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1

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

2

Ship signatures in synthetic aperture radar imagery  

Microsoft Academic Search

Ship signatures in synthetic aperture radar (SAR) imagery have been matched to Automatic Identification System (AIS) data to yield a large database of known ships for ship signature analysis. This paper focuses on ship radar cross section and ship length derived from the ship signature length. Cross- polarization is an attractive option for ship detection.

Paris W. Vachon; Ryan A. English; John Wolfe

2007-01-01

3

Orbit determination using synthetic aperture radar  

Microsoft Academic Search

The use of synthetic aperture radar (SAR) images to estimate orbital parameters is studied. The SAR image formation process which requires the ability to repeatedly transmit identical signals and accurately sense the return echoes from a region of terrain is described. The orbit determination capabilities of the SAR system's observables are investigated. Five SAR observations were collected from a simulated

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

1986-01-01

4

Low-cost airborne synthetic aperture radar  

Microsoft Academic Search

This paper describes the rudiments of a design and implementation approach that will produce low-cost and quick turnaround airborne synthetic aperture radar (SAR) systems including designs for remotely piloted vehicles (RPVs). The concept is based on strict adherence to a discipline of simplicity in application boundary definition, the corresponding design that follows, extension of this core of simplicity through the

Samuel W. McCandless; Barton D. Huxtable; Christopher R. Jackson

1997-01-01

5

Adaptive synthetic aperture radar image enhancement  

Microsoft Academic Search

An adaptive SAR image enhancement method is presented for reducing the speckle noise and increasing the contrast of synthetic aperture radar (SAR) images. First, a fuzzy logic based filter, employing fuzzy edge to weight the contributions of pixel values in filter window, is used to filter the speckles. Second, the original SAR image is decomposed into lowfrequency component and high-frequency

Hua Cheng; Jinwen Tian

2009-01-01

6

Synthetic aperture radar identification based on information fusion  

Microsoft Academic Search

In this paper, a novel method based on data fusion for identifying synthetic aperture radar is introduced. Basic probability assignment function obtaining of D-S evidence theory is a difficult problem. The method of obtaining BPAF based on feature parameters resemble is proposed. The synthetic aperture radar identification fusion model based on obtaining BPAF method is constructed and synthetic aperture radar

Li Nan; Qu Changwen; Su Feng; Ping Dianfa

2009-01-01

7

Use of Synthetic Aperture Radar in Cold Climate Flood Response  

Microsoft Academic Search

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

L. D. Yarbrough

2009-01-01

8

IMAGE DOMAIN SCATTERING CENTER MODELS FOR SYNTHETIC APERTURE RADAR  

E-print Network

IMAGE DOMAIN SCATTERING CENTER MODELS FOR SYNTHETIC APERTURE RADAR Michael J. Gerry, Lee C. Potter-made objects from synthetic aperture radar SAR measurements. The model is developed for high frequency for describing high fre- quency synthetic aperture radar measurements of ob- jects. The model is based

Moses, Randolph L.

9

Analysis of synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

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

Blanchard, B. J.

1977-01-01

10

Wind energy mapping from synthetic aperture radar  

Microsoft Academic Search

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

Ola M. Johannessen; Heidi Espedal; E. Bjorgo

1999-01-01

11

Addressing Three Fallacies About Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

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

Atwood, Don; Garron, Jessica

2013-12-01

12

Recent Trend of the Synthetic Aperture Radar  

Microsoft Academic Search

The Synthetic Aperture Radar (SAR) is expected to use various application for monitoring ground terrain. In 1990s, some space-borne SARs had been launched and showed their validity. These space-borne SARs had been functioned with single band and single polarization of about 30m resolution. On the other hand, airborne SAR and shuttle-borne SARs have conducted the advanced technologies, such as Interferometry

Seiho Uratsuka

2003-01-01

13

Soviet oceanographic synthetic aperture radar (SAR) research  

SciTech Connect

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

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

1991-01-01

14

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

Microsoft Academic Search

ERS-1\\/ERS-2 synthetic aperture radar interferometry was used to study the 1997 eruption of Okmok volcano in Alaska. First, we derived an accurate digital elevation model (DEM) using a tandem ERS-1\\/ERS-2 image pair and the preexisting DEM. Second, by studying changes in interferometric coherence we found that the newly erupted lava lost radar coherence for 5-17 months after the eruption. This

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

2000-01-01

15

Synthetic aperture radar processing with tiered subapertures  

SciTech Connect

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

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

1994-06-01

16

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

17

MEASUREMENT OF SOIL MOISTURE WITH SYNTHETIC APERTURE RADAR1  

E-print Network

MEASUREMENT OF SOIL MOISTURE WITH SYNTHETIC APERTURE RADAR1 J. P. Kerekes and S. C. Crocker Lincoln the use of Synthetic Aperture Radar (SAR) data in the measurement of soil moisture content in small area of soil moisture contentover small areas at various subsurface depths and under three surface cover

Kerekes, John

18

Segmentation of polarimetric synthetic aperture radar data.  

PubMed

A statistical image model is proposed for segmenting polarimetric synthetic aperture radar (SAR) data into regions of homogeneous and similar polarimetric backscatter characteristics. A model for the conditional distribution of the polarimetric complex data is combined with a Markov random field representation for the distribution of the region labels to obtain the posterior distribution. Optimal region labeling of the data is then defined as maximizing the posterior distribution of the region labels given the polarimetric SAR complex data (maximum a posteriori (MAP) estimate). Two procedures for selecting the characteristics of the regions are then discussed. Results using real multilook polarimetric SAR complex data are given to illustrate the potential of the two selection procedures and evaluate the performance of the MAP segmentation technique. It is also shown that dual polarization SAR data can yield segmentation resultS similar to those obtained with fully polarimetric SAR data. PMID:18296163

Rignot, E; Chellappa, R

1992-01-01

19

Multi-static synthetic aperture radar and inverse scattering  

Microsoft Academic Search

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

Mats Gustafsson

2003-01-01

20

Automated registration of synthetic aperture radar imagery to LIDAR  

Microsoft Academic Search

The registration of synthetic aperture radar imagery to other images is difficult, especially in mountainous terrain. We introduce a new approach to this problem that registers radar images to digital elevation models derived from LIDAR. The algorithm generates a predicted image from the elevation model using the radar geometry and then registers the predicted image to the radar image with

Mark D. Pritt; Kevin J. LaTourette

2011-01-01

21

Spaceborne Synthetic Aperture Radar for Oceanography  

NASA Astrophysics Data System (ADS)

The book originates from a symposium held at the Applied Physics Laboratory of the Johns Hopkins University in March 1980. The purpose of the symposium was to review the results to date of investigations related to the SEASAT SAR (synthetic aperture radar) experiment and, to quote from the book's foreword, ‘to explore the potential’ of such satellite-borne imaging radars for oceanography. The book contains 13 papers; these are grouped into chapters according to the various phenomena sensed by the SAR; namely, winds (or surface stress), waves, and circulation patterns. The book is held together by an introduction to SAR principles and the SEASAT mission (by Beal) and concludes with a panel discussion and a collection of SAR imagery obtained over the western North Atlantic during the abbreviated lifetime of the SEASAT mission (June—October 1978). (This imagery, composited from four optically processed 25 km subswaths, comes as a bit of a disappointment after the 40-km square digitally processed images that grace as frontispieces the several chapters of the volume).

Jackson, F. C.

22

Synthetic aperture radar imaging exploiting multiple scattering  

NASA Astrophysics Data System (ADS)

In this paper, we consider an imaging scenario, where a bi-static synthetic aperture radar (SAR) system is used in a multiple scattering environment. We consider a ray-theoretic approximation to the Green function to model a multiple scattering environment. This allows us to incorporate the multiple paths followed by the transmitted signal, thereby providing different views of the object to be imaged. However, the received signal from the multiple paths and additive thermal noise may interfere and produce artifacts when standard backprojection-based reconstruction algorithms are used. We use microlocal analysis in a statistical setting to develop a novel filtered-backprojection type image reconstruction method that not only exploits the multi-paths leading to enhancement of the reconstructed image but also suppresses the artifacts due to interference. We assume a priori knowledge of the second-order statistics of the target and noise to suppress the artifacts due to interference in a mean-square error sense. We present numerical simulations to demonstrate the performance of our image reconstruction method. While the focus of this paper is on radar applications, our image formation method is also applicable to other problems arising in fields such as acoustic, geophysical and medical imaging.

Krishnan, V.; Yazici, B.

2011-05-01

23

A system model and inversion for synthetic aperture radar imaging  

Microsoft Academic Search

A system model and its corresponding inversion for synthetic aperture radar imaging are presented. The system model incorporates the spherical nature of a radar's radiation pattern at far field. The inverse method based on this model integrates the recorded signals at various coordinates of a translational radar (linear array) via a spatial Fourier transform. The transformed data are shown to

M. Soumekh

1990-01-01

24

Peak stability derived from phase history in synthetic aperture radar  

Microsoft Academic Search

The stability of bright peaks over the complex phase history of synthetic aperture radar (SAR) imagery is examined using a 'sub-aperture imaging' approach. The additional information obtained about the peaks can be applied to the following areas: improved peak matching in the automatic target recognition (ATR) problem; false-alarm determination; and identification of imaging artifacts, such as the sidelobes of bright

Warren E. Smith; Theodore Irons; Jay Riordan; Steven Sayre

1999-01-01

25

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

26

Synthetic-aperture radar imaging through dispersive media  

Microsoft Academic Search

In this paper we develop a method for synthetic-aperture radar (SAR) imaging through a dispersive medium. We consider the case when the sensor and scatterers are embedded in a known homogeneous dispersive material, the scene to be imaged lies on a known surface and the radar antenna flight path is an arbitrary but known smooth curve. The scattering is modeled

Trond Varslot; J. Héctor Morales; Margaret Cheney

2010-01-01

27

Reconnaissance with ultra wideband UHF synthetic aperture radar  

Microsoft Academic Search

The author addresses the problem of detecting and identifying stationary and moving targets with foliage penetrating UHF synthetic aperture radar (SAR). The role of a target's coherent SAR signature, which varies with the radar's frequency and aspect angle, in forming the Fourier space of the SAR signal is analyzed. The resultant relationship is the basis of an algorithm which, after

MEHRDAD SOUMEKH

1995-01-01

28

Parametric scattering models for bistatic synthetic aperture radar  

Microsoft Academic Search

Parametric scattering center models match to radar scene attributes, aiding in automatic target recognition (ATR) and scene visualization. In this paper, we develop parametric models of canonical shapes for bistatic synthetic aperture radar (SAR).We generalize geometric theory of diffraction solutions for scattering mechanisms in a plane to develop three-dimensional models for six canonical shapes: a rectangular plate, dihedral, trihedral, cylinder,

Julie Ann Jackson; Brian D. Rigling; Randolph L. Moses

2008-01-01

29

Imaging procedures for the inverse synthetic aperture radar application  

Microsoft Academic Search

The paper discusses the approaches used in the algorithm design of radar image processing. They are based on parametric and non-parametric spectral analysis and compared to each other using well-known example of simulated data for the inverse synthetic aperture radar application. The goal of the processing is meeting two requirements which are reducing smeared Doppler shifts and improving image resolution.

Maxim Konovalyuk; Yury Kuznetsov; Andrey Baev

2011-01-01

30

A parametric model for synthetic aperture radar measurements  

Microsoft Academic Search

We present a parametric model for radar scattering as a function of frequency and aspect angle. The model is used for analysis of synthetic aperture radar measurements. The estimated parameters provide a concise, physically relevant description of measured scattering for use in target recognition, data compression and scattering studies. The scattering model and an image domain estimation algorithm are applied

Michael J. Gerry; Lee C. Potter; Inder J. Gupta; Andria van der Merwe

1999-01-01

31

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

32

An archaeological application of synthetic aperture radar (SAR) in Thailand  

Microsoft Academic Search

An archaeological site has been identified in Northeastern Thailand using airborne Synthetic Aperture Radar (SAR). The site consists of a pair of concentric ancient moats or canals which once surrounded an ancient town called “Muang Ham Hork”; near Ban Rai, Tambol Ban Khwao, Amphoe Ban Khwao, Changwat Chaiyaphum. The site enclosed by the moat is approximately, 1.6km in diameter. It

1995-01-01

33

SARAS: a synthetic aperture radar (SAR) raw signal simulator  

Microsoft Academic Search

An SAR simulator of an extended three-dimensional scene is presented. It is based on a facet model for the scene, asymptotic evaluation of SAR unit response, and a two-dimensional fast Fourier transform code for the data processing. Prescribed statistics of the model account for a realistic speckle of the image. The simulator is implemented in Synthetic Aperture Radar Advance Simulators

Giorgio Franceschetti; Maurizio Migliaccio; Daniele Riccio; Gilda Schirinzi

1992-01-01

34

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

35

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

36

Imagery of ocean waves by synthetic aperture radar  

Microsoft Academic Search

We consider the image structure of ocean waves produced by a synthetic aperture radar (SAR). The theory takes account of the spatial and temporal dependence of small scale capillary waves and large scale waves. Detailed discussions are given to the imaging process in which both amplitude modulation and velocity bunching contribute to the final images. Discussions are also presented on

K. Ouchi

1982-01-01

37

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

38

Multifrequency polarimetric synthetic aperture radar observations of sea ice  

Microsoft Academic Search

The first known full polarimetric airborne synthetic aperture radar (SAR) data set of sea ice is introduced. Images were acquired in the Beaufort, Bering and Chukchi seas in March 1988, during a campaign for validation of Defense Meterological Satellite Program Special Sensor Microwave Imager radiometer ice products. Statistics of the magnitude, phase and polarization of complex backscattered signals recorded by

Mark R. Drinkwater; R. Kwok; D. P. Winebrenner; E. Rignot

1991-01-01

39

Target detection accuracy improvement in synthetic aperture radar  

Microsoft Academic Search

This paper proposes a decision method to improve the target identification accuracy in a synthetic aperture radar processing algorithm. In the imaging algorithm, Fourier based processing algorithm is used to obtain the processed image from the measured 2D cartesian backscattered frequency domain data. In practical applications, the measured data is limited in frequency band and aspect angle interval and this

S. Kargin; M. Kartal; S. Kurnaz

2003-01-01

40

Support Vector Machines For Synthetic Aperture Radar Automatic Target Recognition  

Microsoft Academic Search

: Algorithms that produce classifiers with large margins, such as support vector machines (SVMs), AdaBoost, etc. are receiving more and more attention in the literature. This paper presents a real application of SVMs for synthetic aperture radar automatic target recognition (SAR\\/ATR) and compares the result with conventional classifiers. The SVMs are tested for classification both in closed and open sets

Qun Zhao; Jose C. Principe

41

Focusing bistatic synthetic aperture radar using dip move out  

Microsoft Academic Search

The appearance of new synthetic aperture radar (SAR) acquisition techniques based on opportunity sources enhances interest in bistatic geometries. In seismic data acquisition, each source is currently accompanied by up to 10 000 receivers, and in the last two decades, the bistatic geometry has been carefully studied by scores of authors. Rather then introducing new focusing techniques, within the first-order

D. D'Aria; A. Monti Guarnieri; F. Rocca

2004-01-01

42

Synthetic Aperture Radar Image Formation in Reconfigurable Logic  

Microsoft Academic Search

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

PETER A

2001-01-01

43

Nearshore circulation and synthetic aperture radar: an exploratory study  

Microsoft Academic Search

We use a sequence of synthetic aperture radar (SAR) images to map diÄ erences in theood and ebb tidal currents in a cove along the coast of Nova Scotia, Canada. The asymmetry in the tidalow determines theushing rate of the cove which, in turn, has a signi® cant e Ä ect on biological production within the cove and its potential

K. R. THOMPSON; D. E. KELLEY; D. STURLEY; B. TOPLISS; R. LEAL

1998-01-01

44

Measuring Synthetic Aperture Radar target differences with stochastic distances  

Microsoft Academic Search

Synthetic Aperture Radar (SAR) imagery plays a central role as a source of unique data for Geographic Information Systems. These data sets provide complementary information to that provided by optical and infra-red sensors as, for instance, Landsat TM, CBERS-2, IKONOS and SPOT, to name a few. SAR sensors capture information about the target roughness and its dielectric properties, and their

A. D. C. Nascimento; Renato J. Cintra; Alejandro C. Frery

2009-01-01

45

Synthetic Aperture Radar Autofocus Based on a Bilinear Model  

Microsoft Academic Search

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

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

2012-01-01

46

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

47

Speckle filtering of synthetic aperture radar images: A review  

Microsoft Academic Search

Speckle, appearing in synthetic aperture radar (SAR) images as granular noise, is due to the interference of waves reflected from many elementary scatterers. Speckle in SAR images complicates the image interpretation problem by reducing the effectiveness of image segmentation and classification. To alleviate deleterious effects of speckle, various ways have been devised to suppress it.This paper surveys several better?known speckle

J. S. Lee; L. Jurkevich; P. Dewaele; P. Wambacq; A. Oosterlinck

1994-01-01

48

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

49

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 University (BYU) µSAR, are made possible by using a linear frequency modulated continuous wave (LFM- CW as constant over a pulse, are limited for an LFM-CW SAR. In this paper, the LFM- CW SAR signal model

Long, David G.

50

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

51

Models for Synthetic Aperture Radar Image Analysis  

Microsoft Academic Search

Abstract: After reviewing some classical statistical hypothesis commonly used in imageprocessing and analysis, this paper presents some models that are useful in syntheticaperture radar (SAR) image analysis. The main focus is on how these models deviatefrom the classical ones, and on the impact these departures have on processing andanalysis techniques. The multiplicative model, an important tool for SAR data modelingand

Alejandro C. Frery; Antonio Correia; Camilo D. Renno; Corina Da C. Freitas; Julio Jacobo-berlles; Klaus L. P. Vasconcellos; Marta Mejail; Sidnei J. S. Sant'anna

1999-01-01

52

Materials identification synthetic aperture radar: progress toward a realized capability  

NASA Astrophysics Data System (ADS)

Most non-metallic materials have frequency-dependent reflectivity functions, that is, they reflect electromagnetic energy in a manner that depends on frequency. Pulsed-chirped synthetic aperture radar and other multispectral radar systems do not generally take into account the frequency dependence of material reflections in forming scenes or making other inferences. In this report, we introduce a simple mathematical approach to using existing pulsed chirp synthetic aperture systems in a manner which results in a determination of a frequency-dependent reflectivity function for each pixel in a computed scene. Our analysis of collected data suggests that the method may be useful to distinguish disturbed from non-disturbed earth, and to detect chemicals on the surface of the earth. The method we have developed provides the analyst with a vector above each pixel with each vector component referencing a frequency band. This additional information may be useful for considering surface texture, subsurface layering and materials identification.

Albanese, Richard A.; Medina, Richard L.

2013-05-01

53

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

54

Studies of multi-baseline spaceborne interferometric synthetic aperture radars  

NASA Technical Reports Server (NTRS)

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

Li, F.; Goldstein, R.

1987-01-01

55

Deformation monitoring using scanning synthetic aperture radar interferometry  

Microsoft Academic Search

This dissertation provides the first demonstration of scanning synthetic aperture radar (ScanSAR) advanced interferometry processing for measuring surface deformation. ScanSAR data are synthesized from ERS-1\\/2 stripmap SAR images over known deformation in Phoenix, Arizona. The strategy is to construct a burst pattern similar to Envisat ScanSAR data and to create a realistic variable-burst synchronization scenario in which any image pair

Krishna Vikas Gudipati

2009-01-01

56

Identification of airfield runways in synthetic aperture radar images  

Microsoft Academic Search

Synthetic aperture radar (SAR) is a microwave-based remote sensing technique whereby images can be captured when optical images cannot, at night or when there is cloud cover. However, its very low signal-to-noise ratio (1:1) means that conventional image analysis techniques are unsuitable for SAR imagery. This paper presents a novel approach to the detection of very small objects in SAR

I. Finch; A. Antonacopoulos

1998-01-01

57

Recognizing target variants and articulations in synthetic aperture radar images  

Microsoft Academic Search

The focus of this paper is recognizing articulated vehicles and actual vehicle configuration variants in real synthetic aperture radar (SAR) images. Using SAR scattering-center locations and magnitudes as features, the invariance of these features is shown with articulation (e.g., rotation of a tank turret), with configuration variants, and with a small change in depression angle. This scatterer-location and magnitude quasiinvariance

Bir Bhanu; Grinnell Jones

2000-01-01

58

Ionospheric effects on synthetic aperture radar at VHF  

SciTech Connect

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

Fitzgerald, T.J.

1997-02-01

59

Synthetic aperture radar range - Azimuth ambiguity design and constraints  

NASA Technical Reports Server (NTRS)

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

Mehlis, J. G.

1980-01-01

60

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

61

Sampling effects in square-law detected synthetic aperture radar  

NASA Astrophysics Data System (ADS)

It was demonstrated by Sakar et al. (1984) that a narrow synthetic radar beam may be generated from square-law detected radar pulses provided that the return pulse is incoherent. This technique reduces the required knowledge of platform location to a fraction of the transmitted pulse length, rather than the fraction of the carrier wavelength required by a coherent SAR. The effect of sampling the aperture is described here. It is shown that the sampling interval required to avoid unacceptable sidelobe levels can be very much greater than that required by coherent SAR.

Wingham, D. J.

1988-05-01

62

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

63

Interferometric synthetic aperture radar imagery of the Gulf Stream  

NASA Technical Reports Server (NTRS)

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

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

1993-01-01

64

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

65

Low-Cost, High Resolution X-Band Laboratory Radar System for Synthetic Aperture Radar Applications  

Microsoft Academic Search

Entry into the field of radar cross section measurements or synthetic aperture radar (SAR) algorithm development is often difficult due to the cost of high-end precision pulsed IF or other precision radar test instruments. A low-cost entry-level alternative was developed in order to provide an intermediate step between high-end high precision radar systems and ad-hoc spare parts systems. The system

Gregory L. Charvat; L. C. Kempel

2006-01-01

66

Application of synthetic aperture radar remote sensing in Antarctica  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

67

Beaconless search and rescue using polarimetric synthetic aperture radar  

NASA Astrophysics Data System (ADS)

In developing a beaconless search and rescue capability to quickly locate small aircraft that have crashed in remote areas, NASA's Search and Rescue (S&R) Program brings together advanced polarimetric synthetic aperture radar processing, field and laboratory tests, and state-of-the-art automated target detection algorithms. This paper provides the status of this program, which began with experiments conducted in concert with the JPL DC-8 AirSAR in 1989 at the Duke University Forest. The program is being conducted by NASA's Goddard Space Flight Center (GSFC) under the auspices of the Search and Rescue Office.

McCandless, Samuel W.; Huxtable, Barton D.; Mansfield, Arthur W.; Wallace, Ronald; Larsen, Rudolph; Rais, Houra

1996-03-01

68

Maximum likelihood classification of synthetic aperture radar imagery  

NASA Technical Reports Server (NTRS)

Classification of synthetic aperture radar (SAR) images has important applications in geology, agriculture, and the military. A statistical model for SAR images is reviewed and a maximum likelihood classification algorithm developed for the classification of agricultural fields based on the model. It is first assumed that the target feature information is known a priori. The performance of the algorithm is then evaluated in terms of the probability of incorrect classification. A technique is also presented to extract the needed feature information from a SAR image; then both the feature extraction and the maximum likelihood classification algorithms are tested on a SEASAT-A SAR image.

Frost, V. S.; Yurovsky, L. S.

1985-01-01

69

SEASAT views oceans and sea ice with synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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

Fu, L. L.; Holt, B.

