Note: This page contains sample records for the topic synthetic aperture radar from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Doppler synthetic aperture radar imaging  

NASA Astrophysics Data System (ADS)

We consider synthetic aperture radar system using ultra-narrowband continuous waveforms, which we refer to as Doppler Synthetic Aperture Radar (DSAR). We present a novel image formation method for bi-static DSAR. Our method first correlates the received signal with a scaled or frequency-shifted version of the transmitted signal over a finite time window, and then uses microlocal analysis to reconstruct the scene by a filtered-backprojection of the correlated signals. Our approach can be used under non-ideal imaging scenarios such as arbitrary flight trajectories and non-flat topography. Furthermore, it is an analytic reconstruction technique which can be made computationally efficient. We present numerical experiments to demonstrate the performance of the proposed method.

Wang, Ling; Yazici, Birsen

2011-05-01

2

Imaging synthetic aperture radar  

DOEpatents

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.

Burns, Bryan L. (Tijeras, NM); Cordaro, J. Thomas (Albuquerque, NM)

1997-01-01

3

Differential Optical Synthetic Aperture Radar  

DOEpatents

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.

Stappaerts, Eddy A. (San Ramon, CA)

2005-04-12

4

Processing for spaceborne synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

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.

Lybanon, M.

1973-01-01

5

Analytic inversion in synthetic aperture radar.  

PubMed Central

A method of processing synthetic aperture radar signals that avoids some of the approximations currently in use that appear to be responsible for severe phase distortions is described. As a practical matter, this method requires N3 numerical operations, as opposed to the N2 ln N currently the case, but N3 is now easily managed, for N in the range of interest.

Rothaus, O S

1994-01-01

6

Synthetic Aperture Radar (SAR) Processing Application  

Microsoft Academic Search

Scietice Applications Iiiteriiatioiial corporation (SAIC) has deveilopcd a software application for processing raw synthetic aperture radar (SAK) phase liistories. Tlic software allows efficicnt workstation processitig of satellite and aircraft data. The processor was origiiially ititelided as an aiialysis tool for testing SAR processing algorithms atid for iinproviiig image quality . These iiiiages have occaiiograpliic applications such as wave or ship

Ellen Brown; John McNeil; Seth Phillips

1992-01-01

7

Use of Synthetic Aperture Radar in Cold Climate Flood Response  

Microsoft Academic Search

The purpose of this study was to investigate the usefulness of Synthetic Aperture Radar (SAR) satellite images during a cold climate disaster response event. There were 15 European Space Agency (ESA) Advanced Synthetic Aperture Radar ASAR scenes, five Japan Aerospace Exploration Agency (JAXA) Phased Array type L-band Synthetic Aperture Radar (PALSAR) scenes, one RADARSAT2 scene, and numerous optical sensor data.

L. D. Yarbrough

2009-01-01

8

Ice sheet studies using synthetic aperture radar  

NASA Technical Reports Server (NTRS)

The objective was to demonstrate the utility of synthetic aperture radar in ice sheet studies. The major advantage of SAR imagery over visible imagery is the all-weather capability of radar and the ability to specify look angle. Available digital SAR imagery over ice sheets was collected and examined both qualitatively and quantitatively using corroborative data, such as LANDSAT imagery, to confirm feature identification and interpretations. A simple scattering model will be developed to assess the relative importance of surface topography, composition, and subsurface layering to the intensity of radar backscatter. Recommendations of system parameters will be made for optimal SAR operation over ice sheets.

Bindschadler, R.

1988-01-01

9

Analysis of synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

Some problems faced in applications of radar measurements in hydrology are: (1) adequate calibration of the radar systems and direct digital data will be required in order that repeatable data can be acquired for hydrologic applications; (2) quantitative hydrologic research on a large scale will be prohibitive with aircraft mounted synthetic aperture radar systems due to the system geometry; (3) spacecraft platforms appear to be the best platforms for radar systems when conducting research over watersheds larger than a few square kilometers; (4) experimental radar systems should be designed to avoid use of radomes; and (5) cross polarized X and L band data seem to discriminate between good and poor hydrologic cover better than like polarized data.

Blanchard, B. J.

1977-01-01

10

Wind energy mapping from synthetic aperture radar  

Microsoft Academic Search

Satellite based synthetic aperture radar (SAR) measurements from, e.g. ERS-1\\/ERS-2 can be used for wind energy mapping in coastal regions for wind mill siting. The SAR has clear advantages for high spatial resolution wind field mapping since it is independent of daylight and clouds. The spatial resolution of 30 m is sufficient as is the 100 km wide and several

Ola M. Johannessen; Heidi Espedal; E. Bjorgo

1999-01-01

11

Research and development on synthetic aperture radar  

Microsoft Academic Search

Results to date are summarized from 6 yr of NASDA R&D on a synthetic aperture radar (SAR) to be flown on the ERS-1 satellite in 1990. The system is to collect better imagery, i.e., a scanning swath width of 75 km and a resolution of 25 km from an orbit of 570 km, than did SEASAT. Design constraints on the

Yasuyuki Itoh; Yasumasa Hisada

1986-01-01

12

Performance limits for Synthetic Aperture Radar.  

SciTech Connect

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''.

Doerry, Armin Walter

2006-02-01

13

Topographical Mapping With Synthetic-Aperture Radar  

NASA Technical Reports Server (NTRS)

Interferometric side-looking synthetic-aperture radar shows promise for high-resolution topographical mapping of terrain. Airplane carries two radar antennas. Radar signal transmitted by right antenna, reflected from ground received by both antennas. Amplitudes and phases of received signals recorded and processed separately to yield two 10-m-resolution amplitude-and-phase images of illuminated terrain. Two images mathematically combined point by point to obtain signal image containing interference fringes: phase at each location of image is difference between phases in two signals and amplitude at each location is project of amplitudes of two signals. Theoretically, technique has potential to attain a root-mean-square (rms) altitude error as small as 2 m.

Zebker, Howard A.; Goldstein, Richard M.

1988-01-01

14

Aperture weighting technique for video synthetic aperture radar  

NASA Astrophysics Data System (ADS)

We present a technique for aperture weighting for use in video synthetic aperture radar (SAR). In video SAR the aperture required to achieve the desired cross range resolution typically exceeds the frame rate period. As a result, there can be a significant overlap in the collected phase history used to form consecutive images in the video. Video SAR algorithms seek to exploit this overlap to avoid unnecessary duplication of processing. When no aperture weighting or windowing is used one can simply form oversampled SAR images from the non-overlapping sub-apertures using coherent back projection (or other similar techniques). The resulting sub-aperture images may be coherently summed to produce a full resolution image. A simple approach to windowing for sidelobe control is to weight the sub-apertures during summation of the images. Our approach involves producing two or more weighted images for each sub-aperture which can be linearly combined to approximate any desired aperture weighting. In this method we achieve nearly the same sidelobe control as weighting the phase history data and forming a new image for each frame without losing the computation savings of the sub-aperture image combining approach.

Hawley, Robert W.; Garber, Wendy L.

2011-05-01

15

Soviet oceanographic synthetic aperture radar (SAR) research  

SciTech Connect

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.

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

1991-01-01

16

Lossless compression of synthetic aperture radar images  

SciTech Connect

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.

Ives, R.W. [Sandia National Labs., Albuquerque, NM (United States); Magotra, N.; Mandyam, G.D. [New Mexico Univ., Albuquerque, NM (United States). Dept. of Electrical and Computer Engineering

1996-02-01

17

Digital filters for synthetic aperture radar  

NASA Astrophysics Data System (ADS)

An organized approach is discussed for designing a set of optimal digital filters that can accommodate a wide range of synthetic-aperture radar (SAR) geometries. The basic SAR signal processing functions are reviewed since they are the basis for the filter design problems. Special digital filter optimality criteria are described that are tailored to the SAR environment. The results from recent filter design publications related to these critria are summarized and examples are included to demonstrate the effectiveness of this approach to designing filters for SAR processors.

Adams, J. W.; Medlin, G. W.; Bayma, R. W.

18

Synthetic aperture radar image simulation system  

NASA Astrophysics Data System (ADS)

An intelligent Synthetic Aperture Radar simulation system can be used to optimize the design of SAR system parameters and select optimum SAR data acquisition mode. Previous research mainly focused on simulating geometric characteristics of SAR image, lacking of radiometric consideration in flat areas because of the complexity of the problem. The popular geometric model of Range Doppler Equations cannot be applied to SAR sensor pre-launched as it relies on so many parameters contained in the original SAR data. In this paper we develop a new simulation system based on simplified geometric model and statistical radar scattering model for different thematic contents. It can generate simulated SAR image product at different bands, polarizations, incidence angles and resolutions, according to user's need. As an experiment, a simulation example of ENVISAT ASAR is compared with the real data collected, to demonstrate the utility and correctness of the system.

Xing, Qiang; Li, Zhen; Chen, Quan

2009-09-01

19

Synthetic aperture radar processing with tiered subapertures  

SciTech Connect

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.

Doerry, A.W. [Sandia National Labs., Albuquerque, NM (United States). Synthetic Aperture Radar Dept.

1994-06-01

20

Weighting in digital synthetic aperture radar processing  

NASA Technical Reports Server (NTRS)

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.

Dicenzo, A.

1979-01-01

21

Multi-static synthetic aperture radar and inverse scattering  

Microsoft Academic Search

Abstract In this paper synthetic aperture radar is analyzed from an inverse scattering perspective. It is shown that the classical point scattering model can be generalized to a dipole scattering model. The dipole scattering model reduces to the point scattering model for small aperture angles. For large aperture angles or multiple illumination apertures the dipole model gives an anisotropic reflectivity

Mats Gustafsson

2003-01-01

22

Multistatic synthetic aperture radar image formation.  

PubMed

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

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

2010-05-01

23

Lincoln Laboratory millimeter-wave synthetic aperture radar imaging system  

Microsoft Academic Search

The Lincoln Laboratory millimeter-wave synthetic aperture radar (SAR) imaging system is part of a DARPA-funded program that was established at Lincoln Laboratory to investigate the detection and classification of stationary targets using ultra-high resolution, fully polarimetric SAR and real aperture radar (RAR) data. The system consists of an airborne radar that operates at 33.56 GHz. The raw radar data are

John C. Henry; Thomas J. Murphy; Kathleen M. Carusone

1992-01-01

24

Real-time beamforming synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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.

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

2006-10-01

25

Metrics for Emitter Selection for Multistatic Synthetic Aperture Radar.  

National Technical Information Service (NTIS)

A bistatic implementation of synthetic aperture radar (SAR) to form images of the ground from an aircraft makes use of separate emitters and receivers. When not using cooperative emitters, ground based communications systems can provide illumination. One ...

S. R. Stevens

2013-01-01

26

Synthetic aperture radar signal processing: Trends and technologies  

NASA Technical Reports Server (NTRS)

An overview of synthetic aperture radar (SAR) technology is presented in vugraph form. The following topics are covered: an SAR ground data system; SAR signal processing algorithms; SAR correlator architectures; and current and future trends.

Curlander, John C.

1993-01-01

27

Gabor Segmentation of High Resolution Synthetic Aperture Radar Imagery.  

National Technical Information Service (NTIS)

This thesis investigates the use of Gabor filters and a radial basis function (RBF) network for segmentation of high resolution (1 foot by 1 foot) synthetic aperture radar (SAR) imagery. Processing involved correlation between the SAR imagery and Gabor fu...

M. A. Hazlett

1991-01-01

28

Ambiguity Of Doppler Centroid In Synthetic-Aperture Radar  

NASA Technical Reports Server (NTRS)

Paper discusses performances of two algorithms for resolution of ambiguity in estimated Doppler centroid frequency of echoes in synthetic-aperture radar. One based on range-cross-correlation technique, other based on multiple-pulse-repetition-frequency technique.

Chang, Chi-Yung; Curlander, John C.

1991-01-01

29

Feature-enhanced synthetic aperture radar imaging  

NASA Astrophysics Data System (ADS)

Remotely sensed images have already attained an important role in a wide spectrum of tasks ranging from weather forecasting to battlefield reconnaissance. One of the most promising remote sensing technologies is the imaging radar, known as synthetic aperture radar (SAR). SAR overcomes the nighttime limitations of optical cameras, and the cloud-cover limitations of both optical and infrared imagers. In current systems, techniques such as the polar format algorithm are used to form images from the collected SAR data. These images are then interpreted by human observers. However, the anticipated high data rates and the time critical nature of emerging SAR tasks motivate the use of automated processing or decision-making techniques in information extraction from the reconstructed images. The success of such automated decision-making (e.g. object recognition) depends on how well SAR images exhibit certain features of the underlying scene. Unfortunately, current SAR image formation techniques have no explicit means to highlight features useful for automatic interpretation. Furthermore, these techniques are usually not robust to reduced quality or quantity of data. We have developed a mathematical foundation and associated algorithms for feature-enhanced SAR imaging to address such challenges. Our framework is based on a regularized reconstruction of the scattering field which combines a tomographic model of the SAR observation process with prior information regarding the nature of the features of interest. We demonstrate the inclusion of prior information through a variety of non-quadratic potential functions. Efficient and robust numerical solution of the optimization problems posed in our framework is achieved through novel extensions of half-quadratic regularization methods to the complex-valued SAR problem. We have established a methodology for quantitative evaluation of a SAR image formation technique based on recognition-oriented features. Through qualitative and quantitative analyses on large sets of real and synthetic SAR images, we have demonstrated the benefits provided by feature-enhanced imaging. These benefits include increased resolution, ease of region segmentation, sidelobe reduction, and speckle suppression, which are important attributes for automated decision-making. Furthermore, we have demonstrated the potential of feature-enhanced SAR imaging to improve automated decision-making performance, through classification experiments on automatic target recognition (ATR) systems.

Cetin, Mujdat

30

The SIR-C\\/X-SAR Synthetic Aperture Radar system  

Microsoft Academic Search

The Spaceborne Imaging Radar-C\\/X-Band Synthetic Aperture Radar (SIR-C\\/X-SAR) was a joint United States\\/German\\/Italian space agency imaging radar system successfully flown aboard the shuttle Endeavor in April 1994 and again in September\\/October 1994. The multifaceted SIR-C\\/X-SAR represents a major technological step forward in radar remote sensing and is the first spaceborne multifrequency, polarimetric SAR. The United States developed SIR-C operated at

R. L. Jordan; B. L. Huneycutt; M. Werner

1995-01-01

31

Estimating Doppler Shifts for Synthetic-Aperture Radar  

NASA Technical Reports Server (NTRS)

Quality of synthetic-aperture-radar (SAR) imagery enhanced by pair of signal-processing techniques that compensate for relative motion between target and vehicle. Combining vehicle trajectory data with radar-parameter and raw image data, techniques generate Doppler estimates for use in constructing fully processed images.

Curlander, J. C.

1985-01-01

32

New formulation for interferometric synthetic aperture radar for terrain mapping  

Microsoft Academic Search

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

Charles V. Jakowatz; Daniel E. Wahl; Paul H. Eichel; Paul A. Thompson

1994-01-01

33

The Earth Observing System Synthetic Aperture Radar (EOS SAR) mission  

NASA Technical Reports Server (NTRS)

The EOS SAR mission under consideration as one element of the mission to planet earth, which will provide a long duration radar observing system with multipolarization and multifrequency capability, is presented. The payload consists of three synthetic aperture radar systems; a C-band radar with dual polarization, an L-band radar with quadruple polarization, and an X-band radar with dual polarization. Each radar system will be of the phased-array type, will have variable resolutions and swath widths and will be capable of steering the beam electronically in elevation.

Wellman, John B.; Sander, Michael J.; Suggs, Eric E.; Way, Jobea

1991-01-01

34

Seasat-A Synthetic Aperture Radar - Radar system implementation  

NASA Technical Reports Server (NTRS)

The Synthetic Aperture Radar (SAR) onboard the Seasat-A satellite will conduct a number of experiments involving deep ocean waves, coastal wave patterns, polar ice and land forms. The SAR will have a 25 m by 25 m resolution over a swath of 100 km width centered about 300 km to the right of the spacecraft track. The SAR's high data rate limits operations to times when Seasat-A is in view of a few ground stations with special SAR receiving equipment. However, the SAR will collect much useful data about deep ocean and coastal waves in the Atlantic and Pacific Oceans; about ice in the Northwest Atlantic, in the Great Lakes and off the coast of Alaska; and about land over much of the United States and Canada.

Thompson, T. W.; Laderman, A.

1976-01-01

35

Digital Beamforming Synthetic Aperture Radar (DBSAR) Polarimetric Upgrade  

NASA Technical Reports Server (NTRS)

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.

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

2011-01-01

36

A SEASAT-A synthetic aperture imaging radar system  

NASA Technical Reports Server (NTRS)

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.

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

1975-01-01

37

Synthetic aperture radar system design for random field classification  

NASA Technical Reports Server (NTRS)

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.

Harger, R. O.

1973-01-01

38

Synthetic aperture radar imaging with motion estimation and autofocus  

NASA Astrophysics Data System (ADS)

We introduce from first principles a synthetic aperture radar (SAR) imaging and target motion estimation method that is combined with compensation for radar platform trajectory perturbations. The main steps of the method are (a) segmentation of the data into properly calibrated small apertures, (b) motion or platform trajectory perturbation estimation using the Wigner transform and the ambiguity function of the data in a complementary way and (c) combination of small aperture estimates and construction of high-resolution images over wide apertures. The analysis provides quantitative criteria for implementing the aperture segmentation and the parameter estimation process. X-band persistent surveillance SAR is a specific application that is covered by our analysis. Detailed numerical simulations illustrate the robust applicability of the theory and validate the theoretical resolution analysis.

Borcea, L.; Callaghan, T.; Papanicolaou, G.

2012-04-01

39

Model-based ATR using synthetic aperture radar  

Microsoft Academic Search

The Moving and Stationary Target Acquisition and Recognition (MSTAR) program was initiated by the USA Defense Advanced Research Project Agency (DARPA) and the USA Air Force Research Laboratory (AFRL) in the summer of 1995. The goal of this project was to advance the state of automatic target recognition (ATR) using synthetic aperture radar (SAR) imagery by developing the technology of

R. Hummel

2000-01-01

40

Target discrimination in synthetic aperture radar using artificial neural networks  

Microsoft Academic Search

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

José Carlos Príncipe; Munchurl Kim; John W. Fisher III

1998-01-01

41

Fourier domain interpolation techniques for synthetic aperture radar  

Microsoft Academic Search

Spotlight-mode synthetic aperture radar (SAR) produces complex Fourier data points on a polar grid which is offset from dc in the frequency domain. To produce an image in the spatial domain, it is necessary to invert this sampled Fourier data prior to extracting magnitude information. However, the polar format of the data makes this difficult, since there is no known

B. C. Mather

1986-01-01

42

Matrix pencil method for inverse synthetic aperture radar imaging  

Microsoft Academic Search

A study of a new high-resolution method called the matrix pencil method for inverse synthetic aperture radar (ISAR) imaging is presented. Simulation comparison of the matrix pencil method and the fast Fourier transform (FFT) method demonstrates the superiority of the matrix pencil method. The matrix pencil method is tested on a real data set and it is found to be

F. A. Baqai; Y. Hua

1992-01-01

43

Space shuttle synthetic aperture radar. [using real time  

NASA Technical Reports Server (NTRS)

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.

1975-01-01

44

Alaska collection SAR (Synthetic Aperture Radar) data summary  

Microsoft Academic Search

Four synthetic aperture radar (SAR) data collection flights were made over Alaska and the surrounding waters in March of 1988, to obtain SAR images of sea ice and forested areas. The P-3 SAR, that operates at C-, L-, and X-bands, was used. 85 passes were collected over four days. The flights produced imagery of use to oceanographic, glaciological, geological, and

D. H. Gineris; R. A. Shuchman; J. D. Lyden; A. S. Milman; E. S. Kasischke

1989-01-01

45

Modeling and Simulation of Synthetic Aperture Radars in Matlab.  

National Technical Information Service (NTIS)

The goal of this research is to produce a synthetic aperture radar (SAR) simulation in MATLAB that will provide a framework to investigate the effects of signal type and emission parameters on the resolution and accuracy of the simulated image. A total of...

B. J. Fason

2013-01-01

46

Synthetic aperture radar automatic target recognition based on curvelet transform  

Microsoft Academic Search

A novel synthetic aperture radar (SAR) automatic target recognition (ATR) approach based on Curvelet Transform is proposed. However, the existing approaches can not extract the more effective feature. In this paper, our method is concentrated on a new effective representation of the moving and stationary target acquisition and recognition (MSTAR) database to obtain a more accurate target region and reduce

Shuang Wang; Zhuo Liu; Licheng Jiao; Jun He

2009-01-01

47

Nonlinear Theory of Synthetic Aperture Radar Sea Wave Imaging.  

National Technical Information Service (NTIS)

The Synthetic Aperture Radar (SAR) sea wave imaging mechanism is shown to be nonlinear for any sea wave directions except for the nearly radial one. The SAR image spectrum for azimuthally traveling waves is found with the speckle noise taken into account.

M. B. Kanevsky

1991-01-01

48

Eddy detection using RADARSAT-1 synthetic aperture radar  

Microsoft Academic Search

Two projects undertaken by the National Oceanic and Atmospheric Administration (NOAA) National Environmental Satellite, Data, and Information Service (NESDIS) have shown success in using spaceborne synthetic aperture radar (SAR) to identify oceanic eddies and current boundaries. In addition to detecting the frontal area and change in slick patterns, the SAR imagery may also pick up a change in the low-level

Karen S. Friedman; Xiaofeng Li; William G. Pichel; Pablo Clemente-Colón; Nan Walker; Tim Veenstra

2004-01-01

49

Synthetic aperture radar interferometry of Okmok volcano, Alaska: radar observations  

USGS Publications Warehouse

ERS-1/ERS-2 synthetic aperture radar interferometry was used to study the 1997 eruption of Okmok volcano in Alaska. First, we derived an accurate digital elevation model (DEM) using a tandem ERS-1/ERS-2 image pair and the preexisting DEM. Second, by studying changes in interferometric coherence we found that the newly erupted lava lost radar coherence for 5-17 months after the eruption. This suggests changes in the surface backscattering characteristics and was probably related to cooling and compaction processes. Third, the atmospheric delay anomalies in the deformation interferograms were quantitatively assessed. Atmospheric delay anomalies in some of the interferograms were significant and consistently smaller than one to two fringes in magnitude. For this reason, repeat observations are important to confidently interpret small geophysical signals related to volcanic activities. Finally, using two-pass differential interferometry, we analyzed the preemptive inflation, coeruptive deflation, and posteruptive inflation and confirmed the observations using independent image pairs. We observed more than 140 cm of subsidence associated with the 1997 eruption. This subsidence occurred between 16 months before the eruption and 5 months after the eruption, was preceded by ?18 cm of uplift between 1992 and 1995 centered in the same location, and was followed by ?10 cm of uplift between September 1997 and 1998. The best fitting model suggests the magma reservoir resided at 2.7 km depth beneath the center of the caldera, which was ?5 km from the eruptive vent. We estimated the volume of the erupted material to be 0.055 km3 and the average thickness of the erupted lava to be ?7.4 m. Copyright 2000 by the American Geophysical Union.

Lu, Zhong; Mann, Dörte; Freymueller, Jeffrey T.; Meyer, David J.

2000-01-01

50

Synthetic aperture characterization of radar satellite constellations  

Microsoft Academic Search

The concept of radar satellite constellations, or clusters, for SAR and other radar modes has been proposed and is currently under research. These systems are composed of multiple, formation-flying satellites with each satellite having its own, coherent receiver. Increased swathwidth compared to that of traditional SAR is attainable by processing the spatial data obtained from multiple satellites. The multi-channel system

Nathan A. Goodman; James M. Stiles

2002-01-01

51

Analysis of synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

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.

Blanchard, B. J. (principal investigator)

1976-01-01

52

Broadband synthetic aperture borehole radar interferometry  

Microsoft Academic Search

Trials in mines have established that wideband VHF borehole radars (BHR), working in the 10–100-MHz band, can be used to probe the rockmass between boreholes over ranges from <5 m to as much as 150 m with submeter resolution. There is evidence that ore bodies reflect these radar signals both specularly and diffusely, much as the ground\\/air interface does when

I. Mason; N. Osman; Q. Liu; C. Simmat; M. Li

2001-01-01

53

The EcoSAR P-band Synthetic Aperture Radar  

Microsoft Academic Search

The EcoSAR instrument is a new concept in Synthetic Aperture Radar for the polarimetric and interferometric measure- ments of biomass and ecosystem structure. EcoSAR will employ a digital beamforming architecture, a highly capable digital wave- form generator and receiver system, and ad- vanced dual-polarization array antennas with an interferometric baseline of 25 m on the NASA P3 aircraft.

Rafael F. Rincon; Temilola Fatoyinbo; Guoqing Sun; K. Jon Ranson; Martin Perrine; Manohar Deshapnde; Quenton Bonds

2011-01-01

54

Millimeter-wave ground based synthetic aperture radar measurements  

Microsoft Academic Search

In this study, applications of millimeter wave ground based synthetic aperture radar (GB-SAR) experiments are studied. GB-SAR data collection setup is constructed and GB-SAR measurements of different objects are carried out in the semi-anechoic chamber room. Measurements from an aluminum target and metal pipe targets at the millimeter wave regions are collected by the newly constructed measurement setup. Also, real

Enes Yigit; Atilla Unal; Adem Kaya; Sevket Demirci; Harun Cetinkaya; Caner Ozdemir; Alexey Vertiy

2011-01-01

55

The Alaska synthetic aperture radar (SAR) facility project  

NASA Technical Reports Server (NTRS)

A receiving station for the acquisition and processing of spaceborne synthetic aperture radar (SAR) data is being established by the National Aeronautics and Space Administration (NASA) at the University of Alaska, Fairbanks. The data that will be received from a number of SAR satellites that are to be launched starting in 1990 will allow U.S. researchers to study sea ice, oceanographic and geological features, hydrological processes, glaciers, and vegetation cover in Alaska and its surrounding seas.

Carsey, F.; Jezek, K.; Miller, J.; Weeks, W.; Weller, G.

1987-01-01

56

Real-time optical synthetic aperture radar /SAR/ processor  

NASA Technical Reports Server (NTRS)

A description is given of a real-time optical synthetic aperture radar (SAR). The processor employs an acoustooptic device as the input electronic-to-optical transducer and a CCD camera that serves as the optical detector and simultaneously performs the focusing of the SAR image in the azimuth direction. The performance criteria of the optical processor that are discussed include azimuth resolution, image size in azimuth, range resolution, image size in range, flexibility, and dynamic range.

Psaltis, D.; Wagner, K.

1982-01-01

57

Polarimetric Synthetic Aperture Radar Data and the Complex Wishart Distribution  

Microsoft Academic Search

When working with multi-look fully polarimetric synthetic aperture radar (SAR) data an appropriate way of representing the\\u000a back-scattered signal consists of the so-called covariance matrix. For each pixel this is a 3×3 Hermitian, positive definite\\u000a matrix which follows a complex Wishart distribution. Based on this distribution a test statistic for equality of two such\\u000a matrices and an associated asymptotic probability

Allan Aasbjerg Nielsen; Knut Conradsen; Henning Skriver

2003-01-01

58

Synthetic aperture radar and digital processing: An introduction  

NASA Technical Reports Server (NTRS)

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.

Dicenzo, A.

1981-01-01

59

Synthetic aperture radar/LANDSAT MSS image registration  

NASA Technical Reports Server (NTRS)

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.

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

1979-01-01

60

Battlefield Radar Imaging Through Airborne Millimetric Wave SAR (Synthetic Aperture Radar).  

National Technical Information Service (NTIS)

Airborne synthetic aperture radar (SAR), operating in the millimetric-wave (mmw) region, is discussed with reference to a battlefield surveillance application. The SAR system provides high resolution real-time imaging of the battlefield and moving target ...

U. Carletti E. Daddio A. Farina C. Morabito R. Pangrazi

1988-01-01

61

Lincoln Laboratory millimeter-wave synthetic aperture radar imaging system  

NASA Astrophysics Data System (ADS)

The Lincoln Laboratory millimeter-wave synthetic aperture radar (SAR) imaging system is part of a DARPA-funded program that was established at Lincoln Laboratory to investigate the detection and classification of stationary targets using ultra-high resolution, fully polarimetric SAR and real aperture radar (RAR) data. The system consists of an airborne radar that operates at 33.56 GHz. The raw radar data are recorded on high density digital tapes that are sent to the Radar Data Analysis Center, which is located at Lincoln Laboratory in Lexington, Mass. This center processes the data to create calibrated SAR and RAR images. The Radar Data Analysis Center consists of a number of major data processing elements: an image formation processor, an archival storage and retrieval system, and a cluster of computer systems used for data analysis. In order to accomplish the goals of the DARPA program, it is essential that the radar data be very carefully calibrated. The calibration process consists of three major steps: (1) an internally generated calibration pulse is inserted into the radar receiver at the front end; (2) calibration targets (dihedrals and trihedrals) deployed on the ground are measured by the radar from the air and; (3) special calibration processing software uses the measurements from (1) and (2) to achieve polarimetric calibration. This paper describes the airborne radar, the ground processing facility, and the calibration process. Recent SAR images, generated from airborne measurements, of ground clutter and selected urban areas are presented. The images were generated using the polarimetric whitening filter (PWF), a novel processing technique developed at Lincoln Laboratory. The PWF process exploits the polarimetric measurement capability of the radar to create imagery that is nearly optical in quality.

