthetic Aperture Radar (SAR) onboard satellites is the only source of directional wave spectra with continuous and global coverage. Millions of SAR Wave Mode (SWM) imagettes have been acquired since the launch in the early 1990's of the first European Remote Sensing Satellite ERS-1 and its successors ERS-2 and ENVISAT, which has opened up many possibilities specially for wave data assimilation purposes. The main aim of data assimilation is to improve the forecasting introducing available observations into the modeling procedures in order to minimize the differences between model estimates and measurements. However there are limitations in the retrieval of the directional spectrum from SAR images due to nonlinearities in the mapping mechanism. The Max-Planck Institut (MPI) scheme, the first proposed and most widely used algorithm to retrieve directional wave spectra from SAR images, is employed to compare significant wave heights retrieved from ERS-1 SAR against buoy measurements and against the WAM wave model. It is shown that for periods shorter than 12 seconds the WAM model performs better than the MPI, despite the fact that the model is used as first guess to the MPI method, that is the retrieval is deteriorating the first guess. For periods longer than 12 seconds, the part of the spectrum that is directly measured by SAR, the performance of the MPI scheme is at least as good as the WAM model. PMID:16341447

  5. Wave-current interaction study in the Gulf of Alaska for detection of eddies by synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Liu, Antony K.; Peng, Chich Y.; Schumacher, James D.

    1994-01-01

    High resolution Esa Remote Sensing Satellite-1 (ERS-1) Synthetic Aperture Radar (SAR) images are used to detect a mesoscale eddy. Such features limit dispersal of pollock larvae and therefore likely influence recruitment of fish in the Gulf of Alaska. During high sea states and high winds, the direct surface signature of the eddy was not clearly visible, but the wave refraction in the eddy area was observed. The rays of the wave field are traced out directly from the SAR image. The ray pattern gives information on the refraction pattern and on the relative variation of the wave energy along a ray through wave current interaction. These observations are simulated by a ray-tracing model which incorporates a surface current field associated with the eddy. The numerical results of the model show that the waves are refracted and diverge in the eddy field with energy density decreasing. The model-data comparison for each ray shows the model predictions are in good agreement with the SAR data.

  6. Small-scale deformations associated with the 1992 Landers, California, earthquake mapped by synthetic aperture radar interferometry phase gradients

    NASA Astrophysics Data System (ADS)

    Price, Evelyn J.; Sandwell, David T.

    1998-11-01

    The Landers earthquake (Mw 7.3) occurred on June 28, 1992, and ruptured nearly 100 km of previously mapped and unmapped faults in the Mojave Desert. We use synthetic aperture radar interferometry (InSAR) to examine the cumulative surface deformation between April 24 and August 7, 1992, in a 100 × 100 km region surrounding the northern portion of the earthquake rupture. Also, we introduce a technique for manipulating SAR interferograms to extract short-wavelength displacement information. This technique involves computation and subsequent combination of interferometric phase gradient maps. The InSAR results show significant deformation signatures associated with faults, fractures, dry lake beds, and mountainous regions within 75-100 km of the main rupture. Using the phase gradient method, we are able to extract small-scale deformation patterns near the main rupture. Many of the preexisting, mapped faults within 50 km of the main rupture experienced triggered slip; these include the Old Woman, Lenwood, Johnson Valley, West Calico, and Calico Faults. The InSAR results also indicate right-lateral offsets along secondary fractures trending N-NE within the left-lateral zone of shear between the main rupture and the Johnson Valley Fault. Additionally, there are interesting interferogram fringe signatures surrounding Troy Dry Lake and Coyote Dry Lake that are related to deformation of dry lake beds.

  7. Design and implementation of a Synthetic Aperture Radar for Open Skies (SAROS) aboard a C-135 aircraft

    SciTech Connect

    Cooper, D.W.; Murphy, M.; Rimmel, G.

    1994-08-01

    NATO and former Warsaw Pact nations have agreed to allow overflights of their countries in the interest of easing world tension. The United States has decided to implement two C-135 aircraft with a Synthetic Aperture Radar (SAR) that has a 3-meter resolution. This work is being sponsored by the Defense Nuclear Agency (DNA) and will be operational in Fall 1995. Since the SAR equipment must be exportable to foreign nations, a 20-year-old UPD-8 analog SAR system was selected as the front-end and refurbished for this application by Loral Defense Systems. Data processing is being upgraded to a currently exportable digital design by Sandia National Laboratories. Amplitude and phase histories will be collected during these overflights and digitized on VHS cassettes. Ground stations will use reduction algorithms to process the data and convert it to magnitude-detected images for member nations. System Planning Corporation is presently developing a portable ground station for use on the demonstration flights. Aircraft integration into the C-135 aircraft is being done by the Air Force at Wright-Patterson AFB, Ohio.

  8. Analysis of two Seasat synthetic aperture radar images of an urban scene

    NASA Technical Reports Server (NTRS)

    Bryan, M. L.

    1982-01-01

    Because the Seasat satellite is not polar-orbiting, the look-directions of its SAR radar on the basic ascending and descending orbits were neither in the same direction, orthogonal to, nor opposite to, one another. This calls for a technique by means of which to identify those features within a given geographic region which were imaged from two directions by Seasat SAR and are sensitive to radar orientation. It is demonstrated that images from the two orbits with different look directions can be registered and subtracted from one another, with the resulting difference image highlighting those features that are direction-sensitive. Although this depends on a precise registration the subtraction technique is straightforward once such registration has been obtained.

  9. Surface roughness measuring system. [synthetic aperture radar measurements of ocean wave height and terrain peaks

    NASA Technical Reports Server (NTRS)

    Jain, A. (Inventor)

    1978-01-01

    Significant height information of ocean waves, or peaks of rough terrain is obtained by compressing the radar signal over different widths of the available chirp or Doppler bandwidths, and cross-correlating one of these images with each of the others. Upon plotting a fixed (e.g., zero) component of the cross-correlation values as the spacing is increased over some empirically determined range, the system is calibrated. To measure height with the system, a spacing value is selected and a cross-correlation value is determined between two intensity images at a selected frequency spacing. The measured height is the slope of the cross-correlation value used. Both electronic and optical radar signal data compressors and cross-correlations are disclosed for implementation of the system.

  10. Method for providing a polarization filter for processing synthetic aperture radar image data

    NASA Technical Reports Server (NTRS)

    Dubois, Pascale C. (Inventor); vanZyl, Jakob J. (Inventor)

    1991-01-01

    A polarization filter can maximize the signal-to-noise ratio of a polarimetric SAR and help discriminate between targets or enhance image features, e.g., enhance contract between different types of target. The method disclosed is based on the Stokes matrix/Stokes vector representation, so the targets of interest can be extended targets, and the method can also be applied to the case of bistatic polarimetric radars.

  11. The derivation of sub-canopy surface terrain models of coastal forests using synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Imhoff, M. L.; Gesch, D. B.

    1988-01-01

    Radar data acquired by the Shuttle Imaging Radar-B mission covering a portion of the Mouths of the Ganges forests were used to create a terrain model for use in determining tidal flow and eventual nutrient transport from the forest to the marine habitat. Results show that good digital topographic terrain models of wet coastal forests can be generated using multiple sets of L-band SAR and ancillary tide elevation data. The dominance of the interaction phenomenon in the radar backscatter of flooded forests can be used to create sub-canopy inundation maps which when merged with tide surface data can be used to generate reasonable topographic models. Ideally models could be improved by using multiple sets of data at a constant incidence angle over the total tide range. The optimal angle for the SAR depends upon the characteristics of the forest. The range of 46 to 57 deg seems applicable to the 12.5 m tall closed canopy in this example. Such models can be an extremely valuable tool for studying and mapping the mangal ecosystem.

  12. Mapping of sea ice and measurement of its drift using aircraft synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Leberl, F.; Bryan, M. L.; Elachi, C.; Farr, T.; Campbell, W.

    1979-01-01

    Side-looking radar images of Arctic sea ice were obtained as part of the Arctic Ice Dynamics Joint Experiment. Repetitive coverages of a test site in the Arctic were used to measure sea ice drift, employing single images and blocks of overlapping radar image strips; the images were used in conjunction with data from the aircraft inertial navigation and altimeter. Also, independently measured, accurate positions of a number of ground control points were available. Initial tests of the method were carried out with repeated coverages of a land area on the Alaska coast (Prudhoe). Absolute accuracies achieved were essentially limited by the accuracy of the inertial navigation data. Errors of drift measurements were found to be about + or - 2.5 km. Relative accuracy is higher; its limits are set by the radar image geometry and the definition of identical features in sequential images. The drift of adjacent ice features with respect to one another could be determined with errors of less than + or - 0.2 km.

  13. Maximum a posteriori classification of multifrequency, multilook, synthetic aperture radar intensity data

    NASA Technical Reports Server (NTRS)

    Rignot, E.; Chellappa, R.

    1993-01-01

    We present a maximum a posteriori (MAP) classifier for classifying multifrequency, multilook, single polarization SAR intensity data into regions or ensembles of pixels of homogeneous and similar radar backscatter characteristics. A model for the prior joint distribution of the multifrequency SAR intensity data is combined with a Markov random field for representing the interactions between region labels to obtain an expression for the posterior distribution of the region labels given the multifrequency SAR observations. The maximization of the posterior distribution yields Bayes's optimum region labeling or classification of the SAR data or its MAP estimate. The performance of the MAP classifier is evaluated by using computer-simulated multilook SAR intensity data as a function of the parameters in the classification process. Multilook SAR intensity data are shown to yield higher classification accuracies than one-look SAR complex amplitude data. The MAP classifier is extended to the case in which the radar backscatter from the remotely sensed surface varies within the SAR image because of incidence angle effects. The results obtained illustrate the practicality of the method for combining SAR intensity observations acquired at two different frequencies and for improving classification accuracy of SAR data.

  14. Upper ocean fine-scale features in synthetic aperture radar imagery. Part I: Simultaneous satellite and in-situ measurements

    NASA Astrophysics Data System (ADS)

    Soloviev, A.; Maingot, C.; Matt, S.; Fenton, J.; Lehner, S.; Brusch, S.; Perrie, W. A.; Zhang, B.

    2011-12-01

    The new generation of synthetic aperture radar (SAR) satellites provides high resolution images that open new opportunities for identifying and studying fine features in the upper ocean. The problem is, however, that SAR images of the sea surface can be affected by atmospheric phenomena (rain cells, fronts, internal waves, etc.). Implementation of in-situ techniques in conjunction with SAR is instrumental for discerning the origin of features on the image. This work is aimed at the interpretation of natural and artificial features in SAR images. These features can include fresh water lenses, sharp frontal interfaces, internal wave signatures, as well as slicks of artificial and natural origin. We have conducted field experiments in the summer of 2008 and 2010 and in the spring of 2011 to collect in-situ measurements coordinated with overpasses of the TerraSAR-X, RADARSAT-2, ALOS PALSAR, and COSMO SkyMed satellites. The in-situ sensors deployed in the Straits of Florida included a vessel-mounted sonar and CTD system to record near-surface data on stratification and frontal boundaries, a bottom-mounted Nortek AWAC system to gather information on currents and directional wave spectra, an ADCP mooring at a 240 m isobath, and a meteorological station. A nearby NOAA NEXRAD Doppler radar station provided a record of rainfall in the area. Controlled releases of menhaden fish oil were performed from our vessel before several satellite overpasses in order to evaluate the effect of surface active materials on visibility of sea surface features in SAR imagery under different wind-wave conditions. We found evidence in the satellite images of rain cells, squall lines, internal waves of atmospheric and possibly oceanic origin, oceanic frontal interfaces and submesoscale eddies, as well as anthropogenic signatures of ships and their wakes, and near-shore surface slicks. The combination of satellite imagery and coordinated in-situ measurements was helpful in interpreting fine-scale features on the sea surface observed in the SAR images and, in some cases, linking them to thermohaline features in the upper ocean. Finally, we have been able to reproduce SAR signatures of freshwater plumes and sharp frontal interfaces interacting with wind stress, as well as internal waves by combining hydrodynamic simulations with a radar imaging algorithm. The modeling results are presented in a companion paper (Matt et al., 2011).

  15. Detection Of Regolith Buried Water Stream Channels On Mars With The Help Of Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Rzhiga, O. N.

    The major problem of Mars research is search of water on its surface. Biological life is connected to water. In this connection the intense interest represents detection of water stream channels, which in the past flew on Mars. In these areas the petrified rests of the former life on Mars may be found out. Now these channels may be under regolith layer. However radio waves penetrating ability allows seeing these channels under a regolith. The radio wave falls on a regolith surface under some angle. The part of the falling wave power is reflected by regolith. Other part of it refracts under a regolith surface and reaches bottom of a channel. Here there is reflection because of a difference in refraction index of regolith and bedrock of a channel bottom. The part of reflected power gets back to the spacecraft. Passage through regolith is accompanied by electric losses. In result we receive the image of a channel which contrast depends on regolith depth, difference in refraction index of regolith and bedrock of a channel bottom as well as wavelength. In this work the optimum wavelength for detection of the water stream channels, now buried by regolith, is determined. In some assumptions concerning regolith and bedrock electric properties the model of the channel image is received. The analysis of the reflected signal level dependence from an angle under which SAR onboard aerial is directed to a planet surface is carried out. It is shown, that power of the SAR transmitter and the size of the onboard aerial will be moderate if radar survey to carry out under a small angle to a local vertical. The way, which allows suppressing the altimetric clutter arising in nadir, is specified. Here one method of search of water on Mars indications - detection of a regolith buried water stream channels is advanced only. However the radar with similar characteristics may be used as well for global survey a planet surface. Owing to a difference in character of reflection and penetrating ability of radio waves, radar survey of Mars allows receiving a lot of the new information in comparison with optical range.

  16. Advanced Land Observing Satellite (ALOS) Phased Array Type L-Band Synthetic Aperture Radar (PALSAR) mosaic for the Kahiltna terrane, Alaska, 2007-2010

    USGS Publications Warehouse

    Cole, Christopher J.; Johnson, Michaela R.; Graham, Garth E.

    2015-01-01

    The USGS has compiled a continuous, cloud-free 12.5-meter resolution radar mosaic of SAR data of approximately 212,000 square kilometers to examine the suitability of this technology for geologic mapping. This mosaic was created from Advanced Land Observing Satellite (ALOS) Phased Array type L-band Synthetic Aperture Radar (PALSAR) data collected from 2007 to 2010 spanning the Kahiltna terrane and the surrounding area. Interpretation of these data may help geologists understand past geologic processes and identify areas with potential for near-surface mineral resources for further ground-based geological and geochemical investigations.

  17. Parametric analysis of synthetic aperture radar data acquired over truck garden vegetation

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1984-01-01

    An airborne X-band SAR acquired multipolarization and multiflight pass SAR images over a truck garden vegetation area. Based on a variety of land cover and row crop direction variations, the vertical (VV) polarization data contain the highest contrast, while cross polarization contains the least. When the radar flight path is parallel to the row direction, both horizontal (HH) and VV polarization data contain very high return which masks out the specific land cover that forms the row structure. Cross polarization data are not that sensitive to row orientation. The inclusion of like and cross polarization data help delineate special surface features (e.g., row crop against non-row-oriented land cover, very-rough-surface against highly row-oriented surface).

  18. High-resolution rainfall signatures on X-band Synthetic Aperture Radar imagery: model analysis and experimental validation

    NASA Astrophysics Data System (ADS)

    Marzano, F. S.; Mori, S.; Mugnai, A.; Weinman, J. A.

