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1

Synthetic aperture radar interferometry  

Microsoft Academic Search

Synthetic aperture radar interferometry is an imaging technique for measuring the topography of a surface, its changes over time, and other changes in the detailed characteristic of the surface. By exploiting the phase of the coherent radar signal, interferometry has transformed radar remote sensing from a largely interpretive science to a quantitative tool, with applications in cartography, geodesy, land cover

PAUL A. ROSEN; SCOTT HENSLEY; IAN R. JOUGHIN; FUK K. LI; SØREN N. MADSEN; ERNESTO RODRÍGUEZ; RICHARD M. GOLDSTEIN

2000-01-01

2

REVIEW ARTICLE Interferometric Synthetic Aperture Radar  

E-print Network

REVIEW ARTICLE Interferometric Synthetic Aperture Radar Christopher T. Allen Department of Electrical Engineering and Computer Science and Radar Systems and Remote Sensing Laboratory University of Kansas Abstract. This paper provides a brief review of interferometric synthetic aperture radar (In

Kansas, University of

3

Future of synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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

Barath, F. T.

1978-01-01

4

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

5

Distributed synthetic aperture radar simulation  

NASA Technical Reports Server (NTRS)

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

Bourgeois, B. A.

1986-01-01

6

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

7

Synthetic aperture radar calibration using reference reflectors  

Microsoft Academic Search

A simple expression for the terrain backscatter coefficient is derived in terms of the integrated power of an adjacent known radar reflector in a synthetic aperture radar (SAR) image. It is shown that this technique for SAR image calibration is independent of the radar system focus or partial coherence and thereby possesses an important advantage over the usual technique, which

A. L. Gray; P. W. Vachon; C. E. Livingstone; T. I. Lukowski

1990-01-01

8

Iterative synthetic aperture radar imaging algorithms   

E-print Network

Synthetic aperture radar is an important tool in a wide range of civilian and military imaging applications. This is primarily due to its ability to image in all weather conditions, during both the day and the night, ...

Kelly, Shaun Innes

2014-06-30

9

A butterfly algorithm for synthetic aperture radar  

E-print Network

It is not currently known if it is possible to accurately form a synthetic aperture radar image from N data points in provable near-linear complexity, where accuracy is defined as the ?? error between the full O(N²) ...

Demanet, Laurent

10

Clutter free synthetic aperture radar correlator  

NASA Technical Reports Server (NTRS)

A synthetic aperture radar correlation system including a moving diffuser located at the image plane of a radar processor is described. The output of the moving diffuser is supplied to a lens whose impulse response is at least as wide as that of the overall processing system. A significant reduction in clutter results is given.

Jain, A.

1977-01-01

11

Miniature synthetic-aperture radar system  

NASA Astrophysics Data System (ADS)

Loral Defense Systems-Arizona has developed a high-performance synthetic-aperture radar (SAR) for small aircraft and unmanned aerial vehicle (UAV) reconnaissance applications. This miniature radar, called Miniature Synthetic-Aperture Radar (MSAR), is packaged in a small volume and has low weight. It retains key features of large SAR systems, including high-resolution imaging and all-weather operation. The operating frequency of MSAR can optionally be selected to provide foliage penetration capability. Many imaging radar configurations can be derived using this baseline system. MSAR with a data link provides an attractive UAV sensor. MSAR with a real-time image formation processor is well suited to installations where onboard processing and immediate image analysis are required. The MSAR system provides high-resolution imaging for short-to-medium range reconnaissance applications.

Stockton, Wayne; Stromfors, Richard D.

1990-11-01

12

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

13

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

14

Amplitude calibration of spaceborne synthetic aperture radars. [Synthetic Aperture Radar  

NASA Technical Reports Server (NTRS)

Problems encountered during attempts to calibrate SAR imagery, recent successful experiments conducted with SEASAT SAR data, and a proposed program for the calibration and validation of the radar imagery from the forthcoming SIR-B SAR are discussed. The SEASAT SAR data for 10 passes over Death Valley, California, were processed with a modified digital correlator. The procedure included a preliminary screening of the data to check for raw data saturation, compensation of waveforms and estimation of the amplitude of the pilot tone. All data was normalized to this pilot tone signal to reduce the effects of variable gains in the data links and ground receivers. The digital correlation algorithm generated image data. Evaluation of 6 passes results in a maximum pass to pass gain variation of only 1.1 dB and a standard deviation amongst the passes of 0.35 dB. previously announced in STAR as N83-26215

Held, D. N.

1983-01-01

15

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

16

Arbitrary scene simulation for synthetic aperture radar  

NASA Astrophysics Data System (ADS)

We propose a new laboratory method for characterizing synthetic aperture radar (SAR) systems through the use of a synthetic scene generator. Flight tests are the only definitive way to characterize the system level performance of airborne synthetic aperture radar systems. However, due to the expense of flights tests it is beneficial to complete as much testing as possible in a laboratory environment before flight testing is performed. There are many existing tests that are employed to measure the performance of various subsystems in a SAR system, find defective hardware, and indicate design problems that need to be mitigated. However, certain issues can only be found on an integrated system, and laboratory testing at a system level is typically confined to characterizing the impulse response (IPR) of a single point target through the use of an optical delay line. While useful, delay line testing requires running a modified version of real-time image formation code as the delay line does not completely mimic a real target. Ideally, system level tests are performed on unmodified code. On modern SAR systems many algorithms are data driven (e.g., autofocus) and require a substantially more sophisticated data model for testing. We desire to create a complete system test by combining an arbitrary number of point targets and clutter patterns to mimic radar responses from a real scene. This capability enables complete testing of radar systems in a laboratory environment according to prescribed terrain/scene characteristics. This paper presents an overview of the system requirements for a synthetic scene generator. The analysis is limited to SAR systems utilizing chirp waveforms and stretch processing. Furthermore, we derive relationships between IF bandwidth, target position, and the phase history model. A technique to properly compensate for motion pulse to pulse is presented. Finally, our concept is demonstrated with simulation data.

Musgrove, Cameron; Naething, Richard; Schilling, John

2014-05-01

17

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.

2011-06-01

18

Cancellation of singularities for synthetic aperture radar  

NASA Astrophysics Data System (ADS)

In a basic model for synthetic aperture radar (SAR) imaging, one wishes to recover a function or distribution f from line integrals over circles whose centers lie on a given curve ?. In this paper, we consider the problem of recovering the singularities (wavefront set) of f given its SAR data, and specifically whether it is possible to choose a singular f whose singularities are hidden from ?, meaning that its SAR data is smooth. We show that f ?s singularities can be hidden to leading order if a certain discrete reflection map is the identity, and give examples where this is the case. Finally, numerical experiments illustrate the hiding of singularities.

Caday, Peter

2015-01-01

19

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

20

Multi-mission, autonomous, synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

21

Motion Measurement for Synthetic Aperture Radar.  

SciTech Connect

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

Doerry, Armin W.

2015-01-01

22

Filtered Back Projection Type Direct Edge Detection of Real Synthetic Aperture Radar Images  

E-print Network

Filtered Back Projection Type Direct Edge Detection of Real Synthetic Aperture Radar Images Noe American, Edinburg, TX 78539 USA ABSTRACT Edge detection algorithms applied to Synthetic Aperture Radar with significant results. Keywords: Synthetic Aperture Radar, Backprojection, Edge Detection, Imaging 1

Qiao, Zhijun "George" - Department of Mathematics, University of Texas

23

Eliminating Clutter in Synthetic-Aperture Radar  

NASA Technical Reports Server (NTRS)

Diffusion technique reduces clutter noise in coherent SAR (synthetic-aperature radar) image signal without degrading its resolution. Technique makes radar-mapped terrain features more obvious.It also has potential application in holographic microscopy.

Jain, A.

1979-01-01

24

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

25

Bistatic synthetic aperture radar using two satellites  

NASA Technical Reports Server (NTRS)

The paper demonstrates the feasibility of a bistatic synthetic aperture radar (BISAR) utilizing two satellites. The proposed BISAR assumes that the direction of the two narrow antenna beams are programmed to coincide over the desired area to be imaged. Functionally, the transmitter and receiver portions can be interchanged between the two satellites. The two satellites may be in one orbit plane or two different orbits such as geosynchronous and low-earth orbits. The pulse repetition frequency and imaging geometry are constrained by contours of isodops and isodels. With two images of the same area viewed from different angles, it is possible in principle to derive three-dimensional stereo images. Applications of BISAR include topography, water resource management, and soil moisture determination.. Advantages of BISAR over a monostatic SAR are mentioned, including lower transmitter power and greater ranges in incidence angle and coverage.

Tomiyasu, K.

1978-01-01

26

Research and development on synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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 off-nadir viewing (33 deg) and the pulse repetition frequency are described. The SAR antenna consists of a series of connected flat panels that will be stowed in an accordion mode for launch, then deployed on-orbit, much the same as is done with solar panels. The panels will have an Al honeycomb structure with a CFRP skin that reduces thermal stresses. Feed components are embedded in the CFRP skin. The SAR will emit in the L-band with H-H polarization.

Itoh, Yasuyuki; Hisada, Yasumasa

27

PTBS segmentation scheme for synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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

Friedland, Noah S.; Rothwell, Brian J.

1995-07-01

28

A Butterfly Algorithm for Synthetic Aperture Radar Imaging  

E-print Network

In spite of an extensive literature on fast algorithms for synthetic aperture radar (SAR) imaging, it is not currently known if it is possible to accurately form an image from N data points in provable near-linear time ...

Demanet, Laurent

29

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

30

Synthetic aperture radar imaging of moving ocean waves  

Microsoft Academic Search

A theory for the radar imaging of ocean waves is presented under the assumptions that a swell propagates through an ensemble of Bragg scatterers and that the integration time of the synthetic aperture radar (SAR) is small compared to the angular velocity of the swell. Results are prsented which show image development and distortions caused by the radial velocities and

C. T. Swift; L. Wilson

1979-01-01

31

Full Motion Compensation for LFM-CW Synthetic Aperture Radar  

E-print Network

Full Motion Compensation for LFM-CW Synthetic Aperture Radar Evan C. Zaugg and David G. Long, but in actuality a UAV or airplane will deviate, often significantly, from this ideal. This non-ideal motion can seriously degrade the SAR image quality. In a continuous wave system this motion happens during the radar

Long, David G.

32

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

33

Mapping of boreal forest biomass from spaceborne synthetic aperture radar  

Microsoft Academic Search

As part of the Boreal-Ecosystem Atmosphere Study (BOREAS), an investigation is being made of the use of satellite data including shuttle imaging radar-C (SIR-C), X-band synthetic aperture radar (XSAR), and Landsat-Thematic Mapper data for estimating total and component aboveground woody biomass in boreal forest study sites in Canada. The goal of this paper is to present progress in mapping above

K. Jon Ranson; R. H. Lang; N. S. Chauhan; R. J. Cacciola; O. Kilic; Sun Guoqing

1997-01-01

34

Antenna dimensions of synthetic aperture radar systems on satellites  

NASA Technical Reports Server (NTRS)

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

Richter, K. R.

1973-01-01

35

Multi-static synthetic aperture radar image formation  

Microsoft Academic Search

In this paper, we consider a multi-static 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 signals from multiple transmitters and the

V. P. Krishnan; J. Swoboda; C. E. Yarman; B. Yazici

2009-01-01

36

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

37

Phase statistics of interferograms with applications to synthetic aperture radar  

Microsoft Academic Search

Interferometric methods are well established in optics and radio astronomy. In recent years, interfero- metric concepts have been applied successfully to synthetic aperture radar (SAR) and have opened up new possibilities in the area of earth remote sensing. However interferometric SAR applications require thorough phase control through the imaging process. The phase accuracy of SAR images is affected by decorrelation

Dieter Just; Richard Bamler

1994-01-01

38

Airborne and spaceborne synthetic aperture radar observations of ocean waves  

Microsoft Academic Search

The Grand Banks ERS?1 synthetic aperture radar (SAR) wave spectra validation experiment took place over a study site in which intensive in situ wind and wave measurements were being taken. The unique aspect of the program was the nearly simultaneous acquisition (in space and time) of spaceborne (ESA ERS?1) and airborne (CCRS CV?580) SAR imagery of the same ocean wave

Paris W. Vachon; Harald E. Krogstad; J. Scott Paterson

1994-01-01

39

Processing of ocean wave data from a synthetic aperture radar  

Microsoft Academic Search

The usual operation of a synthetic-aperture radar (SAR) assumes that the sensor platform moves at a constant velocity along a straight line and that objects to be imaged are stationary. Moving ocean waves perturb the Doppler frequencies in the SAR phase histories, and when processed in a conventional manner, they produce images of waves that are dispersed and thus defocused

R. A. Shuchman; J. S. Zelenka

1978-01-01

40

Ice island detection and characterization with airborne synthetic aperture radar  

Microsoft Academic Search

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

M. O. Jeffries; W. M. Sackinger

1990-01-01

41

Ice sheet margin detection using ERS-1 synthetic aperture radar  

Microsoft Academic Search

A portion of the Greenland ice sheet margin near the Jakobshavn area is mapped using an automatic, hierarchical approach applied to ERS-1 synthetic aperture radar (SAR). Image tone and texture variability between the bare ice facies near the ice sheet margin and recently deglaciated rocks are used to map the ice sheet margin. This process involves integration of an anisotropic

Hong-Gyoo Sohn; Kenneth C. Jezek

1996-01-01

42

Discontinuity Adaptive MRF Model for Synthetic Aperture Radar Image Analysis  

Microsoft Academic Search

In this paper, an approach is presented for the reconstruction and analysis of synthetic aperture radar (SAR) images that preserves better fine structures and borders in the image than classical methods, The method uses the discontinuity adaptive MRF model proposed by Li [1] in combination which an observation model that exploits a gamma distribution. This resulted in a new algorithm

Paul C. Smits; Silvana G. Dellepiane; Gianni Vernazza

1997-01-01

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

Integrated design of synthetic aperture radars for unmanned aircraft  

Microsoft Academic Search

The use of synthetic aperture radar (SAR) on unmanned aircraft (UAVs) is often contemplated for aerial observation of regions where unmanned, long duration (tens of hours) observations are advantageous. Some current applications are severe weather, military surveillance and environmental observations. However, in most cases the initial SAR and aircraft designs are done independently and one is either trying to design

J. F. Vesecky; J. M. Cornwall

1996-01-01

45

New military uses for synthetic aperture radar (SAR)  

NASA Astrophysics Data System (ADS)

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

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

1993-02-01

46

Soil-penetrating synthetic aperture radar  

SciTech Connect

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

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

1994-12-01

47

Theory and design of interferometric synthetic aperture radars  

Microsoft Academic Search

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

E. Rodriguez; J. M. Martin

1992-01-01

48

Studies of multibaseline spaceborne interferometric synthetic aperture radars  

Microsoft Academic Search

The authors have utilized a set of Seasat synthetic aperture radar (SAR) data that were obtained in nearly repeat ground-track orbits to demonstrate the performance of spaceborne interferometric SAR (INSAR) systems. An assessment of the topography measurement capability is presented. A phase measurement error model is described and compared with the data obtained at various baseline separations and signal-to-noise ratios.

FUK K. LI; R. M. Goldstein

1990-01-01

49

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

50

Underground focusing spotlight synthetic aperture radar for tunnel detection applications  

Microsoft Academic Search

This work studies the concept of a underground focusing plane-based synthetic aperture radar (UF-SL-SAR) by analyzing two different scenarios. The first scenario is a sandy, non-dispersive, homogeneous and rough soil. In this case successful underground focusing can be performed and the scattered field produced by the tunnel just above the rough surface dominates that of by the rough ground surface

Jose A. Martinez-Lorenzo; Carey Rappaport

2009-01-01

51

Sensitivity of synthetic aperture radar boresight orientation to orbit parameters  

NASA Technical Reports Server (NTRS)

Attendant upon the use of synthetic aperture radar (SAR) in upcoming planetary missions, is the need to assess errors in the pointing angles of the instrument boresight due to spacecraft ephemeris errors. Developed herein are the constrained analytic partials of these boresight angles not only with respect to a motion-related, cartesian frame but also with respect to classical orbital elements. While both systems have great utility for spacecraft based instruments, the former system should prove useful for SAR instruments on aircraft.

Russell, R. K.; San Martin, A. M.; Jin, M.

1986-01-01

52

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

53

Design of a millimetre Synthetic Aperture Radar (SAR) onboard UAV's  

Microsoft Academic Search

This paper describes the design for an experimental short-range (2 Km) high-resolution (30??30 cm2) Synthetic Aperture Radar (SAR) sensor in the millimetre wave band to take it onboard Unmanned Aerial Vehicles (UAV). The novelty lies on the establishment of new and very demanding requirements induced by the need of being onboard low cost aerial platforms and so, susceptible of been

Raquel Ruiz Saldaña; Félix Pérez Martínez

2007-01-01

54

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

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

1993-05-01

55

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

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

1993-05-01

56

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

57

Probing the Martian Subsurface with Synthetic Aperture Radar  

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

58

Considerations on data compression of synthetic aperture radar images  

NASA Technical Reports Server (NTRS)

This paper describes some analytical results relative to the effectiveness of applying data compression techniques for efficient transmission of synthetic aperture radar (SAR) signals and images. A Rayleigh target model is assumed in the analysis. It is also assumed that all surface reflectivity information is of interest and needs to be transmitted. Spectral characteristics of radar echo signals and processed images are analyzed. Analytical results generally indicate that due to the lack of high spatial correlation in the Rayleigh distributed radar surface reflectivity, application of data compression to SAR signals and images under the square difference fidelity criterion may be less effective than its application to images obtained using incoherent illumination. On the other hand, if certain random variations in radar images are considered as undesirable, substantial compression ratio may be achieved by removing such variations.

Wu, C.

1976-01-01

59

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

60

Stationary and moving target shadow characteristics in synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

61

Synthetic aperture radar modeling for the Watchkeeper tactical UAV program  

NASA Astrophysics Data System (ADS)

Critical to the performance of any synthetic aperture radar (SAR) system is accurate compensation for aircraft motion during the imaging aperture. This is thought to be particularly important for Unmanned Aerial Vehicles (UAVs) operating in poor weather conditions where the aircraft may be subject to pronounced turbulence effects. This paper presents some initial findings of an investigation into the effects of aircraft motion on SAR azimuth point spread function for given levels of motion spectrum suppression as supplied by the radar's motion compensation processing. With validation, this approach will allow indicative levels of SAR performance to be estimated over a wide range of operating conditions and hence provides a useful source of advice when considering procurement options.

Jolly, Alistair D.; Thompson, Peter

2002-07-01

62

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

63

Synthetic aperture radar imaging from an inclined geosynchronous orbit  

NASA Technical Reports Server (NTRS)

Images of earth can be produced with an assumed synthetic aperture radar (SAR) on a satellite platform undergoing a nutating relative motion from geosynchronous altitude. From a 50 deg inclined circular orbit, the contiguous United States can be imaged in about 3 h of segmented operation at 100-m resolution with 4-azimuth-look averaging. The 2450-MHz transmitter radiates 1312 W of average power from a steerable 15-m-diam antenna. The SAR can image daily an area bounded longitudinally and latitudinally.

Tomiyasu, K.; Pacelli, J. L.

1983-01-01

64

Synthetic aperture radar imaging of a two-story building  

NASA Astrophysics Data System (ADS)

This paper investigates the expected performance of a ground-based, multi-story building imaging radar system through far-field and near-field computer models. We created a 3-D computer-aided design model of a complex two-story building, simulated the radar response from this complex structure for various geometries and applied synthetic aperture radar image formation algorithms consistent with the simulation scenarios. In this study, we employed the Finite Difference Time Domain method and the Xpatch software to compute the radar signatures. The numerical results give a better understanding of the phenomenology of the scattering and imaging processes and show that relying solely on the far-field scattering data at one elevation angle is not sufficient to obtain the multi-story building layout. Multiple elevation angle views are required in order to determine the location of imaged objects in the vertical direction. Xpatch simulation results in a near-field strip-map configuration suggest a way to achieve this goal within the constraints of a ground-based radar system.

Le, Calvin; Dogaru, Traian

2012-06-01

65

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

66

Passive synthetic aperture radar imaging of ground moving targets  

NASA Astrophysics Data System (ADS)

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

Wacks, Steven; Yazici, Birsen

2012-05-01

67

Signal based motion compensation for synthetic aperture radar  

SciTech Connect

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

John Kirk

1999-06-07

68

Studies Directed Toward the Achievement of Wide Swathwidths in Synthetic Aperture Radar  

NASA Technical Reports Server (NTRS)

Studies to achieve wide swath widths in Synthetic Aperture Radar are described. The use of multiple beams in range and/or azimuth is considered. Radar system parameters for a number of cases are computed.

Cutrona, L. J.

1979-01-01

69

Focused synthetic aperture radar processing of ice-sounder data collected over the Greenland ice sheet  

E-print Network

We developed a synthetic aperture radar (SAR) processing algorithm for airborne/spaceborne ice-sounding radar systems and applied it to data collected in Greenland. By using focused SAR (phase-corrected coherent averaging), we improved along...

Legarsky, J. L.; Gogineni, Sivaprasad; Akins, T. L.

2001-10-01

70

Addendum to proceedings of the 1978 Synthetic Aperture Radar Technology Conference  

NASA Technical Reports Server (NTRS)

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

1978-01-01

71

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

72

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

73

Characterizing Levees using Polarimetric and Interferometric Synthetic Aperture Radar Imagery  

NASA Astrophysics Data System (ADS)

Monitoring the physical condition of levees is vital in order to protect them from flooding. The dynamics of subsurface water events can cause damage on levee structures which could lead to slough slides, sand boils or through seepage. Synthetic Aperture Radar (SAR) technology, due to its high spatial resolution and soil penetration capability, is a good choice to identify such problem areas so that they can be treated to avoid possible catastrophic failure. The radar polarimetric and interferometric data is capable of identifying variations in soil properties of the areas which might cause levee failure. The study area encompasses portion of levees of the lower Mississippi river in the United States. The methodology of this research is mainly categorized into two streams: 1) polarimetric data analysis and classification, and 2) interferometric analysis. Two sources of SAR imagery are used: a) quad-polarized, L-band data from Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) for polarimetric classification, and b) high resolution dual-polarized Terrasar-X data for interferometric analysis. NASA's UAVSAR imagery acquired between 2009 and 2011 are used for the analysis. The polarimetric classification is performed based on the decomposition parameters: entropy (H), anisotropy (A) and alpha (?) and the results detected slough slides on the levees and potential future slides. In the interferometric approach, the Terrasar-X SAR images acquired at different times in the year 2011 are combined into pairs to exploit the phase difference of the signals. The interferometric information is used to find evidence of potential small-scale deformations which could be pre-cursors to levee failure.

Dabbiru, L.; Aanstoos, J. V.; Mahrooghy, M.; Gokaraju, B.; Nobrega, R. A.; Younan, N. H.

2011-12-01

74

BYU MICRO-SAR: A VERY SMALL, LOW-POWER LFM-CW SYNTHETIC APERTURE RADAR  

E-print Network

BYU MICRO-SAR: A VERY SMALL, LOW-POWER LFM-CW SYNTHETIC APERTURE RADAR by Michael I. Duersch-SAR: A VERY SMALL, LOW-POWER LFM-CW SYNTHETIC APERTURE RADAR Michael I. Duersch Department of Electrical-weight, and low power consumption SAR for flight on a small unmanned aerial vehicle (UAV) at low altitudes

Long, David G.

75

Synthetic-Aperture Radar Based on Nonsinusoidal Functions: III-Beam- Forming by Means of the Doppler Effect  

Microsoft Academic Search

Synthetic-aperture radar based on nonsinusoidal functions was discussed in two previous papers [1]. The Doppler effect was not used to produce the synthetic aperture, even though the conventional synthetic-aperture radar would not work without it. This paper shows how the Doppler effect of a nonsinusoidal wave can be used to produce a synthetic aperture. The main result is that the

Henning Harmuth

1979-01-01

76

Use of Synthetic Aperture Radar in Cold Climate Flood Response  

NASA Astrophysics Data System (ADS)

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. These data were primarily used to indentify floodwater inundation polygons and flow vectors. However, in cold climate flooding, there are complicating factors such as frazil ice, ice jams, and snow-covered, frozen flood waters that are not present during warmer flooding events. The imagery was obtained through the International Charter "Space and Major Disasters.” The Charter aims at providing a unified system of space data acquisition and delivery to those affected by natural or man-made disasters through Authorized Users. Each member agency has committed resources to support the provisions of the Charter, and thus is helping to mitigate the effects of disasters on human life and property. On 25 March 2009, the Charter was activated in response to the flooding along the Red River of the North in the states of North Dakota and Minnesota of the United States. The delivery time of a single SAR scene from a Charter participant was less than 12 hours from the time of acquisition. This expedited service allowed additional time for creating image-based derivations, field checking and delivery to a decision maker or emergency responder. SAR-derived data sets include identification of river ice and saturated ground conditions. This data could be provided to experts in river ice engineering for use in the development of plans to reduce ice jamming, its effect on water levels and additional stresses on river infrastructure. During disaster response applications, SAR data was found to very useful in indentifying open water and the front of ice jams. Using a river mask from historical imagery, the SAR data helped to confirm if areas behind flood protection were, in fact, frozen flood water or snow-covered field. This analysis would benefit from future research efforts because optical sensor data is of little use in this application.

Yarbrough, L. D.

2009-12-01

77

Seamless Synthetic Aperture Radar Archive for Interferometry Analysis  

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

78

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

79

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

80

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 to get your arms around' the problem of ascertaining achievable performance limits, and yet those limits exist and are dictated by physics. This report identifies and explores those limits, and how they depend on hardware system parameters and environmental conditions. Ultimately, this leads to a characterization of parameters that offer optimum performance for the overall ISAR system. While the information herein is not new to the literature, its collection into a single report hopes to offer some value in reducing the seek time'.

Doerry, Armin Walter

2013-11-01

81

Adaptive resource allocation for synthetic aperture radars under resource constraints  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

82

The rapid terrain visualization interferometric synthetic aperture radar sensor  

NASA Astrophysics Data System (ADS)

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

2003-11-01

83

Strapdown inertial navigation system requirements imposed by synthetic aperture radar  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to demonstrate a means of specifying strapdown inertial navigation system (INS) requirements from synthetic aperture radar (SAR) requirements. The latter include allowable levels for quadratic and cubic phase shift, and side lobe levels (i.e., peak side lobe ratio (PSLR) and integrated side lobe ratio (ISLR). When these multiple considerations produce different INS requirements, of course, the tightest governs. Results obtained constitute a technique demonstration only, and do not represent any specific mechanization. In the process of this investigation several pitfalls in common procedures were identified; these are highlighted in the discussion. A brief background description is provided in the Appendix for those unfamiliar with the analysis of SAR degradations.

Farrell, J. L.

1985-08-01

84

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.

85

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

86

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

87

Synthetic aperture radar: not just a sensor of last resort  

NASA Astrophysics Data System (ADS)

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

Wells, Lars M.; Doerry, Armin W.

2003-08-01

88

Unexploded ordnance detection experiments using ultrawideband synthetic aperture radar  

NASA Astrophysics Data System (ADS)

The Army Research Laboratory (ARL) has several technology development programs that are evaluating the use of ultra- wideband synthetic aperture radar (UWB SAR) to detect and locate targets that are subsurface or concealed by foliage. Under these programs, a 1-GHz-bandwidth, low-frequency, fully polarimetric UWB SAR instrumentation system was developed to collect the data needed to support foliage and ground- penetrating radar studies. The radar was integrated onto a 150-ft-high mobile boomlift platform in 1995 and was thus named the BoomSAR. In 1997, under the sponsorship of the Strategic Environmental Research and Development Program (SERDP), ARL began a project focused on enhancing the detection and discrimination of unexploded ordnance (UXO). The program's technical approach is to collect high-quality, precision data to support phenomenological investigations of electromagnetic wave propagation through varying dielectric media, which in turn supports the development of algorithms for automatic target detection. For this project, a UXO test site was set up at the Steel Crater Test Area -- an existing test site that already contained subsurface mines, tactical vehicles, 55-gallon drums, storage containers, wires, pipes, and arms caches located at Yuma Proving Ground (YPG), Arizona. More than 600 additional pieces of inert UXO were added to the Steel Crater Test Area, including bombs (250, 500, 750, 1000, and 2000 lb), mortars (60 and 81 mm), artillery shells (105 and 155 mm), 2.75-in. rockets, submunitions (M42, BLU-63, M68, BLU-97, and M118), and mines (Gator, VS1.6, M12, PMN, and POM- Z). In the selection of UXO to be included at YPG, an emphasis was placed on the types of munitions that may be present at CONUS test and training ranges.

DeLuca, Clyde C.; Marinelli, Vincent R.; Ressler, Marc A.; Ton, Tuan T.

1998-09-01

89

Simulation and studies of spaceborne synthetic aperture radar image quality with reduced bit rate  

NASA Technical Reports Server (NTRS)

A computer simulation program that is used to study the effects of digitization in spaceborne synthetic aperture radar systems is described. An analytical study of the distortion noise introduced by the digitization process at various gain settings, sampling rates and bit error rates is presented and the results agree well with those obtained from the simulation program. The simulation program is also used to study the spatial frequency response of hard-limiting (quantizing to 1-bit) synthetic aperture radar systems. The implications of these results on synthetic aperture radar system design are discussed.

Li, F.; Held, D.; Huneycutt, B.; Zebker, H.

1981-01-01

90

High-Resolution Synthetic Aperture Radar Observations of the Moon  

NASA Astrophysics Data System (ADS)

Variations in radar backscatter from planetary surfaces are related to differences in the local slope and the electrical and structural properties of the top surface layer. The top few meters of the surface of the Moon consist of fine-grained unconsolidated rock material containing exposed and buried rocks. Previous Lunar radar measurements have shown a depolarized backscatter component related to the abundance of surface and sub-surface rocks and a linearly polarized component associated with-surface backscatter. High spatial resolution observations of the Lunar surface were conducted using the Arecibo Observatory 12.6 cm wavelength radar in 1990 and 1992 with the aim of analyzing local variations in the surface backscatter properties. In the finest spatial resolution mode a pulsed pseudo-random code with a 10 MHz bandwidth was transmitted and approximately 24 minutes of data was processed to achieve pixel resolutions smaller than 40 m in both dimensions. To obtain this fine resolution over a large area, a focused delay-Doppler algorithm was developed. This new data processing method applies range and frequency offsets to the raw data that permit processing with an algorithm similar to that used for strip mode synthetic aperture radar. A circularly polarized wave was transmitted and both senses of circular polarization were received. Stokes vector analysis was used to estimate the circularly and linearly polarized backscatter components. The comparison of these measurements to a model of quasi-specular and diffuse backscatter from surface and sub-surface structures yielded estimates of the surface dielectric constant and showed that subsurface quasi-specular scattering is required for this model to explain the linearly polarized backscatter power. Images of the Lunar poles show enhanced backscatter with a circular polarization ratio of approximately 0.9 from the radar facing inner walls and ejecta of several impact craters. This result is mainly attributed to diffuse backscatter from exposed and buried rocks. The orientation of the linearly polarized backscatter component was found to correlate with surface topography confirming that this component is, in general, the result of transmission through the surface. Results of an interferometric experiment showed that interferometric phase fringes related to topography can be generated from data acquired several months apart.

Stacy, Nicholas John Sholto

91

High-resolution synthetic aperture radar observations of the Moon  

NASA Astrophysics Data System (ADS)

Variations in radar backscatter from planetary surfaces are related to differences in the local slope and the electrical and structural properties of the top surface layer. The top few meters of the surface of the moon consist of fine-grained unconsolidated rock material containing exposed and buried rocks. Previous lunar radar measurements have shown a depolarized backscatter component related to the abundance of surface and subsurface rocks and a linearly polarized component associated with subsurface backscatter. High spatial resolution observations of the lunar surface were conducted using the Arecibo Observatory 12.6 cm wavelength radar in 1990 and 1992 with the aim of analyzing local variations in the surface backscatter properties. In the finest spatial resolution mode, a pulsed pseudo-random code with a 10 MHz bandwidth was transmitted and approximately 24 minutes of data was processed to achieve pixel resolutions smaller than 40 m in both dimensions. To obtain this fine resolution over a large area, a focused delay-Doppler algorithm was developed. This new data processing method applies range and frequency offsets to the raw data that permit processing with an algorithm similar to that used for strip mode synthetic aperture radar. A circularly polarized wave was transmitted and both senses of circular polarization were received. Stokes vector analysis was used to estimate the circularly and linearly polarized backscatter components. The comparison of these measurements to a model of quasi-specular and diffuse backscatter from surface and subsurface structures yielded estimates of the surface dielectric constant and showed that subsurface quasi-specular scattering is required for this model to explain the linearly polarized backscatter power. Images of the lunar poles show enhanced backscatter with a circular polarization ratio of approximately 0.9 from the radar facing inner walls and ejecta of several impact craters. This result is mainly attributed to diffuse backscatter from exposed and buried rocks. The orientation of the linearly polarized backscatter component was found to correlate with surface topography confirming that this component is, in general, the result of transmission through the surface. Results of an interferometric experiment show that interferometric phase fringes related to topography can be generated from data acquired several months apart.