Henry, John C.; Murphy, Thomas J.; Carusone, Kathleen M.

1992-05-01

62

Synthetic aperture radar range - Azimuth ambiguity design and constraints  

NASA Technical Reports Server (NTRS)

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.

Mehlis, J. G.

1980-01-01

63

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

NASA Technical Reports Server (NTRS)

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.

Vanzyl, Jakob J. (editor)

1991-01-01

64

Real-time synthetic aperture radar processing  

NASA Technical Reports Server (NTRS)

Real-time acousto-optic SAR processors are described and experimentally demonstrated. SAR imaging is performed in one of the architectures by applying the signal to an acousto-optic device and correlating it with chirp signals recorded on an optical transparency by time integration on a CCD detector. In a different implementation, the imaging is preformed by interfering the light beams diffracted from two separate acousto-optic devices, one modulated the radar signal and the second by the reference chirp waveform.

Psaltis, D.; Haney, M.; Wagner, K.

1984-01-01

65

Spaceborne synthetic aperture radar pilot study  

NASA Technical Reports Server (NTRS)

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.

1974-01-01

66

Interferometric synthetic aperture radar imagery of the Gulf Stream  

NASA Technical Reports Server (NTRS)

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.

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

67

Time-frequency analysis of synthetic aperture radar signals  

SciTech Connect

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.

Johnston, B.

1996-08-01

68

Spaceborne synthetic-aperture imaging radars - Applications, techniques, and technology  

NASA Technical Reports Server (NTRS)

In June 1978, the Seasat satellite was placed into orbit around the earth with a synthetic-aperture imaging radar (SAR) as one of the payload sensors. The Seasat SAR provided, for the first time, synoptic radar images of the earth's surface with a resolution of 25 m. In November 1981, the second imaging radar was successfully operated from space on the Shuttle. The Shuttle Imaging Radar-A acquired images over a variety of regions around the world with an imaging geometry different from the one used by the Seasat SAR. The spaceborne SAR principle is discussed, taking into account ambiguities, orbital and environmental factors, range curvature and range walk, surface interaction mechanisms, thermal and speckle noise, key tradeoff parameters, and nonconventional SAR systems. Attention is also given to spaceborne SAR sensors, the digital processing of spaceborne SAR data, the optical processing of spaceborne SAR data, postimage formation processing, data interpretation techniques and applications, and the next decade.

Elachi, C.; Bicknell, T.; Jordan, R. L.; Wu, C.

1982-01-01

69

Simulation of synthetic aperture radar 2: Simulating SAR (Synthetic Aperture Radar) using the advanced visual technology system  

Microsoft Academic Search

The Advanced Visual Technology System (AVTS) computer image generator was modified to produce highly accurate simulations of synthetic aperture radar (SAR) reflectively and elevation effects that can be precisely correlated with corresponding visual and infrared imagery. The resulting SAR snapshot is a plan view of the selected patch area with the field-of-view corresponding to a selected scale of 0.65, 1.3,

Robert L. Ferguson; John Ellis; Steven R. French; Jeanne Ball; Lisa Spencer; Herbert H. Bell; Peter M. Crane

1989-01-01

70

Multiregion level-set partitioning of synthetic aperture radar images.  

PubMed

The purpose of this study is to investigate Synthetic Aperture Radar (SAR) image segmentation into a given but arbitrary number of gamma homogeneous regions via active contours and level sets. The segmentation of SAR images is a difficult problem due to the presence of speckle which can be modeled as strong, multiplicative noise. The proposed algorithm consists of evolving simple closed planar curves within an explicit correspondence between the interiors of curves and regions of segmentation to minimize a criterion containing a term of conformity of data to a speckle model of noise and a term of regularization. Results are shown on both synthetic and real images. PMID:15875799

Ben Ayed, Ismail; Mitiche, Amar; Belhadj, Ziad

2005-05-01

71

A simulation of synthetic aperture radar imaging of ocean waves  

NASA Technical Reports Server (NTRS)

A simulation of radar imaging of ocean waves with synthetic aperture techniques is presented. The modelling is simplistic from the oceanographic and electromagnetic viewpoint in order to minimize the computational problems, yet reveal some of the physical problems associated with the imaging of moving ocean waves. The model assumes: (1) The radar illuminates a one-dimensional, one harmonic ocean wave. (2) The scattering is assumed to be governed by geometrical optics. (3) The radar is assumed to be down-looking, with Doppler processing (range processing is suppressed due to the one-dimensional nature of the problem). (4) The beamwidth of the antenna (or integration time) is assumed to be sufficiently narrow to restrict the specular points of the peaks and troughs of the wave. The results show that conventional processing of the image gives familiar results if the ocean waves are stationary. When the ocean wave dispersion relationship is satisfied, the image is smeared due to the motion of the specular points over the integration time. In effect, the image of the ocean is transferred to the near field of the synthetic aperture.

Swift, C. T.

1974-01-01

72

Application of synthetic aperture radar remote sensing in Antarctica  

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

73

A matched filter based synthetic aperture radar (SAR) algorithm for stepped frequency ground penetrating radar  

Microsoft Academic Search

We apply a matched filter based SAR algorithm to process ground penetrating radar data. The algorithm discussed is for a stepped frequency type radar although it can be applied to other types with few modifications. The selection of the synthetic aperture length considering the ground attenuation, antenna beam pattern and the scattering pattern of the object being imaged is also

Aruna Gunawardena; Dennis Longstaff

1995-01-01

74

SEASAT views oceans and sea ice with synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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.

Fu, L. L.; Holt, B.

1982-01-01

75

Two target height effects on interferometric synthetic aperture radar coherence  

SciTech Connect

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.

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

2000-03-07

76

Interferometric synthetic aperture radar studies of Alaska volcanoes  

USGS Publications Warehouse

Interferometric synthetic aperture radar (InSAR) imaging is a recently developed geodetic technique capable of measuring ground-surface deformation with centimeter to subcentimeter vertical precision and spatial resolution of tens-of-meter over a relatively large region (???104 km2). The spatial distribution of surface deformation data, derived from InSAR images, enables the construction of detailed mechanical models to enhance the study of magmatic and tectonic processes associated with volcanoes. This paper summarizes our recent InSAR studies of several Alaska volcanoes, which include Okmok, Akutan, Kiska, Augustine, Westdahl, and Peulik volcanoes.

Lu, Z.; Wicks, Jr. , C.; Power, J.; Dzurisin, D.; Thatcher, W.; Masterlark, T.

2002-01-01

77

Chinese progress toward marine applications of synthetic aperture radar  

NASA Astrophysics Data System (ADS)

This paper presents the progress toward marine applications of synthetic aperture radar (SAR) data and a review of the SAR satellite program in China. The technique development includes the development of algorithms and of methodology for extracting oceanographic parameters from SAR data. Marine applications range from environmental monitoring to oceanographic research. Two series of SAR satellites have been planned. The first SAR satellite of the Environmental and Disaster Monitoring Satellite series (HJ series) will be launched in 2009 while the first SAR satellite of the Ocean SAR Satellite series (HY-3 series) is in planning phase. A description is given of the instruments and their plateforms.

Huang, Weigen; Fu, Bi; Yang, Jingsong; Zhang, Huaguo; Fu, Bin; Chen, Peng; Xiao, Qinmei; Shi, Aiqing

2008-10-01

78

Remote sensing with spaceborne synthetic aperture imaging radars: A review  

NASA Technical Reports Server (NTRS)

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.

Cimino, J. B.; Elachi, C.

1983-01-01

79

A comparison of spotlight synthetic aperture radar image formation techniques  

SciTech Connect

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.

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

1996-10-01

80

Synthetic aperture radar and interferometry development at Sandia National Laboratories  

SciTech Connect

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.

NONE

1993-04-01

81

Phase and amplitude phase restoration in synthetic aperture radar imaging.  

PubMed

Methods for addressing two types of multiplicative noise in synthetic aperture radar (SAR) imaging are presented. The authors consider a multiplicative noise with a real phase (i.e. the SAR signal's phase is contaminated but its amplitude is uncorrupted) that possesses unknown functional characteristics with respect to the radar signal's temporal frequencies. A perturbation solution for phase reconstruction from amplitude is developed from a wave equation governing the SAR signal and a Riccati equation that relates the amplitude and phase functions of the SAR signal. This solution is converted into a noniterative analytical solution in terms of the moments and powers of the log amplitude function. Next, the authors consider a multiplicative noise with a complex phase (i.e. both the amplitude and phase of the SAR signal are contaminated) that varies linearly with respect to the radar signal's temporal frequencies. The two wave equations governing the SAR signal at two temporal frequencies of the radar signal are combined to derive a method to reconstruct the complex phase error function. PMID:18296157

Soumekh, M; Choi, J H

1992-01-01

82

Experiment in Onboard Synthetic Aperture Radar Data Processing  

NASA Technical Reports Server (NTRS)

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.

Holland, Matthew

2011-01-01

83

Use of synthetic aperture and stepped-frequency continuous wave processing to obtain radar images  

Microsoft Academic Search

This paper outlines the use of synthetic aperture radar processing techniques to obtain images from a stepped-frequency continuous wave radar. Theoretical, simulation and experimental results are presented

A. D. M. Garvin; M. R. Inggs

1991-01-01

84

Using Surface Pressure to Improve Tropical Cyclone Surface Wind Retrievals form Synthetic Aperture Radar Imagery.  

National Technical Information Service (NTIS)

The calibration and validation of surface wind and stress retrievals from oceanic synthetic aperture radar (SAR) imagery is especially difficult in tropical cyclone (TC) conditions. The geophysical model functions (GMFs) that characterize the radar backsc...

J. Patoux R. Foster

2013-01-01

85

A novel method for estimating offshore wind fields using synthetic aperture radar and meteorological model data  

Microsoft Academic Search

Synthetic aperture radar (SAR) provides a promising method for offshore wind field estimation, particularly in the context of important for offshore wind farm development. This paper introduces an iterative maximum aposteriori probability (MAP) method for combining meteorological model output with synthetic aperture radar for offshore wind field estimation. The MAP approach is demonstrated for 40 ENVISAT ASAR scenes collected for

I. D. Cameron; I. H. Woodhouse; N. Walker

2007-01-01

86

Fusion of multiple-look synthetic aperture radar images at data and image levels  

Microsoft Academic Search

Synthetic aperture radar (SAR) and inverse synthetic aperture radar (ISAR) have proven capabilities for non-cooperative target recognition (NCTR) applications. Multiple looks of the same target (at different aspect angles, frequencies, etc.) can be exploited to enhance target recognition by fusing the information from each look. Such fusion can be performed at the raw data level or at the processed image

Ram M. Narayanan; Zhixi Li; Scott Papson

2008-01-01

87

Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Radar Imagery  

SciTech Connect

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

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

1999-06-29

88

Synthetic aperture radar imagery scene segmentation using fractal processing  

NASA Astrophysics Data System (ADS)

This paper demonstrates the application of fractal random process models and their related scaling parameters as features in the analysis and segmentation of clutter in high-resolution polarimetric synthetic aperture radar (SAR) imagery. Specifically, the fractal dimension of natural clutter sources, such as grass and trees, is computed and used as a texture feature for a Bayesian classifier. The SAR shadows are segmented in a separate manner using the original backscatter power as a discriminant. The proposed segmentation process yields a three-class segmentation map for the scenes considered in this study (with three clutter types: shadows, trees and grass). The difficulty of computing texture metrics in high-speckle SAR imagery is also addressed. In particular, a two-step preprocessing approach consisting of polarimetric minimum speckle filtering followed by non-coherent spatial averaging is used. The relevance of the resulting segmentation maps to constant-false-alarm-rate (CFAR) target detection techniques is also discussed.

Stewart, Clayton V.; Moghaddam, Baback; Hintz, Kenneth J.

1992-07-01

89

Perceptual compression of magnitude-detected synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

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.

Gorman, John D.; Werness, Susan A.

1994-01-01

90

Topography estimation with interferometric synthetic aperture radar using fringe detection  

NASA Technical Reports Server (NTRS)

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.

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

1991-01-01

91

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

SciTech Connect

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 toget 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 theseek time'.

Doerry, Armin Walter

2013-11-01

92

Moving receive beam method and apparatus for synthetic aperture radar  

DOEpatents

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.

Kare, Jordin T. (San Ramon, CA)

2001-01-01

93

Synthetic aperture radar automatic target recognition based on curvelet transform  

NASA Astrophysics Data System (ADS)

A novel synthetic aperture radar (SAR) automatic target recognition (ATR) approach based on Curvelet Transform is proposed. However, the existing approaches can not extract the more effective feature. In this paper, our method is concentrated on a new effective representation of the moving and stationary target acquisition and recognition (MSTAR) database to obtain a more accurate target region and reduce feature dimension. Firstly, MSTAR database can be extracted feature through the optimal sparse representation by curvelets to obtain a clear target region. However, considering the loss of part of edges of image. We extract coarse feature, which is to compensate fine feature error brought by segmentation. The final features consisting of fine and coarse feature are classified by SVM with Gaussian radial basis function (RBF) kernel. The experiments show that our proposed algorithm can achieve a better correct classification rate.

Wang, Shuang; Liu, Zhuo; Jiao, Licheng; He, Jun

2009-10-01

94

Theory and design of interferometric synthetic aperture radars  

NASA Astrophysics Data System (ADS)

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.

Rodriguez, E.; Martin, J. M.

1992-04-01

95

The Rapid Terrain Visualization interferometric synthetic aperture radar sensor.  

SciTech Connect

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.

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

2003-07-01

96

Computing Ocean Surface Currents from Satellite Synthetic Aperture Radar Imagery  

NASA Astrophysics Data System (ADS)

Ocean surface currents play an important role in ocean-atmosphere interactions and global ocean circulation, and are also significant for fishing, ocean navigation, and search & rescue. Existing in-situ and remote sensing techniques for measuring ocean surface currents are limited by spatial and temporal data coverage, and thermal IR feature tracking methods are limited by clouds and weak thermal gradients. High-resolution spaceborne Synthetic Aperture Radar (SAR) offers repeatable cloud-penetrating measurements of the ocean surface. This research explores methods for ocean surface current measurement through satellite-based SAR. The major part of this research is concerned with the development and application of a semi-automated algorithm to generate ocean surface currents at ˜1.9 km resolution from sequential spaceborne C-band SAR intensity images using the Maximum Cross-Correlation(MCC) method. The primary geographical area of study is the coastal California Current System (CCS), and nearly two years (2008-2009) of 30-min lag data from the Envisat ASAR and ERS-2 AMI SAR sensors is analyzed. The velocity wavenumber spectrum of the derived MCC SAR currents agrees with the k-2 power law as predicted by submesoscale resolution models, and also shows seasonal mesoscale variability. The derived MCC SAR currents are validated against High frequency (HF) radar currents, and the two show some agreement in vector direction, with MCC SAR vectors oriented slightly anti-clockwise relative to HF radar vectors. The unimodal mean-symmetric residual histograms indicate that errors between the two datasets are random, except for a mean positive bias of ? 11 cm/s in MCC SAR currents relative to HF radar currents. This magnitude difference occurs primarily in the along-shore component ( ? 6 cm/s) and is negligible in the cross-shore component. Doppler Centroid Cross-Track (XT) radial currents from Envisat Wide Swath Mode (WSM) scenes are compared with HF radar radial currents, and are seen to have much larger extreme values, which is attributed to the Doppler wind correction process. Ignoring the extreme values, errors between the two datasets appear to be random, with a near-zero mean bias, and are also linked with the Doppler radial estimation errors attributed to model wind corrections. Comparison of Doppler radials with MCC SAR radials for two ? 12-hour lag cases also shows promising results. Finally, experiments conducted with TerraSAR-X experimental Dual Receive Aperture (DRA) mode Along-Track Interferometry (ATI) datasets suggest possible solutions for the absolute phase calibration problem using interferometric phase over ocean only.

Qazi, Waqas A.

97

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

Microsoft Academic Search

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

Mehrdad Soumekh

1997-01-01

98

A simulator for the Seasat-A synthetic aperture radar ground support network  

Microsoft Academic Search

The characteristics and capabilities of link measurement and simulation equipment for the NASA ground stations supporting the Seasat-A synthetic aperture radar (SAR) are described. The Spaceflight Tracking and Data Network (STDN) Seasat-A SAR Simulator generates SAR radar and data link signals, including chirp, radar return, pilot, PRN radar timing, and noise components. After injection into and passage through the STDN

S. C. Jones; J. D. Colson; P. J. Grunberger

1978-01-01

99

Three-dimensional subsurface imaging synthetic aperture radar  

SciTech Connect

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.

Moussally, G.J.

1995-03-01

100

New formulation for interferometric synthetic aperture radar for terrain mapping  

NASA Astrophysics Data System (ADS)

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 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 3D computerized axial tomography (CAT) was developed. After outlining the major steps in the mathematics, we show how a computer simulator which utilizes 3D Fourier transforms can be constructed that demonstrates all of the major aspects of IFSAR from spotlight mode collections.

Jakowatz, Charles V.; Wahl, Daniel E.; Eichel, Paul H.; Thompson, Paul A.

1994-06-01

101

Synthetic aperture radar signal processing on the MPP  

NASA Technical Reports Server (NTRS)

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.

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

1987-01-01

102

Correlation of oceanographic signatures appearing in synthetic aperture radar and interferometric synthetic aperture radar imagery with in situ measurements  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar (SAR) imagery collected over the continental shelf near Cape Hatteras, N. C., is analyzed in conjunction with shipboard hydrographic and current measurements. The SAR measurements were made over a 2-hour period on June 20, 1993, in both standard mapping mode and interferometric synthetic aperture radar (INSAR) mode from a NASA DC-8 aircraft as part of the High-Resolution Remote Sensing Experiment. In situ currents were measured using a surface-towed acoustic Doppler current profiler (ADCP). The measurements were made near the end of a period of Gulf Stream incursion onto the shelf as detected using a shore-based HF radar. Winds were southwesterly at 4-6 m s-1. Long, curvilinear SAR signatures, resembling earlier SEASAT observations made in the same area, are shown to correspond to narrow, shallow fronts separating water masses that increase in surface density with distance offshore. Across-front changes in surface current inferred from the INSAR data are consistent with 2-m-depth currents measured by the ADCP over scales of tens of meters. Thus frontal current gradients measured by INSAR reflect real changes in surface current and are not due to biases induced by changes in the surface-wave spectrum. This lends support to the detailed INSAR surface maps derived by Graber et al. [1996]. An east-west salinity front having the largest observed surface density and current gradient is corrugated on length scales up to the local Rossby radius of deformation and translates southward between successive images. In data from the longer radar wavelengths the salinity front appears as a dark band downwind of a bright signature, and this is interpreted as a region where Bragg-scale waves regenerate following their dissipation in the frontal region. In addition to the fronts the imagery shows closely spaced packets of southward propagating ocean internal waves occurring in the strongly stratified inshore water mass. This case study further serves to emphasize the potential of SAR imagery for study of a wide range of shelf processes.

Marmorino, G. O.; Thompson, D. R.; Graber, H. C.; Trump, C. L.

1997-08-01

103

New inverse synthetic aperture radar algorithm for translational motion compensation  

NASA Astrophysics Data System (ADS)

Inverse synthetic aperture radar (ISAR) is an imaging technique that shows real promise in classifying airborne targets in real time under all weather conditions. Over the past few years a large body of ISAR data has been collected and considerable effort has been expended to develop algorithms to form high-resolution images from this data. One important goal of workers in this field is to develop software that will do the best job of imaging under the widest range of conditions. The success of classifying targets using ISAR is predicated upon forming highly focused radar images of these targets. Efforts to develop highly focused imaging computer software have been challenging, mainly because the imaging depends on and is affected by the motion of the target, which in general is not precisely known. Specifically, the target generally has both rotational motion about some axis and translational motion as a whole with respect to the radar. The slant-range translational motion kinematic quantities must be first accurately estimated from the data and compensated before the image can be focused. Following slant-range motion compensation, the image is further focused by determining and correcting for target rotation. The use of the burst derivative measure is proposed as a means to improve the computational efficiency of currently used ISAR algorithms. The use of this measure in motion compensation ISAR algorithms for estimating the slant-range translational motion kinematic quantities of an uncooperative target is described. Preliminary tests have been performed on simulated as well as actual ISAR data using both a Sun 4 workstation and a parallel processing transputer array. Results indicate that the burst derivative measure gives significant improvement in processing speed over the traditional entropy measure now employed.

Bocker, Richard P.; Henderson, Thomas B.; Jones, Scott A.; Frieden, B. R.

1991-10-01

104

An ERS-1 synthetic aperture radar image of a tropical squall line compared with weather radar data  

Microsoft Academic Search

A radar image acquired by the C-band synthetic aperture radar (SAR) aboard the European Remote Sensing satellite ERS-2 over the coastal waters south of Singapore showing radar signatures of a strong tropical squall line (“Sumatra Squall”) is compared with coincident and collocated weather radar data. Squall line features such as the gust front, areas of updraft convergence, and rain areas

I.-I. Lin; W. Alpers; V. Khoo; H. Lim; T. K. Lim; D. Kasilingam

2001-01-01

105

Synthetic Aperture Radar Using Random Signals. Part I. Discrete Arrays.  

National Technical Information Service (NTIS)

The report introduces a signal processor structure for synthetic array processing in conjunction with a random signal radar. Displayed in its elemental form, the processor configuration consists of a bank of cross-correlators followed by a tapped delay li...

G. R. Cooper K. W. Moran

1973-01-01

106

Synthetic aperture radar autofocus based on a bilinear model.  

PubMed

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

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

2012-05-01

107

Lynx: A High-Resolution Synthetic Aperture Radar  

SciTech Connect

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.

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

1999-03-08

108

Flight test of a synthetic aperture radar antenna using STEP  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

109

Farmland detection in synthetic aperture radar images with texture signature  

NASA Astrophysics Data System (ADS)

The detection of farmland in synthetic aperture radar (SAR) images is useful to compute agriculture distribution in mountainous regions. The SAR technology is helpful to government agencies compiling much needed information for agricultural assessment of need-based data. We propose a texture signature to detect farmland in SAR. The texture signature is extracted from the texture pixels of the SAR image through the fuzzy c-means, where each texture pixel is a vector whose elements are the convolution value of the filters of the normalized Gaussian derivatives and SAR images at a spatial position. Then, we use the texture signatures to detect farmland in SAR images through the earth mover's distance method. In the end, we propose a different approach to compute both the true positive rate and the false positive rate of receiver operating characteristic (ROC) curve. We use the area under the curve of ROC to achieve the best sample and the best threshold which realizes the best detection. The experiment results also show the best performance of the detection.

Xu, Wentao; Zhang, Guixu; Duan, Ye

2014-01-01

110

Target discrimination in synthetic aperture radar using artificial neural networks.  

PubMed

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

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

1998-01-01

111

Battlefield radar imaging through airborne millimetric wave SAR (Synthetic Aperture Radar)  

Microsoft Academic Search

Airborne synthetic aperture radar (SAR), operating in the millimetric-wave (mmw) region, is discussed with reference to a battlefield surveillance application. The SAR system provides high resolution real-time imaging of the battlefield and moving target detection, under adverse environmental conditions (e.g., weather, dust, smoke, obscurants). The most relevant and original aspects of the system are the band of operation (i.e., mmw

U. Carletti; E. Daddio; A. Farina; C. Morabito; R. Pangrazi; F. A. Studer

1988-01-01

112

Dual frequency Synthetic Aperture Radar (SAR) mission for monitoring our dynamic planet  

NASA Technical Reports Server (NTRS)

Advances in spaceborne Synthetic Aperture Radar (SAR) remote sensing technology make it possible to acquire global-scale data sets that provide unique information about the Earth's continually changing surface characteristics.

Hilland, J.; Bard, S.; Key, R.; Kim, Y.; Vaze, P.; Huneycutt, B.

2000-01-01

113

Interferometric Synthetic Aperture Radar Imaging of Ocean Surface Currents and Wavefields.  

National Technical Information Service (NTIS)

The potential of a method to remotely measure near-surface currents and dominant wave spectra using Interferometric Synthetic Aperture Radar INSAR is demonstrated. INSAR consists of a single conventional SAR augmented by an additional receiving antenna. T...

M. Marom

1990-01-01

114

Motion Compensation Requirements for a High Resolution Spotlight SAR (Synthetic Aperture Radar).  

National Technical Information Service (NTIS)

The Canadian Department of National Defense is developing a high resolution airborne spotlight synthetic aperture radar (SAR). To attain the high contrast, high resolution and low geometric distortion objectives of the project, it is essential that very a...

J. S. A. Hepburn G. E. Haslam D. F. Liang W. S. Widnall

1986-01-01

115

Development of a Synthetic Aperture Radar Design Approach for Wide-Swath Implementation.  

National Technical Information Service (NTIS)

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 selec...

B. R. Jean

1981-01-01

116

Gabor Filters and Neural Networks for Segmentation of Synthetic Aperture Radar Imagery.  

National Technical Information Service (NTIS)

This research investigates Gabor filters and artificial networks for autonomous segmentation of 1 foot by 1 foot) high resolution polarimetric synthetic aperture radar (SAR). Processing involved frequency correlation between the SAR imagery and biological...

A. P. L'Homme

1990-01-01

117

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

NASA Technical Reports Server (NTRS)

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.

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

1994-01-01

118

The Information Content of Interferometric Synthetic Aperture Radar: Vegetation and Underlying Surface Topography  

NASA Technical Reports Server (NTRS)

This paper first gives a heuristic description of the sensitivity of Interferometric Synthetic Aperture Radar to vertical vegetation distributions and underlying surface topography. A parameter estimation scenario is then described in which the Interferometric Synthetic Aperture Radar cross-correlation amplitude and phase are the observations from which vegetation and surface topographic parameters are estimated. It is shown that, even in the homogeneous-layer model of the vegetation, the number of parameters needed to describe the vegetation and underlying topography exceeds the number of Interferometric Synthetic Aperture Radar observations for single-baseline, single-frequency, single-incidence-angle, single-polarization Interferometric Synthetic Aperture Radar. Using ancillary ground-truth data to compensate for the underdetermination of the parameters, forest depths are estimated from the INSAR data. A recently-analyzed multibaseline data set is also discussed and the potential for stand-alone Interferometric Synthetic Aperture Radar parameter estimation is assessed. The potential of combining the information content of Interferometric Synthetic Aperture Radar with that of infrared/optical remote sensing data is briefly discussed.

Treuhaft, Robert N.

1996-01-01

119

The Spaceborne Imaging Radar-C, X-Band Synthetic Aperture radar (SIR-C/X-SAR) Mission Overview  

NASA Technical Reports Server (NTRS)

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. Soon after launch, the radars were activated and began around the clock operations which lasted for the next 10 days.

Evans, D. L.; Stofan, E. R.; Farr, T.; Plaut, J.; vanZyl, J.; Kobrick, M.; Holt, B.; Way, J. B.; Ottl, H.; Schmullius, C.; Nithack, J.; Calamia, M.

1994-01-01

120

Ice island detection and characterization with airborne synthetic aperture radar  

SciTech Connect

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.

Jeffries, M.O.; Sackinger, W.M. (Univ. of Alaska, Fairbanks (United States))

1990-04-15

121

HeliRadar: A rotating antenna synthetic aperture radar for helicopter allweather operations  

NASA Astrophysics Data System (ADS)

Today, available radar instruments cannot be applied for flight guidance purposes due to lack of resolution and ground elevation information. On the other side, optical sensors such as infrared systems provide an excellent resolution but are nearly blind at adverse weather conditions such as fog and rain. A new radar technology called ROSAR (Synthetic Aperture Radar based on ROtating antennas) promises to overcome the deficiencies of the traditional radar systems. On the basis of encouraging research work on ROSAR-technology and an investigation of the feasibility of a piloting system based on these ideas, Eurocopter Deutschland and Deutsche Aerospace started a development program called HeliRadar to develop a ROSAR-based piloting system. This device should be able to provide photolike images even under extreme visibility conditions. Details on the investigation and the resulting concepts for synthetic vision based flight guidance at Eurocopter will be given. Following an introduction to the basics of ROSAR-technology, the technical concept of HeliRadar will be presented. The paper concludes with a discussion of the perspectives for civil and military applications.

Kreitmair-Steck, W.; Wolframm, A. P.