1982-01-01

70

Two target height effects on interferometric synthetic aperture radar coherence  

SciTech Connect

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

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

2000-03-07

71

YSAR: a compact low-cost synthetic aperture radar  

NASA Astrophysics Data System (ADS)

The Brigham Young University Synthetic Aperture Radar (YSAR) is a compact, inexpensive SAR system which can be flown on a small aircraft. The system has exhibited a resolution of approximately 0.8 m by 0.8 m in test flights in calm conditions. YSAR has been used to collect data over archeological sites in Israel. Using a relatively low frequency (2.1 GHz), we hope to be able to identify walls or other archeological features to assist in excavation. A large data set of radar and photographic data have been collected over sites at Tel Safi, Qumran, Tel Micnah, and the Zippori National Forest in Israel. We show sample images from the archeological data. We are currently working on improved autofocus algorithms for this data and are developing a small, low-cost interferometric SAR system (YINSAR) for operation from a small aircraft.

Thompson, Douglas G.; Arnold, David V.; Long, David G.; Miner, Gayle F.; Karlinsey, Thomas W.; Robertson, Adam E.

1997-09-01

72

The Radarsat synthetic aperture radar: Early hardware development  

NASA Astrophysics Data System (ADS)

Since the beginning of 1990, the contract to Spar Aerospace for the Radarsat project has been signed, and the work leading up to launch has begun. The synthetic aperture radar (SAR) system has been designed to be much more versatile in its operations than other preceding satellite SAR systems. Necessarily, certain additional capabilities are required of some of the components and subsystems which make up the instrument. Wherever possible, however, established technologies and designs have been adopted in order to reduce risk and development cost. This paper reviews the new requirements which arise from the Radarsat design and outlines the current status of the hardware developments. This review covers all segments of the Radarsat SAR system, including telecommand and data links, on-board computer and recorders, the ground processor, as well as the subsystems of the radar instrument itself. The major anticipated developments in the building of hardware breadboards and in the preliminary design review are identified.

Luscombe, Anthony P.; Ferguson, Ian D.

1990-07-01

73

Precipitation mapping with an airborne synthetic aperture imaging radar  

NASA Technical Reports Server (NTRS)

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

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

1977-01-01

74

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

75

Ground-penetrating synthetic aperture radar focusing algorithm  

SciTech Connect

This paper presents an algorithm for image reconstruction of ground-penetrating synthetic aperture radar that can be implemented in real time. The algorithm permits underground focusing. The algorithm was successfully demonstrated at scale using a Ka-band radar in the laboratory that has 1 cm range resolution. The equipment utilized objects on the surface and at depths of 7.5 and 15 cm. With the imaging set for focus at the surface, the buried objects were not detected. The buried objects were detected and resolved to the theoretical limits with the focus appropriately set, with the surface object detected but blurred. Thus, the algorithm provides better detection and resolution of underground objects than algorithms sans underground focus, and also permits an estimate of the depth.

Cribbs, R.W. [Folsom Research, Inc., Folsom, CA (United States)

1994-12-31

76

Topographic mapping from interferometric synthetic aperture radar observations  

NASA Technical Reports Server (NTRS)

The production of high-resolution topographic maps derived from interferometric synthetic aperture radar observations of the Earth is reported. Topographic maps are typically determined from stereo-pair optical photographs. Vertical relief causes the same terrain to appear in a slightly different projection for differing look angles, and this shift in appearance is interpreted in terms of the height of the terrain. The radar interferometric approach is related to the stereo technique in that the terrain is viewed at two different angles; however, in this case, the angular separation of the antennas is extremely small, on the order of a milliradian or less, as compared to tens of degrees for the optical case. Thus, the geometrical distortion and subsequent rectification correction algorithms are much less severe in the reduction of interferometric data.

Zebker, H. A.; Goldstein, R. M.

1985-01-01

77

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

78

Compact, autonomous, multi-mission synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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

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

2013-05-01

79

A comparison of spotlight synthetic aperture radar image formation techniques  

SciTech Connect

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

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

1996-10-01

80

Phase and amplitude phase restoration in synthetic aperture radar imaging.  

PubMed

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

Soumekh, M; Choi, J H

1992-01-01

81

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

82

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

83

Application of polarimetric synthetic aperture radar interferometry for land cover classification  

Microsoft Academic Search

The development of radar polarimetry and radar interferometry is advancing rapidly. The textural fine structure, target orientation, system metrics and material constituents can be recovered with radar polarimetry; while with radar interferometry, the elevation structure of a target can be explored. Polarimetric synthetic aperture radar interferometric (Pol-InSAR) is interferometry between all possible polarization channels at each end of the baseline.

Yang Zhen; Yang Ruliang

2002-01-01

84

Synthetic Aperture Characterization of Radar Satellite Constellations Nathan A. Goodman and James M. Stiles  

E-print Network

- The concept of radar satellite constellations, or clusters, for SAR and other radar modes has been proposed satellite having its own, coherent receiver. Increased swathwidth compared to that of traditional SAR synthetic aperture. Then, the synthetic aperture expression is used to derive resolution; simulations

Kansas, University of

85

Tropospheric phase delay in interferometric synthetic aperture radar estimated from meteorological model and multispectral imagery  

Microsoft Academic Search

ENVISAT Medium Resolution Imaging Spectrometer Instrument (MERIS) multispectral data and the mesoscale meteorological model MM5 are used to estimate the tropospheric phase delay in synthetic aperture radar (SAR) interferograms. MERIS images acquired simultaneously with ENVISAT Advanced Synthetic Aperture Radar data provide an estimate of the total water vapor content W limited to cloud-free areas based on spectral bands ratio (accuracy

Béatrice Puysségur; Rémi Michel; Jean-Philippe Avouac

2007-01-01

86

Opening and closing of sea ice leads: Digital measurements from synthetic aperture radar  

Microsoft Academic Search

The coming opportunity to extract quantitative sea ice data from routine synthetic aperture radar imagery requires the development of automated image processing techniques. An algorithm is described for measuring the opening and the closing of leads by comparing two sequential synthetic aperture radar (SAR) digital images. The pair of images is classified into leads and ice, correcting for variation in

M. Fily; D. A. Rothrock

1990-01-01

87

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 these constraints, a linear frequency modulation- continuous wave (LFM-CW) transmit signal is utilized. Use

Long, David G.

88

MICRO SYNTHETIC APERTURE RADAR USING FM/CW Ryan L. Smith  

E-print Network

MICRO SYNTHETIC APERTURE RADAR USING FM/CW TECHNOLOGY by Ryan L. Smith A thesis submitted;ABSTRACT MICRO SYNTHETIC APERTURE RADAR USING FM/CW TECHNOLOGY Ryan L. Smith Department of Electrical of gener- ating high quality images using frequency modulated, continuous wave (FM/CW) technology and it

Long, David G.

89

Spatially Interpolated Nonlinear Anodization in Synthetic Aperture Radar Imagery  

SciTech Connect

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

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

1999-06-29

90

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

91

The Rapid Terrain Visualization interferometric synthetic aperture radar sensor.  

SciTech Connect

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

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

2003-07-01

92

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.

93

Gulf Stream surface convergence imaged by synthetic aperture radar  

NASA Astrophysics Data System (ADS)

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

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

1994-09-01

94

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

95

Augmenting synthetic aperture radar with space time adaptive processing  

NASA Astrophysics Data System (ADS)

Wide-area persistent radar video offers the ability to track moving targets. A shortcoming of the current technology is an inability to maintain track when Doppler shift places moving target returns co-located with strong clutter. Further, the high down-link data rate required for wide-area imaging presents a stringent system bottleneck. We present a multi-channel approach to augment the synthetic aperture radar (SAR) modality with space time adaptive processing (STAP) while constraining the down-link data rate to that of a single antenna SAR system. To this end, we adopt a multiple transmit, single receive (MISO) architecture. A frequency division design for orthogonal transmit waveforms is presented; the approach maintains coherence on clutter, achieves the maximal unaliased band of radial velocities, retains full resolution SAR images, and requires no increase in receiver data rate vis-a-vis the wide-area SAR modality. For Nt transmit antennas and N samples per pulse, the enhanced sensing provides a STAP capability with Nt times larger range bins than the SAR mode, at the cost of O(log N) more computations per pulse. The proposed MISO system and the associated signal processing are detailed, and the approach is numerically demonstrated via simulation of an airborne X-band system.

Riedl, Michael; Potter, Lee C.; Ertin, Emre

2013-05-01

96

Synthetic aperture radar processing system for search and rescue  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar (SAR) is uniquely suited to help solve the search and rescue problem since it can be utilized either day or night and through both dense fog or thick cloud cover. This paper describes the search and rescue data processing system (SARDPS) developed at Goddard Space Flight Center. SARDPS was developed for the Search and Rescue Mission Office in order to conduct research, development, and technology demonstration of SAR to quickly locate small aircraft which have crashed in remote areas. In order to effectively apply SAR to the detection of crashed aircraft several technical challenges needed to be overcome. These include full resolution SAR image formation using low frequency radar appropriate for foliage penetration, the application of autofocusing for SAR motion compensation in the processing system, and the development of sophisticated candidate crash site detection algorithms. In addition, the need to dispatch rescue teams to specific locations requires precise SAR image georectification and map registration techniques. The final end-to-end processing system allows for raw SAR phase history data to be quickly converted to georeferenced map/image products with candidate crash site locations identified.

Huxtable, Barton D.; Jackson, Christopher R.; Mansfield, Arthur W.; Rais, Houra

1997-06-01

97

Mapping Boreal Wetlands Using Spaceborne Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

Carbon and methane emissions from wetlands and lakes can have a large impact on global climate. These ecosystems are dominant features in the northern high latitudes hence the importance of assessing their spatial and temporal extent to improve upon global net carbon exchange estimates. Spaceborne synthetic aperture radar (SAR) is an effective tool for this purpose since large inaccessible areas can be monitored on a temporal basis regardless of atmospheric conditions or solar illumination and it is sensitive to vegetation and standing water. We employ ERS (C-band, 100 m, VV-polarization) and JERS (L-band, 100 m, HH-polarization) in this study to map wetlands within boreal sub-regions. Large scale L-band SAR mosaics assembled over boreal regions are used with supplementary multi-temporal data for the analysis. Path to path and year to year radiometric differences due predominantly to seasonal changes were a source of confusion. Decision tree classification tools are used to alleviate this problem. Digital elevation models (where available) and derived slope aspect are used to better distinguish drainage patterns. Texture images are used to help differentiate different wetland classes (e.g. fens, bogs, swamps, marshes, and open water). Examples of validated test regions are presented. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology and the University of Washington under contract with the National Aeronautics and Space Administration.

Podest, E.; McDonald, K. C.; Bohn, T.; Lettenmaier, D.

2006-12-01

98

Flight test of a synthetic aperture radar antenna using STEP  

NASA Technical Reports Server (NTRS)

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

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

1984-01-01

99

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

100

The family of atomic functions and digital signal processing in synthetic aperture radar  

Microsoft Academic Search

The report consists of two parts. In the first part, the sampling analysis of weight windows is conducted on the basis of atomic functions (AF) and their application in problems of the classical method of synthetic aperture radar (SAR) is considered. The second part contains fundamentals of a modified method of synthetizing the aperture. The modified ambiguity function for different

V. F. Kravchenko; V. K. Volosyuk; V. V. Pavlikov

2007-01-01

101

THE APPLICATION OF ACTIVE CONTOURS FOR THE LOCALIZATION OF VARYING-CONTRAST EDGES IN SYNTHETIC APERTURE RADAR IMAGES  

E-print Network

applying the basic snake technique to synthetic aperture radar (SAR) remote sensing images APERTURE RADAR IMAGES Benjamin Seppke and Leonie Dreschler-Fischer University of Hamburg, MIN of this work is to accurately localize the tidal creek shorelines in synthetic aperture radar (SAR) imagery

Hamburg,.Universität

102

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

Microsoft Academic Search

Radar remote sensing data provide a unique perspective on the Earth's crust and the processes that have influenced its evolution. Physically based models are required, however, to relate the geophysical quantities being measured by the radar sensor to useful geologic information. Synthetic aperture radar (SAR) data over the Cima volcanic field in the Mojave Desert of California are quantitatively connected

Diane L. Evans; Tom G. Farr; Jakob J. van Zyl

1992-01-01

103

Models of synthetic aperture radar backscattering for bright flows and dark spots on Titan  

Microsoft Academic Search

The synthetic aperture radar (SAR) imaging mode of the Cassini RADAR instrument enables us to map the surface of Titan through its thick atmosphere. The first Cassini close flyby, acquired on 26 October 2004, revealed a complex surface, with areas of low relief and dome-like volcanic constructs, flows, and sinuous channels. In particular, fan-like features with strong radar backscattering were

Philippe Paillou; Marc Crapeau; Charles Elachi; Stephen Wall; Pierre Encrenaz

2006-01-01

104

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

Microsoft Academic Search

Radar remote sensing data provide a unique perspective of the earth's crust and the processes that have influenced its evolution. Physically based models are required, however, to relate the geophysical quantities being measured by the radar sensor to useful geologic information. In this study, synthetic aperture radar (SAR) data over the Cima volcanic field in the Mojave Desert of California

Diane L. Evans; Tom G. Farr; Jakob J. van Zyl

1992-01-01

105

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

106

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

107

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

108

Examination of Two Synthetic Aperture Radar Wind Retrieval Models During Norcsex '95.  

National Technical Information Service (NTIS)

Synthetic Aperture Radar wind retrieval models have great potential to accurately depict the mesoscale wind field on the order of hundreds of meters. However, there are still significant hurdles to overcome in applying the theory in a fully automated algo...

J. B. Hart

1996-01-01

109

Sources of Artefacts in Synthetic Aperture Radar Interferometry Data Sets  

NASA Astrophysics Data System (ADS)

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

Becek, K.; Borkowski, A.

2012-07-01

110

Radar shadow detection in synthetic aperture radar images using digital elevation model and projections  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar (SAR) images are currently widely used in target recognition tasks. In this work, we propose an automatic approach for radar shadow detection and extraction from SAR images utilizing geometric projections along with the digital elevation model (DEM), which corresponds to the given georeferenced SAR image. First, the DEM is rotated into the radar geometry, so that each row would match that of a radar line of sight. Next, we extract the shadow regions by processing row by row until the image is covered fully. We test the proposed shadow detection approach on different DEMs and simulated one-dimensional signals and two-dimensional hills and valleys modeled by various variance-based Gaussian functions. Experimental results indicate that the proposed algorithm produces good results in detecting shadows in SAR images with high resolution.

Prasath, V. B. Surya; Haddad, Oussama

2014-01-01

111

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

112

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

113

Estimation of the real aperture radar modulation transfer function directly from synthetic aperture radar ocean wave image spectra without a priori knowledge of the ocean wave height spectrum  

Microsoft Academic Search

The phase and amplitude of the real aperture radar (RAR) modulation transfer function (MTF) are, applying both simulated and real synthetic aperture radar (SAR) image spectra, shown to strongly influence the SAR ocean wave imaging of range- (or near-range) traveling wave systems. Conventionally, in situ measurement of the sea state has been used in connection with SAR estimation of the

S. Jacobsen; K. A. Høgda

1994-01-01

114

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

115

High Resolution Ionospheric Mapping Using Spaceborne Synthetic Aperture Radars  

NASA Astrophysics Data System (ADS)

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

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

2012-12-01

116

IEEE TRANSACTIONS ON IMAGE PROCESSING 1 Synthetic Aperture Radar Autofocus Based  

E-print Network

demonstrate the superior performance of our proposed methods using computer simulations in both the correct (SAR), successive cancel- lation approach (SCA). I. INTRODUCTION Aspotlight-mode synthetic aperture radar (SAR) provides a high-resolution microwave image using an antenna of small aperture. High

Wiseman, Yair

117

An Exploratory Study to Derive Precipitation over Land from X-Band Synthetic Aperture Radar Measurements  

E-print Network

An Exploratory Study to Derive Precipitation over Land from X-Band Synthetic Aperture Radar) ABSTRACT Global precipitation measurements from space-based radars and microwave radiometers have been will be addressed by the improved sensors that will be placed on the Global Precipitation Measurement (GPM) core

Marzano, Frank Silvio

118

Multidimensional Waveform Encoding: A New Digital Beamforming Technique for Synthetic Aperture Radar Remote Sensing  

Microsoft Academic Search

This paper introduces the innovative concept of multidimensional waveform encoding for spaceborne synthetic aperture radar (SAR). The combination of this technique with digital beamforming on receive enables a new generation of SAR systems with improved performance and flexible imaging capabilities. Examples are high-resolution wide-swath radar imaging with compact antennas, enhanced sensitivity for applications like alongtrack interferometry and moving object indication,

Gerhard Krieger; Nicolas Gebert; Alberto Moreira

2008-01-01

119

Synthetic aperture radar imaging of ocean waves: Comparison with wave measurements  

Microsoft Academic Search

Synthetic aperture radar images of ocean waves were obtained in conjunction with reference wave data near Marineland, Florida, December 14, 1975. Each of the various types of measurements were processed into a form that allowed direct comparisons with the others. Maxima of radar spectra occurred at the same frequencies as the maxima of reference wave height spectra. In a comparison

William McLeish; Duncan Ross; Robert A. Shuchman; Paul G. Teleki; S. Vincent Hsiao; O. H. Shemdin; W. E. Brown

1980-01-01

120

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

Microsoft Academic Search

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

R. Sabry; P. W. Vachon

2005-01-01

121

Models for synthetic aperture radar imaging of the Ocean: A comparison  

Microsoft Academic Search

Theoretical comparisons are made of different models for synthetic aperture radar (SAR) imaging of ocean waves. The velocity bunching model, distributed surface model, Lyzenga model, Canadian Center for Remote Sensing\\/Radarsat (CCRS\\/RADARSAT) model, and the Ocean Research and Engineering (ORE) model are compared analytically with respect to their description of the SAR imaging process and the radar backscatter process. The study

Dayalan P. Kasilingam; Omar H. Shemdin

1990-01-01

122

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

123

On the applicability of 2-D damped exponential models to synthetic aperture radar  

Microsoft Academic Search

This paper examines the modeling of synthetic aperture radar (SAR) phase histories with 2-D damped exponential models of low order. The use of a low order model is warranted when the radar returns are attributable to a small number of point scatterers. We show that the fit of the widely used damped exponential model is highly dependent on the image

Matthew P. Pepin; Michael P. Clark; Jian Li

1995-01-01

124

Terrain Modeling in Synthetic Aperture Radar Images Using Shape-from-Shading  

Microsoft Academic Search

In this paper we introduce a new approach for recov- ering shape-from-shading (SFS) from synthetic aperture radar (SAR) images of the terrain. Three contributions are proposed. Firstly, we show how the direction of surface nor- mals is constrained by the geometry of the radar reflectiv- ity cone. Second, we show how topographic features can be used as boundary constraints on

Adrian G. Bors; Edwin R. Hancock; Richard C. Wilson

2000-01-01

125

Screening of Earthen Levees Using Synthetic Aperture Radar  

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

126

SPECKLE MODELING AND REDUCTION IN SYNTHETIC APERTURE RADAR IMAGERY Ousseini Lankoande, Majeed M. Hayat, and Balu Santhanam  

E-print Network

both simulated as well as real synthetic-aperture-radar (SAR) imagery show that the proposed speckle. 1. INTRODUCTION Synthetic-aperture-radar (SAR) is an imaging system that uses co- herent radiation to create images. The benefit of SAR over non- radar imaging systems is that it does not rely on an external

Hayat, Majeed M.

127

Overview of results of Spaceborne Imaging Radar-C, X-Band Synthetic Aperture Radar (SIR-C\\/X-SAR)  

Microsoft Academic Search

The Spaceborne Imaging Radar-C, X-Band Synthetic Aperture Radar (SIR-C\\/X-SAR) was launched on the Space Shuttle Endeavour for two ten day missions in the spring and fall of 1994. Radar data from these missions are being used to better understand the dynamic global environment. During each mission, radar images of over 300 sites around the Earth were obtained, returning over a

Ellen R. Stofan; Diane L. Evans; Christianna Schmullius; Benjamin Holt; Jeffrey J. Plaut; Jakob van Zyl; Stephen D. Wall

1995-01-01

128

Integrated wideband antenna nulling and focusing technique for MultiChannel Synthetic Aperture Radar  

Microsoft Academic Search

The imaging capability of a synthetic aperture radar (SAR) could be seriously limited or denied by an electromagnetic noise-like interference signal impinging on the antenna during the synthetic aperture. A multi-channel SAR (M-SAR), exploiting an antenna nulling based electronic counter-counter measures (ECCM) technique, shall be able to cancel the effects of interferences over the collected SAR data. Since SAR systems

M. Bucciarelli; D. Cristallini; D. Pastina; M. Sedehi; P. Lombardo

2008-01-01

129

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

Microsoft Academic Search

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

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

1988-01-01

130

The measurement of precipitation with synthetic aperture radar  

NASA Technical Reports Server (NTRS)

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

Atlas, David; Moore, Richard K.

1987-01-01

131

A Three-Dimensional Ray Tracing Simulation of a Synthetic Aperture Ground Penetrating Radar System  

NASA Astrophysics Data System (ADS)

Ground Penetrating Radar (GPR) is a useful tool for imaging the area below the Earth's surface. GPR works on the same principle as traditional radar, evaluating the electromagnetic returns reflected from an object or scene of interest to determine characteristics of the object that reflected the signal. Synthetic Aperture Radar (SAR) is a technique which combines radar returns of a given scene collected at several positions. By compiling the information contained in the returns, an image of a scene can be generated. Combining these two concepts allows us to create an image of an underground scene.

Jeter, James W., III

2002-10-01

132

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

133

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

NASA Technical Reports Server (NTRS)

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

Sivertson, W. E., Jr.