Stacy, Nicholas John Sholto

1993-01-01

92

Microlocal Structure of High Range-Resolution Inverse Synthetic-Aperture Radar Data  

E-print Network

Microlocal Structure of High Range-Resolution Inverse Synthetic-Aperture Radar Data Margaret Cheney the problem of identification of airborne objects from high-range- resolution radar data. We use high-frequency asymptotics to show that certain features of the object correspond to identifiable features of the radar data

Cheney, Margaret

93

Metrology, attitude, and orbit determination for spaceborne interferometric synthetic aperture radar  

Microsoft Academic Search

The Shuttle Radar Topography Mission (SRTM), scheduled for an 11 day Space Shuttle flight in 1999, will use an Interferometric Synthetic Aperture Radar instrument to produce a near-global digital elevation map of the earth's land surface with 16 m absolute vertical height accuracy at 30 meter postings. SRTM will achieve the required interferometric baseline by extending a receive-only radar antenna

Riley M. Duren; Ed Wong; Bill Breckenridge; Scott Shaffer; Courtney Duncan; Eldred F. Tubbs; Phil M. Salomon

1998-01-01

94

UHF Microstrip Antenna Array for Synthetic- Aperture Radar  

NASA Technical Reports Server (NTRS)

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

Thomas, Robert F.; Huang, John

2003-01-01

95

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

96

Statistical assessment of model fit for synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

Parametric approaches to problems of inference from observed data often rely on assumed probabilistic models for the data which may be based on knowledge of the physics of the data acquisition. Given a rich enough collection of sample data, the validity of those assumed models can be assessed in a statistical hypothesis testing framework using any of a number of goodness-of-fit tests developed over the last hundred years for this purpose. Such assessments can be used both to compare alternate models for observed data and to help determine the conditions under which a given model breaks down. We apply three such methods, the (chi) 2 test of Karl Pearson, Kolmogorov's goodness-of-fit test, and the D'Agostino-Pearson test for normality, to quantify how well the data fit various models for synthetic aperture radar (SAR) images. The results of these tests are used to compare a conditionally Gaussian model for complex-valued SAR pixel values, a conditionally log-normal model for SAR pixel magnitudes, and a conditionally normal model for SAR pixel quarter-power values. Sample data for these tests are drawn from the publicly released MSTAR dataset.

DeVore, Michael D.; O'Sullivan, Joseph A.

2001-08-01

97

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

98

Joint anisotropy characterization and image formation in wide-angle synthetic aperture radar  

E-print Network

Imagery formed from wide-angle synthetic aperture radar (SAR) measurements has fine cross-range resolution in principle. However, conventional SAR image formation techniques assume isotropic scattering, which is not valid ...

Varshney, Kush R. (Kush Raj)

2006-01-01

99

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

100

Seamless Synthetic Aperture Radar Archive for Interferometry Analysis  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

101

Tundra Fire Effects Mapping from Synthetic Aperture Radar Satellite Data  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

102

On the Detectability of Ocean Surface Waves by Real and Synthetic Aperture Radar  

Microsoft Academic Search

Real and synthetic aperture radars have been used in recent years to image ocean surface waves. Though wavelike patterns are often discernible on radar images, it is still not fully understood how they relate to the actual wave field. The present paper reviews and extends current models on the imaging mechanism. Linear transfer functions that relate the two-dimensional wave field

Werner R. Alpers; Duncan B. Ross; Clifford L. Rufenach

1981-01-01

103

Numerical Simulation of Synthetic Aperture Radar Image Spectra for Ocean Waves  

Microsoft Academic Search

A numerical model for predicting the synthetic aperture radar (SAR) image of a moving ocean surface is described, and results are presented for two SIR-B data sets collected off the coast of Chile. Wave height spectra measured by the NASA radar ocean wave spectrometer (ROWS) were used as inputs to this model, and results are compared with actual SIR-B image

DAVID R. LYZENGA

1986-01-01

104

Miniaturized high resolution Synthetic Aperture Radar at 94 GHz for microlite aircraft or UAV  

Microsoft Academic Search

A miniaturised millimetre wave radar, MIRANDA, to be used as Synthetic Aperture Radar onboard a small UAV was designed, built and tested onboard a microlite aircraft and an unmanned helicopter. The design followed the FM-CW principle, to get the highest possible average transmit power and thus the best range performance. A very flexible principle of operation, based upon multiplication of

Winfried Johannes; Helmut Essen; Stephan Stanko; Rainer Sommer; Alfred Wahlen; Jorn Wilcke; Christian Wagner; Michael Schlechtweg; Axel Tessmann

2011-01-01

105

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

106

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

PubMed

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

Fiori, Simone

2003-01-01

107

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

108

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

109

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

110

Estimating boreal forest species type with airborne polarimetric synthetic aperture radar  

Microsoft Academic Search

We have applied a non-parametric classifier (k nearest neighbour) to two calibrated orthogonal passes of airborne polarimetric synthetic aperture radar (POLSAR) image data over boreal forest for the purpose of discriminating canopy tree species of predefined stands. We found that a single classifier based on a single feature space (i.e. one set of POLSAR variables for all species) was less

Michael Wollersheim; Michael J. Collins; Don Leckie

2011-01-01

111

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

112

The use of synthetic aperture radar to detect and chart submerged navigation hazards  

Microsoft Academic Search

This report discusses the utility of synthetic aperture radar (SAR) data collected by the SEASAT satellite for the detection and charting of bottom features which might be hazardous to navigation. Data from 35 SEASAT orbits were used to examine nine test sites. These test sites included: the Tongue of the Ocean, Bermuda, Haiti, Sula Sgier, Cook Inlet (Alaska), the Mississippi

E. A. Kasischke; D. R. Lyzenga; R. A. Shcuhman; Y. S. Tsen; B. S. Termaat; B. A. Burns; G. A. Meadows

1982-01-01

113

Tropical cyclone morphology from spaceborne synthetic aperture radar1 Xiaofeng Li1  

E-print Network

1 Tropical cyclone morphology from spaceborne synthetic aperture radar1 2 Xiaofeng Li1 , Jun A and innovative mapping approaches to better understand the dynamics4 of tropical cyclone genesis, morphology and movement. Although tropical cyclones can be5 detected by many remote sensors, SAR can yield high

Long, David G.

114

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

115

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

SciTech Connect

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

Doerry, Armin Walter

2012-05-01

116

Atmospheric effects in interferometric synthetic aperture radar surface deformation and topographic maps  

Microsoft Academic Search

Interferogram images derived from repeat-pass spaceborne synthetic aperture radar systems exhibit artifacts due to the time and space variations of atmospheric water vapor. Other tropospheric variations, such as pressure and temperature, also induce distortions, but the effects are smaller in magnitude and more evenly distributed throughout the interferogram than the wet troposphere term. Spatial and temporal changes of 20% in

Howard A. Zebker; Paul A. Rosen; Scott Hensley

1997-01-01

117

Spectral signal to clutter and thermal noise properties of ocean wave imaging synthetic aperture radars  

Microsoft Academic Search

The high wavenumber detection cut-off is determined above which the spectrum of ocean waves imaged by a synthetic aperture radar (SAR) is lost in the background noise spectrum consisting of the clutter noise associated with the Rayleigh statistics of the backscattering surface and the thermal noise originating in the SAR system itself. For given power, the maximum detection cut-off wavenumber

Werner Alpers; Klaus Hasselmann

1982-01-01

118

Monte Carlo simulations for studying the relationship between ocean wave and synthetic aperture radar image spectra  

Microsoft Academic Search

A theoretical model previously developed for describing the imaging of monochromatic ocean waves by synthetic aperture radar (SAR) is extended to relate ocean wave spectra to SAR image spectra. Since the SAR response to the moving ocean surface is nonlinear for a large range of ocean wave parameters, this relationship can, in general, not be described by a linear mapping

Werner Alpers

1983-01-01

119

An improved algorithm for the retrieval of ocean wave spectra from synthetic aperture radar image spectra  

Microsoft Academic Search

An earlier algorithm for retrieving two-dimensional wave spectra from synthetic aperture radar (SAR) image spectra is improved by using a modified cost function and introducing an additional iteration loop in which the first-guess input spectrum is systematically updated. For this purpose a spectral partitioning scheme is applied in which the spectrum is decomposed into a finite number of distinct wave

S. Hasselmann; C. Brüning; K. Hasselmann; P. Heimbach

1996-01-01

120

The effect of orbital motions on synthetic aperture radar imagery of ocean waves  

Microsoft Academic Search

The formation of wave-like patterns in synthetic aperture radar (SAR) images of the ocean surface caused by orbital motions is investigated. Furthermore, the degradation in azimuthal resolution due to these motions is calculated by applying a least square fit to the phase history. Formulas are given which describe the variation of intensity in azimuthal direction in the image plane as

WERNER R. ALPERS; C. Rufenach

1979-01-01

121

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

Microsoft Academic Search

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

C. Mastenbroek; C. F. de Valk

2000-01-01

122

Waves in frazil and pancake ice and their detection in Seasat synthetic aperture radar imagery  

Microsoft Academic Search

A theoretical model of waves propagating into an ice cover composed of frazil and pancake ice is developed and compared with measurements of wavelength and direction derived from synthetic aperture radar (SAR) imagery obtained from Seasat in October 1978. The theoretical model is based on the concept that ice of these types, which consists of small crystals or cakes, has

Peter Wadhams; Benjamin Holt

1991-01-01

123

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

Microsoft Academic Search

A neural network system for boundary segmentation and surface representation, inspired by a new local-circuit model of visual processing in the cerebral cortex, is used to enhance images of range data gathered by a synthetic aperture radar (SAR) sensor. Boundary segmentation is accomplished by an improved Boundary Contour System (BCS) model which completes coherent boundaries that retain their sensitivity to

Ennio Mingolla; William D. Ross; Stephen Grossberg

1999-01-01

124

Discontinuity Adaptive MRF Model for the Analysis of Synthetic Aperture Radar Images  

Microsoft Academic Search

In this paper, a novel approach is presented for the segmentation of synthetic aperture radar (SAR) images. The method integrates the gamma distribution, appropriate for SAR data, in an objective function that exploits the discontinuity adaptive MRF model proposed by Li (1995). After a straightforward initialization routine that computes for each class the mean intensity value, the objective function is

Paul C. Smits; Silvana G. Dellepiane

1997-01-01

125

Use of the coherence of synthetic aperture radar cross spectra for ocean wave measurements  

Microsoft Academic Search

A noise model for synthetic aperture radar (SAR) look cross spectra (LCS) acquired over the ocean is proposed. The study is meant to contribute to the improvement of algorithms for retrieval of two dimensional ocean wave spectra from LCS. Error bars for the LCS phase, which contains information on the ocean wave phase speed and propagation direction are derived. The

J. Schulz-Stellenfleth; S. Lehner; D. Hoja

2002-01-01

126

Development of a high precision timing and control unit for Synthetic Aperture Radar  

Microsoft Academic Search

This paper discusses the design and development of an Field Programmable Gate Array (FPGA) based timing and control unit for high resolution Unmanned Aerial Vehicle (UAV) Synthetic Aperture Radar (SAR). The unit controls sub modules of SAR such as the timing of the chirp generator, the data acquisition module, the motion compensation module and any other modules that requires a

Huey Shen Boey; Tien Sze Lim; Voon Chet Koo; Fabian Kung Wai Lee

2011-01-01

127

A butterfly algorithm for synthetic aperture radar imaging Laurent Demanet1  

E-print Network

A butterfly algorithm for synthetic aperture radar imaging Laurent Demanet1 , Matthew Ferrara2, with the desired pixelwise accuracy. It is based on the butterfly scheme, which unlike the FFT works for vastly analysis in the butterfly algorithm. MF and LD are grateful for AFOSR support from Arje Nachman. MF and NM

Peraire, Jaime

128

A butterfly algorithm for synthetic aperture radar imaging Laurent Demanet1  

E-print Network

A butterfly algorithm for synthetic aperture radar imaging Laurent Demanet1 , Matthew Ferrara2 pixelwise accuracy. It is based on the butterfly scheme, which unlike the FFT works for vastly more general in the butterfly algorithm. MF is grateful for AFOSR support from Arje Nachman. MF and NM were partially supported

Demanet, Laurent

129

Eliminating Doppler Effects in Synthetic-Aperture Radar Optical Processors  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

130

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

131

Three-dimensional subsurface imaging Synthetic Aperture Radar  

SciTech Connect

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

Wuenschel, E. [Mirage Systems, Inc., Sunnyvale, CA (United States)

1995-10-01

132

Synthetic aperture radar simulation system based on Matlab  

Microsoft Academic Search

This paper introduces the SAR simulation system realized by using Matlab. The SAR imaging algorithm with pulse compression is discussed, and simulated radar images are also presented. It is shown that the SAR simulation system is flexible due to the easy program language and powerful signal processing tools of Matlab

Zhang Hongyuan; Zhang Yunhua; Jiang Jingshan

2000-01-01

133

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

134

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

135

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

136

Physical Limitations on Detecting Tunnels using Underground Focusing Spotlight Synthetic Aperture Radar  

Microsoft Academic Search

This work studies the concept of Underground Focusing Spotlight Synthetic Aperture Radar (UF-SL-SAR) systems for tunnel detection applications. A general formulation for generating UF-SL-SAR imaging in realistic, randomly rough ground is developed by focusing in space and frequency at subsurface points by considering rays refraction at the nominal ground surface. Imaging results are presented for two soil scenarios: dry sand

Carey M. Rappaport; Jose Angel Martinez Lorenzo

2009-01-01

137

Feasibility of tunnel detection under rough ground surfaces using Underground Focusing Spotlight Synthetic Aperture Radar  

Microsoft Academic Search

Detecting and imaging the presence of illicit tunnels in any given volume of soil is occasionally possible because the air that fills them is materially quite different from anything else underground. The Underground Focusing Spotlight Synthetic Aperture Radar (UF-SL-SAR) concept has been suggested for sub-surface tunnel detection due to its ability to scan large areas of terrain in a short

Fernando Quivira; Kristen Fassbender; Jose A. Martinez-Lorenzo; Carey M. Rappaport

2010-01-01

138

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

139

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

NASA Technical Reports Server (NTRS)

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

Hsiao, S. V.

1978-01-01

140

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

141

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

NASA Astrophysics Data System (ADS)

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

Deshpande, M.

2012-10-01

142

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

143

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

144

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

NASA Technical Reports Server (NTRS)

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

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

1996-01-01

145

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

146

Numerical simulation of synthetic aperture radar image spectra for ocean waves  

NASA Technical Reports Server (NTRS)

A numerical model for predicting the synthetic aperture radar (SAR) image of a moving ocean surface is described, and results are presented for two SIR-B data sets collected off the coast of Chile. Wave height spectra measured by the NASA radar ocean wave spectrometer (ROWS) were used as inputs to this model, and results are compared with actual SIR-B image spectra from orbits 91 and 106. Additional parametric variations are presented to illustrate the effects of nonlinearities in the imaging process.

Lyzenga, D. R.

1986-01-01

147

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

NASA Astrophysics Data System (ADS)

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.

1993-05-01

148

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

149

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

SciTech Connect

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

Doerry, A.W.

1994-01-01

150

Analysis of synthetic aperture radar data acquired over a variety of land cover  

NASA Technical Reports Server (NTRS)

The results of Synthetic Aperture Radar (SAR) measurements over Kershaw County, South Carolina, using HH, HV, and VV polarization and two-incidence angle X-band airborne SAR system and over Baldwin County, Alabama, using HH polarization L-band Shuttle Imaging Radar (SIR-A) are presented. The X-band data indicate higher HH than VV radar return for cypress forest with standing water. Multipolarization (HH, HV, and VV) data help delineate several land-cover types that are difficult to delineate by the single polarization (HH) data. The L-band data indicate that radar return signal strength is highly correlated with tree height or age for three types of pine forest. It is found that delineation of urban/residential from deciduous forest is significantly improved by the inclusion of Landsat multispectral scanner data.

Wu, S.-T.

1984-01-01

151

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

152

Accurate geometrical model for airborne synthetic aperture radar  

NASA Astrophysics Data System (ADS)

The accurate knowledge of the geometry of an airborne SAR image is crucial for many applications. Repeat-pass SAR interferometry requires an accurate image matching to the 10th of a pixel, while less demanding applications such as wide area coverage by multi-pass composite or image geocoding tolerate mismatches of pixels. Compared to spaceborne SAR, those accuracy requirements are stronger for airborne SAR sine they provide higher resolution. Moreover, irregularities in aircraft motion due to air turbulence introduce severe geometrical distortions in the images. Unfortunately, these distortions are tightly coupled with the signal processing algorithm used for computing SAR images. We have implemented a geometrical error model for our generic off-line SAR processor which provides an image distortion map. Derivatives with respect to errors in radar parameters and errors in aircraft trajectory measurements (velocity, altitude, oscillations are also provided, thus allowing the efficient estimation of the errors from distortion measurements (tiepoints). The paper is illustrated with some relevant application examples.

Cantalloube, Hubert M. J.; Nahum, Carole E.

1999-12-01

153

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

NASA Technical Reports Server (NTRS)

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

Tomiyasu, K.

1981-01-01

154

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

155

Synthetic Aperture Radar Interferometry to Measure Earth's Surface Topography and Its Deformation  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar interferometry (InSAR) from Earth-orbiting spacecraft provides a new tool to map global topography and deformation of the Earth's surface. Radar images taken from slightly different viewing directions allow the construction of digital elevation models of meter-scale accuracy. These data sets aid in the analysis and interpretation of tectonic and volcanic landscapes. If the Earth's surface deformed between two radar image acquisitions, a map of the surface displacement with tens-of-meters resolution and subcentimeter accuracy can be constructed. This review gives a basic overview of InSAR for Earth scientists and presents a selection of geologic applications that demonstrate the unique capabilities of InSAR for mapping the topography and deformation of the Earth.

Bürgmann, Roland; Rosen, Paul A.; Fielding, Eric J.

156

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

157

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

158

Neighborhood virtual points discriminant embedding for synthetic aperture radar automatic target recognition  

NASA Astrophysics Data System (ADS)

We propose a new feature extraction method for synthetic aperture radar automatic target recognition based on manifold learning theory. By introducing the virtual point in every sample's neighborhood, we establish the spatial relationships of the neighborhoods. When the samples are embedded into the feature space, each sample moves toward its neighborhood virtual point, whereas the virtual points with the same class label get together, and the virtual points from different classes separate from each other. This can improve the classification and recognition performance effectively. Experiments based on the moving and stationary target acquisition and recognition database are conducted to verify the effectiveness of our method.

Pei, Jifang; Huang, Yulin; Liu, Xian; Yang, Jianyu

2013-03-01

159

Theory of Waveform-Diverse Moving-Target Spotlight Synthetic-Aperture Radar  

E-print Network

We develop a theory for waveform-diverse moving-target synthetic-aperture radar, in the case in which a single moving antenna is used for both transmitting and receiving. We assume that the targets (scattering objects) are moving linearly, but we allow an arbitrary, known flight path for the antenna and allow it to transmit a sequence of arbitrary, known waveforms. A formula for phase space (position and velocity) imaging is developed, and we provide a formula for the point-spread function of the corresponding imaging system. This point-spread function is expressed in terms of the ordinary radar ambiguity function. As an example, we show how the theory can be applied to the problem of estimating the errors that arise when target and antenna motion is neglected during the transit time of each pulse.

Margaret Cheney; Brett Borden

2011-05-15

160

Mine detection with a forward-looking ground-penetrating synthetic aperture radar  

NASA Astrophysics Data System (ADS)

In order to detect buried land mines in clutter, Planning Systems Incorporated has adapted its Ground Penetrating Synthetic Aperture Radar (GPSAR) technology for forward-looking applications. The Forward Looking GPSAR (FLGPSAR), is a wide-band stepped-frequency radar operating over frequencies from 400 MHz to 4 GHz. The FLGPSAR system is based on a modified John Deere E-Gator turf vehicle that is capable of remote control. Custom Archimedean spiral antennas are used to populate the GPSAR array. These antennas are designed and built by PSI and have exceptional broad-band radiation characteristics. The FLGSPAR system has been used to detect plastic and metallic landmines at U.S. Army test facilities and at PSI's engineering center in Long Beach Mississippi. Multi-look SAR processing has been shown to significantly improve the quality of FLGPSAR imagery.

Bradley, Marshall R.; Witten, Thomas R.; Duncan, Michael; McCummins, Robert

2003-09-01

161

Theory of Waveform-Diverse Moving-Target Spotlight Synthetic-Aperture Radar  

E-print Network

We develop a theory for waveform-diverse moving-target synthetic-aperture radar, in the case in which a single moving antenna is used for both transmitting and receiving. We assume that the targets (scattering objects) are moving linearly, but we allow an arbitrary, known flight path for the antenna and allow it to transmit a sequence of arbitrary, known waveforms. A formula for phase space (position and velocity) imaging is developed, and we provide a formula for the point-spread function of the corresponding imaging system. This point-spread function is expressed in terms of the ordinary radar ambiguity function. As an example, we show how the theory can be applied to the problem of estimating the errors that arise when target and antenna motion is neglected during the transit time of each pulse.

Cheney, Margaret

2011-01-01

162

The tomographic formulation of spotlight mode synthetic aperture radar extended to three dimensional targets  

NASA Astrophysics Data System (ADS)

In this paper we take a new look at the tomographic formulation of spotlight mode synthetic aperture radar (SAR), so as to include the case of targets having three-dimensional structure. This bridges the work of David C. Munson and his colleagues, who first described SAR in terms of two-dimensional tomography, with Jack Walker's original derivation of spotlight mode SAR imaging via Doppler analysis. The main result is to demonstrate that the demodulated radar return data from a spotlight mode collection represent a certain set of samples of the three-dimensional Fourier transform of the target reflectivity function, and to do so using tomographic principles instead of traditional Doppler arguments. We then show that the tomographic approach is useful in interpreting the two-dimensional SAR image of a three-dimensional scene. In particular, the well-known SAR imaging phenomenon commonly referred to as layover is easily explained in terms of tomographic projection.

Jakowatz, C. V., Jr.; Thompson, P. A.

1992-02-01

163

A signal processing view of strip-mapping synthetic aperture radar  

NASA Technical Reports Server (NTRS)

The authors derive the fundamental strip-mapping SAR (synthetic aperture radar) imaging equations from first principles. They show that the resolution mechanism relies on the geometry of the imaging situation rather than on the Doppler effect. Both the airborne and spaceborne cases are considered. Range processing is discussed by presenting an analysis of pulse compression and formulating a mathematical model of the radar return signal. This formulation is used to obtain the airborne SAR model. The authors study the resolution mechanism and derive the signal processing relations needed to produce a high-resolution image. They introduce spotlight-mode SAR and briefly indicate how polar-format spotlight processing can be used in strip-mapping SAR. They discuss a number of current and future research directions in SAR imaging.

Munson, David C., Jr.; Visentin, Robert L.

1989-01-01

164

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

165

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

166

Laboratory experiments on synthetic-aperture laser radar with acousto-optic modulators  

NASA Astrophysics Data System (ADS)

The diffraction limit of laser is smaller than microwave's for its shorter wavelength. Higher spatial resolution will be achieved when laser is applied to the synthetic-aperture radar, called synthetic-aperture laser radar (SAL). Just because of many advantages, in recent years the research on SAL is becoming a hotspot. One of key techniques of SAL is heterodyne detection of signals by means of linear frequency modulation pulse compression (LFM-PC); this paper introduces an experiment based on heterodyne detection with an acousto-optic frequency shifter (AOFS) in our laboratory. Detailed discussion about AOFS is presented. We find that the acousto-optic modulator can considerably influence the transmitted light beam. In particular, when the width of laser beam is larger than the effective width of acousto-optic cell, the transverse distribution of scattering light intensity is inhomogeneous, which will decrease the signal-to-noise ratio of the heterodyne detection. This paper discusses the coupled partial difference equations

Liu, HuanHuan; Zeng, XiaoDong; Cao, ChangQing; Feng, ZheJun; Fu, Chao

2009-07-01

167

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

168

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

169

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.

2012-06-01

170

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

171

Sea ice type maps from Alaska synthetic aperture radar facility imagery: An assessment  

NASA Technical Reports Server (NTRS)

Synthetic aperture radar (SAR) imagery received at the Alaskan SAR Facility is routinely and automatically classified on the Geophysical Processor System (GPS) to create ice type maps. We evaluated the wintertime performance of the GPS classification algorithm by comparing ice type percentages from supervised classification with percentages from the algorithm. The root mean square (RMS) difference for multiyear ice is about 6%, while the inconsistency in supervised classification is about 3%. The algorithm separates first-year from multiyear ice well, although it sometimes fails to correctly classify new ice and open water owing to the wide distribution of backscatter for these classes. Our results imply a high degree of accuracy and consistency in the growing archive of multiyear and first-year ice distribution maps. These results have implications for heat and mass balance studies which are furthered by the ability to accurately characterize ice type distributions over a large part of the Arctic.

Fetterer, Florence M.; Gineris, Denise; Kwok, Ronald

1994-01-01

172

Evaluation of terrain models for the geocoding and terrain correction of synthetic aperture radar (SAR) images  

NASA Astrophysics Data System (ADS)

Synthetic aperture radars (SAR's) are well suited for the measurement of geophysical parameters but the application of SAR imagery is limited by geometric and radiometric effects caused by variable terrain. Terrain models may be used for the rectification of SAR images, but model quality limits the extent of error correction. Various terrain models (USGS, SPOT, and 1 deg models) were used to rectify a Seasat SAR image in order to quantify terrain model differences and their effects on SAR image terrain correction. The accuracy of geocoded and terrain-corrected images was assessed, terrain models were compared, and the effects of terrain model differences on corrected SAR images were analyzed. Results indicate that elevation errors in terrain models are amplified into location errors in the terrain-corrected images. USGS and SPOT terrain-corrected images are superior to the image corrected by the 1 deg terrain model or geocoding using a constant elevation.

Wivell, Charles E.; Steinwand, Daniel R.; Kelly, Glenn G.; Meyer, David J.

1992-11-01

173

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

SciTech Connect

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

Popovics, J. S.; Ham, S. [Department of Civil and Environmental Engineering, The University of Illinois at Urbana-Champaign, Urbana, IL 61801 (United States); Ghasr, M. T.; Zoughi, R. [Department of Electrical and Computer Engineering, Missouri University of Science and Technology (S and T), Rolla, MO 65409 (United States)

2014-02-18

174

Motion of the Lambert Glacier estimated by using differential Interferometric Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

Interferometric Synthetic Aperture Radar (InSAR) is one of the most promising remote sensing technologies and has been widely applied in constructing topographic information and estimating the deformation of the Earth's surface. Ice velocity is an important parameter for calculating the mass balance and modelling ice shelve dynamics. Ice velocity is also an important indicator for climate changes. Therefore, it plays an important role in studying the global climate change and global sea level rise. In this paper, the ERS-1/2 tandem data and the ASTER GDEM are combined together to obtained the deformation in line of sight by using the differential Interferometric SAR for the Lambert Amery glacier in Antarctica. Then the surface parallel assumption is adopted in order to achieve the ice flow velocity. The results showed that ice velocity would be increased along the Lambert glacier; the maximum ice velocity would be reach about 450m/year in the study area.

Liu, Shuang; Tong, Xiaohua; Xie, Huan; Liu, Xiangfeng; Liu, Jun

2014-03-01

175

Use of Seasat synthetic aperture radar and Landsat multispectral scanner subsystem data for Alaskan glaciology studies  

NASA Technical Reports Server (NTRS)

Three Seasat synthetic aperture radar (SAR) and three Landsat multispectral scanner subsystem (MSS) scenes of three areas of Alaska were analyzed for hydrological information. The areas were: the Dease Inlet in northern Alaska and its oriented or thaw lakes, the Ruth and Tokositna valley glaciers in south central Alaska, and the Malaspina piedmont glacier on Alaska's southern coast. Results for the first area showed that the location and identification of some older remnant lake basins were more easily determined in the registered data using an MSS/SAR overlay than in either SAR or MSS data alone. Separately, both SAR and MSS data were useful for determination of surging glaciers based on their distinctive medial moraines, and Landsat data were useful for locating the glacier firn zone. For the Malaspina Glacier scenes, the SAR data were useful for locating heavily crevassed ice beneath glacial debris, and Landsat provided data concerning the extent of the debris overlying the glacier.

Hall, D. K.; Ormsby, J. P.

1983-01-01

176

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

177

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

178

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

179

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

180

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

181

Finding realistic dike models from interferometric synthetic aperture radar data: The February 2000 eruption at Piton de la Fournaise  

Microsoft Academic Search

Dike intrusions often cause complex ground displacements that are not sufficiently explained by simple analytical models. We develop a method to find complex and realistic dike geometries and overpressures from interferometric synthetic aperture radar (InSAR) data. This method is based on a combination of a boundary element method with realistic topography and a neighborhood algorithm inversion. Dike model geometry is

Y. Fukushima; V. Cayol; P. Durand

2005-01-01

182

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

183

Active Microwave Remote Sensing and Synthetic Aperture Radar 2.1. THE INTERACTION OF ELECTROMAGNETIC ENERGY WITH THE  

E-print Network

21 Chapter 2 Active Microwave Remote Sensing and Synthetic Aperture Radar 2.1. THE INTERACTION OF ELECTROMAGNETIC ENERGY WITH THE EARTH'S SURFACE An orbiting, active microwave remote sensing instrument launches the Earth, interacts with the Earth's surface, and is scattered back towards the sensor. The propagation

Fialko, Yuri

184

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

185

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

186

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

NASA Astrophysics Data System (ADS)

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

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

2004-09-01

187

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

NASA Astrophysics Data System (ADS)

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

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

2015-01-01

188

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

NASA Astrophysics Data System (ADS)

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

Minchew, Brent

2012-08-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

190

Precipitation observations from high frequency spaceborne polarimetric synthetic aperture radar and ground-based radar: Theory and model validation  

NASA Astrophysics Data System (ADS)

Global weather monitoring is a very useful tool to better understand the Earth's hydrological cycle and provide critical information for emergency and warning systems in severe cases. Developed countries have installed numerous ground-based radars for this purpose, but they obviously are not global in extent. To address this issue, the Tropical Rainfall Measurement Mission (TRMM) was launched in 1997 and has been quite successful. The follow-on Global Precipitation Measurement (GPM) mission will replace TRMM once it is launched. However, a single precipitation radar satellite is still limited, so it would be beneficial if additional existing satellite platforms can be used for meteorological purposes. Within the past few years, several X-band Synthetic Aperture Radar (SAR) satellites have been launched and more are planned. While the primary SAR application is surface monitoring, and they are heralded as "all weather'' systems, strong precipitation induces propagation and backscatter effects in the data. Thus, there exists a potential for weather monitoring using this technology. The process of extracting meteorological parameters from radar measurements is essentially an inversion problem that has been extensively studied for radars designed to estimate these parameters. Before attempting to solve the inverse problem for SAR data, however, the forward problem must be addressed to gain knowledge on exactly how precipitation impacts SAR imagery. This is accomplished by simulating storms in SAR data starting from real measurements of a storm by ground-based polarimetric radar. In addition, real storm observations by current SAR platforms are also quantitatively analyzed by comparison to theoretical results using simultaneous acquisitions by ground radars even in single polarization. For storm simulation, a novel approach is presented here using neural networks to accommodate the oscillations present when the particle scattering requires the Mie solution, i.e., particle diameter is close to the radar wavelength. The process of transforming the real ground measurements to spaceborne SAR is also described, and results are presented in detail. These results are then compared to real observations of storms acquired by the German TerraSAR-X satellite and by one of the Italian COSMO-SkyMed satellites both operating in co-polar mode (i.e., HH and VV). In the TerraSAR-X case, two horizontal polarization ground radars provided simultaneous observations, from which theoretical attenuation is derived assuming all rain hydrometeors. A C-band fully polarimetric ground radar simultaneously observed the storm captured by the COSMO-SkyMed SAR, providing a case to begin validating the simulation model. While previous research has identified the backscatter and attenuation effects of precipitation on X-band SAR imagery, and some have noted an impact on polarimetric observations, the research presented here is the first to quantify it in a holistic sense and demonstrate it using a detailed model of actual storms observed by ground radars. In addition to volumetric effects from precipitation, the land backscatter is altered when water is on or near the surface. This is explored using TRMM, Canada's RADARSAT-1 C-band SAR and Level 3 NEXRAD ground radar data. A weak correlation is determined, and further investigation is warranted. Options for future research are then proposed.

Fritz, Jason P.

191

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

192

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

193

Mars orbital synthetic aperture radar: Obtaining geologic information from radar polarimetry  

Microsoft Academic Search

Radar penetration of mantling layers, and scattering from buried objects or interfaces, is a topic of current interest in both terrestrial and planetary remote sensing. We examine the behavior of surface and subsurface scattering interfaces and the types of information that may be obtained from observations in different polarizations and wavelengths. These results are applied to the design of a

Bruce A. Campbell; Ted A. Maxwell; Anthony Freeman

2004-01-01

194

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

NASA Technical Reports Server (NTRS)

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

Tomiyasu, K.

1981-01-01

195

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

196

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

197

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

198

A three-dimensional fractional Fourier transformation methodology for volumetric linear, circular, and orbital synthetic aperture radar formation  

NASA Astrophysics Data System (ADS)

The 3-D Fractional Fourier Transformation (FrFT) has unique applicability to multi-pass and multiple receiver Synthetic Aperture Radar (SAR) scenarios which can collect radar returns to create volumetric reflectivity data. The 3-D FrFT can independently compress and image radar data in each dimension for a broad set of parameters. The 3-D FrFT can be applied at closer ranges and over more aperture sampling conditions than other imaging algorithms. The FrFT provides optimal processing matched to the quadratic signal content in SAR (i.e. the pulse chirp and the spherical wave-front across the aperture). The different parameters for 3-D linear, circular, and orbital SAR case are derived and specifi…c considerations such as squint and scene extent for each scenario are addressed. Example imaged volumes are presented for linear, circular and orbital cases. The imaged volume is sampled in the radar coordinate system and can be transformed to a target based coordinate system. Advantages of the FrFT which extend to the 3-D FrFT include its applicability to a wide variety of imaging condition (standoff range and aperture sub-sampling) as well as inherent phase preservation in the images formed. The FrFT closely matches the imaging process and thus is able to focus SAR images over a large variation in standoff ranges specifi…cally at close range. The FrFT is based on the relationship between time and frequency and thus can create an image from an under-sampled wave-front. This ability allows the length of the synthetic aperture to be increased for a fixed number of aperture samples.

Pepin, Matthew

2014-06-01

199

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

200

Performance analysis of weak target detection via ground-based synthetic aperture radar  

NASA Astrophysics Data System (ADS)

Polarimetric Interferometric Synthetic Aperture Radar (Pol-InSAR) is an emerging technique that combines interferometric SAR and polarimetric SAR techniques and has shown its effectiveness in the detection of buried weak targets. The detection performance is affected by the SAR parameters as well as the covering characteristics. In this paper, the effects of covering characteristics on the detection performance were emphasized and experimentally investigated by a ground-based Pol-InSAR system. Firstly, the detection principle for buried weak target by Pol-InSAR technique was presented, which is based on the use of interferometric coherence variation with polarization. Then the ground-based two dimensional rail (TDR) SAR used for investigation was introduced. Furthermore, the experiment target scene was designed and the effects of different covering type, different covering moisture, and different covering depth on the detection performance of weak targets were shown and analyzed. Preliminary results confirmed the effectiveness of Pol-InSAR technique used for weak target detection and it would be helpful for the further investigation of this technique.