1995-03-01

122

Performance of coherent-on-receive synthetic aperture side looking airborne radar  

Microsoft Academic Search

The Coast Guard's Oil Slick Detection Side Looking Airborne Radar was modified to add a synthetic aperture mode. The modification used the technologies of real time digital synthetic aperture processing and making the existing magnetron transmitter\\/receiver unit coherent-on-receive. Improvement in resolution by a factor of ten and imaging of the ocean surface and moving vessels were demonstrated. Synthetic oil slicks,

D. E. Fraser; G. V. Morris

1976-01-01

123

Determination of the velocity of ocean gyres through Synthetic Aperture Radar  

Microsoft Academic Search

The imaging process of a sensor is affected by the motion of the target. The simple optical image undergoes blurring due to target motion, but the more complex aperture synthesis process of the Synthetic Aperture Radar (SAR) results in a shift in the position of the moving target. The different parts of an extended non-linear target (such as an ocean

H. I. Andharia

1987-01-01

124

A spectral domain approach to modelling of EM scattering for Synthetic Aperture Radar target recognition  

Microsoft Academic Search

A Fourier-based technique for electromagnetic (EM) wave reconstruction with application to polarimetric airborne and spaceborne radar data exploitation is presented. The method is different from conventional modelling techniques for Synthetic Aperture Radar (SAR) applications as a result of the full electromagnetic treatment of field interactions with the scatterer, the possibility of introducing new and controllable feature classes for target classification,

R. Sabry; P. W. Vachon

2005-01-01

125

Parametric Velocity Synthetic Aperture Radar:Signal Modeling and Optimal Methods  

Microsoft Academic Search

Velocity synthetic aperture radar (VSAR) is equipped with a linear array to receive the echoes from a radar illuminating area via multiple channels, each of which can reconstruct a reflectivity image for the same stationary scene. Based on analysis of pixel vector sampled among multi-images, VSAR may effectively suppress the strong ground clutter and improve moving target detection and location.

Jia Xu; Gang Li; Ying-Ning Peng; Xiang-Gen Xia; Yong-Liang Wang

2008-01-01

126

A theory of the imaging mechanism of underwater bottom topography by real and synthetic aperture radar  

Microsoft Academic Search

A simple theoretical model of the imaging mechanism of underwater bottom topography in tidal channels by real and by synthetic aperture radar (SAR) is presented. The imaging is attributed to surface effects induced by current variations over bottom topography. The current modulates the short-scale surface roughness, which in turn gives rise to changes in radar reflectivity. The bottom topography-current interaction

Werner Alpers; Ingo Hennings

1984-01-01

127

Experimental evaluation of cursors for B2 Synthetic Aperture Radar (SAR) application  

Microsoft Academic Search

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

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

1993-01-01

128

Main Features of the X-SAR (X-band Synthetic Aperture Radar) Project.  

National Technical Information Service (NTIS)

The X-SAR is an imaging Shuttle-borne synthetic aperture X-band radar for Earth observation from space. Together with SIR-C, X-SAR will become a multifrequency-multipolarization SAR facility (Shuttle Radar Lab). Three missions are planned, and the possibi...

M. Wahl P. Ammendola

1988-01-01

129

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

Microsoft Academic Search

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

John F. Vesecky; Robert H. Stewart

1982-01-01

130

Modified space-time adaptive processing for dismount detection using synthetic aperture radar  

Microsoft Academic Search

This paper presents a new adaptive radar signal processing technique for dismount detection using Synthetic Aperture Radar (SAR). The new approach uses the complex nature of the Doppler response scattering from the dismounts rotary motion to modify the conventional Space-Time Adaptive Processing (STAP). This is used for dismount detection wherein resolution is dictated by the sensor system platform. The feasibility

Ke Yong Li; Faruk Uysal; S. Unnikrishna Pillai; Linda J. Moore

2012-01-01

131

Land-cover classification and estimation of terrain attributes using synthetic aperture radar  

Microsoft Academic Search

This paper presents progress toward a geophysical and biophysical information processor for synthetic aperture radar (SAR). This processor operates in a sequential fashion to first classify terrain according to structural attributes and then apply class-specific retrievals for geophysical and biophysical properties. Structural and electrical attributes control the radar backscattering from terrain. Experimental data and theoretical results illustrate the sensitivity of

M. Craig Dobson; Fawwaz T. Ulaby; Leland E. Pierce

1995-01-01

132

Screening of Earthen Levees Using Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

Earthen levees protect large areas of populated and cultivated land in the US from flooding. As shown recently with hurricanes Katrina and Ike and the recent floods in the Midwest, the potential loss of life and property associated with the catastrophic failure of levees can be extremely large. Over the entire US, there are over 100,000 miles of levee structures of varying designs and conditions. Currently, there are limited processes in place to prioritize the monitoring of large numbers of dam and levee structures. Levee managers and federal agencies need to assess levee health rapidly with robust techniques that identify, classify and prioritize levee vulnerabilities with lower costs than traditional soil-boring programs, which can cost many of millions of dollars and provide information about the subsurface only in the immediate vicinity of a small-diameter borehole. This paper reports preliminary results of a project studying the use of airborne synthetic aperture radar (SAR) as an aid to the levee screening process. The SAR sensor being studied is the NASA UAVSAR (Unmanned Aerial Vehicle SAR), a fully polarimetric L-band SAR which is specifically designed to acquire airborne repeat track SAR data for differential interferometric measurements. The instrument is capable of sub-meter ground sample distance. NASA has imaged with this instrument 230 km of levees along the lower Mississippi River for use in this study. SAR interferometric mode is capable of identifying vertical displacements on the order of a few millimeters. Its multipolarization measurements can penetrate soil to as much as one meter depth. Thus it is valuable in detecting changes in levees that will be key inputs to a levee vulnerability classification system. Once vulnerable levee reaches have been identified, further actions such as more detailed examination or repairs can be focused on these higher-priority sections. We report on the use of various feature detection algorithms being applied to the polarimetry data, including entropy-anisotropy decomposition and methods based on the Grey Level Co-occurrence Matrix (GLCM). The features detected are compared with various ground truth data including soil type maps, soil conductivity measurements, and on site visual inspections.

Aanstoos, J. V.; O'Hara, C.; Prasad, S.; Dabbiru, L.; Nobrega, R.; Lee, M.

2009-12-01

133

Model-Based Information Extraction From Synthetic Aperture Radar Signals  

NASA Astrophysics Data System (ADS)

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.

Matzner, Shari A.

134

Synthetic-aperture-radar imaging with a solid-state laser.  

PubMed

We report the operation of an imaging Nd:YAG microchip-laser synthetic-aperture radar, with which we imaged two-dimensional (2-D) models of military targets. The images obtained showed spatial resolution significantly better than the diffraction limit of the real aperture in the along-track dimension. The signal processing is described, and the measurement sensitivity is both predicted and verified. In addition, 2-D images with high resolution in both dimensions were generated by using an asymmetric aperture to match the along-track synthetic-aperture resolution with the across-track diffraction-limited resolution. PMID:21060556

Green, T J; Marcus, S; Colella, B D

1995-10-20

135

Preliminary results from the NASA\\/JPL multifrequency, multipolarization synthetic aperture radar  

Microsoft Academic Search

A brief description is given of the three-frequency polarimetric synthetic-aperture radar built and tested at the Jet Propulsion Laboratory. The radar has the capability to simultaneously acquire fully polarimetric data at P-, L-, and C-bands from a DC-8 airborne platform. The radar has an instantaneous data rate of approximately 2.1 Gb\\/s and has selectable record rates between 80-240 Mb\\/s. The

D. N. Held; W. E. Brown; T. W. Miller

1988-01-01

136

Phase correction system for automatic focusing of synthetic aperture radar  

DOEpatents

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.

Eichel, Paul H. (Albuquerque, NM); Ghiglia, Dennis C. (Placitas, NM); Jakowatz, Jr., Charles V. (Albuquerque, NM)

1990-01-01

137

Autofocus algorithm for synthetic aperture radar imaging with large curvilinear apertures  

NASA Astrophysics Data System (ADS)

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.

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

2013-05-01

138

Synthetic aperture radar imaging using a unique approach to frequency-modulated continuous-wave radar design  

Microsoft Academic Search

Synthetic-aperture-radar (SAR) imaging is an expensive endeavor. It can be difficult for universities, small business, or individuals to experiment with SAR imaging and algorithm development on a low budget. For this reason, a uniquely inexpensive solution to frequency-modulated continuous-wave (FMCW) radar was developed and then utilized as an ultra-low-cost SAR imaging system. This unique approach to FMCW radar used a

G. L. Charvat; Leo C. Kempel

2006-01-01

139

Modeling of Complex Radar Target for High-Resolution Synthetic Aperture Radar Image Simulation Based on GRECO  

Microsoft Academic Search

The electromagnetic scattering models of complex radar targets, e.g. aircrafts, vehicles etc, are of great significance to Automatic Target Recognition (ATR) of Synthetic Aperture Radar (SAR) imagery. Based on the Graphical Electromagnetic Computing (GRECO) technique, a novel implementation method of complex radar target modeling for the simulation of high-resolution SAR image is proposed. The three-dimensional (3-D) scattering modeling of the

Jie Chen; Lin Li; Shaobin Li; Zhou Li

2009-01-01

140

On a Novel Approach Using MLCC and CFAR for the Improvement of Ship Detection by Synthetic Aperture Radar  

Microsoft Academic Search

Multilook cross correlation (MLCC) is a useful technique in extracting the images of ships embedded in heavy sea clutter by synthetic aperture radar (SAR). In the ship detection experiment in 2006 by Phased Array L-band Synthetic Aperture Radar (PALSAR) on board the Advanced Land Observing Satellite, we applied MLCC to PALSAR data in order to extract small fishing boats. The

Seong-In Hwang; Kazuo Ouchi

2010-01-01

141

Computer processing of SAR L-band imagery. [Synthetic Aperture Radar for ice mapping  

NASA Technical Reports Server (NTRS)

The described work in the areas of hydrology and polar ice defines possible uses of automatic picture processing of uncalibrated radar images. The data used in the study were collected with the aid of an L-band synthetic aperture radar mounted in the NASA CV-990 aircraft. The radar was operated at approximately 30,000 feet altitude. One study area used was located in the Beaufort Sea and contained sea ice. The other study area contained lakes on the Alaskan North Slope. The reported investigations demonstrate that certain types of features can be efficiently studied by using simple automatic picture processing techniques applied to uncalibrated radar data.

Bryan, M. L.; Stromberg, W. D.; Farr, T. G.

1977-01-01

142

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

NASA Technical Reports Server (NTRS)

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.

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

1980-01-01

143

A dual-polarised wideband planar array for X-band synthetic aperture radar  

Microsoft Academic Search

This paper describes the design and performance of a wideband planar array panel for use in a dual linear-polarisation antenna for the Australian Defence Science and Technology Organisation (DSTO) Ingara X-band airborne synthetic aperture radar (SAR). The final array aperture is approximately 1200 mm by 200 mm and comprises 192 dual-fed microstrip patch elements divided into three panels, each panel

A. Parfitt; N. Nikolic

2001-01-01

144

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

NASA Technical Reports Server (NTRS)

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.

Sivertson, W. E., Jr.

1976-01-01

145

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

NASA Technical Reports Server (NTRS)

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.

Jean, B. R.

1981-01-01

146

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

NASA Astrophysics Data System (ADS)

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.

Jean, B. R.

1981-09-01

147

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

SciTech Connect

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.

Eichel, Paul H.

2005-09-01

148

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

PubMed

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

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; Raki?, A D

2014-05-01

149

On the application of coherent optical processing techniques to synthetic-aperture radar  

Microsoft Academic Search

Coherent optical systems are useful for the processing of data collected by sidelooking synthetic-aperture radars. This type of radar, which is useful for generating fine-resolution terrain imagery, has the capability of providing along-track, or azimuth, resolution which is much finer than the azimuth dimension of the radiated beam itself; however, the attainment of this finer resolution requires extensive processing of

L. J. Cutrona; E. N. Leith; L. J. Porcello; W. E. Vivian

1966-01-01

150

Synthetic aperture radar imaging of axial convergence fronts in Cook Inlet, Alaska  

Microsoft Academic Search

Axial fronts of tidal currents are observed in Cook Inlet, AK, on a RADARSAT-1 standard mode synthetic aperture radar (SAR) image taken at 16:31:47 coordinated universal time (UTC) on July 12, 2002. The longest front appears as a 100-km-long quasi-linear bright feature in the SAR image. This front is characterized by an increase in the normalized radar cross section (NRCS)

Xiaofeng Li; Chunyan Li; William G. Pichel; Pablo Clemente-Colón; Karen S. Friedman

2005-01-01

151

A comparison of Geosat altimeter and synthetic aperture radar measurements over east Greenland pack ice  

Microsoft Academic Search

Altimetry over sea ice has attracted attention as a possible source of geophysical information. However, the interpretation of altimeter data records over ice has been hampered by a lack of high-resolution imagery for comparison. In this paper we compare Geosat altimeter data along a track over pack ice east of Greenland with coincident synthetic aperture radar data obtained as part

FLORENCE M. FETTERER; SEYMOUR LAXON; DONALD R. JOHNSON

1991-01-01

152

Estimation of ocean wave height using polarization ratio of synthetic aperture radar data  

Microsoft Academic Search

Anewtechniqueforestimatingwaveheight ofrange-traveling ocean waves by using the polarization ratio of synthetic aperture radar (SAR) data is proposed. Unlike the previous methods based on scattering models such as composite surface model [1], the new method does not require any scattering models that strongly affect the estimation accuracy. First, the dependence of the polarization ratio on local incidence angles and its application

Mitsunobu Sugimoto; Nobuaki Shiroto; Kazuo Ouchi

2011-01-01

153

Target Discrimination in Synthetic Aperture Radar (SAR) using Artificial Neural Networks  

Microsoft Academic Search

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 will show that the two applications require different cost func- tions. We start by analyzing with a pattern recognition perspective the two-parameter constant false alarm rate (CFAR) detector

Jose C. Principe; Munchurl Kim; John W. Fisher

154

Synthetic aperture radar for DEM generation in snow-covered mountain terrain  

Microsoft Academic Search

Digital elevation model (DEM) generation has mainly been based on optical imagery and photogrammetric techniques. However, in recent years there has been a growing interest in the use of synthetic aperture radar (SAR) for this purpose. It is mainly two techniques that are used, SAR interferometry and stereoSAR. We have studied the influence of the snow cover on the accuracy

Kjell Arild Hogda; Tore Guneriussen; Inge Lauknes

2002-01-01

155

Differential Synthetic Aperture Radar Interferometry in monitoring large landslide (La Frasse, Switzerland)  

Microsoft Academic Search

Spaceborne Differential Interferometric Synthetic Aperture Radar (DInSAR) is able to detect quasi vertical movements covering very large areas in a continuous way; it can be considered as an efficient tool to detect and monitor slope instabilities. The La Frasse landslide is located in the Canton of Vaud (Switzerland). It has a length of 2 km, a width of 500 m

C. Michoud; T. Rune Lauknes; A. Pedrazzini; M. Jaboyedoff; R. Tapia; G. Steinmann

2009-01-01

156

Crop Classification with Multi-Temporal X-Band SAR (Synthetic Aperture Radar) Data.  

National Technical Information Service (NTIS)

Multitemporal X-band HH polarized synthetic aperture radar data were used to classify crop type. Prior to the classification, the influence of non-crop variables on crop separability were evaluated. While the influence of the soil moisture content was uni...

G. M. Foody P. J. Curran G. B. Groom D. C. Munro

1988-01-01

157

Multi?temporal airborne synthetic aperture radar data for crop classification  

Microsoft Academic Search

This paper presents an approach to the classification of crop type using multi?temporal airborne synthetic aperture radar (SAR) data. Following radiometric correction of the data the accuracy of a per?field crop classification reached 90% for three classes using data acquired on four dates. A comparable accuracy of 88% could be obtained for a classification of the same classes using data

G. M. Foody; P. J. Curran; G. B. Groom; D. C. Munro

1989-01-01

158

Space-based surface change detection with differential Synthetic Aperture Radar (SAR) Interferometry: potentialities and preliminary  

Microsoft Academic Search

The capability of measuring small crustal deformation by means of differential Synthetic Aperture Radar (SAR) interferometry (DIFSAR) is investigated in this work. After outlining the mathematical background inherent to the principles of differential SAR interferometry and showing the potential and limits of the information content of spaceborne DIFSAR data, the analysis of the impact of this technique is carried out

Antonio Vettore; Salvatore Ponte; Nicola Crocetto

159

Integrated satellite interferometry: Tropospheric noise, GPS estimates and implications for interferometric synthetic aperture radar products  

Microsoft Academic Search

Interferometric synthetic aperture radar (INSAR), like other astronomic and space geodetic techniques, is limited by the spatially and temporally variable delay of electromagnetic waves propagating through the neutral atmosphere. Statistical analysis of these variations, from a wide variety of instruments, reveals a power law dependence on frequency that is characteristic of elementary (Kolmogorov) turbulence. A statistical model for a major

Simon Williams; Yehuda Bock; Peng Fang

1998-01-01

160

A new polar Fourier transform for computer-aided tomography and spotlight synthetic aperture radar  

Microsoft Academic Search

An algorithm for calculating the Fourier transform of certain discrete measures supported on a two-dimensional polar grid is described. The algorithm utilizes a modified Bluestein chirp algorithm to directly calculate the Fourier transform values over a rectangular grid. Applications to computer-aided tomography and spotlight synthetic aperture radar are described

Wayne Lawton

1988-01-01

161

Spatial Resolution of Bistatic Synthetic Aperture Radar: Impact of Acquisition Geometry on Imaging Performance  

Microsoft Academic Search

This paper analyzes the spatial resolution of bistatic synthetic aperture radar (SAR) in general hybrid configurations, such as air- and spaceborne systems moving along independent trajectories. The gradient method is utilized to point out the effects of the acquisition geometry, namely, position and velocity of both the transmitter and the receiver, on image resolution. This general approach is applied to

Antonio Moccia; Alfredo Renga

2011-01-01

162

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

Microsoft Academic Search

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

John A. Richards; JOHN A

2002-01-01

163

Resolution Enhancement for Inversed Synthetic Aperture Radar Imaging Under Low SNR via Improved Compressive Sensing  

Microsoft Academic Search

The theory of compressed sampling (CS) indicates that exact recovery of an unknown sparse signal can be achieved from very limited samples. For inversed synthetic aperture radar (ISAR), the image of a target is usually constructed by strong scattering centers whose number is much smaller than that of pixels of an image plane. This sparsity of the ISAR signal intrinsically

Lei Zhang; Mengdao Xing; Cheng-Wei Qiu; Jun Li; Jialian Sheng; Yachao Li; Zheng Bao

2010-01-01

164

A Multiple Beam Synthetic Aperture Radar Design Concept for Geoscience Applications  

Microsoft Academic Search

The multiple beam synthetic aperture radar (SAR) has been presented as a superior alternative to conventional side-looking SAR designs for mapping earth resources from space. The multiple beam approach provides wide swath coverage at nearly constant incident angle while conserving peak power. These desirable system characteristics, however, are realized at the expense of additional signal processing. A design example illustrates

Buford R. Jean; John W. Rouse

1983-01-01

165

Automatic ship classification system for inverse synthetic aperture radar (ISAR) imagery  

Microsoft Academic Search

The U.S. Navy has been interested in applying neural network processing architectures to automatically determine the naval class of ships from an inverse synthetic aperture radar (ISAR) on-board an airborne surveillance platform. Currently an operator identifies the target based on an ISAR display. The emergence of the littoral warfare scenario, coupled with the addition of multiple sensors on the platform,

Murali M. Menon

1995-01-01

166

Comments on optical transfer function techniques and SAR (Synthetic Aperture Radar) imaging  

Microsoft Academic Search

Optical transfer function techniques are reviewed and applied to the problem of analyzing and specifying synthetic aperture radar (SAR) image quality. Integrated side lobe ratio is compared to similar optical measurements. The effect of pulse repetition frequency (PRF) on non-coherent transfer functions is discussed. Non-coherent and coherent transfer functions are discussed.

Niels Jensen

1986-01-01

167

Exploitation of target shadows in synthetic aperture radar imagery for automatic target recognition  

Microsoft Academic Search

The utility of target shadows for automatic target recognition (ATR) in synthetic aperture radar (SAR) imagery is investigated. Although target shadow, when available, is not a powerful target discriminating feature, it can effectively increase the overall accuracy of the target classification when it is combined with other target discriminating features such as peaks, edges, and corners. A second and more

John A. Saghri; Andrew DeKelaita

2006-01-01

168

A Performance Complexity Study of Several Approaches to Automatic Target Recognition from Synthetic Aperture Radar Images  

Microsoft Academic Search

A framework which allows for the direct comparison of alternate approaches to automatic target recogni- tion (ATR) from synthetic aperture radar (SAR) images is described and applied to variants of several ATR algorithms. This framework allows comparisons to be made on an even footing while minimizing the impact of implementation details and accounts for variation in image sizes, in angular

Michael D. DeVore; Joseph A. O'Sullivan

1999-01-01

169

Automatic Target Recognition in Synthetic Aperture Radar image using multiresolution analysis and classifiers combination  

Microsoft Academic Search

Automatic target recognition (ATR) is an important capability for defense application. ATR removes the human operator from the process of target acquisition and classification, reducing the reaction time to possible threats and can be used to gun target engagement. This paper presents one technique used to solve the automatic target recognition problem in synthetic aperture radars (SAR) images, that is

João Paulo Pordeus Gomes; José Fernando Basso Brancalion; David Fernandes

2008-01-01

170

Applications of Synthetic Aperture Radar to Meteorology and Oceanography Command Operations.  

National Technical Information Service (NTIS)

Our long-term goal is to employ synthetic aperture radar (SAR) imagery of the sea surface as a marine meteorological research and forecasting tool. That is, we aim to use SAR to discover dynamical and morphological characteristics of microscale, mesoscale...

G. S. Young N. S. Winstead T. D. Sikora

2007-01-01

171

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

172

Complex Wishart Distribution Based Analysis of Polarimetric Synthetic Aperture Radar Data  

Microsoft Academic Search

Multi-look, polarimetric synthetic aperture radar (SAR) data are often worked with in the so-called covariance matrix representation. For each pixel this representation gives a 3 times 3 Hermitian, positive definite matrix which follows a complex Wishart distribution. Based on this distribution a test statistic for equality of two such matrices and an associated asymptotic probability for obtaining a smaller value

Allan A. Nielsen; H. Skriver; K. Conradsen

2007-01-01

173

Analysis of Data Acquired by Synthetic Aperture Radar over Dade County, Florida, and Acadia Parish, Louisiana.  

National Technical Information Service (NTIS)

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 estima...

S. T. Wu

1983-01-01

174

Persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis, with application to Volcán Alcedo, Galápagos  

Microsoft Academic Search

While conventional interferometric synthetic aperture radar (InSAR) is a very effective technique for measuring crustal deformation, almost any interferogram includes large areas where the signals decorrelate and no measurement is possible. Persistent scatterer (PS) InSAR overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. Existing PS methods have

A. Hooper; P. Segall; H. Zebker

2007-01-01

175

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

Microsoft Academic Search

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

Pablo Clemente-Colon

2002-01-01

176

The SIR-C\\/X-SAR synthetic aperture radar system  

Microsoft Academic Search

SIR-C\\/X-SAR, a three-frequency radar to be flown on the Space Shuttle in September 1993, is described. The SIR-C system is a two-frequency radar operating at 1250 MHz (L-band) and 5300 MHz (C-band), and is designed to get four-polarization radar imagery at multiple surface angles. The X-SAR system is an X-band imaging radar operating at 9600 MHz. The discussion covers the

Rolando L. Jordan; Bryan L. Huneycutt; Marian Werner

1991-01-01

177

Waveform error analysis for bistatic synthetic aperture radar systems  

Microsoft Academic Search

The signal phase histories at the transmitter, receiver, and radar signal processor in bistatic SAR systems are described. The fundamental problem of mismatches in the waveform generators for the illuminating and receiving radar systems is analyzed. The effects of errors in carrier frequency and chirp slope are analyzed for bistatic radar systems which use linear FM waveforms. It is shown

J. W. Adams; T. M. Schifani

1987-01-01

178

Special Issue on Results from Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (Sir-C/X-SAR): Foreword  

NASA Technical Reports Server (NTRS)

The two flights of the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR) aboard the Space Shuttle Endeavour represent a major advance in remote sensing technology for studies of planetary surfaces.

Plaut, Jefferey J.

1996-01-01

179

Estimating X-band synthetic aperture radar detection of objects obscured by foliage using the DSTO Ingara airborne imaging radar  

Microsoft Academic Search

Estimating the Probability of Detection (Pd) of synthetic aperture radar (SAR) imagery of foliage-obscured objects requires a knowledge of the object backscatter and the obscuration properties of the foliage. At X-band frequencies minimal penetration of the foliage occurs and as such the assumption that the object is visible only through gaps in the foliage can be made. Given this assumption

B. G. Hobbs; N. J. S. Stacy

2001-01-01

180

Observations of Hurricane Bonnie in spaceborne synthetic aperture radar (SAR) and next-generation Doppler weather radar (NEXRAD)  

Microsoft Academic Search

Atmospheric circulation systems have being shown to produce observable signatures on spaceborne synthetic aperture radar (SAR) imagery of the ocean surface. Capillary and small gravity ocean waves of roughly the scale of the SAR electromagnetic wavelength, the so-called Bragg waves, provide the surface roughness that allows for SAR mapping of both ocean and atmospheric mesoscale features. Two RADARSAT SAR images

Pablo Clemente-Colon; Peter C. Manousos; William G. Pichel; Karen Friedman

1999-01-01

181

The SIR-C/X-SAR synthetic aperture radar system  

NASA Technical Reports Server (NTRS)

SIR-C/X-SAR, a three-frequency radar to be flown on the Space Shuttle in September 1993, is described. The SIR-C system is a two-frequency radar operating at 1250 MHz (L-band) and 5300 MHz (C-band), and is designed to get four-polarization radar imagery at multiple surface angles. The X-SAR system is an X-band imaging radar operating at 9600 MHz. The discussion covers the mission concept; system design; hardware; RF electronics; digital electronics; command, timing, and telemetry; and testing.

Jordan, Rolando L.; Huneycutt, Bryan L.; Werner, Marian

1991-01-01

182

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

PubMed

We 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. PMID:18276222

Webb, J H; Munson, D R; Stacy, N S

1998-01-01

183

Crop classification from airborne synthetic aperture radar data  

Microsoft Academic Search

The ability of radar systems to record useful data independently of the prevailing weather conditions and the future increase in radar data availability is likely to result in their increased utilization for crop classification. However, a variety of factors relating to the quantity and quality of the data will influence the accuracy with which these data can be classified. This

G. M. FOODY

1988-01-01

184

Dismount feature extraction from circular synthetic aperture radar data  

Microsoft Academic Search

Recently, the use of micro-Doppler radar signatures for classification has become an area of focus, in particular for the case of dynamic targets where many components are interacting over time. One specific target of interest is the dismount. Dismount detection, feature extraction, and classification offers some unique challenges. For instance, humans have small radar cross-sections and slow range-rates making discrimination

Orelle R. Fogle; Brian D. Rigling

2012-01-01

185

Three-dimensional holographic data processing and wavelength readout for range-doppler-angle radar, and synthetic-aperture radar  

NASA Astrophysics Data System (ADS)

The utilization of three dimensions of parallelism in photorefractive data processors is extended to parallel three- dimensional readout for the two radar scenarios of radar doppler and ranging processing, and 3D synthetic aperture radar. These are scenarios in which the data processing has full parallelism in all of three dimensions, making the volume holographic approach attractive. The result of this processing gives us a surface with the third dimension coded with the wavelength and the value represented by the intensity so that the three dimensions of data may be read out in parallel with the use of a three-color CCD.

Weverka, Robert T.; Wagner, Kelvin H.; Sarto, Anthony W.; Weaver, Samuel P.

1994-06-01

186

User guide to the Magellan synthetic aperture radar images  

NASA Technical Reports Server (NTRS)

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.

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

1995-01-01

187

Synthetic aperture radar (SAR) image focus performance during maneuvers  

NASA Astrophysics Data System (ADS)

Focus of a SAR image during maneuvers requires accurate estimates of the aircraft velocity vector. Velocity errors particularly along the radar line of sight (LOS) to the SAR map center cause LOS acceleration errors during an aircraft maneuver. This LOS acceleration results in defocused SAR images. Sensitivity to acceleration errors is greatest when mapping at small squint angles with respect to the aircraft velocity vector, i.e., at small angles with respect to the aircraft fore-aft axis. This paper shows the expected SAR map focus performance during maneuvers as a function of velocity errors. Simulation results showing expected focus performance using current and advanced processing techniques with background radar Doppler updates and with the use of Global Positioning System (GPS) are presented. With GPS aiding, velocity accuracy is improved by a factor of ten. The simulation results are compared to the flight test results performed with the APG-76 radar using both a gimbaled and a strapdown one nautical mile per hour class Inertial Navigation System with and without GPS aiding. The AN/APG-76 is a SAR radar with simultaneous Ground Moving Target Indication and is designed for `near the nose' imaging during aircraft maneuvers.

Ibsen, Paul M.; Guarino, Robert

1996-06-01

188

Synthetic aperture radar (SAR) image focus performance during maneuvers  

Microsoft Academic Search

Focus of a SAR image during maneuvers requires accurate estimates of the aircraft velocity vector. Velocity errors particularly along the radar line of sight (LOS) to the SAR map center cause LOS acceleration errors during an aircraft maneuver. This LOS acceleration results in defocused SAR images. Sensitivity to acceleration errors is greatest when mapping at small squint angles with respect

Paul M. Ibsen; Robert Guarino

1996-01-01

189

Study of Synthetic Aperture Radar (SAR) imagery characteristics  

NASA Technical Reports Server (NTRS)

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.