1976-01-01

134

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

Microsoft Academic Search

This report provides a detailed evaluation of synthetic aperture radar (SAR) as a potential technology improvement over the Coast Guard's existing side-looking airborne radar (SLAR) for oil-spill surveillance applications. The U.S. Coast Guard Research and Development Center (RD Center), Environmental Safety Branch, sponsored a joint experiment including the U.S. Coast Guard, Sandia National Laboratories, and the National Oceanographic and Atmospheric

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

1993-01-01

135

Synthetic aperture radar (SAR)-based mapping of wildfire burn severity and recovery  

Microsoft Academic Search

New radar based techniques for efficient identification of forest damage caused by wildfire and subsequent recovery are applied to data acquired over the 2002 Rodeo-Chediski, Arizona and 1988 Yellowstone National Park wildfire complexes. Fully polarimetric C-, L- and P-band airborne synthetic aperture radar data were acquired in approximately east-west and north-south swaths over the northern half of the Rodeo-Chediski wildfire

Kristina R. Czuchlewski; Jeffrey K. Weissel

2005-01-01

136

Synthetic aperture radar (SAR)-based mapping of volcanic flows: Manam Island, Papua New Guinea  

Microsoft Academic Search

We present new radar-based techniques for efficient identification of surface changes generated by lava and pyroclastic flows, and apply these to the 1996 eruption of Manam Volcano, Papua New Guinea. Polarimetric L- and P-band airborne synthetic aperture radar (SAR) data, along with a C-band DEM, were acquired over the volcano on 17 November 1996 during a major eruption sequence. The

J. K. Weissel; K. R. Czuchlewski; Y. Kim

2004-01-01

137

Extraction of ground control points (GCPs) from synthetic aperture radar images and SRTM DEM  

Microsoft Academic Search

Qualified ground control points (GCPs) are crucial in the geolocation of a remotely sensed image. If a region has no published map, the geographical coordinates of GCPs must be obtained indirectly. Although these can be re?constructed from a synthetic aperture radar (SAR) image using sensor position and velocity, this conventional method does not provide accurate GCPs owing to the variable

2006-01-01

138

Synthetic Aperture Radar Processing by a Multiple Scale Neural System for Boundary and Surface  

E-print Network

Supported in part by the Air Force Office of Scientific Reserach (AFOSR F49620­92­J­ 0499), the AdvancedSynthetic Aperture Radar Processing by a Multiple Scale Neural System for Boundary and Surface Systems and Center for Adaptive Systems Boston University 111 Cummington Street, Boston, MA 02215 4

Grossberg, Stephen

139

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

140

Research of the aeroplane intelligent localization methods based on Synthetic Aperture Radar imagery  

Microsoft Academic Search

Synthetic aperture radar (SAR) presents prominent advantages, such as working in all-time and all weather condition, which makes it locate the aeroplane more advantageous. First, the article discusses the effect on aircraft location caused by factors such as topographic relief while SAR imaging. Then, proposes a method that calculates the areoplane's spatial position based on the multi-angular cone model after

Shao Yongshe; Han Yang; Zhang Leiyu

2009-01-01

141

Synthetic aperture radar data visualization on the iPod Touch  

Microsoft Academic Search

A major area of focus for the Air Force is sensor performance in urban environments. Aircraft with multiple sensor modalities, such as Synthetic Aperture RADAR (SAR), Infrared (IR), and Electro-Optics (EO), are essential for intelligence, surveillance, and reconnaissance (ISR) of current and future urban battlefields. Although applications exist for visualization of these types of imagery, they usually require at least

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

2010-01-01

142

Tropospheric phase delay in interferometric synthetic aperture radar estimated from meteorological model  

E-print Network

meteorological model MM5 are used to estimate the tropospheric phase delay in synthetic aperture radar (SAR, are simulated from MM5. A priori pertinent cumulus parameterization and planetary boundary layer options of MM5 ranges where active tectonics might contribute to a measurable SAR signal that is obscured by atmospheric

Avouac, Jean-Philippe

143

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

144

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

145

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

146

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

147

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

148

Ocean wave extraction from RADARSAT synthetic aperture radar inter-look image cross-spectra  

Microsoft Academic Search

This study is concerned with the extraction of directional ocean wave spectra from synthetic aperture radar (SAR) image spectra. The statistical estimation problem underlying the wave-SAR inverse problem is examined in detail in order to properly quantify the wave information content of SAR. As a concrete focus, a data set is considered comprising six RADARSAT SAR images co-located with a

Michael Dowd; Paris W. Vachon; Fred W. Dobson; Richard B. Olsen

2001-01-01

149

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

E-print Network

Fault creep along the southern San Andreas from interferometric synthetic aperture radar, permanent ERS SAR images along the southern San Andreas Fault. First, amplitude stacking is utilized to identify, southern San Andreas, InSAR, atmospheric effects Citation: Lyons, S., and D. Sandwell, Fault creep along

Sandwell, David T.

150

Coherence estimation in synthetic aperture radar data based on speckle noise modeling  

Microsoft Academic Search

In the past we proposed a multidimensional speckle noise model to which we now include systematic phase variation effects. This extension makes it possible to define what is believed to be a novel coherence model able to identify the different sources of bias when coherence is estimated on multidimensional synthetic radar aperture (SAR) data. On the one hand, low coherence

Carlos López-Martínez; Eric Pottier

2007-01-01

151

Fractional Brownian motion models for synthetic aperture radar imagery scene segmentation  

Microsoft Academic Search

The application of fractal random process models and their related scaling parameters as features in the analysis and segmentation of clutter in high-resolution, polarimetric synthetic aperture radar (SAR) imagery is demonstrated. Specifically, the fractal dimension of natural clutter sources, such as grass and trees, is computed and used as a texture feature for a Bayesian classifier. The SAR shadows are

CLAYTON V. STEWART; BABACK MOGHADDAM; KENNETH J. HINTZ; LESLIE M. NOVAK

1993-01-01

152

Focusing of synthetic aperture radar images of moving targets using minimum entropy adaptive filters  

Microsoft Academic Search

Synthetic aperture radar (SAR) imaging systems are used for generating high-resolution images for target detection and identification. However, when imaging moving targets, the imaging process is degraded by target motion. These effects generally manifest as a form of smearing in the azimuthal direction. Since the motion parameters are generally not known, it requires a processing technique that can estimate the

D. Kasilingam; Junfeng Wang; Jong-Sen Lee; R. Jensen

2000-01-01

153

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

Microsoft Academic Search

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

John A. Saghri; Andrew DeKelaita

2006-01-01

154

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

Microsoft Academic Search

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

D. K. Hall; J. P. Ormsby

1983-01-01

155

Extraction of ground control points (GCPs) from synthetic aperture radar image using DEM  

Microsoft Academic Search

Synthetic aperture radar (SAR) data have serious geometric distortions caused by inherent side looking geometry and are usually corrupted by speckle noises so that it is difficult to identify ground control points (GCPs). The location of the pixel in a given SAR image can be derived from the knowledge of sensor position and velocity. We propose a GCP extraction algorithm

Sang-Hoon Hong; H.-S. Jung; J.-S. Won; Hong-Gab Kim

2004-01-01

156

An Adaptive Beamforming Technique for Countering Synthetic Aperture Radar (SAR) Jamming Threats  

Microsoft Academic Search

In a hostile environment synthetic aperture radar (SAR) is likely to be subjected to electronic countermeasures (ECM) to prevent target detection and classification. In practice, noise jamming may not always provide an effective ECM against the SAR because of the large power output required to obscure the SAR image. A potentially more potent threat is presented by deception or repeater

A. S. Paine

2007-01-01

157

Synthesize multi-level composite filter for synthetic-aperture radar image identification  

Microsoft Academic Search

A novel optical correlator system to identify the Synthetic-Aperture Radar (SAR) image based on multilevel composite function (MCF) filters, constructed in input domain, is presented. The MCFs are synthesized by the simulated annealing algorithm, which are suitable to current spatial light modulators because of their limited dynamic range requirement of the MCFs. In this paper, we focus our investigation on

Chun-Te Li; Jiang Li; Shizhuo Yin; Tracy D. Hudson; Deanna K. McMillen

1998-01-01

158

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

Microsoft Academic Search

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

Murali M. Menon

1995-01-01

159

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

Microsoft Academic Search

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

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

2009-01-01

160

Genetic programming for automatic target classification and recognition in synthetic aperture radar imagery  

Microsoft Academic Search

We use the genetic programming (GP) paradigm for two tasks. The first task given a GP is the generation of rules for the target \\/ clutter classification of a set of synthetic aperture radar (SAR) images, the second, the generation of rules for the identification of tanks in a second set of SAR images. To perform these tasks, previously defined

Stephen A. Stanhope; Jason M. Daida

161

ESTIMATING UNDERWATER ACOUSTICAL PARAMETERS FROM SPACE-BASED SYNTHETIC APERTURE RADAR IMAGERY  

Microsoft Academic Search

Synthetic aperture radar (SAR) imagery from satel- lites provides a range of data products that can reveal certain aspects of the underwater acoustical environment. Space-based SAR imagery is avail- able in all weather, day or night and has wide area coverage with swaths up to 500 km across. This availability and coverage gives SAR satellite data the potential to enhance

Dan L. Hutt; Paris W. Vachon

162

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

Microsoft Academic Search

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

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

2010-01-01

163

A compact implementation of a real time acousto-optic synthetic aperture radar processor  

NASA Technical Reports Server (NTRS)

The architecture of a real-time acoustooptic synthetic aperture radar processor is reviewed and recent efforts to develop a compact processor are presented. It employs an acoustooptic device operated in the space integrating mode to compress the signal in range.

Shaik, Kamran; Lesh, James R.; Hemmati, Hamid

1988-01-01

164

Wind retrieval over the China Seas using satellite synthetic aperture radar  

Microsoft Academic Search

The high spatial resolution and large coverage of synthetic aperture radar (SAR) offers a good opportunity to retrieve detailed wind vector information over the oceans, especially in the coast areas. In the work presented here, the wind speeds estimate is based on the data from ScanSAR aboard the Canadian satellite RADARSAT, operating at C-band with horizontal polarization, and the empirically

Qian Feng; Mingqiang Fang; Yingjian Liu; Laibu Wang

2004-01-01

165

Adaptive detection of moving target based on velocity synthetic aperture radar  

Microsoft Academic Search

By dividing a vector sampling at a specified pixel into three components, namely target, clutter, and noise, a novel parametric statistical model is proposed in the multi-channel and multi-look image domain of velocity synthetic aperture radar (VSAR). With the proposed parametric model, an adaptive moving target detection method is also obtained for VSAR, based on which the optimum improvement factors

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

2007-01-01

166

Extreme Wind and Wave Conditions Observed by Synthetic Aperture Radar on a Regional and Global Scale  

Microsoft Academic Search

It is well known that synthetic aperture radar (SAR) provides information on ocean winds and surface waves. SAR data are of particularly high value in extreme weather conditions where the sensor is still able to penetrate the clouds providing information on different ocean surface processes. In this paper some recent results on the SAR observation of extreme wind and ocean

S. Lehner; T. König; A. Reppucci; J. Schulz-Stellenfleth

2006-01-01

167

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

Microsoft Academic Search

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

A. Hooper; P. Segall; H. Zebker

2007-01-01

168

The Rhine Outflow Plume Studied by the Analysis of Synthetic Aperture Radar Data and Numerical Simulations  

Microsoft Academic Search

The dynamics of the Rhine outflow plume in the proximity of the river mouth is investigated by using remote sensing data and numerical simulations. The remote sensing data consist of 41 synthetic aperture radar (SAR) images acquired by the First and Second European Remote Sensing satellites ERS-1 and ERS-2 over the outflow region of the river Rhine. Most of them

Katrin Hessner; Angelo Rubino; Peter Brandt; Werner Alpers

2001-01-01

169

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

Microsoft Academic Search

We present a Wiener filter that is especially suitable for speckle and noise reduction in multilook synthetic aperture radar (SAR) imagery. The proposed filter is nonparametric, not being based on parametrized analytical models of signal statistics. Instead, the Wiener Hopf equation is expressed entirely in terms of observed signal statistics, with no reference to the possibly unobservable pure signal and

Robert S. Caprari; Alvin S. Goh; Emily K. Moffatt

2000-01-01

170

(Automatic) target detection in synthetic aperture radar imagery via terrain recognition  

Microsoft Academic Search

Surveillance of large areas of the Earths surface is often un- dertaken with low resolution synthetic aperture radar (SAR) imagery from either a satellite or a plane. There is a need to process these images with automatic target detection (ATD) algorithms. Typically the targets being searched for are ve- hicles or small vessels, which occupy only a few resolution cells.

Rupert Paget; John Homer; Donald Crisp

2001-01-01

171

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

Microsoft Academic Search

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

Jian Li

1994-01-01

172

A noise model for estimated synthetic aperture radar look cross spectra acquired over the ocean  

Microsoft Academic Search

It is well known that look cross spectra processed from synthetic aperture radar (SAR) contain valuable information on ocean waves. With the launch of the European satellite ENVISAT, SAR look cross spectra (SLCS) have become available on an operational basis. Activities therefore exist at different European weather centres to use the data for assimilation into numerical wave models. Furthermore there

Johannes Schulz-Stellenfleth; Susanne Lehner

2005-01-01

173

Wavelet packet-based nonlinear speckle reduction in optical synthetic aperture radar image analysis  

Microsoft Academic Search

A new technique for efficient speckle reduction in synthetic aperture radar (SAR) images using wavelet packets is proposed. A phenomenological approach is used in adapting the wavelet packet transform to minimize the speckle coefficients. With thresholding and averaging, the resulting non-linear, multirate filtering can be used to preprocess images for reduction of speckle while retaining contrast in key objects necessary

Khan M. Iftekharuddin; Theresa A. Tuthill

1996-01-01

174

SYNTHETIC-APERTURE RADAR IMAGING AND WAVEFORM DESIGN FOR DISPERSIVE MEDIA  

E-print Network

SYNTHETIC-APERTURE RADAR IMAGING AND WAVEFORM DESIGN FOR DISPERSIVE MEDIA By Jos´e H´ector Morales . . . . . . . . . . . . . . . . . . . . 14 2.0.2.1 Image Variance, Bias, and Expected Mean-Square Error FOR DISPERSIVE MEDIA . . . . . . . . . . . . . 28 3.1 Determination of the Power Spectrum Amplitude

Cheney, Margaret

175

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

176

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

177

An Interferometric Technique for Synthetic Aperture Ground-Penetrating Radar Carl Leuschen, Nathan Goodman, Chris Allen, Richard Plumb  

E-print Network

--Many synthetic aperture radar (SAR) algorithms for ground-penetrating radar involve making measurements along interferometric techniques to SAR-based images, it is possible to construct an image of the scattering object proposes a method of combining radar interferometry with SAR-based ground-penetrating radar

Kansas, University of

178

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

179

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

NASA Technical Reports Server (NTRS)

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

Plaut, Jefferey J.

1996-01-01

180

Waveform error analysis for bistatic synthetic aperture radar systems  

NASA Astrophysics Data System (ADS)

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

Adams, J. W.; Schifani, T. M.

181

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

182

Real-time multiple-look synthetic aperture radar processor for spacecraft applications  

NASA Technical Reports Server (NTRS)

A spaceborne synthetic aperture radar (SAR) having pipeline multiple-look data processing is described which makes use of excessive azimuth bandwidth in radar echo signals to produce multiple-looking images. Time multiplexed single-look image lines from an azimuth correlator go through an energy analyzer which analyzes the mean energy in each separate look to determine the radar antenna electric boresight for use in generating the correct reference functions for the production of high quality SAR images. The multiplexed single look image lines also go through a registration delay to produce multi-look images.

Wu, C.; Tyree, V. C. (inventors)

1981-01-01

183

High-Resolution Synthetic Aperture Radar Observations of the Moon  

Microsoft Academic Search

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

Nicholas John Sholto Stacy

1993-01-01

184

Resolution and synthetic aperture characterization of sparse radar arrays  

E-print Network

the theory. We make our conclusions in Section V. II. RADAR MODEL The assumed radar geometry is shown in Fig. 1. The spaceborne system travels in the positive x-direction at velocity v, and the array phase reference at time zero is located at the origin... x is given by x = [xy#0;?h] † where (#0;?) † denotes the matrix or vector transpose operation. Since the transmitter is located at the array phase reference, which passes through the origin at time t = 0, its position at any given time is r t =vt...

Stiles, James Marion; Goodman, N. A.

2003-07-01

185

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

186

Three-dimensional subsurface imaging synthetic aperture radar  

Microsoft Academic Search

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

Moussally

1995-01-01

187

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

188

Structure selection in synthetic aperture radar scattering models  

Microsoft Academic Search

High-frequency models for radar backscatter can include components with different structures that correspond to different physical scattering mechanisms on an object. We consider the problem of structure selection for an attributed scattering center model that includes both localized and distributed scattering terms. We propose three structure classification algorithms, and compare their performance. We show that a threshold test on the

Y. Akyildiz; R. L. Moses

2000-01-01

189

Evidence of Rainfall Signatures on X-Band Synthetic Aperture Radar Imagery Over Land  

Microsoft Academic Search

Five spaceborne X-band synthetic aperture radars (X-SARs) are nowadays operating, and several more will be launched in the coming years. These X-SAR sensors, 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 a few hundred meters due to the moving-target degradation effects. This work is

Frank Silvio Marzano; Saverio Mori; James A. Weinman

2010-01-01

190

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

191

Inversion of Spaceborne X-Band Synthetic Aperture Radar Measurements for Precipitation Remote Sensing Over Land  

Microsoft Academic Search

Several spaceborne X-band synthetic aperture radar (X-SAR) systems were launched in 2007, and more will be launched in the current decade. These sensors may significantly augment the sensors that comprise the global precipitation mission (GPM) constellation. X-SAR rainfall measurements may be beneficial particularly over land where rainfall is difficult to measure by means of satellite microwave radiometers. Inversion techniques to

Frank Silvio Marzano; James A. Weinman

2008-01-01

192

Potential of X-band spaceborne synthetic aperture radar for precipitation retrieval over land  

Microsoft Academic Search

Numerous space-borne X-band Synthetic Aperture Radars (X-SAR) systems will be launched by European agencies in the coming decade commencing this year. Those X-SARs can measure precipitation over land, thereby significantly augmenting the sensors that comprise the Global Precipitation Mission (GPM). This will incur relatively little incremental cost because they have already been funded. X-SAR measurements are especially beneficial over land

F. S. Marzano; G. Poccia; R. Cantelmi; N. Pierdicca; J. A. Weinman; V. Chandrasekar; A. Mugnai

2007-01-01

193

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

194

MONITORING OF THE SNOW COVER WITH A GROUND-BASED SYNTHETIC APERTURE RADAR  

Microsoft Academic Search

The feasibility of retrieving changes in the depth of snow cover by means of the LISA (LInear SAR) Ground-Based Synthetic Aperture Radar system has been investigated. The LISA instrument con- sists of a computer-controlled sledge moving along a linear axis 5 m long, a set of transmit and receive antennas, a network analyzer, and a C-Band amplifier. All the equipment

Alberto Martinez-Vazquez; Joaquim Fortuny-Guasch; Urs Gruber

2005-01-01

195

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

Microsoft Academic Search

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

Ken Yoong LEE; Timo Rolf BRETSCHNEIDER

196

Remote sensing of ocean waves by along-track interferometric synthetic aperture radar  

Microsoft Academic Search

A new wave retrieval method for the Along-Track Interferometric Synthetic Aperture Radar (AT-InSAR) phase image is presented. The new algorithm, named parametric retrieval algorithm (PRA), uses the full nonlinear mapping relations. It differs from previous retrieval algorithms in that it does not require a priori information about the sea state or the wind vector from scatterometer data. Instead, it combines

Biao Zhang; Will Perrie; Yijun He

2009-01-01

197

Comparison of actual and simulated synthetic aperture radar image spectra of ocean waves  

Microsoft Academic Search

We have simulated synthetic aperture radar (SAR) image spectra of ocean waves which were focused for stationary scenes using three popular formulations of SAR ocean imaging theory: the time-dependent, velocity-bunching, and quasi-linear models. All three models require functional forms for surface wave spectra, modulation transfer functions, and correlation times; these were obtained from data taken during the SAR and X

L. M. Zurk; William J. Plant

1996-01-01

198

Ultra-wide-band synthetic-aperture radar for minefield detection  

Microsoft Academic Search

A full-wave model is developed for electromagnetic scattering from buried and surface land mines (both conducting and plastic), taking rigorous account of the lossy, dispersive, and potentially layered properties of soil. The (polarimetric) theoretical results are confirmed via synthetic-aperture radar (SAR) measurements, performed using the US Army Research Laboratory's BoomSAR, with which fully polarimetric ultra-wide-band (50-1200 MHz) SAR imagery is

Lawrence Carin; Norbert Geng; Mark McClure; Jeffvey Sichina; Lam Nguyen

1999-01-01

199

Cueing, feature discovery, and one-class learning for synthetic aperture radar automatic target recognition  

Microsoft Academic Search

The exquisite capabilities of biological neural systems for recognizing target patterns subject to large variations have motivated us to investigate neurophysiologically-inspired techniques for automatic target recognition. This paper describes a modular multi-stage architecture for focus-of-attention cueing, feature discovery and extraction, and one-class pattern learning and identification in synthetic aperture radar imagery.To prescreen massive amounts of image data, we apply a

Mark W. Koch; Mary M. Moya; Larry D. Hostetler; R. Joseph Fogler

1995-01-01

200

Electromagnetic induced timing defects in the synthetic aperture radar of the Magellan spacecraft  

Microsoft Academic Search

The Magellan spacecraft synthetic aperture radar experienced a failure when the receiver protect circuitry in the PRF\\/Timing subsystem failed. The receiver protect circuitry failed due to electromagnetic coupling from the ultra stable oscillator\\/clock generator circuit located on an adjacent board. Some ICs in this ultra stable oscillator\\/clock generator circuit had previously become detached from their traces when a thermal test

R. Perez

1996-01-01

201

Identification of sea ice types in spaceborne synthetic aperture radar data  

Microsoft Academic Search

An approach for identification of sea ice types in spaceborne synthetic aperture radar (SAR) image data is presented. The unsupervised classification approach involves cluster analysis for segmentation of the image data followed by cluster labeling based on previously defined look-up tables containing the expected backscatter signatures of different types measured by land-based scatterometer. The particular look-up table used for labeling

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

1992-01-01

202

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

Microsoft Academic Search

With the large amount of image data that can be produced in real-time by new synthetic aperture radar (SAR) platforms, such as Global Hawk, compression techniques will be needed for both transmission and storage of this data. Also to keep image analysts (IA's) from being overwhelmed, high-speed automatic target cueing and\\/or recognition (ATC, ATR) systems will be needed to help

Michael Hoffelder; Jun Tian

2000-01-01

203

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

204

Monitoring snowmelt across the Arctic forest–tundra ecotone using Synthetic Aperture Radar  

Microsoft Academic Search

Detailed snowpack observations, meteorology, topography and landcover classification were integrated with multi?temporal SAR data to assess its capability for landscape scale snowmelt mapping at the forest–tundra ecotone. At three sites along an approximately 8° latitudinal gradient in the Fennoscandian mountain range, 16 multi?temporal spaceborne ERS?2 synthetic aperture radar (SAR) were used for mapping snowmelt.Comparison of field measurements and backscatter values

A. M. Dean; I. A. Brown; B. Huntley; C. J. Thomas

2006-01-01

205

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

Microsoft Academic Search

The feasibility of measuring volcanic deformation or monitoring deformation of active volcanoes using space-borne synthetic aperture radar (SAR) interferometry depends on the ability to maintain phase coherence over appropriate time intervals. Using ERS 1 C band (lambda=5.66cm) SAR imagery, we studied the seasonal and temporal changes of the interferometric SAR coherence for fresh lava, weathered lava, tephra with weak water

Zhong Lu; Jeffrey T. Freymueller

1998-01-01

206

A comparison of some electronic countermeasures on Inverse Synthetic Aperture Radar (ISAR)  

Microsoft Academic Search

Inverse Synthetic Aperture Radar (ISAR) is an important means for target classification, recognition, identification and many\\u000a other military applications. A simulation model of ISAR system is established after analyzing the principle of ISAR imaging,\\u000a and then several ECM (Electronic Counter Measurement) techniques are studied. Simulation experiments are done on the basis\\u000a of such research. The experimental result of the research

Luhong Fan; Yiming Pi; Shunji Huang; Yinming Hou

2006-01-01

207

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

Microsoft Academic Search

We present the theoretical investigation of a novel architecture of a LiNbO3 guided-wave optical processor suitable for real-time microwave imaging in on-board synthetic aperture radar (SAR) applications, using a moving platform on either an aircraft or a spacecraft. The new configuration, which is basically interferometric, includes four Mach-Zehnder modulators, each characterized by an additional aperiodic phase-reversal traveling wave modulator. The

Mario N. Armenise; Vittorio M. Passaro

1994-01-01

208

Vegetation profiles in tropical forests from multibaseline interferometric synthetic aperture radar, field, and lidar measurements  

Microsoft Academic Search

This paper addresses the estimation of vertical vegetation density profiles from multibaseline interferometric synthetic aperture radar (InSAR) data from the AirSAR aircraft at C band over primary, secondary, and abandoned-pasture stands at La Selva Biological Station, Costa Rica in 2004. Profiles were also estimated from field data taken in 2006 and lidar data taken with the LVIS, 25 m spot

R. N. Treuhaft; B. D. Chapman; J. R. dos Santos; F. G. Gonçalves; L. V. Dutra; P. M. L. A. Graça; J. B. Drake

2009-01-01

209

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

210

Strapdown inertial measurement units for motion compensation for synthetic aperture radars  

Microsoft Academic Search

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

Thomas A. Kennedy

1988-01-01

211

Ultra-wide-band model-based synthetic aperture radar imaging through complex media  

Microsoft Academic Search

It is known that electromagnetic signals can penetrate into non-metallic barriers such as building walls and soil. A portable Synthetic Aperture Radar (SAR) unit capable of transmitting and receiving such signals is desirable in various non-intrusive (proximity or remote) sensing applications. Theoretical and experimental issues associated with Ultra-Wide-Band (UWB) SAR imaging through complex media are studied. The complex media of

Lixin Cai

2000-01-01

212

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

Microsoft Academic Search

New space-based Interferometric Synthetic Aperture Radar (InSAR) observations of the Everglades wetlands provide high spatial resolution maps of water level changes that are essential for improved modeling efforts of surface water sheetflow. In this study, we model the Everglades' Water Conservation Area 1 (WCA-1), which is used to restore, protect, and preserve water resources and wildlife in southern Florida. We

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

2005-01-01

213

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

214

Coseismic crustal deformations of 1994 Northridge, California, earthquake detected by interferometric JERS 1 synthetic aperture radar  

Microsoft Academic Search

Coseismic deformations of the January 17, 1994, Northridge, California earthquake are mapped using interferometric combination of synthetic aperture radar images acquired by the Japanese Earth Resource Satellite (JERS 1) on April 30, 1993, and June 14, 1994. We make an interferogram in a rectangular area with a size of 18.6 km (N-S) by 29.9 km (E-W). Although coherence is not

Makoto Murakami; Mikio Tobita; Satoshi Fujiwara; Takashi Saito; Hiroshi Masaharu

1996-01-01

215

Modeling of synthetic aperture radar for nonconventional geometry  

Microsoft Academic Search

Basic SAR equations for Doppler bandwidth, point-scatterer response, focused and unfocused resolution, and iso-Doppler contours, are presently generalized to the case where the platform is not in level flight and the radar is squinted. The effects of the geometry on S\\/N, minimum pulse repetition frequency, and maximum swath, are also noted. A computer simulation of a mm-wave SAR on a

M. A. Richards; G. H. Lunsford; A. H. Green Jr.

1985-01-01

216

Determination of ocean wave heights from synthetic aperture radar imagery  

Microsoft Academic Search

A calculation is presented for the cross-correlation of the radar images obtained by processing the same signal data over\\u000a different portions of the chirp spectrum bandwidth as a function of the center frequency spacings for these portions. This\\u000a is shown to be proportional to the square of the product of the characteristic function for ocean wave heights and the pupil

Atul Jain

1977-01-01

217

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

218

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

219

Modeling of synthetic aperture radar for nonconventional geometry  

NASA Astrophysics Data System (ADS)

Basic SAR equations for Doppler bandwidth, point-scatterer response, focused and unfocused resolution, and iso-Doppler contours, are presently generalized to the case where the platform is not in level flight and the radar is squinted. The effects of the geometry on S/N, minimum pulse repetition frequency, and maximum swath, are also noted. A computer simulation of a mm-wave SAR on a translating and rotating missile platform is employed, and selected plots of the detailed geometric behavior of several key SAR quantities ae presented.