Zhou, Yong-sheng; Zhou, Mei; Tang, Ling-li; Li, Chuan-rong

2011-10-01

201

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

202

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

NASA Technical Reports Server (NTRS)

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

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

1988-01-01

203

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

204

The use of synthetic aperture radar to detect and chart submerged navigation hazards  

NASA Astrophysics Data System (ADS)

This report discusses the utility of synthetic aperture radar (SAR) data collected by the SEASAT satellite for the detection and charting of bottom features which might be hazardous to navigation. Data from 35 SEASAT orbits were used to examine nine test sites. These test sites included: the Tongue of the Ocean, Bermuda, Haiti, Sula Sgier, Cook Inlet (Alaska), the Mississippi River Delta, the English Channel, the Nantucket Shoals, and the northeast Atlantic Ocean. The northeast Atlantic test site actually contained 17 distinct bottom features such as seamounts, submarine ridges, banks and the edges of continental shelfs. Three distinct techniques were used to examine the SEASAT SAR imagery: broad survey studies, multi-temporal analyses, and multisensor analyses. This study continued to document the utility of SEASAT SAR imagery for locating and identifying bottom features in both shallow and deep water portions of the world's oceans. By correlating the SAR data with ancillary environmental data (such as wind, wave, and tidal current information) the causes of many of the bottom-related surface patterns on the SAR imagery have been identified, an important step for defining the limitations of SAR data for bottom feature detection.

Kasischke, E. A.; Lyzenga, D. R.; Shcuhman, R. A.; Tsen, Y. S.; Termaat, B. S.; Burns, B. A.; Meadows, G. A.

1982-04-01

205

Multiscale salient region detection and salient map generation for synthetic aperture radar image  

NASA Astrophysics Data System (ADS)

Saliency, which refers to distinctive parts of an image that can immediately attract attention without prior information, is significantly meaningful in machine vision, image interpretation, and moreover in quickly extracting vehicle targets or man-made constructions in remote sensing image processing. Different from optical images, synthetic aperture radar (SAR) image has unique characters such as multiplicative speckle noise, local intensity variation, and no color information. However, it is still a challenging work for SAR images to detect salient region and to generate saliency map with the methods performed on optical images. To address this problem, this paper presents a stable salient region detection and salient map generation method for SAR image. We propose a new local complexity metric, which is insensitive to speckle noise and can effectively describe the local intensity variation of SAR image. In addition, via incorporating a stable distribution distance measure, the self-dissimilarity metric is redefined. Using these two components, we construct the saliency metric and generate the salient map. Experimental results demonstrate the accuracy, robustness, and stability of our method for SAR images.

Tang, Tao; Xiang, Deliang; Xie, Huijie

2014-01-01

206

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

SciTech Connect

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

Brock, Billy C.

2010-02-01

207

Disaster phenomena of Wenchuan earthquake in high resolution airborne synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

The devastating Wenchuan Earthquake occurred in Sichuan Province, Southwestern China, with a magnitude of 8.0 on May 12, 2008. Most buildings along the seismic zone were ruined, resulting in infrastructure damage to factories, traffic facilities and power supplies. The earthquake also triggered geological disasters, such as landslides, debris flow, landslide lakes, etc. During the rescue campaign the remote sensing aircrafts of the Chinese Academy of Sciences (CAS), equipped with synthetic aperture radar (SAR) and optical sensors, flew over the disaster area and acquired many high resolution airborne SAR images. We first describe the basic characteristics of SAR imagery. The SAR images of buildings are simulated, and the backscattering mechanism of the buildings is analyzed. Finally, the various disaster phenomena are described and analyzed in the high resolution airborne SAR images. It is shown that certain phenomena of ruins could be identified clearly in high resolution SAR images in proper imaging conditions, while the functional destruction is quite difficult to detect. With calibrated data, the polarmetric SAR interferometry could be used to analyze the scattering mechanism and 3D distribution of the scattering center, which are redound to earthquake damage assessment.

Wang, Chao; Zhang, Hong; Wu, Fan; Zhang, Bo; Tang, Yixian; Wu, Hongan; Wen, Xiaoyang; Yan, Dongmei

2009-05-01

208

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

209

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

210

Unsupervised change detection based on improved Markov random field technique using multichannel synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

Change detection represents an important remote sensing tool in environmental monitoring and disaster management. In this respect, multichannel synthetic aperture radar (SAR) data offer great potential because of their insensitivity to atmospheric and sun-illumination conditions (over optical multispectral data) and the improved discrimination capability they may provide compared to single-channel SAR. The problem of detecting the changes caused by flooding is addressed by a contextual unsupervised technique based on a Markovian data fusion approach. However, the isotropic formulation of Markov random field (MRF) models causes oversmoothing of spatial boundaries in the final change maps. In order to reduce this drawback, an edge-preserving MRF model is proposed and formulated by using energy functions that combine the edge information extracted from the produced edge maps using competitive fuzzy rules and Canny technique, the information conveyed by each SAR channel, and the spatial contextual information. The proposed technique is experimentally validated with semisimulated data and real ASAR-ENVISAT images. Change detection results obtained by the improved MRF model exhibited a higher accuracy than its predecessors for both semisimulated (average 12%) and real (average 6%) data.

Salehi, Sara; Valadan Zoej, Mohammad Javad

2014-01-01

211

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

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

Onstott, Robert G.; Gineris, Denise J.

1990-01-01

212

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

213

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

NASA Technical Reports Server (NTRS)

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

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

2014-01-01

214

Observations and modeling of the current deformation in Afar using Synthetic Aperture Radar Interferometry  

NASA Astrophysics Data System (ADS)

The Afar system is a unique place on Earth where a triple rift junction may be emerging. As the three rifts separating Arabia, Nubia and Somalia plates have not achieved a complete connection at present, I observe a 200 km wide area of complex surface deformation. A variety of extensional structures including a network of faults, fissures, dikes, and volcanic centers are collectively accommodating far field movement of the surrounding plates. Understanding the nature and distribution of the deformation over this vast region is critical since here I observe the transition between established oceanic ridges (the Red Sea and the Aden-Goubbet ridges) and continental deformation. In this study I use the technique of Synthetic Aperture Radar Interferometry (InSAR) to analyze radar data of the Afar region, and to construct a 10 yr timeline of surface displacement over a 200 km by 400 km area. By combining data acquired from ascending and descending passes I construct a two-dimensional velocity maps of the region. The maps show localized extensional deformation across the Asal-Ghoubbet rift segment accommodating the diverging motion of the Arabia-Somalia plates, as well as regional uplift asymmetrically distributed north and south of the Asal Rift area. The vertical velocity map in the rift indicates subsidence of the rift floor with respect to the rift shoulders, accommodated by fault creep. To interpret the observed velocity across the Asal rift I develop a 2-dimensional and a 3-dimensional dislocation model using a combination of dikes, sill and faults embedded in an elastic half space. The forward modeling allows me to place the overall geometry of sub-surface structures and estimate rates of dike and sill inflation, and fault movement. Then I construct a 3-dimensional model to perform a least-squares inversion of the radar-derived velocity maps. The results show an inflating body centered under the Fieale volcano expanding at a rate of 2 106 m3/yr. Faults bordering the rift show both down-dip and opening motion especially at their base where they connect with the inflating body. These findings suggest that the faults react passively to the pressurized magmatic system at depth, and contribute to plate accretion by taking up the injected material in the shallow part of the crust. The sustained process I currently witness in the Asal rift might be characteristic of the 'inter-crisis' state of a magmatic rift system where pressurized fluids accumulate at relatively shallow depth, eventually leading to lateral dike injection as during the seismo-magmatic crisis of 1978.

Tomic, Jelena

215

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

216

Iceberg and ship detection and classification in single, dual and quad polarized synthetic aperture radar  

NASA Astrophysics Data System (ADS)

Iceberg and ship identification in satellite synthetic aperture radar (SAR) data is an essential part of offering an operational iceberg surveillance program. Identification here refers to detection of ocean SAR targets and then classification of these targets as iceberg, ship, or unknown. Maximizing the detection and minimizing incorrect classification of iceberg and ship targets are required. Because coarser resolution satellite SAR data is at times not as intuitive as satellite optical data for manual human interpreted target classification, this process can be labor intensive, subjective, and error prone. Therefore, it is desired that an automated method for iceberg or ship identification be implemented. The methodology investigated here follows a well known standard in supervised pattern recognition, the maximum likelihood-quadratic discriminant function. The goal here in this thesis is to build class models from known iceberg and ship targets. Each class model is based on features that describe targets such as brightness, texture, and shape. Based on these descriptors as training input into the discriminant functions, future unknown targets can be compared with the class model for best fit. The best fit (or minimum distance) is used to assign class status for these unknown targets. One major consideration when using this type of pattern recognition approach is feature selection. Feature selection is based on the notion that some subset (subspace) of the descriptive metrics will lead to improved classification accuracy when comparing discriminant functions. Sequential forward selection and variants of exhaustive search algorithms are implemented and compared. RADARSAT-1, ENVSIAT AP (HH/HV), and EMISAR SAR iceberg and ship targets are used for algorithm training, feature selection, and performance estimation.

Howell, Carl

217

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

NASA Astrophysics Data System (ADS)

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

Ding, Yu

218

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

219

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

220

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

221

Differential Synthetic Aperture Radar Interferometry (DINSAR) for 3D Coastal Geomorphology Reconstruction  

Microsoft Academic Search

Summary This paper introduces a new method for three-dimensional (3D) coastal geomorphology reconstruction using differential synthetic aperture interferometry (DInSAR). The new method is based on an integration between fuzzy B-spline algorithm and DInSAR method. DInSAR algorithm is involved two parts: (i) 3D map simulation which is based on interferogram simulation and (ii) satellite orbit parameters. 3D coastal geomorphology reconstruction is

Maged Marghany

2009-01-01

222

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

NASA Astrophysics Data System (ADS)

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

Higgins, Stephanie

223

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

224

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

225

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

NASA Technical Reports Server (NTRS)

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

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

2005-01-01

226

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

NASA Technical Reports Server (NTRS)

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.

1983-01-01

227

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

228

Inverse problems arising in different synthetic aperture radar imaging systems and a general Bayesian approach for them  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar (SAR) imaging systems are nowadays very common technics of imaging in remote sensing and environment survey. There are different acquisition modes: spotlight, stripmap, scan; different geometries: mono-, bi- and multi-static; and varieties of specific applications: interferometric SAR (InSAR), polarimetric SAR etc. In this paper, first a common inverse problem framework for all of them is given, and then basics of SAR imaging and the classical deterministic inversion methods are presented. Aiming at overcoming the inadequacies of deterministic methods, a general probabilistic Bayesian estimation method is pioneered for solving image reconstruction problems. In particular, two priors which simply allow the automated determination of the hyperparameters in a Type-II likelihood framework are considered. Finally, the performances of the proposed methods on synthetic data.

Zhu, Sha; Mohammad-Djafari, Ali; Li, Xiang; Mao, Junjie

2011-03-01

229

Interferometric synthetic aperture radar deformation data used to interpolate and extrapolate hydraulic head time-series  

NASA Astrophysics Data System (ADS)

A 2004 court decision established that hydraulic head levels within the confined aquifer system of the San Luis Valley (SLV), Colorado be maintained within the range experienced in the years between 1978 and 2000. The current groundwater flow model for this area is not able to predict hydraulic head accurately in the confined aquifer system due to a dearth of calibration points, i.e., hydraulic head measurements, during the time period of interest. The work presented here investigates the extent to which spatially and temporally dense measurements of deformation from Interferometric Synthetic Aperture Radar (InSAR) data could be used to interpolate and extrapolate temporal and spatial gaps in the hydraulic head dataset by performing a calibration at the well locations. We first predicted the magnitude of the seasonal deformation at the confined aquifer well locations by using aquifer thickness/lithology information from well logs and estimates of the aquifer compressibility from the literature. At 11 well locations the seasonal magnitude of the deformation was sufficiently large so as to be reliably measured with InSAR, given the accepted level of uncertainty of the measurement (~ 5 mm). Previous studies in arid or urban areas have shown that high quality InSAR deformation measurements are often collocated with hydraulic head measurements at monitoring wells, making such a calibration approach relatively straightforward. In contrast, the SLV is an agricultural area where many factors, e.g. crop growth, can seriously degrade the quality of the InSAR data. We used InSAR data from the ERS-1 and ERS-2 satellites, which have a temporal sampling of 35 days and a spatial sampling on the order of 10's of meters, and found that the InSAR data were not of sufficiently high quality at any of the 11 selected well locations. Hence, we used geostatistical techniques to analyze the high quality InSAR deformation data elsewhere in the scene and to estimate the deformation at the selected well locations. At the 11 locations we estimated the compressibility parameter that relates the deformation and the hydraulic head. We found that this calibration was effective at 3 of the well locations where the magnitude of the seasonal deformation was > 3 cm, well above the uncertainty of the InSAR measurement. We then estimated the hydraulic head prior to and within the temporal sampling window of the hydraulic head measurements at the 3 well locations. We found that 59% of the InSAR-predicted hydraulic head values agree with the measured hydraulic head values, within the uncertainty of the data. Given our success in extending the hydraulic head data temporally, the next step in our research is to use InSAR data to interpolate spatially between hydraulic head measurements at field sites where the magnitude of the deformation is large enough to be accurately measured by InSAR.

Reeves, J. A.; Knight, R. J.; Zebker, H. A.; Kitanidis, P. K.; Schreuder, W. A.

2013-12-01

230

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

231

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

232

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

233

Three-dimensional subsurface imaging synthetic aperture radar (3D SISAR). Final report, September 22, 1993--September 22, 1996  

SciTech Connect

The concept developed under this applied research and development contract is a novel Ground Penetrating Radar system capable of remotely detecting, analyzing, and mapping buried waste containers from a mobile platform. From the testing and analysis performed to date, the 3-D SISAR has achieved the detection, accurate location, and three-dimensional imaging of buried test objects from a stand-off geometry. Tests have demonstrated that underground objects have been located to within 0.1 meter of their actual position. This work validates that the key elements of the approach are performing as anticipated. The stand-off synthetic aperture radar (SAR) methodology has been demonstrated to be a feasible approach as a remote sensing technique. The radar sensor constructed under this project is providing adequate quality data for imaging, and the matched filters have been demonstrated to provide enhanced target detection. Additional work is on-going in the area of underground propagation and scattering phenomena to provide enhanced depth performance, as the current imaging results have been limited to a few feet of depth underground.

NONE

1998-12-31

234

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

235

Reservoir monitoring and characterization using satellite geodetic data: Interferometric Synthetic Aperture Radar observations from the Krechba field, Algeria  

SciTech Connect

Deformation in the material overlying an active reservoir is used to monitor pressure change at depth. A sequence of pressure field estimates, eleven in all, allow us to construct a measure of diffusive travel time throughout the reservoir. The dense distribution of travel time values means that we can construct an exactly linear inverse problem for reservoir flow properties. Application to Interferometric Synthetic Aperture Radar (InSAR) data gathered over a CO{sub 2} injection in Algeria reveals pressure propagation along two northwest trending corridors. An inversion of the travel times indicates the existence of two northwest-trending high permeability zones. The high permeability features trend in the same direction as the regional fault and fracture zones. Model parameter resolution estimates indicate that the features are well resolved.

Vasco, D.W.; Ferretti, Alessandro; Novali, Fabrizio

2008-05-01

236

Inversion of synthetic aperture radar interferograms for sourcesof production-related subsidence at the Dixie Valley geothermalfield  

SciTech Connect

We used synthetic aperture radar interferograms to imageground subsidence that occurred over the Dixie Valley geothermal fieldduring different time intervals between 1992 and 1997. Linear elasticinversion of the subsidence that occurred between April, 1996 and March,1997 revealed that the dominant sources of deformation during this timeperiod were large changes in fluid volumes at shallow depths within thevalley fill above the reservoir. The distributions of subsidence andsubsurface volume change support a model in which reduction in pressureand volume of hot water discharging into the valley fill from localizedupflow along the Stillwater range frontal fault is caused by drawdownwithin the upflow zone resulting from geothermal production. Our resultsalso suggest that an additional source of fluid volume reduction in theshallow valley fill might be similar drawdown within piedmont faultzones. Shallow groundwater flow in the vicinity of the field appears tobe controlled on the NW by a mapped fault and to the SW by a lineament ofas yet unknown origin.

Foxall, B.; Vasco, D.W.

2006-07-01

237

Feasibility of sea ice typing with synthetic aperture radar (SAR): Merging of Landsat thematic mapper and ERS 1 SAR satellite imagery  

Microsoft Academic Search

ERS 1 synthetic aperture radar (SAR) and Landsat thematic mapper (TM) images were acquired for the same area in the Beaufort Sea, April 16 and 18, 1992. The two image pairs were colocated to the same grid (25-m resolution), and a supervised ice type classification was performed on the TM images in order to classify ice free, nilas, gray ice,

Konrad Steffen; John Heinrichs

1994-01-01

238

Timing of Volcanism on Yunaska Island, Central Aleutian arc, Alaska: an Investigation Applying Multi-temporal Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

The volcanoes of the central Aleutian arc remain largely uninstrumented and unstudied despite numerous eruptions within the last century. Many of these eruptions are not documented and others may not have been observed. Previous synthetic aperture radar (SAR) studies at Westdahl volcano show that radar can be used to relatively date a'a lava flows and to suggest whether some flows are "historic" though not recorded. This is accomplished through comparison of semi-quantitative measurements of surface roughness for young, unvegetated lavas. Because a'a lavas typically become smoother as they weather, they produce less radar backscatter. Thus, lavas that exhibit higher radar backscatter intensities are younger than those with lower backscatter intensities for regions of similar relief and aspect. Located 305 km west of Dutch Harbor, Yunaska has six volcanic centers, of which three have probably been active in the Quaternary. Based on field observations, recent volcanism on Yunaska is associated with the younger of two nested calderas and several smaller vents and cones on the eastern half of the island. Although there is a reported 1937 eruption, it is not clear if this came from fissures north of the caldera or created the intracaldera cinder cone and lava flows. Using a twenty-year composite of SAR data, we establish relative ages for five basaltic andesite lavas from these fissures and from within the young caldera. Clear stratigraphic relationships among three lavas within the caldera provide a check on the accuracy of this technique. The use of SAR to differentiate between young lavas allows us to better document the eruption history of remote volcanoes and to mitigate their hazards.

Brown, M. E.; Nicolaysen, K. P.; Dehn, J.; Myers, J. D.

2003-12-01

239

Tracking lava flow emplacement on the east rift zone of Kilauea, Hawai’i with synthetic aperture radar (SAR) coherence  

USGS Publications Warehouse

Lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior. Although maps are traditionally created through field surveys, remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location. Synthetic aperture radar (SAR) imagery, in particular, can detect changes in a flow field by comparing two images collected at different times with SAR coherence. New lava flows radically alter the scattering properties of the surface, making the radar signal decorrelated in SAR coherence images. We describe a new technique, SAR Coherence Mapping (SCM), to map lava flows automatically from coherence images independent of look angle or satellite path. We use this approach to map lava flow emplacement during the Pu‘u ‘?‘?-Kupaianaha eruption at K?lauea, Hawai‘i. The resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows, as well as the locations of active flow paths. However, the SCM technique is only moderately successful at mapping flows that enter vegetation, which is also often decorrelated between successive SAR images. Along with measurements of planform morphology, we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness. Finally, we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post-emplacement flow subsidence.

Dietterich, Hannah R.; Poland, M.P.; Schmidt, David; Cashman, Katharine V.; Sherrod, David R.; Espinosa, Arkin Tapia

2012-01-01

240

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

241

Imaging algorithms for a strip-map synthetic aperture sonar: minimizing the effects of aperture errors and aperture undersampling  

Microsoft Academic Search

Imaging the sea floor using high-precision synthetic aperture sonar (SAS) techniques is at the stage where the efficiency and the robustness of the various imaging algorithms are of concern. There have been several block processing algorithms developed for relatively narrow-band-, narrow swath-, and narrow beamwidth synthetic aperture systems mainly for use by the synthetic aperture radar (SAR) community. These algorithms

Peter T. Gough; David W. Hawkins

1997-01-01

242

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

243

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

244

Surface deformation measured with interferometric synthetic aperture radar: Case studies of basin and range and Garlock-San Andreas fault  

NASA Astrophysics Data System (ADS)

Interferometric Synthetic Aperture Radar (InSAR) and Global Positioning System (GPS) is widely used to detect ground deformation from varieties of geophysical origins. However, most studies lack the spatial and temporal resolutions to better characterize such observations. The purpose of this research is to use multi-track satellite radar imagery to generate time series to study and monitor vertical ground deformation over large regions such as the Nevada portion of the Basin and Range Province and the western end of the Mojave Desert. We developed an innovative method to remove horizontal movements from InSAR line-of-sight (LOS) observations using a GPS velocity field and subsequently combine the multi-track imagery resulting in one single high spatial resolution map of observed vertical crustal and surface movements. By implementing this technique we detect vertical deformation signals with short and intermediate wavelength signals associated to tectonic processes such as interseismic and postseismic deformation. In Central Nevada Seismic Belt we detect in three independent orbits a broad area of uplift that confirms results of previous studies that associate the origin of this signal to post-seimic deformation of the historic earthquakes at this region. In south-central Nevada we detect several valleys that show a gradual eastward tilt of the valley floors due to deep geodynamical processes. The valleys located at the eastern side of Ruby Mountains show a range decrease that could indicate uplift related to magma intrusion or post-seismic deformation due to older, unrecognized earthquakes. In the Big Bend segment in southern California we detect vertical uplift as expected by mechanical models of interseismic deformation. Additionaly all our velocity maps reveal small wavelength deformation signals of anthropogenic origin.

Greene, Fernando

245

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. PMID:17710188

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

246

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

247

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 W., III; Rangoonwala, Amina; Bannister, Terri

2013-01-01

248

Monitoring cyanobacteria-dominant algal blooms in eutrophicated Taihu Lake in China with synthetic aperture radar images  

NASA Astrophysics Data System (ADS)

Monitoring algal blooms by optical remote sensing is limited by cloud cover. In this study, synthetic aperture radar (SAR) was deployed with the aim of monitoring cyanobacteria-dominant algal blooms in Taihu Lake in cloudy weather. The study shows that dark regions in the SAR images caused by cyanobacterial blooms damped the microwave backscatter of the lake surface and were consistent with the regions of algal blooms in quasi-synchronous optical images, confirming the applicability of SAR for detection of surface blooms. Low backscatter may also be associated with other factors such as low wind speeds, resulting in interference when monitoring algal blooms using SAR data alone. After feature extraction and selection, the dark regions were classified by the support vector machine method with an overall accuracy of 67.74%. SAR can provide a reference point for monitoring cyanobacterial blooms in the lake, particularly when weather is not suitable for optical remote sensing. Multi-polarization and multi-band SAR can be considered for use in the future to obtain more accurate information regarding algal blooms from SAR data.

Wang, Ganlin; Li, Junsheng; Zhang, Bing; Shen, Qian; Zhang, Fangfang

2015-01-01

249

Analysis of ERS 1 synthetic aperture radar data of frozen lakes in northern Montana and implications for climate studies  

USGS Publications Warehouse

Lakes that freeze each winter are good indicators of regional climate change if key parameters, such as freeze-up and breakup date and maximum ice thickness, are measured over a decade-scale time frame. Synthetic aperture radar (SAR) satellite data have proven to be especially useful for measurement of climatologically significant parameters characteristic of frozen lakes. In this paper, five lakes in Glacier National Park, Montana, have been studied both in the field and using Earth Remote-Sensing Satellite (ERS) 1 SAR data during the 1992-1993 winter. The lakes are characterized by clear ice, sometimes with tubular or rounded bubbles, and often with a layer of snow ice on top of the clear ice. They are also often snow covered. Freeze-up is detected quite easily using ERS 1 SAR data as soon as a thin layer of ice forms. The effect of snow ice on the backscatter is thought to be significant but is, as yet, undetermined. On the five lakes studied, relative backscatter was found to increase with ice thickness until a maximum was reached in February. Breakup, an often ill-defined occurrence, is difficult to detect because surface water causes the SAR signal to be absorbed, thus masking the ice below. Comparison of the bubble structure of thaw lakes in northern Alaska with lakes in northern Montana has shown that the ice structure is quite different, and this difference may contribute to differential SAR signature evolution in the lakes of the two areas.

Hall, Dorothy K.; Fagre, Daniel B.; Klasner, Fritz; Linebaugh, Gregg; Liston, Glen E.

1994-01-01

250

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

251

Range ambiguity suppression for multiple-input, multiple-output synthetic aperture radar system using azimuth phase coding technique  

NASA Astrophysics Data System (ADS)

For synthetic aperture radar (SAR), range ambiguity causes a great deterioration in imaging performance. To suppress range ambiguity, the azimuth phase coding (APC) technique stands out for its effectiveness with a low implementation complexity among the available approaches. With proper phase modulation and demodulation, the position of an ambiguous signal is shifted in Doppler spectrum and then part of the ambiguity can be filtered out by an azimuth filter. However, since the suppression performance heavily depends on the system oversampling rate, the APC technique cannot achieve the same suppression performance for a multichannel SAR system compared with a single-channel SAR system. A method to suppress the range ambiguity for multiple-input, multiple-output (MIMO) SAR system based on APC technique is presented. By taking advantage of more phase centers of the MIMO SAR, a proper azimuth beamformer weight vector can be computed to null out the ambiguity position in the azimuth frequency domain and reconstruct the useful signal; thus most of the ambiguity components can be significantly suppressed. Finally, the simulation results validate the effectiveness of the proposed method.

Guo, Lei; Wang, Robert; Deng, Yunkai; Wang, Wei; Luo, Xiulian

2014-01-01

252

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

253

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

254

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

255

SEASAT Synthetic Aperture Radar (SAR) Response to Lowland Vegetation Types in Eastern Maryland and Virginia  

Microsoft Academic Search

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

M. Dennis Krohn; N. M. Milton; Donald B. Segal

1983-01-01

256

Extracting eco-hydrological information of inland wetland from L-band Synthetic Aperture Radar image in Honghe National Nature Reserve, Northeast China  

Microsoft Academic Search

Taking a typical inland wetland of Honghe National Nature Reserve (HNNR), Northeast China, as the study area, this paper studied\\u000a the application of L-band Synthetic Aperture Radar (SAR) image in extracting eco-hydrological information of inland wetland.\\u000a Landsat-5 TM and ALOS PALSAR HH backscatter images were first fused by using the wavelet-IHS method. Based on the fused image\\u000a data, the classification

Yonghua Sun; Huili Gong; Xiaojuan Li; Ruiliang Pu; Shuang Li

2011-01-01

257

On the nonlinear mapping of an ocean wave spectrum into a synthetic aperture radar image spectrum and its inversion  

Microsoft Academic Search

A new, closed nonlinear intergral transformation relation is derived describing the mapping of a two-dimensional ocean wave spectrum into a syntheic aperture radar (SAR) image spectrum. The general integral relatin is expanded in a power series with respect to orders of nonlinearity and velocity bunching. The individual terms of the series can be readily computed using fast Fourier transforms. The

Klaus Hasselmann; Susanne Hasselmann

1991-01-01

258

Surface roughness measuring system. [synthetic aperture radar measurements of ocean wave height and terrain peaks  

NASA Technical Reports Server (NTRS)

Significant height information of ocean waves, or peaks of rough terrain is obtained by compressing the radar signal over different widths of the available chirp or Doppler bandwidths, and cross-correlating one of these images with each of the others. Upon plotting a fixed (e.g., zero) component of the cross-correlation values as the spacing is increased over some empirically determined range, the system is calibrated. To measure height with the system, a spacing value is selected and a cross-correlation value is determined between two intensity images at a selected frequency spacing. The measured height is the slope of the cross-correlation value used. Both electronic and optical radar signal data compressors and cross-correlations are disclosed for implementation of the system.

Jain, A. (inventor)

1978-01-01

259

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

260

Upper ocean fine-scale features in synthetic aperture radar imagery. Part I: Simultaneous satellite and in-situ measurements  

NASA Astrophysics Data System (ADS)

The new generation of synthetic aperture radar (SAR) satellites provides high resolution images that open new opportunities for identifying and studying fine features in the upper ocean. The problem is, however, that SAR images of the sea surface can be affected by atmospheric phenomena (rain cells, fronts, internal waves, etc.). Implementation of in-situ techniques in conjunction with SAR is instrumental for discerning the origin of features on the image. This work is aimed at the interpretation of natural and artificial features in SAR images. These features can include fresh water lenses, sharp frontal interfaces, internal wave signatures, as well as slicks of artificial and natural origin. We have conducted field experiments in the summer of 2008 and 2010 and in the spring of 2011 to collect in-situ measurements coordinated with overpasses of the TerraSAR-X, RADARSAT-2, ALOS PALSAR, and COSMO SkyMed satellites. The in-situ sensors deployed in the Straits of Florida included a vessel-mounted sonar and CTD system to record near-surface data on stratification and frontal boundaries, a bottom-mounted Nortek AWAC system to gather information on currents and directional wave spectra, an ADCP mooring at a 240 m isobath, and a meteorological station. A nearby NOAA NEXRAD Doppler radar station provided a record of rainfall in the area. Controlled releases of menhaden fish oil were performed from our vessel before several satellite overpasses in order to evaluate the effect of surface active materials on visibility of sea surface features in SAR imagery under different wind-wave conditions. We found evidence in the satellite images of rain cells, squall lines, internal waves of atmospheric and possibly oceanic origin, oceanic frontal interfaces and submesoscale eddies, as well as anthropogenic signatures of ships and their wakes, and near-shore surface slicks. The combination of satellite imagery and coordinated in-situ measurements was helpful in interpreting fine-scale features on the sea surface observed in the SAR images and, in some cases, linking them to thermohaline features in the upper ocean. Finally, we have been able to reproduce SAR signatures of freshwater plumes and sharp frontal interfaces interacting with wind stress, as well as internal waves by combining hydrodynamic simulations with a radar imaging algorithm. The modeling results are presented in a companion paper (Matt et al., 2011).

Soloviev, A.; Maingot, C.; Matt, S.; Fenton, J.; Lehner, S.; Brusch, S.; Perrie, W. A.; Zhang, B.

2011-12-01

261

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

262

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

263

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

264

Reconstructing 2-D/3-D Building Shapes from Spaceborne Tomographic Synthetic Aperture Radar Data  

NASA Astrophysics Data System (ADS)

In this paper, we present an approach that allows automatic (parametric) reconstruction of building shapes in 2-D/3-D using TomoSAR point clouds. These point clouds are generated by processing radar image stacks via advanced interferometric technique, called SAR tomography. The proposed approach reconstructs the building outline by exploiting both the available roof and façade information. Roof points are extracted out by employing a surface normals based region growing procedure via selected seed points while the extraction of façade points is based on thresholding the point scatterer density SD estimated by robust M-estimator. Spatial clustering is then applied to the extracted roof points in a way such that each roof cluster represents an individual building. Extracted façade points are reconstructed and afterwards incorporated to the segmented roof cluster to reconstruct the complete building shape. Initial building footprints are derived by employing alpha shapes method that are later regularized. Finally, rectilinear constraints are added to yield better geometrically looking building shapes. The proposed approach is illustrated and validated by examples using TomoSAR point clouds generated from a stack of TerraSAR-X high-resolution spotlight images from ascending orbit only covering two different test areas with one containing relatively smaller buildings in densely populated regions and the other containing moderate sized buildings in the city of Las Vegas.

Shahzad, M.; Zhu, X. X.

2014-08-01

265

Observation of autumn freeze-up in the Beaufort and Chukchi Seas using the ERS 1 synthetic aperture radar  

NASA Astrophysics Data System (ADS)

We present observations of the transition in sea ice backscattering signatures from late summer into early winter in the Beaufort and Chukchi Seas during 1991 and 1992, using data from the ERS 1 synthetic aperture radar (SAR). We employ both analyzed surface temperature fields and direct observations of near-surface temperature from drifting buoys. Consistent with previous surface-based observations, backscattering from sea ice surviving at the end of summer increases strongly and rapidly when temperatures fall below freezing for the final time in the autumn, apparently because of increased volume scattering from bubbles in the upper part of the ice. Areally averaged backscattering sometimes overshoots typical winter multiyear ice values by 1-2 dB, before settling back over a period of approximately a week. The backscattering-temperature link forms a sufficient basis for an algorithm to estimate retrospectively, from time series of SAR images, the date of freeze-up (defined here to be the date on which all liquid water in the bubbly upper layer of surviving sea ice freezes and remains frozen for the duration of the ensuing autumn and winter). We present a prototype algorithm and use it to estimate freeze-up dates in nine Lagrangian cells in the Beaufort Sea during the autumn of 1992. We observe a 12-day spread in freeze-up dates between latitudes of approximately 73°N and 82°N, with dates in the northernmost cells of August 29-30 and those in the southernmost cells of September 7. Two cells at latitudes of 75°N-77°N appear to freeze-up earlier than cells further north, but present uncertainties limit the significance of this observation.

Winebrenner, D. P.; Holt, B.; Nelson, E. D.

1996-07-01

266

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. PolSAR and passive visible light polarimetric imaging, is a largely unexplored area in remote sensing and the main challenge in this research is to identify areas and scenarios where information fusion between the two modes is advantageous for separation of the classes in terms of scattering mechanisms relative to separation achieved with only PolSAR.