1975-01-01

190

A Synthetic Aperture Radar (SAR) for commercial applications  

Microsoft Academic Search

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

B. L. Bullock; A. Kozma

1985-01-01

191

Quantization noise in digital signal processing by harmonic analysis in a synthetic-aperture radar  

Microsoft Academic Search

The paper derives and analyzes expressions for assessing the effect of quantization noise arising in digital signal processing by harmonic analysis in a synthetic-aperture radar on the output signal for an arbitrary weight function in an FFT processor. The output signal-to-noise ratio is shown to depend on the FFT base size, the digit-representation length in the processing system, and the

N. A. Sazonov

1985-01-01

192

Mapping Ocean Surface Topography with a Synthetic-Aperture Interferometry Radar  

NASA Technical Reports Server (NTRS)

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.

Fu, Lee-Lueng; Rodriguez, Ernesto

2006-01-01

193

Investigating landslides with space-borne Synthetic Aperture Radar (SAR) interferometry  

Microsoft Academic Search

This paper is addressed to readers without advanced knowledge of remote sensing. It illustrates some current and potential uses of satellite Synthetic Aperture Radar interferometry (InSAR) for landslide assessment. Data acquired by SAR systems can provide 3D terrain models and be used to assist in regional scale investigations, e.g. aimed at evaluation of susceptibility of slopes to failure. Under favourable

Carlo Colesanti; Janusz Wasowski

2006-01-01

194

Global digital topography mapping with a synthetic aperture scanning radar altimeter  

NASA Technical Reports Server (NTRS)

Global digital topography data of the land surface is of importance in a variety of geoscientific and application disciplines. Such a database, with a spatial resolution of 150 to 500 m and height accuracy of 5 m or better can be acquired from an orbiting platform using a synthetic aperture scanning radar altimeter. Near-global coverage can be achieved within 14 days from an orbiting platform in a polar or near-polar orbit.

Elachi, C.; Im, K. E.; Rodriguez, E.

1990-01-01

195

A beamforming approach to stepped-frequency synthetic aperture through-the-wall radar imaging  

Microsoft Academic Search

A data-adaptive stepped-frequency synthetic aperture radar system based on quadratically constrained Capon beamforming is presented for through-the-wall wideband microwave imaging applications. Various effects of the presence of the wall, such as refraction, change in speed, and attenuation, are incorporated into the beamformer design. Proof of concept is provided using real data collected in a laboratory environment. The results show that

Fauzia Ahmad; Moeness G. Amin; Saleem A. Kassam

2005-01-01

196

Atmospheric boundary layer rolls observed by the synthetic aperture radar aboard the ERS-1 satellite  

Microsoft Academic Search

Two synthetic aperture radar (SAR) images acquire by the European Remote Sensing Satellite ERS-1 over the Jade-Weser estuary in the German Bight of the North Sea on January 2 and 20, 1992, are analyzed. The images show sea surface manifestations of atmospheric boundary layer rolls. This is inferred from the orientation of the quasi-periodic sea surface patterns which are aligned

W. Alpers; B. Brümmer

1994-01-01

197

Strapdown inertial measurement units for motion compensation for synthetic aperture radars  

Microsoft Academic Search

It is shown that synthetic-aperture radar (SAR) motion can be compensated by using an antenna-mounted strapdown inertial measurement unit (IMU) as the motion sensing system, but sensor and system errors affect SAR image quality. A strapdown IMU consists of three accelerator channels and three gyro channels. Strapdown IMU errors include gyro-scale and accelerometer-scale factor and bias errors, velocity error, platform

Thomas A. Kennedy

1988-01-01

198

Fault creep along the southern San Andreas from interferometric synthetic aperture radar, permanent scatterers, and stacking  

Microsoft Academic Search

Interferometric synthetic aperture radar (InSAR) provides a practical means of mapping creep along major strike-slip faults. The small amplitude of the creep signal (<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

Suzanne Lyons; David Sandwell

2003-01-01

199

Synthetic aperture radar images of ocean waves, theories of imaging physics and experimental tests  

NASA Technical Reports Server (NTRS)

The physical mechanism for the synthetic Aperture Radar (SAR) imaging of ocean waves is investigated through the use of analytical models. The models are tested by comparison with data sets from the SEASAT mission and airborne SAR's. Dominant ocean wavelengths from SAR estimates are biased towards longer wavelengths. The quasispecular scattering mechanism agrees with experimental data. The Doppler shift for ship wakes is that of the mean sea surface.

Vesecky, J. F.; Durden, S. L.; Smith, M. P.; Napolitano, D. A.

1984-01-01

200

Interpretation of a SAR (Synthetic Aperture Radar) image of the Bay of Biscay  

Microsoft Academic Search

On August 20, 1978, the Synthetic Aperture Radar (SAR) on board the satellite SEASAT, gave evidence of high energy internal oceanic activity at the shelfbreak in the northern part of the Bay of Biscay. Quantitive spatial measurements of internal wave patterns were correlated with conventional, quasi-synoptic in situ data and yielded phase speeds of 0.55M\\/S for high frequency, nonlinear internal

J. F. Soubrier

1983-01-01

201

Comparison of real-time acousto-optic SAR (synthetic aperture radar) processor architectures  

Microsoft Academic Search

A comparison of real-time acousto-optic processors for synthetic aperture radar (SAR) image formation has been performed. These processors take advantage of the high processing speed and large time bandwidth product of acousto-optic devices (AOD's) in combination with the multichannel correlation capability of charge coupled devices (CCD) to form the SAR image in real time. They offer significant size, weight and

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

1987-01-01

202

Airborne C-SAR (Synthetic Aperture Radar) real-time imaging system  

Microsoft Academic Search

This paper presents the design of one real-time imaging system in airborne C-band Synthetic Aperture Radar. The real-time imaging algorithm based on subaperture-division is described in detail. In order to meet real-time signal processing the signal processing board with 8 ADSP-TS201S digital signal processors and 2GB SDRAM is designed. This system has excellent real-time processing ability and tremendous data throughput

Liu Jing; Wu Jing-wei; Wang Zhi-rui; Hu Qing-rong

2007-01-01

203

SPATIALLY ADAPTIVE DESPECKLING FOR MULTI-LOOK POLARIMETRIC SYNTHETIC APERTURE RADAR IMAGERY  

Microsoft Academic Search

A spatially adaptive speckle filtering approach for multi-look polarimetric synthetic aperture radar imagery is presented. The central idea of the proposed filter is that the filtering operations are performed spatially variant for image features, i.e. edges, lines and point-like textural features, in order to preserve them. For homogeneous areas, the filtering is based on scattering properties. To achieve this, edge

Ken Yoong LEE; Timo Rolf BRETSCHNEIDER

204

Mission analysis and design of a bistatic synthetic aperture radar on board a small satellite  

Microsoft Academic Search

This paper is aimed at a feasibility study of a new space-based observation technique: bistatic synthetic aperture radar, e.g. an active microwave sensor operating with separated transmitting and receiving antennae. Assuming ESA ENVISAT ASAR as main mission, a small satellite (BISSAT) equipped with a receiving-only antenna and flying in formation with ENVISAT is studied in details. In addition to conventional

Antonio Moccia; Sergio Vetrella; Roberta Bertoni

2000-01-01

205

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

Microsoft Academic Search

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

C. J. Read; D. V. Arnold; D. M. Chabries; P. L. Jackson; R. W. Christiansen

1988-01-01

206

An R and D model of a synthetic aperture radar antenna  

NASA Technical Reports Server (NTRS)

The test results of an R and D model of Synthetic Aperture Radar Antenna (SARA) for ERS-1 (Japanese Earth Resources Satellite-1) are summarized. Critical structural and mechanical components test, electrical performance test, deployment test and thermal deformation tests were performed and an environmental tests model was developed. The deployment test, thermal deformation test and 128 element tests (one of the electrical tests) indicate that the model meets expectations.

Imura, N.; Akaishi, A.; Ono, M.; Hisada, Y.; Itoh, Y.

1984-01-01

207

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

NASA Astrophysics Data System (ADS)

Flooding is a particular hazard in urban areas worldwide due to the increased risks to life and property in these regions. Synthetic Aperture Radar (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.

Mason, D. C.; Giustarini, L.; Garcia-Pintado, J.; Cloke, H. L.

2014-05-01

208

Information extraction and transmission techniques for spaceborne synthetic aperture radar images  

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

209

Measuring the thermodynamic state of sea ice using synthetic aperture radar (SAR) time series data  

Microsoft Academic Search

The study of atmosphere-sea ice-ocean processes using synthetic aperture radar (SAR) endeavors to improve estimates of energy flows and climate state variables from seasonally dynamic Arctic sea ice. This paper works toward this goal by characterizing the seasonal coevolution of the thermodynamic, electrical, brine volume, mechanical and microwave scattering characteristics of a snow covered landfast first-year (FY) sea ice volume

J. J. Yackel; D. G. Barber

1998-01-01

210

Tutorial review of synthetic-aperture radar (SAR) with applications to imaging of the ocean surface  

Microsoft Academic Search

A synthetic aperture radar (SAR) can produce high-resolution two-dimensional images of mapped areas. The SAR comprises a pulsed transmitter, an antenna, and a phase-coherent receiver. The SAR is borne by a constant velocity vehicle such as an aircraft or satellite, with the antenna beam axis oriented obliquely to the velocity vector. The image plane is defined by the velocity vector

KIYO TOMIYASU

1978-01-01

211

Synthetic Aperture Radar moving target indication processing of along-track monopulse nonlinear gotcha data  

Microsoft Academic Search

This paper is concerned with imaging and moving target detection using a synthetic aperture radar (SAR) platform that is known as Gotcha. The SAR platform can interrogate a scene using an imperfect circular trajectory; we refer to this as nonlinear SAR data collection. This collection can make monostatic and quasi-monostatic measurements in the along-track domain. We present subaperture-based wavefront reconstruction

Uttam Majumder; Mehrdad Soumekh; Michael Minardi; Steven Scarborough; LeRoy Gorham; Curtis Casteel; Matthew Judge; John Kirk

2009-01-01

212

The NASA/JPL Airborne Synthetic Aperture Radar System  

NASA Technical Reports Server (NTRS)

The NASA/JPL airborne SAR (AIRSAR) system operates in the fully polarimetric mode at P-, L- and C-band simultaneously or in the interferometric mode in both L- and C-band simultaneously. The system became operational in late 1987 and flew its first mission aboard a DC-8 aircraft operated by NASA's Ames Research Center in Mountain View, California. Since then, the AIRSAR has flown missions every year and acquired images in North, Central and South America, Europe and Australia. In this paper, we will briefly describe the instrument characteristics, the evolution of the various radar modes, the instrument performance, and improvement in the knowledge of the positioning and attitude information of the radar. In addition, we will summarize the progress of the data processing effort especially in the interferometry processing. Finally, we will address the issue of processing and calibrating the cross-track interferometry (XTI) data.

Kim, Yun-Jin; Lou, Yun-Ling; vanZyl, Jakob

1996-01-01

213

Hyperbola summation based synthetic aperture radar technique for ground penetrating radar image focusing  

Microsoft Academic Search

Ground-penetrating radar (GPR) is a remote sensing technique used to obtain information on subsurface features from data collected over the surface. The process of collecting data may be viewed as mapping from the object space to an image space. Since most GPRs use broad beamwidth antennas, the energy reflected from a buried structure is recorded over a large lateral aperture

Shrikant Sharma; Paramananda Jena; Ramachandra Kuloor

2012-01-01

214

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

NASA Technical Reports Server (NTRS)

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.

Zawadzki, Mark; Huang, John

1999-01-01

215

Salient Feature Identification and Analysis using Kernel-Based Classification Techniques for Synthetic Aperture Radar Automatic Target Recognition.  

National Technical Information Service (NTIS)

An investigation into feature saliency for application to synthetic aperture radar (SAR) automatic target recognition (ATR) is presented. Specifically, research is focused on improving the SAR binary classi cation performance aspect of ATR, or the ability...

M. S. Flynn

2014-01-01

216

Doppler Aliasing Reduction in Wide-Angle Synthetic Aperture Radar Using Phase Modulated Random Stepped-Frequency Waveforms.  

National Technical Information Service (NTIS)

This research investigates the benefits of using several phase modulated Random Stepped Frequency (RSF) waveforms in a Wide-Angle Synthetic Aperture Radar (WA-SAR) scenario. RSF waveforms have been demonstrated to have desirable properties which allow for...

A. W. Hyatt

2006-01-01

217

Doppler Aliasing Reduction in Wide-Angle Synthetic Aperture Radar Using a Linear Frequency Modulated Random Stepped-Frequency Waveform.  

National Technical Information Service (NTIS)

This research examines the theory, application, and results of using Random Stepped-Frequency (RSF) waveforms to mitigate Doppler aliasing in a wide- angle Synthetic Aperture Radar (SAR) imaging scenario. Severe Doppler aliasing typically occurs in this s...

J. McMahon

2005-01-01

218

Modeling Collapse Chimney and Spall Zone Settlement as a Source of Post- Shot Subsidence Detected by Synthetic Aperture Radar Interferometry.  

National Technical Information Service (NTIS)

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 (V...

W. Foxall

2000-01-01

219

Inversion of Synthetic Aperture Radar Interferograms for Sources of Production-Related Subsidence at the Dixie Valley Geothermal Field.  

National Technical Information Service (NTIS)

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, ...

B. Foxall D. Vasco

2003-01-01

220

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

NASA Technical Reports Server (NTRS)

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.

Li, Jian

1994-01-01

221

Estimating Titan Surface Topography from Cassini Synthetic Aperture RADAR Data  

NASA Astrophysics Data System (ADS)

One of the more vexing dilemmas for RADAR remote sensing is the necessity to choose between altimetry and SAR imaging of a surface. Coincident surface height estimates are very useful in aiding the analysis of the unique surface features observed in the SAR imagery of Titan. Radar altimetry is optimally obtained from nadir observations, whereas SAR requires off-nadir observation in order to construct an image. Co-located nadir altimetry and SAR only occur when observations taken at different times happen to overlap. Stereo techniques can also be used to estimate topography in SAR images, but they also require multiple overlapping observations. Here we discuss a technique, SARTopo, for obtaining 10 km horizontal resolution and 75 m vertical resolution surface height estimates along each SAR swath. The height estimates comprise 1-3 cuts in each SAR pass that are 10 km wide by thousands of km long and extend along the entire long dimension of the SAR image strips. Because we obtain co-located topography along each SAR pass rather than only in regions with overlapping observations, the new technique extends the area over which we have colocated topography and SAR imagery by a couple orders of magnitude. The method is based upon Amplitude Monopulse Comparison, a technique for resolving RADAR targets developed prior to the advent of SAR. The technique requires: 1) accurate spacecraft pointing, 2) accurate spacecraft ephemeris, 3) precise knowledge of the antenna pattern of the RADAR, and 4) downlinked echo data covering the entire antenna footprint. The fourth requirement is met through synergy with Cassini SAR coverage requirements. Cassini SAR commanding and pointing is designed to utilize as much of the antenna footprint as possible in order to maximize cross-track coverage. We describe the technique and present the results for several SAR passes. We validate the technique through comparison with known features such as mountain ranges and dry lakes, and by comparison with colocated nadir altimetry and SAR stereo. In particular, we examine a strip of nadir altimetry obtained along a 1000 km strip observed by SAR a month earlier. The SARTopo height track is within 5-10 km of the nadir altimetry track for a 200 km long section. In this area, the two independent techniques agree closely. Furthermore the region contains prominent high spatial resolution topography, so it provides an excellent test of the resolution and accuracy of both techniques. SARTopo heights are also co-located and agree well with SAR stereo observations. The research described here was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.

Stiles, B. W.; Hensley, S.; Gim, Y.; Kirk, R. L.; Zebker, H. A.; Janssen, M. A.; Johnson, W. T.; West, R. D.

2007-12-01

222

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

NASA Technical Reports Server (NTRS)

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.

Werner, Marian U.

1993-01-01

223

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

NASA Technical Reports Server (NTRS)

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.

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

1992-01-01

224

The Earth Observing System (EOS) synthetic aperture radar (SAR)  

NASA Technical Reports Server (NTRS)

The evolution of the Spaceborne Imaging Radar (SIR) has led to a multipolarization, multifrequency SAR with variable imaging geometry which will be ready for flight on the Space Station Earth Observing System (EOS). Nominally, this SAR will be a three-frequency (L-, C-, and X-band) system with quad polarization available for the L and C bands. It will be capable of acquiring multiincidence-angle data using electronic beam steering, and other imaging geometries by mechanically pitching, yawing, and rolling the antenna. The capabilities of the EOS SAR, particularly acquisition of cross-polarized and high-incidence-angle data, depend on the altitude of the platform on which the SAR flies and improve significantly at lower altitudes. The EOS SAR will provide a unique new data set and will play a key role in understanding the earth's global processes, alone and synergistically with other EOS instruments.

Cimino, Jobea; Held, Dan

1986-01-01

225

Multiple feature-enhanced synthetic aperture radar imaging  

NASA Astrophysics Data System (ADS)

Non-quadratic regularization based image formation is a recently proposed framework for feature-enhanced radar imaging. Specific image formation techniques in this framework have so far focused on enhancing one type of feature, such as strong point scatterers, or smooth regions. However, many scenes contain a number of such features. We develop an image formation technique that simultaneously enhances multiple types of features by posing the problem as one of sparse signal representation based on overcomplete dictionaries. Due to the complex-valued nature of the reflectivities in SAR, our new approach is designed to sparsely represent the magnitude of the complex-valued scattered field in terms of multiple features, which turns the image reconstruction problem into a joint optimization problem over the representation of the magnitude and the phase of the underlying field reflectivities. We formulate the mathematical framework needed for this method and propose an iterative solution for the corresponding joint optimization problem. We demonstrate the effectiveness of this approach on various SAR images.

Samadi, Sadegh; Çetin, Müjdat; Masnadi-Shirazi, Mohammad Ali

2009-05-01

226

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

NASA Technical Reports Server (NTRS)

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.

Montgomery, Donald R. (Editor)

1996-01-01

227

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)

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.

Mehlis, J. G.

1976-01-01

228

Fast ISAR (Inverse Synthetic Aperture Radar)-Imaging Process and Its Inherent Degrading Effects on Image Quality.  

National Technical Information Service (NTIS)

A method for a fast two-dimensional inverse synthetic aperture radar (ISAR) imaging process is presented. A coherent short pulse radar is used to sample amplitude and phase of the backscattered field from a continuously rotating object. This is being done...

K. H. Bethke B. Roede

1989-01-01

229

X-SAR: The German/Italian Contribution to Realizing a Multifrequency Synthetic Aperture Radar for Remote Sensing from Space.  

National Technical Information Service (NTIS)

X-SAR is a Shuttle Borne imaging Synthetic Aperture Radar (SAR) operating in X band (9.6 GHz). It is being developed and operated in a joint venture between Germany and Italy. Integrated together with the L band (1.25 GHz) and C band (5.3 GHz) radar SIR-C...

M. Wahl P. Ammendola H. Oettl P. Pampaloni

1992-01-01

230

Monitoring of the Greenland Ice Sheet using ERS-1 synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

ERS-1 Synthetic Aperture Radar (SAR) imagery is shown to be suitable for monitoring the climate of the Greenland ice sheet and for measuring changes in its marginal position. Four distinct hydrologic zones are easily recognized. Zone boundaries align closely with elevation. Seasonal changes in at least one of these zones indicate that late Winter is a better time than late Summer for the collection of images intended for long term monitoring. Subtle variations of the backscatter intensity from the highest portions of the ice sheet where melting never occurs are believed to indicate surface topography.

Bindschadler, Robert; Fahnestock, Mark; Kwok, Ron

1993-01-01

231

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

DOEpatents

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.

Doerry, Armin W. (Albuquerque, NM); Heard, Freddie E. (Albuquerque, NM); Cordaro, J. Thomas (Albuquerque, NM)

2008-06-24

232

The application of spaceborne synthetic aperture radar in the maritime environment  

NASA Astrophysics Data System (ADS)

The principles of spaceborne Synthetic Aperture Radar (SAR) are given. Its application in the maritime environment is discussed, with reference to several specific systems. The requirement for calibration is discussed. Some of the more advanced techniques expected to be incorporated in future missions are summarized. Spaceborne SAR is a potentially powerful sensor in the maritime environment. Its active nature imparts an all weather, 24 hour imaging capability, limited only by orbit and power supply constraints. It is able to image a variety of ocean phenomena, leading to a range of applications in several fields.

Condley, C. J.

1991-10-01

233

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

NASA Technical Reports Server (NTRS)

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.

Imhoff, Marc L. (inventor)

1991-01-01

234

Delta K measurements with synthetic aperture radar data. [micirowavelength difference values  

NASA Technical Reports Server (NTRS)

Delta K measurements are obtained from the interference of two electromagnetic waves of different frequencies. Constructive interference occurs when 2pi phase differences between the two frequencies correspond to a surface wavelength. Previous Delta K measurements have used two discrete frequencies for this purpose. Range pulses and Doppler signatures of a synthetic aperture radar system were filtered to obtain a sequence of Delta K values. Those Delta K values which correspond to the wavelengths of known surfaces show maximum constructive interference. SAR data can therefore be used for Delta K measurements, indicating the possibility of selective Delta K filtering during data gathering.

Larson, R. W.; Jackson, P. L.; Klooster, A.

1985-01-01

235

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

NASA Technical Reports Server (NTRS)

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.

Wu, C.

1976-01-01

236

A sea surface height estimator using synthetic aperture radar complex imagery  

NASA Technical Reports Server (NTRS)

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.

Harger, R. O.

1983-01-01

237

Synthetic Aperture Radar Interferometry for Digital Elevation Model of Kuwait Desert - Analysis of Errors  

NASA Astrophysics Data System (ADS)

Using different combinations of 29 Advanced Synthetic Aperture Radar (ASAR) images, 43 Digital Elevations Models (DEM) were generated adopting SAR Interferometry (InSAR) technique. Due to sand movement in desert terrain, there is a poor phase correlation between different SAR images. Therefore, suitable methodology for generating DEMs of Kuwait desert terrain using InSAR technique were worked out. Time series analysis was adopted to derive the best DEM out of 43 DEMs. The problems related to phase de-correlation over desert terrain are discussed. Various errors associated with the DEM generation are discussed which include atmospheric effects, penetration into soil medium, sand movement. The DEM of Shuttle Radar Topography Mission (SRTM) is used as a reference. The noise levels of DEM of SRTM are presented.

Jassar, H. K. Al; Rao, K. S.

2012-07-01

238

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

239

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

NASA Technical Reports Server (NTRS)

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.

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

2004-01-01

240

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

SciTech Connect

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.

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

1993-12-31

241

Anisotropic adaptive filtering for speckle reduction in synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

The speckle reduction is an important problem in coherent imaging, such as synthetic aperture radar or ultrasound imagery. Speckle is a nonadditive and nonwhite process, and the reduction of speckle without blurring sharp features is known to be difficult. We present a new speckle reduction algorithm that utilizes an anisotropic directional filter that adapts to the proximity and direction of nearest important features. To remove speckle without blurring important features, the locations and direction of edges in the image are estimated. Then for each pixel in the image, the distance and angle to the nearest edge are computed by an efficient algorithm and stored in distance and angle maps. Finally, for each pixel, an anisotropic directional filter aligned to the nearest edge is applied. The shape and the orientation of the filter are determined from the distance and the angle maps. The new speckle reduction algorithm is tested with both synthesized and real synthetic aperture radar images. The performance of the new algorithm is also compared to those of earlier speckle reduction approaches. We show that the new algorithm performs favorably compared to other speckle reduction algorithms in reducing speckle without blurring important features.

Eom, Kie B.

2011-05-01

242

Invariant triangle-based stationary oil platform detection from multitemporal synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

An automatic algorithm for stationary oil platform detection from multitemporal synthetic aperture radar data is proposed. The proposed algorithm consists of the following two parts. (1) A two-parameter constant false-alarm rate (CFAR) algorithm is used to extract targets from the Environment Satellite (ENVISAT) advanced synthetic aperture radar (ASAR), in which the focus is to determine the appropriate parameters of CFAR, thus ensuring as few as possible false-alarm targets when sea-surface targets are effectively extracted. (2) A simple point cluster matching pattern is proposed based on an invariant triangle rule, by which targets extracted from multitemporal ENVISAT ASAR images are automatically matched for detection of stationary targets (e.g., oil platforms). This invariant triangle rule is that any three moving targets have an extremely low probability of maintaining a relative position in multitemporal images, whereas stationary targets can always maintain a fixed relative position. Even under high noise, this invariant triangle rule can be used to realize the target data matching with high robustness. The experiment shows that the false-alarm rate and the missing rate are relatively low when all the targets are detected. The proposed invariant-triangle-based point cluster matching pattern can conduct effective detection and monitoring of stationary oil platforms.

Cheng, Liang; Yang, Kang; Tong, Lihua; Liu, Yongxue; Li, Manchun

2013-01-01

243

A method to evaluate residual phase error for polar formatted synthetic aperture radar systems  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar systems that use the polar format algorithm are subject to a focused scene size limit inherent to the polar format algorithm. The classic focused scene size limit is determined from the dominant residual range phase error term. Given the many sources of phase error in a synthetic aperture radar, a system designer is interested in how much phase error results from the assumptions made with the polar format algorithm. Autofocus algorithms have limits to the amount and type of phase error that can be corrected. Current methods correct only one or a few terms of the residual phase error. A system designer needs to be able to evaluate the contribution of the residual or uncorrected phase error terms to determine the new focused scene size limit. This paper describes a method to estimate the complete residual phase error, not just one or a few of the dominant residual terms. This method is demonstrated with polar format image formation, but is equally applicable to other image formation algorithms. A benefit for the system designer is that additional correction terms can be added or deleted from the analysis as necessary to evaluate the resulting effect upon image quality.

Musgrove, Cameron; Naething, Richard

2013-05-01

244

Biomass estimation of wetland vegetation in Poyang Lake area using ENVISAT advanced synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

Biomass estimation of wetlands plays a role in understanding dynamic changes of the wetland ecosystem. Poyang Lake is the largest freshwater lake in China, with an area of about 3000 km2. The lake's wetland ecosystem has a significant impact on leveraging China's environmental change. Synthetic aperture radar (SAR) data are a good choice for biomass estimation during rainy and dry seasons in this region. In this paper, we discuss the neural network algorithms (NNAs) to retrieve wetland biomass using the alternating-polarization ENVISAT advanced synthetic aperture radar (ASAR) data. Two field measurements were carried out coinciding with the satellite overpasses through the hydrological cycle in April to November. A radiative transfer model of forest canopy, the Michigan Microwave Canopy Scattering (MIMICS) model, was modified to fit to herbaceous wetland ecosystems. With both ASAR and MIMICS simulations as input data, the NNA-estimated biomass was validated with ground-measured data. This study indicates the capability of NNA combined with a modified MIMICS model to retrieve wetland biomass from SAR imagery. Finally, the overall biomass of Poyang Lake wetland vegetation has been estimated. It reached a level of 1.09×109, 1.86×108, and 9.87×108 kg in April, July, and November 2007, respectively.

Liao, Jingjuan; Shen, Guozhuang; Dong, Lei

2013-01-01

245

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

NASA Technical Reports Server (NTRS)

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.

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

1982-01-01

246

Analysis of airborne synthetic aperture radar waveforms over arctic sea ice  

NASA Astrophysics Data System (ADS)

The sea ice thickness and its changes are one of the biggest uncertainties in the Arctic climate system. To address these uncertainties CryoSat has been launched in 2010. Onboard is the SAR/Interferometric Radar Altimeter (SIRAL) which uses the synthetic aperture radar technique to enhance the resolution along track. The new, improved sampling technique and the resulting changes in the signal shape lead to the question weather a distinction of different sea ice types may be possible. To answer this question we analyze radar altimeter data over the arctic ocean from CryoSats' pre-launch validation campaigns. During these campaigns the Airborne SAR/Interferometric Altimeter System ASIRAS has been operated over different surface regimes what allows for a detailed analysis of the radar waveform shape over different sea ice types. In our study we in particular investigate if the lead detection can be improved and if it is possible to distinguish between first year ice and multi year ice based on the shape of the radar echo waveform alone. We define various parameters to describe the width and strength of the returned radar waveform and select the most appropriate parameters for the surface classification. With a bayesian based method we are able to identify around 80 percent of the waveforms correctly. For the detection of leads we find the widely used threshold method sufficient enough to detect more than 90 % of the leads. However we found that the use of the maximum of the radar echo power as a classification parameter can minimize the rate of false detection compared to the widely used Pulse Peakiness parameter. The possibility to distinguish between different ice types makes it possible to improve the freeboard retrieval and the conversion into sea ice thickness by applying more suitable values for the sea ice density and snow load. More analysis however is required to test the presented method for satellite based altimeters.

Zygmuntowska, Marta; Khvorostovsky, Kirill; Sandven, Stein

2013-04-01

247

Tropical vegetation analysis with Landsat thematic mapper and Canadian synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

To test the synergy between optical and microwave remote sensing data sets for vegetation analysis, a comparison was carried out between the results of vegetation land cover classification using multitemporal landsat thematic mapper (TM) alone, and then in conjunction with a Canadian airborne C-band synthetic aperture radar (SAR) image gathered as part of the South American Radar Experiment (SAREX'92). These data sets cover the Tapajos National Forest area of the Brazilian Amazon (Para State). Occurring within the area are many land use and cover types, including extensive tracts of undistributed humid tropical forest, large pastures, small scale agriculture, abandoned plantations and secondary forest growth on old agricultural fields. The addition of radar backscatter and texture information (HH and VV polarizations) to optical data sets significantly increased the separability of classes. For instance, VV backscatter was much higher in areas of permanent agriculture versus those of smaller rotational fields. However, the complexity of the radar backscatter information requires sophisticated analytical capabilities that are only now in development. The synergistic use of active and passive sensors holds a broad promise of solving some of the analytical needs for the global change and carbon modeling communities that cannot be solved with optical data without intensive field validation and/or extensive multitemporal data sets.