Richards, M. A.; Lunsford, G. H.; Green, A. H., Jr.

220

Estimating Titan Surface Topography from Cassini Synthetic Aperture RADAR Data  

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

221

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

222

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

SciTech Connect

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

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

1993-10-01

223

Japanese Earth Resources Satellite-1 synthetic aperture radar  

NASA Astrophysics Data System (ADS)

The spaceborne L-band SAR to be launched on the Japanese Earth Resources Satellite-1 is described. The mission is mainly dedicated to geological applications. The ground resolution of the processed image is designed as 18 m, and the off-nadir angle required to meet geological applications is 35 deg. The design and performance of the key system parameters are discussed, along with the reasons for choosing such design parameters. The antenna is a thin-flat-foldable configuration that has a 11.9-m by 2.2-m aperture when extended in orbit. The transmitter, receiver, and signal processor are all of the solid-state type to achieve high reliability of operation. They transmit an 1100-W peak (minimum) chirp pulse and receive the return echos and process the echo signals into in-phase and quadrature data streams.

Nemoto, Yoshiaki; Nishino, Hideo; Ono, Makoto; Mizutamari, Hitoshi; Nishikawa, Katsuhiko; Tanaka, Kaoru

1991-06-01

224

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

NASA Astrophysics Data System (ADS)

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

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

1992-03-01

225

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

226

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

227

Synthetic Aperture Radar: The NCCS Enables Search and Rescue  

NASA Astrophysics Data System (ADS)

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

2002-07-01

228

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

229

Synthetic aperture radar imaging of ocean waves - Comparison with wave measurements  

NASA Technical Reports Server (NTRS)

Synthetic aperture radar images of ocean waves were obtained in conjunction with reference wave data near Marineland, Florida, December 14, 1975. Each of the various types of measurements were processed into a form that allowed direct comparisons with the others. Maxima of radar spectra occurred at the same frequencies as the maxima of reference wave height spectra. In a comparison of a radar spectrum with observed spectra of wave height, wave orbital velocity, and surface slope the high-frequency portion of the radar spectrum lay near and between the wave height and the orbital velocity spectra but differed significantly from the surface slope spectrum. The radar-derived mean directions and model-fitted directional spreads of wave energy were close to the values from a directional wave buoy and indicated the accuracy of radar measurements of wave direction. However, a directional plot of a radar spectrum near shore at the frequency of the maximum showed a sharper peak than such a plot of a fitted spectrum derived from reference data.

Mcleish, W.; Ross, D.; Shuchman, R. A.; Teleki, P. G.; Hsiao, S. V.; Shemdin, O. H.; Brown, W. E., Jr.

1980-01-01

230

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

NASA Astrophysics Data System (ADS)

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

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

2014-06-01

231

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

232

Polarimetric synthetic aperture radar study of the Tsaoling landslide generated by the 1999 Chi-Chi earthquake, Taiwan  

Microsoft Academic Search

We employ L-band airborne synthetic aperture radar (SAR) polarimetry to detect surface changes produced by the Tsaoling landslide, the largest slope failure triggered by the September 1999 Chi-Chi earthquake in central Taiwan. Imaging polarimeters provide a complete description of the scattering properties of radar target materials. Resurfacing of forested hillslopes by landslides alters scattering mechanisms from those dominated by backscatter

Kristina R. Czuchlewski; Jeffrey K. Weissel; Yunjin Kim

2003-01-01

233

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

Microsoft Academic Search

In industrial process measurement instrumentation, radar systems are well established for the measurement of filling levels of liquids in tanks. Level measurements of bulk goods in silos, on the other hand, are more challenging because the material is heaped up and its surface has typically a relatively complex shape. In this paper, the application of synthetic aperture radar (SAR) reconstruction

M. Vogt; M. Gerding; T. Musch

2010-01-01

234

A statistical approach for determining radiometric precisions and accuracies in the calibration of synthetic aperture radar imagery  

Microsoft Academic Search

A model that estimates a relative error bound for the radiometric calibration of synthetic aperture radar (SAR) imagery is presented. This model is based on a statistical `Coefficient of Variation of Error Model', which produces a relative error bound by propagating the measured or estimated uncertainties in the radar system parameters utilized to correct digitally processed SAR image intensity values.

E. S. Kasischke; G. W. Fowler

1989-01-01

235

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

NASA Technical Reports Server (NTRS)

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

Wu, C.

1976-01-01

236

Comparison of synthetic aperture radar autofocus techniques---Phase gradient vs subaperture  

SciTech Connect

Two methods of focusing synthetic aperture radar (SAR) images are compared. Both a conventional subaperture cross-correlation method and a new phase gradient autofocus (PGA) algorithm developed at Sandia National Laboratories are shown to perform well if high-order phase errors are not present. With the introduction of significant high-order phase errors (e.g., due to uncompensated platform motion), both algorithms suffer a loss in performance. However, relative performance degradation is less for PGA than for the subaperture focusing technique. An explanation is presented for the observed behavior of the two autofocus techniques. 8 refs., 8 figs.

Calloway, T.M.; Jakowatz, C.V. Jr.; Thompson, P.A.; Eichel, P.H.

1991-01-01

237

Synthetic aperture radar for search and rescue: evaluation of advanced capabilities in preparation for RADARSAT-2  

NASA Astrophysics Data System (ADS)

Researchers at the Canada Centre for Remote Sensing of Natural Resources Canada are exploring the use of remotely sensed imagery to assist Search and Rescue in Canada. Studies have been examining the use of Synthetic Aperture Radar for the detection of crashed aircraft. Promising results have been obtained with techniques for detection of dihedrals in interferometric and polarimetric data. With further development in technologies and techniques, and improved coverage of the Canadian landmass by future spaceborne systems such as RADARSAT-2, it is expected that it will be possible to assist in Search and Rescue for land targets.

Lukowski, Tom I.; Khellah, Fakhry; Charbonneau, Francois J.; Yue, Bing

2002-07-01

238

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

NASA Technical Reports Server (NTRS)

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

Bindschadler, Robert; Fahnestock, Mark; Kwok, Ron

1993-01-01

239

Use of compact synthetic aperture radar systems to assist with device detection and discrimination  

NASA Astrophysics Data System (ADS)

NuSAR (Naval Research Laboratory Unmanned Synthetic Aperture Radar) is a sensor developed under the ONRfunded FEATHAR (Fusion, Exploitation, Algorithms, and Targeting for High-Altitude Reconnaissance) program. FEATHAR is being directed and executed by the Naval Research Laboratory (NRL) in conjunction with the Space Dynamics Laboratory (SDL). FEATHAR's goal is to develop and test new tactical sensor systems specifically designed for small manned and unmanned platforms (payload weight < 50 lbs). NuSAR is a novel dual-band (L- and X-band) SAR capable of a variety of tactically relevant operating modes and detection capabilities. Flight test results will be described for narrow and wide bandwidth and narrow and wide azimuth aperture operating modes.

Jensen, Mark; Walls, Thomas J.; Anderson, Scott A.; Linne von Berg, Dale; Holt, Niel; Kruer, Melvin; Long, David G.; Wilson, Michael L.

2010-04-01

240

Seasat synthetic aperture radar observations of wave-current and wave-topographic interactions  

NASA Technical Reports Server (NTRS)

This study investigated the capability of a spaceborne, imaging radar system to detect subtle changes in the propagation characteristics of ocean wave systems. Specifically, an evolving surface gravity wave system emanating from Hurricane Ella and propagating toward Cape Hatteras, NC, formed the basis of this investigation. This wave system was successfully imaged by the Seasat synthetic aperture radar (SAR) during revolution 974 on September 3, 1978. Estimates of the dominant wavelength and direction of the ocean waves were derived from the SAR data by using optical Fourier transforms. Environmental data of the test area, which included the surface velocity vector within the Gulf Stream, the location of Hurricane Ella, and local bathymetric information, were used in conjunction with the SAR data to form the basis of this comparative study. Favorable agreement was found between wave rays calculated by utilizing theoretical wave-current and wave-topographic interactions and SAR observed dominant wavelength and direction changes across the Gulf Stream and continental shelf.

Meadows, G. A.; Tseng, Y. C.; Shuchman, R. A.; Kasischke, E. S.

1983-01-01

241

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

242

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

NASA Astrophysics Data System (ADS)

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

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

2000-03-01

243

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

244

Measurements of the radar cross section and Inverse Synthetic Aperture Radar (ISAR) images of a Piper Navajo at 9.5 GHz and 49 GHz  

Microsoft Academic Search

Studies were conducted of the enhanced radar cross section (RCS) and improved inverse synthetic aperture radar (ISAR) image quality that may result at millimeter-wave (mmw) frequencies. To study the potential for mmw radar in these areas, a program was initiated in FY-90 to design and fabricate a 49.0- to 49.5-GHz stepped-frequency radar. After conducting simultaneous measurements of the RCS of

R. Dinger; G. Kinzel; W. Lam; S. Jones

1993-01-01

245

Retrieval of soil moisture using airborne synthetic- and real- aperture radar data at different spatial scales  

NASA Astrophysics Data System (ADS)

For the studies of surface soil moisture, radar observations offer high spatial resolution through aperture synthesis. The spatial resolution may be tens of meters from airborne platform to a few kilometers for global mapping from spaceborne platforms such as the L-band Soil Moisture Active Passive (SMAP) mission. A suite of sophisticated radar scattering forward models 'data-cubes' were developed for 17 land cover classes that simulate the radar response to soil moisture, surface roughness, and diverse vegetation. The inversion of the forward models to estimate soil moisture becomes a well-constrained problem through time-series analysis and parameterization of vegetation structure through an empirical allometric relationship. The retrieval approach has been developed for application using SMAP radar observations. This paper studies the applicability of the approach to radar observations over various spatial scales. The high-resolution airborne L-band radar data were collected by the Uninhabited Aerial Vehicle Synthetic Aperture Radar during the SMAP Validation Experiment 2012 conducted near Winnipeg, Canada in 2012 over agriculture fields. During the six-week campaign period, there were three major drying cycles of surface soil moisture that occurred while the agricultural vegetation grew from bare condition to full canopy. The volumetric soil moisture and radar backscattering generally showed a positive relationship when the vegetation effect was not strong, such as over pasture fields, or when the vegetation effect did not change substantially over time, such as for wheat fields. However, the significant temporal changes in corn and soybean canopies from bare to full growth result in a reverse of this relationship over these fields. The data-cube retrieval approach was able to systematically correct for the effect of the changing vegetation. Errors in soil moisture retrieval ranged from 0.037 to 0.086 cm3/cm3, when evaluated over all the available fields. In addition, the Passive Active L-band Sensor (PALS) was flown during the campaign. This instrument collected real-aperture radar data over the same spatial and temporal domains as those of the UAVSAR. The PALS spatial resolution is about 650m and often includes more than one crop types within a footprint. The data-cube retrieval algorithm will be applied to the PALS radar data and its ability to perform with the heterogeneous vegetation conditions will be evaluated. The scatterometer onboard the Aquarius/SAC-D satellite has provided the global 70km-resolution radar data for 3 years so far. The radar forward model predictions match the Aquarius data with the mean difference of about 2 dB and a standard deviation of about 3 dB (one sigma) globally. The data-cube retrieval will also be tested on a global scale using the Aquarius data.

Kim, S.; Tsang, L.; Liao, T.; Huang, H.; Jackson, T. J.

2013-12-01

246

Oil detection in a coastal marsh with polarimetric Synthetic Aperture Radar (SAR)  

USGS Publications Warehouse

The National Aeronautics and Space Administration's airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) was deployed in June 2010 in response to the Deepwater Horizon oil spill in the Gulf of Mexico. UAVSAR is a fully polarimetric L-band Synthetic Aperture Radar (SAR) sensor for obtaining data at high spatial resolutions. Starting a month prior to the UAVSAR collections, visual observations confirmed oil impacts along shorelines within northeastern Barataria Bay waters in eastern coastal Louisiana. UAVSAR data along several flight lines over Barataria Bay were collected on 23 June 2010, including the repeat flight line for which data were collected in June 2009. Our analysis of calibrated single-look complex data for these flight lines shows that structural damage of shoreline marsh accompanied by oil occurrence manifested as anomalous features not evident in pre-spill data. Freeman-Durden (FD) and Cloude-Pottier (CP) decompositions of the polarimetric data and Wishart classifications seeded with the FD and CP classes also highlighted these nearshore features as a change in dominant scattering mechanism. All decompositions and classifications also identify a class of interior marshes that reproduce the spatially extensive changes in backscatter indicated by the pre- and post-spill comparison of multi-polarization radar backscatter data. FD and CP decompositions reveal that those changes indicate a transform of dominant scatter from primarily surface or volumetric to double or even bounce. Given supportive evidence that oil-polluted waters penetrated into the interior marshes, it is reasonable that these backscatter changes correspond with oil exposure; however, multiple factors prevent unambiguous determination of whether UAVSAR detected oil in interior marshes.

Ramsey, Elijah W., III; Rangoonwala, Amina; Suzuoki, Yukihiro; Jones, Cathleen E.

2011-01-01

247

Estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar: the 1997 eruption of Okmok volcano, Alaska  

Microsoft Academic Search

Interferometric synthetic aperture radar (InSAR) techniques are used to calculate the volume of extrusion at Okmok volcano, Alaska by constructing precise digital elevation models (DEMs) that represent volcano topography before and after the 1997 eruption. The posteruption DEM is generated using airborne topographic synthetic aperture radar (TOPSAR) data where a three-dimensional affine transformation is used to account for the misalignments

Zhong Lu; Eric Fielding; Matthew R. Patrick; Charles M. Trautwein

2003-01-01

248

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

SciTech Connect

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

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

1994-05-01

249

Upper ocean fine-scale features in synthetic aperture radar imagery. Part II: Numerical modeling  

NASA Astrophysics Data System (ADS)

We have been able to reproduce synthetic aperture radar (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 numerical simulations were performed using a non-hydrostatic model, the computational fluid dynamics (CFD) software ANSYS Fluent. We modeled the dynamics of freshwater plumes and their interaction with ambient stratification in the upper ocean as well as with wind stress. We then combined the results from the CFD model with a radar imaging algorithm to simulate the sea surface signature in SAR images. As the plume propagates into a stratified environment, a resonant interaction between the density-driven current and the ambient stratification can lead to internal waves and a fragmentation of the freshwater plume. This fragmentation can be seen as a banding pattern in the simulated radar image of the sea surface. In addition, wind stress leads to directional anisotropy of fine-scale sea surface signatures with respect to the wind direction. The numerical results are consistent with observations of freshwater plumes in the Western Equatorial Pacific during TOGA COARE and observations in the Straits of Florida reported in a companion paper (Soloviev et al., 2011). Internal waves can lead to a signal in the measured electromagnetic field in the ocean. As part of this work, we have also simulated electromagnetic signatures of freshwater plumes and internal waves in the total magnetic field, which potentially provides a link between SAR signatures of transient ocean dynamics and magnetic field fluctuations in the ocean. The novel approach of combining a CFD model with a radar imaging algorithm to investigate the dynamics of small-scale oceanic features and their sea surface signatures in SAR images can be useful for the study and interpretation of a range of near-surface processes, among them freshwater plumes and sharp frontal interfaces, as well as magnetic signatures of oceanic processes.

Matt, S.; Fujimura, A.; Soloviev, A.

2011-12-01

250

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

251

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

NASA Astrophysics Data System (ADS)

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

Sadjadi, Firooz A.

2014-06-01

252

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

NASA Astrophysics Data System (ADS)

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

Rait, Gary L.

1993-08-01

253

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

NASA Astrophysics Data System (ADS)

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

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

1986-02-01

254

Structure of southeastern Antarctic Peninsula ice shelves and ice tongues from synthetic aperture radar imagery  

NASA Astrophysics Data System (ADS)

Examination of synthetic aperture radar data collected over the southeastern Antarctic Peninsula shows that features sometimes mapped as ice shelves are more likely composed of numerous ice tongues interspersed within a matrix of fast ice and icebergs. The tongues are formed by the seaward extension of numerous small mountain glaciers that drain from the Antarctic Peninsula. Once afloat, the tongues intermingle with a matrix of fast ice and brash. Examination of 1997 RADARSAT-1 image mosaics shows that southeastern Antarctic Peninsula composite-ice shelves covered an area of about 3500 km2. Like ice tongues around the rest of Antarctica, these features are highly fragmented and likely to be susceptible to mechanical failure. One such composite shelf, located between New Bedford and Wright Inlets, was observed to decrease in area by 1200 km2 between 1997 and 2000.

Jezek, K. C.; Liu, H. X.

255

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

NASA Technical Reports Server (NTRS)

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

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

1982-01-01

256

Modified log-ratio operator for change detection of synthetic aperture radar targets in forest concealment  

NASA Astrophysics Data System (ADS)

Inherent speckle noise greatly limits the performance of change detection in synthetic aperture radar (SAR) images. In order to reduce the influence of such speckle noise, a modified-log-ratio (MLR) operator for change detection of targets in forest concealment is proposed. By performing a logarithm of the linear transform ratio on the pixel amplitude using multilook processing to generate a difference image, the presented MLR operator is theoretically proven to be capable of improved restraining of the negative effect of speckle noise over the conventional log-ratio operator. A Gaussian distribution of the MLR statistics is assumed, which facilitates the adaptive detection of targets using a constant false alarm rate technique. Experimental results based on the public VHF-band CARABAS-II SAR image dataset validate the effectiveness of the proposed operator.

Gao, Gui; Wang, Xiaoyang; Niu, Min; Zhou, Shilin

2014-01-01

257

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

NASA Technical Reports Server (NTRS)

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

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

1983-01-01

258

Surface displacement of the March 26, 1997 Kagoshima-ken-hokuseibu earthquake in Japan from synthetic aperture radar interferometry  

Microsoft Academic Search

A JERS 1 differential L-band synthetic aperture radar (SAR) interferogram of the March 26, 1997 Kagoshima-ken-hokuseibu earthquake (Mw=6.1) in southwestern Japan shows about 9 cm peak-to-peak coseismic surface displacement in the radar line-of-sight (LOS) direction. A permanent GPS array detected 1 to 2 cm horizontal displacements from this earthquake. By inverting the SAR and GPS data together, we estimated a

Satoshi Fujiwara; Hiroshi Yarai; Shinzaburo Ozawa; Mikio Tobita; Masaki Murakami; Hiroyuki Nakagawa; Koh Nitta; Paul A. Rosen; Charles L. Werner

1998-01-01

259

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

Microsoft Academic Search

The 14 November 2001, Mw = 7.8, Kokoxili earthquake ruptured more than 400 km of the westernmost stretch of the left-lateral Kunlun fault in northern Tibet. Interferometric synthetic aperture radar data from descending orbits, along four adjacent tracks covering almost the entire rupture, and 1-m pixel Ikonos satellite images are used to map the rupture geometry and the surface displacements

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

2005-01-01

260

Time Reversal Synthetic Aperture Radar Imaging In Multipath Yuanwei Jin, Jose M.F. Moura, and Nicholas O'Donoughue  

E-print Network

Michael T. Mulford and Alphonso A. Samuel Raytheon Missile Systems Tucson, AZ 85734 Abstract Conventional spotlight Synthetic Aperture Radar (SAR) assumes a single reflection of transmitted waveforms from targets in conventional SAR images, which obscures true target image and leads to poor resolution. In this paper, we

Moura, José

261

Advanced interferometric synthetic aperture radar (InSAR) time series analysis using interferograms of multiple-orbit  

E-print Network

Advanced interferometric synthetic aperture radar (InSAR) time series analysis using interferograms. To obtain details of such deformation, we developed an advanced InSAR time series analysis using. Additionally, this analysis can combine interferograms for different incidence angles. In a case study

Fialko, Yuri

262

A Mathematical Observation On Synthetic Aperture Radar Yufeng Caoa, Shuxia Lia, Juan Lopeza, Alex Martineza, and Zhijun Qiaoa  

E-print Network

78539 USA ABSTRACT A general synthetic aperture radar (SAR) signal model is derived based on the Maxwells equation, and three numerical simulations are analyzed and discussed. With this signal model, compressive sensing is applied to get a better image. Keywords: compressed sensing, SAR, Maxwell's equations 1

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

263

Volcano-wide fringes in ERS synthetic aperture radar interferograms of Etna (1992-1998): Deformation or tropospheric effect?  

Microsoft Academic Search

Mount Etna (3300 m) is the volcano that has been first and most studied by differential synthetic aperture radar. Previous papers gave evidence for a large-scale deformation of the entire edifice consistent with unrest episodes but with a poor fit with classical elastic models. Also, atmospheric effects on mountainous areas are known to be very significant. Accordingly, interferograms may reflect

François Beauducel; Pierre Briole; Jean-Luc Froger

2000-01-01

264

Develop and Demonstrate Real-Time Wavelet Based Automatic Target Recognition Using Sonar and Synthetic Aperture Radar (SAR) Data.  