    2009-04-01

    Climate modelers need global precipitation measurements because the released latent heat distribution has a profound effect on the performance of such models. Precipitation measurements are also required to facilitate water management strategies by hydrologists, and managers of transportation, agricultural and flood relief agencies. Although precipitation measurements are widely available in technologically advanced countries, the measurement of precipitation over oceans, mountainous terrain and less developed regions leaves much to be desired. Since the 1980s much of our understanding of global precipitation has been provided by space-borne passive microwave radiometers and a combination of microwave and infrared passive measurements. Unfortunately space-borne microwave radiometers, even in combination with infrared sensors, have had limited success in retrieving precipitation over land because they rely heavily on the scattering properties of ice in the upper regions of precipitating clouds. Those scattering properties may be poorly related to surface rainfall rates. This limitation can be overcome over land by space-based radars operating at X or Ku band. The Ku band Precipitation Radar (PR) aboard the Tropical Rainfall Measurement Mission (TRMM) program has provided unique precipitation measurements over land. Mountainous terrain has presented challenges to both ground and space-based radars. Radar reflectivity measurements from PR are routinely removed within about 1 to 2 kilometers from mountainous surfaces to avoid ground clutter. If significant shallow precipitation or rain cells smaller than the 4 km horizontal resolution occur along mountain slopes, then such precipitation may be missed by PR. The measurement of light, small rain cells may also be impaired by the signal-to-noise ratio floor of the PR. A new opportunity to measure precipitation from space may be afforded by the forthcoming availability of several X-band Synthetic Aperture Radars (X-SARs). The TerraSAR-X (TSX) was launched on June 15, 2007 by the Deutsches Zentrum f. Luft u. Raumfahrt (DLR) and another X-SAR will be launched by 2009. The Constellation of Small Satellites for Mediterranean basin Observations (COSMO-SkyMed, CSK) will be launched by the Agenzia Spaziale Italiana (ASI) within 2009. The first of four of these satellites was launched by ASI on June 7, 2007. The Israeli Defense Ministry plans to launch yet another X-band SAR, the TecSAR SAR Technology Demonstration Satellite, later in 2009. Space-borne X-SARs are generally not designed for atmospheric observation. SARs are often considered "all weather" sensors. However, there is relevant theoretical and experimental evidence that X-band radar may be significantly affected by precipitation occurrence within the synthetically scanned area [9]-[13]. As a matter of fact, PR was designed at Ku band which is only 4 GHz away from X band. Several authors showed that X-SARs are more sensitive to rainfall effects than SARs operating at longer wavelengths, such as L and C bands [10]-[13]. For example, this was demonstrated by the Shuttle Missions STS-59 and 68 of 1994 and the STS-99 Shuttle Radar Topography Mission (SRTM) of 2000 carrying the first X-SAR along with L and C band SARs. Rainfall reflectivity at X-band may be enhanced by about 12 dB and the attenuation increased by about 4 dB when compared to C-band reflectivity and attenuation. The potential of X-SAR for precipitation retrieval is intriguing. They will probably be able to measure rainfall over land with greater sensitivity than from radiometers. The high spatial resolution (less than 100 m) of X-SARs can provide new insights into the structure of precipitating clouds with respect to PR and its future upgrades. X-SAR platforms could also significantly enhance the planned constellation of satellites carrying microwave radiometers and radars that will be part of the foreseen Global Precipitation Measurements (GPM) mission. These X-SAR satellites, then, may make a valuable contribution to our understanding of the hydrological cycle. This work is devoted to the exploration of the potential of space-borne microwave SAR to estimate rainfall over land from both a model and inversion point of view. The main objective is to provide a framework for a physically-based inversion of SARs measurements at X band over land. The X-SARs potentials for rainfall retrievals will be investigated to design quantitative inversion algorithms. We will concentrate on SAR inversion over land in order to avoid the ambiguities of X-SAR response over ocean in the presence of rainfall. A forward model of SAR response will be illustrated not only the X band, but also at Ku and Ka band where some SAR technology is already available. The inversion methodologies will be extensively illustrated and quantitative applications to X-SAR data will be discussed, dealing with several case studies gathered during overpasses of TerraSAR-X over America and Europe. The latter will be also discussed in terms of rain-field validation using available ground-based weather radar data.

  19. Seasat synthetic aperture radar /SAR/ response to lowland vegetation types in eastern Maryland and Virginia

    NASA Technical Reports Server (NTRS)

    Krohn, M. D.; Milton, N. M.; Segal, D. B.

    1983-01-01

    Examination of Seasat SAR images of eastern Maryland and Virginia reveals botanical distinctions between vegetated lowland areas and adjacent upland areas. Radar returns from the lowland areas can be either brighter or darker than returns from the upland forests. Scattering models and scatterometer measurements predict an increase of 6 dB in backscatter from vegetation over standing water. This agrees with the 30-digital number (DN) increase observed in the digital Seasat data. The brightest areas in the Chickahominy, Virginia, drainage, containing P. virginica about 0.4 m high, contrast with the brightest areas in the Blackwater, Maryland, marshes, which contain mature loblolly pine in standing water. The darkest vegetated area in the Chickahominy drainage contains a forest of Nyssa aquatica (water tupelo) about 18 m high, while the darkest vegetated area in the Blackwater marshes contains the marsh plant Spartina alterniflora, 0.3 m high. The density, morphology, and relative geometry of the lowland vegetation with respect to standing water can all affect the strength of the return L band signal.

  20. Detection of regolith buried water stream channels on Mars with the help of synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    Rzhiga, O. N.

    The major problem of Mars research is search of water on its surface Biological life is connected to water In this connection the intense interest represents detection of water stream channels which in the past flew on Mars In these areas the petrified rests of the former life on Mars may be found out Now these channels may be under regolith layer However radio waves penetrating ability allows seeing these channels under a regolith The radio wave falls on a regolith surface under some angle The part of the falling wave power is reflected by regolith Other part of it refracts under a regolith surface and reaches bottom of a channel Here there is reflection because of a difference in refraction index of regolith and bedrock of a channel bottom The part of reflected power gets back to the spacecraft Passage through regolith is accompanied by electric losses In result we receive the image of a channel which contrast depends on regolith depth difference in refraction index of regolith and bedrock of a channel bottom as well as wavelength In this work in some assumptions concerning regolith and bedrock electric properties the model of the channel image is received The optimum wavelength for detection of the water stream channels now buried by regolith is determined The analysis of the reflected signal level dependence from an angle under which SAR onboard aerial is directed to a planet surface is carried out It is shown that power of the SAR transmitter and the size of the onboard aerial will be moderate if radar survey to carry out

  1. Resurrection Of Archived Synthetic Aperture Radar Imagery For Characterizing Hydrodynamics On Boreal Landscapes

    NASA Astrophysics Data System (ADS)

    Sass, G. Z.; Creed, I. F.

    2006-12-01

    Characterizing the spatial and temporal variation in surface hydrological patterns of large boreal landscapes is vital since these patterns define the occurrence of key areas of land- to-lake and land-to-atmosphere hydrological and biogeochemical linkages that are critical in the movement of matter and energy at local to global scales. However, monitoring surface hydrological dynamics over large geographic extents and over long periods of time is a challenge for hydrologists as traditional point measurements are not practical. In this study we used ERS radar imagery to monitor the variation in surface hydrological patterns over a 12 year period and to assess the change in the organization of saturated and inundated areas of the landscape that may form hotspots or hot moments for various biogeochemical and ecological processes. Using the regional Utikuma River drainage basin (1000 km2) as the test area, analyses of patterns of wetlands (including both saturated and inundated areas) indicated that during dry climatic conditions, wetland sizes were small and disconnected from each other and receiving bodies of water. As climatic conditions changed from dry to mesic, wetland numbers increased but were still disconnected from the rest of the landscape. It required very wet climatic conditions before the disjointed wetlands coalesced and connected to lakes. During these wet conditions the response of the lake level at Utikuma Lake was observed to be much higher than under drier conditions. Analyses of individual wetland maps and integrated probability maps have the potential to inform future biogeochemical and ecological investigations and forest management on the Boreal Plain.

  2. Strain Partitioning and Localization within Dobe Graben Using Differential Interferometric Synthetic Aperture Radar (D-INSAR) and Shuttle Radar Terrain Model

    NASA Astrophysics Data System (ADS)

    Demissie, Z. S.; Abdelsalam, M. G.; Byrnes, J. M.; Bridges, D.

    2014-12-01

    The Dobe graben is a northwestern trending, Quaternary continental rift found within the east-central block of the Afar Depression (AD), Ethiopia. The AD is one of only few places where three active tectonic rift arms meet on land. Extensional rifting is ongoing in the Dobe graben as evident by the 1989 swarm of intermediate magnitude (5.7 < Ms < 6.3) earthquakes. Dobe graben extension occurs on steeply dipping faults, where the maximum displacement, fault length, heave and spacing spans in three orders of magnitude. Crustal deformation within the graben was measured through ascending and descending interferograms using the Advanced Synthetic Aperture Radar (ASAR), C- Band (l = 5.6 cm) of the ENVISAT satellite. Results from the Differential Interferometric Synthetic Aperture Radar (D-INSAR) over a period of four years (05/20/2005 to 03/05/2010) suggests that the vertical component of deformation is distributed along a 50 km long NW trending zone in the Dobe graben. The vertical component of deformation is -0.5 to -0.3 cm along the graben axial rift floor likely representing subsidence due to riftingand +0.6 cm to 0.9 cm at the middle of the Dobe relay zone due to uplifting along the border escarpment faults. An estimate for the extension rate has been calculated from twelve traverses across the Dobe graben using Shuttle Rader Terrain Model (SRTM). Results show a deformation elongation (e) value ranging from 0.225 to 0.348. A fractal dimension of 0.03 from the graben floor was obtained for the measured population of fault throws (n= 162) in 12 traverses totaling 172 km. This value is interpreted to represent the dominant contribution to extension from faults with large throw. Moreover, frequency distribution of a natural fault population along the graben floor revealed a negative exponential law distribution indicating a strong strain partitioning within the active axial graben floor. A fractal dimension of 0.01 from the graben shoulder escarpment was obtained for the measured population of fault throws (n= 30) in 12 traverses totaling 48 km revealed a negative power fit distribution indicated a strong strain localization by the graben boarder faults.

  3. Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation

    USGS Publications Warehouse

    Lu, Zhiming; Masterlark, Timothy; Dzurisin, D.

    2005-01-01

    Okmok volcano, located in the central Aleutian arc, Alaska, is a dominantly basaltic complex topped with a 10-km-wide caldera that formed circa 2.05 ka. Okmok erupted several times during the 20th century, most recently in 1997; eruptions in 1945, 1958, and 1997 produced lava flows within the caldera. We used 80 interferometric synthetic aperture radar (InSAR) images (interferograms) to study transient deformation of the volcano before, during, and after the 1997 eruption. Point source models suggest that a magma reservoir at a depth of 3.2 km below sea level, located beneath the center of the caldera and about 5 km northeast of the 1997 vent, is responsible for observed volcano-wide deformation. The preeruption uplift rate decreased from about 10 cm yr-1 during 1992-1993 to 2 ??? 3 cm yr-1 during 1993-1995 and then to about -1 ??? -2 cm yr-1 during 1995-1996. The posteruption inflation rate generally decreased with time during 1997-2001, but increased significantly during 2001-2003. By the summer of 2003, 30 ??? 60% of the magma volume lost from the reservoir in the 1997 eruption had been replenished. Interferograms for periods before the 1997 eruption indicate consistent subsidence of the surface of the 1958 lava flows, most likely due to thermal contraction. Interferograms for periods after the eruption suggest at least four distinct deformation processes: (1) volcano-wide inflation due to replenishment of the shallow magma reservoir, (2) subsidence of the 1997 lava flows, most likely due to thermal contraction, (3) deformation of the 1958 lava flows due to loading by the 1997 flows, and (4) continuing subsidence of 1958 lava flows buried beneath 1997 flows. Our results provide insights into the postemplacement behavior of lava flows and have cautionary implications for the interpretation of inflation patterns at active volcanoes.

  4. Climate Change Indicator for Hazard Identification of Indian North West Coast Marine Environment Using Synthetic Aperture Radar (sar)

    NASA Astrophysics Data System (ADS)

    Gambheer, Phani Raj

    2012-07-01

    Stormwater runoff, Petroleum Hydrocarbon plumes are found abundantly near coastal cities, coastal population settlements especially in developing nations as more than half the world's human population. Ever increasing coastal populations and development in coastal areas have led to increased loading of toxic substances, nutrients and pathogens. These hazards cause deleterious effects on the population in many ways directly or indirectly which lead to algal blooms, hypoxia, beach closures, and damage to coastal fisheries. Hence these pollution hazards are important and the coastal administrations and people need to be aware of such a danger lurking very close to them. These hazards due to their small size, dynamic and episodic in nature are difficult to be visualized or to sample using in-situ traditional scientific methods. Natural obstructions like cloud cover and complex coastal circulations can hinder to detect and monitor such occurrences in the selected areas chosen for observations. This study takes recourse to Synthetic Aperture Radar (SAR) imagery because the pollution hazards are easily detectable as surfactants are deposited on the sea surface, along with nutrients and pathogens, smoothing capillary and small gravity waves to produce areas of reduced backscatter compared with surrounding ocean. These black spots can be termed as `Ecologic Indicator' and formed probably due to stronger thermal stratification, a deepening event of thermocline. SAR imagery that delivers useful data better than others regardless of darkness or cloud cover, should be made as an important observational tool for assessment and monitoring marine pollution hazards in the areas close to coastal regions. Till now the effects of climate change, sea level rise and global warming seems to have not affected the coastal populace of India in intrusions of sea water but it takes significance to the human health as the tides dominate these latitudes with bringing these polluted waters. KEY WORDS Coastal, ecologic, estuarine, hazard, indicator, marine, pollution, stressor, tides

  5. Coastal Monitoring Using L-band Synthetic Aperture Radar (SAR) Image Data - Some Case Studies in Asian Delta Areas

    NASA Astrophysics Data System (ADS)

    Tanaka, A.

    2014-12-01

    Coastal geomorphology is highly variable as it is affected by sea-level changes and other naturally- and human-induced fluctuations. To effectively assess and monitor geomorphological changes in various time scales is thus critical for coastal management. Asian mega deltas are vulnerable to a sea-level rise due to its low-lying delta plain, and are dynamic region given a large amount of sediment supply. However, limited data availability and accessibility in the deltas have prevented establishment of systematic coastal monitoring. A variety of remote sensing systems can be used to monitor geomorphological changes in coastal areas as it has wide spatial coverage and high temporal repeatability. Especially, analysis using SAR (Synthetic Aperture Radar) data not affected by the cloud conditions offer potential for monitoring in the monsoon Asia region. We will present some case studies of Asian coastal regions using L-band SAR data, ALOS (Advanced Land Observing Satellite) PALSAR (Phased Array type L-band SAR) and JERS-1 (Japanese Earth Resource Satellite-1) SAR data. One example is that time-series of radar amplitude images can be used to delineate changes quantitatively of the areal extent of river-mouth bars in distributaries of the Mekong River delta. It shows that the estimated areas of river mouthbars gradually increase on an annual time scale, and seasonal variations of areas were also recognized. Another example is that differential SAR interferometry is applied to the coast of the Yellow River delta in China. It shows very high subsidence rates, likely due to groundwater pumping. A further example is that we apply a SAR interferometry time series analysis to monitor ground deformations in the lower Chao Phraya delta plain, Thailand. A single reference time series interferogram from the stacking of unwrapped phases were applied. The subsidence and uplift pattern observed using the SAR interferometry time series analysis highlights the spatial complexity. Longer-term continuous monitoring with future SAR missions, such as ALOS-2, will provide us with more opportunities for new insights into coastal monitoring.

  6. Analysis of polarimetric synthetic aperture radar and passive visible light polarimetric imaging data fusion for remote sensing applications

    NASA Astrophysics Data System (ADS)

    Maitra, Sanjit

    The recent launch of spaceborne (TerraSAR-X, RADARSAT-2, ALOS-PALSAR, RISAT) and airborne (SIRC, AIRSAR, UAVSAR, PISAR) polarimetric radar sensors, with capability of imaging through day and night in almost all weather conditions, has made polarimetric synthetic aperture radar (PolSAR) image interpretation and analysis an active area of research. PolSAR image classification is sensitive to object orientation and scattering properties. In recent years, significant work has been done in many areas including agriculture, forestry, oceanography, geology, terrain analysis. Visible light passive polarimetric imaging has also emerged as a powerful tool in remote sensing for enhanced information extraction. The intensity image provides information on materials in the scene while polarization measurements capture surface features, roughness, and shading, often uncorrelated with the intensity image. Advantages of visible light polarimetric imaging include high dynamic range of polarimetric signatures and being comparatively straightforward to build and calibrate. This research is about characterization and analysis of the basic scattering mechanisms for information fusion between PolSAR and passive visible light polarimetric imaging. Relationships between these two modes of imaging are established using laboratory measurements and image simulations using the Digital Image and Remote Sensing Image Generation (DIRSIG) tool. A novel low cost laboratory based S-band (2.4GHz) PolSAR instrument is developed that is capable of capturing 4 channel fully polarimetric SAR image data. Simple radar targets are formed and system calibration is performed in terms of radar cross-section. Experimental measurements are done using combination of the PolSAR instrument with visible light polarimetric imager for scenes capturing basic scattering mechanisms for phenomenology studies. The three major scattering mechanisms studied in this research include single, double and multiple bounce. Single bounce occurs from flat surfaces like lakes, rivers, bare soil, and oceans. Double bounce can be observed from two adjacent surfaces where one horizontal flat surface is near a vertical surface such as buildings and other vertical structures. Randomly oriented scatters in homogeneous media produce a multiple bounce scattering effect which occurs in forest canopies and vegetated areas. Relationships between Pauli color components from PolSAR and Degree of Linear Polarization (DOLP) from passive visible light polarimetric imaging are established using real measurements. Results show higher values of the red channel in Pauli color image (|HH-VV|) correspond to high DOLP from double bounce effect. A novel information fusion technique is applied to combine information from the two modes. In this research, it is demonstrated that the Degree of Linear Polarization (DOLP) from passive visible light polarimetric imaging can be used for separation of the classes in terms of scattering mechanisms from the PolSAR data. The separation of these three classes in terms of the scattering mechanisms has its application in the area of land cover classification and anomaly detection. The fusion of information from these particular two modes of imaging, i.e. PolSAR and passive visible light polarimetric imaging, is a largely unexplored area in remote sensing and the main challenge in this research is to identify areas and scenarios where information fusion between the two modes is advantageous for separation of the classes in terms of scattering mechanisms relative to separation achieved with only PolSAR.

  7. Monitoring of Ground Movement and Generation of Digital Elevation Models Using Interferometric Synthetic Aperture Radar (InSAR) Data

    NASA Astrophysics Data System (ADS)

    Panda, B. B.