Shimabukuro, Yosio E.; Lawrence, William T.; Ahern, Francis J.

1995-01-01

248

Soil moisture assessments for brown locust Locustana pardalina breeding potential using synthetic aperture radar  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar (SAR) imagery was collected over a brown locust Locustana pardalina outbreak area to estimate soil moisture relevant to egg development. ERS-2/RadarSat overpasses and field studies enabled parameterization of surface roughness, volumetric soil moisture, soil texture, and vegetation cover. Data were analyzed both when the target area was assessed as nonvegetated and when treated as vegetated. For the former, using the integral equation model (IEM) and soil surface data combined with the sensitivity of the IEM to changes in surface roughness introduced an error of ˜±0.06 cm3 cm-3 in volumetric soil moisture. Comparison of the IEM modeling results with backscatter responses from the ERS-2/RadarSat imagery revealed errors as high as ±0.14 cm3 cm-3, mostly due to IEM calibration problems and the impact of vegetation. Two modified versions of the water cloud model (WCM) were parameterized, one based on measurements of vegetation moisture and the other on vegetation biomass. A sensitivity analysis of the resulting model revealed a positive relationship between increases in both vegetation biomass and vegetation moisture and the backscatter responses from the ERS-2 and RadarSat sensors. The WCM was able to explain up to 80% of the variability found when the IEM was used alone.

Crooks, William T. S.; Cheke, Robert A.

2014-01-01

249

Waveform analysis of airborne synthetic aperture radar altimeter over Arctic sea ice  

NASA Astrophysics Data System (ADS)

Sea ice thickness is one of the most sensitive variables in the Arctic climate system. In order to quantify changes in sea ice thickness, CryoSat was launched in 2010 carrying a Ku-band Radar Altimeter (SIRAL) designed to measure sea ice freeboard with a few centimeters accuracy. The instrument uses the synthetic aperture radar technique providing signals with a resolution of about 300 m along track. In this study, airborne Ku-band radar altimeter data over different sea ice types has been analyzed. A set of parameters has been defined to characterize the difference in strength and width of the returned power waveforms. With a Bayesian based method it is possible to classify about 80% of the waveforms by three parameters: maximum of the returned power echo, the trailing edge width and pulse peakiness. Furthermore, the radar power echo maximum can be used to minimize the rate of false detection of leads compared to the widely used Pulse Peakiness parameter. The possibility to distinguish between different ice types and open water allows to improve the freeboard retrieval and the conversion into sea ice thickness where surface type dependent values for the sea ice density and snow load can be used.

Zygmuntowska, M.; Khvorostovsky, K.; Helm, V.; Sandven, S.

2013-03-01

250

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

NASA Astrophysics Data System (ADS)

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.

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

2011-02-01

251

Signal processing techniques for forward imaging using ultrawideband synthetic aperture radar  

NASA Astrophysics Data System (ADS)

The U.S. Army Research Laboratory (ARL), as part of a customer and mission-funded exploratory development program, has been developing a prototype of low-frequency, ultra-wideband (UWB) forward-imaging synthetic aperture radar (SAR) to support the U.S. Army's vision for increased mobility and survivability of unmanned ground vehicle missions. The ability of the UWB radar technology to detect objects under foilage could provide an important obstacle-avoidance capability for robotic vehicles, which could improve the speed and maneuverability of these vehicles and consequently increase the survivability of the U.S. forces. In a recent experiment at Aberdeen Proving Ground (APG), we exercised the UWB SAR radar in forward-looking mode and collected data to support the investigation. This paper discusses the signal processing algorithms and techniques that we developed and applied to the recent UWB SAR forward-looking data. The algorithms include motion data processing, self-interference signal (SIR) removal, radio frequency interference (RFI) signal removal, forward-looking image formation, and visualization techniques. We present forward-loking SAR imagery and also volumetric imagery of some targets.

Nguyen, Lam H.; Ton, Tuan T.; Wong, David C.; Ressler, Marc A.

2003-09-01

252

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

SciTech Connect

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.

Falco, T.; Francis, F.; Lovejoy, S. [McGill Univ., Montreal, Quebec (Canada). Physics Dept.] [McGill Univ., Montreal, Quebec (Canada). Physics Dept.; Schertzer, D. [Univ. Pierre et Marie Curie, Paris (France). Lab. de Meteorologie Dynamique] [Univ. Pierre et Marie Curie, Paris (France). Lab. de Meteorologie Dynamique; Kerman, B. [Atmospheric Environment Service, Burlington, Ontario (Canada)] [Atmospheric Environment Service, Burlington, Ontario (Canada); Drinkwater, M. [Jet Propulsion Lab., Pasadena, CA (United States)] [Jet Propulsion Lab., Pasadena, CA (United States)

1996-07-01

253

Sensitivity of C-band Synthetic Aperture RADAR to field-scale soil surface parameters  

NASA Astrophysics Data System (ADS)

This thesis investigates the sensitivity of polarimetric variables from C-band Synthetic Aperture RADAR to near-surface soil moisture (6 cm), micro-topographical surface roughness, and biomass cover, during pre/seed and post-harvest over agricultural fields. Variables examined include: the like-polarized and cross-polarized linear intensity channels; polarization ratios; the Total Power signal; the co-polarized phase difference and co-polarized complex correlation coefficient; Pedestal Height; extrema of the completely polarized and unpolarized components; extrema of the received power and scattered intensity; and the polarization coefficient of variation. Classification of scattering mechanisms with the Cloude-Pottier and Freeman-Durden decompositions are also examined. The empirical relationships between RADAR variables and surface parameters are first analyzed using data collected during field-validation campaigns. Secondly, RADAR imagery is integrated over the watershed scale to assess the operational discrimination of tillage practices with these polarimetric variables and decompositions. Overall results provide an enhanced theoretical understanding of these variables and decompositions for agricultural target retrievals and demonstrate promise for use in an agricultural monitoring scheme.

Adams, Justin

254

Waveform classification of airborne synthetic aperture radar altimeter over Arctic sea ice  

NASA Astrophysics Data System (ADS)

Sea ice thickness is one of the most sensitive variables in the Arctic climate system. In order to quantify changes in sea ice thickness, CryoSat-2 was launched in 2010 carrying a Ku-band radar altimeter (SIRAL) designed to measure sea ice freeboard with a few centimeters accuracy. The instrument uses the synthetic aperture radar technique providing signals with a resolution of about 300 m along track. In this study, airborne Ku-band radar altimeter data over different sea ice types have been analyzed. A set of parameters has been defined to characterize the differences in strength and width of the returned power waveforms. With a Bayesian-based method, it is possible to classify about 80% of the waveforms from three parameters: maximum of the returned power waveform, the trailing edge width and pulse peakiness. Furthermore, the maximum of the power waveform can be used to reduce the number of false detections of leads, compared to the widely used pulse peakiness parameter. For the pulse peakiness the false classification rate is 12.6% while for the power maximum it is reduced to 6.5%. The ability to distinguish between different ice types and leads allows us to improve the freeboard retrieval and the conversion from freeboard into sea ice thickness, where surface type dependent values for the sea ice density and snow load can be used.

Zygmuntowska, M.; Khvorostovsky, K.; Helm, V.; Sandven, S.

2013-08-01

255

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

SciTech Connect

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).

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

1994-05-01

256

Flexible end-to-end system design for synthetic aperture radar applications  

NASA Astrophysics Data System (ADS)

This paper presents ARTEMIS, Inc.'s approach to development of end-to-end synthetic aperture radar systems for multiple applications and platforms. The flexible design of the radar and the image processing tools facilitates their inclusion in a variety of application-specific end-to-end systems. Any given application comes with certain requirements that must be met in order to achieve success. A concept of operation is defined which states how the technology is used to meet the requirements of the application. This drives the design decisions. Key to adapting our system to multiple applications is the flexible SlimSAR radar system, which is programmable on-the-fly to meet the imaging requirements of a wide range of altitudes, swath-widths, and platform velocities. The processing software can be used for real-time imagery production or post-flight processing. The ground station is adaptable, and the radar controls can be run by an operator on the ground, on-board the aircraft, or even automated as part of the aircraft autopilot controls. System integration takes the whole operation into account, seeking to flawlessly work with data links and on-board data storage, aircraft and payload control systems, mission planning, and image processing and exploitation. Examples of applications are presented including using a small unmanned aircraft at low altitude with a line of sight data link, a long-endurance UAV maritime surveillance mission with on-board processing, and a manned ground moving target indicator application with the radar using multiple receive channels.

Zaugg, Evan C.; Edwards, Matthew C.; Bradley, Joshua P.

2012-05-01

257

Unsupervised synthetic aperture radar image segmentation with superpixels in independent space based on independent component analysis  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar (SAR) image segmentation is a challenging problem in recent years because of the speckle noise. An unsupervised SAR image segmentation with superpixels by independent component analysis (ICA) is proposed. ICA independent space is proposed to represent SAR images for feature extraction effectively. First, the SAR image is divided into small regions by mean-shift algorithm and then those regions are merged in region adjacent graph and full-connected graph based on the Mining Spanning Tree theory, which balances the speed and quality of segmentation. Finally, experiments on X-band TerraSAR images and comparisons with simple linear iterative clustering and graph-cut illustrate the excellent performance of the new method.

Ji, Jian; Li, Xiao-yuan

2014-01-01

258

Mesoscale Near-Surface Wind Speed Variability Mapping with Synthetic Aperture Radar  

PubMed Central

Operationally-significant wind speed variability is often observed within synthetic aperture radar-derived wind speed (SDWS) images of the sea surface. This paper is meant as a first step towards automated distinguishing of meteorological phenomena responsible for such variability. In doing so, the research presented in this paper tests feature extraction and pixel aggregation techniques focused on mesoscale variability of SDWS. A sample of twenty eight SDWS images possessing varying degrees of near-surface wind speed variability were selected to serve as case studies. Gaussian high- and low-pass, local entropy, and local standard deviation filters performed well for the feature extraction portion of the research while principle component analysis of the filtered data performed well for the pixel aggregation. The findings suggest recommendations for future research.

Young, George; Sikora, Todd; Winstead, Nathaniel

2008-01-01

259

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

PubMed

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

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

2004-08-01

260

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

NASA Astrophysics Data System (ADS)

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.

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

2004-08-01

261

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

NASA Technical Reports Server (NTRS)

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).

Jain, A. (inventor)

1985-01-01

262

Study of RADARSAT-2 synthetic aperture radar data for observing sensitive factors of global environmental change  

NASA Astrophysics Data System (ADS)

Global environmental change has gained widespread global attention. It is a complex system with special spatial and temporal evolutionary characteristics. Sensitive factors are indicators of global environmental change, and some can be observed with Earth observation technology. RADARSAT-2 is capable of polarimetric and interferometric observations, which can provide an effective way to document some sensitive factors of global environmental change. This study focuses on the usage of RADARSAT-2 data for observing sensitive factors of environmental change and building highly accurate application models that connect synthetic aperture radar data and observable sensitive factors. These include (1) extracting spatiotemporal distribution of large-scale alluvial fan, (2) extracting vegetation vertical structure, (3) detecting urban land cover change, and (4) monitoring seasonal floods. From this study, RADARSAT-2 data have been demonstrated to have excellent capabilities in documenting several sensitive factors related to global environmental change.

Guo, Huadong; Liu, Guang; Liao, Jingjuan; Li, Xinwu; Zhang, Lu; Shen, Guozhuang; Fu, Wenxue; Sun, Zhongchang

2014-01-01

263

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

NASA Technical Reports Server (NTRS)

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.

Jain, A. (inventor)

1979-01-01

264

Region based target detection approach for synthetic aperture radar images and its parallel implementation  

NASA Astrophysics Data System (ADS)

Automatic target detection (ATD) methods for synthetic aperture radar (SAR) imagery are sensitive to image resolution, target size, clutter complexity, and speckle noise level. However, a robust ATD method needs to be less sensitive to the above factors. In this study, a constant false alarm rate (CFAR) based method is proposed which can perform target detection independent of image resolution and target size even in heterogeneous background clutter. The proposed method is computationally efficient since clutter statistics are calculated only for candidate target regions and a single execution of the method is sufficient for different types of targets having different shapes and sizes. Computational efficiency is further increased by parallelizing the algorithm using OpenMP and NVidia CUDA implementations.

Nar, Fatih; Demirkesen, Can; Okman, O. Erman; Cetin, Mujdat

2012-05-01

265

A two-level image pair simulator for interferometric synthetic aperture radar  

NASA Astrophysics Data System (ADS)

This paper presents a novel simulator to obtain single-look complex (SLC) image pair from the distributed target for interferometric synthetic aperture radar (InSAR). From conventional works, two simulation levels are derived: one is raw signal level (RSL) which means using raw signal to obtain SLC image pairs, the other is SLC image level (SIL) which means obtaining the SLC image pairs directly from existing SAR images. Conventional simulators only work on one simulation level, use complicated backscattering models, have high computational load on RSL and mismatch the real data on SIL. The novel simulator can robustly work on both RSL and SIL. It not only simplified the backscattering model, but also reduces the computational load on RSL. Moreover, the novel simulator creatively uses complex backscattering coefficient (CBC) pair to generate SLC image pair on SIL, which makes the result more accurately match real data. Finally, the improvements of this novel simulator are demonstrated by experimental results.

Chen, Wenxun; Xiang, Zheng; Liu, Xingzhao; Zhu, Mengmeng

2008-10-01

266

Particle swarm optimization-based despeckling and decluttering of wavelet packet transformed synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

The performance of automatic target recognition in synthetic aperture radar images is greatly influenced by preprocessing, viz, despeckling and decluttering. In this work, a particle swarm optimization (PSO)-based adaptive wavelet packet transform is introduced for despeckling and decluttering of military targets including tanks, bulldozers, trucks, cars, cannons, and armored personnel carriers. The proposed method consists of two stages. The first stage removes speckle, and the second stage removes clutter with the aid of PSO to optimize the objective criteria, such as equivalent number of looks and signal to clutter ratio, respectively. The purpose of these methods is to enhance the target feature suitable for further processing. The proposed work has been tested on the moving and stationary target acquisition and recognition database and shows a remarkable performance over existing methods.

Vasuki, Perumal; Mohamed Mansoor Roomi, S.

2013-01-01

267

Analysis of spatially mismatched imagery for synthetic aperture radar ATR classification  

NASA Astrophysics Data System (ADS)

Template-based classification algorithms used with synthetic aperture radar (SAR) automatic target recognition (ATR) degrade in performance when used with spatially mismatched imagery. The degradation, caused by a spatial mismatch between the template and image, is analyzed to show acceptable tolerances for SAR systems. The mismatch between the image and template is achieved by resampling the test imagery to different pixel spacings. A consistent SAR dataset is used to examine pixel spacings between 0.1069 and 0.2539 meters with a nominal spacing of 0.2021 meters. Performance degradation is observed as the pixel spacing is adjusted, Small amounts of variation in the pixel spacing cause little change in performance and allow design engineers to set reliable tolerances. Alternatively, the results show that using templates and images collected from slightly different sensor platforms is a very real possibility with the ability to predict the classification performance.

Rupp, Chad T.; Halversen, Shawn D.; Montagnino, Lee J.; Hebert, Christina L.; Young, Matthew T.; Cassabaum, Mary L.; Ku, Neilson

2008-05-01

268

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

NASA Astrophysics Data System (ADS)

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.

Rait, Gary L.

1993-08-01

269

Seasat synthetic-aperture radar data reduction using parallel programmable array processors  

NASA Technical Reports Server (NTRS)

This paper presents a digital processing system that produces the Seasat synthetic-aperture radar (SAR) imagery. The system consists of a SEL 32/77 host minicomputer and three AP-120B array processors. The partitioning of the SAR processing functions and the design of software modules is described. The rationale for selecting the parallel array processor architecture and the methodology for developing the parallel processing scheme on this system is described. This system attains a Seasat SAR data reduction speed of 2.5 h per 25-m resolution 4-look and 100 km x 100 km image frame. A preliminary performance evaluation of this parallel processing system and potential future applications for remote sensing data reduction are described.

Wu, C.; Barkan, B.; Karplus, W. J.; Caswell, D.

1982-01-01

270

Spaceborne synthetic aperture radar design and trade-off analysis for switchable dual incidence angle operation  

NASA Astrophysics Data System (ADS)

The design of a spaceborne Synthetic Aperture Radar (SAR) system operating at a specific incidence angle has been treated fairly well in the literature. Various problems arise when one switches the antenna to a different incidence angle and wants to achieve significant swath with acceptable image quality. The present paper analyzes the problems encountered when a spaceborne SAR system optimized for a lower incidence angle is switched to a higher one or vice versa. Various trade-offs and design aspects are studied to arrive at the optimum antenna dimensions to operate efficiently at two widely separated incidence angles. Emphasis has been laid on the determination of the optimum operating point on the antenna beam pattern corresponding to a given swath. Further, the constraints imposed on system design due to PRF bands formation, Range ambiguity, Orbit and Attitude errors have been analyzed and presented.

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

271

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

NASA Astrophysics Data System (ADS)

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.

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

2012-01-01

272

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

PubMed

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

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

2006-06-01

273

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

NASA Technical Reports Server (NTRS)

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.

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

1983-01-01

274

The Evolution of Convective Storms from Their Footprints on the Sea as Viewed by Synthetic Aperture Radar from Space  

Microsoft Academic Search

SEASAT synthetic aperture radar (SAR) echoes from the sea have previously been shown to be the result of rain and winds produced by convective storms; rain damps the surface waves and causes echo-free holes, while the diverging winds associated with the downdraft generate waves and associated echoes surrounding the holes. Gust fronts are also evident. Such a snapshot from 8

David Atlas; Peter G. Black

1994-01-01

275

Application of multitemporal ERS-2 synthetic aperture radar in delineating rice cropping systems in the Mekong River Delta, Vietnam  

Microsoft Academic Search

The authors report the use of multitemporal ERS-2 satellite synthetic aperture radar (SAR) images in delineating and mapping areas under different rice cropping systems in the Mekong River Delta, Vietnam. Change index maps were generated from seven images acquired between May and December 1996. Using a 3-dB threshold, the pixels in each change index (CI) map were classified into one

Soo Chin Liew; Suan-Pheng Kam; To-Phuc Tuong; Ping Chen; Vo Quang Minh; Hock Lim

1998-01-01

276

Regional Mapping of the Offshore Wind Resource: Towards a Significant Contribution From SpaceBorne Synthetic Aperture Radars  

Microsoft Academic Search

This paper reviews and discusses the benefits of synthetic aperture radar (SAR) satellite imagery for regional mapping of the offshore wind resources, mostly in comparison to the more standard approach of numerical mesoscale and\\/or microscale models. Remote sensing measurements can be used as a complementary approach to numerical models, as well as a semi-autonomous approach to assess offshore and coastal

Philippe Beaucage; Monique Bernier; GaËtan Lafrance; Julien Choisnard

2008-01-01

277

The influence of the marine atmospheric boundary layer on ERS 1 synthetic aperture radar imagery of the Gulf Stream  

Microsoft Academic Search

In September 1991, the ERS 1 synthetic aperture radar (SAR) collected a set of four colocated images over the western Gulf Stream (GS). The SAR images were supple- mented by satellite infrared imagery and measurements of the marine atmospheric boundary layer (MABL) from both a pair of surface buoys and a suite of instruments on the Ukrainian research vessel R\\/V

R. C. Beal; V. N. Kudryavtsev; D. R. Thompson; S. A. Grodsky; D. G. Tilley; V. A. Dulov; H. C. Graber

1997-01-01

278

Capability estimation of the along-track interferometric synthetic-aperture radar in measurements of the ocean surface current velocity  

NASA Astrophysics Data System (ADS)

We propose a simple method for estimation of the resolution of the along-track interferometric synthetic-aperture radar (AT-InSAR) in measurements of the ocean surface current velocity without resorting to the laborious numerical simulation commonly used for this purpose.

Kanevsky, M. B.

2012-09-01

279

Observations of Snow Water Equivalent Change on Landfast First-Year Sea Ice in Winter Using Synthetic Aperture Radar Data  

Microsoft Academic Search

In this paper, we examine the utility of synthetic aperture radar (SAR) backscatter data to detect a change in snow water equivalent (SWE) over landfast first-year sea ice during winter at relatively cold temperatures. We begin by reviewing the theoretical framework for linking microwave scattering from SAR to the thermodynamic and electrical properties of first-year sea ice. Previous research has

John J. Yackel; David G. Barber

2007-01-01

280

Analysis of oceanic long wave refraction at the Gulf Stream boundary using RADARSAT synthetic aperture radar during Hurricane Bonnie  

Microsoft Academic Search

In this study, we analyze the Gulf Stream's effect on the refraction of ocean waves observed in data obtained from the RADARSAT synthetic aperture radar (SAR). The ocean waves observed on this SAR image have very long wavelengths and are mainly generated by Hurricane Bonnie which was located to the east of the Gulf Stream when the SAR image was

Xiaofeng Li; Mingxia He; W. G. Pichel; Kan Zeng; K. S. Friedman; P. Clemente-Colon; Laibu Wang; Chaofang Zhao

2001-01-01

281

Focus of attention for millimeter and ultra wideband synthetic aperture radar imagery  

NASA Astrophysics Data System (ADS)

The major goal of this research is to develop efficient detectors for Synthetic Aperture Radar (SAR) images, exploiting the reflectivity characteristics of targets in different radar types. Target detection is a signal processing problem whereby one attempts to detect a stationary target embedded in background clutter while minimizing the false alarm probability. In radar signal processing, the better resolution provided by the Millimeter Wave (MMW) SAR enhances the detectability of small targets. As radar technology evolves, the newly developed Ultra Wideband (UWB) SAR provides better penetration capabilities to locate concealed targets in foliage. In this thesis we demonstrate that local intensity kernel tests can be formulated based on the generalized likelihood ratio test (GLRT), while preserving constant false alarm rate (CFAR) characteristics. Both the widely used two-parameter CFAR and the g -CFAR can be viewed as special cases of the local intensity tests with different intensity kernels. It is demonstrated that the first-order Gamma kernel is a good approximation for the principal eigenvector of the projected radial intensity of targets, which provides the optimal matching intensity kernel. This also explains the better performance of the g -CFAR detector over the two parameter CFAR detector. We also developed different CFAR subspace detectors for UWB images, utilizing a Laguerre function subspace. The driven response produced by natural clutter degrades the performance of these subspace detectors. In addition to the driven response, the distinguishing feature of metallic targets in UWB is the resonance response. Therefore, we further propose a two-stage detection scheme: g -CFAR detector followed by the quadratic Laguerre discriminator (QLD). We evaluate every detector and discriminator using ROC curves in a large area (about 2 km2) of imagery. The combined g -CFAR and quadratic Laguerre discriminator improve the simple Laguerre subspace detector more than one hundred fold for a perfect detection rate (Pd = 1).

Yen, Li-Kang

282

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

SciTech Connect

(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.

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

1999-05-27

283

Optimal Envisat advanced synthetic aperture radar image parameters for mapping and monitoring Sahelian floodplains  

NASA Astrophysics Data System (ADS)

Floodplains in the Sahel region of Africa are of exceptional socio-economical and ecological importance. Due to their large extent and highly dynamic nature, monitoring these ecosystems can only be performed by means of remote sensing. The capability of the Envisat Advanced Synthetic Aperture Radar (ASAR) sensor to capture radar backscattering at various incident angles and with different polarization combinations, provides opportunities for improved wetland mapping and monitoring. However, little is known of the optimal image parameters, i.e. incident angle, polarization combination, and acquisition time. Backscatter ?° signatures of Land Use and Land Cover (LULC) classes in and around the Waza-Logone floodplain (Cameroon) were analyzed to determine these optimal image parameters. Based on Jeffries-Matusita (JM) distances between all LULC classes it was determined that best separation was obtained with images acquired in the middle of the flooding cycle at a steep incident angle. Furthermore, separability of cross-polarized images was higher than for co-polarized images. The combination of two and three ASAR Alternating Polarization images with highest separability were used as input for a LULC classification. Two methods were evaluated: Pixel-based Maximum Likelihood and object-based Nearest Neighbour (NN) classification. Best results were obtained with the object-based approach.

Westra, Toon; de Wulf, Robert; van Coillie, Frieke; Crabbe, Sarah

2010-03-01

284

Advances in soil moisture retrieval from synthetic aperture radar and hydrological applications  

NASA Astrophysics Data System (ADS)

SummaryThe sensitivity of Synthetic Aperture Radar (SAR) to soil moisture is well established, however, the retrieval of soil moisture from SAR is confounded by the effects of surface roughness and vegetation. This difficulty has resulted in limited applications of SAR as an operational source of soil moisture in hydrology despite the demonstrated benefits of high-resolution distributed soil moisture. Technical and methodological advances such as multi-configuration radar and forthcoming SAR constellations are increasingly mitigating the shortcomings of SAR with respect to soil moisture estimation at the field and catchment scale. At the same time, progress in data assimilation and a better understanding of the impact of phenomena, such as climate change, are revealing the hydrological importance of soil moisture spatial distribution. Thus, despite the currently modest retrieval accuracy, SAR is an important source of soil moisture state information for the hydrological community. Towards the end of increasing the hydrological utilization of SAR soil moisture, a comprehensive literature review was conducted to provide the state-of-the-art of SAR soil moisture retrieval methodology, its limitations and potential. Following the methodology review, a discussion of the benefits and limitations of soil moisture data retrieved from SAR is used to outline the scope of SAR derived soil moisture for hydrological applications.

Kornelsen, Kurt C.; Coulibaly, Paulin

2013-01-01

285

A semiparametric algorithm to retrieve ocean wave spectra from synthetic aperture radar  

NASA Astrophysics Data System (ADS)

A new wave retrieval method for the ERS synthetic aperture radar(SAR) wave mode is presented. The new algorithm, named semiparametric retrieval algorithm (SPRA), uses the full nonlinear mapping relations as proposed by Hasselmann and Hasselmann [1991]. It differs from previous retrieval algorithms in that it does not require a priori information on the sea state. Instead, it combines the observed SAR spectrum with the collocated wind vector from the ERS scatterometer to make an estimate of the wind sea spectrum. The residual signal in the SAR spectrum is interpreted as swell. The method has been validated by collocating over 5 years of SAR wave mode observations with spectral buoy measurements at 11 locations on the open ocean. For wave components longer than 225 m, the standard deviation between the retrieved spectra and buoy observations is 0.41 m, which corresponds to a relative RMS error of 29%. About 10% of the observed SAR spectra were rejected, in particular in light wind conditions when nonwave features such as those caused by slicks dominated the imagette. The bias and scatter in the results obtained under light wind conditions could be reduced by introducing a wind-dependent tilt modulation. This wind-dependent tilt formulation is derived from the empirical CMOD4 relation between the wind vector, the incidence angle, and the radar backscatter for the ERS scatterometer.

Mastenbroek, C.; de Valk, C. F.

2000-02-01

286

Automatic classification of targets in synthetic aperture radar imagery using topographic features  

NASA Astrophysics Data System (ADS)

Automatic classification of target in synthetic aperture radar (SAR) imagery is performed using topographic features. Targets are segmented from wide area imagery using a constant false alarm rate (CFAR) detector. Individual target areas are classified using the topographical primal sketch which assigns each pixel a label that is invariant under monotonic gray tone transformations. A local surface fit is used to estimate the underlying function oat each target pixel. Pixels are classified based on the zero crossings of the first directional derivatives and the extrema of second directional derivatives. These topographic labels along with the quantitative values of second directional derivative extrema and gradient are used in target matching schemes. Multiple matching schemes are investigated including correlation and graph matching schemes that incorporate distance between features as well as similarity measures. Cost functions are tailored to the topographic features inherent in SAR imagery. Trade offs between the different matching schemes are addressed with respect to robustness and computational complexity. Classification is performed using one foot and one meter imagery obtained from XPATCH simulations and the MSTAR synthetic dataset.

Meth, Reuven; Chellappa, Rama

1996-06-01

287

Model-Based Radar Power Calculations for Ultra-Wideband (UWB) Synthetic Aperture Radar (SAR).  

National Technical Information Service (NTIS)

In this study, we establish a relationship between the radar transmitted power, the target signature and the signal-to-noise ratio required for a specific target detection performance in a radar system. While this relationship can be easily derived from t...

T. Dogaru

2013-01-01

288

A hybrid radar waveform design technique for improving slant range resolution in a synthetic aperture radar system  

NASA Astrophysics Data System (ADS)

A 'hybrid' radar waveform design technique is presented for improving slant range resolution in a synthetic aperture radar system which is processor-bandwidth limited. The hybrid waveform consists of K repetitions of L complementary phase coded pulses with linearly increasing carrier frequency from repetition to repetition. Processing of this frequency stepped, phase coded waveform consists of matched filtering on a pulse-by-pulse basis followed by amplitude weighting and coherent summation. The 'composite' ambiguity function is determined and illustrated for the hybrid waveform. A method for selecting optimum amplitude weights based on a cost function related to the integrated sidelobe ratio of the compressed waveform is also presented. This is contrasted with the usual method of choosing a window function with a low peak sidelobe ratio. The results of a computer study are summarized in terms of the cost function, peak and integrated sidelobe ratios, and mainlobe spread ratio as functions of selected waveform parameters. A numerical example is then given which illustrates the improvement factor to be expected by using the hybrid waveform technique.