Maitra, Sanjit

267

Monitoring of Ground Movement and Generation of Digital Elevation Models Using Interferometric Synthetic Aperture Radar (InSAR) Data  

NASA Astrophysics Data System (ADS)

Interferometric synthetic aperture radar (InSAR) has the potential for measuring deformation of the earth's surface with very high accuracy and for the development of digital elevation models. Both capabilities are of high relevance for ground movement assessment. In addition, when archived raw data is available (post 1992), recent historic movement may be quantifiable. InSAR utilizes satellite-based data acquired at two different times along orbits of a similar trajectory to detect changes in the ground surface elevation. This technique can be used to monitor ground movement for rectangular areas as large as 100 kilometers on a side. Knowledge of topography, geology, trends and mechanics of existing ground movement is required for successful interpretation of InSAR data. The detection of ground surface deformation in terrain of high slope relief terrain is difficult. For ground deformation mapping by means of InSAR it is necessary to separate the motion-related and the topographic phase contributions. This is achieved by using a low resolution digital elevation model (DEM) during the processing of InSAR data. The application of InSAR technology to mining areas provides monitoring of not only the active mine areas but also the adjacent regions that has been affected by mining. Thus InSAR technique proves to be an essential ground monitoring methods in future for mining areas. The results from the InSAR analysis are compared with data from a ground-based monitoring system comprised of measured survey prisms for an open pit mine in Canada. InSAR analysis provided the location of the stable site for relocating the crusher which was affected by movement of pit slope. The presentation will show the application of InSAR technology to various mines in USA and Canada. Besides subsidence evaluation, InSAR data is also used to generate digital elevation models (DEM) and digital terrain models (DTM). The DEM and DTM derived from InSAR data for a mine in Canada is compared with the survey and LIDAR data to demonstrate the applicability of InSAR data to model surface topography.

Panda, B. B.

2013-12-01

268

Automatic change detection in time series of Synthetic Aperture Radar data using a scale-driven approach  

NASA Astrophysics Data System (ADS)

Automatic change detection and change classification from Synthetic Aperture Radar (SAR) images is a difficult task mostly due to the high level of speckle noise inherent to SAR data and the highly non-Gaussian nature of the SAR amplitude information. Several approaches were developed in recent years to deal with SAR specific change detection problems from image pairs and time series of images. Despite these considerable efforts, no satisfying solution to this problem has been found so far. In this paper we present a promising new algorithm for change detection from SAR that is based on a multi-scale analysis of a times series of SAR images. Our approach is composed of three steps, including (1) data enhancement and filtering, (2) multi-scale change detection, and (3) time-series analysis of change detection maps. In the data enhancement and filtering step, we first form time-series of ratio images by dividing all SAR images by a reference acquisition to suppress stationary image information and enhance change signatures. Several methods for reference image selection will be discussed in the paper. The generated ratio images are further log-transformed to create near-Gaussian data and to convert the originally multiplicative noise into additive noise. A subsequent fast non-local mean filter is applied to reduce image noise whilst preserving most of the image details. The filtered log-ratio images are then inserted into a multi-scale change detection algorithm that is composed of: (1) a multi-scale decomposition of the input images using a two-dimensional discrete stationary wavelet transform (2D-SWT); (2) a multi-resolution classification into 'change' and 'no-change' areas; and (3) a scale-driven fusion of the classification results. In a final time-series analysis step the multi-temporal change detection maps are analyzed to identify seasonal, gradual, and abrupt changes. The performance of the developed approach will be demonstrated by application to the monitoring of wildfire progression in an area northeast of Fairbanks, Alaska. In this demonstration study, areas affected by wildfires were identified from a time series of Radarsat-1 SAR images acquired between the years 2000 and 2008. A series of change detection maps were created and analyzed to automatically extract wildfire related change and reject changes unrelated to fires. The accuracy of the resulting change detection maps was assessed using burn scar shapefiles acquired from the Alaska Fire Service. The comparison showed exceptional performance of our algorithm for this application.

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

2013-12-01

269

Gulf of Mexico Ecological Forecasting - Atlantic Bluefin Tuna Population Assessment and Management using Synthetic Aperture Radar (SAR) Data  

NASA Astrophysics Data System (ADS)

Atlantic Bluefin Tuna (Thunnus thynnus) is one of the largest vertebrates in the world and is in high demand in sushi markets. It is a highly political species and is managed internationally by the International Commission for the Conservation of Atlantic Tuna. The Gulf of Mexico and the Mediterranean Sea are the only two known spawning sites in the world. However, there is a large variance in estimates of adult Atlantic Tuna spawning. This research focuses on extending Earth science research results to existing decision-making systems, National Oceanic and Atmospheric Administration (NOAA) and the National Marine Fisheries Service (NMFS)for population assessment and management of Atlantic Bluefin Tuna. The research team is a multi-sector and multi-disciplinary team composed of government (NOAA_NMFS), academic (University of South Florida Institute for Marine Remote Sensing) and commercial (Roffer’s Ocean Fishing Forecasting Service, Inc.) institutions. Their goal is to reduce the variance in the estimates of adult Bluefin Tuna spawning stock abundance in the Gulf of Mexico (GOM). Therefore, this paper will be derived from the innovative use of several earth orbiting satellites focusing on the use of synthetic aperture radar (SAR) data to identify Sargassum, which is a floating marine algae that may be relevant to the presence of Bluefin Tuna aggregations. The SAR imagery will be examined in combination with MODIS and MERIS Chlorophyll-a products to detect fine-scale surface current shear, eddy and frontal features, as well as biological slicks due to the presence of Sargassum. In addition, wind records from NOAA buoy data will be studied to analyze wind patterns in the Gulf of Mexico. The fine-resolution, all-weather capabilities of SAR provide a valuable complement to optical/IR sensors, which are often impacted by cloud cover. This study will provide an assessment of whether or not SAR can contribute to decision support efforts relevant to commercial fisheries through the improvement of the understanding of environmental conditions relative to Tuna. The critically endangered Atlantic Bluefin Tuna (Thunnus thynnus)

Laygo, K.; Jones, I.; Huerta, J.; Holt, B.

2010-12-01

270

Comparing range data across the slow-time dimension to correct 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)

2010-08-17

271

Phase Error Correction for Synthetic-Aperture Phased-Array Imaging Systems  

E-print Network

: If one replaces the ordinary single receiver of a synthetic-aperture radar (SAR) with a linear array is required. Keywords: Synthetic-aperture radar, SAR, synthetic aperture, 3-D imaging, motion compensation of the PredatorTM unmanned aerial vehicle (UAV). It can alternatively operate as a down-looking angle

Fienup, James R.

272

Interferometric synthetic aperture microscopy  

PubMed Central

State-of-the-art methods in high-resolution three-dimensional optical microscopy require that the focus be scanned through the entire region of interest. However, an analysis of the physics of the light–sample interaction reveals that the Fourier-space coverage is independent of depth. Here we show that, by solving the inverse scattering problem for interference microscopy, computed reconstruction yields volumes with a resolution in all planes that is equivalent to the resolution achieved only at the focal plane for conventional high-resolution microscopy. In short, the entire illuminated volume has spatially invariant resolution, thus eliminating the compromise between resolution and depth of field. We describe and demonstrate a novel computational image-formation technique called interferometric synthetic aperture microscopy (ISAM). ISAM has the potential to broadly impact real-time three-dimensional microscopy and analysis in the fields of cell and tumour biology, as well as in clinical diagnosis where in vivo imaging is preferable to biopsy.

Ralston, Tyler S.; Marks, Daniel L.; Carney, P. Scott; Boppart, Stephen A.

2014-01-01

273

Polarimetric C-/X-band Synthetic Aperture Radar Observations of Melting Sea Ice in the Canadian Arctic Archipelago  

NASA Astrophysics Data System (ADS)

Operational ice information services rely heavily on space-borne synthetic aperture radar (SAR) data for the production of ice charts to meet their mandate of providing timely and accurate sea ice information to support safe and efficient marine operations. During the summer melt period, the usefulness of SAR data for sea ice monitoring is limited by the presence of wet snow and melt ponds on the ice surface, which can mask the signature of the underlying ice. This is a critical concern for ice services whose clients (e.g. commercial shipping, cruise tourism, resource exploration and extraction) are most active at this time of year when sea ice is at its minimum extent, concentration and thickness. As a result, there is a need to further quantify the loss of ice information in SAR data during the melt season and to identify what information can still be retrieved about ice surface conditions and melt pond evolution at this time of year. To date the majority of studies have been limited to analysis of single-polarization C-band SAR data. This study will investigate the potential complimentary and unique sea ice information that polarimetric C- and X-band SAR data can provide to supplement the information available from traditional single co-polarized C-band SAR data. A time-series of polarimetric C- and X-band SAR data was acquired over Jones Sound in the Canadian Arctic Archipelago, in the vicinity of the Grise Fiord, Nunavut. Five RADARSAT-2 Wide Fine Quad-pol images and 11 TerraSAR-X StripMap dual-pol (HH/VV) images were acquired. The time-series begins at the onset of melt in early June and extends through advanced melt conditions in late July. Over this period several ponding and drainage events and two snowfall events occurred. Field observations of sea ice properties were collected using an Ice Mass Balance (IMB) buoy, hourly photos from a time-lapse camera deployed on a coastal cliff, and manual in situ measurements of snow thickness and melt pond depth. Where available, clear-sky data from optical sensors (MODIS, Landsat-8, and WorldView) are also used to provide supplementary information on melt pond coverage and evolution. Meteorological data are available from an Environment Canada weather station in Grise Fiord. In this presentation we will discuss the sea ice information provided by each polarization and frequency and evaluate the impact of melt pond evolution on SAR backscatter. Results to date indicate that C- and X-band provide predominantly redundant information, and cross-polarized backscatter (only acquired at C-band) is often very low and near the system noise floor. Early in the melt season a thick wet snow pack is present and both frequencies provide very little ice information. This is attributed to the strong attenuation of the microwave signal by the wet snow. At this time the underlying ice is effectively obscured. During heavily ponded periods backscatter is highly variable, attributed to changing winds and thus variable melt pond surface roughness. In the final week of observations the fast ice in the region is breaking up and open water is present in some images. In these images C-band appears to provide greater contrast between the melting ice and open water than X-band. Analysis of polarimetric parameters is ongoing.

Casey, J. A.; Beckers, J. F.; Brossier, E.; Haas, C.

2013-12-01

274

Synthetic aperture ladar concept for infrastructure monitoring  

NASA Astrophysics Data System (ADS)

Long range surveillance of infrastructure is a critical need in numerous security applications, both civilian and military. Synthetic aperture radar (SAR) continues to provide high resolution radar images in all weather conditions from remote distances. As well, Interferometric SAR (InSAR) and Differential Interferometric SAR (D-InSAR) have become powerful tools adding high resolution elevation and change detection measurements. State of the art SAR systems based on dual-use satellites are capable of providing ground resolutions of one meter; while their airborne counterparts obtain resolutions of 10 cm. D-InSAR products based on these systems could produce cm-scale vertical resolution image products. Deformation monitoring of railways, roads, buildings, cellular antennas, power structures (i.e., power lines, wind turbines, dams, or nuclear plants) would benefit from improved resolution, both in the ground plane and vertical direction. The ultimate limitation to the achievable resolution of any imaging system is its wavelength. State-of-the art SAR systems are approaching this limit. The natural extension to improve resolution is to thus decrease the wavelength, i.e. design a synthetic aperture system in a different wavelength regime. One such system offering the potential for vastly improved resolution is Synthetic Aperture Ladar (SAL). This system operates at infrared wavelengths, ten thousand times smaller than radar wavelengths. This paper presents a laboratory demonstration of a scaled-down infrastructure deformation monitoring with an Interferometric Synthetic Aperture Ladar (IFSAL) system operating at 1.5 ?m. Results show sub-millimeter precision on the deformation applied to the target.

Turbide, Simon; Marchese, Linda; Terroux, Marc; Bergeron, Alain

2014-10-01

275

Synthetic-aperture-radar imaging of the ocean surface using the slightly-rough facet model and a full surface-wave spectrum  

NASA Technical Reports Server (NTRS)

A new model of synthetic-aperture-radar (SAR) imaging of ocean waves is described. The model is based on mapping individual, slightly-rough surface facets through the SAR processor into the image and responses of the facets in the image domain are added together coherently to give the composite image. A windowing technique allows both the orbital motion and the phase velocity of the long waves to be included. It is determined that the azimuthal cut-off is due to a smearing of the response of the facets in the image induced by the random orbital motion of the intermediate large-scale waves and that the focus adjustment that gives the greatest image contrast is half the phase velocity of the dominant long wave. The optimal processing technique, however, may consist of spatially offsetting the multiple looks on the image domain to compensate the propagation of long waves during the integration time of the SAR.

West, James C.; Moore, Richard K.; Holtzman, Julian C.

1990-01-01

276

Application of SEASAT-1 Synthetic Aperture Radar (SAR) data to enhance and detect geological lineaments and to assist LANDSAT landcover classification mapping. [Appalachian Region, West Virginia  

NASA Technical Reports Server (NTRS)

Digital SEASAT-1 synthetic aperture radar (SAR) data were used to enhance linear features to extract geologically significant lineaments in the Appalachian region. Comparison of Lineaments thus mapped with an existing lineament map based on LANDSAT MSS images shows that appropriately processed SEASAT-1 SAR data can significantly improve the detection of lineaments. Merge MSS and SAR data sets were more useful fo lineament detection and landcover classification than LANDSAT or SEASAT data alone. About 20 percent of the lineaments plotted from the SEASAT SAR image did not appear on the LANDSAT image. About 6 percent of minor lineaments or parts of lineaments present in the LANDSAT map were missing from the SEASAT map. Improvement in the landcover classification (acreage and spatial estimation accuracy) was attained by using MSS-SAR merged data. The aerial estimation of residential/built-up and forest categories was improved. Accuracy in estimating the agricultural and water categories was slightly reduced.

Sekhon, R.

1981-01-01

277

Spaceborne synthetic aperture radar: Current status and future directions. A report to the Committee on Earth Sciences, Space Studies Board, National Research Council  

NASA Technical Reports Server (NTRS)

This report provides a context in which questions put forth by NASA's Office of Mission to Planet Earth (OMPTE) regarding the next steps in spaceborne synthetic aperture radar (SAR) science and technology can be addressed. It summarizes the state-of-the-art in theory, experimental design, technology, data analysis, and utilization of SAR data for studies of the Earth, and describes potential new applications. The report is divided into five science chapters and a technology assessment. The chapters summarize the value of existing SAR data and currently planned SAR systems, and identify gaps in observational capabilities needing to be filled to address the scientific questions. Cases where SAR provides complementary data to other (non-SAR) measurement techniques are also described. The chapter on technology assessment outlines SAR technology development which is critical not only to NASA's providing societally relevant geophysical parameters but to maintaining competitiveness in SAR technology, and promoting economic development.

Evans, D. L. (editor); Apel, J.; Arvidson, R.; Bindschadler, R.; Carsey, F.; Dozier, J.; Jezek, K.; Kasischke, E.; Li, F.; Melack, J.

1995-01-01

278

Glacial Rebound Due to Present Day Ice Loss on Greenland Ice Sheet and Canadian Arctic Archipelago Observed by Synthetic Aperture Radar Interferometry  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar Interferometry (InSAR) has been used to measure glacial rebound and estimate ice mass balance in recent years. Relevant studies have covered Jakobshavn Isbrea glacial, Greenland, Vatnajokull Iceland and Antarctic Peninsula by using Radarsat-1, ERS and Alos imagery. We focus on other 2 main contributors to global sea level rise (SLR) in the north Atlantic Region - the Greenland Ice Sheet (GIS) and the Canadian Arctic Archipelago (CAA) in this presentation. We choose a series of test sites on GIS and 1 test site on CAA - Barnes ice cap. New generation SAR satellites Radarsat-2 and TerraSAR-X are applied to these 2 regions respectively. Initial results show the ability that the new satellites data is useful for not only annual velocity but also seasonal variation detections.

Zhao, W.; Amelung, F.; Samsonov, S. V.; Dixon, T. H.; Wdowinski, S.

2013-12-01

279

Tracking lava flow emplacement on the east rift zone of K?lauea, Hawai‘i, with synthetic aperture radar coherence  

NASA Astrophysics Data System (ADS)

Lava flow mapping is both an essential component of volcano monitoring and a valuable tool for investigating lava flow behavior. Although maps are traditionally created through field surveys, remote sensing allows an extraordinary view of active lava flows while avoiding the difficulties of mapping on location. Synthetic aperture radar (SAR) imagery, in particular, can detect changes in a flow field by comparing two images collected at different times with SAR coherence. New lava flows radically alter the scattering properties of the surface, making the radar signal decorrelated in SAR coherence images. We describe a new technique, SAR Coherence Mapping (SCM), to map lava flows automatically from coherence images independent of look angle or satellite path. We use this approach to map lava flow emplacement during the Pu`u `?`?-Kupaianaha eruption at K?lauea, Hawai`i. The resulting flow maps correspond well with field mapping and better resolve the internal structure of surface flows, as well as the locations of active flow paths. However, the SCM technique is only moderately successful at mapping flows that enter vegetation, which is also often decorrelated between successive SAR images. Along with measurements of planform morphology, we are able to show that the length of time a flow stays decorrelated after initial emplacement is linearly related to the flow thickness. Finally, we use interferograms obtained after flow surfaces become correlated to show that persistent decorrelation is caused by post-emplacement flow subsidence.

Dietterich, Hannah R.; Poland, Michael P.; Schmidt, David A.; Cashman, Katharine V.; Sherrod, David R.; Espinosa, Arkin Tapia

2012-05-01

280

Terahertz interferometric synthetic aperture tomography for confocal imaging systems.  

PubMed

Terahertz (THz) interferometric synthetic aperture tomography (TISAT) for confocal imaging within extended objects is demonstrated by combining attributes of synthetic aperture radar and optical coherence tomography. Algorithms recently devised for interferometric synthetic aperture microscopy are adapted to account for the diffraction-and defocusing-induced spatially varying THz beam width characteristic of narrow depth of focus, high-resolution confocal imaging. A frequency-swept two-dimensional TISAT confocal imaging instrument rapidly achieves in-focus, diffraction-limited resolution over a depth 12 times larger than the instrument's depth of focus in a manner that may be easily extended to three dimensions and greater depths. PMID:22513671

Heimbeck, M S; Marks, D L; Brady, D; Everitt, H O

2012-04-15

281

An all-optronic synthetic aperture lidar  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Radar (SAR) is a mature technology that overcomes the diffraction limit of an imaging system's real aperture by taking advantage of the platform motion to coherently sample multiple sections of an aperture much larger than the physical one. Synthetic Aperture Lidar (SAL) is the extension of SAR to much shorter wavelengths (1.5 ?m vs 5 cm). This new technology can offer higher resolution images in day or night time as well as in certain adverse conditions. It could be a powerful tool for Earth monitoring (ship detection, frontier surveillance, ocean monitoring) from aircraft, unattended aerial vehicle (UAV) or spatial platforms. A continuous flow of high-resolution images covering large areas would however produce a large amount of data involving a high cost in term of post-processing computational time. This paper presents a laboratory demonstration of a SAL system complete with image reconstruction based on optronic processing. This differs from the more traditional digital approach by its real-time processing capability. The SAL system is discussed and images obtained from a non-metallic diffuse target at ranges up to 3m are shown, these images being processed by a real-time optronic SAR processor origiinally designed to reconstruct SAR images from ENVISAT/ASAR data.

Turbide, Simon; Marchese, Linda; Terroux, Marc; Babin, François; Bergeron, Alain

2012-09-01

282

Potential of high-resolution detection and retrieval of precipitation fields from X-band spaceborne synthetic aperture radar over land  

NASA Astrophysics Data System (ADS)

X-band Synthetic Aperture Radars (X-SARs), able to image the Earth's surface at metric resolution, may provide a unique opportunity to measure rainfall over land with spatial resolution of about few hundred meters, due to the atmospheric moving-target degradation effects. This capability has become very appealing due to the recent launch of several X-SAR satellites, even though several remote sensing issues are still open. This work is devoted to: (i) explore the potential of X-band high-resolution detection and retrieval of rainfall fields from space using X-SAR signal backscattering amplitude and interferometric phase; (ii) evaluate the effects of spatial resolution degradation by precipitation and inhomogeneous beam filling when comparing to other satellite-based sensors. Our X-SAR analysis of precipitation effects has been carried out using both a TerraSAR-X (TSX) case study of Hurricane "Gustav" in 2008 over Mississippi (USA) and a COSMO-SkyMed (CSK) X-SAR case study of orographic rainfall over Central Italy in 2009. For the TSX case study the near-surface rain rate has been retrieved from the normalized radar cross section by means of a modified regression empirical algorithm (MREA). A relatively simple method to account for the geometric effect of X-SAR observation on estimated rainfall rate and first-order volumetric effects has been developed and applied. The TSX-retrieved rain fields have been compared to those estimated from the Next Generation Weather Radar (NEXRAD) in Mobile (AL, USA). The rainfall detection capability of X-SAR has been tested on the CSK case study using the repeat-pass coherence response and qualitatively comparing its signature with ground-based Mt. Midia C-band radar in central Italy. A numerical simulator to represent the effect of the spatial resolution and the antenna pattern of TRMM satellite Precipitation Radar (PR) and Microwave Imager (TMI), using high-resolution TSX-retrieved rain images, has been also set up in order to evaluate the rainfall beam filling phenomenon. As expected, the spatial average can modify the statistics of the high-resolution precipitation fields, strongly reducing its dynamics in a way non-linearly dependent on the rain rate local average value.

Marzano, F. S.; Mori, S.; Chini, M.; Pulvirenti, L.; Pierdicca, N.; Montopoli, M.; Weinman, J. A.

2011-03-01

283

Potential of high-resolution detection and retrieval of precipitation fields from X-band spaceborne Synthetic Aperture Radar over land  

NASA Astrophysics Data System (ADS)

X-band Synthetic Aperture Radars (X-SARs), able to image the Earth's surface at metric resolution, may provide a unique opportunity to measure rainfall over land with spatial resolution of about few hundred meters, due to the atmospheric moving-target degradation effects. This capability has become very appealing due to the recent launch of several X-SAR satellites, even though several remote sensing issues are still open. This work is devoted to: (i) explore the potential of X-band high-resolution detection and retrieval of rainfall fields from space using X-SAR signal backscattering amplitude and interferometric phase; (ii) evaluate the effects of spatial resolution degradation by precipitation and inhomogeneous beam filling when comparing to other satellite-based sensors. Our X-SAR analysis of precipitation effects has been carried out using both a TerraSAR-X (TSX) case study of Hurricane "Gustav" in 2008 over Mississippi (USA) and a COSMO-SkyMed (CSK) X-SAR case study of orographic rainfall over Central Italy in 2009. For the TSX case study the near-surface rain rate has been retrieved from the normalized radar cross section by means of a modified regression empirical algorithm (MREA). A relatively simple method to account for the geometric effect of X-SAR observation on estimated rainfall rate and first-order volumetric effects has been developed and applied. The TSX-retrieved rain fields have been compared to those estimated from the Next Generation Weather Radar (NEXRAD) in Mobile (AL, USA). The rainfall detection capability of X-SAR has been tested on the CSK case study using the repeat-pass coherence response and qualitatively comparing its signature with ground-based Mt. Midia C-band radar in central Italy. A numerical simulator to represent the effect of the spatial resolution and the antenna pattern of TRMM satellite Precipitation Radar (PR) and Microwave Imager (TMI), using high-resolution TSX-retrieved rain images, has been also set up in order to evaluate the rainfall beam filling phenomenon. As expected, the spatial average can modify the statistics of the high-resolution precipitation fields, strongly reducing its dynamics in a way non-linearly dependent on the rainrate local average value.

Marzano, F. S.; Mori, S.; Chini, M.; Pulvirenti, L.; Pierdicca, N.; Montopoli, M.; Weinman, J. A.

2010-09-01

284

Structural and stratigraphic features and ERS 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in NW Alaska, winter 1991-1992  

NASA Technical Reports Server (NTRS)

Changes in Earth Remote-Sensing Satellite (ERS) 1 C band synthetic aperture radar (SAR) backscatter intensity (sigma(exp 0)) from ice growing on shallow tundra lakes at three locations in NW Alaska are described. Ice core analysis shows that all lakes on the coast at Barrow the ice, whether floating or frozen to the bottom, includes an inclusion-free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth. The clear ice may also be overlain by a discontinuous layer of bubbly snow ice. Backscatter is low (-16 to -22 dB) at the time of initial ice formation, probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar. As the ice thickens during the autumn, backscatter rises steadily. Once the ice freezes to the lake bottom, regardless of the presence of foward scattering tubular bubbles, low backscatter values of -17 to -18 dB are caused by absorption of the radar signal in the lake bed. For ice that remains afloat all winter the ice-water interface and the tubular bubbles combine, presumably via an incoherent double-bounce mechanism, to cause maximum backscatter values of the order of -6 to -7 dB. The sigma(exp 0) saturates at -6 to -7 dB before maximum ice thickness and tubular bubble content are attained. A simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice. During the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland. This reversal may be related to the ice surface topography and wetness plus the effects of a longer, cooler melt period by the coast. Time series of backscatter variations from shallow tundra lakes are a record of (1) the development of tubular bubbles in the ice and, by association, changes in the gas content of the underlying water and (2) the freezing of ice to the bottoms of the lakes and therefore lake bathymetry and water availability. SAR is also able to detect the onset of lake ice growth in autumn and the initiation of the spring thaw and thus has potential for monitoring high-altitude lake ice growth and decay processes in relation to climate variability.

Jeffries, M. O.; Morris, K.; Weeks, W. F.; Wakabayashi, H.

1994-01-01

285

Structural and stratigraphic features and ERS 1 synthetic aperture radar backscatter characteristics of ice growing on shallow lakes in NW Alaska, winter 1991-1992  

NASA Astrophysics Data System (ADS)

Changes in ERS 1 C band synthetic aperture radar (SAR) backscatter intensity (?°) from ice growing on shallow tundra lakes at three locations in NW Alaska are described. Ice core analysis shows that at all lakes on the coast at Barrow the ice, whether floating or frozen to the bottom, includes an inclusion-free layer overlying a layer of ice with tubular bubbles oriented parallel to the direction of growth. The clear ice may also be overlain by a discontinuous layer of bubbly snow ice. Backscatter is low (-16 to -22 dB) at the time of initial ice formation, probably due to the specular nature of the upper and lower ice surfaces causing the radar pulse to be reflected away from the radar. As the ice thickens during the autumn, backscatter rises steadily. Once the ice freezes to the lake bottom, regardless of the presence of forward scattering tubular bubbles, low backscatter values of-17 to -18 dB are caused by absorption of the radar signal in the lake bed. For ice that remains afloat all winter the ice-water interface and the tubular bubbles combine, presumably via an incoherent double-bounce mechanism, to cause maximum backscatter values of the order of -6 to -7 dB. The ?° saturates at -6 to -7 dB before maximum ice thickness and tubular bubble content are attained. A simple ice growth model suggests that the layer of ice with tubular bubbles need be only a few centimeters thick midway through the growth season to cause maximum backscatter from floating ice. During the spring thaw a previously unreported backscatter reversal is observed on the floating and grounded portions of the coastal lakes but not on the lakes farther inland. This reversal may be related to the ice surface topography and wetness plus the effects of a longer, cooler melt period by the coast. Time series of backscatter variations from shallow tundra lakes are a record of (1) the development of tubular bubbles in the ice and, by association, changes in the gas content of the underlying water and (2) the freezing of ice to the bottoms of the lakes and therefore lake bathymetry and water availability. SAR is also able to detect the onset of lake ice growth in autumn and the initiation of the spring thaw and thus has potential for monitoring high-latitude lake ice growth and decay processes in relation to climate variability.

Jeffries, M. O.; Morris, K.; Weeks, W. F.; Wakabayashi, H.

1994-11-01

286

Surface Deformation of Augustine Volcano, 1992-2005, from Multiple-Interferogram Processing Using a Refined Small Baseline Subset (SBAS) Interferometric Synthetic Aperture Radar (InSAR) Approach  

USGS Publications Warehouse

Augustine Volcano is an active stratovolcano located in southwestern Cook Inlet, about 280 kilometers southwest of Anchorage, Alaska. The volcano produced six significant explosive eruptions between 1812 and 1986. Augustine eruptions typically have an explosive onset followed by dome building. The most recent eruption began on January 11, 2006. We applied the small baseline subset (SBAS) interferometric synthetic aperture radar (InSAR) technique to measure ground surface deformation during 1992-2005 with the use of European Remote Sensing Satellites 1 and 2 (ERS-1 and ERS-2) radar imagery. Through a multiple-interferogram approach, atmospheric delay artifacts, which hinder conventional InSAR measurements, are significantly reduced by spatial and temporal filtering. This allows us to retrieve time-series deformation over coherent points at millimeter-scale accuracy. The deformation results from two independent satellite tracks agree with each other, suggesting 2 to 8 cm wholesale uplift of Augustine Volcano from 1992 to 2005. Global Positioning System (GPS) data acquired in September 2004 and October 2005 confirm the SBAS InSAR results. A preliminary model consisting of a contracting source at 2 to 4 km depth and an inflating source at 7 to 12 km depth fits the observed deformation reasonably well. We interpret the deeper source as a long-term magma storage zone and the shallower source as a subsidiary reservoir that was tapped during the 2006 eruption. The shallow source corresponds approximately to the location of the volcano-tectonic earthquakes that preceded and followed the 1976 and 2006 eruptions, respectively.

Lee, Chang-Wook; Lu, Zhong; Jung, Hyung-Sup; Won, Joong-Sun; Dzurisin, Daniel

2010-01-01

287

Glacier surface velocity estimation in the West Kunlun Mountain range from L-band ALOS/PALSAR images using modified synthetic aperture radar offset-tracking procedure  

NASA Astrophysics Data System (ADS)

Glacier movement is closely related to changes in climatic, hydrological, and geological factors. However, detecting glacier surface flow velocity with conventional ground surveys is challenging. Remote sensing techniques, especially synthetic aperture radar (SAR), provide regular observations covering larger-scale glacier regions. Glacier surface flow velocity in the West Kunlun Mountains using modified offset-tracking techniques based on ALOS/PALSAR images is estimated. Three maps of glacier flow velocity for the period 2007 to 2010 are derived from procedures of offset detection using cross correlation in the Fourier domain and global offset elimination of thin plate smooth splines. Our results indicate that, on average, winter glacier motion on the North Slope is 1 cm/day faster than on the South Slope-a result which corresponds well with the local topography. The performance of our method as regards the reliability of extracted displacements and the robustness of this algorithm are discussed. The SAR-based offset tracking is proven to be reliable and robust, making it possible to investigate comprehensive glacier movement and its response mechanism to environmental change.

Ruan, Zhixing; Guo, Huadong; Liu, Guang; Yan, Shiyong

2014-01-01

288

Ground displacements caused by aquifer-system water-level variations observed using interferometric synthetic aperture radar near Albuquerque, New Mexico  

USGS Publications Warehouse

Six synthetic aperture radar (SAR) images were processed to form five unwrapped interferometric (InSAR) images of the greater metropolitan area in the Albuquerque Basin. Most interference patterns in the images were caused by range displacements resulting from changes in land-surface elevation. Loci of land- surface elevation changes correlate with changes in aquifer-system water levels and largely result from the elastic response of the aquifer-system skeletal material to changes in pore-fluid pressure. The magnitude of the observed land-surface subsidence and rebound suggests that aquifer-system deformation resulting from ground-water withdrawals in the Albuquerque area has probably remained in the elastic (recoverable) range from July 1993 through September 1999. Evidence of inelastic (permanent) land subsidence in the Rio Rancho area exists, but its relation to compaction of the aquifer system is inconclusive because of insufficient water-level data. Patterns of elastic deformation in both Albuquerque and Rio Rancho suggest that intrabasin faults impede ground- water-pressure diffusion at seasonal time scales and that these faults are probably important in controlling patterns of regional ground-water flow.

Heywood, Charles E.; Galloway, Devin L.; Stork, Sylvia V.

2002-01-01

289

NOAA satellite ocean remote sensing near real-time system for providing synthetic aperture radar data for marine and coastal applications  

SciTech Connect

The National Environmental Satellite, Data, and Information Service (NESDIS) of the National Oceanic and Atmospheric Administration (NOAA) in partnership with the National Aeronautics and Space Administration, the Naval Oceanographic Office, the Naval Research Laboratory (NRL), the University of Alaska at Fairbanks (UAF), and the Canadian Ice Service has constructed a near real-time data system for providing satellite synthetic aperture radar (SAR) imagery to U.S. Government users. Data processed in near real-time at the Alaska SAR Facility of the UAF, at the Gatineau Ground Station in Canada, and the Tromso Satellite Station in Norway (with the McMurdo Ground Station in Antarctica to be added in the future), are brought electronically to the NOAA/NESDIS Satellite Active Archive where they are provided to US Government subscribers in near real-time or retrospectively. A SAR data display and analysis system developed by NRL is provided to users to aid in applying these data to marine and coastal environmental problems. Targeted applications include operational sea and lake ice analysis, river ice jam monitoring, flood mapping, oil spill tracking, ocean feature detection, fisheries management and enforcement, fisheries studies, and river plume monitoring. Initial coastal and marine users include the US National Ice Center, the NOAA CoastWatch Regional Nodes and the US Coast Guard.

Pichel, W.G.; Stone, R.N.; Tseng, W. [NOAA/National Environmental Satellite, Data, and Information Service, Washington, DC (United States)

1997-06-01

290

Analysis of data acquired by synthetic aperture radar and LANDSAT Multispectral Scanner over Kershaw County, South Carolina, during the summer season  

NASA Technical Reports Server (NTRS)

Data acquired by synthetic aperture radar (SAR) and LANDSAT multispectral scanner (MSS) were processed and analyzed to derive forest-related resources inventory information. The SAR data were acquired by using the NASA aircraft X-band SAR with linear (HH, VV) and cross (HV, VH) polarizations and the SEASAT L-band SAR. After data processing and data quality examination, the three polarization (HH, HV, and VV) data from the aircraft X-band SAR were used in conjunction with LANDSAT MSS for multisensor data classification. The results of accuracy evaluation for the SAR, MSS and SAR/MSS data using supervised classification show that the SAR-only data set contains low classification accuracy for several land cover classes. However, the SAR/MSS data show that significant improvement in classification accuracy is obtained for all eight land cover classes. These results suggest the usefulness of using combined SAR/MSS data for forest-related cover mapping. The SAR data also detect several small special surface features that are not detectable by MSS data.

Wu, S. T.