    2013-12-01

    Interferometric synthetic aperture radar (InSAR) has the potential for measuring deformation of the earth's surface with very high accuracy and for the development of digital elevation models. Both capabilities are of high relevance for ground movement assessment. In addition, when archived raw data is available (post 1992), recent historic movement may be quantifiable. InSAR utilizes satellite-based data acquired at two different times along orbits of a similar trajectory to detect changes in the ground surface elevation. This technique can be used to monitor ground movement for rectangular areas as large as 100 kilometers on a side. Knowledge of topography, geology, trends and mechanics of existing ground movement is required for successful interpretation of InSAR data. The detection of ground surface deformation in terrain of high slope relief terrain is difficult. For ground deformation mapping by means of InSAR it is necessary to separate the motion-related and the topographic phase contributions. This is achieved by using a low resolution digital elevation model (DEM) during the processing of InSAR data. The application of InSAR technology to mining areas provides monitoring of not only the active mine areas but also the adjacent regions that has been affected by mining. Thus InSAR technique proves to be an essential ground monitoring methods in future for mining areas. The results from the InSAR analysis are compared with data from a ground-based monitoring system comprised of measured survey prisms for an open pit mine in Canada. InSAR analysis provided the location of the stable site for relocating the crusher which was affected by movement of pit slope. The presentation will show the application of InSAR technology to various mines in USA and Canada. Besides subsidence evaluation, InSAR data is also used to generate digital elevation models (DEM) and digital terrain models (DTM). The DEM and DTM derived from InSAR data for a mine in Canada is compared with the survey and LIDAR data to demonstrate the applicability of InSAR data to model surface topography.

  8. Gulf of Mexico Ecological Forecasting - Atlantic Bluefin Tuna Population Assessment and Management using Synthetic Aperture Radar (SAR) Data

    NASA Astrophysics Data System (ADS)

    Laygo, K.; Jones, I.; Huerta, J.; Holt, B.

    2010-12-01

    Atlantic Bluefin Tuna (Thunnus thynnus) is one of the largest vertebrates in the world and is in high demand in sushi markets. It is a highly political species and is managed internationally by the International Commission for the Conservation of Atlantic Tuna. The Gulf of Mexico and the Mediterranean Sea are the only two known spawning sites in the world. However, there is a large variance in estimates of adult Atlantic Tuna spawning. This research focuses on extending Earth science research results to existing decision-making systems, National Oceanic and Atmospheric Administration (NOAA) and the National Marine Fisheries Service (NMFS)for population assessment and management of Atlantic Bluefin Tuna. The research team is a multi-sector and multi-disciplinary team composed of government (NOAA_NMFS), academic (University of South Florida Institute for Marine Remote Sensing) and commercial (Roffer’s Ocean Fishing Forecasting Service, Inc.) institutions. Their goal is to reduce the variance in the estimates of adult Bluefin Tuna spawning stock abundance in the Gulf of Mexico (GOM). Therefore, this paper will be derived from the innovative use of several earth orbiting satellites focusing on the use of synthetic aperture radar (SAR) data to identify Sargassum, which is a floating marine algae that may be relevant to the presence of Bluefin Tuna aggregations. The SAR imagery will be examined in combination with MODIS and MERIS Chlorophyll-a products to detect fine-scale surface current shear, eddy and frontal features, as well as biological slicks due to the presence of Sargassum. In addition, wind records from NOAA buoy data will be studied to analyze wind patterns in the Gulf of Mexico. The fine-resolution, all-weather capabilities of SAR provide a valuable complement to optical/IR sensors, which are often impacted by cloud cover. This study will provide an assessment of whether or not SAR can contribute to decision support efforts relevant to commercial fisheries through the improvement of the understanding of environmental conditions relative to Tuna. The critically endangered Atlantic Bluefin Tuna (Thunnus thynnus)

  9. Remote sensing of a dynamic sub-arctic peatland reservoir using optical and synthetic aperture radar data

    NASA Astrophysics Data System (ADS)

    Larter, Jarod Lee

    Stephens Lake, Manitoba is an example of a peatland reservoir that has undergone physical changes related to mineral erosion and peatland disintegration processes since its initial impoundment. In this thesis I focused on the processes of peatland upheaval, transport, and disintegration as the primary drivers of dynamic change within the reservoir. The changes related to these processes are most frequent after initial reservoir impoundment and decline over time. They continue to occur over 35 years after initial flooding. I developed a remote sensing approach that employs both optical and microwave sensors for discriminating land (Le. floating peatlands, forested land, and barren land) from open water within the reservoir. High spatial resolution visible and near-infrared (VNIR) optical data obtained from the QuickBird satellite, and synthetic aperture radar (SAR) microwave data obtained from the RADARSAT-1 satellite were implemented. The approach was facilitated with a Geographic Information System (GIS) based validation map for the extraction of optical and SAR pixel data. Each sensor's extracted data set was first analyzed separately using univariate and multivariate statistical methods to determine the discriminant ability of each sensor. The initial analyses were followed by an integrated sensor approach; the development of an image classification model; and a change detection analysis. Results showed excellent (> 95%) classification accuracy using QuickBird satellite image data. Discrimination and classification of studied land cover classes using SAR image texture data resulted in lower overall classification accuracies (˜ 60%). SAR data classification accuracy improved to > 90% when classifying only land and water, demonstrating SAR's utility as a land and water mapping tool. An integrated sensor data approach showed no considerable improvement over the use of optical satellite image data alone. An image classification model was developed that could be used to map both detailed land cover classes and the land and water interface within the reservoir. Change detection analysis over a seven year period indicated that physical changes related to mineral erosion, peatland upheaval, transport, and disintegration, and operational water level variation continue to take place in the reservoir some 35 years after initial flooding. This thesis demonstrates the ability of optical and SAR satellite image remote sensing data sets to be used in an operational context for the routine discrimination of the land and water boundaries within a dynamic peatland reservoir. Future monitoring programs would benefit most from a complementary image acquisition program in which SAR images, known for their acquisition reliability under cloud cover, are acquired along with optical images given their ability to discriminate land cover classes in greater detail.

  10. Monitoring Land Subsidence in Arizona Due to Excessive Groundwater Withdrawal Using Interferometric Synthetic Aperture Radar (InSAR) Data

    NASA Astrophysics Data System (ADS)

    Conway, B. D.

    2014-12-01

    Land subsidence due to excess groundwater overdraft has been an ongoing problem in south-central and southern Arizona since the1940's. The first earth fissure attributed to excessive groundwater withdrawal was discovered in 1946 near Picacho, Arizona. In some areas of the State, groundwater declines of more than 400 feet have resulted in extensive earth fissuring and widespread land subsidence; land subsidence of more than 19 feet has been documented near Phoenix and Eloy. The Arizona Department of Water Resources (ADWR) has been monitoring land subsidence throughout Arizona since 1997 using Interferometric Synthetic Aperture Radar (InSAR) Data and Global Navigation Satellite System Data. The ADWR InSAR program has proven to be a critical resource in monitoring land subsidence throughout Arizona, resulting in the identification of more than twenty-five individual land subsidence features that cover an area of more than 1,200 square miles. The majority of these land subsidence features are a direct result of groundwater declines attributed to groundwater overdraft. Using InSAR data in conjunction with both automated and manual groundwater level datasets, ADWR is able to monitor active land subsidence areas as well as identify other areas that may require additional InSAR monitoring. InSAR data have also proven to be extremely useful in monitoring land surface uplift associated with rising groundwater levels near groundwater recharge facilities. InSAR data can show the impact of the recharged groundwater as the area of uplift extends down gradient from the recharge facility. Some highlights of recent InSAR results include the identification of a new land subsidence feature in the eastern portion of Metropolitan Phoenix where groundwater levels have recently declined; the identification of changes to a floodplain that may be exacerbating recent flooding; seasonal land subsidence and uplift related to seasonal groundwater demands; and the identification of uplift related to groundwater recharge facilities. The declining groundwater levels in Arizona are both a challenge for future groundwater availability but also for mitigating land subsidence. ADWR's InSAR program will continue to be a critical tool for monitoring land subsidence due to excessive groundwater withdrawal.

  11. Savannah woody structure modelling and mapping using multi-frequency (X-, C- and L-band) Synthetic Aperture Radar data

    NASA Astrophysics Data System (ADS)

    Naidoo, Laven; Mathieu, Renaud; Main, Russell; Kleynhans, Waldo; Wessels, Konrad; Asner, Gregory; Leblon, Brigitte

    2015-07-01

    Structural parameters of the woody component in African savannahs provide estimates of carbon stocks that are vital to the understanding of fuelwood reserves, which is the primary source of energy for 90% of households in South Africa (80% in Sub-Saharan Africa) and are at risk of over utilisation. The woody component can be characterised by various quantifiable woody structural parameters, such as tree cover, tree height, above ground biomass (AGB) or canopy volume, each been useful for different purposes. In contrast to the limited spatial coverage of ground-based approaches, remote sensing has the ability to sense the high spatio-temporal variability of e.g. woody canopy height, cover and biomass, as well as species diversity and phenological status - a defining but challenging set of characteristics typical of African savannahs. Active remote sensing systems (e.g. Light Detection and Ranging - LiDAR; Synthetic Aperture Radar - SAR), on the other hand, may be more effective in quantifying the savannah woody component because of their ability to sense within-canopy properties of the vegetation and its insensitivity to atmosphere and clouds and shadows. Additionally, the various components of a particular target's structure can be sensed differently with SAR depending on the frequency or wavelength of the sensor being utilised. This study sought to test and compare the accuracy of modelling, in a Random Forest machine learning environment, woody above ground biomass (AGB), canopy cover (CC) and total canopy volume (TCV) in South African savannahs using a combination of X-band (TerraSAR-X), C-band (RADARSAT-2) and L-band (ALOS PALSAR) radar datasets. Training and validation data were derived from airborne LiDAR data to evaluate the SAR modelling accuracies. It was concluded that the L-band SAR frequency was more effective in the modelling of the CC (coefficient of determination or R2 of 0.77), TCV (R2 of 0.79) and AGB (R2 of 0.78) metrics in Southern African savannahs than the shorter wavelengths (X- and C-band) both as individual and combined (X + C-band) datasets. The addition of the shortest wavelengths also did not assist in the overall reduction of prediction error across different vegetation conditions (e.g. dense forested conditions, the dense shrubby layer and sparsely vegetated conditions). Although the integration of all three frequencies (X + C + L-band) yielded the best overall results for all three metrics (R2 = 0.83 for CC and AGB and R2 = 0.85 for TCV), the improvements were noticeable but marginal in comparison to the L-band alone. The results, thus, do not warrant the acquisition of all three SAR frequency datasets for tree structure monitoring in this environment.

  12. Interferometric synthetic aperture microscopy

    PubMed Central

    Ralston, Tyler S.; Marks, Daniel L.; Carney, P. Scott; Boppart, Stephen A.

    2014-01-01

    State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the light–sample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe and demonstrate a novel computational image-formation technique called interferometric synthetic aperture microscopy (ISAM). ISAM has the potential to broadly impact real-time three-dimensional microscopy and analysis in the fields of cell and tumour biology, as well as in clinical diagnosis where in vivo imaging is preferable to biopsy. PMID:25635181

  13. Comparing range data across the slow-time dimension to correct motion measurement errors beyond the range resolution of a synthetic aperture radar

    SciTech Connect

    Doerry, Armin W.; Heard, Freddie E.; Cordaro, J. Thomas

    2010-08-17

    Motion measurement errors that extend beyond the range resolution of a synthetic aperture radar (SAR) can be corrected by effectively decreasing the range resolution of the SAR in order to permit measurement of the error. Range profiles can be compared across the slow-time dimension of the input data in order to estimate the error. Once the error has been determined, appropriate frequency and phase correction can be applied to the uncompressed input data, after which range and azimuth compression can be performed to produce a desired SAR image.

  14. Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)

    SciTech Connect

    Fellerhoff, J.R.; Kohler, S.M.

    1991-01-01

    An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

  15. Aperture undersampling using compressive sensing for synthetic aperture stripmap imaging

    NASA Astrophysics Data System (ADS)

    Leier, Stefan; Zoubir, Abdelhak M.

    2014-12-01

    Synthetic aperture imaging is a high-resolution imaging technique employed in radar and sonar applications, which construct a large aperture by constantly transmitting pulses while moving along a scene of interest. In order to avoid azimuth image ambiguities, spatial sampling requirements have to be fulfilled along the aperture trajectory. The latter, however, limits the maximum speed and, therefore, the coverage rate of the imaging system. This paper addresses the emerging field of compressive sensing for stripmap synthetic aperture imaging using transceiver as well as single-transmitter and multi-receiver systems so as to overcome the spatial Nyquist criterion. As a consequence, future imaging systems will be able to significantly reduce their mission time due to an increase in coverage rate. We demonstrate the capability of our proposed compressive sensing approach to at least double the maximum sensor speed based on synthetic data and real data examples. Simultaneously, azimuth image ambiguities are successfully suppressed. The real acoustical measurements are obtained by a small-scale ultrasonic synthetic aperture laboratory system.

  16. Order N^2 log(N) backprojector algorithm for focusing wide-angle wide-bandwidth arbitrary-motion synthetic aperture radar

    NASA Astrophysics Data System (ADS)

    McCorkle, John W.; Rofheart, Martin

    1996-06-01

    A new, fast algorithm for synthetic aperture radar (SAR) image formation is introduced. The algorithm is based on a decomposition of the time domain backprojection technique. It inherits the primary advantages of time domain backprojection: simple motion compensation, simple and spatially unconstrained propagation velocity compensation, and localized processing artifacts. The computational savings are achieved by using a divide-and-conquer strategy of decomposition, and exploiting spatial redundancy in the resulting sub-problems. The decomposition results in a quadtree data structure that is readily parallelizable and requires only limited interprocessor communications. For a SAR with N aperture points and an N by N image area, the algorithm is seen to achieve O(N2logN) complexity. The algorithm allows a direct trade between processing speed and focused image quality.

  17. Estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar: The 1997 eruption of Okmok Volcano, Alaska

    USGS Publications Warehouse

    Lu, Zhiming; Fielding, E.; Patrick, M.R.; Trautwein, C.M.

    2003-01-01

    Interferometric synthetic aperture radar (InSAR) techniques are used to calculate the volume of extrusion at Okmok volcano, Alaska by constructing precise digital elevation models (DEMs) that represent volcano topography before and after the 1997 eruption. The posteruption DEM is generated using airborne topographic synthetic aperture radar (TOPSAR) data where a three-dimensional affine transformation is used to account for the misalignments between different DEM patches. The preeruption DEM is produced using repeat-pass European Remote Sensing satellite data; multiple interferograms are combined to reduce errors due to atmospheric variations, and deformation rates are estimated independently and removed from the interferograms used for DEM generation. The extrusive flow volume associated with the 1997 eruption of Okmok volcano is 0.154 ?? 0.025 km3. The thickest portion is approximately 50 m, although field measurements of the flow margin's height do not exceed 20 m. The in situ measurements at lava edges are not representative of the total thickness, and precise DEM data are absolutely essential to calculate eruption volume based on lava thickness estimations. This study is an example that demonstrates how InSAR will play a significant role in studying volcanoes in remote areas.

  18. Coherence-based land cover classification in forested areas of Chattisgarh, Central India, using environmental satellite--advanced synthetic aperture radar data

    NASA Astrophysics Data System (ADS)

    Nizalapur, Vyjayanthi; Madugundu, Rangaswamy; Jha, Chandra Shekhar

    2011-01-01

    In the present work, the potential of synthetic aperture radar (SAR) interferometric coherence in land cover classification is studied over forested areas of Bilaspur, Chattisgarh, India using Environmental Satellite--Advanced Synthetic Aperture Radar (ENVISAT-ASAR) C-band data. Single look complex (SLC) interferometric pair ASAR data of 24th September 2006 (SLC-1) and 29th October 2006 (SLC-2) covering the study area were acquired and processed to generate backscatter and interferometric coherence images. A false colored composite of coherence, backscatter difference, and mean backscatter was generated and subjected to maximum likelihood classification to delineate major land cover classes of the study area viz., water, barren, agriculture, moist deciduous forest, and sal mixed forests. Accuracy assessment of the classified map is carried out using kappa statistics. Results of the study suggested potential use of ENVISAT-ASAR C-band data in land cover classification of the study area with an overall classification accuracy of 82.5%, average producer's accuracy of 83.69%, and average user's accuracy of 81%. The present study gives a unique scope of SAR data application in land cover classification over the tropical deciduous forest systems of India, which is still waiting for its indigenous SAR system.

  19. Study on spatial variation of land subsidence over Minagish-Umm Gudair oil fields of Kuwait using synthetic aperture radar interferometry technique

    NASA Astrophysics Data System (ADS)

    Rao, Kota S.; Al Jassar, Hala K.; Kodiyan, Nevil J.; Daniel, Viju P.

    2016-01-01

    Land subsidence can be a major problem where there are large-scale underground activities such as oil extraction. This paper addresses the spatial variability of land subsidence over Minagish and Umm Gudair oil fields of Kuwait. Synthetic aperture radar interferometry (InSAR) with multiple reference scenes using a persistent scatterer InSAR toolchain was employed in this study. Twenty-nine scenes of advanced synthetic aperture radar data (for the period January 2005 to August 2009) were used to make 20 pairs of interferograms (with high coherence and low noise) of stable point-like reflectors. The output of this study is the land subsidence maps of Minagish and Umm Gudair oil fields with a spatial resolution of 40 m. The results indicate that there is land subsidence of 29.9 mm/year in the southern part of the oil field (Umm Gudair). This is the first detailed assessment of land subsidence in the Minagish-Umm Gudair oil fields; therefore, no ground-truth data are available to compare the subsidence results. The results were consistent, indicating their validity.

  20. Polarimetric C-/X-band Synthetic Aperture Radar Observations of Melting Sea Ice in the Canadian Arctic Archipelago

    NASA Astrophysics Data System (ADS)

    Casey, J. A.; Beckers, J. F.; Brossier, E.; Haas, C.