Koch, D. B.; Tranter, W. H.

289

Spatial Estimation of Soil Moisture Using Synthetic Aperture Radar in Alaska  

NASA Astrophysics Data System (ADS)

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

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

1999-01-01

290

Evaluating soil moisture variability using synthetic aperture radar and terrain indices  

NASA Astrophysics Data System (ADS)

The spatial and temporal variability of soil moisture is influenced by precipitation patterns, local topography, soil texture and vegetation. It is likely that on bare agricultural fields of near homogeneous soil texture, soil moisture distribution is primarily controlled by topography. This research examines the relationship between soil moisture maps derived from satellite-based Synthetic Aperture Radar (SAR) sensors and wetness indices calculated from LiDAR digital elevation models (DEMs) under wet, dry and moderate moisture conditions. The radar response (backscatter) from SAR sensors is related to the dielectric constant of the surface, allowing soil moisture values to be retrieved through inversion techniques in backscatter models. Wetness indices model expected moisture patterns through evaluation of the surface slope and the number of upslope moisture-contributing cells (specific catchment area) at any point. Although multiple wetness indices have been developed and assessed, few researchers have evaluated the relationships of these indices in conjunction with high-resolution SAR imagery. For eight dates spanning fall 2009 and spring 2010, fine quad-polarimetric mode RADARSAT-2 imagery and coincident in situ surface parameter data are used to derive soil moisture maps of a small agricultural watershed in southwestern Ontario. Wetness indices are used as surrogates for soil moisture patterns in the same area. High-resolution LiDAR-derived DEMs at resolutions of 1, 4 and 8 m are used to calculate the ln(As/tan?) wetness index where As is the specific catchment area and ? is the surface slope. Multiple flow accumulation algorithms are employed to define As. Statistical analyses quantify the relationships and the described variance among assorted wetness index outputs and satellite-derived soil moisture under changing surface conditions.

Powell, K. A.; Berg, A. A.

2010-12-01

291

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

SciTech Connect

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.

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

1987-05-01

292

Automatic ship classification system for inverse synthetic aperture radar (ISAR) imagery  

NASA Astrophysics Data System (ADS)

The U.S. Navy has been interested in applying neural network processing architectures to automatically determine the naval class of ships from an inverse synthetic aperture radar (ISAR) on-board an airborne surveillance platform. Currently an operator identifies the target based on an ISAR display. The emergence of the littoral warfare scenario, coupled with the addition of multiple sensors on the platform, threatens to impair the ability of the operator to identify and track targets in a timely manner. Thus, on-board automation is quickly becoming a necessity. Over the past four years the Opto-Radar System Group at MIT Lincoln Laboratory has developed and fielded a neural network based automatic ship classification (ASC) system for ISAR imagery. This system utilizes imagery from the APS-137 ISAR. Previous related work with ASC systems processed either simulated or real ISAR imagery under highly controlled conditions. The focus of this work was to develop a ship classification system capability of providing real-time identification from imagery acquired during an actual mission. The ship classification system described in this report uses both neural network and conventional processing techniques to determine the naval class of a ship from a range- Doppler (ISAR) image. The `learning' capability of the neural network classifier allows a single naval class to be distributed across many categories such that a degree of invariance to ship motion is developed. The ASC system was evaluated on 30 ship class database that had also been used for an operational readiness evaluation of ISAR crews. The results of the evaluation indicate that the ASC system has a performance level comparable to ISAR operators and typically provides a significant improvement in throughput.

Menon, Murali M.

1995-04-01

293

Synthetic aperture radar data visualization on the iPod Touch  

NASA Astrophysics Data System (ADS)

A major area of focus for the Air Force is sensor performance in urban environments. Aircraft with multiple sensor modalities, such as Synthetic Aperture RADAR (SAR), Infrared (IR), and Electro-Optics (EO), are essential for intelligence, surveillance, and reconnaissance (ISR) of current and future urban battlefields. Although applications exist for visualization of these types of imagery, they usually require at least a laptop computer and internet connection. Field operatives need to be able to access georeferenced information about imagery as part of a Geographic Information System (GIS) on mobile devices. The iPod/iPhone has a 640x480 resolution multi-touch display, making it an excellent device for interacting with georeferenced imagery. We created an iPhone application that loads SAR imagery and allows the user to interact with it. The user multi-touch interface provides pan and zoom capabilities as well as options to change parameters relating to the query. We describe how operatives in the field can use this application to investigate SAR and GIS related problems on the iPhone mobile device, which otherwise would require a computer and Internet connection.

Fouts, Aaron; Vickery, Rhonda; Majumder, Uttam; Burchett, Tracy; Klein, Troy; Minardi, Michael

2010-04-01

294

Method and apparatus for reducing range ambiguity in synthetic aperture radar  

SciTech Connect

A modified Synthetic Aperture Radar (SAR) system is disclosed 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.

Kare, J.T.

1999-10-26

295

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

NASA Astrophysics Data System (ADS)

An unsupervised classification method based on the H/? 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 ?. The classification result based on the H/? 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.

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

2014-01-01

296

Seasonal subsidence and rebound in Las Vegas Valley, Nevada, observed by synthetic aperture radar interferometry  

USGS Publications Warehouse

Analyses of areal variations in the subsidence and rebound occurring over stressed aquifer systems, in conjunction with measurements of the hydraulic head fluctuations causing these displacements, can yield valuable information about the compressibility and storage properties of the aquifer system. Historically, stress-strain relationships have been derived from paired extensometer/piezometer installations, which provide only point source data. Because of the general unavailability of spatially detailed deformation data, areal stress-strain relations and their variability are not commonly considered in constraining conceptual and numerical models of aquifer systems. Interferometric synthetic aperture radar (InSAR) techniques can map ground displacements at a spatial scale of tens of meters over 100 km wide swaths. InSAR has been used previously to characterize larger magnitude, generally permanent aquifer system compaction and land subsidence at yearly and longer timescales, caused by sustained drawdown of ground-water levels that produces intergranular stresses consistently greater than the maximum historical stress. We present InSAR measurements of the typically small-magnitude, generally recoverable deformations of the Las Vegas Valley aquifer system occurring at seasonal timescales. From these we derive estimates of the elastic storage coefficient for the aquifer system at several locations in Las Vegas Valley. These high-resolution measurements offer great potential for future investigations into the mechanics of aquifer systems and the spatial heterogeneity of aquifer system structure and material properties as well as for monitoring ongoing aquifer system compaction and land subsidence.

Hoffmann, J.; Zebker, H. A.; Galloway, D. L.; Amelung, F.

2001-01-01

297

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

NASA Technical Reports Server (NTRS)

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).

Onstott, Robert G.; Gineris, Denise J.

1990-01-01

298

3-D synthetic aperture radar interferometry phase unwrapping using extended Kalman filters  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar Interferometry (InSAR) observations allow researchers to map elevations, analyze surface deformation, and even detect ground water level changes from satellites orbiting the Earth. The InSAR phase measurements are inherently wrapped between 0 and 2?. For most physical interpretation methods the phase measurements have to be unwrapped to reveal the full scale of the observations. The unwrapping of multi-dimensional phase data is still a field of active research and here we present an algorithm using an Extended Kalman Filter (EKF). The current implementation of our EKF algorithm utilizes a piecewise linear approximation in space and a simple model in the third dimension (e.g. time). The algorithm starts from wrapped, unfiltered interferograms and filters and unwraps the results at the same time solving for a common topography or deformation rate, starting from the highest quality point in the coherent area and proceeding to unwrap highest quality neighbors. The highest quality neighbors are determined according to the Fisher's Distance, which is a phase quality measure similar to the more commonly used phase derivative variance, but also includes the interferogram coherence. In this presentation we demonstrate the effectiveness of our algorithm for the applications of DEM generation and deformation rate analysis using real data.

Osmanoglu, B.; Wdowinski, S.; Dixon, T. H.

2013-10-01

299

Synthetic aperture radar imagery of airports and surrounding areas: Denver Stapleton International Airport  

NASA Technical Reports Server (NTRS)

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).

Onstott, Robert G.; Gineris, Denise J.

1990-01-01

300

Three dimensional surface slip partitioning of the Sichuan earthquake from Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

The Sichuan earthquake, Mw 7.9, struck the Longmen Shan range front, in the western Sichuan province, China, on 12 May 2008. It severely affected an area where little historical seismicity and little or no significant active shortening were reported before the earthquake (e.g. Gu et al., 1989; Chen et al., 1994; Gan et al., 2007). The Longmen Shan thrust system bounds the eastern margin of the Tibetan plateau and is considered as a transpressive zone since Triassic time that was reactivated during the India-Asia collision (e.g., Tapponnier and Molnar, 1977, Chen and Wilson 1996; Arne et al., 1997, Godard et al., 2009). However, contrasting geological evidences of sparse thrusting and marked dextral strike-slip faulting during the Quaternary along with high topography (Burchfiel et al., 1995; Densmore et al., 2007) have led to models of dynamically driven and sustained topography (Royden et al., 1997) limiting the role of earthquakes in relief building and leaving the mechanism of long term strain distribution in this area as an open question. Here we combine C and L band Synthetic Aperture Radar (SAR) offsets data from ascending and descending paths to retrieve the three dimensional surface slips distribution all along the earthquake ruptures of the Sichuan earthquake. We show a quantitative assessment of the amount of co-seismic slip and its partitioning at the surface.

de Michele, M.; Raucoules, D.; de Sigoyer, J.; Pubellier, M.; Lasserre, C.; Pathier, E.; Klinger, Y.; van der Woerd, J.

2009-12-01

301

Automated global water mapping based on wide-swath orbital synthetic aperture radar  

NASA Astrophysics Data System (ADS)

This paper presents an automated technique, embedded in an online service, which ingests orbital synthetic aperture radar (SAR) imagery and outputs surface water maps in near real time and on a global scale. The service anticipates future open data dissemination of water extent information using the European Space Agency's Sentinel-1 data. The classification methods used are innovative but practical and different per 1 × 1 degree tile. For each tile, a probability distribution function of a pixel, being covered with water or being dry is established based on a long SAR training dataset. These probability distributions are conditional on the backscatter and the incidence angle. In classification mode the probability of water coverage is calculated, conditional on the current backscatter - incidence angle combination. The overlap between the probability distributions of a pixel being wet or dry is used as a proxy for the quality of our classification. The service has multiple uses, e.g. for water body dynamics in times of drought or for urgent inundation extent determination during floods. The service generates data systematically: it is not an on-demand service activated only for emergency response, but instead is always up-to-date and available. We demonstrate its use in flood situations using Envisat ASAR information during the 2011 Thailand floods. A first merge with a NASA near real time water product based on MODIS optical satellite imagery shows excellent agreement between these independent satellite-based water products.

Westerhoff, R. S.; Kleuskens, M. P. H.; Winsemius, H. C.; Huizinga, H. J.; Brakenridge, G. R.

2012-06-01

302

Access to Synthetic Aperture Radar Data from the Alaska Satellite Facility  

NASA Astrophysics Data System (ADS)

The Alaska Satellite Facility (ASF) currently downlinks, archives, processes and distributes Synthetic Aperture Radar (SAR) data for several international satellites. The SAR data are available to NASA-approved researchers and U.S. government agencies. A straightforward proposal process provides easy access to large quantities of worldwide RADARSAT-1 and JERS-1 data, as well as ERS-1 and ERS-2 data for Alaska and Antarctica. This presentation will outline the process by which researchers may access SAR data archived at ASF without charge. Proposals for NASA approval, approximately two to five pages in length, are submitted electronically to asf@eos.nasa.gov and undergo review at NASA and ASF. Key points to include in the proposal are a scientific justification for the data, linkage between proposal goals and NASA Earth Science Enterprise Research Strategy goals, description of data type (archived, new, or both), and the quantity of data required. Once approved, researchers can place new data acquisition requests (DARs) through ASF for RADARSAT-1 and ERS-2. RADARSAT-1 DARs can be anywhere in the world whereas ERS-2 DARs are limited to the ASF and McMurdo Ground Station receiving regions. ASF can also request data archived at select foreign ground stations for approved proposals. With the successful launch of JAXA's Advanced Land Observing Satellite (ALOS), ASF has taken on a new role as the Americas ALOS Data Node (AADN). Data from the three sensors aboard ALOS are available to researchers within the Americas for the cost of production.

Wolf, V. G.; Harbin, M.; Sanches, R.

2006-12-01

303

Method and apparatus for reducing range ambiguity in synthetic aperture radar  

DOEpatents

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.

Kare, Jordin T. (San Ramon, CA)

1999-10-26

304

Oil spill detection using synthetic aperture radar images and feature selection in shape space  

NASA Astrophysics Data System (ADS)

The major goal of the present study is to describe a method by which synthetic aperture radar (SAR) images of oil spills can be discriminated from other phenomena of similar appearance. The optimal features of these dark formations are here identified. Because different materials have different physical properties, they form different shapes. In this case, oil films and lookalike materials have different fluid properties. In this paper, 9 shape features with a total of 95 eigenvalues were selected. Using differential evolution feature selection (DEFS), similar eigenvalues were extracted from total space of oil spills and lookalike phenomena. This process assumes that these similar eigenvalues impair classification. These similar eigenvalues are removed from the total space, and the important eigenvalues (IEs), those useful to the discrimination of the targets, are identified. At least 30 eigenvalues were found to be inappropriate for classification of our shape spaces. The proposed method was found to be capable of facilitating the selection of the top 50 IEs. This allows more accurate classification. Here, accuracy reached 94%. The results of the experiment show that this novel method performs well. It could also be made available to teams across the world very easily.

Guo, Yue; Zhang, Heng Zhen

2014-08-01

305

Adaptive multiparameter spectral feature analysis for synthetic aperture radar target recognition  

NASA Astrophysics Data System (ADS)

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.

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

2012-08-01

306

Target detection in synthetic aperture radar imagery: a state-of-the-art survey  

NASA Astrophysics Data System (ADS)

Target detection is the front-end stage in any automatic target recognition system for synthetic aperture radar (SAR) imagery (SAR-ATR). The efficacy of the detector directly impacts the succeeding stages in the SAR-ATR processing chain. There are numerous methods reported in the literature for implementing the detector. We offer an umbrella under which the various research activities in the field are broadly probed and taxonomized. First, a taxonomy for the various detection methods is proposed. Second, the underlying assumptions for different implementation strategies are overviewed. Third, a tabular comparison between careful selections of representative examples is introduced. Finally, a novel discussion is presented, wherein the issues covered include suitability of SAR data models, understanding the multiplicative SAR data models, and two unique perspectives on constant false alarm rate (CFAR) detection: signal processing and pattern recognition. From a signal processing perspective, CFAR is shown to be a finite impulse response band-pass filter. From a statistical pattern recognition perspective, CFAR is shown to be a suboptimal one-class classifier: a Euclidean distance classifier and a quadratic discriminant with a missing term for one-parameter and two-parameter CFAR, respectively. We make a contribution toward enabling an objective design and implementation for target detection in SAR imagery.

El-Darymli, Khalid; McGuire, Peter; Power, Desmond; Moloney, Cecilia

2013-01-01

307

Shape-based recognition of targets in synthetic aperture radar images using elliptical Fourier descriptors  

NASA Astrophysics Data System (ADS)

This paper primarily investigates the use of shape-based features by an Automatic Target Recognition (ATR) system to classify various types of targets in Synthetic Aperture Radar (SAR) images. In specific, shapes of target outlines are represented via Elliptical Fourier Descriptors (EFDs), which, in turn, are utilized as recognition features. According to the proposed ATR approach, a segmentation stage first isolates the target region from shadow and ground clutter via a sequence of fast thresholding and morphological operations. Next, a number of EFDs are computed that can sufficiently describe the salient characteristics of the target outline. Finally, a classification stage based on an ensemble of Support Vector Machines identifies the target with the appropriate class label. In order to experimentally illustrate the merit of the proposed approach, SAR intensity images from the well-known Moving and Stationary Target Acquisition and Recognition (MSTAR) dataset were used as 10-class and 3-class recognition problems. Furthermore, comparisons were drawn in terms of classification performance and computational complexity to other successful methods discussed in the literature, such as template matching methods. The obtained results portray that only a very limited amount of EFDs are required to achieve recognition rates that are competitive to well-established approaches.

Nicoli, Louis P.; Anagnostopoulos, Georgios C.

2008-05-01

308

The effect of synthetic aperture radar image resolution on target discrimination  

NASA Astrophysics Data System (ADS)

This paper details the effect of spatial resolution on target discrimination in Synthetic Aperture Radar (SAR) images. Multiple SAR image chips, containing targets and non-targets, are used to test a baseline Automatic Target Recognition (ATR) system with reduced spatial resolution obtained by lowering the pixel count or synthesizing a degraded image. The pixel count is lowered by averaging groups of adjoining pixels to form a new single value. The degraded image is synthesized by low-pass-filtering the image frequency space and then lowering the pixel count. To train a linear classifier, a two-parameter Constant False Alarm Rate (CFAR) detector is tested, and three different types of feature spaces, are used: size, contrast, and texture. The results are scored using the Area Under the Receiver Operator Characteristic (AUROC) curve. The CFAR detector is shown to perform better at lower resolution. All three feature sets together performed well with the degradation of resolution; separately the sets had different performances. The texture features performed best because they do not rely on the number of pixels on the target, while the size features performed the worst for the same reason. The contrast features yielded improved performance when the resolution was slightly reduced.

McGowan, John E.; Gustafson, Steven C.; Jackson, Julie A.; Terzuoli, Andrew J., Jr.

2010-04-01

309

The Effect of Synthetic Aperture Radar Image Resolution on Target Discrimination  

NASA Astrophysics Data System (ADS)

This research details the effect of spatial resolution on target discrimination in Synthetic Aper-ture Radar (SAR) images. Multiple SAR image chips containing targets and non-targets are used to test a baseline Automatic Target Recognition (ATR) system with reduced spatial reso-lution obtained by lowering the pixel count or synthesizing a degraded image. The pixel count is lowered by averaging groups of adjoining pixels to form a new single value. The degraded image is synthesized by low-pass filtering the image frequency space and then lowering the pixel count. A two parameter Constant False Alarm Rate (CFAR) detector is tested, and three different types of feature spaces; size, contrast, and texture; are used to train a linear classifier. The results are scored using the Area Under the Receiver Operator Characteristic (AUROC) curve. The CFAR detector is shown to perform better at lower resolution. All three feature sets together performed well with the degradation of resolution; separately the sets had different performances. The texture features performed best because they do not rely on the number of pixels on the target, while the size features performed worst for the same reason. The contrast features yielded improved performance when the resolution was slightly reduced. The views expressed in this article are those of the authors and do not reflect the official policy of the U.S. Air Force, U.S. Department of Defense, or the U.S. Government.

Terzuoli, Andrew; McGowan, John; Gustafson, Steven; Jackson, Julie; Martin, Richard

310

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

NASA Technical Reports Server (NTRS)

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.

Wu, S. T.

1983-01-01

311

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

NASA Astrophysics Data System (ADS)

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.

Parks, S. M.

2012-08-01

312

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

NASA Astrophysics Data System (ADS)

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.

Suwa, Kei; Wakayama, Toshio

2011-05-01

313

A jamming strategy against synthetic aperture radar with varieties of squint angles and wide beams  

NASA Astrophysics Data System (ADS)

In order to form a false scene in Synthetic Aperture Radar (SAR) image, deceptive jammer need to get the relevant SAR parameters. In these parameters, squint angle and beamwidth usally change and it will make the pre-generated jamming signal unuseful. For solving this problem, a strategy is proposed to transform the pre-generated jamming signals to counter SAR with arbitrary squint angle and beamwidth in real time. Firstly, the jamming effects under estimation errors of SAR's squint angle and beam-width are analyzed. Using Graphics Processing Units (GPU), a parallel algorithm to generate jamming signals for varying squint angle and azimuth beam-width is proposed. Then, This paper describes a method that can implement the signal transformation between wide-beam condition and narrow-beam condition. Based on the generated signals, the jamming under arbitrary squint angle and beam-width can be realized in real time. The simulation results shows that this strategy is effective to jam SAR with varieties of squint angles and wide-beams.

Lin, Xiaohong; Xue, Guoyi; Liu, Peiguo

2013-10-01

314

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

NASA Technical Reports Server (NTRS)

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.

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

1984-01-01

315

Registration of synthetic aperture radar images using a multiresolution Radon transform  

NASA Astrophysics Data System (ADS)

This paper describes a new algorithm for registration of synthetic aperture radar (SAR) images. The algorithm is based on cross-correlation in the Radon transform domain, chosen principally because of the prevalence of line-like features in SAR images. The distributed nature of such features, and their persistence in the image independently of 'look angle,' make Radon-domain correlation appropriate for the peculiar challenge of SAR image registration. Furthermore, 2D cross- correlation in Radon space may be efficiently implemented as 1D convolution followed by backprojection. To handle local variations caused by terrain elevations and errors in global parameters, we use a coarse-to-fine matching strategy based on a novel multiresolution Radon transform pyramid. This may be efficiently constructed from an initial fine partition of the image into disjoint tiles, using alternating grouping and decimation steps. The whole algorithm is linear in the number of such tiles. Test results demonstrate that the new algorithm performs comparably to pixel-similarity-based registration when the look angle is the same, and much better for pairs with different look angles.

Payne, Timothy M.; Magarey, Julian F.; Newsam, Garry N.

1998-12-01

316

Feasibility Study of Synthetic Aperture Radar - Adaptability of the Payload to KOMPSAT Platform  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar (SAR) has been used for mapping the surface geomorphology of cloudy planets like Venus as well as the Earth. The cloud-free Mars is also going to be scanned by SAR in order to detect buried water channels and other features under the very shallow subsurface of the ground. According to the 'Mid and Long-term National Space Development Plan' of Korea, SAR satellites, in addition to the EO (Electro-Optical) satellites, are supposed to be developed in the frame of the KOMPSAT (Korean Multi-Purpose Satellite) program. Feasibility of utilizing a SAR payload on KOMPSAT platform has been studied by KARI in collaboration with Astrium U.K. The purpose of the SAR program is Scientific and Civil applications on the Earth. The study showed that KOMPSAT-2 platform can accommodate a small SAR like Astrium's MicroSAR. In this paper, system aspects of the satellite design are presented, such as mission scenario, operation concept, and capabilities. The spacecraft design is also discussed and conclusion is followed.

Kim, Young-Soo; Lee, Sang-Ryool

2002-09-01

317

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

USGS Publications Warehouse

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.

Mayer, Larry; Lu, Zhong

2001-01-01

318

Postseismic displacement of the 1999 Athens earthquake retrieved by the Differential Interferometry by Synthetic Aperture Radar time series  

Microsoft Academic Search

In September 1999, a moderate (Mw = 5.9) earthquake struck the Attica plain, causing unexpected and extensive damage to Athens and its population. In this work, we exploit the potential of multitemporal Differential Interferometry by Synthetic Aperture Radar (DInSAR) analysis, using about a hundred European Remote Sensing (ERS) 1\\/2 images to calculate the displacement time series from 1992 to 2002.

Simone Atzori; Michele Manunta; Gianfranco Fornaro; Athanassios Ganas; Stefano Salvi

2008-01-01

319

Postseismic displacement of the 1999 Athens earthquake retrieved by the Differential Interferometry by Synthetic Aperture Radar time series  

Microsoft Academic Search

In September 1999, a moderate (M w = 5.9) earthquake struck the Attica plain, causing unexpected and extensive damage to Athens and its population. In this work, we exploit the potential of multitemporal Differential Interferometry by Synthetic Aperture Radar (DInSAR) analysis, using about a hundred European Remote Sensing (ERS) 1\\/2 images to calculate the displacement time series from 1992 to

Simone Atzori; Michele Manunta; Gianfranco Fornaro; Athanassios Ganas; Stefano Salvi

2008-01-01

320

Geometric and radiometric calibration of synthetic aperture radar images acquired in alpine regions-spaceborne and airborne  

Microsoft Academic Search

Multi-temporal synthetic aperture radar (SAR) images acquired in alpine regions by spaceborne and airborne instruments are radiometric and geometric calibrated using corner reflectors, high precision digital elevation model (DEM) and orthophoto images. A fully automatic procedure are developed and applied to multi-temporal series of images acquired from the Norwegian test site of the EMAC'95 campaign. The results show that the

I. Lauknes; H. Johnsen; T. Guneriussen

1998-01-01

321

Multi-temporal monitoring of wetland water levels in the Florida Everglades using interferometric synthetic aperture radar (InSAR)  

Microsoft Academic Search

Interferometric synthetic aperture radar (InSAR) techniques can successfully detect phase variations related to the water level changes in wetlands and produce spatially detailed high-resolution maps of water level changes. Despite the vast details, the usefulness of the wetland InSAR observations is rather limited, because hydrologists and water resources managers need information on absolute water level values and not on relative

Sang-Hoon Hong; Shimon Wdowinski; Sang-Wan Kim; Joong-Sun Won

2010-01-01

322

Delineation of inundated area and vegetation along the Amazon floodplain with the SIR-C synthetic aperture radar  

Microsoft Academic Search

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

Laura L. Hess; John M. Melack; Solange Filoso; Yong Wang

1995-01-01

323

Small-scale deformations associated with the 1992 Landers, California, earthquake mapped by synthetic aperture radar interferometry phase gradients  

Microsoft Academic Search

Abstract. The Landers earthquake ( Mw7.3) 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 x 100 km region surrounding the northern portion of the earthquake rupture. Also,

Evelyn J. Price; David T. Sandwell

1998-01-01

324

A geosynchronous synthetic aperture radar; for tectonic mapping, disaster management and measurements of vegetation and soil moisture  

Microsoft Academic Search

A geosynchronous synthetic aperture radar (SAR) with an orbit inclination of 50-65° can provide daily coverage of all of North and South America. Longitudinally, the width of the mapped area would be on the order of ±50° at the Equator, somewhat more at the most northern\\/southern latitudes. Within the area mapped, very good temporal coverage can be obtained-up to several

S. N. Madsen; Wendy Edelstein; Leo D. DiDomenico; John LaBrecque

2001-01-01

325

Using C-Band Synthetic Aperture Radar Data to Monitor Forested Wetland Hydrology in Maryland's Coastal Plain, USA  

Microsoft Academic Search

Hydrology (i.e., inundation and soil moisture) is the most important abiotic factor controlling wetland function and extent, and scientists predict that wetland hydrology can be significantly altered over relatively short timescales due to climate change and anthropogenic impact. Whereas broadscale hydrology is difficult to monitor in forested wetlands with ground-based and optical remote sensing methods, C-band synthetic aperture radar (SAR)

Megan W. Lang; Eric S. Kasischke

2008-01-01

326

Modeling Collapse Chimney and Spall Zone Settlement as a Source of Post-Shot Subsidence Detected by Synthetic Aperture Radar Interferometry.  

National Technical Information Service (NTIS)

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 (V...

W. Foxall

2000-01-01

327

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

USGS Publications Warehouse

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

Wildey, R. L.

1980-01-01

328

Forest biomass, canopy structure, and species composition relationships with multipolarization L-band synthetic aperture radar data  

NASA Technical Reports Server (NTRS)

The effect of forest biomass, canopy structure, and species composition on L-band synthetic aperature radar data at 44 southern Mississippi bottomland hardwood and pine-hardwood forest sites was investigated. Cross-polarization mean digital values for pine forests were significantly correlated with green weight biomass and stand structure. Multiple linear regression with five forest structure variables provided a better integrated measure of canopy roughness and produced highly significant correlation coefficients for hardwood forests using HV/VV ratio only. Differences in biomass levels and canopy structure, including branching patterns and vertical canopy stratification, were important sources of volume scatter affecting multipolarization radar data. Standardized correction techniques and calibration of aircraft data, in addition to development of canopy models, are recommended for future investigations of forest biomass and structure using synthetic aperture radar.

Sader, Steven A.

1987-01-01

329

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

NASA Technical Reports Server (NTRS)

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.

Smith, Robert C.

2006-01-01

330

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

331

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

NASA Technical Reports Server (NTRS)

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.

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

2003-01-01

332

Demonstration of synthetic aperture imaging ladar  

Microsoft Academic Search

The spatial resolution of a conventional imaging LADAR system is constrained by the diffraction limit of the telescope aperture. The purpose of this work is to investigate Synthetic Aperture Imaging LADAR (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. This paper details our

W. Buell; N. Marechal; J. Buck; R. Dickinson; D. Kozlowski; T. Wright; S. Beck

2005-01-01

333

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)

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.

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

1994-01-01

334

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

NASA Astrophysics Data System (ADS)

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.

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

2012-12-01

335

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

NASA Astrophysics Data System (ADS)

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.