1983-01-01

291

Arizona Department of Water Resources use of ALOS Interferometric Synthetic Aperture Radar (InSAR) data to Identify Areas of Land Subsidence in Southeastern Arizona  

NASA Astrophysics Data System (ADS)

The Arizona Department of Water Resources (ADWR) has been collecting, processing, and analyzing Interferometric Synthetic Aperture Radar (InSAR) data since 2005. The Alaska Satellite Facility's Americas ALOS Data Node (AADN) has provided ADWR's InSAR program with the necessary data to identify new land subsidence features in Southeastern Arizona within Cochise County. ADWR has used the ALOS InSAR data in conjunction with ADWR groundwater level data to better understand the groundwater conditions in relation to the current land subsidence data and attempt to better understand the complex basin hydrology of the area. ADWR and the Arizona Geological Survey (AZGS) have used the ALOS InSAR data to also identify areas where conditions may exist for earth fissure formation. Further ground investigations by the AZGS have revealed unmapped earth fissures in potential earth fissure risk areas identified by ALOS InSAR data. Previously mapped earth fissures by the AZGS also fall within some of these earth fissure risk areas.

Conway, B. D.

2011-12-01

292

Broadband synthetic aperture geoacoustic inversion.  

PubMed

A typical geoacoustic inversion procedure involves powerful source transmissions received on a large-aperture receiver array. A more practical approach is to use a single moving source and/or receiver in a low signal to noise ratio (SNR) setting. This paper uses single-receiver, broadband, frequency coherent matched-field inversion and exploits coherently repeated transmissions to improve estimation of the geoacoustic parameters. The long observation time creates a synthetic aperture due to relative source-receiver motion. This approach is illustrated by studying the transmission of multiple linear frequency modulated (LFM) pulses which results in a multi-tonal comb spectrum that is Doppler sensitive. To correlate well with the measured field across a receiver trajectory and to incorporate transmission from a source trajectory, waveguide Doppler and normal mode theory is applied. The method is demonstrated with low SNR, 100-900?Hz LFM pulse data from the Shallow Water 2006 experiment. PMID:23862809

Tan, Bien Aik; Gerstoft, Peter; Yardim, Caglar; Hodgkiss, William S

2013-07-01

293

Active salt tectonics in the Needles District, Canyonlands (Utah) as detected by interferometric synthetic aperture radar and point target analysis: 1992-2002  

NASA Astrophysics Data System (ADS)

The Needles District in Canyonlands National Park, Utah, is known for its well-exposed array of extensional faults, which are thought to be produced by gravity-driven extension and downward flexure of a thin sandstone plate into the Colorado River canyon in response to dissolution and flow of underlying evaporites (halite and gypsum). Owing to a lack of precise geodetic data, however, it remains uncertain if and to what extent those extensional faults are currently deforming. In this study we use synthetic aperture radar (SAR) data to search for ongoing, decadal ground displacements, by applying both a stacking interferometric SAR (InSAR) analysis and Interferometric Point Target Analysis (IPTA). Our results show that most of the Needles District is indeed undergoing deformation now at a maximum rate of 2-3 mm/year away from the satellite, looking roughly westward with an incidence angle of about 20°. Also, we identify a localized region along the riverbank that is uplifting at a rate of 2-3 mm/year. We estimate the measurement precision to be better than 0.8 mm/year, except along the riverbank where the errors are probably higher than this, by analyzing residual signals and carrying out a signal recovery experiment using synthetic two dimensional correlated noise. The deforming region is almost totally bounded by the Colorado River canyon to the west and north, a rapidly subsiding, east-west trending graben to the south, and a relatively sharp to very diffuse deformation gradient to the east. We observe deformation patterns that were previously undetected. These include an area in the southwestern part of the deforming region that is deforming at higher rates than anywhere else in the Needles but that has little surface extensional faulting. Rates of deformation are lower but still clearly significant further north, in a region of spectacularly exposed fault blocks that have been previously studied in considerable detail.

Furuya, M.; Mueller, K.; Wahr, J.

2007-06-01

294

Synthetic aperture sonar: An analysis of beamforming and system design  

Microsoft Academic Search

A model to improve predictions of synthetic aperture processing performance as applied to active sonar is described. Models to date have been based on the theories developed for radar systems and have been limited primarily to the study of short range, high-frequency active systems. The present study follows a general approach to develop a computer model to give the beam

E. Pusone; L. Lloyd

1984-01-01

295

Relationships between autofocus methods for SAR and self-survey techniques for SONAR. [Synthetic Aperture Radar (SAR)  

SciTech Connect

Autofocus methods in SAR and self-survey techniques in SONAR have a common mathematical basis in that they both involve estimation and correction of phase errors introduced by sensor position uncertainties. Time delay estimation and correlation methods have been shown to be effective in solving the self-survey problem for towed SONAR arrays. Since it can be shown that platform motion errors introduce similar time-delay estimation problems in SAR imaging, the question arises as to whether such techniques could be effectively employed for autofocus of SAR imagery. With a simple mathematical model for motion errors in SAR, we will show why such correlation/time-delay techniques are not nearly as effective as established SAR autofocus algorithms such as phase gradient autofocus or sub-aperture based methods. This analysis forms an important bridge between signal processing methodologies for SAR and SONAR. 5 refs., 4 figs.

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

1991-01-01

296

Simulation of the Effects of Hard Limiting on Image Quality of Synthetic Aperture Radar. [onboard Landsat Satellite  

NASA Technical Reports Server (NTRS)

Starting with a magnetic tape of a scene viewed by the Landsat satellite, the radar return of reflectors whose average intensity matched that of the picture elements in the scene has been simulated. The returns were processed in three ways: normally or with no quantization, with a procedure simulation IF hard limiting, and with a procedure simulating video (baseband) hard limiting. For each type of processing an image for a one, two, and four-look system has been developed. It was found that IF limiting is slightly better than video limiting, while both can be reasonable trade-offs of image quality for reduced data rates when the number of looks is four or less. These conclusions are supported by photographs representing the different processing techniques.

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

1976-01-01

297

Forest above ground biomass estimation and forest/non-forest classification for Odisha, India, using L-band Synthetic Aperture Radar (SAR) data  

NASA Astrophysics Data System (ADS)

Tropical forests contribute to approximately 40 % of the total carbon found in terrestrial biomass. In this context, forest/non-forest classification and estimation of forest above ground biomass over tropical regions are very important and relevant in understanding the contribution of tropical forests in global biogeochemical cycles, especially in terms of carbon pools and fluxes. Information on the spatio-temporal biomass distribution acts as a key input to Reducing Emissions from Deforestation and forest Degradation Plus (REDD+) action plans. This necessitates precise and reliable methods to estimate forest biomass and to reduce uncertainties in existing biomass quantification scenarios. The use of backscatter information from a host of allweather capable Synthetic Aperture Radar (SAR) systems during the recent past has demonstrated the potential of SAR data in forest above ground biomass estimation and forest / nonforest classification. In the present study, Advanced Land Observing Satellite (ALOS) / Phased Array L-band Synthetic Aperture Radar (PALSAR) data along with field inventory data have been used in forest above ground biomass estimation and forest / non-forest classification over Odisha state, India. The ALOSPALSAR 50 m spatial resolution orthorectified and radiometrically corrected HH/HV dual polarization data (digital numbers) for the year 2010 were converted to backscattering coefficient images (Schimada et al., 2009). The tree level measurements collected during field inventory (2009-'10) on Girth at Breast Height (GBH at 1.3 m above ground) and height of all individual trees at plot (plot size 0.1 ha) level were converted to biomass density using species specific allometric equations and wood densities. The field inventory based biomass estimations were empirically integrated with ALOS-PALSAR backscatter coefficients to derive spatial forest above ground biomass estimates for the study area. Further, The Support Vector Machines (SVM) based Radial Basis Function classification technique was employed to carry out binary (forest-non forest) classification using ALOSPALSAR HH and HV backscatter coefficient images and field inventory data. The textural Haralick's Grey Level Cooccurrence Matrix (GLCM) texture measures are determined on HV backscatter image for Odisha, for the year 2010. PALSAR HH, HV backscatter coefficient images, their difference (HHHV) and HV backscatter coefficient based eight textural parameters (Mean, Variance, Dissimilarity, Contrast, Angular second moment, Homogeneity, Correlation and Contrast) are used as input parameters for Support Vector Machines (SVM) tool. Ground based inputs for forest / non-forest were taken from field inventory data and high resolution Google maps. Results suggested significant relationship between HV backscatter coefficient and field based biomass (R2 = 0.508, p = 0.55) compared to HH with biomass values ranging from 5 to 365 t/ha. The spatial variability of biomass with reference to different forest types is in good agreement. The forest / nonforest classified map suggested a total forest cover of 50214 km2 with an overall accuracy of 92.54 %. The forest / non-forest information derived from the present study showed a good spatial agreement with the standard forest cover map of Forest Survey of India (FSI) and corresponding published area of 50575 km2. Results are discussed in the paper.

Suresh, M.; Kiran Chand, T. R.; Fararoda, R.; Jha, C. S.; Dadhwal, V. K.

2014-11-01

298

Applications of Radarsat-1 synthetic aperture radar imagery to assess hurricane-related flooding of coastal Louisiana  

USGS Publications Warehouse

The Louisiana coast is subjected to hurricane impacts including flooding of human settlements, river channels and coastal marshes, and salt water intrusion. Information on the extent of flooding is often required quickly for emergency relief, repairs of infrastructure, and production of flood risk maps. This study investigates the feasibility of using Radarsat-1 SAR imagery to detect flooded areas in coastal Louisiana after Hurricane Lili, October 2002. Arithmetic differencing and multi-temporal enhancement techniques were employed to detect flooding and to investigate relationships between backscatter and water level changes. Strong positive correlations (R2=0.7-0.94) were observed between water level and SAR backscatter within marsh areas proximate to Atchafalaya Bay. Although variations in elevation and vegetation type did influence and complicate the radar signature at individual sites, multi-date differences in backscatter largely reflected the patterns of flooding within large marsh areas. Preliminary analyses show that SAR imagery was not useful in mapping urban flooding in New Orleans after Hurricane Katrina's landfall on 29 August 2005. ?? 2005 Taylor & Francis.

Kiage, L.M.; Walker, N.D.; Balasubramanian, S.; Babin, A.; Barras, J.

2005-01-01

299

Sinking Coastlines: Land Subsidence at Aquaculture Facilities in the Yellow River Delta, China, measured with Differential Synthetic Aperture Radar (D-InSAR)  

NASA Astrophysics Data System (ADS)

Land subsidence in river deltas is a global problem. It heightens storm surges, salinates groundwater, intensifies river flooding, destabilizes infrastructure and accelerates shoreline retreat. Measurements of delta subsidence typically rely on point measures such as GPS devices, tide gauges or extensometers, but spatial coverage is needed to fully assess risk across river deltas. Differential Interferometric Synthetic Aperture Radar (D-InSAR) is a satellite-based technique that can provide maps of ground deformation with mm to cm-scale vertical resolution. We apply D-InSAR to the coast of the Yellow River Delta in China, which is dominated by aquaculture facilities and has experienced severe coastal erosion in the last twenty years. We extract deformation patterns from dry land adjacent to aquaculture facilities along the coast, allowing the first measurements of subsidence at a non-urban delta shoreline. Results show classic cones-of-depression surrounding aquaculture facilities, likely due to groundwater pumping. Subsidence rates are as high as 250 mm/y at the largest facility on the delta. These rates exceed local and global average sea level rise by nearly two orders of magnitude. If these rates continue, large aquaculture facilities in the area could induce more than a meter of relative sea level rise every five years. Given the global explosion in fish farming in recent years, these results also suggest that similar subsidence and associated relative sea level rise may present a significant hazard for other Asian megadeltas. False-color MODIS image of the Yellow River delta in September 2012. Water appears dark blue, highlighting the abundance of aquaculture facilities along the coast. Green land is primarily agricultural; brown is urban. Red boxes indicate locations of aquaculture facilities examined in this study. Figure from Higgins, S., Overeem, I., Tanaka, A., & Syvitski, J.P.M., (2013), Land Subsidence at Aquaculture Facilities in the Yellow River Delta, Geophysical Research Letters, in press.

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

2013-12-01

300

Integration of optical and synthetic aperture radar (SAR) images to differentiate grassland and alfalfa in Prairie area  

NASA Astrophysics Data System (ADS)

Alfalfa presents a huge potential biofuel source in the Prairie Provinces of Canada. However, it remains a challenge to find an ideal single satellite sensor to monitor the regional spatial distribution of alfalfa on an annual basis. The primary interest of this study is to identify alfalfa spatial distribution through effectively differentiating alfalfa from grasslands, given their spectral similarity and same growth calendars. MODIS and RADARSAT-2 ScanSAR narrow mode were selected for regional-level grassland and alfalfa differentiation in the Prairie Provinces, due to the high frequency revisit of MODIS, the weather independence of ScanSAR as well as the large area coverage and the complementary characteristics SAR and optical images. Combining MODIS and ScanSAR in differentiating alfalfa and grassland is very challenging, since there is a large spatial resolution difference between MODIS (250 m) and ScanSAR narrow (50 m). This study investigated an innovative image fusion technique for combining MODIS and ScanSAR and obtaining a synthetic image which has the high spatial details derived from ScanSAR and the colour information from MODIS. The field trip was arranged to collect ground truth to label and validate the classification results. The fusion classification result shows significant accuracy improvement when compared with either ScanSAR or MODIS alone or with other commonly-used data combination methods, such as multiple files composites. This study has shown that the image fusion technique used in this study can combine the structural information from high resolution ScanSAR and colour information from MODIS to significantly improve the classification accuracy between alfalfa and grassland.

Hong, Gang; Zhang, Aining; Zhou, Fuqun; Brisco, Brian

2014-05-01

301

Region-enhanced imaging for sparse-aperture passive radar  

NASA Astrophysics Data System (ADS)

We present the application of a recently-developed region-enhanced synthetic aperture radar (SAR) image reconstruction technique to the problem of passive radar imaging. One goal in passive radar imaging is to form images of aircraft using signals transmitted by commercial radio and television stations, which then get reflected from the objects of interest. This involves reconstructing an image from sparse samples of its Fourier transform. Due to the sparse nature of the aperture, a conventional image formation approach based on direct Fourier transformation results in quite dramatic artifacts in the image, as compared to the case of active SAR imaging. The region-enhanced image formation method we consider appears to significantly reduce such artifacts, and preserve the features of the imaged object. Furthermore, this approach exhibits robustness to measurement noise. We demonstrate our results using data based on electromagnetic simulations.

Cetin, Mujdat; Lanterman, Aaron D.

2004-09-01

302

Deployable Synthetic Aperture Radar Reflector  

E-print Network

performance using the finite element software ABAQUS, and demonstrated by designing, constructing and testing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21 2.3 Preliminary Finite Element Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 25 3. The performance of the connections between different sheets, made with woven-glass tape, has been determined

Pellegrino, Sergio

303

Interferometric synthetic aperture radar observation of vertical land displacement in the vicinity of the All-American Canal at the United States and Mexico border  

NASA Astrophysics Data System (ADS)

Interferometric Synthetic Aperture Radar (InSAR) provided a synoptic view of the status of groundwater levels in the vicinity of the All-American Canal (AAC) by measuring vertical land displacements. The European Remote Sensing satellite SAR images were used to produce surface deformation maps. The full time period (1992-2000) was divided to two shorter periods (early and late) (1992-97 and 1996-2000). For low coherence areas such as agricultural fields in the Mexicali Valley, Persistent Scatterers InSAR (PSInSAR) was used to detect any deformation signals. The surface deformation maps from InSAR indicated that there were insignificant vertical land displacements in the vicinity of the AAC. However, the surrounding areas of the East Mesa Geothermal Field (EMGF) were subsiding over the full observation period (-38 mm/year). The maximum subsidence rate at the EMGF was reduced by 21% between the early (-43 mm/year) and late (-34 mm/year) periods. The AAC was within the edges of the spatial extent of the EMGF subsidence, especially during the early period, which was associated with a high averaged net geothermal production. The maximum subsidence on the East Highline Canal was -9.5 +/- 0.5 cm and -2.4 +/- 0.8 cm for the early and late periods, respectively. Results from PSInSAR in Mexicali City and the Mexicali Valley showed insignificant displacements. This lack of deformation indicated that there was no measurable surface deformation in the areas, but validation data were not available. The most interesting phenomenon is the high density of persistent scatterers in the areas between the Andrade Mesa and the Mexicali Valley, and the Sand Hills dunes. Forward modeling was conducted to characterize the reservoir zone of the EMGF based on the InSAR displacement over the full time period. Inputs to the model were the maximum subsidence (-3.8 cm) and depth of the reservoir, the radius of the reservoir and Poisson's ratio. An interactive approach was conducted to find the radius of the reservoir and Poisson's ratio. The radius of the EMGF reservoir is between 1,900 m and 2,000 m with Poisson's ratios between 0.180 and 0.205 at a deforming depth of 800 m.

Han, Joo-Yup

304

Detection and measurement of land subsidence using interferometric synthetic aperture radar and Global Positioning System, San Bernardino County, Mojave Desert, California  

USGS Publications Warehouse

Land subsidence associated with ground-water-level declines has been recognized as a potential problem in parts of the Mojave Desert, California. Ground water has been the primary source of domestic, agricultural, and municipal water supplies in the desert since the early 1900s. Pumping of ground water from the Mojave River and Morongo ground-water basins in the southwestern Mojave Desert resulted in water-level declines of more than 30 meters (100 feet) between the 1950s and the 1990s. A Global Positioning System (GPS) survey of a geodetic network was used to determine the location, extent, and magnitude of vertical land-surface changes in Lucerne Valley in the Morongo ground-water basin. The GPS survey was conducted in 1998 to estimate historical elevation changes by comparing GPS-derived elevations with historical elevations (which were available for some of the monuments in the network as early as 1944) and to establish baseline values that can be used for comparisons with future GPS surveys. The GPS measurements indicated that about 600 millimeters (2 feet) [plus or minus 1,500 millimeters (5 feet)] of subsidence occurred at three of the monuments between 1969 and 1998 but that very little to no vertical change in position occurred at seven other monuments in the network. Water levels in the area of subsidence in Lucerne Valley declined about 15 meters (50 feet) during 1970-98. Interferometric synthetic aperture radar (InSAR) methods were used to characterize vertical land-surface changes in the Mojave River and Morongo ground-water basins during various intervals of time between 1992 and 1999. Interferograms, InSAR-generated displacement maps, show that subsidence ranging from 45 to 90 mm (0.15 to 0.3 ft) occurred in four areas of these two ground-water basins--the El Mirage, Lockhart-Harper Lake (dry), Newberry Springs, and Lucerne Valley areas. Some of the InSAR measurements were affected by the earthquakes at Landers and Hector Mine, California, and by atmospheric artifacts. Water-level data were examined for areas undergoing vertical land-surface changes to determine whether the vertical land-surface changes may be related to aquifer-system compaction caused by ground-water-level changes. Temporally relevant water-level data were sparse for some areas, particularly the El Mirage and Lockhart-Harper Lake (dry) areas. Water levels in wells proximate to the subsiding areas generally declined between 1992 and 1999; water levels in some wells proximate to the subsiding areas experienced seasonal periods of declines and recoveries.

Sneed, Michelle; Ikehara, Marti E.; Stork, Sylvia V.; Amelung, Falk; Galloway, Devin L.

2003-01-01

305

Investigation of land subsidence in the Houston-Galveston region of Texas by using the Global Positioning System and interferometric synthetic aperture radar, 1993-2000  

USGS Publications Warehouse

Since the early 1900s, groundwater has been the primary source of municipal, industrial, and agricultural water supplies for the Houston-Galveston region, Texas. The region's combination of hydrogeology and nearly century-long use of groundwater has resulted in one of the largest areas of subsidence in the United States; by 1979, as much as 3 meters (m) of subsidence had occurred, and approximately 8,300 square kilometers of land had subsided more than 0.3 m. The U.S. Geological Survey, in cooperation with the Harris-Galveston Subsidence District, used interferometric synthetic aperture radar (InSAR) data obtained for four overlapping scenes from European remote sensing satellites ERS-1 and ERS-2 to analyze land subsidence in the Houston-Galveston region of Texas. The InSAR data were processed into 27 interferograms that delineate and quantify land-subsidence patterns and magnitudes. Contemporaneous data from the Global Positioning System (GPS) were reprocessed by the National Geodetic Survey and analyzed to support, verify, and provide temporal resolution to the InSAR investigation. The interferograms show that the area of historical subsidence in downtown Houston along the Houston Ship Channel has stabilized and that recent subsidence occurs farther west and north of Galveston Bay. Three areas of recent subsidence were delineated along a broad arcuate (bowshaped) feature from Spring, Tex., southwest to Cypress, Tex., and south to Sugar Land, Tex., with subsidence rates ranging from 15 millimeters per year (mm/yr) to greater than 60 mm/yr. Multiyear interferograms near Seabrook, Tex., within the historical subsidence area and nearby Galveston Bay, show several fringes of subsidence (approximately 85 millimeters from January 1996 to December 1997) in the area; however it is difficult to determine the subsidence magnitude near Seabrook because many of the InSAR fringes were truncated or ill-defined. Horizontal and vertical GPS data throughout the area support the InSAR measured subsidence rates and extent. The subsidence rates for a few GPS stations northwest of Houston began to decrease in 2007, which may indicate that subsidence may be decreasing in these areas.

Bawden, Gerald W.; Johnson, Michaela R.; Kasmarek, Mark C.; Brandt, Justin; Middleton, Clifton S.

2012-01-01

306

Analysis of the fractal dimension of volcano geomorphology through Synthetic Aperture Radar (SAR) amplitude images acquired in C and X band.  

NASA Astrophysics Data System (ADS)

In the last two decades several aspects relevant to volcanic activity have been analyzed in terms of fractal parameters that effectively describe natural objects geometry. More specifically, these researches have been aimed at the identification of (1) the power laws that governed the magma fragmentation processes, (2) the energy of explosive eruptions, and (3) the distribution of the associated earthquakes. In this paper, the study of volcano morphology via satellite images is dealt with; in particular, we use the complete forward model developed by some of the authors (Di Martino et al., 2012) that links the stochastic characterization of amplitude Synthetic Aperture Radar (SAR) images to the fractal dimension of the imaged surfaces, modelled via fractional Brownian motion (fBm) processes. Based on the inversion of such a model, a SAR image post-processing has been implemented (Di Martino et al., 2010), that allows retrieving the fractal dimension of the observed surfaces, dictating the distribution of the roughness over different spatial scales. The fractal dimension of volcanic structures has been related to the specific nature of materials and to the effects of active geodynamic processes. Hence, the possibility to estimate the fractal dimension from a single amplitude-only SAR image is of fundamental importance for the characterization of volcano structures and, moreover, can be very helpful for monitoring and crisis management activities in case of eruptions and other similar natural hazards. The implemented SAR image processing performs the extraction of the point-by-point fractal dimension of the scene observed by the sensor, providing - as an output product - the map of the fractal dimension of the area of interest. In this work, such an analysis is performed on Cosmo-SkyMed, ERS-1/2 and ENVISAT images relevant to active stratovolcanoes in different geodynamic contexts, such as Mt. Somma-Vesuvio, Mt. Etna, Vulcano and Stromboli in Southern Italy, Shinmoe in Japan, Merapi in Indonesia. Preliminary results reveal that the fractal dimension of natural areas, being related only to the roughness of the observed surface, is very stable as the radar illumination geometry, the resolution and the wavelength change, thus holding a very unique property in SAR data inversion. Such a behavior is not verified in case of non-natural objects. As a matter of fact, when the fractal estimation is performed in the presence of either man-made objects or SAR image features depending on geometrical distortions due to the SAR system acquisition (i.e. layover, shadowing), fractal dimension (D) values outside the range of fractality of natural surfaces (2 < D < 3) are retrieved. These non-fractal characteristics show to be heavily dependent on sensor acquisition parameters (e.g. view angle, resolution). In this work, the behaviour of the maps generated starting from the C- and X- band SAR data, relevant to all the considered volcanoes, is analyzed: the distribution of the obtained fractal dimension values is investigated on different zones of the maps. In particular, it is verified that the fore-slope and back-slope areas of the image share a very similar fractal dimension distribution that is placed around the mean value of D=2.3. We conclude that, in this context, the fractal dimension could be considered as a signature of the identification of the volcano growth as a natural process. The COSMO-SkyMed data used in this study have been processed at IREA-CNR within the SAR4Volcanoes project under Italian Space Agency agreement n. I/034/11/0.

Pepe, S.; Di Martino, G.; Iodice, A.; Manzo, M.; Pepe, A.; Riccio, D.; Ruello, G.; Sansosti, E.; Tizzani, P.; Zinno, I.

2012-04-01

307

Radar Detection using Sparsely Distributed Apertures in Urban Environment  

E-print Network

Radar Detection using Sparsely Distributed Apertures in Urban Environment Il-Young Sona, Trond in detection performance compared to conventional matched filtering. Keywords: Radar detection, Distributed antenna, Radar data processing, Statistical signal pro- cessing 1. INTRODUCTION Conventional matched

Yazici, Birsen

308

Generalized radar/radiometry imaging problems  

E-print Network

Paper Generalized radar/radiometry imaging problems Ivan Prudyus, Sviatoslav Voloshynovskiy, Andriy- ing simulation based on radar, synthetic aperture radar (SAR) and radiometry systems are presented systems, synthetic aperture radar, spatio-temporal imaging. 1. Introduction Resolution of radar

Genève, Université de

309

Detection and Measurement of Land Subsidence Using Global Positioning System and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 1998-2000  

USGS Publications Warehouse

Land subsidence associated with ground-water-level declines has been recognized as a potential problem in Coachella Valley, California. Since the early 1920s, ground water has been a major source of agricultural, municipal, and domestic supply in the valley. Pumping of ground water resulted in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the lower Coachella Valley began, resulting in a reduction in ground-water pumping and a recovery of water levels during the 1950s through the 1970s. Since the late 1970s, demand for water in the valley has exceeded deliveries of imported surface water, resulting in increased pumping and associated ground-water-level declines and, consequently, an increase in the potential for land subsidence caused by aquifer-system compaction. The location, extent, and magnitude of the vertical land-surface changes in Coachella Valley between 1998 and 2000 were determined using Global Positioning System (GPS) and interferometric synthetic aperture radar (InSAR) methods. GPS measurements made at 15 geodetic monuments in the lower Coachella Valley indicate that -34 to +60 millimeters ? 45 millimeters (-0.11 to +0.20 foot ? 0.15 foot) of vertical change in the land surface occurred during the 2-year period. Changes at three of the monuments exceeded the maximum uncertainty of ? 45 millimeters (? 0.15 foot) at the 95-percent confidence level, which indicates that small amounts of uplift occurred at these monuments between October 1998 and August 2000. Water-level measurements made at wells near the three uplifted monuments during this 2-year period indicate that the water levels fluctuate seasonally; water-level measurements made at these wells in September 1998 and September 2000 indicate that the water levels rose slightly near two monuments and declined slightly near the third. The relation between the seasonally fluctuating, but fairly stable, water levels between September 1998 and September 2000 and the slight uplift at the monuments may indicate that the water levels are fluctuating in the elastic range of stress and that the preconsolidation stress of the aquifer system was not exceeded during the 2-year period. Results of the InSAR measurements made between June 17, 1998, and October 4, 2000, indicate that land subsidence, ranging from about 40 to 80 millimeters (0.13 to 0.26 foot), occurred in three areas of the Coachella Valley; near Palm Desert, Indian Wells, and La Quinta. Measurements made between June 17, 1998, and June 2, 1999, indicate that about 15 millimeters (0.05 foot) occurred southeast of Lake Cahuilla. All the subsiding areas coincide with or are near areas where ground-water levels declined between 1998 and 2000; some water levels in 2000 were at the lowest levels in their recorded histories. The coincident areas of subsidence and declining water levels suggest that aquifer-system compaction may be causing subsidence. If the stresses imposed by the historically lowest water levels exceeded the preconsolidation stress, the aquifer-system compaction and associated land subsidence may be permanent. Although the localized character of the subsidence signals look typical of the type of subsidence characteristically caused by localized pumping, the subsidence also may be related to tectonic activity in the valley.

Sneed, Michelle; Stork, Sylvia V.; Ikehara, Marti E.

2002-01-01

310

Natural and Unnatural Oil Layers on the Surface of the Gulf of Mexico Detected and Quantified in Synthetic Aperture RADAR Images with Texture Classifying Neural Network Algorithms  

NASA Astrophysics Data System (ADS)

Effervescent hydrocarbons rise naturally from hydrocarbon seeps in the Gulf of Mexico and reach the ocean surface. This oil forms thin (~0.1 ?m) layers that enhance specular reflectivity and have been widely used to quantify the abundance and distribution of natural seeps using synthetic aperture radar (SAR). An analogous process occurred at a vastly greater scale for oil and gas discharged from BP's Macondo well blowout. SAR data allow direct comparison of the areas of the ocean surface covered by oil from natural sources and the discharge. We used a texture classifying neural network algorithm to quantify the areas of naturally occurring oil-covered water in 176 SAR image collections from the Gulf of Mexico obtained between May 1997 and November 2007, prior to the blowout. Separately we also analyzed 36 SAR images collections obtained between 26 April and 30 July, 2010 while the discharged oil was visible in the Gulf of Mexico. For the naturally occurring oil, we removed pollution events and transient oceanographic effects by including only the reflectance anomalies that that recurred in the same locality over multiple images. We measured the area of oil layers in a grid of 10x10 km cells covering the entire Gulf of Mexico. Floating oil layers were observed in only a fraction of the total Gulf area amounting to 1.22x10^5 km^2. In a bootstrap sample of 2000 replications, the combined average area of these layers was 7.80x10^2 km^2 (sd 86.03). For a regional comparison, we divided the Gulf of Mexico into four quadrates along 90° W longitude, and 25° N latitude. The NE quadrate, where the BP discharge occurred, received on average 7.0% of the total natural seepage in the Gulf of Mexico (5.24 x10^2 km^2, sd 21.99); the NW quadrate received on average 68.0% of this total (5.30 x10^2 km^2, sd 69.67). The BP blowout occurred in the NE quadrate of the Gulf of Mexico; discharged oil that reached the surface drifted over a large area north of 25° N. Performing a similar estimate using 5x5 km grid cells, we observed discharged oil over an area of 1.20x10^5 km^2; 91% of this area was east of 90° W. The average area oil covered water observed in the SAR images was 4.41x104^ km^2, 98% of which was observed in the eastern Gulf. Numerical oil spill model experiments are used to clarify the distinction between the area impacted by the BP oil spill and the surface slicks due to known natural seeps. Natural oil seepage has been cited as a background source of hydrocarbon contamination in the Gulf of Mexico. Our direct comparison shows that during the blowout, the discharged oil impacted an average area two orders of magnitude greater than the entire Gulf total and three orders of magnitude greater than the usual dose received in the northeastern region. Because the layers of discharged oil were often many times thicker than natural seep oil, additional scale factors are required to show the true difference in doses. These differences should be weighed when evaluating the relative impact of natural and unnatural oil in a large marine ecosystem.

MacDonald, I. R.; Garcia-Pineda, O. G.; Morey, S. L.; Huffer, F.

2011-12-01

311

GNSS-based passive radar sensing using hybrid-aperture system  

NASA Astrophysics Data System (ADS)

A hybrid-aperture radar system is being developed for passive, GNSS-based sensing and imaging missions. Different from previous work, the real aperture (RA) array has excellent cross-range resolution and electronic scanning capability, and synthetic aperture processing is applied for the dimension along the UAV/aircraft flight path. The hybrid aperture thus provides real-time, combined sensing capability and multiple functions. Multi-level signal synchronization and tracking is used to ensure the signal phase coherency and integrity. The advantages of covert radar sensing and reduced onboard computing complexity of this sensor are being demonstrated through experiments.

Silver, Randy; Zhang, Yan Rockee; Suarez, Hernan; Pan, Yu; Huang, Yih-Ru

2013-05-01

312

Synthetic-Aperture Coherent Imaging From A Circular Path  

NASA Technical Reports Server (NTRS)

Imaging algorithms based on exact point-target responses. Developed for use in reconstructing image of target from data gathered by radar, sonar, or other transmitting/receiving coherent-signal sensory apparatus following circular observation path around target. Potential applications include: Wide-beam synthetic-aperture radar (SAR) from aboard spacecraft in circular orbit around target planet; SAR from aboard airplane flying circular course at constant elevation around central ground point, toward which spotlight radar beam pointed; Ultrasonic reflection tomography in medical setting, using one transducer moving in circle around patient or else multiple transducers at fixed positions on circle around patient; and Sonar imaging of sea floor to high resolution, without need for large sensory apparatus.

Jin, Michael Y.