National Technical Information Service (NTIS)

The DARPA project, 'Develop and Demonstrate Real-Time Wavelet Based Automatic Target Recognition Using Sonar and Synthetic Aperture Radar (SAR) data' was initiated March 30,1998 with a kick-off meeting attended by personnel from Rice University CML, North...

P. Haley

2001-01-01

265

High voltage technology for a Traveling Wave Tube Electronic Power Conditioner (TWT-EPC) for a Synthetic Aperture Radar (SAR)  

Microsoft Academic Search

A satellite-borne synthetic aperture radar system with an output power of 5 to 20 kW was studied to determine electronic power conditioning (EPC) requirements. The EPC technology is described. The selection of the insulating materials, the test procedures, and switching principles for an emitting amplifier tube are reviewed. The electrical and mechanical load limits and the thermal criteria relative to

K. H. Geissler; R. Bernhard; R. Seeliger

1985-01-01

266

Estimation of discharge from three braided rivers using synthetic aperture radar satellite imagery: Potential application to ungaged basins  

Microsoft Academic Search

Analysis of 41 ERS 1 synthetic aperture radar images and simultaneous ground measurements of discharge for three large braided rivers indicates that the area of active flow on braided river floodplains is primarily a function of discharge. A power law correlation is found between satellite-derived effective width We and discharge Q, where We is the water surface area within a

Laurence C. Smith; Bryan L. Isacks; Arthur L. Bloom; A. Brad Murray

1996-01-01

267

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

268

Detection of target scattering centers in terrain clutter using an ultra-wideband, fully-polarimetric synthetic aperture radar  

Microsoft Academic Search

We study the processing of full-polarization data collected by an ultra-wideband synthetic aperture radar in order to detect targets embedded in terrain clutter. We focus on the use of polarization diversity in a high resolution application to incorporate partial knowledge of the target into the detector design and to model geometrically relevant unknown parameters. We consider a family of generalized

Ronald Louis Dilsavor

1993-01-01

269

Measurement of surface currents using sequential synthetic aperture radar images of slick patterns near the edge of the Gulf Stream  

Microsoft Academic Search

Two-dimensional surface currents are estimated over an area of 00100 kmnear the inshore edge of the Gulf Stream by correlating the surface slick patterns observed on two synthetic aperture radar (SAR) images collected about 20 min apart. The currents obtained from this analysis are found to agree well with shipboard acoustic Doppler current profiler (ADCP) measurements at 10 to 20-m

David R. Lyzenga; George O. Marmorino

1998-01-01

270

Estimation of Discharge From Three Braided Rivers Using Synthetic Aperture Radar Satellite Imagery: Potential Application to Ungaged Basins  

Microsoft Academic Search

Analysis of 41 ERS 1 synthetic aperture radar images and simultaneous ground measurements of discharge for three large braided rivers indicates that the area of active flow on braided river floodplains is primarily a function of discharge. A power law correlation is found between satellite-derived effective width We and discharge Q, where We is the water surface area within a

Laurence C. Smith; Bryan L. Isacks; Arthur L. Bloom; A. Brad Murray

1996-01-01

271

Model-based principal component techniques for detection of buried landmines in multiframe synthetic aperture radar images  

Microsoft Academic Search

Here we consider the use of model-based methods for the detection of buried objects from a sequence of synthetic aperture images obtained by a radar sensor moving linearly down a track. The scattering physics of the underlying sensing modality cause the relevant target signatures to change in a complex yet predictable manner from one image to the next. To arrive

Jie Cheng; Eric Miller

2002-01-01

272

A parametric scheme for the retrieval of two-dimensional ocean wave spectra from synthetic aperture radar look cross spectra  

Microsoft Academic Search

A parametric inversion scheme for the retrieval of two-dimensional (2-D) ocean wave spectra from look cross spectra acquired by spaceborne synthetic aperture radar (SAR) is presented. The scheme uses SAR observations to adjust numerical wave model spectra. The Partition Rescaling and Shift Algorithm (PARSA) is based on a maximum a posteriori approach in which an optimal estimate of a 2-D

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

2005-01-01

273

A user-friendly system for synthetic aperture radar image classification based on grayscale distributional properties and context  

Microsoft Academic Search

The purpose of this paper is to present a system for the analysis and classification of Synthetic Aperture Radar (SAR) images. This system, unlike most of its competitors, allows a careful modeling of the statistical properties of the data beyond the usual Gaussian hypothesis. The modeling tools include basic descriptive measures and the choice of suited distributions, through goodness-of-fit tests,

Alejandro C. Frery; Corina Da C. F. Yanasse; Pedro R. Vieira; S. J. S. Santanna; Camilo D. Rennó

1997-01-01

274

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

SciTech Connect

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

Jakowatz, C.V. Jr.; Wahl, D.E. (Sandia National Laboratories, Albuquerque, New Mexico 87815 (United States))

1993-12-01

275

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

SciTech Connect

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

Hicks, M.J.

1996-01-01

276

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

277

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

NASA Astrophysics Data System (ADS)

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

Marechal, Nicholas; Dickinson, Richard; Karamyan, Grant

2013-05-01

278

Developing a small multi frequency synthetic aperture radar for UAS operation: the SlimSAR  

NASA Astrophysics Data System (ADS)

The SlimSAR is a small, low-cost, Synthetic Aperture Radar (SAR) and represents a new advancement in high-performance SAR. ARTEMIS employed a unique design methodology in designing the SlimSAR that exploits previous developments. The system is designed to be smaller, lighter, and more flexible while consuming less power than typical SAR systems. The system consists of an L-band core and frequency block converters and is very suitable for use on a number of small UAS's. Both linear-frequency-modulated continuous-wave (LFM-CW) and pulsed modes have been tested. The LFM-CW operation achieves high signal-to-noise ratio while transmitting with less peak power than a comparable pulsed system. The flexible control software allows us to change the radar parameters in flight. The system has a built-in high quality GPS/IMU motion measurement solution and can also be packaged with a small data link and a gimbal for high frequency antennas. Multi-frequency SAR provides day and night imaging through smoke, dust, rain, and clouds with the advantages of additional capabilities at different frequencies (i.e. dry ground and foliage penetration at low frequencies, and change detection at high frequencies.)

Zaugg, Evan; Edwards, Matthew; Margulis, Alex

2010-04-01

279

The Analysis of Moonborne Cross Track Synthetic Aperture Radar Interferometry for Global Environment Change Monitoring  

NASA Astrophysics Data System (ADS)

Faced to the earth observation requirement of large scale global environment change, a SAR (Synthetic Aperture Radar) antenna system is proposed to set on Moon's surface for interferometry in this paper. With several advantages superior to low earth obit SAR, such as high space resolution, large range swath and short revisit interval, the moonborne SAR could be a potential data resource of global changes monitoring and environment change research. Due to the high stability and ease of maintenance, the novel system is competent for offering a long and continuous time series of remote sensing imagery. The Moonborne SAR system performance is discussed at the beginning. Then, the peculiarity of interferometry is analyzed in both repeat pass and single pass cases. The chief distinguishing feature which is worth to research the potentiality of repeat pass interferometry is that the revisit interval is reduced to one day in most cases, and in worst case one month. Decorrelation deriving from geometry variety is discussed in detail. It turns out that the feasibility of moonborne SAR repeat pass interferometry depends on the declination of Moon. The severity of shift effects in radar echoes increased as Moon approaches to the equatorial plane. Moreover, referring to the single pass interferometry, two antennas are assumed to set on different latitude of Moon. There is enough space on Moon to form a long baseline, which is highly related to the interferogram precision.

Yixing, Ding; Huadong, Guo; Guang, Liu; Daowei, Zhang

2014-03-01

280

A method for retrieving the directional ocean wave spectra from synthetic aperture radar image  

NASA Astrophysics Data System (ADS)

Directional ocean wave spectra can describe the energy distribution of ocean wave and play an important role in oceanography. Synthetic aperture radar (SAR) can measure wave spectra based on a nonlinear mapping model between the image spectra (or cross spectra) and wave spectra. Due to the complexity of variable estimation and wave number cut off in azimuth direction in the mapping process, some scientists have been endeavoring to improve the retrieval of wave spectra. The paper proposes a method for the retrieval, which don't depend on any external information except wind direction. It separates into two parts. In part 1, the spectra for real image or the cross spectra for complex image are calculated. And the modulation transfer function (MTF) is estimated including real aperture radar (RAR) MTF and velocity bunching. Then the wave spectra are retrieved by direct dividing based on the quasi-linear relation. The 180° ambiguity is removed from the imaginary part of cross spectra or the wind direction. The significant wave height (Hs), peak wave wavelength (L) and peak wave direction (D) are extracted from the retrieval. If the angle between the D and the azimuth direction is higher than 45°, the retrieval is finished. If the angle is lower than 45°, we go on retrieving. In part 2, the first guess spectra are needed to compensate the lost wave information, which can be parametrically constructed based on the retrieved wave spectra in part 1. Finally the wave spectra are iteratively retrieved from the first guess spectra based on the nonlinear relation. The Envisat ASAR images are used to validate the method. In case 1, the RMSE between this method and SARTool on D, L, Hs is 7.6°, 19.7 m, 0.18 m respectively. In case 2, the RMSE between this method and Jason-1 on Hs is 0.5 m.

Ren, Lin; Yang, Jingsong; Chen, Peng

2012-09-01

281

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

282

Optimized algorithm for synthetic aperture imaging  

Microsoft Academic Search

We present a novel synthetic aperture imaging algorithm based on concepts used in synthetic aperture radar (SAR) and sonar (SAS). The algorithm, based on a convolution model of the imaging system developed in the frequency domain, accounts for the beam-pattern of the finite sized transducer used in the synthetic aperture. A 2D Fourier transform is used for the calculation of

T. Stepinski; F. Lingvall

2004-01-01

283

Azimuth smearing in ocean-synthetic aperture radar image spectra: A study of Hasselmann's closed-form transformation based on Norwegian Continental Shelf Experiment 1988 synthetic aperture radar data  

Microsoft Academic Search

The well-known along-track resolution loss in synthetic aperture radar (SAR) ocean wave image spectra is investigated comparing simulations based on Hasselmann's nonlinear integral transform and measurements from the Norwegian Continental Shelf Experiment 1988 experiment. In the literature the resolution loss has often been modeled as a low-pass filter process, described by the rms azimuth shift width sigmax, acting within a

K. A. Høgda; S. Jacobsen; H. E. Krogstad; G. Engen

1993-01-01

284

Azimuth smearing in ocean–synthetic aperture radar image spectra: A study of Hasselmann's closed-form transformation based on Norwegian Continental Shelf Experiment 1988 synthetic aperture radar data  

Microsoft Academic Search

The well-known along-track resolution loss in synthetic aperture radar (SAR) ocean wave image spectra is investigated comparing simulations based on Hasselmann's nonlinear integral transform and measurements from the Norwegian Continental Shelf Experiment 1988 experiment. In the literature the resolution loss has often been modeled as a low-pass filter process, described by the rms azimuth shift width rr x, acting within

K. A. Høgda; S. Jacobsen; H. E. Krogstad; G. Engen

1993-01-01

285

Coseismic deformation of the 2002 Denali fault earthquake: Contributions from synthetic aperture radar range offsets  

NASA Astrophysics Data System (ADS)

We investigate coseismic deformation from the 2002 Denali fault earthquake using synthetic aperture radar (SAR) range offsets. Through a cross-correlation technique, we form a range offset map from two radar amplitude images. A profile across the fault at the Trans-Alaska Pipeline shows right-lateral strike-slip and displacement values that agree with predictions from a GPS-based slip model to within the uncertainty of the range offset data. Using a fixed strike-slip/dip-slip ratio taken from geologic measurements, we derive a lateral slip estimate from the range offsets. This slip estimate shows that the largest geologic offset measurement in a region most accurately represents the full slip value. We then invert a combination of the range offsets, GPS data, and geologic surface offset data to solve for the slip distribution on a three-dimensional fault model in an elastic half-space. The combined model displays highly variable slip, with values generally increasing from west to east along the Denali fault, as well as four major patches of high slip on that fault. As expected, the combined model is nearly identical to the GPS-based model outside the SAR coverage area. Within the coverage area, however, the combined model has better constraints and predicts slip values much closer to the geologic measurements. The offset map displays asymmetrical displacements across the fault. We show that a combination of a bending fault, variable slip, and the SAR line-of-sight geometry can explain this asymmetry. We also discuss how fault geometry influences slip and moment release along the rupture.

Elliott, Julie L.; Freymueller, Jeffrey T.; Rabus, Bernhard

2007-06-01

286

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

287

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

288

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

289

Focusing of synthetic aperture radar ocean images with long integration times  

NASA Astrophysics Data System (ADS)

Synthetic aperture radar (SAR) images obtained in the SAR and X Band Ocean Nonlinearities: Chesapeake Light Tower (SAXON:CLT) experiment are processed with long integration times (6 s) and analyzed to study the effects of focusing. Two images with near-azimuth-traveling waves were chosen for the study. The first image consists of relatively short wavelength wind waves traveling in the same general direction as the aircraft. The second image consists of a long Atlantic swell traveling in the opposite direction to the aircraft. At these long integration times the image spectral intensities are found to be sensitive to the focus setting. The spectral intensity at the optimum focus is 400% of that at zero focus for the first image and 167% for the second image. The focusing curves for both images agree well with those predicted by a model developed by several groups and referred to here as the "consensus" model. This model predicts an optimum focus setting that is equal to one half of the effective phase speed of the dominant wave in the azimuth direction. The velocity bunching model underpredicts the optimum focus setting significantly. The study concludes that in long-integration-time SAR processing of surface waves, such as the spotlight mode, the image contrast is sensitively dependent on the focus setting and that the optimum focus setting is given by one half of the effective phase speed of the dominant surface wave.

Kasilingam, Dayalan P.; Hayt, David W.; Shemdin, Omar H.

1991-09-01

290

A Fast Level Set Method for Synthetic Aperture Radar Ocean Image Segmentation  

PubMed Central

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

Huang, Xiaoxia; Huang, Bo; Li, Hongga

2009-01-01

291

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

PubMed

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

Mingolla, Ennio; Ross, William; Grossberg, Stephen

1999-04-01

292

Change detection in synthetic aperture radar images based on image fusion and fuzzy clustering.  

PubMed

This paper presents an unsupervised distribution-free change detection approach for synthetic aperture radar (SAR) images based on an image fusion strategy and a novel fuzzy clustering algorithm. The image fusion technique is introduced to generate a difference image by using complementary information from a mean-ratio image and a log-ratio image. In order to restrain the background information and enhance the information of changed regions in the fused difference image, wavelet fusion rules based on an average operator and minimum local area energy are chosen to fuse the wavelet coefficients for a low-frequency band and a high-frequency band, respectively. A reformulated fuzzy local-information C-means clustering algorithm is proposed for classifying changed and unchanged regions in the fused difference image. It incorporates the information about spatial context in a novel fuzzy way for the purpose of enhancing the changed information and of reducing the effect of speckle noise. Experiments on real SAR images show that the image fusion strategy integrates the advantages of the log-ratio operator and the mean-ratio operator and gains a better performance. The change detection results obtained by the improved fuzzy clustering algorithm exhibited lower error than its preexistences. PMID:21984509

Gong, Maoguo; Zhou, Zhiqiang; Ma, Jingjing

2012-04-01

293

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

NASA Astrophysics Data System (ADS)

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

Lin, Xiaohong; Xue, Guoyi; Liu, Peiguo

2013-10-01

294

Synthetic aperture radar data visualization on the iPod Touch  

NASA Astrophysics Data System (ADS)

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

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

2010-04-01

295

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

NASA Astrophysics Data System (ADS)

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

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

2009-12-01

296

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

297

Penetration depth of interferometric synthetic-aperture radar signals in snow and ice  

NASA Astrophysics Data System (ADS)

Digital elevation models of glaciated terrain produced by the NASA/Jet Propulsion Laboratory (JPL) airborne interferometric synthetic-aperture radar (InSAR) instrument in Greenland and Alaska at the C- (5.6 cm wavelength) and L-band (24-cm) frequencies were compared with surface elevation measured from airborne laser altimetry to estimate the phase center of the interferometric depth, or penetration depth, ?p. On cold polar firn at Greenland summit, ?p = 9±2m at C- and 14±4m at L-band. On the exposed ice surface of Jakobshavn Isbrae, west Greenland, ?p = 1±2 m at C- and 3±3 m at L-band except on smooth, marginal ice where ?p=15±5 m. On colder marginal ice of northeast Greenland, ?p reaches 60 to 120 m at L-band. On the temperate ice of Brady Glacier, Alaska, ?p is 4±2 m at C-and 12±6 m at L-band, with little dependence on snow/ice conditions. The implications of the results on the scientific use of InSAR data over snow/ice terrain is discussed.

Rignot, Eric; Echelmeyer, Keith; Krabill, William

298

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

USGS Publications Warehouse

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

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

2001-01-01

299

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

300

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

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

301

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

NASA Astrophysics Data System (ADS)

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

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

2009-05-01

302

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

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

303

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

304

C- and Multiangle Ku-Band Synthetic Aperture Radar Data for Bare Soil Moisture Estimation in Agricultural Areas  

Microsoft Academic Search

A sensitivity analysis of C-band (5.3 GHz) and Ku-band (14.85 GHz) synthetic aperture radar (SAR) data to the bare soil moisture content of agricultural fields was conducted in this study. The C-band data were obtained with a 23° incidence angle, whereas the Ku-band data were obtained with 35°, 55°, and 75° incidence angles. The fields presented either a small-scale or

E. E. Sano; M. S. Moran; A. R. Huete; T. Miura

1998-01-01

305

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

Microsoft Academic Search

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

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

2001-01-01

306

Development of polarization selective corner reflectors and its experiment for calibration of airborne polarimetric synthetic aperture radar  

Microsoft Academic Search

As a part of polarimetric calibration efforts of CRL\\/NASDA airborne synthetic aperture radar system (Pi-SAR), we have developed corner reflectors to reflect a specific polarization channel. They include a 45° rotated dihedral, a 22.5° rotated dihedral, and a dihedral made of thin wires placed in the direction of polarization to be reflected, horizontal (H) or vertical (V). The wire-aligned dihedral

Makoto Satake; Toshihiko Umehara; Akitsugu Nadai; Hideo Maeno; Seiho Uratsuka; Takeshi Matsuoka; Hiroaki Honma

2001-01-01

307

Aseismic deformation of a fold-and-thrust belt imaged by synthetic aperture radar interferometry near Shahdad, southeast Iran  

Microsoft Academic Search

At depth, many fold-and-thrust belts are composed of a gently dipping, basal thrust fault and steeply dipping, shallower splay faults that terminate beneath folds at the surface. Movement on these buried faults is difficult to observe, but synthetic aperture radar (SAR) interferometry has imaged slip on at least 600 km2 of the Shahdad basal-thrust and splay-fault network in southeast Iran.

Eric J. Fielding; Tim J. Wright; Jordan Muller; Barry E. Parsons; Richard Walker

2004-01-01

308

Aseismic deformation of a fold-and-thrust belt imaged by synthetic aperture radar interferometry near Shahdad, southeast Iran  

Microsoft Academic Search

At depth, many fold-and-thrust belts are composed of a gently dipping, basal thrust fault and steeply dipping, shallower splay faults that terminate beneath folds at the sur- face. Movement on these buried faults is difficult to observe, but synthetic aperture radar (SAR) interferometry has imaged slip on at least 600 km2 of the Shahdad basal-thrust and splay-fault network in southeast

Eric J. Fielding; Tim J. Wright; Jordan Muller; Barry E. Parsons; Richard Walker

2004-01-01

309

Detection and Identification of Archaeological Sites and Features Using Synthetic Aperture Radar (SAR) Data Collected from Airborne Platforms  

Microsoft Academic Search

Protocols for archaeological inventory of large areas using synthetic aperture radar (SAR) are presented here. They were developed\\u000a during a 2002–2005 research project sponsored by a Department of Defense Strategic Environmental Research and Development\\u000a Program Research Project (SERDP CS-1260) on San Clemente Island, California. Archaeological evidence has established that\\u000a San Clemente Island has been occupied for almost 10,000 years. Some

DOUGLAS C. COMER; RONALD G. BLOM

310

Estimation of Discharge From Three Braided Rivers Using Synthetic Aperture Radar Satellite Imagery: Potential Application to Ungaged Basins  

Microsoft Academic Search

Analysis of 41 ERS 1 synthetic aperture radar images and simultaneous ground measurements of discharge for three large braided rivers indicates that the area of active flow on braided riverfloodplains is primarily a function of discharge. A power law correlation is found between satellite-derived effective widthWe and dischargeQ, where We is the water surface area within a braided reach divided

Laurence C. Smith; Bryan L. Isacks; Arthur L. Bloom; A. Brad Murray

1996-01-01

311

A quasi-parametric algorithm for synthetic aperture radar target feature extraction and imaging with angle diversity  

Microsoft Academic Search

We present synthetic aperture radar (SAR) target feature extraction and imaging techniques with angle divesity. We first establish a flexible data model that describes each target scatterer as a two-dimensional (2D) complex sequence with arbitrary amplitude and constant phase in range and cross-range. A new algorithm, referred to as the QUasiparametric ALgorithm for target feature Extraction (QUALE), is then presented

Junzheng Man; Guoqing Liu; Jian Li; Rob Williams

2000-01-01

312

Transient ultra wide band measurement applications: radar cross section, synthetic aperture radar, electromagnetic compatibility  

Microsoft Academic Search

The Electronic Armament Centre (CELAR: Centre d'Electronique de L'Armement) and the Research Institute of Microwave and Optical Communications (IRCOM: Institut de Recherches en Communications Optiques et Micro-ondes) has evaluated the use of ultra-wide-band (UWB) short pulse measurement facilities to characterize target electromagnetic signatures. A first device is capable of determining the radar cross section (RCS) within a 200 MHz to

J. Andrieu; C. Dubois; M. Lalande; V. Bertrand; P. Delmote; B. Beillard; E. Martinod; B. Jecko; R. Guilleret; F. Monnier; M. Legoff

2003-01-01

313

Temporal Stability of Soil Moisture and Radar Backscatter Observed by the Advanced Synthetic Aperture Radar (ASAR)  

Microsoft Academic Search

The high spatio-temporal variability of soil moisture is the result of atmospheric forcing and redistribution processes related to terrain, soil, and vegetation characteristics. Despite this high variability, many field studies have shown that in the temporal domain soil moisture measured at specific locations is correlated to the mean soil moisture content over an area. Since the measurements taken by Synthetic

Wolfgang Wagner; Carsten Pathe; Marcela Doubkova; Daniel Sabel; Annett Bartsch; Stefan Hasenauer; Günter Blöschl; Klaus Scipal; José Martínez-Fernández

2008-01-01

314

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

315

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

NASA Astrophysics Data System (ADS)

Flooding is a particular hazard in urban areas worldwide due to the increased risks to life and property in these regions. Synthetic Aperture Radar (SAR) sensors are often used to image flooding because of their all-weather day-night capability, and now possess sufficient resolution to image urban flooding. The flood extents extracted from the images may be used for flood relief management and improved urban flood inundation modelling. 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. This paper investigates whether urban flooding can be detected in layover regions (where flooding may not normally be apparent) using double scattering between the (possibly flooded) ground surface and the walls of adjacent buildings. The method estimates double scattering strengths using a SAR image in conjunction with a high resolution LiDAR (Light Detection and Ranging) 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.