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

2014-01-01

336

Performance of Scattering Matrix Decomposition and Color Spaces for Synthetic Aperture Radar Imagery  

NASA Astrophysics Data System (ADS)

Polarimetrc Synthetic Aperture Radar (SAR) has been shown to be a powerful tool in re-mote sensing because uses up to four simultaneous measurements giving additional degrees of freedom for processing. Typically, polarization decomposition techniques are applied to the polarization-dependent data to form colorful imagery that is easy for operators systems to interpret. Yet, the presumption is that the SAR system operates with maximum bandwidth which requires extensive processing for near-or real-time application. In this research, color space selection is investigated when processing sparse polarimetric SAR data as in the case of the publicly available Volumetric SAR Data Set, Version 1:0". To improve information quality in resultant color imagery, three scattering matrix decompositions were investigated (linear, Pauli and Krogager) using two common color spaces (RGB, CMY) to deter-mine the best combination for accurate feature extraction. A mathematical model is presented for each de-composition technique and color space to the Cramer-Rao lower bound (CRLB) and quantify the performance bounds from an estimation perspective for given SAR system and processing parameters. After a deep literature review in color science, the mathematical model for color spaces was not able to be computed together with the mathematical model for decomposition techniques. The color spaces used for this research were functions of variables that are out of the scope of electrical engineering research and include factors such as the way humans sense color, envi-ronment inuences in the color stimulus and device technical characteristics used to display the SAR image. Hence, SAR imagery was computed for speci c combinations of decomposition technique and color space and allow the reader to gain an abstract view of the performance differences. The views expressed in this article are those of the authors and do not reflect the official policy of the U.S. Air Force, U.S. Department of Defense, or the U.S. Government.

Terzuoli, Andrew; Arriagada, Manuel; Saville, Michael

337

Synthetic aperture radar interferometry coherence analysis over Katmai volcano group, Alaska  

USGS Publications Warehouse

The feasibility of measuring volcanic deformation or monitoring deformation of active volcanoes using space-borne synthetic aperture radar (SAR) interferometry depends on the ability to maintain phase coherence over appropriate time intervals. Using ERS 1 C band (?? = 5.66 cm) SAR imagery, we studied the seasonal and temporal changes of the interferometric SAR coherence for fresh lava, weathered lava, tephra with weak water reworking, tephra with strong water reworking, and fluvial deposits representing the range of typical volcanic surface materials in the Katmai volcano group, Alaska. For interferograms based on two passes with 35 days separation taken during the same summer season, we found that coherence increases after early June, reaches a peak between the middle of July and the middle of September, and finally decreases until the middle of November when coherence is completely lost for all five sites. Fresh lava has the highest coherence, followed by either weathered lava or fluvial deposits. These surfaces maintain relatively high levels of coherence for periods up to the length of the summer season. Coherence degrades more rapidly with time for surfaces covered with tephra. For images taken in different summers, only the lavas maintained coherence well enough to provide useful interferometric images, but we found only a small reduction in coherence after the first year for surfaces with lava. Measurement of volcanic deformation is possible using summer images spaced a few years apart, as long as the surface is dominated by lavas. Our studies suggest that in order to make volcanic monitoring feasible along the Aleutian arc or other regions with similar climatic conditions, observation intervals of the satellite with C band SAR should be at least every month from July through September, every week during the late spring/early summer or late fall, and every 2-3 days during the winter. Copyright 1998 by the American Geophysical Union.

Lu, Z.; Freymueller, J. T.

1998-01-01

338

Ocean Observer Synthetic Aperture Radar User and Instrument Requirements and Configuration  

NASA Astrophysics Data System (ADS)

User and instrument requirements for a U.S. operational ocean and land observing synthetic aperture radar (SAR) has emerged out of the Ocean Observer Satellite Study sponsored by the U.S. Dept. of Commerce/Dept. of Defense/National Aeronautics and Space Administration Integrated Program Office. User requirements were identified for thirty parameters that are best measured with SAR instruments. These include coastal sea surface winds, wave characteristics, ocean currents, surf conditions, sea and lake ice type/motion/concentration/edge-location, flood mapping, land surface deformation, land surface topography, soil moisture, and land surface freeze/thaw state. The user requirements have been summarized in an Ocean Observer User Requirements Document including details of horizontal measurement spacing, measurement accuracy, refresh rate, geographic coverage, and long term stability. The SAR instrument requirements needed to measure these parameters were analyzed, drawing on the scientific literature, previous study reports and the experience of the User Requirements Team. The SAR instrument/satellite requirements and notional design that emerged from this process consists of a 15-year mission using three satellites, each with 7.5 year lifetime. During part of the mission, two satellites would fly in formation for cross track interferometry to allow precision land topography measurement. The satellites would be in sun-synchronous polar orbit with 1:00 pm ascending equator crossing time with a 8-day exact repeat orbit. The SAR would be a dual frequency (C-band and L-band), multi-polarization, multi-mode instrument. Orbit maintenance would allow repeat pass interferometry and antenna design would allow along-track interferometry for ocean current measurement.

McGuire, J. P.; Cunningham, J. D.; Gerber, A. J.; Pichel, W. G.

2002-12-01

339

Automated global water mapping based on wide-swath orbital synthetic-aperture radar  

NASA Astrophysics Data System (ADS)

This paper presents an automated technique which ingests orbital synthetic-aperture radar (SAR) imagery and outputs surface water maps in near real time and on a global scale. The service anticipates future open data dissemination of water extent information using the European Space Agency's Sentinel-1 data. The classification methods used are innovative and practical and automatically calibrated to local conditions per 1 × 1° tile. For each tile, a probability distribution function in the range between being covered with water or being dry is established based on a long-term SAR training dataset. These probability distributions are conditional on the backscatter and the incidence angle. In classification mode, the probability of water coverage per pixel of 1 km × 1 km is calculated with the input of the current backscatter - incidence angle combination. The overlap between the probability distributions of a pixel being wet or dry is used as a proxy for the quality of our classification. The service has multiple uses, e.g. for water body dynamics in times of drought or for urgent inundation extent determination during floods. The service generates data systematically: it is not an on-demand service activated only for emergency response, but instead is always up-to-date and available. We validate its use in flood situations using Envisat ASAR information during the 2011 Thailand floods and the Pakistan 2010 floods and perform a first merge with a NASA near real time water product based on MODIS optical satellite imagery. This merge shows good agreement between these independent satellite-based water products.

Westerhoff, R. S.; Kleuskens, M. P. H.; Winsemius, H. C.; Huizinga, H. J.; Brakenridge, G. R.; Bishop, C.

2013-02-01

340

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

NASA Technical Reports Server (NTRS)

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.

Lyons, Suzanne; Sandwell, David

2003-01-01

341

Airborne synthetic aperture radar observations and simulations for waves in ice  

NASA Astrophysics Data System (ADS)

The Canada Centre for Remote Sensing CV-580 aircraft collected C-band synthetic aperture radar (SAR) data over the marginal ice zone off the east coast of Newfoundland during the Labrador Ice Margin Experiment (LIMEX) in March 1989. One component of the LIMEX'89 program was the study of ocean waves penetrating the marginal ice zone. In this paper, we consider nearly coincidental observations of waves in ice by airborne SAR and wave-induced ice motion measurements. We explain the wave patterns observed in the SAR imagery, and the corresponding SAR image spectra, in terms of SAR wave imaging models. These include the well-known tilt cross-section modulation, linear, quasi-linear, and nonlinear velocity bunching forward mapping models (FMMs), and the assertion that the concept of coherence time limitation applies differently to the cases of waves in ice and open water. We modify the concept of the scene coherence time to include two parts: first, a decorrelation time deduced from the inherent azimuth cutoff in the nonlinear velocity bunching FMM; and second, the intrinsic scene coherence time which is a measure of the time scale over which an open water Bragg scattering patch retains its phase structure. Either of these coherence time scales could dominate the SAR image formation process, depending upon the environmental conditions (the wave spectrum and the wind speed, for example). These two coherence time scales are independently estimated based upon a quasi-linear velocity bunching FMM applied to some of the LIMEX'89 observations. Observed SAR image spectra and forward mapped ice motion package spectra are favorably compared.

Vachon, Paris W.; Olsen, Richard B.; Krogstad, Harald E.; Liu, Antony K.

1993-01-01

342

Motion estimation and imaging of complex scenes with synthetic aperture radar  

NASA Astrophysics Data System (ADS)

We study synthetic aperture radar (SAR) imaging and motion estimation of complex scenes consisting of stationary and moving targets. We use the classic SAR setup with a single antenna emitting signals and receiving the echoes from the scene. The known motion estimation methods for SAR work only in simple cases, with one or a few targets in the same motion. We propose to extend the applicability of these methods to complex scenes, by complementing them with a data pre-processing step intended to separate the echoes from the stationary targets and the moving ones. We present two approaches. The first is an iteration designed to subtract the echoes from the stationary targets one by one. This approach first estimates the location of each stationary target from a preliminary image, and then uses the location to define a filter that removes the corresponding target’s echo from the data. The second approach is based on the robust principal component analysis (PCA) method. The key observation is that with appropriate pre-processing and windowing, the discrete samples of the stationary target echoes form a low-rank matrix, whereas the samples of a few moving target echoes form a high-rank sparse matrix. The robust PCA method is designed to separate the low rank from the sparse part, and thus can be used for the SAR data separation. We present a brief analysis of the two methods and explain how they can be combined to improve the data separation for extended and complex imaging scenes. We also assess the performance of the methods with extensive numerical simulations.

Borcea, Liliana; Callaghan, Thomas; Papanicolaou, George

2013-05-01

343

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

NASA Astrophysics Data System (ADS)

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

Vesecky, John F.; Stewart, Robert H.

1982-04-01

344

Ocean wave directional spectra and wave-current interaction in the Agulhas from the Shuttle Imaging Radar-B synthetic aperture radar  

NASA Technical Reports Server (NTRS)

SIR-B synthetic aperture radar ocean-wave spectra for a 200-km pass crossing the Agulhas current off the coast of Africa are analyzed. A significant enhancement of one spectral peak along the northern edge of the current is attributed both to amplification of the waves by refraction-dominated wave-current interaction and to transient specular backscatter contributions spatially correlated to the waves.

Irvine, D. E.; Tilley, D. G.

1988-01-01

345

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

NASA Astrophysics Data System (ADS)

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.

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

2014-05-01

346

Synthetic aperture radar for a crop information system: A multipolarization and multitemporal approach  

NASA Astrophysics Data System (ADS)

Acquisition of timely information is a critical requirement for successful management of an agricultural monitoring system. Crop identification and crop-area estimation can be done fairly successfully using satellite sensors operating in the visible and near-infrared (VIR) regions of the spectrum. However, data collection can be unreliable due to problems of cloud cover at critical stages of the growing season. The all-weather capability of synthetic aperture radar (SAR) imagery acquired from satellites provides data over large areas whenever crop information is required. At the same time, SAR is sensitive to surface roughness and should be able to provide surface information such as tillage-system characteristics. With the launch of ERS-1, the first long-duration SAR system became available. The analysis of airborne multipolarization SAR data, multitemporal ERS-1 SAR data, and their combinations with VIR data, is necessary for the development of image-analysis methodologies that can be applied to RADARSAT data for extracting agricultural crop information. The overall objective of this research is to evaluate multipolarization airborne SAR data, multitemporal ERS-1 SAR data, and combinations of ERS-1 SAR and satellite VIR data for crop classification using non-conventional algorithms. The study area is situated in Norwich Township, an agricultural area in Oxford County, southern Ontario, Canada. It has been selected as one of the few representative agricultural 'supersites' across Canada at which the relationships between radar data and agriculture are being studied. The major field crops are corn, soybeans, winter wheat, oats, barley, alfalfa, hay, and pasture. Using airborne C-HH and C-HV SAR data, it was found that approaches using contextual information, texture information and per-field classification for improving agricultural crop classification proved to be effective, especially the per-field classification method. Results show that three of the four best per-field classification accuracies (\\ K=0.91) are achieved using combinations of C-HH and C-VV SAR data. This confirms the strong potential of multipolarization data for crop classification. The synergistic effects of multitemporal ERS-1 SAR and Landsat TM data are evaluated for crop classification using an artificial neural network (ANN) approach. The results show that the per-field approach using a feed-forward ANN significantly improves the overall classification accuracy of both single-date and multitemporal SAR data. Using the combination of TM3,4,5 and Aug. 5 SAR data, the best per-field ANN classification of 96.8% was achieved. It represents an 8.5% improvement over a single TM3,4,5 classification alone. Using multitemporal ERS-1 SAR data acquired during the 1992 and 1993 growing seasons, the radar backscatter characteristics of crops and their underlying soils are analyzed. The SAR temporal backscatter profiles were generated for each crop type and the earliest times of the year for differentiation of individual crop types were determined. Orbital (incidence-angle) effects were also observed on all crops. The average difference between the two orbits was about 3 dB. Thus attention should be given to the local incidence-angle effects when using ERS-1 SAR data, especially when comparing fields from different scenes or different areas within the same scene. Finally, early- and mid-season multitemporal SAR data for crop classification using sequential-masking techniques are evaluated, based on the temporal backscatter profiles. It was found that all crops studied could be identified by July 21.

Ban, Yifang

347

SAR-related stress variability in the marine atmospheric boundary layer. Final report, 1 June 1990-30 September 1992. [SAR (Synthetic Aperture Radars)  

Microsoft Academic Search

Satellite- or aircraft-bourne synthetic aperture radars (SAR) have the potential to serve as a powerful and essential part of the global meteorological\\/oceanographic observation system. While the potential of SAR systems is enormous, quantitative interpretation of SAR signals has clearly been frustrated by our incomplete understanding of the relationships between the radar backscatter cross section and a complicated heterogeneous and constantly

H. N. Shier; G. S. Young

1992-01-01

348

A rectangular-fit classifier for synthetic aperture radar automatic target recognition  

NASA Astrophysics Data System (ADS)

The utility of a rectangular-fit classifier for Synthetic Aperture Radar Automatic Target Recognition (SAR ATR) is examined. The target is fitted with and modeled as a rectangle that can best approximate its boundary. The rectangular fit procedure involves 1) a preprocessing phase to remove the background clutter and noise, 2) a pose detection phase to establish the alignment of the rectangle via a least squares straight line fitting algorithm, and 3) size determination phase via stretching the width and the height dimensions of the rectangle in order to encapsulate a pre-specified, e.g., 90%, of the points in the target. A training set composed of approximately half the total images in the MSTAR public imagery database are used to obtain and record the statistical variations in the width and height of the resulting rectangles for each potential target. The remaining half of the images is then used to assess the performance of this classifier. Preliminary results using minimum Euclidean and Mahalanobis distance classifiers show overall accuracies of 44% and 42%, respectively. Although the classification accuracy is relatively low, this technique can be successfully used in combination with other classifiers such as peaks, edges, corners, and shadow-based classifiers to enhance their performances. A unique feature of the rectangular fit classifier is that it is rotation invariant in its present form. However, observation of the dataset reveals that in general the shapes of the targets in SAR imagery are not fully rotation invariant. Thus, the classification accuracy is expected to improve considerably using multiple training sets, i.e., one training set generated and used for each possible pose. The tradeoff is the increased computation complexity which tends to be offset by ever increasing efficiency and speed of the processing hardware and software. The rectangular fit classifier can also be used as a pose detection routine and/or in conjunction with other ATR schemes, such as shadow-based ATR, that require an initial pose detection phase prior to matching.

Saghri, John A.; Cary, Daniel A.

2007-10-01

349

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

NASA Astrophysics Data System (ADS)

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.

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

2002-08-01

350

Using Synthetic Aperture Radar Wind Measurements to support Offshore Wind Parks  

NASA Astrophysics Data System (ADS)

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.

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

2003-04-01

351

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

NASA Astrophysics Data System (ADS)

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.

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

352

Detection of linear features in synthetic-aperture radar images by use of the localized Radon transform and prior information  

NASA Astrophysics Data System (ADS)

A new linear-features detection method is proposed for extracting straight edges and lines in synthetic-aperture radar images. This method is based on the localized Radon transform, which produces geometrical integrals along straight lines. In the transformed domain, linear features have a specific signature: They appear as strongly contrasted structures, which are easier to extract with the conventional ratio edge detector. The proposed method is dedicated to applications such as geographical map updating for which prior information (approximate length and orientation of features) is available. Experimental results show the method's robustness with respect to poor radiometric contrast and hidden parts and its complementarity to conventional pixel-by-pixel approaches.

Onana, Vincent-De-Paul; Trouvé, Emmanuel; Mauris, Gilles; Rudant, Jean-Paul; Tonyé, Emmanuel

2004-01-01

353

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

NASA Astrophysics Data System (ADS)

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.

Thompson, T. W.

1983-06-01

354

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

SciTech Connect

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.

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

1999-06-24

355

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

PubMed Central

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.

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

2008-01-01

356

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

NASA Technical Reports Server (NTRS)

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.

Imhoff, Marc Lee; Gesch, Dean B.

1990-01-01

357

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

NASA Technical Reports Server (NTRS)

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.

Mader, G. L.

1981-01-01

358

Comprehensive contrast comparison of laver cultivation area extraction using parameters derived from polarimetric synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

Image contrast between extracted laver cultivation area and background water was extensively compared using various parameters that can be calculated by dual- and quad-polarization (fully polarimetric) synthetic aperture radar data. Each parameter derived from Pauli decomposition, eigenvalue analysis, coherence analysis, and four-component scattering power decomposition (4-CSPD) has distinctive characteristics and react to different backscatterers differently. Contrast comparison was made using these parameters using the L-band quad-polarization data acquired by phased-array L-band synthetic aperture radar (PALSAR) on board advanced land observing satellite (ALOS) and the X-band dual-polarization data acquired by TerraSAR-X, and experimental results showed that the contrast can be improved using multi-polarization data than using single-polarization data. It has also been found that entropy performs better among dual-polarization methods, and the surface scattering component calculated from 4-CSPD exhibits higher contrast than any other parameters from quad-polarization data.

Sugimoto, Mitsunobu; Ouchi, Kazuo; Nakamura, Yasuhiro

2013-01-01

359

Science Results from the Spaceborne Imaging Radar-C/X-Band Synthetic Aperture Radar (SIR-C/X-SAR): Progress Report  

NASA Technical Reports Server (NTRS)

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.

Evans, Diane L. (Editor); Plaut, Jeffrey (Editor)

1996-01-01

360

Observation of wave refraction at an ice edge by synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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).

Liu, Antony K.; Vachon, Paris W.; Peng, Chih Y.

1991-01-01

361

Estimation of the possibility to measure the elevation of the rough water surface using a cross-track interferometric synthetic aperture radar  

NASA Astrophysics Data System (ADS)

We analyze the operation of an oceanographic cross-track interferometric synthetic aperture radar and present estimates of the signal-to-noise ratio in the obtained interferograms. It is shown that after filtering additive phase noise, the interferograms allow one to restore the profile of a sufficiently large-scale part of water-surface roughness. The criterion of large-scale roughness is determined mainly by the ratio R/V of the oblique distance R to the velocity V of a carrier of the interferometric synthetic aperture radar, as well as by the character and propagation direction of the surface roughness.

Kanevsky, M. B.

2013-02-01

362

Implementation and evaluation of coherent synthetic aperture radar processing for level measurements of bulk goods with an FMCW-system  

NASA Astrophysics Data System (ADS)

In industrial process measurement instrumentation, radar systems are well established for the measurement of filling levels of liquids in tanks. Level measurements of bulk goods in silos, on the other hand, are more challenging because the material is heaped up and its surface has typically a relatively complex shape. In this paper, the application of synthetic aperture radar (SAR) reconstruction with a frequency modulated continuous wave (FMCW) radar system for level measurements of bulk goods is evaluated. In the proposed monostatic setup, echo signals are acquired at discrete antenna positions on top of the silo. Spatially resolved information about the surface contour of a bulk good heap is reconstructed by coherent 'delay and sum' processing. The concept has been experimentally evaluated with a 24 to 26 GHz FMCW radar system mounted on a linear stepping motor positioning unit. Measurements on a thin metal wire at different range and on a curved test-object with a diffusely scattering surface have been performed to analyze the system's point spread function (PSF) and performance. Constant range and azimuth resolutions (-6 dB) of 15 cm and 8 cm, respectively, have been obtained up to a range of 6 m, and results of further evaluations show that the proposed concept allows more accurate and reliable level reconstructions of surface profiles compared to the conventional approach with measurements at a single antenna position.

Vogt, M.; Gerding, M.; Musch, T.

2010-09-01

363

Experimental study of near-surface radar imaging of buried objects with adaptive focused synthetic aperture processing  

NASA Astrophysics Data System (ADS)

This paper deals with the application of stepped frequency radar to subsurface imaging of buried targets with a final aim of object imaging and identification. The applications are mainly mines or UXO detection but also buried pipes. The depths considered here are a few cm to 15 cm under the surface (from the top of the object). It is necessary to use a UWB radar in order to separate the soil interface from the top of the object. A versatile system has been built that can be brought outdoor. It is used to find the best parameters for a future optimal radar. Special antennas have been realized that cover the 500 MHz to 8 GHz frequency range. The antenna pair (T/R) moves at a given height over the soil surface along a rail. Radar returns are then processed on a PC in order to deliver in a few seconds a 2D vertical profile of the soil. A special algorithm for near field synthetic focusing aperture has been developed for this task. It takes into account the wave propagation in the soil. Tomographic images are presented for different objects in different soils (.5 to 5 GHz and 2 to 8 GHz bandwidths) that show the quality of the results delivered by this improved technique. Conclusion are drawn on the potentialities and the limitations of the method and future perspectives like 3D imaging.

Millot, Patrick; Bureau, J. C.; Borderies, P.; Bachelier, E.; Pichot, Christian; Le Brusq, E.; Guillanton, E.; Dauvignac, J. Y.

2000-07-01

364

A comparison of spatial sampling techniques enabling first principles modeling of a synthetic aperture RADAR imaging platform  

NASA Astrophysics Data System (ADS)

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.

Gartley, Michael; Goodenough, Adam; Brown, Scott; Kauffman, Russel P.

2010-04-01

365

Two-beam-coupling correlator for synthetic aperture radar image recognition with power-law scattering centers preenhancement.  

PubMed

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 targets is utilized. The joint input image consists of a prepower-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, Horner efficiency, and correlation-peak intensity. The results showed significant improvement as the power increased. PMID:18516129

Haji-Saeed, Bahareh; Woods, Charles L; Kierstead, John; Khoury, Jed

2008-06-01

366

Status and future of laser scanning, synthetic aperture radar and hyperspectral remote sensing data for forest biomass assessment  

NASA Astrophysics Data System (ADS)

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.

Koch, Barbara

2010-11-01

367

Analysis of urban area land cover using SEASAT Synthetic Aperture Radar data  

NASA Technical Reports Server (NTRS)

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.

Henderson, F. M. (principal investigator)

1980-01-01

368

Inverse synthetic aperture radar processing using parametric time-frequency estimators Phase I  

SciTech Connect

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.

Candy, J.V., LLNL

1997-12-31

369

Automatic Synthetic Aperture Radar based oil spill detection and performance estimation via a semi-automatic operational service benchmark.  

PubMed

Today the health of ocean is in danger as it was never before mainly due to man-made pollutions. Operational activities show regular occurrence of accidental and deliberate oil spill in European waters. Since the areas covered by oil spills are usually large, satellite remote sensing particularly Synthetic Aperture Radar represents an effective option for operational oil spill detection. This paper describes the development of a fully automated approach for oil spill detection from SAR. Total of 41 feature parameters extracted from each segmented dark spot for oil spill and 'look-alike' classification and ranked according to their importance. The classification algorithm is based on a two-stage processing that combines classification tree analysis and fuzzy logic. An initial evaluation of this methodology on a large dataset has been carried out and degree of agreement between results from proposed algorithm and human analyst was estimated between 85% and 93% respectively for ENVISAT and RADARSAT. PMID:23790462

Singha, Suman; Vespe, Michele; Trieschmann, Olaf

2013-08-15

370

An earth and ocean SAR for Space Shuttle - User requirements and data handling implications. [Synthetic Aperture Radar  

NASA Technical Reports Server (NTRS)

A brief summary is presented of user requirements for the Shuttle synthetic aperture radar (SAR) to be flown on a sortie mission of 7 to 10 days in duration, based on information collected from survey of the literature and direct user contacts. This information suggests selection of a dual frequency (L and X band) dual polarization SAR capable of meeting most user requirements. Particular attention is given to the SAR system specifications and the data handling capability expected to be available during the 1980s for the tracking and data relay satellite system (TDRSS). The data link requirements of the majority of Shuttle experiments will eventually determine whether the necessary high-capacity Shuttle-TDRSS return link will be part of the intrinsic Shuttle capability or will be part of the SAR payload.

Cohen, E. A.; Mehlis, J. G.; Jordan, R. L.; Brown, W. E., Jr.; Rouse, J. W., Jr.

1975-01-01

371

Detection of linear features in synthetic-aperture radar images by use of the localized Radon transform and prior information.  

PubMed

A new linear-features detection method is proposed for extracting straight edges and lines in synthetic-aperture radar images. This method is based on the localized Radon transform, which produces geometrical integrals along straight lines. In the transformed domain, linear features have a specific signature: They appear as strongly contrasted structures, which are easier to extract with the conventional ratio edge detector. The proposed method is dedicated to applications such as geographical map updating for which prior information (approximate length and orientation of features) is available. Experimental results show the method's robustness with respect to poor radiometric contrast and hidden parts and its complementarity to conventional pixel-by-pixel approaches. PMID:14735946

Onana, Vincent-de-Paul; Trouvé, Emmanuel; Mauris, Gilles; Rudant, Jean-Paul; Tonyé, Emmanuel

2004-01-10

372

Review of the NASA\\/JPL airborne synthetic aperture radar system  

Microsoft Academic Search

AIRSAR has served as a test-bed for both imaging radar techniques and radar technologies for over a decade. In fact, the polarimetric, cross-track interferometric, and along-track interferometric radar techniques were all developed using AIRSAR. We present the up-to-date system configuration, the expected performance and data accuracy in the standard radar modes.

Yunling Lou

2002-01-01

373

Analysis of Data Acquired by Synthetic Aperture Radar and LANDSAT Multispectral Scanner over Kershaw County, South Carolina, During the Summer Season.  

National Technical Information Service (NTIS)

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,...

S. T. Wu

1983-01-01

374

Transmission of information from large groups of sensors using synthetic aperture radar and modulated reradiation, and, Quasi-regular LDPC code design for QAM constellations  

Microsoft Academic Search

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

Srinivas V. Vanjari

2006-01-01

375

MODELING COLLAPSE CHIMNEY AND SPALL ZONE SETTLEMENT AS A SOURCE OF POST-SHOT SUBSIDENCE DETECTED BY SYNTHETIC APERTURE RADAR INTERFEROMETRY  

Microsoft Academic Search

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

William Foxall

376

Remote sensing of vegetation and flooding on Magela Creek Floodplain (Northern Territory, Australia) with the SIR-C synthetic aperture radar  

Microsoft Academic Search

The potential of using synthetic aperture radar (SAR) imagery to study seasonal variations in floodplain inundation and accompanying changes in herbaceous plant communities was assessed for aquatic environments in the Kakadu region of northern Australia. Dual wavelength (C- and L-band), co- and cross-polarized (HH and HV) SAR imagery of the floodplain of Magela Creek, a tributary of the East Alligator

L. L. Hess; J. M. Melack

2003-01-01

377

Using ship wake patterns to evaluate SAR (Synthetic Aperture Radar) ocean wave imaging mechanisms. Joint US-Canadian Ocean Wave Investigation Project  

Microsoft Academic Search

The Joint Ocean Wave Investigation Project (JOWIP) was conducted to evaluate the detectability of ocean wave structures on imaging synthetic aperture radar (SAR). This project used Kelvin surface ship wake patterns generated under controlled and well documented surface environmental conditions to isolate SAR image parameters. Use of waves of known wavelength and direction provide the opportunity to evaluate the SAR

R. R. Hammond; R. R. Buntzen; E. E. Floren

1985-01-01

378

Modeling Collapse Chimney and Spall Zone Settlement as a Source of Post-Shot Subsidence Detected by Synthetic Aperture Radar Interferometry  

Microsoft Academic Search

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

Foxwall

2000-01-01

379

Observation of hurricane-generated ocean swell refraction at the Gulf Stream north wall with the RADARSAT-1 synthetic aperture radar  

Microsoft Academic Search

We analyze the refraction of long oceanic waves at the Gulf Stream's north wall off the Florida coast as observed in imagery obtained from the RADARSAT-1 synthetic aperture radar (SAR) during the passage of Hurricane Bonnie on August 25, 1998. The wave spectra are derived from RADARSAT-1 SAR images from both inside and outside the Gulf Stream. From the image

Xiaofeng Li; William G. Pichel; Mingxia He; Sunny Y. Wu; Karen S. Friedman; Pablo Clemente-Colón; Chaofang Zhao

2002-01-01

380

Satellite synthetic aperture radar detection of Delaware Bay plumes: Jet-like feature analysis  

Microsoft Academic Search

From the physics of radar imaging of ocean surface processes a theoretical model for the radar imaging of an ocean jet was derived. The theoretical model predicts that the jet current structure, sech2?, constitutes a determining factor for the radar image. The modeled image intensity depends on the axial velocity, decreasing as x?1 along the jet axis, and is sensitive

Quanan Zheng; Pablo Clemente-Colón; Xiao-Hai Yan; W. Timothy Liu; Norden E. Huang

2004-01-01

381

Detection of aquifer system compaction and land subsidence using interferometric synthetic aperture radar, Antelope Valley, Mojave Desert, California  

USGS Publications Warehouse

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.