    2013-12-01

    Operational ice information services rely heavily on space-borne synthetic aperture radar (SAR) data for the production of ice charts to meet their mandate of providing timely and accurate sea ice information to support safe and efficient marine operations. During the summer melt period, the usefulness of SAR data for sea ice monitoring is limited by the presence of wet snow and melt ponds on the ice surface, which can mask the signature of the underlying ice. This is a critical concern for ice services whose clients (e.g. commercial shipping, cruise tourism, resource exploration and extraction) are most active at this time of year when sea ice is at its minimum extent, concentration and thickness. As a result, there is a need to further quantify the loss of ice information in SAR data during the melt season and to identify what information can still be retrieved about ice surface conditions and melt pond evolution at this time of year. To date the majority of studies have been limited to analysis of single-polarization C-band SAR data. This study will investigate the potential complimentary and unique sea ice information that polarimetric C- and X-band SAR data can provide to supplement the information available from traditional single co-polarized C-band SAR data. A time-series of polarimetric C- and X-band SAR data was acquired over Jones Sound in the Canadian Arctic Archipelago, in the vicinity of the Grise Fiord, Nunavut. Five RADARSAT-2 Wide Fine Quad-pol images and 11 TerraSAR-X StripMap dual-pol (HH/VV) images were acquired. The time-series begins at the onset of melt in early June and extends through advanced melt conditions in late July. Over this period several ponding and drainage events and two snowfall events occurred. Field observations of sea ice properties were collected using an Ice Mass Balance (IMB) buoy, hourly photos from a time-lapse camera deployed on a coastal cliff, and manual in situ measurements of snow thickness and melt pond depth. Where available, clear-sky data from optical sensors (MODIS, Landsat-8, and WorldView) are also used to provide supplementary information on melt pond coverage and evolution. Meteorological data are available from an Environment Canada weather station in Grise Fiord. In this presentation we will discuss the sea ice information provided by each polarization and frequency and evaluate the impact of melt pond evolution on SAR backscatter. Results to date indicate that C- and X-band provide predominantly redundant information, and cross-polarized backscatter (only acquired at C-band) is often very low and near the system noise floor. Early in the melt season a thick wet snow pack is present and both frequencies provide very little ice information. This is attributed to the strong attenuation of the microwave signal by the wet snow. At this time the underlying ice is effectively obscured. During heavily ponded periods backscatter is highly variable, attributed to changing winds and thus variable melt pond surface roughness. In the final week of observations the fast ice in the region is breaking up and open water is present in some images. In these images C-band appears to provide greater contrast between the melting ice and open water than X-band. Analysis of polarimetric parameters is ongoing.

  1. Water volume variations in Lake Izabal (Guatemala) from in situ measurements and ENVISAT Radar Altimeter (RA-2) and Advanced Synthetic Aperture Radar (ASAR) data products

    NASA Astrophysics Data System (ADS)

    Medina, Camilo; Gomez-Enri, Jesus; Alonso, Jose Juan; Villares, Pilar

    2010-03-01

    SummaryThe water storage variations in lakes affect their physical, chemical and biological processes. Besides, the water masses of these waterbodies reflect the balance of the rainfall and evaporation with surface and ground waters. The lake's water volume is estimated combining water level variations with accurate bathymetry and shore topography maps. Lake Izabal is the largest waterbody of Guatemala (approximately 673.29 km 2). Its water volume has been estimated in the past but the volume variations are still unknown. The lake water level variations are monitored in situ since 2004, but regrettably accurate information about the bathymetry and shore topography is not available. The main objective of this study was to make a first estimate of the Lake Izabal water volume variations. To do this, we combined level variations and inundated area variations. The lack of accurate bathymetry and topography maps was overcame by using inundated area variations in the assumption that every level change reflects an inundated area response, depending on bathymetry and shore topography. The level variations were estimated from an in situ moored gauged in the lake and from the ENVISAT Radar Altimeter (RA-2). The inundated area variations were obtained using 12 ENVISAT Advanced Synthetic Aperture Radar (ASAR) images. Prior to the area estimates the lake's shoreline was extracted making use of a chain of existing image processing algorithms. The correlation analysis between in situ lake levels and inundated area variations yielded a correlation coefficient of 0.9. The volume variations of the lake were then estimated on the dates of the acquired SAR images. Then, a group of rating curves relating level, area and volume were developed. In order to extend the area and volume estimates to the whole study time period (February 2003 to December 2006) the lake levels from the RA-2 dataset were entered to the rating curves. The estimated water volume variations of Lake Izabal range between 8271.2 × 10 6 m 3 (17th December of 2005) and 9018.15 × 10 6 m 3 (15th July of 2006) in agreement with the most recent estimation of the Lake Izabal water volume (8300 × 10 6 m 3). Regarding the inundated area variations, they range between 672.44 × 10 6 m 2 (17th December of 2005) and 677.2 × 10 6 m 2 (15th July of 2006) in agreement with the Guatemalan government information (673.29 km 2). The water volume, inundated area and water level fluctuations of the Lake Izabal show a strong seasonal signal with high stages during the rainy season (May-November) and low stages during the dry seasons (December-April). These results give valuable information for the Lake Izabal management and strengthen the idea of using remote sensing as a powerful and cheap complementary tool for hydrologic purposes.

  2. Synthetic aperture ladar concept for infrastructure monitoring

    NASA Astrophysics Data System (ADS)

    Turbide, Simon; Marchese, Linda; Terroux, Marc; Bergeron, Alain

    2014-10-01

    Long range surveillance of infrastructure is a critical need in numerous security applications, both civilian and military. Synthetic aperture radar (SAR) continues to provide high resolution radar images in all weather conditions from remote distances. As well, Interferometric SAR (InSAR) and Differential Interferometric SAR (D-InSAR) have become powerful tools adding high resolution elevation and change detection measurements. State of the art SAR systems based on dual-use satellites are capable of providing ground resolutions of one meter; while their airborne counterparts obtain resolutions of 10 cm. D-InSAR products based on these systems could produce cm-scale vertical resolution image products. Deformation monitoring of railways, roads, buildings, cellular antennas, power structures (i.e., power lines, wind turbines, dams, or nuclear plants) would benefit from improved resolution, both in the ground plane and vertical direction. The ultimate limitation to the achievable resolution of any imaging system is its wavelength. State-of-the art SAR systems are approaching this limit. The natural extension to improve resolution is to thus decrease the wavelength, i.e. design a synthetic aperture system in a different wavelength regime. One such system offering the potential for vastly improved resolution is Synthetic Aperture Ladar (SAL). This system operates at infrared wavelengths, ten thousand times smaller than radar wavelengths. This paper presents a laboratory demonstration of a scaled-down infrastructure deformation monitoring with an Interferometric Synthetic Aperture Ladar (IFSAL) system operating at 1.5 ?m. Results show sub-millimeter precision on the deformation applied to the target.

  3. Improving the TanDEM-X DEM for flood modelling using flood extents from Synthetic Aperture Radar images.

    NASA Astrophysics Data System (ADS)

    Mason, David; Trigg, Mark; Garcia-Pintado, Javier; Cloke, Hannah; Neal, Jeffrey; Bates, Paul

    2015-04-01

    Many floodplains in the developed world have now been imaged with high resolution airborne LiDAR or InSAR, giving accurate DEMs that facilitate accurate flood inundation modelling. This is not always the case for remote rivers in developing countries. However, the accuracy of DEMs produced for modelling studies on such rivers should be enhanced in the near future by the high resolution TanDEM-X World DEM. In a parallel development, increasing use is now being made of flood extents derived from high resolution SAR images for calibrating, validating and assimilating observations into flood inundation models in order to improve these. The paper discusses an additional use of SAR flood extents to improve the accuracy of the TanDEM-X DEM in the floodplain covered by the flood extents, thereby permanently improving the DEM for future flood modelling studies in this area. The method is based on the fact that for larger rivers the water elevation changes only slowly along a reach, so that the boundary of the flood extent (the waterline) can be regarded locally as a quasi-contour. As a result, heights of adjacent pixels along a small section of waterline can be regarded as a sample of heights with a common population mean. The height of the central pixel in the section can be replaced with the average of these heights, leading to a more accurate height estimate. While this will result in a reduction in the height errors along a waterline, the waterline is a linear feature in a two-dimensional space. However, improvements to the DEM heights between adjacent pairs of waterlines can also be made, because DEM heights enclosed by the higher waterline of a pair must be at least no higher than the refined heights along the higher waterline, whereas DEM heights not enclosed by the lower waterline must be no lower than the refined heights along the lower waterline. In addition, DEM heights between the higher and lower waterlines can also be assigned smaller errors because of the reduced errors on the refined waterline heights. The method was tested on a section of the TanDEM-X Intermediate DEM (IDEM) covering an 11km reach of the Warwickshire Avon, England. Flood extents from four COSMO-SKyMed images were available at various stages of a flood in November 2012. Waterlines were detected automatically using the method described in [1]. The 12.5m resolution IDEM was re-sampled to the 2.5m resolution of the CSK images using nearest neighbour interpolation. Improvements to the IDEM were attempted only in regions of low slope and low vegetation, so that the DEM could be regarded as the DTM. The height of a pixel on a waterline was replaced by the average of the waterline pixel heights in an 11 x 11 IDEM pixel window centred on the current CSK pixel (but selecting only one waterline height per IDEM pixel to reduce correlations). Original and refined IDEM heights were compared to corresponding airborne LiDAR heights. Along the waterlines, it was found that the original IDEM heights had a standard deviation of 1.1m and a bias of 0.2m, while the refined heights had a standard deviation of only 0.6m and a similar bias. Between two adjacent waterlines, on average approximately 25% of IDEM heights were above the higher waterline, and 20% below the lower waterline. When compared to LiDAR, the original higher heights had a mean difference from the LiDAR height of 2.4m with standard deviation 3.0m, while after correction the mean difference was 0.5m with standard deviation 1.0m. The corrected heights below the lower waterline were similarly improved. The height errors of a further 40% of IDEM heights between the higher and lower waterlines were also reduced, because of the reduced errors on the refined waterline heights. 1. Mason DC, Davenport IJ, Neal JC, Schumann GJ-P and Bates PD (2012). Near real-time flood detection in urban and rural areas using high resolution Synthetic Aperture Radar images. IEEE. Trans. Geoscience Rem. Sens., 50(8), 3041-3052.

  4. Two-dimensional superresolution multiple-input multiple-output and inverse synthetic aperture radar imaging based on spatial frequency ambiguity resolving

    NASA Astrophysics Data System (ADS)

    Yang, Jianchao; Su, Weimin; Gu, Hong

    2015-01-01

    Combining multiple-input multiple-output (MIMO) radar and inverse synthetic aperture radar (ISAR) techniques can reduce the number of antennas used and shorten the radar integrated time compared with the single-channel ISAR for the same cross-range resolution. In existing MIMO-ISAR processing, the echoes of different sensors are rearranged into an equivalent single-channel ISAR signal. A new method without echo rearrangement is proposed for two-dimensional (2-D) MIMO-ISAR imaging. A 2-D frequency estimation algorithm based on Unitary ESPRIT and projection transformation is used to obtain the spatial and Doppler frequencies of scatterers, and a high cross-range resolution can be achieved. The relationship between the two frequencies is exploited to resolve the ambiguity of spatial frequency. The analysis and simulation results show that, compared with the existing method, the proposed method can decrease the relative rotation angle (or integrated time) required for imaging. Thus, this method is more suitable for imaging targets with limited rotation or high maneuvering.

  5. Inverse synthetic aperture radar imaging of targets with complex motions based on modified chirp rate-quadratic chirp rate distribution for cubic phase signal

    NASA Astrophysics Data System (ADS)

    Yanyan, Li; Tao, Su; Jibin, Zheng

    2015-01-01

    For targets with complex motions, the time-varying Doppler frequency deteriorates inverse synthetic aperture radar (ISAR) images. After range alignment and phase adjustment, azimuth echoes in a range cell can be modeled as multicomponent cubic phase signals (CPSs). The chirp rate and the quadratic chirp rate of the CPS are identified as the causes of the time-varying Doppler frequency; thus, it is necessary to estimate these two parameters correctly to obtain a well-focused ISAR image. The parameter-estimation algorithm based on the modified chirp rate-quadratic chirp rate distribution (M-CRQCRD) is proposed for the CPS and applied to the ISAR imaging of targets with complex motions. The computational cost of M-CRQCRD is low, because it can be implemented by the fast Fourier transform (FFT) and the nonuniform FFT easily. Compared to two representative parameter-estimation algorithms, the M-CRQCRD can acquire a higher antinoise performance due to the introduction of an optimal lag-time. Through simulations and analyses for the synthetic radar data, the effectiveness of the M-CRQCRD and the imaging algorithm based on the M-CRQCRD are verified.

  6. Spaceborne synthetic aperture radar: Current status and future directions. A report to the Committee on Earth Sciences, Space Studies Board, National Research Council

    NASA Technical Reports Server (NTRS)

    Evans, D. L. (Editor); Apel, J.; Arvidson, R.; Bindschadler, R.; Carsey, F.; Dozier, J.; Jezek, K.; Kasischke, E.; Li, F.; Melack, J.

    1995-01-01

    This report provides a context in which questions put forth by NASA's Office of Mission to Planet Earth (OMPTE) regarding the next steps in spaceborne synthetic aperture radar (SAR) science and technology can be addressed. It summarizes the state-of-the-art in theory, experimental design, technology, data analysis, and utilization of SAR data for studies of the Earth, and describes potential new applications. The report is divided into five science chapters and a technology assessment. The chapters summarize the value of existing SAR data and currently planned SAR systems, and identify gaps in observational capabilities needing to be filled to address the scientific questions. Cases where SAR provides complementary data to other (non-SAR) measurement techniques are also described. The chapter on technology assessment outlines SAR technology development which is critical not only to NASA's providing societally relevant geophysical parameters but to maintaining competitiveness in SAR technology, and promoting economic development.

  7. Glacial Rebound Due to Present Day Ice Loss on Greenland Ice Sheet and Canadian Arctic Archipelago Observed by Synthetic Aperture Radar Interferometry

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Amelung, F.; Samsonov, S. V.; Dixon, T. H.; Wdowinski, S.

    2013-12-01

    Synthetic Aperture Radar Interferometry (InSAR) has been used to measure glacial rebound and estimate ice mass balance in recent years. Relevant studies have covered Jakobshavn Isbrea glacial, Greenland, Vatnajokull Iceland and Antarctic Peninsula by using Radarsat-1, ERS and Alos imagery. We focus on other 2 main contributors to global sea level rise (SLR) in the north Atlantic Region - the Greenland Ice Sheet (GIS) and the Canadian Arctic Archipelago (CAA) in this presentation. We choose a series of test sites on GIS and 1 test site on CAA - Barnes ice cap. New generation SAR satellites Radarsat-2 and TerraSAR-X are applied to these 2 regions respectively. Initial results show the ability that the new satellites data is useful for not only annual velocity but also seasonal variation detections.

  8. Hunt for forgotten warplanes: a unique application for the Goddard Space Flight Center Search and Rescue Synthetic Aperture Radar (SAR2) program

    NASA Astrophysics Data System (ADS)

    Yagen, Gerald; Jackson, Christopher R.

    1998-09-01

    The principal purpose of the Beaconless Search and Rescue program at Goddard Space Flight Center (GSFC) is to utilize synthetic aperture radar (SAR) for the efficient and rapid location of recent small aircraft crashes. An additional side benefit might prove to be the detection and discovery of long lost or forgotten historic aircraft that have now become of immense value for museum display or among wealthy collectors. As the GSFC SAR2 program matures and its achievements in SAR target detection become more widely available, they will be of use to amateur and professional airplane hunters. We recommend that such ancillary benefits be kept in mind during the continued development and testing of such equipment, which would be of benefit to all future generations concerning the history of aviation. We welcome and encourage all participants to notify organizations such as ours of the discovery of any historic aircraft wreckage or intact abandoned old aircraft throughout the world.

  9. Application of SEASAT-1 Synthetic Aperture Radar (SAR) data to enhance and detect geological lineaments and to assist LANDSAT landcover classification mapping. [Appalachian Region, West Virginia

    NASA Technical Reports Server (NTRS)

    Sekhon, R.

    1981-01-01

    Digital SEASAT-1 synthetic aperture radar (SAR) data were used to enhance linear features to extract geologically significant lineaments in the Appalachian region. Comparison of Lineaments thus mapped with an existing lineament map based on LANDSAT MSS images shows that appropriately processed SEASAT-1 SAR data can significantly improve the detection of lineaments. Merge MSS and SAR data sets were more useful fo lineament detection and landcover classification than LANDSAT or SEASAT data alone. About 20 percent of the lineaments plotted from the SEASAT SAR image did not appear on the LANDSAT image. About 6 percent of minor lineaments or parts of lineaments present in the LANDSAT map were missing from the SEASAT map. Improvement in the landcover classification (acreage and spatial estimation accuracy) was attained by using MSS-SAR merged data. The aerial estimation of residential/built-up and forest categories was improved. Accuracy in estimating the agricultural and water categories was slightly reduced.

  10. Multitemporal L- and C-Band Synthetic Aperture Radar To Highlight Differences in Water Status Among Boreal Forest and Wetland Systems in the Yukon Flats, Interior Alaska

    USGS Publications Warehouse

    Balser, Andrew W.; Wylie, Bruce K.