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

2014-05-01

316

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

NASA Technical Reports Server (NTRS)

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

Sader, Steven A.

1987-01-01

317

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

NASA Astrophysics Data System (ADS)

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

Smith, R. C.

2006-12-01

318

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

NASA Technical Reports Server (NTRS)

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

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

1994-01-01

319

Ocean Observer Synthetic Aperture Radar User and Instrument Requirements and Configuration  

NASA Astrophysics Data System (ADS)

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

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

2002-12-01

320

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

NASA Astrophysics Data System (ADS)

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

Fallahpour, Mojtaba

321

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

NASA Astrophysics Data System (ADS)

While conventional interferometric synthetic aperture radar (InSAR) is a very effective technique for measuring crustal deformation, almost any interferogram includes large areas where the signals decorrelate and no measurement is possible. Persistent scatterer (PS) InSAR overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms. Existing PS methods have been very successful in analysis of urban areas, where stable angular structures produce efficient reflectors that dominate background scattering. However, man-made structures are absent from most of the Earth's surface. Furthermore, existing methods identify PS pixels based on the similarity of their phase history to an assumed model for how deformation varies with time, whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study. We describe here a method for PS analysis, StaMPS, that uses spatial correlation of interferogram phase to find pixels with low-phase variance in all terrains, with or without buildings. Prior knowledge of temporal variations in the deformation rate is not required for their identification. We apply StaMPS to Volcán Alcedo, where conventional InSAR fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time. We detect two sources of deformation. The first we model as a contracting pipe-like body, which we interpret to be a crystallizing magma chamber. The second is downward and lateral motion on the inner slopes of the caldera, which we interpret as landsliding.

Hooper, A.; Segall, P.; Zebker, H.

2007-07-01

322

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

NASA Astrophysics Data System (ADS)

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

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

2005-05-01

323

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

Microsoft Academic Search

This report summarizes the work performed for the Office of the Chief of Naval Research (ONR) during the period of 1 September 1997 through 31 December 1997. The primary objective of this research was aimed at developing an alternative time-frequency approach which is recursive-in-time to be applied to the Inverse Synthethic Aperture Radar (ISAR) imaging problem discussed subsequently. Our short

Candy

1997-01-01

324

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

325

Salt-dissolution-induced subsidence in the Dead Sea area detected by applying interferometric techniques to ALOS Palsar Synthetic Aperture Radar images  

Microsoft Academic Search

This paper discusses the interpretation of ground motions detected in the dried up Lynch Strait, Dead Sea area, by applying radar interferometric techniques to ALOS Palsar Synthetic Aperture Radar images. Four ALOS scenes spanning from December 15, 2007 to May 17, 2008 have been processed leading to the generation of five interferograms. Three ground deformation zones have been detected. One

Damien Closson; Najib Abou Karaki; Nada Milisavljevic; Frédéric Hallot; Marc Acheroy

2010-01-01

326

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

327

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

328

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

329

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

330

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

331

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

NASA Technical Reports Server (NTRS)

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

Mader, G. L.

1981-01-01

332

Design and development of control software in the experiment system of synthetic aperture laser imaging radar  

NASA Astrophysics Data System (ADS)

A control software experiment system of synthetic aperture imaging ladar is developed based on multithreading parallel mechanism of Labview8.6 and SCPI (standard commands for programmable instruments) protocol. Firstly, hardware composition and software function requirement of the system are analyzed. Then, the control module of the laser and stepper motor and the data communication module of oscillograph are developed separately and the three modules are integrated to realize the gather and compute of the return signal. Finally, by the result of experiment, the control software worked steady and real timely and it can operate the laser, stepper motor and oscillograph successfully.

Wu, Yapeng; Zhou, Yu; Zhi, Ya'nan; Sun, Jianfeng; Lu, Wei; Liu, Liren

2010-08-01

333

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

NASA Astrophysics Data System (ADS)

Interferometric inverse synthetic aperture radar (InISAR) imaging provides complementary information to monostatic inverse synthetic aperture radar (ISAR) imaging. This paper proposes a new InISAR imaging system for space targets based on wideband direct sampling using two antennas. The system is easy to realize in engineering since the motion trajectory of space targets can be known in advance, which is simpler than that of three receivers. In the preprocessing step, high speed movement compensation is carried out by designing an adaptive matched filter containing speed that is obtained from the narrow band information. Then, the coherent processing and keystone transform for ISAR imaging are adopted to reserve the phase history of each antenna. Through appropriate collocation of the system, image registration and phase unwrapping can be avoided. Considering the situation not to be satisfied, the influence of baseline variance is analyzed and compensation method is adopted. The corresponding size can be achieved by interferometric processing of the two complex ISAR images. Experimental results prove the validity of the analysis and the three-dimensional imaging algorithm.

Tian, Biao; Liu, Yang; Xu, Shiyou; Chen, Zengping

2014-01-01

334

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

NASA Astrophysics Data System (ADS)

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

Moon, Wooil M.

335

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

NASA Technical Reports Server (NTRS)

The Spaceborne Imaging Radar-C/X-band Synthetic Aperture Radar (SIR-C/X-SAR) is the most advanced imaging radar system to fly in Earth orbit. Carried in the cargo bay of the Space Shuttle Endeavour in April and October of 1994, SIR-C/X-SAR simultaneously recorded SAR data at three wavelengths (L-, C-, and X-bands; 23.5, 5.8, and 3.1 cm, respectively). The SIR-C/X-SAR Science Team consists of 53 investigator teams from more than a dozen countries. Science investigations were undertaken in the fields of ecology, hydrology, ecology, and oceanography. This report contains 44 investigator team reports and several additional reports from coinvestigators and other researchers.

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

1996-01-01

336

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

337

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

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

338

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

339

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

SciTech Connect

This report summarizes the work performed for the Office of the Chief of Naval Research (ONR) during the period of 1 September 1997 through 31 December 1997. The primary objective of this research was aimed at developing an alternative time-frequency approach which is recursive-in-time to be applied to the Inverse Synthethic Aperture Radar (ISAR) imaging problem discussed subsequently. Our short term (Phase I) goals were to: 1. Develop an ISAR stepped-frequency waveform (SFWF) radar simulator based on a point scatterer vehicular target model incorporating both translational and rotational motion; 2. Develop a parametric, recursive-in-time approach to the ISAR target imaging problem; 3. Apply the standard time-frequency short-term Fourier transform (STFT) estimator, initially to a synthesized data set; and 4. Initiate the development of the recursive algorithm. We have achieved all of these goals during the Phase I of the project and plan to complete the overall development, application and comparison of the parametric approach to other time-frequency estimators (STFT, etc.) on our synthesized vehicular data sets during the next phase of funding. It should also be noted that we developed a batch minimum variance translational motion compensation (TMC) algorithm to estimate the radial components of target motion (see Section IV). This algorithm is easily extended to recursive solution and will probably become part of the overall recursive processing approach to solve the ISAR imaging problem. Our goals for the continued effort are to: 1. Develop and extend a complex, recursive-in-time, time- frequency parameter estimator based on the recursive prediction error method (RPEM) using the underlying Gauss- Newton algorithms. 2. Apply the complex RPEM algorithm to synthesized ISAR data using the above simulator. 3. Compare the performance of the proposed algorithm to standard time-frequency estimators applied to the same data sets.

Candy, J.V., LLNL

1997-12-31

340

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

341

Interferometric synthetic aperture radar (InSAR) atmospheric correction: GPS, Moderate Resolution Imaging Spectroradiometer (MODIS), and InSAR integration  

NASA Astrophysics Data System (ADS)

Atmospheric effects represent one of the major limitations of repeat-pass interferometric synthetic aperture radar (InSAR). In this paper, GPS, and Moderate Resolution Imaging Spectroradiometer (MODIS) data were integrated to provide regional water vapor fields with a spatial resolution of 1 km × 1 km, and a water vapor correction model based on the resultant water vapor fields was successfully incorporated into the Jet Propulsion Laboratory/California Institute of Technology ROI_PAC software. The advantage of this integration approach is that only one continuous GPS station is required within a 2030 km × 1354 km MODIS scene. Application to ERS-2 repeat-pass data over the Los Angeles Southern California Integrated GPS Network (SCIGN) area shows that this integration approach not only helps discriminate geophysical signals from atmospheric artifacts but also reduces water vapor effects significantly, which is of great interest to a wide community of geophysicists.

Li, Zhenhong; Muller, Jan-Peter; Cross, Paul; Fielding, Eric J.

2005-03-01

342

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

343

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

Microsoft Academic Search

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

Yunling Lou

2002-01-01

344

Estimates of ocean wavelength and direction from X-and L-band synthetic aperture radar data collected during the Marineland experiment  

Microsoft Academic Search

Simultaneously obtainedX- andL-band synthetic aperture radar (SAR) data collected during the Marineland Experiment were spectrally analyzed by fast Fourier transform (FFT) techniques to estimate ocean wavelength and direction. An eight-sided flight pattern was flown over the same ocean area in order to study the sensitivity of the spectral estimate on radar look direction. These spectral estimates were compared with in

ROBERT A. SHUCHMAN; JAMES D. LYDEN; DAVID R. LYZENGA

1983-01-01

345

Application of synthetic aperture radar (SAR) imagery to volcano mapping in the humid tropics: a case study in East Java, Indonesia  

Microsoft Academic Search

Volcanoes in humid tropical environments are frequently cloud covered, typically densely vegetated and rapidly eroded. These factors complicate field and laboratory studies and even the basic identification of potentially active volcanoes. Numerous previous studies have highlighted the potential value of radar remote sensing for volcanology in equatorial regions. Here, cloud- and vegetation-penetrating LHH-band (lambda 24cm) synthetic aperture radar (SAR) data

Simon A. Carn

1999-01-01

346

Application of synthetic aperture radar (SAR) imagery to volcano mapping in the humid tropics: a case study in East Java, Indonesia  

Microsoft Academic Search

Volcanoes in humid tropical environments are frequently cloud covered, typically densely vegetated and rapidly eroded. These\\u000a factors complicate field and laboratory studies and even the basic identification of potentially active volcanoes. Numerous\\u000a previous studies have highlighted the potential value of radar remote sensing for volcanology in equatorial regions. Here,\\u000a cloud- and vegetation-penetrating LHH-band (??24?cm) synthetic aperture radar (SAR) data from

Simon A. Carn

1999-01-01

347

Use of Synthetic Aperture Radar (SAR) for geologic reconnaissance in Arctic regions: An example from the Arctic National Wildlife Refuge, Alaska  

Microsoft Academic Search

Satellite-based synthetic aperture radar (SAR) can provide an additional remote-sensing tool for regional geologic studies in arctic regions. Although SAR data do not yield direct information on rock type and do not replace traditional optical data, SAR data can provide useful geologic information in arctic regions where the stratigraphic column includes a wide range of lithologies, and bedrock exposures have

C. L. Hanks; R. M. Guritz

1997-01-01

348

A study of P-band synthetic aperture radar applicability and performance for Mars exploration: Imaging subsurface geology and detecting shallow moisture  

Microsoft Academic Search

Over the past decade, orbital images of the Martian surface revealed key evidence about the history of the planet environment (craters, faults, paleo-lakes, and rivers), partially hidden under a widespread layer of aeolian deposits. Furthermore, several recent observations and studies support the hypothesis that water could be found in the shallow subsurface of Mars. Low-frequency synthetic aperture radar (SAR) has

Philippe Paillou; Yannick Lasne; Essam Heggy; Jean-Marie Malézieux; Gilles Ruffié

2006-01-01

349

Internal Waves in the Strait of Messina Studied by a Numerical Model and Synthetic Aperture Radar Images from the ERS 1\\/2 Satellites  

Microsoft Academic Search

A new numerical two-layer model is presented, which describes the generation of internal tidal bores and their disintegration into internal solitary waves in the Strait of Messina. This model is used to explain observations made by the synthetic aperture radar (SAR) from the European Remote Sensing satellites ERS 1 and ERS 2. The analysis of available ERS 1\\/2 SAR data

Peter Brandt; Angelo Rubino; Werner Alpers; Jan O. Backhaus

1997-01-01

350

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

E-print Network

.1). These #12;Micr ¤ olocal Structure of HRR ISAR Data 2 two sections serve to introduce our notation-scattering and multiple- scattering cases. 2. Radar data High-range-resolution (HRR) radar systems transmit the equivalent

Cheney, Margaret

351

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

352

An Interferometric Ka-band Synthetic Aperture Radar: A New Technique for Glacier and Ice- sheet Topography Mapping  

NASA Astrophysics Data System (ADS)

The estimation of the mass balance of ice sheets and glaciers on Earth is a problem of considerable scientific and societal importance. The Greenland and Antarctic ice sheets together hold enough ice to raise global sea level by 80 m. The annual exchange of mass on the ice sheets is equivalent to 8mm/yr sea level, so that any fluctuation in that level of exchange is significant on the global scale. A key measurement to understanding, monitoring and forecasting these changes is ice-surface topography, both for ice-sheet and glacial regions. As such NASA identified "ice topographic mapping instruments capable of providing precise elevation and detailed imagery data for measurements on glacial scales for detailed monitoring of ice sheet, and glacier changes" as a science priority for the most recent ESTO- Instrument Incubator Program (IIP) opportunities. Funded under this opportunity is the technological development for a Ka-Band (35GHz) single-pass digitally beamformed interferometric synthetic aperture radar (InSAR). Unique to this concept is the ability to map a significant swath impervious of cloud cover with measurement accuracies comparable to lidar altimeters but with variable resolution as appropriate to the differing scales-of-interest over ice-sheets and glaciers. By diverging from the more traditional profiling measurements employed to date (ie radar altimeters and lidars) we are able to offer the potential to significantly advance the spaciotemporal observational capabilities of both ice sheets and glaciers. Dubbed the Glacier and Land Ice Surface Topography Interferometer (GLISTIN), the instrument and mission presents several significant challenges. In particular, under the IIP program we are designing, building and demonstrating a large Ka-band antenna array with integrated digital receivers and utilizing digital beamforming to preserve both antenna gain and swath. These technology items will ultimately be integrated into a complete interferometric ground-based system and demonstrated from the local JPL mesa antenna range. While the demonstration addresses the key technology hurdles, an additional component to this program is to address the systematic and geophysical calibration issues that will arise for a dedicated mission of this type. We discuss our proposed calibration methodology and present several of the critical issues, including correction of systematic errors and surface and volume decorrelation effects. We conclude with a discussion of the impact of snow penetration on the height measurements, and discuss a proposed campaign to field a Ka-band interferometric synthetic aperture radar based on the Jet Propulsion Laboratory's new "UAVSAR" platform.

Moller, D. K.; Aaron, K.; Gim, Y.; Heavey, B.; Hodges, R.; Nicolson, A.; Rengarajan, S.; Rignot, E.; Rogez, F.; Sadowy, G.; Simard, M.; Zawadzki, M.

2006-12-01

353

Polarimetric synthetic aperture radar study of the Tsaoling landslide generated by the 1999 Chi-Chi earthquake, Taiwan  

NASA Astrophysics Data System (ADS)

We employ L-band airborne synthetic aperture radar (SAR) polarimetry to detect surface changes produced by the Tsaoling landslide, the largest slope failure triggered by the September 1999 Chi-Chi earthquake in central Taiwan. Imaging polarimeters provide a complete description of the scattering properties of radar target materials. Resurfacing of forested hillslopes by landslides alters scattering mechanisms from those dominated by backscatter from trees to mechanisms associated with scatter from rough, bare surfaces. Scattering mechanism information on a per-pixel basis is extracted by decomposing matrices formed as the outer product of the complex scattering vector measured for each resolution cell. We classify surface cover type and thereby identify the extent of the landslide, using such polarimetric parameters as scattering entropy, anisotropy, and pedestal height, derived from the eigenvalues of the decomposition, as well as the weighted average scattering mechanism derived from the eigenvectors. We address the utility of full polarimetry versus dual polarimetry for landslide mapping purposes and show that fully polarimetric SAR is necessary for distinguishing water surfaces of varying roughness from the bare surfaces created by landsliding. We show that scattering entropy and average scattering mechanism, for example, can be used to identify the Tsaoling landslide source, run out area and impounded lakes as proficiently as maps obtained using satellite optical sensors, such as Landsat and the Indian Research Satellite. However, the operational advantages of radar over optical sensing techniques (namely, its day-night, all-weather data acquisition capability) suggest that SAR polarimetry could play a leading role in the rapid assessment of landslide disasters.

Czuchlewski, Kristina R.; Weissel, Jeffrey K.; Kim, Yunjin

2003-12-01

354

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

Microsoft Academic Search

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

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

2010-01-01

355

A method for constraining canopy height using single-polarization L-band Interferometric Synthetic Aperture Radar (InSAR)  

NASA Astrophysics Data System (ADS)

Over the past two decades, interferometric synthetic aperture radar (InSAR) has proven to be a useful technique for observing a wide range of sources of crustal motion, including groundwater extraction and deformation related to volcanic processes and earthquakes. In this study we introduce a new method for the application of InSAR to the determination of canopy height in forests where extensive clearcutting has occurred. Our region of study is the Pacific Northwest, specifically Washington and Oregon, where clearcutting has been a common logging technique since the earliest days of the timber industry in the region. We analyzed twenty-nine interferograms of the Pacific Northwest in this study. The interferograms were processed using single-polarization Synthetic Aperture Radar (SAR) data acquired by the Advanced Land Observation Satellite (ALOS). ALOS data is acquired at L-band (~24 cm), which provides high coherence in a region that is heavily forested and has high relief. Regions that have undergone clearcutting within the past 10 to 15 years are characterized in the interferograms by quasi-rectangular regions of line-of-sight phase change between clearcuts and the surrounding standing forest. This phase difference correlates linearly with interferometric baseline, allowing us to attribute the observed phase difference between clearcut areas and standing forest to an effective digital elevation model (DEM) error. By focusing only on the phase change over the short spatial scale between standing forest and adjacent regions that have been logged, we remove the effect of longer spatial scale atmospheric noise and satellite orbital errors. A ratio of Landsat 5 Thematic Mapper (TM) bands 2 and 7 (0.52-0.60 and 2.08-2.35 ?m, respectively) was used to identify and remove areas that were logged during the timespan of the SAR data (2007 to 2011). We present a map of canopy height throughout the western coast of Oregon and Washington. Observed canopy heights are consistent with local ground surveys and previous remote-sensing studies. Our methods provide an independent measurement of canopy height and will aid in ongoing efforts to constrain the global carbon budget. Estimates of canopy height will likely be improved by the addition of new data through the advent of the next generation of SAR missions, such as the proposed DESDynI mission. These methods will also be useful for removing a prominent non-tectonic signal observed in the Pacific Northwest so that InSAR data will be of more utility in forthcoming tectonic studies.

Prush, V. B.; Lohman, R.

2012-12-01

356

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

357

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

NASA Technical Reports Server (NTRS)

The scientific and engineering requirements for the Earth Observing System (EOS) imaging radar are provided. The radar is based on Shuttle Imaging Radar-C (SIR-C), and would include three frequencies: 1.25 GHz, 5.3 GHz, and 9.6 GHz; selectable polarizations for both transmit and receive channels; and selectable incidence angles from 15 to 55 deg. There would be three main viewing modes: a local high-resolution mode with typically 25 m resolution and 50 km swath width; a regional mapping mode with 100 m resolution and up to 200 km swath width; and a global mapping mode with typically 500 m resolution and up to 700 km swath width. The last mode allows global coverage in three days. The EOS SAR will be the first orbital imaging radar to provide multifrequency, multipolarization, multiple incidence angle observations of the entire Earth. Combined with Canadian and Japanese satellites, continuous radar observation capability will be possible. Major applications in the areas of glaciology, hydrology, vegetation science, oceanography, geology, and data and information systems are described.

1987-01-01

358

Data-Level Fusion of Multilook Inverse Synthetic Aperture Radar Images  

Microsoft Academic Search

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

Zhixi Li; Scott Papson; Ram M. Narayanan

2008-01-01

359

An Approach to Ground Moving Target Indication Using Multiple Resolutions of Multilook Synthetic Aperture Radar Images  

E-print Network

Design . . . . . . . . . . . . . . . . . . . . . . . . . . . 126 6.1.1 MATLAB Radar Model . . . . . . . . . . . . . . . . . . . . . 126 6.1.2 Monte Carlo Simulations . . . . . . . . . . . . . . . . . . . . . 127 6.2 GMTI Using Multilook SAR Images...?cations relating Kalman ?ltering, iterative MMSE, RLS, and back projection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56 3.3 DWT synthesis ?lter bank tree . . . . . . . . . . . . . . . . . . . . . 57 3.4 Haar scaling function and wavelet...

Akers, Geoffrey

2009-12-15

360

Maximum likelihood estimation of point scatterers in synthetic aperture radar data  

Microsoft Academic Search

The motivation for this research is the recognition of objects from the relative locations of radar point scatterers on the object. Point scatterers are modeled as damped exponential signals. Parametric estimation of the exponential parameters determines the point scatterer locations. Maximum likelihood estimation of exponential parameters in white Gaussian noise provides good results in many exponential estimation problems. In fact,

Matthew P. Pepin; Joseph J. Sacchini

1996-01-01

361

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

Microsoft Academic Search

The detection of buried objects, particularly hazardous waste containers and unexploded ordnance (UXO), has gained significant interest in the Unites States in the late 1990s. The desire to remediate the thousands of sites worldwide has become an increasing concern and the application of radar to this problem has received renewed attention. The US Department of Energy's Special Technologies Laboratory (STL),

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

2000-01-01

362

Millimeter-wave Ground-based Synthetic Aperture Radar Imaging for Foreign Object Debris Detection: Experimental Studies at Short Ranges  

NASA Astrophysics Data System (ADS)

In this paper, millimeter-wave imaging of foreign object debris (FOD)-type objects on the ground is studied with the help of ground-based synthetic aperture radar (GB-SAR) technique. To test the feasibility of detecting runway FODs with this technique, some preliminary experiments are conducted within short antenna-to-target ranges of small imaging patches. An automated stripmap GB-SAR system with stepped-frequency transmission is constructed together with a quasi-monostatic data collection operation. The imaging experiments for various braces and screws are then carried out by using 32- 36 GHz and 90- 95 GHz frequency bands of the millimeter-wave. Images reconstructed by a matched-filter based algorithm are analyzed to determine the proper system parameters for an efficient imaging and to comprehend the factors against a successful detection. Results demonstrate the capability of GB-SAR imaging in accurately locating these FOD-like targets under near-range operating conditions.

Yigit, Enes; Demirci, Sevket; Unal, Atilla; Ozdemir, Caner; Vertiy, Alexey

2012-12-01

363

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

364

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

365

A parametric scheme for the retrieval of two-dimensional ocean wave spectra from synthetic aperture radar look cross spectra  

NASA Astrophysics Data System (ADS)

A parametric inversion scheme for the retrieval of two-dimensional (2-D) ocean wave spectra from look cross spectra acquired by spaceborne synthetic aperture radar (SAR) is presented. The scheme uses SAR observations to adjust numerical wave model spectra. The Partition Rescaling and Shift Algorithm (PARSA) is based on a maximum a posteriori approach in which an optimal estimate of a 2-D wave spectrum is calculated given a measured SAR look cross spectrum (SLCS) and additional prior knowledge. The method is based on explicit models for measurement errors as well as on uncertainties in the SAR imaging model and the model wave spectra used as prior information. Parameters of the SAR imaging model are estimated as part of the retrieval. Uncertainties in the prior wave spectrum are expressed in terms of transformation variables, which are defined for each wave system in the spectrum, describing rotations and rescaling of wave numbers and energy as well as changes of directional spreading. Technically, the PARSA wave spectra retrieval is based on the minimization of a cost function. A Levenberg-Marquardt method is used to find a numerical solution. The scheme is tested using both simulated SLCS and ERS-2 SAR data. It is demonstrated that the algorithm makes use of the phase information contained in SLCS, which is of particular importance for multimodal sea states. Statistics are presented for a global data set of 11,000 ERS-2 SAR wave mode SLCS acquired in southern winter 1996.