1995-01-01

313

Detection and measurement of land subsidence using Global Positioning System and interferometric synthetic aperture radar, Coachella Valley, California, 1996-98  

USGS Publications Warehouse

Land subsidence associated with ground-water-level declines has been recognized as a potential problem in Coachella Valley, California. Since the early 1920s, ground water has been a major source of agricultural, municipal, and domestic supply in the valley, resulting in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the lower Coachella Valley began, resulting in a reduction in ground-water pumping and a recovery of water levels from the 1950s through the 1970s. Since the late 1970s, the demand for water in the valley has exceeded the deliveries of imported surface water, again resulting in increased pumping and ground-water-level declines. The magnitude and temporal occurrence of land subsidence in the lower Coachella Valley are not well known; data are sparse and accuracy varies. Also, the area is tectonically active and has subsided during the past several million years, which further complicates interpretations of the data. Land-surface-elevation data have been collected by many agencies using various methods and different geographic scales; because of this, the -150 millimeters (-0.5 foot) of subsidence determined for the southern parts of the valley for 1930-96 may have a possible error of plus or minus (?)90 millimeters (?0.3 foot). The location, extent, and magnitude of vertical land-surface changes from 1996 to 1998 were determined using Global Positioning System (GPS) and interferometric synthetic aperture radar (InSAR) methods. GPS measurements for 14 monuments in the lower Coachella Valley indicate that the vertical land-surface changes from 1996 to 1998 ranged from -13 to -67 millimeters ? 40 millimeters (-0.04 to -0.22 foot ?0.13 foot). Changes at seven of the monuments exceeded the measurement error of ?40 millimeters (?0.13 foot), which indicates that small amounts of land subsidence occurred at these monuments between 1996 and 1998. Some of the water levels measured in wells near several of these monuments during 1996-98 were the lowest water levels in the recorded histories of the wells. The possible relation between the stresses caused by historically low water levels and the measured vertical changes in land surface suggests that the preconsolidation stress of the aquifer system may have been exceeded during this period and that subsidence may be permanent. Comparisons of several paired monuments and wells indicated that the relation between short-term ground-water-level changes and vertical changes in land surface in the lower Coachella Valley is not clearly defined. Results of InSAR measurements made between 1996 and 1998 indicate that vertical changes in land surface, ranging from about -20 to -70 millimeters ? 5-10 millimeters (-0.07 to -0.23 foot ? 0.02-0.03 foot), occurred in three areas of the Coachella Valley--near Palm Desert, Indian Wells, and Lake Cahuilla. The areas of subsidence near Palm Desert and Indian Wells coincide with areas of substantial ground-water production during 1996-98. The Coachella Valley Water District reported that they had no ground-water production wells in the Lake Cahuilla area but that there may be private production wells in the area. Production from these wells or possibly tectonic activity may be contributing to or causing the subsidence. The geodetic network used for the GPS measurements described in this report covers the area from the Salton Sea on the south to just northwest of Indio. The maps processed using InSAR overlap the part of the geodetic network west of Coachella and north of Lake Cahuilla, and include the Palm Desert area. Both methods of measuring vertical land-surface changes, GPS and InSAR, were used to characterize vertical land-surface changes from the Palm Desert area to the Salton Sea. Because InSAR produces more spatially detailed data over large areas, it generally was useful where vertical land-surface changes were previously unrecognized, such as the

Sneed, Michelle; Ikehara, Marti E.; Galloway, D.L.; Amelung, Falk

2001-01-01

314

Detection and Measurement of Land Subsidence Using Global Positioning System Surveying and Interferometric Synthetic Aperture Radar, Coachella Valley, California, 1996-2005  

USGS Publications Warehouse

Land subsidence associated with ground-water-level declines has been investigated by the U.S. Geological Survey in the Coachella Valley, California, since 1996. Ground water has been a major source of agricultural, municipal, and domestic supply in the valley since the early 1920s. Pumping of ground water resulted in water-level declines as large as 15 meters (50 feet) through the late 1940s. In 1949, the importation of Colorado River water to the southern Coachella Valley began, resulting in a reduction in ground-water pumping and a recovery of water levels during the 1950s through the 1970s. Since the late 1970s, demand for water in the valley has exceeded deliveries of imported surface water, resulting in increased pumping and associated ground-water-level declines and, consequently, an increase in the potential for land subsidence caused by aquifer-system compaction. Global Positioning System (GPS) surveying and interferometric synthetic aperture radar (InSAR) methods were used to determine the location, extent, and magnitude of the vertical land-surface changes in the southern Coachella Valley. GPS measurements made at 13 geodetic monuments in 1996 and in 2005 in the southern Coachella Valley indicate that the elevation of the land surface had a net decline of 333 to 22 millimeters ?58 millimeters (1.1 to 0.07 foot ?0.19 foot) during the 9-year period. Changes at 10 of the 13 monuments exceeded the maximum uncertainty of ?58 millimeters (?0.19 foot) at the 95-percent confidence level, indicating that subsidence occurred at these monuments between June 1996 and August 2005. GPS measurements made at 20 geodetic monuments in 2000 and in 2005 indicate that the elevation of the land surface changed -312 to +25 millimeters ?42 millimeters (-1.0 to +0.08 foot ?0.14 foot) during the 5-year period. Changes at 14 of the 20 monuments exceeded the maximum uncertainty of ?42 millimeters (?0.14 foot) at the 95-percent confidence level, indicating that subsidence occurred at these monuments between August 2000 and August 2005. Eight of the fourteen monuments for which subsidence rates could be compared indicate that subsidence rates increased by as much as a factor of 10 between 2000 and 2005 compared with subsidence rates before 2000. InSAR measurements made between May 7, 2003, and September 25, 2005, indicate that land subsidence, ranging from about 75 to 180 millimeters (0.25 to 0.59 foot), occurred in three areas of the Coachella Valley: near Palm Desert, Indian Wells, and La Quinta; the equivalent subsidence rates range from about 3 to more than 6 mm/month (0.01 to 0.02 ft/month). The subsiding areas near Palm Desert, Indian Wells, and La Quinta were previously identified using InSAR measurements for 1996-2000, which indicated that about 35 to 150 mm (0.11 to 0.49 ft) of subsidence occurred during the four-year period; the equivalent subsidence rates range from about 1 to 3 mm/month (0.003 to 0.01 ft/month). Comparison of the InSAR results indicates that subsidence rates have increased 2 to 4 times since 2000 in these three areas. Water-level measurements made at wells near the subsiding monuments and in the three subsiding areas generally indicated that the water levels fluctuated seasonally and declined annually between 1996 and 2005; some water levels in 2005 were at the lowest levels in their recorded histories. The coincident areas of subsidence and declining water levels suggest that aquifer-system compaction may be causing subsidence. If the stresses imposed by the historically lowest water levels exceeded the preconsolidation stress, the aquifer-system compaction and associated land subsidence may be permanent. Although the localized character of the subsidence signals is typical of the type of subsidence characteristically caused by localized ground-water pumping, the subsidence may also be related to tectonic activity in the valley.

Sneed, Michelle; Brandt, Justin T.

2007-01-01

315

Real-time interferometric synthetic aperture microscopy  

E-print Network

) system design with real-time 2D cross-sectional processing is described in detail. The system can acquireReal-time interferometric synthetic aperture microscopy Tyler S. Ralston1,2,* , Daniel L. Marks1 indistinguishable scattering intensities and provides proof of feasibility for future real-time ISAM systems. ©2008

Bhargava, Rohit

316

Infrared, adaptive, and synthetic aperture optical systems  

Microsoft Academic Search

This book contains 24 selections. Some of the titles are: Generating, grinding, and figuring advanced optical elements; Survey of material for an infrared-opaque coating; Parametric study of various synthetic aperture telescope configurations for coherent imaging applications; and Zone plates for optical sensor applications.

R. B. Johnson; W. L. Wolfe; J. S. Fender

1986-01-01

317

High-resolution DOA estimation from synthetic aperture beamforming  

Microsoft Academic Search

We have introduced a new direction of arrival algorithm that synthetically extends the spatial aperture (synthetic aperture conventional beamformer, SA-CBF) that couples the resolution capability of the MUSIC algorithm and the robustness of the conventional Bartlett beamformer. The synthetic aperture is created bv using a 2D data extrapolation technique from 2D linear prediction algorithm whose number of parameters were selected

Claudio S. Marino; P. M. Chau

2005-01-01

318

Interferometric Synthetic Aperture Microscopy: Computed Imaging for Scanned Coherent Microscopy  

PubMed Central

Three-dimensional image formation in microscopy is greatly enhanced by the use of computed imaging techniques. In particular, Interferometric Synthetic Aperture Microscopy (ISAM) allows the removal of out-of-focus blur in broadband, coherent microscopy. Earlier methods, such as optical coherence tomography (OCT), utilize interferometric ranging, but do not apply computed imaging methods and therefore must scan the focal depth to acquire extended volumetric images. ISAM removes the need to scan the focus by allowing volumetric image reconstruction from data collected at a single focal depth. ISAM signal processing techniques are similar to the Fourier migration methods of seismology and the Fourier reconstruction methods of Synthetic Aperture Radar (SAR). In this article ISAM is described and the close ties between ISAM and SAR are explored. ISAM and a simple strip-map SAR system are placed in a common mathematical framework and compared to OCT and radar respectively. This article is intended to serve as a review of ISAM, and will be especially useful to readers with a background in SAR. PMID:20948975

Davis, Brynmor. J.; Marks, Daniel. L.; Ralston, Tyler. S.; Carney, P. Scott; Boppart, Stephen. A.

2008-01-01

319

Fast parametric beamformer for synthetic aperture imaging.  

PubMed

This paper describes the design and implementation of a real-time delay-and-sum synthetic aperture beamformer. The beamforming delays and apodization coefficients are described parametrically. The image is viewed as a set of independent lines that are defined in 3D by their origin, direction, and inter-sample distance. The delay calculation is recursive and inspired by the coordinate rotation digital computer (CORDIC) algorithm. Only 3 parameters per channel and line are needed for their generation. The calculation of apodization coefficients is based on a piece- wise linear approximation. The implementation of the beamformer is optimized with respect to the architecture of a novel synthetic aperture real-time ultrasound scanner (SARUS), in which 4 channels are processed by the same set of field-programmable gate arrays (FPGA). In synthetic transmit aperture imaging, low-resolution images are formed after every emission. Summing all low-resolution images produces a perfectly focused high-resolution image. The design of the beamformer is modular, and a single beamformation unit can produce 4600 low-resolution images per second, each consisting of 32 lines and 1024 complex samples per line. In its present incarnation, 3 such modules fit in a single device. The summation of low-resolution images is performed internally in the FPGA to reduce the required bandwidth. The delays are calculated with a precision of 1/16th of a sample, and the apodization coefficients with 7-bit precision. The accumulation of low-resolution images is performed with 24-bit precision. The level of the side- and grating lobes, introduced by the use of integer numbers in the calculations and truncation of intermediate results, is below -86 dB from the peak. PMID:18986919

Nikolov, Svetoslav Ivanov; Jensen, Jørgen Arendt; Tomov, Borislav Gueorguiev

2008-08-01

320

Constraining the slip distribution and fault geometry of the Mw 7.9, 3 November 2002, Denali fault earthquake with Interferometric Synthetic Aperture Radar and Global Positioning System data  

USGS Publications Warehouse

The Mw 7.9, Denali fault earthquake (DFE) is the largest continental strike-slip earthquake to occur since the development of Interferometric Synthetic Aperture Radar (InSAR). We use five interferograms, constructed using radar images from the Canadian Radarsat-1 satellite, to map the surface deformation at the western end of the fault rupture. Additional geodetic data are provided by displacements observed at 40 campaign and continuous Global Positioning System (GPS) sites. We use the data to determine the geometry of the Susitna Glacier fault, thrusting on which initiated the DFE, and to determine a slip model for the entire event that is consistent with both the InSAR and GPS data. We find there was an average of 7.3 ?? 0.4 m slip on the Susitna Glacier fault, between 1 and 9.5 km depth on a 29 km long fault that dips north at 41 ?? 0.7?? and has a surface projection close to the mapped rupture. On the Denali fault, a simple model with large slip patches finds a maximum of 8.7 ?? 0.7 m of slip between the surface and 14.3 ?? 0.2 km depth. A more complex distributed slip model finds a peak of 12.5 ?? 0.8 m in the upper 4 km, significantly higher than the observed surface slip. We estimate a geodetic moment of 670 ?? 10 ?? 10 18 N m (Mw 7.9), consistent with seismic estimates. Lack of preseismic data resulted in an absence of InSAR coverage for the eastern half of the DFE rupture. A dedicated geodetic InSAR mission could obviate coverage problems in the future.

Wright, T.J.; Lu, Z.; Wicks, C.

2004-01-01

321

(abstract) Characterization of Tree Water Status and Dielectric Constant Changes of North American Boreal Forests in Combination with Synthetic Aperture Radar Remote Sensing  

NASA Technical Reports Server (NTRS)

The occurrence and magnitude of temporal and spatial tree water status changes in the boreal environment were studied in a floodplain forest in Alaska and in four forest types of Central Canada. Under limited water supply conditions from the rooted soil zone in early spring (freeze/thaw transition) and during summer, trees show declining water potentials. Coincidental change in tree water potential, tree transpiration and tree dielectric constant had been observed in previous studies performed in Mediterranean ecotones. If radar is sensitive to chances in tree water status as reflected through changes in dielectric constant, then radar remote sensing could be used to monitor the water status of forests. The SAR imagery is examined to determine the response of the radar backscatter to the ground based observations of the water status of forest canopies. Comparisons are made between stands and also along the large North-South gradient between sites. Data from SAR are used to examine the radar response to canopy physiological state as related to vegetation freeze/thaw and growing season length.

McDonald, K. C.; Zimmerman, R.; Way, J. B.

1994-01-01

322

Three-dimensional imaging using differential synthetic aperture interferometry  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar interferometry (InSAR) can gain three-dimensional topography with high spatial resolution and height accuracy using across track interferometry[1]. Conventional InSAR produce three-dimensional images from SAR data. But when the working wavelength transit from microwave to optical wave, the transmission antenna and receive antenna become very sensitive to platform vibration and beam quality[2]. Through differential receive antenna formation, we can relax the requirement of platform and laser using synthetic aperture imaging ladar (SAIL) concept[3]. Line-of-sight motion constraints are reduced by several orders of magnitude. We introduce two distinctive forms of antenna formation according to the position of interferogram. The first architecture can simplify the interferogram processing and phase extraction algorithm under time-division multiplex operation. The second architecture can process the 2D coordinate and height coordinate at the same time. Using optical diffraction theory, a systematic theory of side-looking SAIL is mathematically formulated and the necessary conditions for assuring a correct phase history are established[4]. Based on optical transformation and regulation of wavefront, a side-looking SAIL of two distinctive architectures is invented and the basic principle, systematic theory, design equations and necessary conditions are presented. It is shown that high height accuracy can be reached and the influences from atmospheric turbulence and unmodeled line-of-sight motion can be automatically compensated.

Zhang, Ning; Zhou, Yu; Sun, Jianfeng; Zhi, Ya'nan; Lu, Zhiyong; Xu, Qian; Sun, Zhiwei; Liu, Liren

2014-09-01

323

Automated change detection for synthetic aperture sonar  

NASA Astrophysics Data System (ADS)

In this paper, an automated change detection technique is presented that compares new and historical seafloor images created with sidescan synthetic aperture sonar (SAS) for changes occurring over time. The method consists of a four stage process: a coarse navigational alignment; fine-scale co-registration using the scale invariant feature transform (SIFT) algorithm to match features between overlapping images; sub-pixel co-registration to improves phase coherence; and finally, change detection utilizing canonical correlation analysis (CCA). The method was tested using data collected with a high-frequency SAS in a sandy shallow-water environment. By using precise co-registration tools and change detection algorithms, it is shown that the coherent nature of the SAS data can be exploited and utilized in this environment over time scales ranging from hours through several days.

G-Michael, Tesfaye; Marchand, Bradley; Tucker, J. D.; Sternlicht, Daniel D.; Marston, Timothy M.; Azimi-Sadjadi, Mahmood R.

2014-05-01

324

SEA SURFACE SIMULATOR FOR TESTING A SYNTHETIC APERTURE SONAR  

E-print Network

SEA SURFACE SIMULATOR FOR TESTING A SYNTHETIC APERTURE SONAR B. DAVIS University of Arizona, Tucson. HUNT University of Arizona, Tucson, AZ With the move to use side-looking imaging sonars in very shallow waters as a com- ponent part of MCM operations, synthetic aperture sonars (SAS) appear to have some

325

Discrimination of coastal wetland environments in the Amazon region based on multi-polarized L-band airborne Synthetic Aperture Radar imagery  

NASA Astrophysics Data System (ADS)

This study assessed the use of multi-polarized L-band images for the identification of coastal wetland environments in the Amazon coast region of northern Brazil. Data were acquired with a SAR R99B sensor from the Amazon Surveillance System (SIVAM) on board a Brazilian Air Force jet. Flights took place in the framework of the 2005 MAPSAR simulation campaign, a German-Brazilian feasibility study focusing on a L-band SAR satellite. Information retrieval was based on the recognition of the interaction between a radar signal and shallow-water morphology in intertidal areas, coastal dunes, mangroves, marshes and the coastal plateau. Regarding the performance of polarizations, VV was superior for recognizing intertidal area morphology under low spring tide conditions; HH for mapping coastal environments covered with forest and scrub vegetation such as mangrove and vegetated dunes, and HV was suitable for distinguishing transition zones between mangroves and coastal plateau. The statistical results for the classification maps expressed by kappa index and general accuracy were 83.3% and 0.734 for the multi-polarized color composition (R-HH, G-HV, B-VV), 80.7% and 0.694% for HH, 79.7% and 0.673% for VV, and 77.9% and 0.645% for HV amplitude image. The results indicate that use of multi-polarized L-band SAR is a valuable source of information aiming at the identification and discrimination of distinct geomorphic targets in tropical wetlands.

Souza-Filho, Pedro Walfir M.; Paradella, Waldir R.; Rodrigues, Suzan W. P.; Costa, Francisco R.; Mura, José C.; Gonçalves, Fabrício D.

2011-11-01

326

Use of Synthetic Aperture Radar (SAR) to Identify and Characterize Overwintering Areas of Fish in Ice-Covered Arctic RIvers: A Demonstration with Broad Whitefish and their Habitats in the Sagavanirktok River, Alaska  

SciTech Connect

In northern climates, locating overwintering fish can be very challenging due to thick ice cover. Areas near the coast of the Beaufort Sea provide valuable overwintering habitat for both resident and anadromous fish species; identifying and understanding their use of overwintering areas is of special interest. Synthetic aperture radar (SAR) imagery from two spaceborne satellites was examined as an alternative to radiotelemetry for identifying anadromous fish overwintering. The presence of water and ice were sampled at 162 sites and fish were sampled at 16 of these sites. From SAR imagery alone, we successfully identified large pools inhabited by overwintering fish in the ice-covered Sagavanirktok River. In addition, the imagery was able to identify all of the larger pools (mean minimum length of 138m (range 15-470 m; SD=131)) of water located by field sampling. The effectiveness of SAR to identify these pools varied from 31% to 100%, depending on imagery polarization, the incidence angle range, and the orbit. Horizontal transmit–vertical receive (HV) polarization appeared best. The accuracy of SAR was also assessed at a finer pixel-by-pixel (30-m x30-m) scale. The best correspondence at this finer scale was obtained with an image having HV polarization. The levels of agreement ranged from 54% to 69%. The presence of broad whitefish (the only anadromous species present) was associated with salinity and pool size (estimated with SAR imagery); fish were more likely to be found in larger pools with low salinity. This research illustrates that SAR imaging has great potential for identifying under-ice overwintering areas of riverine fish. These techniques should allow managers to identify critical overwintering areas with relatively more ease and lower cost than traditional techniques.

Brown, Richard S.; Duguay, Claude R.; Mueller, Robert P.; Moulton, Larry; Doucette, Peter J.; Tagestad, Jerry D.

2010-12-01

327

Spatiotemporal evolution of surface creep in the Parkfield region of the San Andreas Fault (1993-2004) from Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

The Parkfield segment is located on the San Andreas Fault (SAF) at the boundary between the creeping segment to the northwest, which slips steadily at a rate of 25-30 mm/y and the locked segment to the southeast, which last ruptured in the 1857 Mw 7.9 Fort Tejon earthquake. At least 6 historic earthquakes of Mw 6 have occurred in this area, in 1881, 1901, 1922, 1934, 1966 and 2004. The Parkfield segment is also characterized by a complex frictional fault behaviour as it represents a transition zone from aseismic creep to stick-slip regime. Creep decreases from a rate of 28 mm/yr in the central creeping segment to 0 mm/yr in the Cholame segment. On the Parkfield transition segment, surface creepmeters and alignment arrays indicate that shallow slip occurs via episodic creep events of mm-to-cm magnitude, as well as intervening steady slip. Slow slip transients of varying duration and magnitude are also well documented. Nadeau and McEvilly (1999) show slip accelerations around the Parkfield asperity from observations of repeating identical earthquake sequences initiating in 1992, confirmed by 2-color EDM measurements. During the last 2004 Parkfield earthquake (Mw 6.0), about 70% of the total (coseismic and postseismic) moment release occurred aseismically. Therefore, it is of particular interest to measure and analyse not only the spatial evolution of surface displacement in this area but also its evolution with time. This paper focusses on the interseismic period before the 28 September 2004 Parkfield event in the Parkfield area. We use radar data acquired by the European Space Agency’s European Remote Sensing (ERS1-2) satellites to form descending interferograms that we combine to retrieve time series of surface displacement in the period 1993-2004. In particular, we focus on characterising the space and time evolution of surface creep on the Parkfield and Cholame segments. The spatial pattern of the inter-seismic displacement rate indicates that tectonic strain is not uniformly distributed along strike of the fault over the period 1993-2004. We observe a decrease in the creep rate from the Parkfield segment to south of Cholame from 1.4 ±0.3 cm/yr to 0.6 ±0.3 cm/yr and a small but significant creep rate increase on the Cholame segment up to 0.2 ±0.1 cm/yr. The evidence of episodic creep on the Cholame segment of the SAFZ south of Parkfield is in contrast with previous published interpretations of GPS and trilateration data. Stone et al. (2002) and Young at al. (2002) studied the recent rupture history of the Cholame segment by trenching. They reported that although unlikely, they could not rule out the possibility of a post 1857 displacement. According to Young et al., (2002) post-1857 tectonic fracturing of historic sediments may have resulted from creep, triggered slip, or ground shaking from nearby moderate earthquakes. This segment of the SAF merits close monitoring as it has shown recent evidence of deep slow slip revealed by deep tremors (Shelly et al., 2009).

de Michele, M.; Raucoules, D.; Rolandone, F.; Briole, P.; Salichon, J.; Lemoine, A.; Aochi, H.

2010-12-01

328

Synthetic aperture design for increased SAR image rate  

DOEpatents

High resolution SAR images of a target scene at near video rates can be produced by using overlapped, but nevertheless, full-size synthetic apertures. The SAR images, which respectively correspond to the apertures, can be analyzed in sequence to permit detection of movement in the target scene.

Bielek, Timothy P. (Albuquerque, NM); Thompson, Douglas G. (Albuqerque, NM); Walker, Bruce C. (Albuquerque, NM)

2009-03-03

329

Ambiguities in spaceborne synthetic aperture radar systems  

NASA Technical Reports Server (NTRS)

An examination of aspects of spaceborne SAR time delay and Doppler ambiguities has led to the formulation of an accurate method for the evaluation of the ratio of ambiguity intensities to that of the signal, which has been applied to the nominal SAR system on Seasat. After discussing the variation of this ratio as a function of orbital latitude and attitude control error, it is shown that the detailed range migration-azimuth phase history of an ambiguity is different from that of a signal, so that the images of ambiguities are dispersed. Seasat SAR dispersed images are presented, and their dispersions are eliminated through an adjustment of the processing parameters. A method is also presented which uses a set of multiple pulse repetition sequences to determine the Doppler centroid frequency absolute values for SARs with high carrier frequencies and poor attitude measurements.

Li, F. K.; Johnson, W. T. K.

1983-01-01

330

Synthetic Aperture Radar Interferometry with 3 satellites  

E-print Network

Our study investigates interferometric SAR (InSAR) post-processing height retrieval techniques. We explore the possible improvements by adding a third satellite to the two already in orbit, and examine some potential uses ...

Wong, Wallace D. (Wallace Dazheng)

2005-01-01

331

Synthetic aperture radar correlator phase histories  

NASA Technical Reports Server (NTRS)

This report supplements the design of the following subsystems: (1) zoom azimuth telescope, zooming range from 3X to 6X. (2) range curvature correcting lenses. (3) Sphero-cylindrical shift lens. (4) Auxiliary lenses (tilted cylinder and matching lens).

1977-01-01

332

Sea slicks classification by synthetic aperture radar  

NASA Astrophysics Data System (ADS)

An automatic system called OSAD (Oil Spill Automatic Detector), able to discriminate oil spills (OS) from similar features (look-alikes - LA) in SAR images, was developed some years ago. Slick detection is based on a probabilistic method (tuned with a training dataset defined by an expert photointerpreter) evaluating radiometric and geometric characteristics of the areas of interest. OSAD also provides wind field by analyzing SAR images. With the aim to completely classify sea slicks, recently a new procedure has been added. Dark areas are identified on the image and the wind is computed inside and outside for every area: if outside wind value is less than a threshold of 2 m/s it is impossible to evaluate if damping is due to a slick. On the other hand, if outside wind is higher than the threshold and the difference between inside and outside the dark area is lower than 1 m/s we consider this reduction as wind fluctuation. Wind difference higher than 1 m/s is interpreted as damping effect due to a slick; therefore the remaining dark spots are split in OS and LA by OSAD. LA are then analyzed and separated in "biogenic" or "anthropogenic" slicks following an analogous procedure. The system performances has been tested on C-band SAR images, in particular on images having spatial resolution so high to examine details near the coastline; the obtained results confirm the efficiency of the algorithm in the classification of four types of signatures usually found on the sea surface.

Trivero, P.; Biamino, W.; Borasi, M.; Cavagnero, M.; Di Matteo, L.; Loreggia, D.

2014-10-01

333

Ocean research with synthetic aperture radar  

Microsoft Academic Search

Spaceborne SAR ocean imagery yields information on surface winds, ocean wavelengths and directions, current fronts and eddies and, at times, even coastal bathymetry. Attention is presently given to the principles of SAR two-dimensional image formation, and to the development history of spaceborne SAR devices and their uses before the launching of Seasat (1974-1978) and during Seasat operations (after autumn 1978),

R. C. Beal

1985-01-01

334

Space-Time-Waveform Adaptive Processing for Frequency Diverse Distributed Radar Apertures  

E-print Network

Space-Time-Waveform Adaptive Processing for Frequency Diverse Distributed Radar Apertures Raviraj S nature of frequency diverse distributed apertures. I. INTRODUCTION Surveillance radar systems operate of diversity to radar systems, using a distributed radar [2]. The phrase "waveform diversity" has now come

Adve, Raviraj

335

Polarimetric synthetic-aperture inversion for extended targets in clutter  

NASA Astrophysics Data System (ADS)

This paper presents an analytic inversion method for a polarimetric synthetic-aperture radar (SAR) in the case of an extended target embedded in clutter. The measurements are also contaminated by thermal noise. We use microlocal analysis in a statistical setting to develop a filtered-backprojection-type reconstruction method. The inversion method accommodates arbitrary waveforms and arbitrary flight paths. We model the antennas and scatterers as dipoles; scatterers are thus characterized by a spatially varying scattering matrix. We include directional scattering assumptions to distinguish a curve-like extended target from clutter, which is assumed to scatter isotropically. For the inversion we choose the backprojection filter which minimizes the mean-square error between the reconstructed image and the actual target scattering matrix. Our work differs from standard polarimetric SAR imaging in that we do not perform channel-by-channel image reconstruction. We find that it is preferable to use a coupled reconstruction scheme in which we use all sets of collected data to form each element of the scattering matrix. We show in our numerical experiments that the coupled reconstruction not only minimizes the mean-square error but also improves the image target-to-clutter ratio in certain scenarios.

Voccola, Kaitlyn; Cheney, Margaret; Yazici, Birsen

2013-05-01

336

Central obscuration effects on optical synthetic aperture imaging  

NASA Astrophysics Data System (ADS)

Due to the central obscuration problem exists in most optical synthetic aperture systems, it is necessary to analyze its effects on their image performance. Based on the incoherent diffraction limited imaging theory, a Golay-3 type synthetic aperture system was used to study the central obscuration effects on the point spread function (PSF) and the modulation transfer function (MTF). It was found that the central obscuration does not affect the width of the central peak of the PSF and the cutoff spatial frequency of the MTF, but attenuate the first sidelobe of the PSF and the midfrequency of the MTF. The imaging simulation of a Golay-3 type synthetic aperture system with central obscuration proved this conclusion. At last, a Wiener Filter restoration algorithm was used to restore the image of this system, the images were obviously better.

Wang, Xue-wen; Luo, Xiao; Zheng, Li-gong; Zhang, Xue-jun

2014-02-01

337

Space-Time-Waveform Adaptive Processing for Frequency Diverse Distributed Radar Apertures  

Microsoft Academic Search

This paper reviews recent developments in the field of adaptive processing for frequency diverse, distributed, radar apertures. The large baseline of such a distributed radar results in angular resolution that is orders of magnitude better than the resolution of a single large radar. This capability comes at the cost of grating lobes (multistatics with evenly spaced apertures) or high sidelobes

Raviraj S. Adve; Lorne Applebaum; Michael C. Wicks; Richard A. Schneible

2006-01-01

338

Concepts for synthetic aperture sonar performance prediction and mission planning  

Microsoft Academic Search

Synthetic aperture sonar (SAS) is an emerging technology capable of providing high resolution sea floor imaging. One remarkable property of SAS is that its azimuthal resolution is theoretically independent of range and wavelength. Consequently SAS is particularly well suited for classifying bottom mines at standoff ranges. SAS processing technology has matured sufficiently in the recent years that it is now

J. D. Campbell; E. Chang

2005-01-01

339

Synthetic aperture controlled source electromagnetics R. Snieder,1  

E-print Network

; accepted 7 June 2010; published 9 July 2010. [1] Controlled source electromagnetics (CSEM) has been used survey, a horizontal current dipole is used as the source to generate an electromagnetic fieldClick Here for Full Article Synthetic aperture controlled source electromagnetics Y. Fan,1 R

Snieder, Roel

340

SYNTHETIC APERTURE SONAR: A TOOL IN UNDERWATER ARCHAEOLOGY  

Microsoft Academic Search

The principle of synthetic aperture sonar (SAS) is coherent combination of successive pings such that the along-track resolution is improved. The along-track resolution in SAS images become range and frequency independent. SAS technology is efficient - it provides high resolution and large area coverage simultaneously. This makes SAS an ideal tool in search for small objects over large areas. The

Roy E Hansen; Helge S Telle

341

In-vivo synthetic aperture flow imaging in medical ultrasound  

Microsoft Academic Search

A new method for acquiring flow images using synthetic aperture techniques in medical ultrasound is presented. The new approach makes it possible to have a continuous acquisition of flow data throughout the whole image simultaneously, and this can significantly improve blood velocity estimation. Any type of filter can be used for discrimination between tissue and blood flow without initialization, and

Svetoslav Ivanov Nikolov; Jmgen Arendt Jensen

2003-01-01

342

Synthetic-aperture imaging through a dispersive layer  

Microsoft Academic Search

This paper develops a method for forming a synthetic-aperture image of a flat surface seen through a homogeneous layer of a material that is dispersive, i.e., its wave speed varies with frequency. We outline first a simplified scalar model for electromagnetic wave propagation in a dispersive medium; the resulting equation could also be used for acoustics. We show that the

Margaret Cheney; Clifford J. Nolan

2004-01-01

343

Synthetic aperture focusing techniques for ultrasonic imaging of solid objects.  

E-print Network

obtained from the ultrasonic inspection of test specimens with artificial defects (side drilled holes). 1Synthetic aperture focusing techniques for ultrasonic imaging of solid objects. Tadeusz Stepinski lenses used for focusing ultrasonic beams at a point of a solid object or structure. This paper presents

344

Elastic Shapes Models for Improving Segmentation of Object Boundaries in Synthetic Aperture Sonar Images  

E-print Network

Elastic Shapes Models for Improving Segmentation of Object Boundaries in Synthetic Aperture Sonar this approach using the segmentation of various objects in synthetic aperture sonar (SAS) images of underwater datasets. Keywords: Riemannian geometry, shape analysis, Bayesian active contours, synthetic aperture sonar

Srivastava, Anuj

345

Synthetic aperture systems; Proceedings of the Meeting, San Diego, CA, August 25, 26, 1983  

NASA Astrophysics Data System (ADS)

Synthetic aperture concepts are discussed, taking into account a synthetic aperture beam control system, a coherent optical system of modular imaging collectors providing an approach for a large aperture high angular resolution telescope in space, multimirror telescope alignment systems which employ fan beams and translation insensitive interferometers, translation insensitive heterodyne interferometers, and a synthetic aperture phase measurement system using a metering rod bridge with corner cubes. Topics related to design, simulation, and analysis are also explored, giving attention to a physical understanding of synthetic aperture arrays via simple models, design and performance of ranging telescopes, performance and phasing of multiline synthetic apertures, a computer model for evaluating synthetic aperture propogation, image-plane phase sensing for phased array telescopes, the testing of large telescope systems using multiple subapertures, and the influence of higher order noise in wavefront reconstruction. Synthetic aperture experiments are also considered.

Fender, J. S.

1984-01-01

346

Development of a ground signal processor for digital synthetic array radar data  

NASA Technical Reports Server (NTRS)

A modified APQ-102 sidelooking array radar (SLAR) in a B-57 aircraft test bed is used, with other optical and infrared sensors, in remote sensing of Earth surface features for various users at NASA Johnson Space Center. The video from the radar is normally recorded on photographic film and subsequently processed photographically into high resolution radar images. Using a high speed sampling (digitizing) system, the two receiver channels of cross-and co-polarized video are recorded on wideband magnetic tape along with radar and platform parameters. These data are subsequently reformatted and processed into digital synthetic aperture radar images with the image data available on magnetic tape for subsequent analysis by investigators. The system design and results obtained are described.

Griffin, C. R.; Estes, J. M.

1981-01-01

347

Synthetic Aperture Sonar Imaging via One-Way Wave Equations  

E-print Network

We develop an efficient algorithm for Synthetic Aperture Sonar imaging based on the one-way wave equations. The algorithm utilizes the operator-splitting method to integrate the one-way wave equations. The well-posedness of the one-way wave equations and the proposed algorithm is shown. A computational result against real field data is reported and the resulting image is enhanced by the BV-like regularization.

Huynh, Quyen

2009-01-01

348

An algorithm for inverse synthetic aperture imaging lidar based on sparse signal representation  

NASA Astrophysics Data System (ADS)

In actual applications of inverse synthetic aperture imaging lidar, the issue of sparse aperture data arises when continuous measurements are impossible or the collected data during some periods are not valid. Hence, the imaging results obtained by traditional methods are limited by high sidelobes. Considering the sparse structure of actual target space in high frequency radar application, a novel imaging method based on sparse signal representation is proposed in this paper. Firstly, the range image is acquired by traditional pulse compression of the optical heterodyne process. Then, the redundant dictionary is constructed through the sparse azimuth sampling positions and the signal form after the range compression. Finally, the imaging results are obtained by solving an ill-posed problem based on sparse regularization. Simulation results confirm the effectiveness of the proposed method.

Ren, X. Z.; Sun, X. M.

2014-12-01

349

SARUS: A Synthetic Aperture Real-time Ultrasound System.  