    2010-01-01

    Tracking landscape-scale water status in high-latitude boreal systems is indispensible to understanding the fate of stored and sequestered carbon in a climate change scenario. Spaceborne synthetic aperture radar (SAR) imagery provides critical information for water and moisture status in Alaskan boreal environments at the landscape scale. When combined with results from optical sensor analyses, a complementary picture of vegetation, biomass, and water status emerges. Whereas L-band SAR showed better inherent capacity to map water status, C-band had much more temporal coverage in this study. Analysis through the use of L- and C-band SARs combined with Landsat Enhanced Thematic Mapper Plus (ETM+) enables landscape stratification by vegetation and by seasonal and interannual hydrology. Resultant classifications are highly relevant to biogeochemistry at the landscape scale. These results enhance our understanding of ecosystem processes relevant to carbon balance and may be scaled up to inform regional carbon flux estimates and better parameterize general circulation models (GCMs).

  11. Rupture parameters of the 2003 Zemmouri (Mw 6.8), Algeria, earthquake from joint inversion of interferometric synthetic aperture radar, coastal uplift, and GPS

    USGS Publications Warehouse

    Belabbes, S.; Wicks, C.; Cakir, Z.; Meghraoui, M.

    2009-01-01

    We study the surface deformation associated with the 21 May 2003 (M w = 6.8) Zemmouri (Algeria) earthquake, the strongest seismic event felt in the Algiers region since 1716. The thrust earthquake mechanism and related surface deformation revealed an average 0.50 m coastal uplift along ??55-km-long coastline. We obtain coseismic interferograms using Envisat advanced synthetic aperture radar (ASAR) (IS2) and RADARSAT standard beam (ST4) data from both the ascending and descending orbits of Envisat satellite, whereas the RADARSAT data proved useful only in the descending mode. While the two RADARSAT interferograms cover the earthquake area, Envisat data cover only the western half of the rupture zone. Although the interferometric synthetic aperture radar (InSAR) coherence in the epicenter area is poor, deformation fringes are observed along the coast in different patches. In the Boumerdes area, the maximum coseismic deformation is indicated by the high gradient of fringes visible in all interferograms in agreement with field measurements (tape, differential GPS, leveling, and GPS). To constrain the earthquake rupture parameters, we model the interferograms and uplift measurements using elastic dislocations on triangular fault patches in an elastic and homogeneous half-space. We invert the coseismic slip using first, a planar surface and second, a curved fault, both constructed from triangular elements using Poly3Dinv program that uses a damped least square minimization. The best fit of InSAR, coastal uplift, and GPS data corresponds to a 65-km-long fault rupture dipping 40?? to 50?? SE, located at 8 to 13 km offshore with a change in strike west of Boumerdes from N60??-65?? to N95??-105??. The inferred rupture geometry at depth correlates well with the seismological results and may have critical implications for the seismic hazard assessment of the Algiers region. Copyright 2009 by the American Geophysical Union.

  12. Integrating the probability integral method for subsidence prediction and differential synthetic aperture radar interferometry for monitoring mining subsidence in Fengfeng, China

    NASA Astrophysics Data System (ADS)

    Diao, Xinpeng; Wu, Kan; Zhou, Dawei; Li, Liang

    2016-01-01

    Differential synthetic aperture radar interferometry (D-InSAR) is characterized mainly by high spatial resolution and high accuracy over a wide coverage range. Because of its unique advantages, the technology is widely used for monitoring ground surface deformations. However, in coal mining areas, the ground surface can suffer large-scale collapses in short periods of time, leading to inaccuracies in D-InSAR results and limiting its use for monitoring mining subsidence. We propose a data-processing method that overcomes these disadvantages by combining D-InSAR with the probability integral method used for predicting mining subsidence. Five RadarSat-2 images over Fengfeng coal mine, China, were used to demonstrate the proposed method and assess its effectiveness. Using this method, surface deformation could be monitored over an area of thousands of square kilometers, and more than 50 regions affected by subsidence were identified. For Jiulong mine, nonlinear subsidence cumulative results were obtained for a time period from January 2011 to April 2011, and the maximum subsidence value reached up to 299 mm. Finally, the efficiency and applicability of the proposed method were verified by comparing with data from leveling surveying.

  13. Three-dimensional interferometric inverse synthetic aperture radar imaging of maneuvering target based on the joint cross modified Wigner-Ville distribution

    NASA Astrophysics Data System (ADS)

    Lv, Qian; Su, Tao; Zheng, Jibin; Zhang, Jiancheng

    2016-01-01

    Inverse synthetic aperture radar (ISAR) can achieve high-resolution two-dimensional images of maneuvering targets. However, due to the indeterminate relative motion between radar and target, ISAR imaging does not provide the three-dimensional (3-D) position information of a target and suffers from great difficulty in target recognition. To tackle this issue, a 3-D interferometric ISAR (InISAR) imaging algorithm based on the joint cross modified Wigner-Ville distribution (MWVD) is presented to form 3-D images of maneuvering targets. First, we form two orthogonal interferometric baselines with three receiving antennas to establish an InISAR imaging system. Second, after the uniform range alignment and phase adjustment, the joint cross MWVD is used for all range cell of each antenna pair to generate the separation of the scatterer as well as preserve the phase that contains position information of the scatterer. At last, the 3-D images of the target can be directly reconstructed from the distribution. Simulation results demonstrate the validity of the proposal.

  14. Crop monitoring & yield forecasting system based on Synthetic Aperture Radar (SAR) and process-based crop growth model: Development and validation in South and South East Asian Countries

    NASA Astrophysics Data System (ADS)

    Setiyono, T. D.

    2014-12-01

    Accurate and timely information on rice crop growth and yield helps governments and other stakeholders adapting their economic policies and enables relief organizations to better anticipate and coordinate relief efforts in the wake of a natural catastrophe. Such delivery of rice growth and yield information is made possible by regular earth observation using space-born Synthetic Aperture Radar (SAR) technology combined with crop modeling approach to estimate yield. Radar-based remote sensing is capable of observing rice vegetation growth irrespective of cloud coverage, an important feature given that in incidences of flooding the sky is often cloud-covered. The system allows rapid damage assessment over the area of interest. Rice yield monitoring is based on a crop growth simulation and SAR-derived key information, particularly start of season and leaf growth rate. Results from pilot study sites in South and South East Asian countries suggest that incorporation of SAR data into crop model improves yield estimation for actual yields. Remote-sensing data assimilation into crop model effectively capture responses of rice crops to environmental conditions over large spatial coverage, which otherwise is practically impossible to achieve. Such improvement of actual yield estimates offers practical application such as in a crop insurance program. Process-based crop simulation model is used in the system to ensure climate information is adequately captured and to enable mid-season yield forecast.

  15. Coseismic deformation associated with the November 1995, MW = 7.1 Nuweiba earthquake, Gulf of Elat (Aqaba), detected by synthetic aperture radar interferometry

    NASA Astrophysics Data System (ADS)

    Baer, Gidon; Sandwell, David; Williams, Simon; Bock, Yehuda; Shamir, Gadi

    1999-11-01

    The November 22, 1995, MW = 7.1 Nuweiba earthquake occurred along one of the left-stepping segments of the Dead Sea Transform in the Gulf of Elat (Aqaba). Although it was the largest earthquake along this fault in the last few centuries, little is yet known about the geometry of the rupture, the slip distribution along it, and the nature of postseismic deformation following the main shock. In this study we examine the surface deformation pattern during the coseismic phase of the earthquake in an attempt to better elucidate the earthquake rupture process. As the entire rupture zone was beneath the waters of the Gulf, and there is very little Global Positioning System (GPS) data available in the region for the period spanning the earthquake, interferometric synthetic aperture radar (INSAR) provides the only source of information of surface deformation associated with this earthquake. We chose four synthetic aperture radar (SAR) scenes of about 90 × 90 km each spanning the rupture area, imaged by the ERS-1 and ERS-2 satellites. The coseismic interferograms show contours of equal satellite-to-ground range changes that correspond to surface displacements due to the earthquake rupture. Interferograms that span the earthquake by 1 week show similar fringe patterns as those that span the earthquake by 6 months, suggesting that postseismic deformation is minor or confined to the first week after the earthquake. A high displacement gradient is seen on the western side of the Gulf, 20-40 km south of Elat and Aqaba, where the total satellite-to-ground range changes are at least 15 cm. The displacement gradient is relatively uniform on the eastern side of the Gulf, and the range changes are less than 10 cm. To interpret these results, we compare them to synthetic interferograms generated by elastic dislocation models with a variety of fault parameters. Although selecting the best fit fault parameters is nonunique, we are able to generate a group of simplified model interferograms that provide a reasonable fit to the coseismic interferogram and serve to constrain the location of the fault. The present analysis shows that if the rupture reached the Gulf-bottom surface, the mean sinistral slip along the fault is constrained to about 1.4 m. If surface rupture did not occur, the average sinistral slip is constrained to the range of 1.4-3 m for a fault patch buried 0-4 km below the Gulf-bottom surface, respectively, with a minor normal component.

  16. Modeling Collapse Chimney and Spall Zone Settlement as a Source of Post-Shot Subsidence Detected by Synthetic Aperture Radar Interferometry

    SciTech Connect

    Foxwall, W.

    2000-07-24

    Ground surface subsidence resulting from the March 1992 JUNCTION underground nuclear test at the Nevada Test Site (NTS) imaged by satellite synthetic aperture radar interferometry (InSAR) wholly occurred during a period of several months after the shot (Vincent et al., 1999) and after the main cavity collapse event. A significant portion of the subsidence associated with the small (less than 20 kt) GALENA and DIVIDER tests probably also occurred after the shots, although the deformation detected in these cases contains additional contributions from coseismic processes, since the radar scenes used to construct the deformation interferogram bracketed these two later events, The dimensions of the seas of subsidence resulting from all three events are too large to be solely accounted for by processes confined to the damage zone in the vicinity of the shot point or the collapse chimney. Rather, the subsidence closely corresponds to the span dimensions predicted by Patton's (1990) empirical relationship between spall radius and yield. This suggests that gravitational settlement of damaged rock within the spall zone is an important source of post-shot subsidence, in addition to settlement of the rubble within the collapse chimney. These observations illustrate the potential power of InSAR as a tool for Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring and on-site inspection in that the relatively broad ({approx} 100 m to 1 km) subsidence signatures resulting from small shots detonated at normal depths of burial (or even significantly overburied) are readily detectable within large geographical areas (100 km x 100 km) under favorable observing conditions. Furthermore, the present results demonstrate the flexibility of the technique in that the two routinely gathered satellite radar images used to construct the interferogram need not necessarily capture the event itself, but can cover a time period up to several months following the shot.

  17. Mapping Exposed and Buried Lava Flows Using Synthetic Aperture and Ground-Penetrating Radar in Craters of the Moon Lava Field

    NASA Astrophysics Data System (ADS)

    Khan, S. D.; Heggy, E.; Fernandez, J.

    2007-10-01

    The Craters of the Moon (COM) lava field in central Idaho has a multiple eruptive history. Burial of older flows by younger eruptive events has resulted in complex surface geomorphology and subsurface stratigraphy. For the older eruptive periods, the locations of source vents and the extension of lava flows are either speculative or unknown, as they are buried under earlier pyroclastistics. In this study, we used surface and subsurface backscatter characteristics of the P- and L-band polarimetric Airborne Synthetic Aperture Radar (AIRSAR) data and Ground-Penetrating Radar (GPR) soundings to resolve different exposed and buried lava flows. Our primary objective is to define the most effective polarization and frequency for mapping, resolving, and characterizing different lava types in the volcanic field. Polarimetric analysis of AIRSAR images from COM allows a clear recognition of the aa' and pahoehoe lava types as a result of the variability in their roughness. Our results suggest that the HV cross-polarized, AIRSAR L band is capable of producing a detailed map delineating surface lava with different surface backscattering properties. An accuracy assessment utilizing the geological map of the Inferno Cone area and in situ observations showed a significant reliability of differentiating lava types and mapping the lava flows extension below loose pyroclastics using AIRSAR data. The P-band, results suggest a constrained ability for mapping buried structures up to 3 meters deep under loose and dry cinder and ash deposits, resolving buried fissures, outcrops, and lava flows that were validated with ground-truth GPR surveys. Investigating subsurface stratigraphy with remote sensing and GPR techniques can be applied in other arid locations on Earth and other planets. Analyzing the radar backscattering penetration depth at higher frequencies is valuable for future planetary subsurface exploration missions for telluric planets.

  18. Synthetic aperture integration (SAI) algorithm for SAR imaging

    SciTech Connect

    Chambers, David H; Mast, Jeffrey E; Paglieroni, David W; Beer, N. Reginald

    2013-07-09

    A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

  19. Potential of high-resolution detection and retrieval of precipitation fields from X-band spaceborne synthetic aperture radar over land

    NASA Astrophysics Data System (ADS)

    Marzano, F. S.; Mori, S.; Chini, M.; Pulvirenti, L.; Pierdicca, N.; Montopoli, M.; Weinman, J. A.

    2011-03-01

    X-band Synthetic Aperture Radars (X-SARs), able to image the Earth's surface at metric resolution, may provide a unique opportunity to measure rainfall over land with spatial resolution of about few hundred meters, due to the atmospheric moving-target degradation effects. This capability has become very appealing due to the recent launch of several X-SAR satellites, even though several remote sensing issues are still open. This work is devoted to: (i) explore the potential of X-band high-resolution detection and retrieval of rainfall fields from space using X-SAR signal backscattering amplitude and interferometric phase; (ii) evaluate the effects of spatial resolution degradation by precipitation and inhomogeneous beam filling when comparing to other satellite-based sensors. Our X-SAR analysis of precipitation effects has been carried out using both a TerraSAR-X (TSX) case study of Hurricane "Gustav" in 2008 over Mississippi (USA) and a COSMO-SkyMed (CSK) X-SAR case study of orographic rainfall over Central Italy in 2009. For the TSX case study the near-surface rain rate has been retrieved from the normalized radar cross section by means of a modified regression empirical algorithm (MREA). A relatively simple method to account for the geometric effect of X-SAR observation on estimated rainfall rate and first-order volumetric effects has been developed and applied. The TSX-retrieved rain fields have been compared to those estimated from the Next Generation Weather Radar (NEXRAD) in Mobile (AL, USA). The rainfall detection capability of X-SAR has been tested on the CSK case study using the repeat-pass coherence response and qualitatively comparing its signature with ground-based Mt. Midia C-band radar in central Italy. A numerical simulator to represent the effect of the spatial resolution and the antenna pattern of TRMM satellite Precipitation Radar (PR) and Microwave Imager (TMI), using high-resolution TSX-retrieved rain images, has been also set up in order to evaluate the rainfall beam filling phenomenon. As expected, the spatial average can modify the statistics of the high-resolution precipitation fields, strongly reducing its dynamics in a way non-linearly dependent on the rain rate local average value.

  20. Structural and stratigraphic features and ERS 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in NW Alaska, winter 1991-1992

    NASA Technical Reports Server (NTRS)

    Jeffries, M. O.; Morris, K.; Weeks, W. F.; Wakabayashi, H.

    1994-01-01

    Changes in Earth Remote-Sensing Satellite (ERS) 1 C band synthetic aperture radar (SAR) backscatter intensity (sigma(exp 0)) from ice growing on shallow tundra lakes at three locations in NW Alaska are described. Ice core analysis shows that all lakes on the coast at Barrow the ice, whether floating or frozen to the bottom, includes an inclusion-free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth. The clear ice may also be overlain by a discontinuous layer of bubbly snow ice. Backscatter is low (-16 to -22 dB) at the time of initial ice formation, probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar. As the ice thickens during the autumn, backscatter rises steadily. Once the ice freezes to the lake bottom, regardless of the presence of foward scattering tubular bubbles, low backscatter values of -17 to -18 dB are caused by absorption of the radar signal in the lake bed. For ice that remains afloat all winter the ice-water interface and the tubular bubbles combine, presumably via an incoherent double-bounce mechanism, to cause maximum backscatter values of the order of -6 to -7 dB. The sigma(exp 0) saturates at -6 to -7 dB before maximum ice thickness and tubular bubble content are attained. A simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice. During the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland. This reversal may be related to the ice surface topography and wetness plus the effects of a longer, cooler melt period by the coast. Time series of backscatter variations from shallow tundra lakes are a record of (1) the development of tubular bubbles in the ice and, by association, changes in the gas content of the underlying water and (2) the freezing of ice to the bottoms of the lakes and therefore lake bathymetry and water availability. SAR is also able to detect the onset of lake ice growth in autumn and the initiation of the spring thaw and thus has potential for monitoring high-altitude lake ice growth and decay processes in relation to climate variability.

  1. Analysis of data acquired by synthetic aperture radar and LANDSAT Multispectral Scanner over Kershaw County, South Carolina, during the summer season

    NASA Technical Reports Server (NTRS)

    Wu, S. T.

    1983-01-01

    Data acquired by synthetic aperture radar (SAR) and LANDSAT multispectral scanner (MSS) were processed and analyzed to derive forest-related resources inventory information. The SAR data were acquired by using the NASA aircraft X-band SAR with linear (HH, VV) and cross (HV, VH) polarizations and the SEASAT L-band SAR. After data processing and data quality examination, the three polarization (HH, HV, and VV) data from the aircraft X-band SAR were used in conjunction with LANDSAT MSS for multisensor data classification. The results of accuracy evaluation for the SAR, MSS and SAR/MSS data using supervised classification show that the SAR-only data set contains low classification accuracy for several land cover classes. However, the SAR/MSS data show that significant improvement in classification accuracy is obtained for all eight land cover classes. These results suggest the usefulness of using combined SAR/MSS data for forest-related cover mapping. The SAR data also detect several small special surface features that are not detectable by MSS data.