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

2005-05-01

366

On the retrieval of significant wave heights from spaceborne Synthetic Aperture Radar using the Max-Planck Institut algorithm.  

PubMed

Synthetic Aperture Radar (SAR) onboard satellites is the only source of directional wave spectra with continuous and global coverage. Millions of SAR Wave Mode (SWM) imagettes have been acquired since the launch in the early 1990's of the first European Remote Sensing Satellite ERS-1 and its successors ERS-2 and ENVISAT, which has opened up many possibilities specially for wave data assimilation purposes. The main aim of data assimilation is to improve the forecasting introducing available observations into the modeling procedures in order to minimize the differences between model estimates and measurements. However there are limitations in the retrieval of the directional spectrum from SAR images due to nonlinearities in the mapping mechanism. The Max-Planck Institut (MPI) scheme, the first proposed and most widely used algorithm to retrieve directional wave spectra from SAR images, is employed to compare significant wave heights retrieved from ERS-1 SAR against buoy measurements and against the WAM wave model. It is shown that for periods shorter than 12 seconds the WAM model performs better than the MPI, despite the fact that the model is used as first guess to the MPI method, that is the retrieval is deteriorating the first guess. For periods longer than 12 seconds, the part of the spectrum that is directly measured by SAR, the performance of the MPI scheme is at least as good as the WAM model. PMID:16341447

Violante-Carvalho, Nelson

2005-12-01

367

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

NASA Technical Reports Server (NTRS)

High resolution Esa Remote Sensing Satellite-1 (ERS-1) Synthetic Aperture Radar (SAR) images are used to detect a mesoscale eddy. Such features limit dispersal of pollock larvae and therefore likely influence recruitment of fish in the Gulf of Alaska. During high sea states and high winds, the direct surface signature of the eddy was not clearly visible, but the wave refraction in the eddy area was observed. The rays of the wave field are traced out directly from the SAR image. The ray pattern gives information on the refraction pattern and on the relative variation of the wave energy along a ray through wave current interaction. These observations are simulated by a ray-tracing model which incorporates a surface current field associated with the eddy. The numerical results of the model show that the waves are refracted and diverge in the eddy field with energy density decreasing. The model-data comparison for each ray shows the model predictions are in good agreement with the SAR data.

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

1994-01-01

368

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

NASA Technical Reports Server (NTRS)

The first European remote sensing satellite ERS-1 will be launched by the European Space Agency (ESA) in 1989. The expected lifetime is two to three years. The spacecraft sensors will primarily support ocean investigations and to a limited extent also land applications. Prime sensor is the Active Microwave Instrumentation (AMI) operating in C-Band either as Synthetic Aperture Radar (SAR) or as Wave-Scatterometer and simultaneously as Wind-Scatterometer. In Europe there will be two distinct types of processing for ERS-1 SAR data, Fast Delivery Processing and Precision Processing. Fast Delivery Proceessing will be carried out at the ground stations and up to three Fast Delivery products per pass will be delivered to end users via satellite within three hours after data acquisition. Precision Processing will be carried out in delayed time and products will not be generated until several days or weeks after data acquisition. However, a wide range of products will be generated by several Processing and Archiving Facilities (PAF) in a joint effort coordinated by ESA. The German Remote Sensing Data Center (Deutsches Fernerkundungsdatenzentrum DFD) will develop and operate one of these facilities. The related activities include the acquisition, processing and evaluation of such data for scientific, public and commercial users. Based on this experience the German Remote Sensing Data Center is presently performing a Phase-B study regarding the development of a SAR processor for ERS-1. The conceptual design of this processing facility is briefly outlined.

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

1986-01-01

369

The 1995 Kozani-Grevena (northern Greece) earthquake revisited: an improved faulting model from synthetic aperture radar interferometry  

NASA Astrophysics Data System (ADS)

Previously, geodetic data associated with earthquakes have been widely modelled using co-planar rectangular dislocations in an elastic half-space. However, such models appear inadequate when complex geometries such as variations in strike and dip or multiple fault segments are involved. Here we revisit the 1995 Ms= 6.6 Kozani-Grevena earthquake, and use synthetic aperture radar (SAR) interferometric measurements, tectonic observations and seismological data to constrain a fault model with a realistic geometry. We undertake a critical analysis of all available SAR data, including characterization of atmospheric artefacts. These are partially removed and the possibility that such effects are misidentified as secondary faulting is examined. Three well-correlated interferograms provide an accurate and complete description of the ground deformation field associated with the event. To take into account the complexity of the fault system activated during the earthquake, we construct a 3-D fault model, composed of triangular elements, that is geometrically more consistent with surface ruptures than those of previous studies. Using first trial-and-error and then iterative inversion, we explore the ranges of geometric parameters that can explain the data. We obtain an average final model and its standard deviation, with small slip amplitude at the surface, consistent with the field observations, and with slip as large as 2.5 m at depth. This model is compared with those previously published. We conclude that an antithetic fault is not required to explain the SAR data.

Rigo, Alexis; de Chabalier, Jean-Bernard; Meyer, Bertrand; Armijo, Rolando

2004-05-01

370

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

NASA Technical Reports Server (NTRS)

A technique based on synthetic aperture radar (SAR) interferometry is used to measure very small (1 cm or less) surface deformations with good resolution (10 m) over large areas (50 km). It can be used for accurate measurements of many geophysical phenomena, including swelling and buckling in fault zones, residual, vertical and lateral displacements from seismic events, and prevolcanic swelling. Two SAR images are made of a scene by two spaced antennas and a difference interferogram of the scene is made. After unwrapping phases of pixels of the difference interferogram, surface motion or deformation changes of the surface are observed. A second interferogram of the same scene is made from a different pair of images, at least one of which is made after some elapsed time. The second interferogram is then compared with the first interferogram to detect changes in line of sight position of pixels. By resolving line of sight observations into their vector components in other sets of interferograms along at least one other direction, lateral motions may be recovered in their entirety. Since in general, the SAR images are made from flight tracks that are separated, it is not possible to distinguish surface changes from the parallax caused by topography. However, a third image may be used to remove the topography and leave only the surface changes.

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

1990-01-01

371

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

372

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

373

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

374

Detection of land surface change due to the Wenchuan earthquake using multitemporal advanced land observation satellite-phased array type L-band synthetic aperture radar data  

NASA Astrophysics Data System (ADS)

A strong earthquake, with a magnitude of 8.0, hit in the Wenchuan area of China on May 12, 2008, resulting in significant changes to the land surface. Remote sensing (RS), especially synthetic aperture radar (SAR) RS technology can play a key role in detecting changes of the land surface. In the present paper, multitemporal Advanced Land Observation Satellite- Phased Array type L-band Synthetic Aperture Radar (ALOS-PALSAR) data acquired on Feb. 17 and May 19, 2008 were used to analyze the land surface changes caused by the Wenchuan earthquake. The characteristics of the land surface in several sites hit by the earthquake are presented, by comparison of pre- and post-seismic images. Subsequently, the land surface changes caused by the earthquake were extracted using change detection and classification methods. To this end, land surface change detection can provide a detailed basis for assessing an earthquakes impact.

Liao, Jingjuan; Shen, Guozhuang

2009-05-01

375

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

Microsoft Academic Search

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

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

2007-01-01

376

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

Microsoft Academic Search

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

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

2009-01-01

377

Assessment of ERS synthetic aperture radar wave spectra retrieved from the Max-Planck-Institut (MPI) scheme through intercomparisons of 1 year of directional buoy measurements  

Microsoft Academic Search

One year of directional buoy measurements comprising the period from May 1994 to April 1995 acquired in deep ocean waters by an offshore heave-pitch-roll buoy are used for the assessment of the directional wave spectra retrieved from synthetic aperture radar (SAR) images using the Max-Planck-Institut (MPI) scheme. SAR is the only sensor so far deployed from satellites that can provide

N. Violante-Carvalho; I. S. Robinson; J. Schulz-Stellenfleth

2005-01-01

378

Wind jets and wind waves off the Pacific coast of northern Japan under winter monsoon captured by combined use of scatterometer, synthetic aperture radar, and altimeter  

Microsoft Academic Search

Wind jets and wind waves off the Pacific coast of northern Japan under the east Asian winter monsoon are investigated using scatterometer, synthetic aperture radar (SAR), and altimeters. First, we depict two prevailing wind flow patterns associated with the northwesterly winter monsoon. They are derived by averaging QuikSCAT wind vectors when the 850-hPa pressure level wind directions are within 260°–290°

Teruhisa Shimada; Hiroshi Kawamura

2004-01-01

379

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

Microsoft Academic Search

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

A. O. Kohlhase; R. Kroes; S. D’Amico

2006-01-01

380

Obtaining Titan Surface Heights Using Cassini Synthetic Aperture RADAR Echo Data  

NASA Astrophysics Data System (ADS)

One of the more vexing dilemmas for RADAR remote sensing is the necessity to choose between altimetry and SAR imaging of a surface. For the Cassini RADAR team, coincident surface height estimates would be very useful in aiding the analysis of the unique surface features we have seen in the SAR imagery of Titan. Unfortunately, radar altimetry is optimally obtained from nadir observations; whereas SAR requires off-nadir observation in order to construct an image. Here we discuss a technique for obtaining coarse resolution (50 km horizontal, 200 m vertical) surface height estimates along the center of the SAR swath. The method requires: 1) accurate s/c pointing, 2) accurate s/c ephemeris, 3) accurate Titan orbital information, 4) precise knowledge of the antenna pattern of the RADAR, and 5) down-linked echo data covering the entire antenna footprint. The fourth and fifth requirements are met through synergy with Cassini SAR coverage requirements. Cassini SAR commanding and pointing was designed to utilize as much of the antenna footprint as possible in order to maximize coverage. The accuracy of the surface height estimation technique is adversely affected by backscatter variation within the footprint. This shortcoming is overcome by averaging results from multiple footprints and through human interaction. We describe the technique and present results for those SAR passes for which its requirements are met. We then validate the technique by comparing the results with a geological analysis of the coincident SAR images. This work was performed at the Jet Propulsion Laboratory, California Institute of Technology under contract with the National Aeronautics and Space Administration.

Stiles, Bryan W.; Lunine, J. I.; Lorenz, R.; Hensley, S.; Janssen, M. A.; Callahan, P. S.; Gim, Y.; Johnson, W. T.; Paganelli, F.; Cassini RADAR Team

2006-09-01

381

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

382

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

383

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

384

Expectation-maximization approach to target model generation from multiple synthetic aperture  

E-print Network

Expectation-maximization approach to target model generation from multiple synthetic aperture radar-Optical Instrumentation Engineers. [DOI: 10.1117/1.1417493] Subject terms: synthetic aperture radar; model-based automatic with synthetic aperture radar SAR imaging systems. The broad utility of SAR as an imaging methodology is well

Willsky, Alan S.

385

Present day velocity field in Central Nevada Seismic Belt observed by Interferometric synthetic aperture radar  

NASA Astrophysics Data System (ADS)

We present the contemporary velocity field in the western Basin and Range province observed by satellite radar interferometry. A recent study in the Central Nevada Seismic Belt (CNSB) reported a broad area of uplift (~ 2-3 mm/yr) explained by postseismic mantle relaxation after a sequence of four earthquakes (M ~ 7) that occurred in the first half of the 20th century. To investigate the contemporary crustal deformation at the CNSB we use SAR imagery that covers a swath nearly 600 km long (six conventional SAR frames) acquired by the European Remote Sensing Satellites ERS-1 and ERS-2 between 1992 and 2009, and Envisat between 2004 and 2010. Time-Series results from Envisat suggest that the uplift velocity decreased for the last 7 years, which is consistent with models of postseismic relaxation. We also produce line of sight (LOS) velocity fields for different time periods (1992 - 2000, 1999 - 2009 and 1992 - 2009) by averaging independent interferograms with small perpendicular baselines (< 150 m). Additionally we identify high rates of deformation at Long Valley Caldera, land subsidence due to water pumping on mines and agricultural exploitation areas, and ground deformation associated with moderate earthquakes. We also present results of orbital error correction using continuous GPS data during the time-series inversion.

Greene, F.; Amelung, F.; Wdowinski, S.

2010-12-01

386

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

387

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

NASA Astrophysics Data System (ADS)

Stormwater runoff, Petroleum Hydrocarbon plumes are found abundantly near coastal cities, coastal population settlements especially in developing nations as more than half the world's human population. Ever increasing coastal populations and development in coastal areas have led to increased loading of toxic substances, nutrients and pathogens. These hazards cause deleterious effects on the population in many ways directly or indirectly which lead to algal blooms, hypoxia, beach closures, and damage to coastal fisheries. Hence these pollution hazards are important and the coastal administrations and people need to be aware of such a danger lurking very close to them. These hazards due to their small size, dynamic and episodic in nature are difficult to be visualized or to sample using in-situ traditional scientific methods. Natural obstructions like cloud cover and complex coastal circulations can hinder to detect and monitor such occurrences in the selected areas chosen for observations. This study takes recourse to Synthetic Aperture Radar (SAR) imagery because the pollution hazards are easily detectable as surfactants are deposited on the sea surface, along with nutrients and pathogens, smoothing capillary and small gravity waves to produce areas of reduced backscatter compared with surrounding ocean. These black spots can be termed as `Ecologic Indicator' and formed probably due to stronger thermal stratification, a deepening event of thermocline. SAR imagery that delivers useful data better than others regardless of darkness or cloud cover, should be made as an important observational tool for assessment and monitoring marine pollution hazards in the areas close to coastal regions. Till now the effects of climate change, sea level rise and global warming seems to have not affected the coastal populace of India in intrusions of sea water but it takes significance to the human health as the tides dominate these latitudes with bringing these polluted waters. KEY WORDS Coastal, ecologic, estuarine, hazard, indicator, marine, pollution, stressor, tides

Gambheer, Phani Raj

2012-07-01

388

Focusing ISAR images using fast adaptive time-frequency and 3D motion detection on simulated and experimental radar data ; Focusing inverse synthetic aperture radar images using fast adaptive time-frequency and three-dimensional motion detection on simulated and experimental radar data .  

E-print Network

??Optimization algorithms were developed for use with the Adaptive Joint Time-Frequency (AJFT) algorithm to reduce Inverse Synthetic Aperture Radar (ISAR) image blurring caused by higher-order… (more)

Brinkman, Wade H.

2005-01-01

389

Mapping and Monitoring Boreal Wetlands within the NEESPI Domain Using Spaceborne Synthetic Aperture Radar for Assessing Carbon Release  

NASA Astrophysics Data System (ADS)

Carbon and methane emissions from wetlands and lakes can have a large impact on global climate. These ecosystems are dominant features in the northern high latitudes hence the importance of assessing their spatial and temporal extent to improve upon global net carbon exchange estimates. Spaceborne synthetic aperture radar (SAR) is an effective tool for this purpose since large inaccessible areas can be monitored on a temporal basis regardless of atmospheric conditions or solar illumination and it is sensitive to vegetation and standing water. We employ multi-temporal PALSAR data (L-band, 30 m resolution, HH and HV-polarizations) and combined QuikSCAT and AMSR-E in this study to map wetland distribution and inundation state within sub-regions of the NEESPI domain. These products are then used within a carbon modeling framework. Multi-temporal PALSAR data spanning the beginning of the seasonal non-frozen period through the end of summer has been assembled over selected hydrologic basins within the NEESPI domain. A decision tree classification approach is then used to classify the radar data. Supplementary data layers are used within the classifier in order to support generation of the results. These data layers include Landsat imagery, a DEM, a proximity to water data layer, and image texture. The classification results depicting wetland extent are used to assess bi-weekly landscape inundation products derived from coarse resolution (~25 km) AMSR-E and QuikSCAT. These products will provide information on wetland extent and inundation dynamics on a bi-weekly basis. The coarse and high-resolution products are then used to calibrate and validate a carbon-modeling framework. Examples of how the remote sensing products are used to calibrate and validate the modeling framework will be presented as well. This work was carried out at the Jet Propulsion Laboratory, California Institute of Technology and at the University of Washington under contract with the National Aeronautics and Space Administration. This work has been undertaken in part within the framework of the JAXA ALOS Kyoto & Carbon Initiative. ALOS PALSAR data have been provided by JAXA EORC.

Podest, E.; McDonald, K. C.; Schroeder, R.; Bohn, T. J.; Lettenmaier, D. P.

2009-12-01

390

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

391

Aperture undersampling using compressive sensing for synthetic aperture stripmap imaging  

NASA Astrophysics Data System (ADS)

Synthetic aperture imaging is a high-resolution imaging technique employed in radar and sonar applications, which construct a large aperture by constantly transmitting pulses while moving along a scene of interest. In order to avoid azimuth image ambiguities, spatial sampling requirements have to be fulfilled along the aperture trajectory. The latter, however, limits the maximum speed and, therefore, the coverage rate of the imaging system. This paper addresses the emerging field of compressive sensing for stripmap synthetic aperture imaging using transceiver as well as single-transmitter and multi-receiver systems so as to overcome the spatial Nyquist criterion. As a consequence, future imaging systems will be able to significantly reduce their mission time due to an increase in coverage rate. We demonstrate the capability of our proposed compressive sensing approach to at least double the maximum sensor speed based on synthetic data and real data examples. Simultaneously, azimuth image ambiguities are successfully suppressed. The real acoustical measurements are obtained by a small-scale ultrasonic synthetic aperture laboratory system.

Leier, Stefan; Zoubir, Abdelhak M.

2014-12-01

392

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

393

Development of a GPS-aided motion measurement, pointing, and stabilization system for a Synthetic Aperture Radar. [Global Positioning System (GPS)  

SciTech Connect

An advanced Synthetic Aperture Radar Motion Compensation System has been developed by Sandia National Laboratories (SNL). The system includes a miniaturized high accuracy ring laser gyro inertial measurement unit, a three axis gimbal pointing and stabilization assembly, a differential Global Positioning System (GPS) navigation aiding system, and a pilot guidance system. The system provides several improvements over previous SNL motion compensation systems and is capable of antenna stabilization to less than 0.01 degrees RMS and absolute position measurement to less than 5.0 meters RMS. These accuracies have been demonstrated in recent flight testing aboard a DHC-6-300 Twin Otter'' aircraft.

Fellerhoff, J.R.; Kohler, S.M.

1991-01-01

394

Recent advances in airborne terrestrial remote sensing with the NASA airborne visible/infrared imaging spectrometer (AVIRIS), airborne synthetic aperture radar (SAR), and thermal infrared multispectral scanner (TIMS)  

NASA Technical Reports Server (NTRS)

Significant progress in terrestrial remote sensing from the air has been made with three NASA-developed sensors that collectively cover the solar-reflected, thermal infrared, and microwave regions of the electromagnetic spectrum. These sensors are the airborne visible/infrared imaging spectrometer (AVIRIS), the thermal infrared mapping spectrometer (TIMS) and the airborne synthetic aperture radar (SAR), respectively. AVIRIS and SAR underwent extensive in-flight engineering testing in 1987 and 1988 and are scheduled to become operational in 1989. TIMS has been in operation for several years. These sensors are described.

Vane, Gregg; Evans, Diane L.; Kahle, Anne B.

1989-01-01

395

Estimating lava volume by precision combination of multiple baseline spaceborne and airborne interferometric synthetic aperture radar: The 1997 eruption of Okmok Volcano, Alaska  

USGS Publications Warehouse

Interferometric synthetic aperture radar (InSAR) techniques are used to calculate the volume of extrusion at Okmok volcano, Alaska by constructing precise digital elevation models (DEMs) that represent volcano topography before and after the 1997 eruption. The posteruption DEM is generated using airborne topographic synthetic aperture radar (TOPSAR) data where a three-dimensional affine transformation is used to account for the misalignments between different DEM patches. The preeruption DEM is produced using repeat-pass European Remote Sensing satellite data; multiple interferograms are combined to reduce errors due to atmospheric variations, and deformation rates are estimated independently and removed from the interferograms used for DEM generation. The extrusive flow volume associated with the 1997 eruption of Okmok volcano is 0.154 ?? 0.025 km3. The thickest portion is approximately 50 m, although field measurements of the flow margin's height do not exceed 20 m. The in situ measurements at lava edges are not representative of the total thickness, and precise DEM data are absolutely essential to calculate eruption volume based on lava thickness estimations. This study is an example that demonstrates how InSAR will play a significant role in studying volcanoes in remote areas.

Lu, Z.; Fielding, E.; Patrick, M. R.; Trautwein, C. M.

2003-01-01

396

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

397

Synthetic aperture confocal imaging  

Microsoft Academic Search

Confocal microscopy is a family of imaging techniques that employ focused patterned illumination and synchronized imaging to create cross-sectional views of 3D biological specimens. In this paper, we adapt confocal imaging to large-scale scenes by replacing the optical apertures used in microscopy with arrays of real or virtual video projectors and cameras. Our prototype implementation uses a video projector, a

Marc Levoy; Billy Chen; Vaibhav Vaish; Mark Horowitz; Ian McDowall; Mark T. Bolas

2004-01-01

398

Use of Synthetic Aperture Radar (SAR) for geologic reconnaissance in Arctic regions: An example from the Arctic National Wildlife Refuge, Alaska  

SciTech Connect

Satellite-based synthetic aperture radar (SAR) can provide an additional remote-sensing tool for regional geologic studies in arctic regions. Although SAR data do not yield direct information on rock type and do not replace traditional optical data, SAR data can provide useful geologic information in arctic regions where the stratigraphic column includes a wide range of lithologies, and bedrock exposures have been reduced to rubble by frost action. For example, in ERS-1 SAR data from the Arctic National Wildlife Refuge (ANWR) of the northeastern Brooks Range, Alaska, carbonate and clastic rocks can give remarkably different radar responses on minimally reprocessed SAR data. The different radar response of different lithologies can specifically the size and angularity of scree in talus slopes. Additional postacquisition processing can both remove many of the negative terrain effects common in SAR data and enhance contrasts in bedrock lithology. Because of this ability to discriminate between gross lithologic packages, the ERS-1 SAR data can be used to provide a regional view of ANWR and a detailed look at specific areas. A mosaic of ERS-1 SAR data from all of ANWR provides a synoptic view of the regional structural framework, such as the anticlinoria of northern ANWR and the different allochthonous units of central and southern ANWR. Higher resolution ERS-1 SAR data of the Porcupine Lake area can be used to examine specific structural and stratigraphic problems associated with several major structural boundaries.

Hanks, C.L.; Guritz, R.M. [Univ. of Alaska, Fairbanks, AK (United States)

1997-01-01

399

Image domain feature extraction from synthetic aperture imagery  

Microsoft Academic Search

We consider the problem of estimating a parametric model that describes radar backscattering from synthetic aperture radar imagery. We adopt a scattering center model that incorporates both frequency and aspect dependence of scattering. We develop an approximate maximum likelihood algorithm for parameter estimation directly on regions of the SAR image. The algorithm autonomously selects model order and structure. Results are

Michael A. Koets; Randolph L. Moses

1999-01-01

400

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

401

Hunt for forgotten warplanes: a unique application for the Goddard Space Flight Center Search and Rescue Synthetic Aperture Radar (SAR2) program  

NASA Astrophysics Data System (ADS)

The principal purpose of the Beaconless Search and Rescue program at Goddard Space Flight Center (GSFC) is to utilize synthetic aperture radar (SAR) for the efficient and rapid location of recent small aircraft crashes. An additional side benefit might prove to be the detection and discovery of long lost or forgotten historic aircraft that have now become of immense value for museum display or among wealthy collectors. As the GSFC SAR2 program matures and its achievements in SAR target detection become more widely available, they will be of use to amateur and professional airplane hunters. We recommend that such ancillary benefits be kept in mind during the continued development and testing of such equipment, which would be of benefit to all future generations concerning the history of aviation. We welcome and encourage all participants to notify organizations such as ours of the discovery of any historic aircraft wreckage or intact abandoned old aircraft throughout the world.