Galloway, D. L.; Hudnut, K. W.; Ingebritsen, S. E.; Phillips, S. P.; Peltzer, G.; Rogez, F.; Rosen, P. A.

1998-01-01

382

Investigating ground deformation and subsidence in northern Metro Manila, Philippines using Persistent Scatterer Interferometric Synthetic Aperture Radar (PSInSAR)  

NASA Astrophysics Data System (ADS)

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.

Eco, R. C.; Lagmay, A. A.; Bato, M. P.

2011-12-01

383

Statistical properties of L-band sea clutter measured with a polarimetric synthetic aperture radar  

Microsoft Academic Search

The limiting factor affecting the performance of most airborne radar systems in detecting targets on or near the surface of the sea is return echoes from the sea surface or sea clutter. The objective of this paper is to provide an analysis of the statistics of Australian sea clutter for an L-band VV-polarised airborne radar system from sampled measured values.

Poh Lian Choong

2001-01-01

384

Differential synthetic aperture radar interferometry for landslide monitoring: a priori GIS based assessment of feasibility  

NASA Astrophysics Data System (ADS)

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.

Plank, S.; Singer, J.; Minet, Ch.; Thuro, K.

2012-04-01

385

Partially Adaptive Phased Array Fed Cylindrical Reflector Technique for High Performance Synthetic Aperture Radar System  

NASA Technical Reports Server (NTRS)

Spaceborne microwave radar instruments demand a high-performance antenna with a large aperature to address key science themes such as climate variations and predictions and global water and energy cycles.

Hussein, Z.; Hilland, J.

2001-01-01

386

Heliradar: A Rotating Antenna Synthetic Aperture Radar for Helicopter Allweather Operations.  

National Technical Information Service (NTIS)

Today, available radar instruments cannot be applied for flight guidance purposes due to lack of resolution and ground elevation information. On the other side, optical sensors such as infrared systems provide an excellent resolution but are nearly blind ...

W. Kreitmair-steck A. P. Wolframm

1995-01-01

387

Three dimensional surface displacement of the Sichuan earthquake (Mw 7.9, China) from Synthetic Aperture Radar.  

NASA Astrophysics Data System (ADS)

The Sichuan earthquake, Mw 7.9, struck the Longmen Shan range front, in the western Sichuan province, China, on 12 May 2008. It severely affected an area where little historical seismicity and little or no significant active shortening were reported before the earthquake (e.g. Gu et al., 1989; Chen et al., 1994; Gan et al., 2007). The Longmen Shan thrust system bounds the eastern margin of the Tibetan plateau and is considered as a transpressive zone since Triassic time that was reactivated during the India-Asia collision (e.g., Tapponnier and Molnar, 1977, Chen and Wilson 1996; Arne et al., 1997, Godard et al., 2009). However, contrasting geological evidences of sparse thrusting and marked dextral strike-slip faulting during the Quaternary along with high topography (Burchfiel et al., 1995; Densmore et al., 2007) have led to models of dynamically driven and sustained topography (Royden et al., 1997) limiting the role of earthquakes in relief building and leaving the mechanism of long term strain distribution in this area as an open question. Here we combine C and L band Synthetic Aperture Radar (SAR) offsets data from ascending and descending paths to retrieve the three dimensional surface displacement distribution all along the earthquake ruptures of the Sichuan earthquake. For the first time on this earthquake we present near field 3D co-seismic surface displacement, which is an important datum for constraining modelled fault geometry at depth. Our results complement other Interferometric Synthetic Aperture Radar (InSAR) and field analyses in indicating that crustal shortening is one of the main drivers for topography building in the Longmen Shan (Liu-Zeng, 2009; Shen et al., 2009; Hubbard and Shaw, 2009). Moreover, our results put into evidence a small but significant amount of displacement in the range front that we interpret as due to slip at depth on a blind structure. We verify this hypothesis by inverting the data against a simple elastic dislocation model. We discuss this result and its implications for understanding strain partitioning during the Sichuan earthquake.

de Michele, Marcello; Raucoules, Daniel; de Sigoyer, Julia; Pubellier, Manuel; Lasserre, Cecile; Pathier, Erwan; Klinger, Yann; van der Woerd, Jerome; Chamot-Rooke, Nicolas

2010-05-01

388

Spotlight-mode synthetic aperture radar processing for high-resolution lunar mapping  

Microsoft Academic Search

During the 2008-2009 year, the Goldstone Solar System Radar was upgraded to support radar mapping of the lunar poles at 4 m resolution. The finer resolution of the new system and the accompanying migration through resolution cells called for spotlight, rather than delay-Doppler, imaging techniques. A new pre-processing system supports fast-time Doppler removal and motion compensation to a point. Two

Leif Harcke; Lawrence Weintraub; Sang-Ho Yun; Richard Dickinson; Eric Gurrola; Scott Hensley; Nicholas Marechal

2010-01-01

389

SAR (Synthetic Aperture Radar). Earth observing system. Volume 2F: Instrument panel report  

NASA Technical Reports Server (NTRS)

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.

1987-01-01

390

Automatic position calculating imaging radar with low-cost synthetic aperture sensor for imaging layered media  

DOEpatents

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.

Mast, J.E.

1998-08-18

391

Automatic position calculating imaging radar with low-cost synthetic aperture sensor for imaging layered media  

DOEpatents

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.

Mast, Jeffrey E. (Livermore, CA)

1998-01-01

392

Inverse synthetic aperture radar imagery of a man with a rocket propelled grenade launcher  

NASA Astrophysics Data System (ADS)

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.

Tran, Chi N.; Innocenti, Roberto; Kirose, Getachew; Ranney, Kenneth I.; Smith, Gregory

2004-08-01

393

High-resolution wind fields from synthetic aperture radars and numerical models for offshore wind farming  

Microsoft Academic Search

All European countries with shallow coastal waters and strong mean wind speed at the coast have begun planning and construction of offshore wind farms, and large parts of the North Sea and the Baltic are under investigation as to whether they are suitable for offshore parks. This paper demonstrates how satellite images taken by spaceborne radar sensors can be used

S. Lehner; J. Horstmann; C. Hasager

2003-01-01

394

Data-Level Fusion of Multilook Inverse Synthetic Aperture Radar Images  

Microsoft Academic Search

Although techniques for resolution enhancement in single-aspect radar imaging have made rapid progress in recent years, it does not necessarily imply that such enhanced images will improve target identification or recognition. However, when multiple looks of the same target from different aspects are obtained, the available knowledge increases, allowing more useful target information to be extracted. Physics-based image fusion techniques

Zhixi Li; Scott Papson; Ram M. Narayanan

2008-01-01

395

Data Level Fusion of Multilook Inverse Synthetic Aperture Radar (ISAR) Images  

Microsoft Academic Search

Although techniques for resolution enhancement in single-aspect radar imaging have made rapid progress in recent years, it does not necessarily imply that such enhanced images will improve target identification or recognition. However, when multiple looks of the same target from different aspects are obtained, the available knowledge base increases allowing more useful target information to be extracted. Physics based image

Zhixi Li; Ram M. Narayanan

2006-01-01

396

Orbital Synthetic Aperture Radar (SAR) for Mars Post Sample Return Exploration  

NASA Technical Reports Server (NTRS)

A Mars orbital radar mission would use two frequencies to map the planet at 50 m resolution, penetrating 5-10 m. Some areas will be imaged at 5-m resolution. A 50-m resolution topographic map will be acquired, and surface changes detected.

Thompson, T. W.; Plaut, J. J.; Arvidson, R. E.; Paillou, P.

2000-01-01

397

Project Ostrich a Feasibility Study: Detecting Buried Mines in Dry Soils Using Synthetic Aperture Radar.  

National Technical Information Service (NTIS)

Metallic and nonmetallic mines were utilized to construct a minefield in arid soil at Twentynine Palms, California to assess the extent to which long-wavelength radar could be used to detect buried mines by remote sensing. Surface and subsurface mines wer...

J. V. Hansen J. Ehlen T. D. Evans R. A. Hevenor

1993-01-01

398

Determining the Vertical Pattern of a Spaceborne SAR (Synthetic Aperture Radar) by Observation of Uniform Targets.  

National Technical Information Service (NTIS)

Pattern measurements were made for SIR-B antenna while it was in space by use of ground receivers. The measurements were supplemented by using the radar signal returned from large homogeneous areas of the surface. Results indicate that the beam is slightl...

R. K. Moore V. S. Frost H. Westmoreland D. Frank M. Hemmat

1986-01-01

399

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

Microsoft Academic Search

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),

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

2000-01-01

400

Coseismic deformation of the 2001 Mw = 7.8 Kokoxili earthquake in Tibet, measured by synthetic aperture radar interferometry  

NASA Astrophysics Data System (ADS)

The 14 November 2001, Mw = 7.8, Kokoxili earthquake ruptured more than 400 km of the westernmost stretch of the left-lateral Kunlun fault in northern Tibet. Interferometric synthetic aperture radar data from descending orbits, along four adjacent tracks covering almost the entire rupture, and 1-m pixel Ikonos satellite images are used to map the rupture geometry and the surface displacements produced by the event. Interferograms are then inverted to solve for coseismic slip on the fault at depth. The radar data show that the rupture connected the Heituo fault, where the earthquake initiated, to the main Kunlun fault, cutting across a pull-apart trough in between the two strike-slip faults. The fault model includes two vertical sections extending to a depth of 20 km and discretized into 5 km × 5 km patches. Using a nonnegative least squares method that includes an appropriate degree of smoothing, we solve for the left-lateral slip on each fault patch. Our solution shows that the largest slip occurred at depths between 0 and 5 km, reaching ?8 m in two areas, 200 and 250 km east of the earthquake epicenter. Significant slip took place below 10 km at both ends of the rupture. Slip appears to have been highly variable along the fault, defining six sections of major moment release. These sections correspond to six subsegments of the Kunlun fault system, defined from the surface morphology of the fault. This suggests that fault geometry exerted a predominant influence on controlling the rupture propagation.

Lasserre, C.; Peltzer, G.; Crampé, F.; Klinger, Y.; van der Woerd, J.; Tapponnier, P.

2005-12-01

401

Small-scale deformations associated with the 1992 Landers, California, earthquake mapped by synthetic aperture radar interferometry phase gradients  

NASA Astrophysics Data System (ADS)

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.

Price, Evelyn J.; Sandwell, David T.

1998-11-01

402

Forest height estimation from mountain forest areas using general model-based decomposition for polarimetric interferometric synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

The estimation of forest parameters over mountain forest areas using polarimetric interferometric synthetic aperture radar (PolInSAR) images is one of the greatest interests in remote sensing applications. For mountain forest areas, scattering mechanisms are strongly affected by the ground topography variations. Most of the previous studies in modeling microwave backscattering signatures of forest area have been carried out over relatively flat areas. Therefore, a new algorithm for the forest height estimation from mountain forest areas using the general model-based decomposition (GMBD) for PolInSAR image is proposed. This algorithm enables the retrieval of not only the forest parameters, but also the magnitude associated with each mechanism. In addition, general double- and single-bounce scattering models are proposed to fit for the cross-polarization and off-diagonal term by separating their independent orientation angle, which remains unachieved in the previous model-based decompositions. The efficiency of the proposed approach is demonstrated with simulated data from PolSARProSim software and ALOS-PALSAR spaceborne PolInSAR datasets over the Kalimantan areas, Indonesia. Experimental results indicate that forest height could be effectively estimated by GMBD.

Minh, Nghia Pham; Zou, Bin; Cai, Hongjun; Wang, Chengyi

2014-01-01

403

Mapping Hydrologically Sensitive Areas on the Boreal Plain: A Multi-Temporal Analysis of ERS Synthetic Aperture Radar Data  

NASA Astrophysics Data System (ADS)

Knowledge of the spatial and temporal dynamics of hydrologically sensitive areas (HSAs) is vital to a wide range of land management decisions. HSAs are defined as both permanently or transiently wet (saturated or inundated) areas. These hydrologic features play a fundamental role in the water cycle and are important in regulating the movement of nutrients and biota within the landscape. However, characterizing the spatial and temporal dynamics of these hydrologic features at scales relevant to resource managers has proven to be a difficult task. Conventional in-situ hydrological measurements adequate to capture the spatial and temporal complexities of a regional landscape would be prohibitively expensive and, therefore, alternative methods are needed. This study presents a remote sensing approach that uses archived ERS-1 and ERS-2 Synthetic Aperture Radar (SAR) images to monitor HSAs in the Willow River watershed (1000 km2) on the western Boreal Plain of Canada. The ERS images were used to generate a probability of HSA occurrence map for a 10-year period (1991-2000). This map revealed the complexity of HSAs on the western Boreal Plain, indicating that some areas remained consitently dry or wet, while some areas were dynamic, wetting and drying and vice versa. The HSA probability map provides information on the spatial and temporal dynamics of HSAs that is currently unavailable for this region.

Clark, R. B.; Creed, I. F.

2006-12-01

404

Design and implementation of a Synthetic Aperture Radar for Open Skies (SAROS) aboard a C-135 aircraft  

SciTech Connect

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.

Cooper, D.W.; Murphy, M. [Sandia National Labs., Albuquerque, NM (United States); Rimmel, G. [Loral Defense Systems, Litchfield, AZ (United States)

1994-08-01

405

Synthetic aperture radar imagery of airports and surrounding areas: Study of clutter at grazing angles and their polarimetric properties  

NASA Technical Reports Server (NTRS)

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.

Onstott, Robert G.; Gineris, Denise J.; Clinthorne, James T.

1991-01-01

406

Method for detecting surface motions and mapping small terrestrial or planetary surface deformations with synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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.

Gabriel, Andrew K. (inventor); Goldstein, Richard M. (inventor); Zebker, Howard A. (inventor)

1990-01-01

407

Off-line processing of ERS-1 synthetic aperture radar data with high precision and high throughput  

NASA Technical Reports Server (NTRS)

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.

Gredel, J.; Markwitz, W.; Noack, W.; Schreier, G.

1986-01-01

408

Coastal flood inundation monitoring with Satellite C-band and L-band Synthetic Aperture Radar data  

USGS Publications Warehouse

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).

Ramsey, Elijah, III; Rangoonwala, Amina; Bannister, Terri

2013-01-01

409

Wave-current interaction study in the Gulf of Alaska for detection of eddies by synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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.

Liu, Antony K.; Peng, Chich Y.; Schumacher, James D.

1994-01-01

410

Patterns of irrigated rice growth and malaria vector breeding in Mali using multi-temporal ERS-2 synthetic aperture radar  

PubMed Central

We explored the use of the European Remote Sensing Satellite 2 Synthetic Aperture Radar (ERS-2 SAR) to trace the development of rice plants in an irrigated area near Niono, Mali and relate that to the density of anopheline mosquitoes, especially An. gambiae. This is important because such mosquitoes are the major vectors of malaria in sub-Saharan Africa, and their development is often coupled to the cycle of rice development. We collected larval samples, mapped rice fields using GPS and recorded rice growth stages simultaneously with eight ERS-2 SAR acquisitions. We were able to discriminate among rice growth stages using ERS-2 SAR backscatter data, especially among the early stages of rice growth, which produce the largest numbers of larvae. We could also distinguish between basins that produced high and low numbers of anophelines within the stage of peak production. After the peak, larval numbers dropped as rice plants grew taller and thicker, reducing the amount of light reaching the water surface. ERS-2 SAR backscatter increased concomitantly. Our data support the belief that ERS-2 SAR data may be helpful for mapping the spatial patterns of rice growth, distinguishing different agricultural practices, and monitoring the abundance of vectors in nearby villages.

Diuk-Wasser, M. A.; Dolo, G.; Bagayoko, M.; Sogoba, N.; Toure, M. B.; Moghaddam, M.; Manoukis, N.; Rian, S.; Traore, S. F.; Taylor, C. E.

2007-01-01

411

Delineation of inundated area and vegetation along the Amazon floodplain with the SIR-C synthetic aperture radar  

SciTech Connect

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.

Hess, L.L.; Melack, J.M.; Filoso, S. [Univ. of California, Santa Barbara, CA (United States)] [Univ. of California, Santa Barbara, CA (United States); Wang, Y. [Univ. of California, Santa Barbara, CA (United States). Inst. for Computational Earth System Science] [Univ. of California, Santa Barbara, CA (United States). Inst. for Computational Earth System Science; [East Carolina Univ., Greenville, NC (United States). Dept. of Geography

1995-07-01

412

Comparative analysis for detecting areas with building damage from several destructive earthquakes using satellite synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

Earthquakes that have caused large-scale damage in developed areas, such as the 1994 Northridge and 1995 Kobe events, remind us of the importance of making quick damage assessments in order to facilitate the resumption of normal activities and restoration planning. Synthetic aperture radar (SAR) can be used to record physical aspects of the Earth's surface under any weather conditions, making it a powerful tool in the development of an applicable method for assessing damage following natural disasters. Detailed building damage data recorded on the ground following the 1995 Kobe earthquake may provide an invaluable opportunity to investigate the relationship between the backscattering properties and the degree of damage. This paper aims to investigate the differences between the backscattering coefficients and the correlations derived from pre- and post-earthquake SAR intensity images to smoothly detect areas with building damage. This method was then applied to SAR images recorded over the areas affected by the 1999 Kocaeli earthquake in Turkey, the 2001 Gujarat earthquake in India, and the 2003 Boumerdes earthquake in Algeria. The accuracy of the proposed method was examined and confirmed by comparing the results of the SAR analyses with the field survey data.

Matsuoka, Masashi; Yamazaki, Fumio

2010-11-01

413

Lithology-controlled subsidence and seasonal aquifer response in the Bandung basin, Indonesia, observed by synthetic aperture radar interferometry  

NASA Astrophysics Data System (ADS)

Land subsidence in the Bandung basin, West Java, Indonesia, is characterized based on differential interferometric synthetic aperture radar (DInSAR) and interferometric point target analysis (IPTA). We generated interferograms from 21 ascending SAR images over the period 1 January 2007 to 3 March 2011. The estimated subsidence history shows that subsidence continuously increased reaching a cumulative 45 cm during this period, and the linear subsidence rate reached ?12 cm/yr. This significant subsidence occurred in the industrial and densely populated residential regions of the Bandung basin where large amounts of groundwater are consumed. However, in several areas the subsidence patterns do not correlate with the distribution of groundwater production wells and mapped aquifer degradation. We conclude that groundwater production controls subsidence, but lithology is a counteracting factor for subsidence in the Bandung basin. Moreover, seasonal trends of nonlinear surface deformations are highly related with the variation of rainfall. They indicate that there is elastic expansion (rebound) of aquifer system response to seasonal-natural recharge during rainy season.

Khakim, Mokhamad Yusup Nur; Tsuji, Takeshi; Matsuoka, Toshifumi

2014-10-01

414

Analysis of SAR Image Quality Degradation due to Pointing and Stability Error of Synthetic Aperture Radar Satellite  

NASA Astrophysics Data System (ADS)

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.

Chun, Yong Sik; Ra, Sung Woong

2008-12-01

415

Integration of speckle de-noising and image segmentation using Synthetic Aperture Radar image for flood extent extraction  

NASA Astrophysics Data System (ADS)

Flood is one of the detrimental hydro-meteorological threats to mankind. This compels very efficient flood assessment models. In this paper, we propose remote sensing based flood assessment using Synthetic Aperture Radar (SAR) image because of its imperviousness to unfavourable weather conditions. However, they suffer from the speckle noise. Hence, the processing of SAR image is applied in two stages: speckle removal filters and image segmentation methods for flood mapping. The speckle noise has been reduced with the help of Lee, Frost and Gamma MAP filters. A performance comparison of these speckle removal filters is presented. From the results obtained, we deduce that the Gamma MAP is reliable. The selected Gamma MAP filtered image is segmented using Gray Level Co-occurrence Matrix (GLCM) and Mean Shift Segmentation (MSS). The GLCM is a texture analysis method that separates the image pixels into water and non-water groups based on their spectral feature whereas MSS is a gradient ascent method, here segmentation is carried out using spectral and spatial information. As test case, Kosi river flood is considered in our study. From the segmentation result of both these methods are comprehensively analysed and concluded that the MSS is efficient for flood mapping.

Senthilnath, J.; Shenoy, H. Vikram; Rajendra, Ritwik; Omkar, S. N.; Mani, V.; Diwakar, P. G.

2013-06-01

416

Atmospheric corrections in interferometric synthetic aperture radar surface deformation - a case study of the city of Mendoza, Argentina  

NASA Astrophysics Data System (ADS)

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.

Balbarani, S.; Euillades, P. A.; Euillades, L. D.; Casu, F.; Riveros, N. C.

2013-09-01

417

First-year sea ice spring melt transitions in the Canadian Arctic Archipelago from time-series synthetic aperture radar data, 1992–2002  

Microsoft Academic Search

This paper synthesizes 10-years' worth of interannual time-series space-borne ERS-1 and RADARSAT-1 synthetic aperture radar (SAR) data collected coincident with daily measurement of snow-covered, land-fast first-year sea ice (FYI) geophysical and surface radiation data collected from the Seasonal Sea Ice Monitoring and Modeling Site, Collaborative-Interdisciplinary Cryospheric Experiment and 1998 North Water Polynya study over the period 1992 to 2002. The

J. J. Yackel; D. G. Barber; T. N. Papakyriakou; C. Breneman

2007-01-01

418

Remote sensing of vegetation and flooding on Magela Creek Floodplain (Northern Territory, Australia) with the SIR-C synthetic aperture radar  

Microsoft Academic Search

\\u000a The potential of using synthetic aperture radar (SAR) imagery to study seasonal variations in floodplain inundation and accompanying\\u000a changes in herbaceous plant communities was assessed for aquatic environments in the Kakadu region of northern Australia.\\u000a Dual wavelength (C- and L-band), co- and cross-polarized (HH and HV) SAR imagery of the floodplain of Magela Creek, a tributary\\u000a of the East Alligator

L. L. Hess; J. M. Melack

419

Methods of obtaining offshore wind direction and sea-state data from X-band aircraft SAR (Synthetic Aperture Radar) imagery of coastal waters  

Microsoft Academic Search

X-band synthetic aperture radar (SAR) imagery of the Goto Islands of Japan was digitally analyzed to extract air-sea interaction parameters and to assess the potential of texture measures in analysis of SAR ocean imagery. Wind direction is extracted from wind rows, wind streaks, and random turbulence patterns observed in the SAR imagery. Sea-state parameters are either extracted directly from the

G. A. Mastin; C. A. Harlow; O. K. Huh; S. A. Hsu

1985-01-01

420

Ground deformation due to tectonic, hydrothermal, gravity, hydrogeological, and anthropic processes in the Campania Region (Southern Italy) from Permanent Scatterers Synthetic Aperture Radar Interferometry  

Microsoft Academic Search

We apply the Permanent Scatterers Synthetic Aperture Radar Interferometry (PS-InSAR) technique to the Campania Region (Southern Italy), which includes the Southern Apennines chain and Plio-Quaternary structural depressions, with the aim to detect ground displacements at a regional scale. The study area, which extends for 13,600 km2, is characterized by intense urbanization, active volcanoes (Phlegraean Fields, Vesuvius and Ischia), seismogenic structures, landslides,

G. Vilardo; G. Ventura; C. Terranova; F. Matano; S. Nardò

2009-01-01

421

Melt ponds on sea ice in the Canadian Archipelago 2. On the use of RADARSAT-1 synthetic aperture radar for geophysical inversion  

Microsoft Academic Search

Microwave scattering from a first-year sea ice (FYI) melt ponded surface is examined using RADARSAT-1 synthetic aperture radar (SAR) data collected during the 1997 Collaborative-Interdisciplinary Cryospheric Experiment (C-ICE'97) near Resolute Bay, Nunavut. This paper (1) investigates the utility of time series of microwave scattering to detect melt pond formation and (2) investigates approaches toward geophysically inverting information on the physical

J. J. Yackel; D. G. Barber

2000-01-01

422

Analysis of two Seasat synthetic aperture radar images of an urban scene  

NASA Technical Reports Server (NTRS)

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.

Bryan, M. L.

1982-01-01

423

Interferometric Baseline Performance Estimations for Multistatic Synthetic Aperture Radar Configurations Derived from GRACE GPS Observations  

Microsoft Academic Search

Recent studies have demonstrated the usefulness of global positioning system (GPS) receivers for relative positioning of formation-flying satellites using dual-frequency carrier-phase observations. The accurate determination of distances or baselines between satellites flying in formation can provide significant benefits to a wide area of geodetic studies. For spaceborne radar interferometry in particular, such measurements will improve the accuracy of interferometric products

A. O. Kohlhase; R. Kroes; S. D’Amico

2006-01-01

424

The derivation of sub-canopy surface terrain models of coastal forests using synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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.

Imhoff, M. L.; Gesch, D. B.

1988-01-01

425

Phase noise from aircraft motion: Compensation and effect on synthetic aperture radar images  

NASA Technical Reports Server (NTRS)

Image degradation of airborne SAR imagery caused by phase errors introduced in the received signal by aircraft motion is discussed. Mechanical motion has a small bandwidth and does not affect the range signal, where the total echo time is typically 60 microsec. However, since the aperture length can be several seconds, the synthesized azimuth signal can have significant errors of which phase noise is the most important. An inertial navigation system can be used to compensate for these errors when processing the images. Calculations to evaluate how much improvement results from compensation are outlined.

Gabriel, Andrew K.; Goldstein, Richard M.

1986-01-01

426

Seasat synthetic aperture radar ( SAR) response to lowland vegetation types in eastern Maryland and Virginia.  

USGS Publications Warehouse

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 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.-from Authors

Krohn, M. D.; Milton, N. M.; Segal, D. B.

1983-01-01

427

Maximum a posteriori classification of multifrequency, multilook, synthetic aperture radar intensity data  

NASA Technical Reports Server (NTRS)

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.

Rignot, E.; Chellappa, R.

1993-01-01

428

BATHYMETRIC IMAGING USING SYNTHETIC APERTURE SONAR  

Microsoft Academic Search

Synthetic aperture sonar imaging is based on coherent combination of a sequence of recorded sonar returns. This method, which is extensively used in radar imaging, synthesises one long antenna and thus achieves high along track resolution. Stable platform motion combined with an accurate estimation of the trajectory is necessary to avoid defocus in the images. This makes autonomous underwater vehicles

T. O. Sæbø; R. E. Hansen

2004-01-01

429

The evolution of synthetic aperture radar systems and their progression to the EOS SAR  

NASA Technical Reports Server (NTRS)

The authors describe the evolution of the spaceborne imaging radar starting with the Seasat SAR, through the SIR-A, SIR-B, and SIR-C/X-SAR missions, to the Earth Observing System (EOS) SAR which is scheduled for launch as part of EOS in the late 1990s. A summary of the planned international missions, which may produce a permanent active microwave capability in space starting as early as 1991, is also presented, along with a description of the airborne systems which will be essential to the algorithm development and long-term calibration of the spaceborne data. A brief summary of the planetary missions utilizing SAR and a comparison of their imaging capabilities with those available on Earth are presented.

Way, Jobea; Smith, Elizabeth A.

1991-01-01

430

Seasat synthetic aperture radar /SAR/ response to lowland vegetation types in eastern Maryland and Virginia  

NASA Technical Reports Server (NTRS)

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.

Krohn, M. D.; Milton, N. M.; Segal, D. B.

1983-01-01

431

Image-focus quality indicators for efficient inverse synthetic aperture radar phase correction  

NASA Astrophysics Data System (ADS)

In this paper we formalize a theory for indicators designed to focus ISAR imagery of non-cooperative targets. These indicators represent variations of the Fisher information and entropy measures, and are capable of operating either in the spatial-frequency domain or in the spatial domain. This freedom of choice is advantageous since the information on the target's representation in either domain has phase and magnitude components, which can be efficiently exploited to resolve and focus the target's primary elements. These elements are displayed as radar cross section (RCS) distribution, we propose a phase correction algorithm based on parametric models of a target's temporal maneuvers. The approach is to quantify the phase non-linearities via the Fisher information or entropy measure that is dependent on motion parameter estimates. The optimization of these parameter estimates is a m-dimensional search problem that minimizes the focus quality indicator over a prescribed tolerance for a given SNR. The coordinates of this minimum point are subsequently used to generate a phase correction factor that eliminates image blurring, thus providing better focusing for effective target recognition.

Flores, Benjamin C.; Tariq, Salim; Son, Jae Sok

1996-06-01

432

Interferometric synthetic aperture radar study of Okmok volcano, Alaska, 1992-2003: Magma supply dynamics and postemplacement lava flow deformation  

USGS Publications Warehouse

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.

Lu, Z.; Masterlark, T.; Dzurisin, D.

2005-01-01

433

Climate Change Indicator for Hazard Identification of Indian North West Coast Marine Environment Using Synthetic Aperture Radar (sar)  

NASA Astrophysics Data System (ADS)

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

Gambheer, Phani Raj

2012-07-01

434

Resurrection Of Archived Synthetic Aperture Radar Imagery For Characterizing Hydrodynamics On Boreal Landscapes  

NASA Astrophysics Data System (ADS)

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.

Sass, G. Z.; Creed, I. F.

2006-12-01

435

Analysis of polarimetric synthetic aperture radar and passive visible light polarimetric imaging data fusion for remote sensing applications  

NASA Astrophysics Data System (ADS)

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. PolS