  2. Assessing the Bayesian inversion technique of C-band synthetic aperture radar data for the retrieval of wind fields in marine coastal areas

    NASA Astrophysics Data System (ADS)

    Adamo, Maria; Rana, Fabio Michele; De Carolis, Giacomo; Pasquariello, Guido

    2014-01-01

    Over the past decade, synthetic aperture radar (SAR) sensors have demonstrated their ability to provide accurate wind speed and direction measurements in the ocean. Although SAR capability to image the sea surface at a suitable spatial resolution, SAR wind field retrieval in marine coastal areas still remains an open issue. The aim of this work is to assess the potential and limits of the Bayesian approach to the C-band NRCS SAR inversion problem for the retrieval of wind fields in marine coastal areas. A dataset of 139 SAR images gathered by the European ERS-2 and ENVISAT satellites during 2007 was analyzed to estimate the sea surface wind vectors over three selected coastal sites in the Mediterranean Sea, offshore Puglia region (Italy). The sites were instrumented to monitor marine and environmental parameters, including wind intensity and direction for further comparison with SAR wind estimations. Results discussed in this study show that the statistical approach in the retrieval of SAR wind speed can be applied in coastal areas with performances comparable with those obtained off-shore. In contrast, the SAR inversion procedure was not able to retrieve wind direction with the same accuracy.

  3. Time series synthetic aperture radar interferometry over the multispan cable-stayed Rio-Antirio Bridge (central Greece): achievements and constraints

    NASA Astrophysics Data System (ADS)

    Parcharidis, Issaak; Foumelis, Michael; Benekos, George; Kourkouli, Penelope; Stamatopoulos, Constantine; Stramondo, Salvatore

    2015-01-01

    The aim of the present study is to monitor by means of multitemporal synthetic aperture radar (SAR) interferometry the stability of the fully suspended cable-stayed Rio-Antirio Bridge (RAB) as well as the ground deformation of its surrounding area. The bridge is located in a region characterized by high hazard susceptibility, therefore, the monitoring of its behavior is of significant interest to mitigate potential risks. Envisat ASAR descending and TerraSAR-X ascending acquisitions were exploited using the persistent scatterer interferometry technique covering the periods 2002 to 2010 and 2010 to 2012, respectively. For both periods, ground displacement rates ranging from -12 to +12 mm/year indicate the absence of a significant deformation source acting during the period of investigation. Of interest is the differential motion pattern between Rio and Antirio for both SAR geometries, signifying the contribution of horizontal motion components, meanwhile allowing the quantification of the relative vertical displacement rates of these regions. For the RAB infrastructure, displacement histories were obtained from TerraSAR-X data analysis only for the stable part of the bridge, namely the viaducts and the four pylons, possibly due to the oscillation of its suspended part and the uncertainty of phase measurements over the pavement. The common behavior of the pylons was confirmed with an overall subsidence between -2 and -3 mm/year. The highest rates were observed for pylons established on specific soil types and were attributed to sediment consolidation.

  4. Ground displacements caused by aquifer-system water-level variations observed using interferometric synthetic aperture radar near Albuquerque, New Mexico

    USGS Publications Warehouse

    Heywood, Charles E.; Galloway, Devin L.; Stork, Sylvia V.

    2002-01-01

    Six synthetic aperture radar (SAR) images were processed to form five unwrapped interferometric (InSAR) images of the greater metropolitan area in the Albuquerque Basin. Most interference patterns in the images were caused by range displacements resulting from changes in land-surface elevation. Loci of land- surface elevation changes correlate with changes in aquifer-system water levels and largely result from the elastic response of the aquifer-system skeletal material to changes in pore-fluid pressure. The magnitude of the observed land-surface subsidence and rebound suggests that aquifer-system deformation resulting from ground-water withdrawals in the Albuquerque area has probably remained in the elastic (recoverable) range from July 1993 through September 1999. Evidence of inelastic (permanent) land subsidence in the Rio Rancho area exists, but its relation to compaction of the aquifer system is inconclusive because of insufficient water-level data. Patterns of elastic deformation in both Albuquerque and Rio Rancho suggest that intrabasin faults impede ground- water-pressure diffusion at seasonal time scales and that these faults are probably important in controlling patterns of regional ground-water flow.

  5. NOAA satellite ocean remote sensing near real-time system for providing synthetic aperture radar data for marine and coastal applications

    SciTech Connect

    Pichel, W.G.; Stone, R.N.; Tseng, W.

    1997-06-01

    The National Environmental Satellite, Data, and Information Service (NESDIS) of the National Oceanic and Atmospheric Administration (NOAA) in partnership with the National Aeronautics and Space Administration, the Naval Oceanographic Office, the Naval Research Laboratory (NRL), the University of Alaska at Fairbanks (UAF), and the Canadian Ice Service has constructed a near real-time data system for providing satellite synthetic aperture radar (SAR) imagery to U.S. Government users. Data processed in near real-time at the Alaska SAR Facility of the UAF, at the Gatineau Ground Station in Canada, and the Tromso Satellite Station in Norway (with the McMurdo Ground Station in Antarctica to be added in the future), are brought electronically to the NOAA/NESDIS Satellite Active Archive where they are provided to US Government subscribers in near real-time or retrospectively. A SAR data display and analysis system developed by NRL is provided to users to aid in applying these data to marine and coastal environmental problems. Targeted applications include operational sea and lake ice analysis, river ice jam monitoring, flood mapping, oil spill tracking, ocean feature detection, fisheries management and enforcement, fisheries studies, and river plume monitoring. Initial coastal and marine users include the US National Ice Center, the NOAA CoastWatch Regional Nodes and the US Coast Guard.

  6. Slope instability and post-emplacement lava flow deformation revealed using interferometric synthetic aperture radar (InSAR) at Pacaya Volcano, Guatemala

    NASA Astrophysics Data System (ADS)

    Schaefer, L. N.; Lu, Z.; Oommen, T.

    2014-12-01

    Pacaya Volcano, Guatemala, is a dominantly basaltic complex that has been continually active since the 1960's, with over 250 lava flows, intermittent strombolian activity, and ash and fumerolic plumes. Sometime between 0.6 and 1.6 ka B.P., the SW sector of the initial cone failed in a major edifice collapse. This event left a large arcuate scarp, within which the modern cone was constructed from historical times up to the present. Two collapses on the upper flanks of the cone near the main vent in 1962 and 2010, and uneven loading of lava flows on the SW flank are a cause for concern about the stability of this young edifice. For this study, ALOS PALSAR L-band Interferometric Synthetic Aperture Radar (InSAR) data was analyzed at Pacaya from February 2007 - February 2011. Interferograms reveal several applications of InSAR for understanding and monitoring activity at Pacaya, including: (1) lava cooling-related compaction during effusive activity, (2) inflation on the northern side of the cone prior to a large eruption on May 27th, 2010, and (3) movement of the edifice to the SW during this large eruption, suggesting large-scale flank instability. With the implementation of InSAR technology at Pacaya in the future, we may be able to provide insights into the post-emplacement behavior of lava flows and shed light on edifice stability, leading to improved volcano hazard assessments.

  7. Flood disaster monitoring in Thailand by using a airborne L-band SAR: Polarimetric and interferometry Synthetic Aperture Radar with L-band(Pi-SAR-L)

    NASA Astrophysics Data System (ADS)

    Kawano, N.; Sobue, S.; Shimada, M.; Ohyoshi, K.

    2012-04-01

    It was heavy rainfall around the northern region of Thailand from July to September 2011, which caused flood disaster to quite wide region of Thailand, it finally reached to the Bangkok central in the end of October 2011. Japan Aerospace Exploration Agency (JAXA) conducted an emergency observation by using a airborne L-band SAR: Polarimetric and interferometry Synthetic Aperture Radar with L-band(Pi-SAR-L) from 5th to 27th November to monitor flood area. Pi-SAR-L has a center frequency of 1271.5 MHz, a band width of 50 MHz, a slant range resolution of 3 m, and an acquisition swath of 15 km on the ground. Pi-SAR-L is boarded on an aircraft of the Gulfstream-II operated by the Diamond Air Service(DAS), Japan, and the Gulfstream-II was ferried to the Chieng-Mai airport in the North Thailand, from Japan. In our presentation, we will show flood area around Bangkok and its variations detected by Pi-SAR-L

  8. Urban change detection with polarimetric Advanced Land Observing Satellite phased array type L-band synthetic aperture radar data: a case study of Tai'an, China

    NASA Astrophysics Data System (ADS)

    Xu, Jinyan; Zhang, Lu; Wang, Yong; Wang, He; Liao, Mingsheng

    2013-01-01

    Change detection in Tai'an city of eastern China using a pair of qual-polarimetric Advanced Land Observing Satellite phased array type L-band synthetic aperture radar (ALOS PALSAR) data was studied. The procedures consisted of polarimetric features extraction, optimal polarimetric feature group selection, supervised classification, and result accuracy assessment. Feature extraction from PALSAR data was performed first, and then the polarimetric features were categorized into several groups. Polarimetric optimum index factor (POIF) and distance factor (DF) were selected to measure and evaluate the suitability of each feature group for urban change detection. The best group of features was identified including linear polarization correlation coefficient (?), right-left (R-L) circular polarization correlation coefficient (?), total power (TP), and cross-polarization isolation (XPI). Afterward, four difference images of the identified features extracted from the two PALSAR data were derived, respectively. Then, the random forest (RF) classifier was employed to perform a supervised classification of the four difference images. Three classes were quantified, including no-change, change from undeveloped area to developed area, and vice versa. The overall accuracy of change detection was about 84% and Cohen's Kappa coefficient was 0.71. Consequently, satisfactory outcomes were obtained in the application of the polarimetric ALOS PALSAR data of moderate resolution in detecting urban land use and land cover type changes.

  9. Multi-input multi-output frequency-modulated continuous wave synthetic aperture radar system using beat-frequency division waveforms

    NASA Astrophysics Data System (ADS)

    Wang, Jie; Chen, Long-yong; Liang, Xing-dong; Ding, Chi-biao; Hong, Wen; Zhou, Liang-jiang; Dong, Yong-wei; Li, Kun

    2013-07-01

    Attention has been paid to lightweight, cost-effective frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) in recent years. Though FMCW SAR can operate at high altitude, it is still impracticable for wide swath or high Doppler bandwidth remote sensing because of the dramatic losses of range resolution and processing gain. Moreover, the system sampling rate is too high for real-time processing. All these restrictions caused by the bandwidth loss of the dechirp operation can be relieved by expanding the system sweep cycle. However, the broadening of the sweep cycle decreases the system pulse repetition frequency with azimuth ambiguity, which can be suppressed by exploiting the spatial diversity of multi-input multi-output (MIMO) systems. This paper reports a MIMO-FMCW SAR system using beat-frequency division waveforms. There is a small frequency interval and a large overlap (in frequency) between the orthogonal waveforms. As the frequency interval is much smaller than the signal bandwidth, the echoes that come from different transmitters can be separated by bandpass filtering with little intrapulse interference. Consequently, the applications of FMCW SAR systems can be extended for wider swath or higher Doppler bandwidth remote sensing. Theoretical analysis and simulation results illustrate the feasibility of this system.

  10. Synthetic aperture interferometry: error analysis.

    PubMed

    Biswas, Amiya; Coupland, Jeremy

    2010-07-10

    Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt. 42, 701 (2003)]. A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt. 47, 1705 (2008)]. Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process. PMID:20648161

  11. Geometric ortho-rectification and generation of sigma(0) image products from multiple incidence synthetic aperture radar images

    NASA Technical Reports Server (NTRS)

    Curlander, James; Leberl, Franz; Kruse, Fred

    1992-01-01

    The results of the first phase of a cooperative effort in geometric orthorectification and generation of sigma(0) images of multiple incidence SAR images are presented. The geometric accuracy of the final image products is approximately 18 m or 1.5 pixels. A method for registering radar imagery collected from an airborne platform to an existing digital elevation model despite the effects of unmodeled variations in the flight path of the platform is demonstrated. The results indicate the requirements for a more detailed digital elevation model.

  12. Relationships between autofocus methods for SAR and self-survey techniques for SONAR. [Synthetic Aperture Radar (SAR)

    SciTech Connect

    Wahl, D.E.; Jakowatz, C.V. Jr.; Ghiglia, D.C.; Eichel, P.H.

    1991-01-01

    Autofocus methods in SAR and self-survey techniques in SONAR have a common mathematical basis in that they both involve estimation and correction of phase errors introduced by sensor position uncertainties. Time delay estimation and correlation methods have been shown to be effective in solving the self-survey problem for towed SONAR arrays. Since it can be shown that platform motion errors introduce similar time-delay estimation problems in SAR imaging, the question arises as to whether such techniques could be effectively employed for autofocus of SAR imagery. With a simple mathematical model for motion errors in SAR, we will show why such correlation/time-delay techniques are not nearly as effective as established SAR autofocus algorithms such as phase gradient autofocus or sub-aperture based methods. This analysis forms an important bridge between signal processing methodologies for SAR and SONAR. 5 refs., 4 figs.

  13. The dependence of synthetic aperture radar backscatter on forest structure and biomass: Potential application for global carbon models

    SciTech Connect

    Imhoff, M.L.

    1993-01-01

    The NASA airborne P-band (0.438 GHz), L-band (1.25 GHz), and C-band (5.3 GHz) quadpol. SAR system was used to collect data in tropical broadleaf evergreen forests on the Island of Hawaii.l The SAR data were regressed against biomass measurements made in the field and the response curves for the tropical forests were compared to those made for coniferous forests in North America and Europe using the same SAR instrument and imaging angles (40[degrees]-50[degrees]). Results indicated that the response curves for the tropical forests and the coniferous forests were similar and that the radar signals were saturating at relatively low biomass levels. Biomass saturation points were determined at [approx]100 tons/ha for P-band, [approx]40 tons/ha for L-band, and [approx]20 tons/has for C-band (HH, VV, and HV polarization). The possible existence of a universal saturation point for the SAR response to forest biomass distinctly limits the usefulness of P-, L-, and C-band SAR for global biomass mapping. A small percentage of the world's vegetated systems falls below the highest estimated saturation level. Approximately 46% of the world's vegetated surface area containing 82% of the estimated total store of biomass lies above the saturation limit of the current radar systems (>100 tons/ha for P-band). While 54% of the Earth's vegetated surfaces area is below the saturation level for P-band, this class contains only an estimated 18% of total biomass represented by terrestrial vegetation. Theoretical modeling indicated the primary forest canopy structural factor influencing SAR backscatter was the surface area to volume ratio (SA/V) of the branches. This proved true for both broadleaf evergreens and conifers. As a forest stand matures, the form of the phytomass coalesces into fewer larger components and the calculated SA/V declines as biomass increases. As the SA/V declines the backscatter trends to increase since the radar has larger components from which reflections can occur.

  14. System and method for measuring ocean surface currents at locations remote from land masses using synthetic aperture radar

    NASA Technical Reports Server (NTRS)

    Young, Lawrence E. (Inventor)

    1991-01-01

    A system for measuring ocean surface currents from an airborne platform is disclosed. A radar system having two spaced antennas wherein one antenna is driven and return signals from the ocean surface are detected by both antennas is employed to get raw ocean current data which are saved for later processing. There are a pair of global positioning system (GPS) systems including a first antenna carried by the platform at a first location and a second antenna carried by the platform at a second location displaced from the first antenna for determining the position of the antennas from signals from orbiting GPS navigational satellites. Data are also saved for later processing. The saved data are subsequently processed by a ground-based computer system to determine the position, orientation, and velocity of the platform as well as to derive measurements of currents on the ocean surface.

  15. Optimal aperture synthesis radar imaging

    NASA Astrophysics Data System (ADS)

    Hysell, D. L.; Chau, J. L.

    2006-03-01

    Aperture synthesis radar imaging has been used to investigate coherent backscatter from ionospheric plasma irregularities at Jicamarca and elsewhere for several years. Phenomena of interest include equatorial spread F, 150-km echoes, the equatorial electrojet, range-spread meteor trails, and mesospheric echoes. The sought-after images are related to spaced-receiver data mathematically through an integral transform, but direct inversion is generally impractical or suboptimal. We instead turn to statistical inverse theory, endeavoring to utilize fully all available information in the data inversion. The imaging algorithm used at Jicamarca is based on an implementation of the MaxEnt method developed for radio astronomy. Its strategy is to limit the space of candidate images to those that are positive definite, consistent with data to the degree required by experimental confidence limits; smooth (in some sense); and most representative of the class of possible solutions. The algorithm was improved recently by (1) incorporating the antenna radiation pattern in the prior probability and (2) estimating and including the full error covariance matrix in the constraints. The revised algorithm is evaluated using new 28-baseline electrojet data from Jicamarca.

  16. Applications of Radarsat-1 synthetic aperture radar imagery to assess hurricane-related flooding of coastal Louisiana

    USGS Publications Warehouse

    Kiage, L.M.; Walker, N.D.; Balasubramanian, S.; Babin, A.; Barras, J.