PubMed

The Synthetic Aperture Real-time Ultrasound System (SARUS) for acquiring and processing synthetic aperture (SA) data for research purposes is described. The specifications and design of the system are detailed, along with its performance for SA, nonlinear, and 3-D flow estimation imaging. SARUS acquires individual channel data simultaneously for up to 1024 transducer elements for a couple of heart beats, and is capable of transmitting any kind of excitation. The 64 boards in the system house 16 transmit and 16 receive channels each, where sampled channel data can be stored in 2 GB of RAM and processed using five field-programmable gate arrays (FPGAs). The fully parametric focusing unit calculates delays and apodization values in real time in 3-D space and can produce 350 million complex samples per channel per second for full non-recursive synthetic aperture B-mode imaging at roughly 30 high-resolution images/s. Both RF element data and beamformed data can be stored in the system for later storage and processing. The stored data can be transferred in parallel using the system's sixty-four 1-Gbit Ethernet interfaces at a theoretical rate of 3.2 GB/s to a 144-core Linux cluster. PMID:24658717

Jensen, Jørgen Arendt; Holten-Lund, Hans; Nilsson, Ronnie Thorup; Hansen, Martin; Larsen, Ulrik Darling; Domsten, Rune Petter; Tomov, Borislav Gueorguiev; Stuart, Matthias Bo; Nikolov, Svetoslav Ivanov; Pihl, Michael Johannes; Du, Yigang; Rasmussen, Joachim Hee; Rasmussen, Morten Fischer

2013-09-01

350

High-rate synthetic aperture communications in shallow water.  

PubMed

Time reversal communication exploits spatial diversity to achieve spatial and temporal focusing in complex ocean environments. Spatial diversity can be provided easily by a vertical array in a waveguide. Alternatively, spatial diversity can be obtained from a virtual horizontal array generated by two elements, a transmitter and a receiver, due to relative motion between them, referred to as a synthetic aperture. This paper presents coherent synthetic aperture communication results from at-sea experiments conducted in two different frequency bands: (1) 2-4 kHz and (2) 8-20 kHz. Case (1) employs binary-phase shift-keying modulation, while case (2) involves up to eight-phase shift keying modulation with a data rate of 30 kbits/s divided by the number of transmissions (diversity) to be accumulated. The receiver utilizes time reversal diversity combining followed by a single channel equalizer, with frequent channel updates to accommodate the time-varying channel due to coupling of space and time in the presence of motion. Two to five consecutive transmissions from a source moving at 4 kts over 3-6 km range in shallow water are combined successfully after Doppler compensation, confirming the feasibility of coherent synthetic aperture communications using time reversal. PMID:20000919

Song, H C; Hodgkiss, W S; Kuperman, W A; Akal, T; Stevenson, M

2009-12-01

351

Adaptive millimeter-wave synthetic aperture imaging for compressive sampling of sparse scenes.  

PubMed

We apply adaptive sensing techniques to the problem of locating sparse metallic scatterers using high-resolution, frequency modulated continuous wave W-band RADAR. Using a single detector, a frequency stepped source, and a lateral translation stage, inverse synthetic aperture RADAR reconstruction techniques are used to search for one or two wire scatterers within a specified range, while an adaptive algorithm determined successive sampling locations. The two-dimensional location of each scatterer is thereby identified with sub-wavelength accuracy in as few as 1/4 the number of lateral steps required for a simple raster scan. The implications of applying this approach to more complex scattering geometries are explored in light of the various assumptions made. PMID:24921545

Mrozack, Alex; Heimbeck, Martin; Marks, Daniel L; Richard, Jonathan; Everitt, Henry O; Brady, David J

2014-06-01

352

Region-Enhanced Imaging for Sparse-Aperture Passive Radar Mujdat Cetina and Aaron D. Lantermanb  

E-print Network

goal in passive radar imaging is to form images of aircraft using signals transmitted by commercial. Such passive multistatic radar systems have been developed to detect and track aircraft. If one couldRegion-Enhanced Imaging for Sparse-Aperture Passive Radar M¨ujdat C¸etina and Aaron D. Lantermanb a

�etin, Müjdat

353

Synthetic Aperture Focusing for Short-Lag Spatial Coherence Imaging  

PubMed Central

It has been demonstrated that short-lag spatial coherence (SLSC) ultrasound imaging can provide improved speckle SNR and lesion CNR compared to conventional B-mode images, especially in the presence of noise and clutter. Application of the van Cittert-Zernike theorem predicts that coherence among the ultrasound echoes received across an array is reduced significantly away from the transmit focal depth, leading to a limited axial depth of field in SLSC images. Transmit focus throughout the field of view can be achieved using synthetic aperture methods to combine multiple transmit events into a single final image. A synthetic aperture can be formed with either focused or diverging transmit beams. We explore the application of these methods to form synthetically focused channel data to create SLSC images with an extended axial depth of field. An analytical expression of SLSC image brightness through depth is derived for the dynamic receive focus case. Experimental results in a phantom and in vivo are presented and compared to dynamic receive focused SLSC images, demonstrating improved SNR and CNR away from the transmit focus and an axial depth of field four to five times longer. PMID:24658715

Bottenus, Nick; Byram, Brett C.; Dahl, Jeremy J.; Trahey, Gregg E.

2013-01-01

354

Micro-Doppler effect analysis and feature extraction in inverse synthetic aperture imaging LADAR imaging  

NASA Astrophysics Data System (ADS)

The micro-Doppler (m-D) effect describes the subtle micromotion features of a radar target and provides a new approach for feature extraction and auto radar target recognition. However, the microwave radar cannot provide enough resolution to detect the m-D effect of small targets and long distance targets. In order to obtain high range resolution for the extraction of subtle m-D signatures, inverse synthetic aperture imaging LADAR (ISAIL) is used here. Because the ISAIL uses a frequency modulation continuous wave signal, the m-D effect of ISAIL is different from the microwave radar. In this paper, the m-D effect of ISAIL is analyzed. The features of the m-D signatures in ISAIL are extracted by an improved Hough transform method associated with erosion and dilation operations in binary mathematical morphology. The simulations are given to validate the theoretical analyses and the proposed m-D extraction method. The experiment results show that the ISAIL can offer sufficient information of micromotions when the feature of motions is tiny.

He, Jin; Zhang, Qun; Luo, Ying; Liang, Xianjiao; Yang, Xiaoyou

2011-01-01

355

Microwave and Millimeter Wave Imaging Using Synthetic Aperture Focusing and Holographical Techniques  

NASA Technical Reports Server (NTRS)

Microwave and millimeter wave nondestructive testing and evaluation (NDT&E) methods have shown great potential for determining material composition in composite structures, determining material thickness or debond thickness between two layers, and determining the location and size of flaws, defects, and anomalies. The same testing methods have also shown great potential to produce relatively high-resolution images of voids inside Spray On Foam Insulation (SOFI) test panels using real focused methods employing lens antennas. An alternative to real focusing methods are synthetic focusing methods. The essence of synthetic focusing is to match the phase of the scattered signal to measured points spaced regularly on a plane. Many variations of synthetic focusing methods have already been developed for radars, ultrasonic testing applications, and microwave concealed weapon detection. Two synthetic focusing methods were investigated; namely, a) frequency-domain synthetic aperture focusing technique (FDSAFT), and b) wide-band microwave holography. These methods were applied towards materials whose defects were of low dielectric contrast like air void in SOFI. It is important to note that this investigation used relatively low frequencies from 8.2 GHz to 26.5 GHz that are not conducive for direct imaging of the SOFI. The ultimate goal of this work has been to demonstrate the capability of these methods before they are applied to much higher frequencies such as the millimeter wave frequency spectrum (e.g., 30-300 GHz).

Case, Joseph Tobias

2005-01-01

356

Phase error correction for synthetic-aperture phased-array imaging systems  

NASA Astrophysics Data System (ADS)

If one replaces the ordinary single receiver of a synthetic- aperture radar (SAR) with a linear array of receivers underneath the wings of an aircraft, one obtains a 3D signal history (to spatial dimensions plus the frequency dimension) that allows the computation of a 3D image (angle-angle- range) of a scene. Because of the limited extent of the wingspan, the cross-track resolution is limited, driving one to use high frequencies, such as 94 GHz, having a wavelength of 3.2 mm. At such short wavelengths, the motion of the wings during the synthetic-aperture integration time will cause large phase errors that will severely blur the image. This paper describes an approach to measuring and correcting these and other phase errors. The approach involves having three transmitters, each at a slightly different monotone frequency. Relative to the first receiver, the second is displaced along the direction of the array of receivers and the third is displaced perpendicular to that direction. The array of receivers can separate the three corresponding signals reflected form the ground from one another. We will show mathematical analysis that allows us to determine the phase errors at each receiver form these three signals. It is required either that the three transmitters experience the same phase errors (so they should be rigidly mounted together) or that the phase errors at the three transmitters are measured. No measurement of phase errors on the receivers is required.

Fienup, James R.

2000-11-01

357

Phase error suppression by low-pass filtering for synthetic aperture imaging ladar  

NASA Astrophysics Data System (ADS)

Compared to synthetic aperture radar (SAR), synthetic aperture imaging ladar (SAIL) is more sensitive to the phase errors induced by atmospheric turbulence, undesirable line-of-sight translation-vibration and waveform phase error, because the light wavelength is about 3-6 orders of magnitude less than that of the radio frequency. This phase errors will deteriorate the imaging results. In this paper, an algorithm based on low-pass filtering to suppress the phase error is proposed. In this algorithm, the azimuth quadratic phase history with phase error is compensated, then the fast Fourier transform (FFT) is performed in azimuth direction, after the low-pass filtering, the inverse FFT is performed, then the image is reconstructed simultaneously in the range and azimuth direction by the two-dimensional (2D) FFT. The highfrequency phase error can be effectively eliminated hence the imaging results can be optimized by this algorithm. The mathematical analysis by virtue of data-collection equation of side-looking SAIL is presented. The theoretical modeling results are also given. In addition, based on this algorithm, a principle scheme of optical processor is proposed. The verified experiment is performed employing the data obtained from a SAIL demonstrator.

Sun, Zhiwei; Hou, Peipei; Zhi, Ya'nan; Sun, Jianfeng; Zhou, Yu; Xu, Qian; Lu, Zhiyong; Liu, Liren

2014-09-01

358

Synthetic Aperture Focusing Technique: State of the art  

NASA Astrophysics Data System (ADS)

Ultrasonic inspection is one of the most promising nondestructive testing methods applied during manufacturing, pre-service and in-service inspection of components like pipes, vessels or steel plates. Starting from manual inspection, research and development during the last years lead to modern remote controlled and microprocessor controlled equipment with a wide variety of implemented signal processing algorithms. This article is concentrated upon the discussion of one of these signal processing algorithms, the so-called 'Synthetic Aperture Focusing Technique = SAFT'. The reason why more and more institution use this technique is the capability to get the highest information content on position, inclination, size and shape of single or of multiple scatterers like inclusions, voids or cracks in real industrial components.

Schmitz, V.; Mueller, W.; Schaefer, G.

359

Target detection and identification using synthetic aperture acoustics  

NASA Astrophysics Data System (ADS)

Recent research has shown that synthetic aperture acoustic (SAA) imaging may be useful for object identification. The goal of this work is to use SAA information to detect and identify four types of objects: jagged rocks, river rocks, small concave capped cylinders, and large concave capped cylinders. More specifically, we examine the use of frequency domain features extracted from the SAA images. We utilize Support Vector Machines (SVMs) for target detection, where an SVM is trained on target and non-target (background) examples for each target type. Assuming perfect target detection, we then compare multivariate Gaussian models for target identification. Experimental results show that SAA-based frequency domain features are able to detect and identify the four types of objects.

Knox, Mary; Tantum, Stacy; Collins, Leslie

2014-05-01

360

A One-Dimensional Synthetic-Aperture Microwave Radiometer  

NASA Technical Reports Server (NTRS)

A proposed one-dimensional synthetic- aperture microwave radiometer could serve as an alternative to either the two-dimensional synthetic-aperture radiometer described in the immediately preceding article or to a prior one-dimensional one, denoted the Electrically Scanned Thinned Array Radiometer (ESTAR), mentioned in that article. The proposed radiometer would operate in a pushbroom imaging mode, utilizing (1) interferometric cross-track scanning to obtain cross-track resolution and (2) the focusing property of a reflector for along-track resolution. The most novel aspect of the proposed system would be the antenna (see figure), which would include a cylindrical reflector of offset parabolic cross section. The reflector could be made of a lightweight, flexible material amenable to stowage and deployment. Other than a stowage/deployment mechanism, the antenna would not include moving parts, and cross-track scanning would not entail mechanical rotation of the antenna. During operation, the focal line, parallel to the cylindrical axis, would be oriented in the cross-track direction, so that placement of receiving/radiating elements at the focal line would afford the desired along-track resolution. The elements would be microwave feed horns sparsely arrayed along the focal line. The feed horns would be oriented with their short and long cross-sectional dimensions parallel and perpendicular, respectively, to the cylindrical axis to obtain fan-shaped beams having their broad and narrow cross-sectional dimensions parallel and perpendicular, respectively, to the cylindrical axis. The interference among the beams would be controlled in the same manner as in the ESTAR to obtain along-cylindrical- axis (cross-track) resolution and cross-track scanning.

Doiron, Terence; Piepmeier, Jeffrey

2010-01-01

361

Initial Images of the Synthetic Aperture Radiometer 2D-STAR  

Technology Transfer Automated Retrieval System (TEKTRAN)

Initial results obtained using a new synthetic aperture radiometer, 2D-STAR, a dual polarized, L-band radiometer that employs aperture synthesis in two dimensions are presented and analyzed. This airborne instrument is the natural evolution of a previous design that employed employs aperture synthes...

362

Synthetic Aperture Processing of Buried Object Scanning Sonar Data Steven G. Schock  

E-print Network

1 Synthetic Aperture Processing of Buried Object Scanning Sonar Data Steven G. Schock James Wulf object scanning sonar (BOSS) imagery. Time delay focusing coherently sums acoustic data measured (synthetic aperture sonar) motion compensation is implemented by calculating the changes in projector

Schock, Steven

363

3-D Terahertz Synthetic-Aperture Imaging and Spectroscopy  

NASA Astrophysics Data System (ADS)

Terahertz (THz) wavelengths have attracted recent interest in multiple disciplines within engineering and science. Situated between the infrared and the microwave region of the electromagnetic spectrum, THz energy can propagate through non-polar materials such as clothing or packaging layers. Moreover, many chemical compounds, including explosives and many drugs, reveal strong absorption signatures in the THz range. For these reasons, THz wavelengths have great potential for non-destructive evaluation and explosive detection. Three-dimensional (3-D) reflection imaging with considerable depth resolution is also possible using pulsed THz systems. While THz imaging (especially 3-D) systems typically operate in transmission mode, reflection offers the most practical configuration for standoff detection, especially for objects with high water content (like human tissue) which are opaque at THz frequencies. In this research, reflection-based THz synthetic-aperture (SA) imaging is investigated as a potential imaging solution. THz SA imaging results presented in this dissertation are unique in that a 2-D planar synthetic array was used to generate a 3-D image without relying on a narrow time-window for depth isolation cite [Shen 2005]. Novel THz chemical detection techniques are developed and combined with broadband THz SA capabilities to provide concurrent 3-D spectral imaging. All algorithms are tested with various objects and pressed pellets using a pulsed THz time-domain system in the Northwest Electromagnetics and Acoustics Research Laboratory (NEAR-Lab).

Henry, Samuel C.

364

Radar Imaging Systems Joseph Charpentier  

E-print Network

Radar Imaging Systems Joseph Charpentier Department of Computing Sciences Villanova University types of radar imaging systems; synthetic aperture radar (SAR), through-the-wall radar, and digital holographic near field radar. Each system surveyed experiments that improved the quality of the resulting

365

Increasing the dynamic range of synthetic aperture vector flow imaging  

NASA Astrophysics Data System (ADS)

In current ultrasound systems the dynamic range of detectable velocities is susceptible to the selected pulse repetition frequency, thus limiting the dynamic range of flow mapping. To establish the feasibility of extending the range of detectable velocities towards low velocity vessels, results are presented using synthetic aperture which increases the frame-to-frame signal correlation of the scatterer displacement while providing continuous data. In this paper, recursive synthetic aperture acquisition, directional beamforming, and cross-correlation are used to produce B-mode and vector velocity images. The emissions for the two imaging modes are interleaved 1-to-1 ratio, providing a high frame rate equal to the effective pulse repetition frequency of each imaging mode. The direction of the flow is estimated, and the velocity is then determined in that direction. This method works for all angles, including fully axial and transverse flows. The method is investigated using Field II simulations and data from the experimental ultrasound scanner SARUS, acquired from a circulating flow rig with a parabolic flow. A 7 MHz linear array transducer is used, and several pulse repetition frequencies are synthesized in a simulated flow phantom with linearly increasing velocity and in a dual-vessel phantom with laminar flow with peak velocities of 0.05 m/s and 0.5 m/s. The experimental measurements are made with laminar flow as in the simulations. For the simulated and experimental vessel with peak velocity of 0.05 m/s and flow angle of 75°, the relative bias is -0.29% and -3.19%, and the relative standard deviations are 2.39% and 5.75% respectively. For the simulated and experimental vessel with peak velocity of 0.5 m/s and flow angle of -90°, the relative biases are -4.30% and -7.37%, and the relative standard deviations are 1.59% and 6.12%, respectively. The presented method can improve the estimates by synthesizing a lower pulse repetition frequency, thereby increasing the dynamic range of the vector velocity imaging.

Villagomez Hoyos, Carlos; Stuart, Matthias Bo; Jensen, Jørgen Arendt

2014-03-01

366

Synthetic Aperture Focusing Technique 3D-CAD-SAFT  

NASA Astrophysics Data System (ADS)

Till the 80's ultrasonic holography has been used as an analyzing technique, a procedure which has been replaced by the Synthetic Aperture Focusing Technique "SAFT." This technique has been applied on metallic components in different power plants, mostly on pipe systems on pressure vessels or on specimen made of composite or concrete material. SAFT exists in different versions, either in 2D or 3D, for plane or arbitrarily shaped surfaces, for pulse echo or pitch- and catch arrangements. The defect sizes ranged from 100 ?m in turbine shafts till fractures of meters in research pressure vessels. The paper covers the lastest results of the SAFT-reconstruction technique under Windows NT which has been guided by the experience obtained in the field. It contributes to the currently discussed question of the possible benefit using TOFD—techniques versus pulse echo techniques; the target has been a fatigue crack in a pipe segment which was investigated by different insonification angles, wave modes and probe arrangements. The results are evaluated with respect to signal-to-noise ratio improvement; problems of TOFD are demonstrated using an animation procedure which allows to walk through the weld in three orthogonal directions. A special example will be shown from a bore hole inspection of water power station valves where the reconstruction procedure follows the radial axial insonification planes. The multi-line SAFT images can be cut according to the situation of the crack position and orientation.

Schmitz, V.; Kröning, M.; Chakhlov, S.; Fischer, W.

2000-05-01

367

Synthetic interferometer radar for topographic mapping  

Microsoft Academic Search

The production of topographic maps requires two kinds of information. First, the detail to be placed on the map sheet must be identified. Second, the positions of the various objects and features must be measured in three dimensions. Current airborne radar technology provides the means to satisfy both of these requirements in adverse weather and at any time, day or

L. C. Graham

1974-01-01

368

Distributed Computing Framework for Synthetic Radar Application  

NASA Technical Reports Server (NTRS)

We are developing an extensible software framework, in response to Air Force and NASA needs for distributed computing facilities for a variety of radar applications. The objective of this work is to develop a Python based software framework, that is the framework elements of the middleware that allows developers to control processing flow on a grid in a distributed computing environment. Framework architectures to date allow developers to connect processing functions together as interchangeable objects, thereby allowing a data flow graph to be devised for a specific problem to be solved. The Pyre framework, developed at the California Institute of Technology (Caltech), and now being used as the basis for next-generation radar processing at JPL, is a Python-based software framework. We have extended the Pyre framework to include new facilities to deploy processing components as services, including components that monitor and assess the state of the distributed network for eventual real-time control of grid resources.

Gurrola, Eric M.; Rosen, Paul A.; Aivazis, Michael

2006-01-01

369

Feasibility of synthetic aperture altimeter data in ice charting  

NASA Astrophysics Data System (ADS)

We demonstrate the possibility to utilise synthetic aperture altimeter data in operational ice charting. Different waveform parameters from Cryosat-2 SIRAL measurements are compared to AARI ice charts over the Barents and Kara seas. It is shown that polygons of different ice types are distinguishable in the altimeter data. The most important sea ice application of satellite altimeters today is measuring the thickness of Arctic winter sea ice. However, the use of altimeters to support ice mapping has been suggested already more than 30 years ago. Due to advent of imaging instruments more suitable for ice charting, most notably the SAR, altimeters have remained tools for sea ice science. They are however used operationally to determine sea height anomaly and significant wave height. Our input data is the SAR mode Level 1B data of CryoSat-2. We only consider the waveform data and calculate simple parameters describing the shape of the waveform such as the pulse peakiness and backscatter coefficient sigma_0. We compare these to ice stages of development given in the ice chart. As expected, ice edge is clearly visible in the altimeter data. What is more promising for operational ice thickness, areas of old ice can be distinguished from areas of young ice and nilas. Altimeters provide an independent source of sea ice information to complement SAR and passive microwave data. Albeit low resolution, altimeter data may prove valuable at times and locations where other data sources are unavailable. SAR data is frequently available for our study area, but our methods are applicable to areas where SAR data is scarce such as the Southern ice covered seas. Furthermore, our results here are directly applicable to the future Sentinel-3 altimeter data.

Rinne, Eero; Kangas, Antti

370

Synthetic aperture laser optical feedback imaging using a translational scanning with galvanometric mirrors  

NASA Astrophysics Data System (ADS)

In this paper we present an experimental setup based on Laser Optical Feedback Imaging (LOFI) and on Synthetic Aperture (SA) with translational scanning by galvanometric mirrors for the purpose of making deep and resolved images through scattering media. We provide real 2D optical synthetic-aperture image of a fixed scattering target with a moving aperture and an isotropic resolution. We demonstrate theoretically and experimentally that we can keep microscope resolution beyond the working distance. A photometric balance is made and we show that the number of photons participating in the final image decreases with the square of the reconstruction distance. This degradation is partially compensated by the high sensitivity of LOFI.

Glastre, Wilfried; Jacquin, Olivier; Hugon, Olivier; Guillet de Chatellus, Hugues; Lacot, Eric

2012-08-01

371

Radar sensing of the ocean  

Microsoft Academic Search

Radar remote sensing of the ocean has been the subject of research for about 20 years. Spaceborne radar altimetry and scatterometry are approaching maturity, and synthetic-aperture radars (SAR) show great promise. The principles of radar scattering from the sea are outlined here, along with some recently discovered questions. For wind-vector scatterometry, the principle is presented, and remaining uncertainties are outlined.

RICHARD K. MOORE

1985-01-01

372

Observations of the marine environment from spaceborne side-looking real aperture radars  

NASA Technical Reports Server (NTRS)

Real aperture, side looking X-band radars have been operated from the Soviet Cosmos-1500, -1602, -1766 and Ocean satellites since 1984. Wind velocities were inferred from sea surface radar scattering for speeds ranging from approximately 2 m/s to those of hurricane proportions. The wind speeds were within 10-20 percent of the measured in situ values, and the direction of the wind velocity agreed with in situ direction measurements within 20-50 deg. Various atmospheric mesoscale eddies and tropical cyclones were thus located, and their strengths were inferred from sea surface reflectivity measurements. Rain cells were observed over both land and sea with these spaceborne radars. Algorithms to retrieve rainfall rates from spaceborne radar measurements were also developed. Spaceborne radars have been used to monitor various marine hazards. For example, information derived from those radars was used to plan rescue operations of distressed ships trapped in sea ice. Icebergs have also been monitored, and oil spills were mapped. Tsunamis produced by underwater earthquakes were also observed from space by the radars on the Cosmos 1500 series of satellites. The Cosmos-1500 satellite series have provided all weather radar imagery of the earths surface to a user community in real time by means of a 137.4 MHz Automatic Picture Transmission channel. This feature enabled the radar information to be used in direct support of Soviet polar maritime activities.

Kalmykov, A. I.; Velichko, S. A.; Tsymbal, V. N.; Kuleshov, Yu. A.; Weinman, J. A.; Jurkevich, I.

1993-01-01

373

GPU-Based Minimum Variance Beamformer for Synthetic Aperture Imaging of the Eye.  

PubMed

Minimum variance (MV) beamforming has emerged as an adaptive apodization approach to bolster the quality of images generated from synthetic aperture ultrasound imaging methods that are based on unfocused transmission principles. In this article, we describe a new high-speed, pixel-based MV beamforming framework for synthetic aperture imaging to form entire frames of adaptively apodized images at real-time throughputs and document its performance in swine eye imaging case examples. Our framework is based on parallel computing principles, and its real-time operational feasibility was realized on a six-GPU (graphics processing unit) platform with 3,072 computing cores. This framework was used to form images with synthetic aperture imaging data acquired from swine eyes (based on virtual point-source emissions). Results indicate that MV-apodized image formation with video-range processing throughput (>20 fps) can be realized for practical aperture sizes (128 channels) and frames with ?/2 pixel spacing. Also, in a corneal wound detection experiment, MV-apodized images generated using our framework revealed apparent contrast enhancement of the wound site (10.8 dB with respect to synthetic aperture images formed with fixed apodization). These findings indicate that GPU-based MV beamforming can, in real time, potentially enhance image quality when performing synthetic aperture imaging that uses unfocused firings. PMID:25638315

Yiu, Billy Y S; Yu, Alfred C H

2015-03-01

374

Passive Synthetic Aperture Hitchhiker Imaging of Ground Moving Targets - Part 2: Performance Analysis.  

PubMed

In Part 1 of this work, we present a passive synthetic aperture imaging and velocity estimation method for ground moving targets using a network of passive receivers. The method involves inversion of a Radon transform type forward model via a novel filtered backprojection approach combined with entropy optimization. The method is applicable to noncooperative transmitters of opportunity where the transmitter locations and transmitted waveforms are unknown. Furthermore, it can image multiple targets moving at different velocities in arbitrary imaging geometries. In this paper, we present a detailed analysis of the performance of our method. First the resolution analysis in position and velocity spaces is presented. The analysis identifies several factors that contribute positively or negativity towards position and velocity resolution. Next, we present a novel theory to analyze and predict smearing artifacts in position images due to error in velocity estimation of moving targets. Specifically, we show that small errors in the velocity estimation result in small positioning errors. We present extensive numerical simulations to demonstrate the theoretical results. While our primary interest lies in radar, the theory, methods and algorithms introduced in our work are also applicable to passive acoustic, seismic, and microwave imaging. PMID:25020091

Wacks, Steven; Yazici, Birsen

2014-07-01

375

Web Application System with Synthetic Aperture Rader Image Processing for Education  

NASA Astrophysics Data System (ADS)

Remotely sensed images observed by synthetic aperture radar (SAR) become to be more significant for a variety of purposes. It is necessary to process and focus SAR images at a user's side for required precision. This paper presents a concept, a system structure, and an implementation method for a web application system with a SAR image processing for education. The system employs Ajax technology in consideration of current computer and network systems. This system has three software components, a SAR server, an HTTP server, and a web browser in each terminal computer. The SAR server is the main component for managing the SAR database and processing all SAR data sets. The range-Doppler method is adopted as a focusing algorithm. Three displaying measures are newly introduced since the SAR images are sets of mass complex number pixels. Operation of SAR image, sample processed images are shown to exhibit actual examples of processing ALOS PALSAR (Advanced Land Observing Satellite Phased Array type L-band SAR) data. From step-by-step processing results, the proposed web application system was demonstrated to provide a useful graphical user interface (GUI) and to produce the SAR image with adjusted parameters by using dialogs.

Teramoto, Yuuhei; Ito, Yosuke; Abe, Kenji

376

Classification of earth terrain using polarimetric synthetic aperture radar images  

NASA Technical Reports Server (NTRS)

Supervised and unsupervised classification techniques are developed and used to classify the earth terrain components from SAR polarimetric images of San Francisco Bay and Traverse City, Michigan. The supervised techniques include the Bayes classifiers, normalized polarimetric classification, and simple feature classification using discriminates such as the absolute and normalized magnitude response of individual receiver channel returns and the phase difference between receiver channels. An algorithm is developed as an unsupervised technique which classifies terrain elements based on the relationship between the orientation angle and the handedness of the transmitting and receiving polariation states. It is found that supervised classification produces the best results when accurate classifier training data are used, while unsupervised classification may be applied when training data are not available.

Lim, H. H.; Swartz, A. A.; Yueh, H. A.; Kong, J. A.; Shin, R. T.; Van Zyl, J. J.

1989-01-01

377

Earth Studies Using L-band Synthetic Aperture Radar  

NASA Technical Reports Server (NTRS)

L-band SAR has played an important role in studies of the Earth by revealing the nature of the larger-scale (decimeter) surface features. JERS-1, by supplying multi-seasonal coverage of the much of the earth, has demonstrated the importance of L-band SARs. Future L-band SARs such as ALOS and LightSAR will pave the way for science missions that use SAR instruments. As technology develops to enable lower cost SAR instruments, missions will evolve to each have a unique science focus. International coordination of multi-parameter constellations and campaigns will maximize science return.

Rosen, Paul A.

1999-01-01

378

Advances in spaceborne synthetic aperture radar sensor technology  

NASA Technical Reports Server (NTRS)

The evolution of space SARs for NASA projects since Seasat (1978) is surveyed, with an emphasis on hardware development. The fundamental principles of SAR are reviewed; the SIR-A and SIR-B instruments flown as Shuttle payloads are characterized; their antennas, transmitters, receivers, and data subsystems are described; the advantages offered by the SIR-C dual-frequency (L and C band) dual-polarization distributed SAR (being developed for a future Shuttle flight and as the basis of an SAR for the Earth Observing System) are explained; and a number of technical challenges are identified (including RF elements, structural fidelity, pointing accuracy, data handling, and dc power). Drawings, diagrams, sample images, photographs, and tables are provided.

Caro, E. R.; Ruzek, M.

1986-01-01

379

Geologic process studies using Synthetic Aperture Radar (SAR) data  

NASA Technical Reports Server (NTRS)

The use of SAR data to study geologic processes for better understanding of recent tectonic activity and climate change as well as the mitigation of geologic hazards and exploration for nonrenewable resources is discussed. The geologic processes that are particularly amenable to SAR-based data include volcanism; soil erosion, degradation, and redistribution; coastal erosion and inundation; glacier fluctuations; permafrost; and crustal motions. When SAR data are combined with data from other planned spaceborne sensors including ESA ERS, the Japanese Earth Resources Satellite, and the Canadian Radarsat, it will be possible to build a time-series view of temporal changes over many regions of earth.

Evans, Diane L.

1992-01-01

380

Polarimetric Synthetic Aperture Radar data for Crop Cover Classification  

NASA Astrophysics Data System (ADS)

The interest in crop inventory through the use of microwave sensors is on the rise owing to need for accurate crop forecast and the availability of multi polarization data. Till recently, the temporal amplitude data has been used for crop discrimination as well as acreage estimation. With the availability of dual and quadpol data, the differential response of crop geometry at various crop growth stages to various polarizations is being exploited for discrimination and classification of crops. An attempt has been made in the current study with RISAT1 and Radarsat2 C-band single, dual, fully and hybrid polarimetric data for crop inventory. The single date hybrid polarimetric data gave comparable results to the three date single polarization data as well as with the single date fully polarimetric data for crops like rice and cotton.

Ramana, K. V.; Srikanth, P.; Deepika, U.; Sesha Sai, M. V. R.

2014-11-01

381

Three-dimensional subsurface imaging synthetic aperture radar  

SciTech Connect

Inadequate resources, aggravated by the limited capabilities of existing site characterization technologies, require that new systems be developed to effectively aid site cleanup. The quantity, condition, and the precise location of buried waste storage containers is often unknown, and is always difficult to assess. Significant safety hazards may also be present at these sites. Therefore, new non-invasive detection techniques are needed that will be cost effective, user friendly, and have a growth path toward a system capable of accessing remote terrain. These detection methods must be economical to use and be capable of exploring large land areas quickly with minimal personnel risk. They should provide the precision for identifying the size, depth, type, and possibly the condition of the waste containers.

Wuenschel, E.

1995-12-31

382

YSAR and YINSAR: Compact, LowCost Synthetic Aperture Radars  

E-print Network

. This paper reports the cur­ rent status of YSAR and YINSAR and presents the latest images from the YSAR data different fields of study. One such field is archaeology. Several re­ searchers [1, 2, 3] have used company could use interferometric SAR to estimate the volume of material removed from a site. Power plants

Long, David G.

383

Polarimetric synthetic aperture radar utilized to track oil spills  

NASA Astrophysics Data System (ADS)

The continued demand for crude oil and related petroleum products along with the resulting upward spiral of the market price of oil have forced oil exploration and production companies to seek out new reserves farther offshore and in deeper waters. The United States is among the top five nations globally in terms of estimated offshore oil reserves and petroleum production. Yet deepwater drilling to extract these reserves is a major engineering challenge for oil companies. Moreover, such drilling activity also comes with a significant environmental risk, and the extremely high pressures associated with deepwater oil wells mean that the mitigation of accidental releases from a deepwater spill is truly a challenging endeavor.

Migliaccio, Maurizio; Nunziata, Ferdinando; Brown, Carl E.; Holt, Benjamin; Li, Xiaofeng; Pichel, William; Shimada, Masanobu

2012-04-01

384

Doppler centroid estimation ambiguity for synthetic aperture radars  

NASA Technical Reports Server (NTRS)

A technique for estimation of the Doppler centroid of an SAR in the presence of large uncertainty in antenna boresight pointing is described. Also investigated is the image degradation resulting from data processing that uses an ambiguous centroid. Two approaches for resolving ambiguities in Doppler centroid estimation (DCE) are presented: the range cross-correlation technique and the multiple-PRF (pulse repetition frequency) technique. Because other design factors control the PRF selection for SAR, a generalized algorithm is derived for PRFs not containing a common divisor. An example using the SIR-C parameters illustrates that this algorithm is capable of resolving the C-band DCE ambiguities for antenna pointing uncertainties of about 2-3 deg.