    2005-01-01

    The Louisiana coast is subjected to hurricane impacts including flooding of human settlements, river channels and coastal marshes, and salt water intrusion. Information on the extent of flooding is often required quickly for emergency relief, repairs of infrastructure, and production of flood risk maps. This study investigates the feasibility of using Radarsat-1 SAR imagery to detect flooded areas in coastal Louisiana after Hurricane Lili, October 2002. Arithmetic differencing and multi-temporal enhancement techniques were employed to detect flooding and to investigate relationships between backscatter and water level changes. Strong positive correlations (R2=0.7-0.94) were observed between water level and SAR backscatter within marsh areas proximate to Atchafalaya Bay. Although variations in elevation and vegetation type did influence and complicate the radar signature at individual sites, multi-date differences in backscatter largely reflected the patterns of flooding within large marsh areas. Preliminary analyses show that SAR imagery was not useful in mapping urban flooding in New Orleans after Hurricane Katrina's landfall on 29 August 2005. ?? 2005 Taylor & Francis.

  17. Multifocal interferometric synthetic aperture microscopy

    PubMed Central

    Xu, Yang; Chng, Xiong Kai Benjamin; Adie, Steven G.; Boppart, Stephen A.; Scott Carney, P.

    2014-01-01

    There is an inherent trade-off between transverse resolution and depth of field (DOF) in optical coherence tomography (OCT) which becomes a limiting factor for certain applications. Multifocal OCT and interferometric synthetic aperture microscopy (ISAM) each provide a distinct solution to the trade-off through modification to the experiment or via post-processing, respectively. In this paper, we have solved the inverse problem of multifocal OCT and present a general algorithm for combining multiple ISAM datasets. Multifocal ISAM (MISAM) uses a regularized combination of the resampled datasets to bring advantages of both multifocal OCT and ISAM to achieve optimal transverse resolution, extended effective DOF and improved signal-to-noise ratio. We present theory, simulation and experimental results. PMID:24977909

  18. Forest above ground biomass estimation and forest/non-forest classification for Odisha, India, using L-band Synthetic Aperture Radar (SAR) data

    NASA Astrophysics Data System (ADS)

    Suresh, M.; Kiran Chand, T. R.; Fararoda, R.; Jha, C. S.; Dadhwal, V. K.

    2014-11-01

    Tropical forests contribute to approximately 40 % of the total carbon found in terrestrial biomass. In this context, forest/non-forest classification and estimation of forest above ground biomass over tropical regions are very important and relevant in understanding the contribution of tropical forests in global biogeochemical cycles, especially in terms of carbon pools and fluxes. Information on the spatio-temporal biomass distribution acts as a key input to Reducing Emissions from Deforestation and forest Degradation Plus (REDD+) action plans. This necessitates precise and reliable methods to estimate forest biomass and to reduce uncertainties in existing biomass quantification scenarios. The use of backscatter information from a host of allweather capable Synthetic Aperture Radar (SAR) systems during the recent past has demonstrated the potential of SAR data in forest above ground biomass estimation and forest / nonforest classification. In the present study, Advanced Land Observing Satellite (ALOS) / Phased Array L-band Synthetic Aperture Radar (PALSAR) data along with field inventory data have been used in forest above ground biomass estimation and forest / non-forest classification over Odisha state, India. The ALOSPALSAR 50 m spatial resolution orthorectified and radiometrically corrected HH/HV dual polarization data (digital numbers) for the year 2010 were converted to backscattering coefficient images (Schimada et al., 2009). The tree level measurements collected during field inventory (2009-'10) on Girth at Breast Height (GBH at 1.3 m above ground) and height of all individual trees at plot (plot size 0.1 ha) level were converted to biomass density using species specific allometric equations and wood densities. The field inventory based biomass estimations were empirically integrated with ALOS-PALSAR backscatter coefficients to derive spatial forest above ground biomass estimates for the study area. Further, The Support Vector Machines (SVM) based Radial Basis Function classification technique was employed to carry out binary (forest-non forest) classification using ALOSPALSAR HH and HV backscatter coefficient images and field inventory data. The textural Haralick's Grey Level Cooccurrence Matrix (GLCM) texture measures are determined on HV backscatter image for Odisha, for the year 2010. PALSAR HH, HV backscatter coefficient images, their difference (HHHV) and HV backscatter coefficient based eight textural parameters (Mean, Variance, Dissimilarity, Contrast, Angular second moment, Homogeneity, Correlation and Contrast) are used as input parameters for Support Vector Machines (SVM) tool. Ground based inputs for forest / non-forest were taken from field inventory data and high resolution Google maps. Results suggested significant relationship between HV backscatter coefficient and field based biomass (R2 = 0.508, p = 0.55) compared to HH with biomass values ranging from 5 to 365 t/ha. The spatial variability of biomass with reference to different forest types is in good agreement. The forest / nonforest classified map suggested a total forest cover of 50214 km2 with an overall accuracy of 92.54 %. The forest / non-forest information derived from the present study showed a good spatial agreement with the standard forest cover map of Forest Survey of India (FSI) and corresponding published area of 50575 km2. Results are discussed in the paper.

  19. Analysis of lake ice dynamics and morphology on Lake El'gygytgyn, NE Siberia, using synthetic aperture radar (SAR) and Landsat

    NASA Astrophysics Data System (ADS)

    Nolan, Matt; Liston, Glen; Prokein, Peter; Brigham-Grette, Julie; Sharpton, Virgil L.; Huntzinger, Rachel

    2003-01-01

    A time series of more than 450 combined ERS-2, Radarsat-1, and Landsat-7 scenes acquired between 1998 and 2001 was analyzed to develop a fairly complete picture of lake ice dynamics on Lake El'gygytgyn, NE Siberia (67.5°N, 172°E). This 14-km3 lake partially fills a meteorite impact crater formed 3.6 million years ago and is home to a paleoenvironmental coring project. The duration of lake ice cover and the onset of lake ice breakup are important both to interpretations of the archived sediment core record and to future drilling projects that will use the ice as a stable platform. Ice formation, snowmelt, and ice breakup likely occur in late October, mid-May, and early July, respectively. These data were used to validate a one-dimensional energy-balance lake ice model, which can now be used to hindcast paleoclimate based on core proxy information. Synthetic aperture radar (SAR) backscatter from the lake ice also revealed unusual spatial variations in bubble content, which were found to indicate the level of biological productivity in the sediments directly beneath the ice, with the highest productivity located in the shallowest (0-10 m) as well as the deepest (170-175 m) regions of the lake. Seismic data indicates that the backscatter anomaly above the deepest water is collocated with the central peak of the impact crater, 500 m below the surface. Several hypotheses are presented to explain this anomaly. Regardless of cause, the fact that large spatial variations in biological productivity exist in the lake has important implications for selecting the locations of future sediment cores.

  20. Sinking Coastlines: Land Subsidence at Aquaculture Facilities in the Yellow River Delta, China, measured with Differential Synthetic Aperture Radar (D-InSAR)

    NASA Astrophysics Data System (ADS)

    Higgins, S.; Overeem, I.; Tanaka, A.; Syvitski, J. P.

    2013-12-01

    Land subsidence in river deltas is a global problem. It heightens storm surges, salinates groundwater, intensifies river flooding, destabilizes infrastructure and accelerates shoreline retreat. Measurements of delta subsidence typically rely on point measures such as GPS devices, tide gauges or extensometers, but spatial coverage is needed to fully assess risk across river deltas. Differential Interferometric Synthetic Aperture Radar (D-InSAR) is a satellite-based technique that can provide maps of ground deformation with mm to cm-scale vertical resolution. We apply D-InSAR to the coast of the Yellow River Delta in China, which is dominated by aquaculture facilities and has experienced severe coastal erosion in the last twenty years. We extract deformation patterns from dry land adjacent to aquaculture facilities along the coast, allowing the first measurements of subsidence at a non-urban delta shoreline. Results show classic cones-of-depression surrounding aquaculture facilities, likely due to groundwater pumping. Subsidence rates are as high as 250 mm/y at the largest facility on the delta. These rates exceed local and global average sea level rise by nearly two orders of magnitude. If these rates continue, large aquaculture facilities in the area could induce more than a meter of relative sea level rise every five years. Given the global explosion in fish farming in recent years, these results also suggest that similar subsidence and associated relative sea level rise may present a significant hazard for other Asian megadeltas. False-color MODIS image of the Yellow River delta in September 2012. Water appears dark blue, highlighting the abundance of aquaculture facilities along the coast. Green land is primarily agricultural; brown is urban. Red boxes indicate locations of aquaculture facilities examined in this study. Figure from Higgins, S., Overeem, I., Tanaka, A., & Syvitski, J.P.M., (2013), Land Subsidence at Aquaculture Facilities in the Yellow River Delta, Geophysical Research Letters, in press.

  1. Southern San Andreas-San Jacinto fault system slip rates estimated from earthquake cycle models constrained by GPS and interferometric synthetic aperture radar observations

    NASA Astrophysics Data System (ADS)

    Lundgren, Paul; Hetland, Eric A.; Liu, Zhen; Fielding, Eric J.

    2009-02-01

    We use ground geodetic and interferometric synthetic aperture radar satellite observations across the southern San Andreas (SAF)-San Jacinto (SJF) fault systems to constrain their slip rates and the viscosity structure of the lower crust and upper mantle on the basis of periodic earthquake cycle, Maxwell viscoelastic, finite element models. Key questions for this system are the SAF and SJF slip rates, the slip partitioning between the two main branches of the SJF, and the dip of the SAF. The best-fitting models generally have a high-viscosity lower crust (η = 1021 Pa s) overlying a lower-viscosity upper mantle (η = 1019 Pa s). We find considerable trade-offs between the relative time into the current earthquake cycle of the San Jacinto fault and the upper mantle viscosity. With reasonable assumptions for the relative time in the earthquake cycle, the partition of slip is fairly robust at around 24-26 mm/a for the San Jacinto fault system and 16-18 mm/a for the San Andreas fault. Models for two subprofiles across the SAF-SJF systems suggest that slip may transfer from the western (Coyote Creek) branch to the eastern (Clark-Superstition hills) branch of the SJF from NW to SE. Across the entire system our best-fitting model gives slip rates of 2 ± 3, 12 ± 9, 12 ± 9, and 17 ± 3 mm/a for the Elsinore, Coyote Creek, Clark, and San Andreas faults, respectively, where the large uncertainties in the slip rates for the SJF branches reflect the large uncertainty in the slip rate partitioning within the SJF system.

  2. Transmission of information from large groups of sensors using synthetic aperture radar and modulated reradiation, and, Quasi-regular LDPC code design for QAM constellations

    NASA Astrophysics Data System (ADS)

    Vanjari, Srinivas V.

    This thesis consists of two parts. In the first part, we develop a remote data collection system to extract information from a number of passive sensors. Active transmitters on sensors, being inherently energy expensive, pose a bottleneck to long battery life. We propose modulated reradiation of radar illumination by sensor nodes as a means to transmit information. A Synthetic Aperture processing technique is developed to decode the transmitted information and simultaneously obtain a geographic map of the sensor locations. Modulated re-radiation be achieved by switching a load on the sensor antenna. Load modulation consumes negligible power compared to an active transmitter, thus reducing the overall power consumption of the sensor. To eliminate the clutter interference in the imaging process due to the presence of unwanted targets, a nonlinear antenna load is used and the reradiated harmonics are processed. In the second part, we develop an LDPC coded modulation scheme for bandwidthefficient data transmission using QAM modulation. The underlying LDPC code is a rate 1/2 quasi-regular code having a low check degree of 5. The code is designed to offer different levels of protection to each bit position in the modulation symbol. Edges attached to different bit positions are treated differently and constraints are imposed on the check node connections to maximize the reliability of the outgoing messages from the check nodes. With a suitable choice of the constellation labeling and by using iterative demodulation, the code is shown to provide excellent performance on an AWGN channel at reasonably short block lengths.

  3. Integration of optical and synthetic aperture radar (SAR) images to differentiate grassland and alfalfa in Prairie area

    NASA Astrophysics Data System (ADS)

    Hong, Gang; Zhang, Aining; Zhou, Fuqun; Brisco, Brian

    2014-05-01

    Alfalfa presents a huge potential biofuel source in the Prairie Provinces of Canada. However, it remains a challenge to find an ideal single satellite sensor to monitor the regional spatial distribution of alfalfa on an annual basis. The primary interest of this study is to identify alfalfa spatial distribution through effectively differentiating alfalfa from grasslands, given their spectral similarity and same growth calendars. MODIS and RADARSAT-2 ScanSAR narrow mode were selected for regional-level grassland and alfalfa differentiation in the Prairie Provinces, due to the high frequency revisit of MODIS, the weather independence of ScanSAR as well as the large area coverage and the complementary characteristics SAR and optical images. Combining MODIS and ScanSAR in differentiating alfalfa and grassland is very challenging, since there is a large spatial resolution difference between MODIS (250 m) and ScanSAR narrow (50 m). This study investigated an innovative image fusion technique for combining MODIS and ScanSAR and obtaining a synthetic image which has the high spatial details derived from ScanSAR and the colour information from MODIS. The field trip was arranged to collect ground truth to label and validate the classification results. The fusion classification result shows significant accuracy improvement when compared with either ScanSAR or MODIS alone or with other commonly-used data combination methods, such as multiple files composites. This study has shown that the image fusion technique used in this study can combine the structural information from high resolution ScanSAR and colour information from MODIS to significantly improve the classification accuracy between alfalfa and grassland.

  4. Investigation of land subsidence in the Houston-Galveston region of Texas by using the Global Positioning System and interferometric synthetic aperture radar, 1993-2000

    USGS Publications Warehouse

    Bawden, Gerald W.; Johnson, Michaela R.; Kasmarek, Mark C.; Brandt, Justin; Middleton, Clifton S.

    2012-01-01

    Since the early 1900s, groundwater has been the primary source of municipal, industrial, and agricultural water supplies for the Houston-Galveston region, Texas. The region's combination of hydrogeology and nearly century-long use of groundwater has resulted in one of the largest areas of subsidence in the United States; by 1979, as much as 3 meters (m) of subsidence had occurred, and approximately 8,300 square kilometers of land had subsided more than 0.3 m. The U.S. Geological Survey, in cooperation with the Harris-Galveston Subsidence District, used interferometric synthetic aperture radar (InSAR) data obtained for four overlapping scenes from European remote sensing satellites ERS-1 and ERS-2 to analyze land subsidence in the Houston-Galveston region of Texas. The InSAR data were processed into 27 interferograms that delineate and quantify land-subsidence patterns and magnitudes. Contemporaneous data from the Global Positioning System (GPS) were reprocessed by the National Geodetic Survey and analyzed to support, verify, and provide temporal resolution to the InSAR investigation. The interferograms show that the area of historical subsidence in downtown Houston along the Houston Ship Channel has stabilized and that recent subsidence occurs farther west and north of Galveston Bay. Three areas of recent subsidence were delineated along a broad arcuate (bowshaped) feature from Spring, Tex., southwest to Cypress, Tex., and south to Sugar Land, Tex., with subsidence rates ranging from 15 millimeters per year (mm/yr) to greater than 60 mm/yr. Multiyear interferograms near Seabrook, Tex., within the historical subsidence area and nearby Galveston Bay, show several fringes of subsidence (approximately 85 millimeters from January 1996 to December 1997) in the area; however it is difficult to determine the subsidence magnitude near Seabrook because many of the InSAR fringes were truncated or ill-defined. Horizontal and vertical GPS data throughout the area support the InSAR measured subsidence rates and extent. The subsidence rates for a few GPS stations northwest of Houston began to decrease in 2007, which may indicate that subsidence may be decreasing in these areas.

  5. Detection and measurement of land subsidence using interferometric synthetic aperture radar and Global Positioning System, San Bernardino County, Mojave Desert, California

    USGS Publications Warehouse

    Sneed, Michelle; Ikehara, Marti E.; Stork, Sylvia V.; Amelung, Falk; Galloway, Devin L.

    2003-01-01

    Land subsidence associated with ground-water-level declines has been recognized as a potential problem in parts of the Mojave Desert, California. Ground water has been the primary source of domestic, agricultural, and municipal water supplies in the desert since the early 1900s. Pumping of ground water from the Mojave River and Morongo ground-water basins in the southwestern Mojave Desert resulted in water-level declines of more than 30 meters (100 feet) between the 1950s and the 1990s. A Global Positioning System (GPS) survey of a geodetic network was used to determine the location, extent, and magnitude of vertical land-surface changes in Lucerne Valley in the Morongo ground-water basin. The GPS survey was conducted in 1998 to estimate historical elevation changes by comparing GPS-derived elevations with historical elevations (which were available for some of the monuments in the network as early as 1944) and to establish baseline values that can be used for comparisons with future GPS surveys. The GPS measurements indicated that about 600 millimeters (2 feet) [plus or minus 1,500 millimeters (5 feet)] of subsidence occurred at three of the monuments between 1969 and 1998 but that very little to no vertical change in position occurred at seven other monuments in the network. Water levels in the area of subsidence in Lucerne Valley declined about 15 meters (50 feet) during 1970-98. Interferometric synthetic aperture radar (InSAR) methods were used to characterize vertical land-surface changes in the Mojave River and Morongo ground-water basins during various intervals of time between 1992 and 1999. Interferograms, InSAR-generated displacement maps, show that subsidence ranging from 45 to 90 mm (0.15 to 0.3 ft) occurred in four areas of these two ground-water basins--the El Mirage, Lockhart-Harper Lake (dry), Newberry Springs, and Lucerne Valley areas. Some of the InSAR measurements were affected by the earthquakes at Landers and Hector Mine, California, and by atmospheric artifacts. Water-level data were examined for areas undergoing vertical land-surface changes to determine whether the vertical land-surface changes may be related to aquifer-system compaction caused by ground-water-level changes. Temporally relevant water-level data were sparse for some areas, particularly the El Mirage and Lockhart-Harper Lake (dry) areas. Water levels in wells proximate to the subsiding areas generally declined between 1992 and 1999; water levels in some wells proximate to the subsiding areas experienced seasonal periods of declines and recoveries.

  6. 3D surface flow kinematics derived from airborne UAVSAR interferometric synthetic aperture radar to constrain the physical mechanisms controlling landslide motion

    NASA Astrophysics Data System (ADS)

    Delbridge, B. G.; Burgmann, R.; Fielding, E. J.; Hensley, S.; Schulz, W. H.

    2013-12-01

    This project focuses on improving our understanding of the physical mechanisms controlling landslide motion by studying the landslide-wide kinematics of the Slumgullion landslide in southwestern Colorado using interferometric synthetic aperture radar (InSAR) and GPS. The NASA/JPL UAVSAR airborne repeat-pass SAR interferometry system imaged the Slumgullion landslide from 4 look directions on eight flights in 2011 and 2012. Combining the four look directions allows us to extract the full 3-D velocity field of the surface. Observing the full 3-dimensional flow field allows us to extract the full strain tensor (assuming free surface boundary conditions and incompressible flow) since we have both the spatial resolution to take spatial derivates and full deformation information. COSMO-SkyMed(CSK) high-resolution Spotlight data was also acquired during time intervals overlapping with the UAVSAR one-week pairs, with intervals as short as one day. These observations allow for the quantitative testing of the deformation magnitude and estimated formal errors in the UAVSAR derived deformation field. We also test the agreement of the deformation at 20 GPS monitoring sites concurrently acquired by the USGS. We also utilize the temporal resolution of real-time GPS acquired by the UC Berkeley Active Tectonics Group during a temporary deployment from July 22nd - August 2nd. By combining this data with the kinematic data we hope to elucidate the response of the landslide to environmental changes such as rainfall, snowmelt, and atmospheric pressure, and consequently the mechanisms controlling the dynamics of the landslide system. To constrain the longer temporal dynamics, interferograms made from pairs of CSK images acquired in 2010, 2011, 2012 and 2013 reveal the slide deformation on a longer timescale by allowing us to measure meters of motion and see the average rates over year long intervals using pixel offset tracking of the high-resolution SAR amplitude images. The results of this study will also allow us to test the agreement and commensurability of UAVSAR- derived deformation with real-time GPS observations and traditional satellite-based SAR interferometry from the COSMOSkyMed system. We will not only help mitigate the hazards associated with large landslides, but also provide information on the limitations of current geodetic imaging techniques. This unique opportunity to compare several concurrent geodetic observations of the same deformation will provide constraints and recommendations for the design and implementation of future geodetic systems for the monitoring of Earth surface processes.

  7. The potential of flood forecasting using a variable-resolution global Digital Terrain Model and flood extents from Synthetic Aperture Radar images.

    NASA Astrophysics Data System (ADS)

    Mason, David; Garcia-Pintado, Javier; Cloke, Hannah; Dance, Sarah

    2015-08-01

    A basic data requirement of a river flood inundation model is a Digital Terrain Model (DTM) of the reach being studied. The scale at which modeling is required determines the accuracy required of the DTM. For modeling floods in urban areas, a high resolution DTM such as that produced by airborne LiDAR (Light Detection And Ranging) is most useful, and large parts of many developed countries have now been mapped using LiDAR. In remoter areas, it is possible to model flooding on a larger scale using a lower resolution DTM, and in the near future the DTM of choice is likely to be that derived from the TanDEM-X Digital Elevation Model (DEM). A variable-resolution global DTM obtained by combining existing high and low resolution data sets would be useful for modeling flood water dynamics globally, at high resolution wherever possible and at lower resolution over larger rivers in remote areas. A further important data resource used in flood modeling is the flood extent, commonly derived from Synthetic Aperture Radar (SAR) images. Flood extents become more useful if they are intersected with the DTM, when water level observations (WLOs) at the flood boundary can be estimated at various points along the river reach. To illustrate the utility of such a global DTM, two examples of recent research involving WLOs at opposite ends of the spatial scale are discussed. The first requires high resolution spatial data, and involves the assimilation of WLOs from a real sequence of high resolution SAR images into a flood model to update the model state with observations over time, and to estimate river discharge and model parameters, including river bathymetry and friction. The results indicate the feasibility of such an Earth Observation-based flood forecasting system. The second example is at a larger scale, and uses SAR-derived WLOs to improve the lower-resolution TanDEM-X DEM in the area covered by the flood extents. The resulting reduction in random height error is significant.

  8. Analysis of the fractal dimension of volcano geomorphology through Synthetic Aperture Radar (SAR) amplitude images acquired in C and X band.

    NASA Astrophysics Data System (ADS)

    Pepe, S.; Di Martino, G.; Iodice, A.; Manzo, M.; Pepe, A.; Riccio, D.; Ruello, G.; Sansosti, E.; Tizzani, P.; Zinno, I.

    2012-04-01

    In the last two decades several aspects relevant to volcanic activity have been analyzed in terms of fractal parameters that effectively describe natural objects geometry. More specifically, these researches have been aimed at the identification of (1) the power laws that governed the magma fragmentation processes, (2) the energy of explosive eruptions, and (3) the distribution of the associated earthquakes. In this paper, the study of volcano morphology via satellite images is dealt with; in particular, we use the complete forward model developed by some of the authors (Di Martino et al., 2012) that links the stochastic characterization of amplitude Synthetic Aperture Radar (SAR) images to the fractal dimension of the imaged surfaces, modelled via fractional Brownian motion (fBm) processes. Based on the inversion of such a model, a SAR image post-processing has been implemented (Di Martino et al., 2010), that allows retrieving the fractal dimension of the observed surfaces, dictating the distribution of the roughness over different spatial scales. The fractal dimension of volcanic structures has been related to the specific nature of materials and to the effects of active geodynamic processes. Hence, the possibility to estimate the fractal dimension from a single amplitude-only SAR image is of fundamental importance for the characterization of volcano structures and, moreover, can be very helpful for monitoring and crisis management activities in case of eruptions and other similar natural hazards. The implemented SAR image processing performs the extraction of the point-by-point fractal dimension of the scene observed by the sensor, providing - as an output product - the map of the fractal dimension of the area of interest. In this work, such an analysis is performed on Cosmo-SkyMed, ERS-1/2 and ENVISAT images relevant to active stratovolcanoes in different geodynamic contexts, such as Mt. Somma-Vesuvio, Mt. Etna, Vulcano and Stromboli in Southern Italy, Shinmoe in Japan, Merapi in Indonesia. Preliminary results reveal that the fractal dimension of natural areas, being related only to the roughness of the observed surface, is very stable as the radar illumination geometry, the resolution and the wavelength change, thus holding a very unique property in SAR data inversion. Such a behavior is not verified in case of non-natural objects. As a matter of fact, when the fractal estimation is performed in the presence of either man-made objects or SAR image features depending on geometrical distortions due to the SAR system acquisition (i.e. layover, shadowing), fractal dimension (D) values outside the range of fractality of natural surfaces (2 < D < 3) are retrieved. These non-fractal characteristics show to be heavily dependent on sensor acquisition parameters (e.g. view angle, resolution). In this work, the behaviour of the maps generated starting from the C- and X- band SAR data, relevant to all the considered volcanoes, is analyzed: the distribution of the obtained fractal dimension values is investigated on different zones of the maps. In particular, it is verified that the fore-slope and back-slope areas of the image share a very similar fractal dimension distribution that is placed around the mean value of D=2.3. We conclude that, in this context, the fractal dimension could be considered as a signature of the identification of the volcano growth as a natural process. The COSMO-SkyMed data used in this study have been processed at IREA-CNR within the SAR4Volcanoes project under Italian Space Agency agreement n. I/034/11/0.

  9. Determination of Classification Accuracy for Land Use/cover Types Using Landsat-Tm Spot-Mss and Multipolarized and Multi-Channel Synthetic Aperture Radar

    NASA Astrophysics Data System (ADS)

    Dondurur, Mehmet

    The primary objective of this study was to determine the degree to which modern SAR systems can be used to obtain information about the Earth's vegetative resources. Information obtainable from microwave synthetic aperture radar (SAR) data was compared with that obtainable from LANDSAT-TM and SPOT data. Three hypotheses were tested: (a) Classification of land cover/use from SAR data can be accomplished on a pixel-by-pixel basis with the same overall accuracy as from LANDSAT-TM and SPOT data. (b) Classification accuracy for individual land cover/use classes will differ between sensors. (c) Combining information derived from optical and SAR data into an integrated monitoring system will improve overall and individual land cover/use class accuracies. The study was conducted with three data sets for the Sleeping Bear Dunes test site in the northwestern part of Michigan's lower peninsula, including an October 1982 LANDSAT-TM scene, a June 1989 SPOT scene and C-, L- and P-Band radar data from the Jet Propulsion Laboratory AIRSAR. Reference data were derived from the Michigan Resource Information System (MIRIS) and available color infrared aerial photos. Classification and rectification of data sets were done using ERDAS Image Processing Programs. Classification algorithms included Maximum Likelihood, Mahalanobis Distance, Minimum Spectral Distance, ISODATA, Parallelepiped, and Sequential Cluster Analysis. Classified images were rectified as necessary so that all were at the same scale and oriented north-up. Results were analyzed with contingency tables and percent correctly classified (PCC) and Cohen's Kappa (CK) as accuracy indices using CSLANT and ImagePro programs developed for this study. Accuracy analyses were based upon a 1.4 by 6.5 km area with its long axis east-west. Reference data for this subscene total 55,770 15 by 15 m pixels with sixteen cover types, including seven level III forest classes, three level III urban classes, two level II range classes, two water classes, one wetland class and one agriculture class. An initial analysis was made without correcting the 1978 MIRIS reference data to the different dates of the TM, SPOT and SAR data sets. In this analysis, highest overall classification accuracy (PCC) was 87% with the TM data set, with both SPOT and C-Band SAR at 85%, a difference statistically significant at the 0.05 level. When the reference data were corrected for land cover change between 1978 and 1991, classification accuracy with the C-Band SAR data increased to 87%. Classification accuracy differed from sensor to sensor for individual land cover classes, Combining sensors into hypothetical multi-sensor systems resulted in higher accuracies than for any single sensor. Combining LANDSAT -TM and C-Band SAR yielded an overall classification accuracy (PCC) of 92%. The results of this study indicate that C-Band SAR data provide an acceptable substitute for LANDSAT-TM or SPOT data when land cover information is desired of areas where cloud cover obscures the terrain. Even better results can be obtained by integrating TM and C-Band SAR data into a multi-sensor system.

  10. Inverse-synthetic-aperture imaging of trees over a ground plane

    SciTech Connect

    Zittel, D.H.; Brock, B.C.; Littlejohn, J.H.; Patitz, W.E.

    1995-11-01

    Recent data collections with the Sandia VHF-UHF synthetic-aperture radar have yielded surprising results; trees appear brighter in the images than expected! In an effort to understand this phenomenon, various small trees have been measured on the Sandia folded compact range with the inverse-synthetic-aperture imaging system. A compilation of these measurements is contained in this report.

  11. Synthetic aperture laser optical feedback imaging using galvanometric scanning.

    PubMed

    Witomski, Arnaud; Lacot, Eric; Hugon, Olivier; Jacquin, Olivier

    2006-10-15

    We describe a new one-dimensional synthetic aperture imaging laser radar (ladar) using the resonant sensitivity of a microchip laser to frequency-shifted optical feedback and galvanometric scanning of the target under investigation. In our experiment, the laser is both the source and the detector, providing optical amplification with self-aligned heterodyne detection. By using galvanometric scanning, we achieve an along-track spatial resolution better than the diffraction limit. PMID:17001390

  12. A synthetic aperture acoustic prototype system

    NASA Astrophysics Data System (ADS)

    Luke, Robert H.; Bishop, Steven S.; Chan, Aaron M.; Gugino, Peter M.; Donzelli, Thomas P.; Soumekh, Mehrdad

    2015-05-01

    A novel quasi-monostatic system operating in a side-scan synthetic aperture acoustic (SAA) imaging mode is presented. This research project's objectives are to explore the military utility of outdoor continuous sound imaging of roadside foliage and target detection. The acoustic imaging method has several military relevant advantages such as being immune to RF jamming, superior spatial resolution as compared to 0.8-2.4 GHz ground penetrating radar (GPR), capable of standoff side and forward-looking scanning, and relatively low cost, weight and size when compared to GPR technologies. The prototype system's broadband 2-17 kHz LFM chirp transceiver is mounted on a manned all-terrain vehicle. Targets are positioned within the acoustic main beam at slant ranges of two to seven meters and on surfaces such as dirt, grass, gravel and weathered asphalt and with an intervening metallic chain link fence. Acoustic image reconstructions and signature plots result in means for literal interpretation and quantifiable analyses.

  13. Detection and Measurement of Land Subsidence Using Global Positioning System and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 1998-2000

    USGS Publications Warehouse

    Sneed, Michelle; Stork, Sylvia V.; Ikehara, Marti E.

    2002-01-01

    Land subsidence associated with ground-water-level declines has been recognized as a potential problem in Coachella Valley, California. Since the early 1920s, ground water has been a major source of agricultural, municipal, and domestic supply in the valley. Pumping of ground water resulted in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the lower Coachella Valley began, resulting in a reduction in ground-water pumping and a recovery of water levels during the 1950s through the 1970s. Since the late 1970s, demand for water in the valley has exceeded deliveries of imported surface water, resulting in increased pumping and associated ground-water-level declines and, consequently, an increase in the potential for land subsidence caused by aquifer-system compaction. The location, extent, and magnitude of the vertical land-surface changes in Coachella Valley between 1998 and 2000 were determined using Global Positioning System (GPS) and interferometric synthetic aperture radar (InSAR) methods. GPS measurements made at 15 geodetic monuments in the lower Coachella Valley indicate that -34 to +60 millimeters ? 45 millimeters (-0.11 to +0.20 foot ? 0.15 foot) of vertical change in the land surface occurred during the 2-year period. Changes at three of the monuments exceeded the maximum uncertainty of ? 45 millimeters (? 0.15 foot) at the 95-percent confidence level, which indicates that small amounts of uplift occurred at these monuments between October 1998 and August 2000. Water-level measurements made at wells near the three uplifted monuments during this 2-year period indicate that the water levels fluctuate seasonally; water-level measurements made at these wells in September 1998 and September 2000 indicate that the water levels rose slightly near two monuments and declined slightly near the third. The relation between the seasonally fluctuating, but fairly stable, water levels between September 1998 and September 2000 and the slight uplift at the monuments may indicate that the water levels are fluctuating in the elastic range of stress and that the preconsolidation stress of the aquifer system was not exceeded during the 2-year period. Results of the InSAR measurements made between June 17, 1998, and October 4, 2000, indicate that land subsidence, ranging from about 40 to 80 millimeters (0.13 to 0.26 foot), occurred in three areas of the Coachella Valley; near Palm Desert, Indian Wells, and La Quinta. Measurements made between June 17, 1998, and June 2, 1999, indicate that about 15 millimeters (0.05 foot) occurred southeast of Lake Cahuilla. All the subsiding areas coincide with or are near areas where ground-water levels declined between 1998 and 2000; some water levels in 2000 were at the lowest levels in their recorded histories. The coincident areas of subsidence and declining water levels suggest that aquifer-system compaction may be causing subsidence. If the stresses imposed by the historically lowest water levels exceeded the preconsolidation stress, the aquifer-system compaction and associated land subsidence may be permanent. Although the localized character of the subsidence signals look typical of the type of subsidence characteristically caused by localized pumping, the subsidence also may be related to tectonic activity in the valley.

  14. Natural and Unnatural Oil Layers on the Surface of the Gulf of Mexico Detected and Quantified in Synthetic Aperture RADAR Images with Texture Classifying Neural Network Algorithms

    NASA Astrophysics Data System (ADS)

    MacDonald, I. R.; Garcia-Pineda, O. G.; Morey, S. L.; Huffer, F.

    2011-12-01

    Effervescent hydrocarbons rise naturally from hydrocarbon seeps in the Gulf of Mexico and reach the ocean surface. This oil forms thin (~0.1 μm) layers that enhance specular reflectivity and have been widely used to quantify the abundance and distribution of natural seeps using synthetic aperture radar (SAR). An analogous process occurred at a vastly greater scale for oil and gas discharged from BP's Macondo well blowout. SAR data allow direct comparison of the areas of the ocean surface covered by oil from natural sources and the discharge. We used a texture classifying neural network algorithm to quantify the areas of naturally occurring oil-covered water in 176 SAR image collections from the Gulf of Mexico obtained between May 1997 and November 2007, prior to the blowout. Separately we also analyzed 36 SAR images collections obtained between 26 April and 30 July, 2010 while the discharged oil was visible in the Gulf of Mexico. For the naturally occurring oil, we removed pollution events and transient oceanographic effects by including only the reflectance anomalies that that recurred in the same locality over multiple images. We measured the area of oil layers in a grid of 10x10 km cells covering the entire Gulf of Mexico. Floating oil layers were observed in only a fraction of the total Gulf area amounting to 1.22x10^5 km^2. In a bootstrap sample of 2000 replications, the combined average area of these layers was 7.80x10^2 km^2 (sd 86.03). For a regional comparison, we divided the Gulf of Mexico into four quadrates along 90° W longitude, and 25