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

1989-01-01

385

Synthetic aperture radar signal data compression using block adaptive quantization  

NASA Technical Reports Server (NTRS)

This paper describes the design and testing of an on-board SAR signal data compression algorithm for ESA's ENVISAT satellite. The Block Adaptive Quantization (BAQ) algorithm was selected, and optimized for the various operational modes of the ASAR instrument. A flexible BAQ scheme was developed which allows a selection of compression ratio/image quality trade-offs. Test results show the high quality of the SAR images processed from the reconstructed signal data, and the feasibility of on-board implementation using a single ASIC.

Kuduvalli, Gopinath; Dutkiewicz, Melanie; Cumming, Ian

1994-01-01

386

Neutral atmospheric delay in interferometric synthetic aperture radar applications  

E-print Network

structure to use when using InSAR data to constrain geophysical models. INDEX TERMS: 1206 Geodesy and Gravity: Crustal movements--interplate (8155); 1208 Geodesy and Gravity: Crustal movements--intraplate (8110); 1243 Geodesy and Gravity: Space geodetic surveys; 1244 Geodesy and Gravity: Standards

387

Signal processing of FMCW Synthetic Aperture Radar data  

Microsoft Academic Search

In the field of airborne earth observation there is special attention to compact, cost effective, high resolution imaging sensors. Such sensors are foreseen to play an important role in small-scale remote sensing applications, such as the monitoring of dikes, watercourses, or highways. Furthermore, such sensors are of military interest; reconnaissance tasks could be performed with small unmanned aerial vehicles (UAVs),

A. Meta

2006-01-01

388

Reconstruction of synthetic aperture digital Fresnel hologram by use of the screen division method  

NASA Astrophysics Data System (ADS)

Synthetic aperture digital holography can effectively increase the recording area of digital hologram, which is propitious to extend the range and improve the resolution of the reconstruction image. However, the area of synthetic aperture digital hologram is usually very large, and thus if it is directly reconstructed, the numerical reconstruction process may can't progress in order for the limitation of the disposal capability of computer. Therefore, a screen-division reconstruction method for synthetic aperture digital Fresnel hologram is proposed in the paper. Relatively to the direct reconstruction method, the screen division reconstruction method can effectively reduce the area of the hologram participant in the numerical operation process and thus make it possible to reconstruct the synthetic aperture digital Fresnel hologram which area exceeds the disposal capability of computer. The synthetic aperture digital Fresnel hologram with large area is acquired by the precise control for the removal of CCD array and then reconstructed by the proposed screen division reconstruction method. The experimental results show that, the introduced numerical reconstruction method can well correct the position and phase distribution of the sub-reconstructed-images and obtain accurate synthetic numerical reconstruction image.

Jiang, Hongzhen; Zhao, Jianlin; Di, Jianglei

2014-12-01

389

Imaging with Radar  

NSDL National Science Digital Library

This interactive activity from NOVA features synthetic aperture radar (SAR), which uses radio waves to create high-quality images. Examine SAR images of Washington, D.C., and learn about this technology's unique advantages.

2004-01-29

390

ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture  

NASA Technical Reports Server (NTRS)

The measurement of soil moisture from space requires putting relatively large microwave antennas in orbit. Aperture synthesis, an interferometric technique for reducing the antenna aperture needed in space, offers the potential for a practical means of meeting these requirements. An aircraft prototype, electronically steered thinned array L-band radiometer (ESTAR), has been built to develop this concept and to demonstrate its suitability for the measurement of soil moisture. Recent flights over the Walnut Gulch Watershed in Arizona show good agreement with ground truth and with measurements with the Pushbroom Microwave Radiometer (PBMR).

Le Vine, D. M.; Griffis, A.; Swift, C. T.; Jackson, T. J.

1992-01-01

391

Data volume reduction for imaging radar polarimetry  

NASA Technical Reports Server (NTRS)

Two alternative methods are disclosed for digital reduction of synthetic aperture multipolarized radar data using scattering matrices, or using Stokes matrices, of four consecutive along-track pixels to produce averaged data for generating a synthetic polarization image.

Zebker, Howard A. (Inventor); Held, Daniel N. (Inventor); van Zul, Jakob J. (Inventor); Dubois, Pascale C. (Inventor); Norikane, Lynne (Inventor)

1989-01-01

392

Data volume reduction for imaging radar polarimetry  

NASA Technical Reports Server (NTRS)

Two alternative methods are presented for digital reduction of synthetic aperture multipolarized radar data using scattering matrices, or using Stokes matrices, of four consecutive along-track pixels to produce averaged data for generating a synthetic polarization image.

Zebker, Howard A. (inventor); Held, Daniel N. (inventor); Vanzyl, Jakob J. (inventor); Dubois, Pascale C. (inventor); Norikane, Lynne (inventor)

1988-01-01

393

Prototype development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR  

NASA Technical Reports Server (NTRS)

Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 55 GHz will be presented. The laboratory prototype is being developed to demonstrate the technologies and system design needed to do millimeter-wave atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large thinned aperture Y-array on a geostationary satellite, and to use aperture synthesis to obtain images of the Earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system.

Tanner, A. B.; Wilson, W. J.; Kangaslahti, P. P.; Lambrigsten, B. H.; Dinardo, S. J.; Piepmeier, J. R.; Ruf, C. S.; Rogacki, S.; Gross, S. M.; Musko, S.

2004-01-01

394

Operations Manager Tim Miller checks out software for the Airborne Synthetic Aperature Radar (AIRSAR  

NASA Technical Reports Server (NTRS)

Tim Miller checks out software for the Airborne Synthetic Aperture Radar (AIRSAR). He was the AIRSAR operations manager for NASA's Jet Propulsion Laboratory. The AIRSAR produces imaging data for a range of studies conducted by the DC-8. NASA is using a DC-8 aircraft as a flying science laboratory. The platform aircraft, based at NASA's Dryden Flight Research Center, Edwards, Calif., collects data for many experiments in support of scientific projects serving the world scientific community. Included in this community are NASA, federal, state, academic and foreign investigators. Data gathered by the DC-8 at flight altitude and by remote sensing have been used for scientific studies in archeology, ecology, geography, hydrology, meteorology, oceanography, volcanology, atmospheric chemistry, soil science and biology.

1998-01-01

395

Autofocusing circular synthetic aperture sonar imagery using phase corrections modeled as generalized cones.  

PubMed

Circular synthetic aperture sonar (CSAS) is a coherent aperture synthesis technique that utilizes backscattered acoustic information from an encircled scene to generate information rich, high-resolution imagery. The aperture length required for image synthesis is much longer than in its linear synthetic aperture sonar counterpart and can result in challenging phase delay and navigation estimation constraints. Residual uncorrected phase errors manifest as focus aberrations in reconstructed CSAS imagery. This paper demonstrates that phase error in image patches can be approximated as an aspect variant linear phase shift representable as a generalized cone in wave-number space. If the geometry of the generalized cone is known, it can be applied as the spectral phase of an inverse filter for aberration correction. A method is derived for reconstructing the error cone geometry from independent estimates of its local curvatures, which are found via a series of one-dimensional line searches that maximize the focus of CSAS sub-aperture images. This approach is applied to real and simulated CSAS data containing aperture distortions, and the results successfully demonstrate estimation and correction of the underlying focus aberrations. PMID:25096096

Marston, Timothy M; Kennedy, Jermaine L; Marston, Philip L

2014-08-01

396

A Prototype Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) for Atmospheric Temperature Sounding  

NASA Technical Reports Server (NTRS)

A viewgraph presentation of a prototype Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) for atmospheric temperature sounding is shown. The topics include: 1) Overview; 2) Requirements & Error allocations; 3) Design; 4) Problems, and How We Solved Them; and 5) Results

Tanner, Alan B.; Lambrigsten, B. H.; Brown, S. T.; Wilson, W. J.; Piepmeier, J. R.; Ruf, C. S.; Lim, B.

2006-01-01

397

GeoSTAR - A Synthetic Aperture Microwave Sounder for Geostationary Missions  

NASA Technical Reports Server (NTRS)

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new microwave atmospheric sounder under development. It will bring capabilities similar to those now available on low-earth orbiting environmental satellites to geostationary orbit - where such capabilities have not been available. GeoSTAR will synthesize the multimeter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now. The synthetic aperture approach has until recently not been feasible, due to the high power needed to operate the on-board high-speed massively parallel processing system required for 2D-synthesis, as well as a number of system and calibration obstacles. The development effort under way at JPL, with important contributions from the Goddard Space Flight Center and the University of Michigan, is intended to demonstrate the measurement concept and retire much of the technology risk.

Lambrigtsen, Bjorn; Wilson, William; Tanner, Alan; Kangaslahti, Pekka

2004-01-01

398

A Ka Band Imaging Radar: DRIVE on Board ONERA Motorglider  

Microsoft Academic Search

Following previous studies, a concept of low-cost imaging Ka-Band radar is presented in this paper. This radar is integrated into under-wings pods that are fixed on a STEMME S10VT motorglider. This radar concept combines real aperture in the cross-track direction, by the antennas geometrical aperture, and synthetic aperture in the along-track direction, realized with the aircraft motion. Radar front-end uses

J. F. Nouvel; H. Jeuland; G. Bonin; S. Roques; O. Du Plessis; J. Peyret

2006-01-01

399

SAR Imaging from Partial-Aperture Data with Frequency-Band Omissions  

E-print Network

," demonstrating the effectiveness of the proposed approach. Keywords: synthetic aperture radar, wide-angle imaging Traditional image formation techniques for synthetic aperture radar (SAR) rely on data on a narrow collection of coherent data across longer times and flight paths. Second, unmanned air vehicle (UAV

Moses, Randolph L.

400

SUBMITTED TO IEE PROCEEDINGS RADAR, SONAR & NAVIGATION 1 Region-Enhanced Passive Radar Imaging  

E-print Network

SUBMITTED TO IEE PROCEEDINGS RADAR, SONAR & NAVIGATION 1 Region-Enhanced Passive Radar Imaging M;SUBMITTED TO IEE PROCEEDINGS RADAR, SONAR & NAVIGATION 2 Abstract We adapt and apply a recently-developed region-enhanced synthetic aperture radar (SAR) image reconstruction technique to the problem of passive

Willsky, Alan S.

401

Prototype Development of a Geostationary Synthetic Thinned Aperture Radiometer, GeoSTAR  

NASA Technical Reports Server (NTRS)

Preliminary details of a 2-D synthetic aperture radiometer prototype operating from 50 to 58 GHz will be presented. The instrument is being developed as a laboratory testbed, and the goal of this work is to demonstrate the technologies needed to do atmospheric soundings with high spatial resolution from Geostationary orbit. The concept is to deploy a large sparse aperture Y-array from a geostationary satellite, and to use aperture synthesis to obtain images of the earth without the need for a large mechanically scanned antenna. The laboratory prototype consists of a Y-array of 24 horn antennas, MMIC receivers, and a digital cross-correlation sub-system. System studies are discussed, including an error budget which has been derived from numerical simulations. The error budget defines key requirements, such as null offsets, phase calibration, and antenna pattern knowledge. Details of the instrument design are discussed in the context of these requirements.

Tanner, Alan B.; Wilson, William J.; Kangaslahti, Pekka P.; Lambrigsten, Bjorn H.; Dinardo, Steven J.; Piepmeier, Jeffrey R.; Ruf, Christopher S.; Rogacki, Steven; Gross, S. M.; Musko, Steve

2004-01-01

402

Clinical evaluation of synthetic aperture sequential beamforming ultrasound in patients with liver tumors.  

PubMed

Medical ultrasound imaging using synthetic aperture sequential beamforming (SASB) has for the first time been used for clinical patient scanning. Nineteen patients with cancer of the liver (hepatocellular carcinoma or colorectal liver metastases) were scanned simultaneously with conventional ultrasound and SASB using a commercial ultrasound scanner and abdominal transducer. SASB allows implementation of the synthetic aperture technique on systems with restricted data handling capabilities due to a reduction in the data rate in the scanner by a factor of 64. The image quality is potentially maintained despite the data reduction. A total of 117 sequences were recorded and evaluated blinded by five radiologists from a clinical perspective. Forty-eight percent of the evaluations were in favor of SASB, 33% in favor of conventional ultrasound and 19 % were equal, that is, a clear, but non-significant trend favoring SASB over conventional ultrasound (p = 0.18), despite the substantial data reduction. PMID:25308936

Hansen, Peter Møller; Hemmsen, Martin; Brandt, Andreas; Rasmussen, Joachim; Lange, Theis; Krohn, Paul Suno; Lönn, Lars; Jensen, Jørgen Arendt; Nielsen, Michael Bachmann

2014-12-01

403

Analytical comparison of sensor signal processing enhancements for NDT synthetic aperture ultrasonic imaging  

Microsoft Academic Search

The results of a detailed analytical study of the effects of sensor processing techniques on clutter suppression and image enhancement for nondestructive testing (NDT) systems are presented. A relatively simple beamforming\\/diffraction model is developed for near-field, wideband, synthetic aperture ultrasonic imaging in NDT systems. The physical model is used to quantitatively evaluate a variety of front-end sensor signal processing tradeoffs

Seth D. Silverstein; Lewis J. Thomas

1993-01-01

404

Optical image reconstruction using an astigmatic lens for synthetic-aperture imaging ladar  

NASA Astrophysics Data System (ADS)

An optical processor for synthetic-aperture imaging ladar (SAIL) utilizing one astigmatic lens is proposed. The processor comprises two structures of transmitting and reflecting. The imaging process is mathematically analyzed using the unified data-collection equation of side-looking and down-looking SAILs. Results show that the astigmatic lens can be replaced with a cylindrical lens on certain conditions. To verify this concept, laboratory experiment is conducted, the imaging result of data collected from one SAIL demonstrator is given.

Sun, Zhiwei; Hou, Peipei; Zhi, Yanan; Sun, Jianfeng; Zhou, Yu; Xu, Qian; Liu, Liren

2014-11-01

405

Sizing of cracks embedded in sub-cladding using the ultrasonic synthetic aperture focusing technique (SAFT)  

Microsoft Academic Search

This paper deals with the experimental work carried out to demonstrate the feasibility of ultrasonic Synthetic Aperture Focusing Technique (SAFT) to obtain improved detection and sizing of vertical\\/inclined (10° and 15°) simulated cracks underneath different claddings. Crack heights ranging from 1.68mm to 19.04mm underneath stainless steel, Inconel and ferritic steel cladding could be sized with an accuracy of ±0.1 to

Sony Baby; T. Balasubramanian; R. J. Pardikar; K. V. Rajkumar; T. Jayakumar; Baldev Raj

2004-01-01

406

Journal of Atmospheric and Solar-Terrestrial Physics 67 (2005) 11711177 Modelling high-power large-aperture radar meteor trails  

E-print Network

-aperture radar meteor trails Lars P. Dyrud�, Licia Ray, Meers Oppenheim, Sigrid Close, Kelly Denney Center see high-power large-aperture (HPLA) radar observations of meteor phenomena called head echoes and non demonstrating that meteor trails are unstable to growth of Farley­Buneman gradient-drift (FBGD) waves

Oppenheim, Meers

407

Estimating Radar Cross Section using Bayesian Image Restoration Richard O. Lane  

E-print Network

Estimating Radar Cross Section using Bayesian Image Restoration Richard O. Lane QinetiQ Malvern-dimensional radar cross section (RCS) of a vehicle given a radar image of the vehicle. A Markov chain Monte Carlo, the method may be applied to any type of radar image such as those produced by a synthetic aperture radar

Haddadi, Hamed

408

Researches of a new kind of advanced meter wave radar  

Microsoft Academic Search

Synthetic impulse and aperture radar (SIAR) is new kind of advanced meter wave radar. Stealth techniques and anti-radiation missiles (ARM) raise challenges to military radar. Many research results show that meter (or much longer) wavelength electromagnetic waves are the right way against the stealth technique and ARMs. However, traditional meter wave radar has many disadvantages, such as poor angle resolution,

Wu Jianqi; Jiang Kai; He Ruilong; Chen Boxiao

2001-01-01

409

A Novel Modified Omega-K Algorithm for Synthetic Aperture Imaging Lidar through the Atmosphere  

PubMed Central

The spatial resolution of a conventional imaging lidar system is constrained by the diffraction limit of the telescope's aperture. The combination of the lidar and synthetic aperture (SA) processing techniques may overcome the diffraction limit and pave the way for a higher resolution air borne or space borne remote sensor. Regarding the lidar transmitting frequency modulation continuous-wave (FMCW) signal, the motion during the transmission of a sweep and the reception of the corresponding echo were expected to be one of the major problems. The given modified Omega-K algorithm takes the continuous motion into account, which can compensate for the Doppler shift induced by the continuous motion efficiently and azimuth ambiguity for the low pulse recurrence frequency limited by the tunable laser. And then, simulation of Phase Screen (PS) distorted by atmospheric turbulence following the von Karman spectrum by using Fourier Transform is implemented in order to simulate turbulence. Finally, the computer simulation shows the validity of the modified algorithm and if in the turbulence the synthetic aperture length does not exceed the similar coherence length of the atmosphere for SAIL, we can ignore the effect of the turbulence.

Guo, Liang; Xing, Mendao; Tang, Yu; Dan, Jing

2008-01-01

410

Partially coherent illumination in full-field interferometric synthetic aperture microscopy  

PubMed Central

A model is developed for optical coherence tomography and interferometric synthetic aperture microscopy (ISAM) systems employing full-field frequency-scanned illumination with partial spatial coherence. This model is used to derive efficient ISAM inverse scattering algorithms that give diffraction-limited resolution in regions typically regarded as out of focus. Partial spatial coherence of the source is shown to have the advantage of mitigating multiple-scattering effects that can otherwise produce significant artifacts in full-field coherent imaging. PMID:19183692

Marks, Daniel L.; Davis, Brynmor J.; Boppart, Stephen A.; Carney, P. Scott

2010-01-01

411

A parametric study of various synthetic aperture telescope configurations for coherent imaging applications  

NASA Technical Reports Server (NTRS)

The comparative advantages of synthetic aperture telescopes (SATs) of segmented primary mirror and common secondary mirror type, on the one hand, and on the other those employing an array of independent telescopes, are discussed. The diffraction-limited optical performance of both redundant and nonredundant subaperture configurations are compared in terms of point spread function characteristics and encircled energy plots. Coherent imaging with afocal telescope SATs involves a pupil-mapping operation followed by a Fourier transform one. A quantitative analysis of the off-axis optical performance degradation due to pupil-mapping errors is presented, together with the field-dependent effects of residual design aberrations of independent telescopes.

Harvey, James E.; Wissinger, Alan B.; Bunner, Alan N.

1986-01-01

412

Bistatic and Multistatic Radar: Surveillance, Countermeasures, and Radar Cross Sections. (Latest Citations from the Aerospace Database)  

NASA Technical Reports Server (NTRS)

The bibliography contains citations concerning the design, development, testing, and evaluation of bistatic and multistatic radar used in surveillance and countermeasure technology. Citations discuss radar cross sections, target recognition and characteristics, ghost recognition, motion image compensation, and wavelet analysis. Stealth aircraft design, stealth target tracking, synthetic aperture radar, and space applications are examined.

1997-01-01

413

Bistatic and Multistatic Radar: Surveillance, Countermeasures, and Radar Cross Sections. (Latest citations from the Aerospace Database)  

NASA Technical Reports Server (NTRS)

The bibliography contains citations concerning the design, development, testing, and evaluation of bistatic and multistatic radar used in surveillance and countermeasure technology. Citations discuss radar cross sections, target recognition and characteristics, ghost recognition, motion image compensation, and wavelet analysis. Stealth aircraft design, stealth target tracking, synthetic aperture radar, and space applications are examined.

1998-01-01

414

Sound Field Directivity Correction in Synthetic Aperture Algorithm for Medical Ultrasound  

NASA Astrophysics Data System (ADS)

The paper presents modified multi-element synthetic transmit aperture (MSTA) method for ultrasound imaging with RF echoes correction taking into account the influence of the element directivity, which property becomes significant as the element width becomes commensurable with the wavelength corresponding to the nominal frequency of the transmit signal. The angular dependence of the radiation efficiency of the transmit-receive aperture is approximated by a far-field radiation pattern resulting from the exact solution of the corresponding mixed boundary-value problem for periodic baffle system. The directivity is calculated at the nominal frequency of the excitation signal and is incorporated into the conventional MSTA algorithm. Numerical experiments performed in MATLAB® environment using data simulated by FIELD II program as well as measurement data acquired using the Ultrasonix SonixTOUCH Research system are shown. The comparison of the results obtain by the modified and conventional MSTA methods is given which reveals significant improvement of the image quality, especially in the area neighboring to the transducer's aperture, and increase of the visualization depth at the same time.

Tasinkevych, Yuriy; Klimonda, Ziemowit; Lewandowski, Marcin; Nowicki, Andrzej

415

Decorrelation in interferometric radar echoes  

Microsoft Academic Search

A radar interferometric technique for topographic mapping of surfaces, implemented utilizing a single synthetic aperture radar (SAR) system in a nearly repeating orbit, is discussed. The authors characterize the various sources contributing to the echo correlation statistics, and isolate the term which most closely describes surficial change. They then examine the application of this approach to topographic mapping of vegetated

Howard A. Zebker; John Villasensor

1992-01-01

416

Simulation study of real time 3D synthetic aperture sequential beamforming for ultrasound imaging  

NASA Astrophysics Data System (ADS)

This paper presents a new beamforming method for real-time three-dimensional (3-D) ultrasound imaging using a 2-D matrix transducer. To obtain images with sufficient resolution and contrast, several thousand elements are needed. The proposed method reduces the required channel count from the transducer to the main imaging system, by including electronics in the transducer handle. The reduction of element channel count is achieved using a sequential beamforming scheme. The beamforming scheme is a combination of a fixed focus beamformer in the transducer and a second dynamic focus beamformer in the main system. The real-time imaging capability is achieved using a synthetic aperture beamforming technique, utilizing the transmit events to generate a set of virtual elements that in combination can generate an image. The two core capabilities in combination is named Synthetic Aperture Sequential Beamforming (SASB). Simulations are performed to evaluate the image quality of the presented method in comparison to Parallel beamforming utilizing 16 receive beamformers. As indicators for image quality the detail resolution and Cystic resolution are determined for a set of scatterers at a depth of 90mm for elevation and azimuth angles from 0° to 25°. Simulations show that the acoustic performance of the Proposed method is less angle dependent than Parallel beamforming. The Cystic resolution is shown to be more than 50% improved, with a detail resolution on the same order as Parallel Beamforming.

Hemmsen, Martin Christian; Rasmussen, Morten Fischer; Stuart, Matthias Bo; Jensen, Jørgen Arendt

2014-03-01

417

GeoSTAR: a synthetic aperture microwave sounder for geostationary missions  

NASA Astrophysics Data System (ADS)

The Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR) is a new microwave atmospheric sounder under development. It will bring capabilities similar to those now available on low-earth orbiting environmental satellites to geostationary orbit - where such capabilities have not been available. GeoSTAR will synthesize the multi-meter aperture needed to achieve the required spatial resolution, which will overcome the obstacle that has prevented a GEO microwave sounder from being implemented until now. The synthetic aperture approach has until recently not been feasible, due to the high power needed to operate the on-board high-speed massively parallel processing system required for 2D-synthesis, as well as a number of system and calibration obstacles. The development effort under way at JPL, with important contributions from the Goddard Space Flight Center and the University of Michigan, is intended to demonstrate the measurement concept and retire much of the technology risk. To that purpose a small ground based demo version of GeoSTAR is being constructed, which will be used to characterize system performance and test various calibration methods. This prototype development, which is being sponsored by NASA through its Instrument Incubator Program, will be completed in 2005. A GeoSTAR space mission can then be initiated. In parallel with the technology development, mission architecture studies are also under way in collaboration with the NOAA Office of System Development. In particular, the feasibility of incorporating GeoSTAR on the next generation of the geostationary weather satellites, GOES-R, is being closely examined. That would fill a long standing gap in the national weather monitoring capabilities.

Lambrigtsen, Bjorn H.; Wilson, William J.; Tanner, Alan B.; Kangaslahti, Pekka

2005-01-01

418

Synthetic aperture microwave imaging with active probing for fusion plasma diagnostics  

NASA Astrophysics Data System (ADS)

A Synthetic Aperture Microwave Imaging (SAMI) system has been designed and built to obtain 2-D images at several frequencies from fusion plasmas. SAMI uses a phased array of linearly polarised antennas. The array configuration has been optimised to achieve maximum synthetic aperture beam efficiency. The signals received by antennas are down-converted to the intermediate frequency range and then recorded in a full vector form. Full vector signals allow beam focusing and image reconstruction in both real time and a post-processing mode. SAMI can scan over 16 pre-programmed frequencies in the range of 10-35GHz with a switching time of 300ns. The system operates in 2 different modes simultaneously: both a 'passive' imaging of plasma emission and also an 'active' imaging of the back-scattered signal of the radiation launched by one of the antennas from the same array. This second mode is similar to so-called Doppler backscattering (DBS) reflectometry with 2-D resolution of the propagation velocity of turbulent structures. Both modes of operation show good performance in fusion plasma experiments on Mega Amp Spherical Tokamak (MAST). We have obtained the first ever 2-D images of BXO mode conversion windows. With active probing, first ever turbulence velocity maps have been obtained. We present an overview of the diagnostic and discuss recent results. In contrast to quasi-optical microwave imaging systems SAMI requires neither big aperture viewing ports nor large 2-D detector arrays to achieve the desired imaging resolution. The number of effective 'pixels' of the synthesized image is proportional to the number of receiving antennas squared. Thus only a small number of optimised antennas is sufficient for the majority of applications. Possible implementation of SAMI on ITERand DEMO is discussed.

Shevchenko, Vladimir F.; Freethy, Simon J.; Huang, Billy K.; Vann, Roddy G. L.

2014-08-01

419

A large-angle high speed scanner based on electro-optic crystal for Fresnel telescope synthetic aperture imaging ladar  

NASA Astrophysics Data System (ADS)

The cross-orbit scanning is very important for Fresnel telescope synthetic aperture imaging ladar system. This paper presents a design of large-angle high speed scanner based on electro-optic crystal for the cross-orbit scanning in Fresnel telescope synthetic aperture imaging ladar system. The designed scanner is based on the space-charge-controlled EO effect in KTN. In the experiment the crystal temperature should be kept a little higher above Tc to obtain a large EO effect and the polarization of the laser beam should be parallel to the direction of the driving electric field. Compared with other conventional EO crystal scanner, the new scanner can greatly improve the scanner angle by several times when maintains high speed and accuracy, which will have a great potential for cross-orbit scanning applications in Fresnel telescope synthetic aperture imaging ladar system.

Xu, Jun; Zhi, Ya'nan; Wang, Xuping; Sun, Jianfeng; Zhou, Yu; Dai, Enwen; Liu, Liren

2012-10-01

420

HI-CLASS on AEOS: a large-aperture laser radar for space surveillance\\/situational awareness investigations  

Microsoft Academic Search

The Air Force Research Laboratory\\/Directed Energy Directorate (AFRL\\/DE) via the ALVA (Applications of Lidars for Vehicles with Analysis) program installed in late 2000 a wideband, 12 J 15 Hz CO2 laser radar (ladar) on the 3.67 meter aperture AEOS (Advanced Electro-Optics System) telescope. This system is part of the Maui Space Surveillance System (MSSS), on the summit of Haleakala, Maui,

Mark A. Kovacs; Gordon L. Dryden; Richard H. Pohle; Kirstie Ayers; Richard A. Carreras; Linda L. Crawford; Russell Taft

2001-01-01

421

Ultrasound research scanner for real-time synthetic aperture data acquisition.  

PubMed

Conventional ultrasound systems acquire ultrasound data sequentially one image line at a time. The architecture of these systems is therefore also sequential in nature and processes most of the data in a sequential pipeline. This often makes it difficult to implement radically different imaging strategies on the platforms and makes the scanners less accessible for research purposes. A system designed for imaging research flexibility is the prime concern. The possibility of sending out arbitrary signals and the storage of data from all transducer elements for 5 to 10 seconds allows clinical evaluation of synthetic aperture and 3D imaging. This paper describes a real-time system specifically designed for research purposes. The system can acquire multichannel data in real-time from multi-element ultrasound transducers, and can perform some real-time processing on the acquired data. The system is capable of performing real-time beamforming for conventional imaging methods using linear, phased, and convex arrays. Image acquisition modes can be intermixed, and this makes it possible to perform initial trials in a clinical environment with new imaging modalities for synthetic aperture imaging, 2D and 3D B-mode, and velocity imaging using advanced coded emissions. The system can be used with 128-element transducers and can excite 128 transducer elements and receive and sample data from 64 channels simultaneously at 40 MHz with 12-bit precision. Two-to-one multiplexing in receive can be used to cover 128 receive channels. Data can be beamformed in real time using the system's 80 signal processing units, or it can be stored directly in RAM. The system has 16 Gbytes RAM and can, thus, store more than 3.4 seconds of multichannel data. It is fully software programmable and its signal processing units can also be reconfigured under software control. The control of the system is done over a 100-Mbits/s Ethernet using C and Matlab. Programs for doing, e.g., B-mode imaging can be written directly in Matlab and executed on the system over the net from any workstation running Matlab. The overall system concept is presented along with its implementation and examples of B-mode and in vivo synthetic aperture flow imaging. PMID:16048189

Jensen, Jørgen Arendt; Holm, Ole; Jensen, Lars Joost; Bendsen, Henrik; Nikolov, Svetoslav Ivanov; Tomov, Borislav Gueorguiev; Munk, Peter; Hansen, Martin; Salomonsen, Kent; Hansen, Johnny; Gormsen, Kim; Pedersen, Henrik Møller; Gammelmark, Kim L

2005-05-01

422

Use of C-Band Ground Penetrating Radar to Determine Backscatter Sources Within Glaciers  

Microsoft Academic Search

The question of penetration of synthetic aperture radar (SAR) signals at C-band frequency into polar glaciers is addressed by comparing ground penetrating radar (GPR) and SAR backscatter signatures. Profiles of the Kongsvegen glacier, Svalbard, were obtained with a C-band GPR. The received signal is converted to the equivalent radar cross section using the standard radar equation, thus mapping the effective

Kirsty Langley; Svein-Erik Hamran; Kjell Arild Hogda; Rune Storvold; Ola Brandt; Jon Ove Hagen; Jack Kohler

2007-01-01

423

RADAR REMOTE SENSINGOF GREAT LAKES ICE COVER G. A. Leshkevich'andS.V. Nghiem2  

E-print Network

RADAR REMOTE SENSINGOF GREAT LAKES ICE COVER G. A. Leshkevich'andS.V. Nghiem2 `Great Lakes cover uses various classes of radars including scatterometer, polarimetric Synthetic Aperture Radar (SAR), and interferometric SAR. Applications of radar mapping of Great Lakes ice cover includes marine resource management

424

Fast nearfield to farfield conversion algorithm for circular synthetic aperture sonar.  

PubMed

Monostatic circular synthetic aperture sonar (CSAS) images are formed by processing azimuthal angle dependent backscattering from a target at a fixed distance from a collocated source/receiver. Typical CSAS imaging algorithms [Ferguson and Wyber, J. Acoust. Soc. Am. 117, 2915-2928 (2005)] assume scattering data are taken in the farfield. Experimental constraints may make farfield measurements impractical and thus require objects to be scanned in the nearfield. Left uncorrected this results in distortions of the target image and in the angular dependence of features. A fast approximate Hankel function based algorithm is presented to convert nearfield data to the farfield. Images and spectrograms of an extended target are compared for both cases. PMID:25096147

Plotnick, Daniel S; Marston, Philip L; Marston, Timothy M

2014-08-01

425

Synthetic Aperture Focusing Technique for the Ultrasonic Evaluation of Friction Stir Welds  

NASA Astrophysics Data System (ADS)

An ultrasonic technique using numerical focusing and processing is presented in this paper for the detection of different types of flaws in friction stir welds (FSW). The data is acquired using immersion ultrasonic technique or laser ultrasonics, while the Synthetic Aperture Focusing Technique (SAFT) is used for numerical focusing. Measurements on the top and far sides of the weld for both lap and butt joints of thin aluminum sheets are investigated. Discontinuities such as wormholes, hooking, lack of penetration and voids are found to be easily detected. The limit of detectability and a comparison with mechanical properties are discussed. Also, the detection of joint line remnants or kissing bonds due to entrapped oxide layers seems possible in lap joint structures using high frequency laser-ultrasonics.

Lévesque, D.; Dubourg, L.; Mandache, C.; Kruger, S. E.; Lord, M.; Merati, A.; Jahazi, M.; Monchalin, J.-P.

2008-02-01

426

Speckle effect in a down-looking synthetic aperture imaging ladar  

NASA Astrophysics Data System (ADS)

Down-looking synthetic aperture imaging ladar(SAIL) has overcome many difficulties in side-looking SAIL. However, it is inevitably impacted by the speckle effect. There is temporally varying speckle effect due to the angular deflecting of two coaxial polarization-orthogonal beams transmitted in the orthogonal direction of travel, and a spatial varying speckle effect in the travel direction. Under the coaxial heterodyne, phase variations caused by speckle effect are compensated, leaving the amplitude variations of speckle field. In this paper, the speckle effect in the down-looking SAIL is analyzed, expressions for two-dimensional data collection contained speckle effect are obtained and the two-dimensional image influenced by speckle effect is simulated.

Xu, Qian; Zhou, Yu; Sun, Jianfeng; Lu, Zhiyong; Sun, Zhiwei; Liu, Liren

2014-09-01

427

Prototype development of a Geostationary Synthetic Thinned Aperture Radiometer (GeoSTAR)  

NASA Technical Reports Server (NTRS)

Weather prediction and hurricane tracking would greatly benefit of a continuous imaging capability of a hemisphere at millimeter wave frequencies. We are developing a synthetic thinned aperture radiometer (STAR) prototype operating from 50 to 56 GHz as a ground-based testbed to demonstrate the technologies needed to do full earth disk atmospheric temperature soundings from Geostationary orbit with very high spatial resolution. The prototype consists of a Y-array of 24 MMIC receivers that are compact units implemented with low noise InP MMIC LNAs, second harmonic I-Q mixers, low power IF amplifiers and include internal digital bias control with serial line communication to enable low cost testing and system integration. Further