Yagen, Gerald; Jackson, Christopher R.

1998-09-01

402

Multitemporal L- and C-Band Synthetic Aperture Radar To Highlight Differences in Water Status Among Boreal Forest and Wetland Systems in the Yukon Flats, Interior Alaska  

USGS Publications Warehouse

Tracking landscape-scale water status in high-latitude boreal systems is indispensible to understanding the fate of stored and sequestered carbon in a climate change scenario. Spaceborne synthetic aperture radar (SAR) imagery provides critical information for water and moisture status in Alaskan boreal environments at the landscape scale. When combined with results from optical sensor analyses, a complementary picture of vegetation, biomass, and water status emerges. Whereas L-band SAR showed better inherent capacity to map water status, C-band had much more temporal coverage in this study. Analysis through the use of L- and C-band SARs combined with Landsat Enhanced Thematic Mapper Plus (ETM+) enables landscape stratification by vegetation and by seasonal and interannual hydrology. Resultant classifications are highly relevant to biogeochemistry at the landscape scale. These results enhance our understanding of ecosystem processes relevant to carbon balance and may be scaled up to inform regional carbon flux estimates and better parameterize general circulation models (GCMs).

Balser, Andrew W.; Wylie, Bruce K.

2010-01-01

403

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  

Microsoft Academic Search

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 them and understanding their use of overwintering areas is of special interest. Synthetic aperture radar (SAR) imagery from two spaceborne satellites was examined as an

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

2010-01-01

404

Application of synthetic aperture radar (SAR) imagery to volcano mapping in the humid tropics: a case study in East Java, Indonesia  

NASA Astrophysics Data System (ADS)

Volcanoes in humid tropical environments are frequently cloud covered, typically densely vegetated and rapidly eroded. These factors complicate field and laboratory studies and even the basic identification of potentially active volcanoes. Numerous previous studies have highlighted the potential value of radar remote sensing for volcanology in equatorial regions. Here, cloud- and vegetation-penetrating LHH-band (? 24cm) synthetic aperture radar (SAR) data from the Japanese Earth Resources Satellite (JERS-1) are used to investigate persistently active volcanoes and prehistoric calderas in East Java, Indonesia. The LHH-band JERS-1 SAR produces high-spatial-resolution (18m) imagery with relatively high incidence angle that highlights structures and topographic variations at or greater than the wavelength scale while minimising geometrical distortions such as layover and foreshortening. These images, along with Internet browse data derived from the Canadian RADARSAT mission, provide new evidence relating regional tectonics to volcanism throughout East Java. Volcanic events, such as caldera collapse at the Tengger caldera, appear to have been partly controlled by northwest-aligned faults related to intra-arc sedimentary basins. Similar regional controls appear important at historically active Lamongan volcano, which is encircled by numerous flank maars and cinder cones. A previously undocumented pyroclastic sheet and debris avalanche deposit from the Jambangan caldera complex is also manifested in the synoptic radar images. At the currently active Semeru volcano these data permit identification of recent pyroclastic flow and lahar deposits. Radar data therefore offer a valuable tool for mapping and hazard assessment at late Quaternary volcanoes. The criteria developed in the analysis here could be applied to other regions in the humid tropics.

Carn, Simon A.

405

Height reconstruction techniques for synthetic aperture lidar systems  

NASA Technical Reports Server (NTRS)

The data-processing techniques and acquisition modes of a synthetic aperture lidar (SAL) instrument operating at optical wavelengths are closely related to the analogous modes of a synthetic aperture radar (SAR) instrument operating at microwave frequencies. It is consequently natural to explore the applicability of SAR processing techniques to SAL sensors. In this paper, we examine the feasibility of adopting SAR height-reconstruction techniques with SAL sensors to obtain high-resolution 3-D imagery at optical wavelengths.

Chen, Curtis W.; Hensley, Scott

2003-01-01

406

Synthetic Aperture Imaging of Surface Laid Targets by Sound  

NASA Astrophysics Data System (ADS)

This paper discusses the design and implementation of a synthetic aperture acoustic imaging system for investigating solid objects in an outdoor environment. Measurement results are reported for a setup consisting of a rail-mounted transceiver, digital data acquisition and control system, and local storage with data post processing capabilities. This imaging system works much like typical sonar and RF synthetic aperture radar technologies but operates above ground and uses acoustic waves in air for its interrogation.

Vignola, Joseph F.; Judge, John A.; Good, Chelsea E.; Bishop, Steven S.; Gugino, Peter M.; Soumekh, Mehrdad

2012-06-01

407

Practical applications of synthetic aperture imaging  

Microsoft Academic Search

Synthetic aperture imaging has been a focus of research for almost 3 decades. The research carried out at the Center for Fast Ultrasound Imaging has demonstrated that synthetic aperture focusing not only can be used in-vivo, but that it also yields superior B-mode and blood flow images. In the last years synthetic aperture focusing has moved from the lab to

Svetoslav Ivanov Nikolov; Jacob Kortbek; Jorgen Arendt Jensen

2010-01-01

408

Phase calibration for synthetic aperture imaging  

Microsoft Academic Search

High-resolution imaging can be achieved by optical aperture synthesis. Using a sparse array of smaller aperture, one can synthesize an aperture with the resolution of the equivalent filled aperture while reducing the size and weight of system. The environment and vibration factors of synthetic aperture arrays lead to errors in phase measurement and cause a severe degradation in the image

Changwei Wang; Yuesong Jiang; Yuntao He; Li Liu

2008-01-01

409

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

410

Synthetic aperture integration (SAI) algorithm for SAR imaging  

DOEpatents

A method and system for detecting the presence of subsurface objects within a medium is provided. In some embodiments, the imaging and detection system operates in a multistatic mode to collect radar return signals generated by an array of transceiver antenna pairs that is positioned across the surface and that travels down the surface. The imaging and detection system pre-processes the return signal to suppress certain undesirable effects. The imaging and detection system then generates synthetic aperture radar images from real aperture radar images generated from the pre-processed return signal. The imaging and detection system then post-processes the synthetic aperture radar images to improve detection of subsurface objects. The imaging and detection system identifies peaks in the energy levels of the post-processed image frame, which indicates the presence of a subsurface object.

Chambers, David H; Mast, Jeffrey E; Paglieroni, David W; Beer, N. Reginald

2013-07-09

411

High Altitude Synthetic Aperture Imaging of Titan  

NASA Astrophysics Data System (ADS)

The Cassini spacecraft has been conducting observations of Titan since July 2004 . Currently, 6 close flyby's have collected synthetic aperture radar (SAR) data giving image resolutions down to 300 - 500 m. About 14 additional close radar imaging passes are planned. To improve radar coverage and increase the synergy with other Cassini imaging instruments such as VIMS and ISS, the radar team has started experimenting with very high altitude SAR imaging where conditions permit. This presentation will examine the performance trade-offs, special processing issues, and science potential of these high altitude SAR observations. These data collections are distinct from the normal Titan SAR images because the range will be much larger (around 20,000 km). To acquire enough signal in these circumstances, the radar operates in the lowest bandwidth scatterometer mode while spacecraft pointing control is used to slowly pan the central beam across a small swath. Due to a lower signal to noise ratio these high altitude images are designed to average together 150-200 independent looks to see features that may lie below the noise floor. So far, three high altitude images have been acquired during Titan flyby's T12, T13, and T15. In T12 imaging was attempted from 37000 km with an effective resolution around 5 km. In T13 the Huygens Probe landing site was imaged from 11000 km with effective resolution of 1 - 2 km. In T15 the Tsegehi area was imaged from 20000 km with effective resolution of 2 - 3 km.

West, Richard; Stiles, B.; Anderson, Y.; Boehmer, R.; Callahan, P.; Gim, Y.; Hamilton, G.; Johnson, W. T.; Kelleher, K.; Wye, L.; Zebker, H.

2006-09-01

412

Three-Dimensional Multiple Layer Extended Target Modeling for Inverse Synthetic Aperture Radar Studies in Target Identification  

Microsoft Academic Search

For the target-sensor simulation involving a ship and a High Range Resolution (HRR) radar system the target model has to have physical extent greater than the radar's resolution abilities. In this paper an extended single layer and its enhanced multiple layer multiple scatterer mathematical model counterpart are presented. Simulations illustrate the compliance of the target model to the theoretical foundations

Theodoros G. Kostis; Sokratis K. Katsikas

413

Observation of a nonlinear wave disturbance in the marine atmosphere by the synthetic aperture radar aboard the ERS 1 satellite  

Microsoft Academic Search

A nonlinear wave disturbance in the marine atmosphere associated with an atmospheric cold front has been identified on a spaceborne radar image of the North Sea by its imprint on the sea surface. This nonlinear wave disturbance is either a solitary wave disturbance or an undular bore propagating in the lower marine atmosphere. The radar image showing sea surface manifestations

Werner Alpers; Gerd Stilke

1996-01-01

414

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

SciTech Connect

Ground surface subsidence resulting from the March 1992 JUNCTION underground nuclear test at the Nevada Test Site (NTS) imaged by satellite synthetic aperture radar interferometry (InSAR) wholly occurred during a period of several months after the shot (Vincent et al., 1999) and after the main cavity collapse event. A significant portion of the subsidence associated with the small (less than 20 kt) GALENA and DIVIDER tests probably also occurred after the shots, although the deformation detected in these cases contains additional contributions from coseismic processes, since the radar scenes used to construct the deformation interferogram bracketed these two later events, The dimensions of the seas of subsidence resulting from all three events are too large to be solely accounted for by processes confined to the damage zone in the vicinity of the shot point or the collapse chimney. Rather, the subsidence closely corresponds to the span dimensions predicted by Patton's (1990) empirical relationship between spall radius and yield. This suggests that gravitational settlement of damaged rock within the spall zone is an important source of post-shot subsidence, in addition to settlement of the rubble within the collapse chimney. These observations illustrate the potential power of InSAR as a tool for Comprehensive Nuclear-Test-Ban Treaty (CTBT) monitoring and on-site inspection in that the relatively broad ({approx} 100 m to 1 km) subsidence signatures resulting from small shots detonated at normal depths of burial (or even significantly overburied) are readily detectable within large geographical areas (100 km x 100 km) under favorable observing conditions. Furthermore, the present results demonstrate the flexibility of the technique in that the two routinely gathered satellite radar images used to construct the interferogram need not necessarily capture the event itself, but can cover a time period up to several months following the shot.

Foxwall, W.

2000-07-24

415

Simulation of synthetic aperture imaging ladar (SAIL) for three-dimensional target model  

Microsoft Academic Search

In conventional imaging laser radar, the resolution of target is constrained by the diffraction-limited, which includes the beamwidth of the laser in the target plane and the telescope's aperture. Synthetic aperture imaging Ladar (SAIL) is an imaging technique which employs aperture synthesis with coherent laser radar, the resolution is determined by the total frequency spread of the source and is

Ning Yi; Zhen-Sen Wu

2010-01-01

416

Time-dependent volcano source monitoring using interferometric synthetic aperture radar time series: A combined genetic algorithm and Kalman filter approach  

NASA Astrophysics Data System (ADS)

Modern geodetic methods allow continuous monitoring of deformation fields of volcanoes. The acquired data contribute significantly to the study of the dynamics of magmatic sources prior to, during and after eruptions and intrusions. In addition to advancing the monitoring techniques, it is important to develop suitable approaches to deal with deformation time series. Here, we present, test and apply a new approach for time-dependent, nonlinear inversion using a combination of a genetic algorithm (GA) and a Kalman filter (KF). The GA is used in the form presented by Shirzaei and Walter (2009), and the KF implementation now allows for the treatment of monitoring data as a full time series rather than as single time steps. This approach provides a flexible tool for assessing unevenly sampled and heterogeneous time series data and explains the deformation field using time-consistent dislocation sources. Following synthetic tests, we demonstrate the merits of time-consistent source modeling for interferometric synthetic aperture radar (InSAR) data available between 1992 and 2008 from the Campi Flegrei volcano in Italy. We obtained multiple episodes of linear velocity for the reservoir pressure change associated with a parabolic surface deformation on the volcano. These data may be interpreted via differential equations as a linear flux to the shallow reservoir that provides new insight into how both the shallow and deep reservoirs communicate beneath Campi Flegrei. The synthetic test and case study demonstrate the robustness of our approach and the ability to track and monitor the source of systems with complex dynamics. It is applicable to time-dependent optimization problems in volcanic and tectonic environments in other tectonic environments in other areas and allows understanding of the spatiotemporal extent of a physical process in quantitative manner.

Shirzaei, M.; Walter, T. R.

2010-10-01

417

Synthetic aperture interferometry: error analysis.  

PubMed

Synthetic aperture interferometry (SAI) is a novel way of testing aspherics and has a potential for in-process measurement of aspherics [Appl. Opt. 42, 701 (2003)]. A method to measure steep aspherics using the SAI technique has been previously reported [Appl. Opt. 47, 1705 (2008)]. Here we investigate the computation of surface form using the SAI technique in different configurations and discuss the computational errors. A two-pass measurement strategy is proposed to reduce the computational errors, and a detailed investigation is carried out to determine the effect of alignment errors on the measurement process. PMID:20648161

Biswas, Amiya; Coupland, Jeremy

2010-07-10

418

Application of compressed sensing in sparse aperture imaging of radar  

Microsoft Academic Search

A new optimal reconstruction method based on compressed sensing (CS) for sparse synthetic aperture radar (SAR)\\/ inverse SAR (ISAR), which can be used in widely sparse aperture, is proposed in this letter. Unlike other parametric estimation method as all-pole algorithm, CS can obtain near-optimal estimation and global-minimal error of gapped signal representation with structured dictionaries and random projections. To resolve

Li Jun; Xing Mengdao; Wu Shunjun

2009-01-01

419

Computer Simulation of Synthetic Aperture Radar Data Adam E. Robertson, David V.Arnold, David G . Long  

E-print Network

for simulating a distributed scene which is capable of modeling SAR data under mod- erate motion of the radar in Utah and at significant archaeological sites in Israel. YINSAR, a 9.9 GHz interferometric SAR, will be used for numerous ap- plications requiring high resolution digital elevation maps. Both systems

Long, David G.

420

394 IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING, VOL. 53, NO. 1, JANUARY 2015 OFDM Synthetic Aperture Radar Imaging  

E-print Network

radar (SAR) systems may correspond to the frequency-hopping and direct-sequence spread spectrum systems communications generations, in this paper, we propose the or- thogonal frequency-division multiplexing (OFDM) SAR (IRCI)-free (high range resolution) SAR image in a SAR system. The sufficient CP in- sertion along

Xia, Xiang-Gen

421

Tip Clearance Measurement Technique for Stationary Gas Turbines Using an Autofocusing Millimeter-Wave Synthetic Aperture Radar  

Microsoft Academic Search

In this paper, an autofocusing radar technique is presented for tip clearance measurements in combustion turbines capable of resolving the edges of a typical blade tip. The clearance is determined by measuring the reflection at the blade tip while passing by the antenna, subsequently focusing the data by means of a matched filter operation and interpreting the phase of the

Andreas Schicht; Stefan Schwarzer; Lorenz-Peter Schmidt

2012-01-01

422

Synthetic aperture sonar image statistics  

NASA Astrophysics Data System (ADS)

Synthetic Aperture Sonar (SAS) systems are capable of producing photograph quality seafloor imagery using a lower frequency than other systems of comparable resolution. However, as with other high-resolution sonar systems, SAS imagery is often characterized by heavy-tailed amplitude distributions which may adversely affect target detection systems. The constant cross-range resolution with respect to range that results from the synthetic aperture formation process provides a unique opportunity to improve our understanding of system and environment interactions, which is essential for accurate performance prediction. This research focused on the impact of multipath contamination and the impact of resolution on image statistics, accomplished through analyses of data collected during at-sea experiments, analytical modeling, and development of numerical simulations. Multipath contamination was shown to have an appreciable impact on image statistics at ranges greater than the water depth and when the levels of the contributing multipath are within 10 dB of the direct path, reducing the image amplitude distribution tails while also degrading image clarity. Image statistics were shown to depend strongly upon both system resolution and orientation to seafloor features such as sand ripples. This work contributes to improving detection systems by aiding understanding of the influences of background (i.e. non-target) image statistics.

Johnson, Shawn F.

423

Flood disaster monitoring in Thailand by using a airborne L-band SAR: Polarimetric and interferometry Synthetic Aperture Radar with L-band(Pi-SAR-L)  

NASA Astrophysics Data System (ADS)

It was heavy rainfall around the northern region of Thailand from July to September 2011, which caused flood disaster to quite wide region of Thailand, it finally reached to the Bangkok central in the end of October 2011. Japan Aerospace Exploration Agency (JAXA) conducted an emergency observation by using a airborne L-band SAR: Polarimetric and interferometry Synthetic Aperture Radar with L-band(Pi-SAR-L) from 5th to 27th November to monitor flood area. Pi-SAR-L has a center frequency of 1271.5 MHz, a band width of 50 MHz, a slant range resolution of 3 m, and an acquisition swath of 15 km on the ground. Pi-SAR-L is boarded on an aircraft of the Gulfstream-II operated by the Diamond Air Service(DAS), Japan, and the Gulfstream-II was ferried to the Chieng-Mai airport in the North Thailand, from Japan. In our presentation, we will show flood area around Bangkok and its variations detected by Pi-SAR-L

Kawano, N.; Sobue, S.; Shimada, M.; Ohyoshi, K.

2012-04-01

424

A study of P-band synthetic aperture radar applicability and performance for Mars exploration: Imaging subsurface geology and detecting shallow moisture  

NASA Astrophysics Data System (ADS)

Over the past decade, orbital images of the Martian surface revealed key evidence about the history of the planet environment (craters, faults, paleo-lakes, and rivers), partially hidden under a widespread layer of aeolian deposits. Furthermore, several recent observations and studies support the hypothesis that water could be found in the shallow subsurface of Mars. Low-frequency synthetic aperture radar (SAR) has demonstrated its subsurface imaging capabilities on Earth, especially in arid regions. While SAR potentials for Mars exploration have already been widely discussed, we present here results of a theoretical and parametric study, based on the experience we gained from terrestrial surveys on Mars analog test sites, which evaluates the capabilities of a P-band (430 MHz) SAR for Mars exploration for both shallow subsurface geology mapping and moisture detection. We suggest that a P-band polarimetric SAR can probe the first meters of the Martian subsurface to reveal the dust-covered geology and to monitor moisture changes over large scales.

Paillou, Philippe; Lasne, Yannick; Heggy, Essam; Malézieux, Jean-Marie; Ruffié, Gilles

2006-04-01

425

Observation of ocean tides below the Filchner and Ronne Ice Shelves, Antarctica, using synthetic aperture radar interferometry: Comparison with tide model predictions  

NASA Astrophysics Data System (ADS)

Tides near and under floating glacial ice, such as ice shelves and glacier termini in fjords, can influence heat transport into the subice cavity, mixing of the under-ice water column, and the calving and subsequent drift of icebergs. Free-surface displacement patterns associated with ocean variability below glacial ice can be observed by differencing two synthetic aperture radar (SAR) interferograms, each of which represents the combination of the displacement patterns associated with the time-varying vertical motion and the time-independent lateral ice flow. We present the pattern of net free-surface displacement for the iceberg calving regions of the Ronne and Filchner Ice Shelves in the southern Weddell Sea. By comparing SAR-based displacement fields with ocean tidal models, the free-surface displacement variability for these regions is found to be dominated by ocean tides. The inverse barometer effect, i.e., the ocean's isostatic response to changing atmospheric pressure, also contributes to the observed vertical displacement. The principal value of using SAR interferometry in this manner lies in the very high lateral resolution (tens of meters) obtained over the large region covered by each SAR image. Small features that are not well resolved by the typical grid spacing of ocean tidal models may contribute to such processes as iceberg calving and cross-frontal ventilation of the ocean cavity under the ice shelf.

Rignot, E.; Padman, L.; MacAyeal, D. R.; Schmeltz, M.

426

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

427

Multi-input multi-output frequency-modulated continuous wave synthetic aperture radar system using beat-frequency division waveforms  

NASA Astrophysics Data System (ADS)

Attention has been paid to lightweight, cost-effective frequency-modulated continuous wave (FMCW) synthetic aperture radar (SAR) in recent years. Though FMCW SAR can operate at high altitude, it is still impracticable for wide swath or high Doppler bandwidth remote sensing because of the dramatic losses of range resolution and processing gain. Moreover, the system sampling rate is too high for real-time processing. All these restrictions caused by the bandwidth loss of the dechirp operation can be relieved by expanding the system sweep cycle. However, the broadening of the sweep cycle decreases the system pulse repetition frequency with azimuth ambiguity, which can be suppressed by exploiting the spatial diversity of multi-input multi-output (MIMO) systems. This paper reports a MIMO-FMCW SAR system using beat-frequency division waveforms. There is a small frequency interval and a large overlap (in frequency) between the orthogonal waveforms. As the frequency interval is much smaller than the signal bandwidth, the echoes that come from different transmitters can be separated by bandpass filtering with little intrapulse interference. Consequently, the applications of FMCW SAR systems can be extended for wider swath or higher Doppler bandwidth remote sensing. Theoretical analysis and simulation results illustrate the feasibility of this system.

Wang, Jie; Chen, Long-yong; Liang, Xing-dong; Ding, Chi-biao; Hong, Wen; Zhou, Liang-jiang; Dong, Yong-wei; Li, Kun

2013-07-01

428

Sequence of rifting in Afar, Manda-Hararo rift, Ethiopia, 2005–2009: Time-space evolution and interactions between dikes from interferometric synthetic aperture radar and static stress change modeling  

Microsoft Academic Search

Thirteen dike intrusions in the Manda Hararo rift, Afar (Ethiopia), from September 2005 to June 2009, studied using an extensive interferometric synthetic aperture radar (InSAR) data set, provide insight into the mechanics of a major active rift. Kinematic inversions of InSAR data reveal that dikes opened by 0.8–3.5 m at an average 5 km depth, with volumes of 0.04–0.2 km3

R. Grandin; A. Socquet; E. Jacques; N. Mazzoni; J.-B. de Chabalier; G. C. P. King

2010-01-01

429

Transient rift opening in response to multiple dike injections in the Manda Hararo rift (Afar, Ethiopia) imaged by time-dependent elastic inversion of interferometric synthetic aperture radar data  

Microsoft Academic Search

Interferometric synthetic aperture radar (InSAR) data spanning the time intervals separating thirteen dike intrusions in the Manda Hararo–Dabbahu rift (Afar, Ethiopia) from 2005 to 2009 show that transient deformation occurs in the inter-diking period. This deformation can be explained by the presence of seven inflating or deflating pressure sources. By combining the data acquired on four different InSAR tracks, through

R. Grandin; A. Socquet; M.-P. Doin; E. Jacques; J.-B. de Chabalier; G. C. P. Kingl

2010-01-01

430

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

431

Time Series of Snow Water Equivalent (SWE) Evolution Derived Using Interferometric Synthetic Aperture Radar (InSAR)  

NASA Astrophysics Data System (ADS)

Radar remote sensing and interferomtery have a unique ability to differentiate various snowpack conditions (i.e. wetness, surface roughness, ice layers, and grain size). Previous research has shown a relationship between interferometric phase of a radar signal and changes in snow water equivalent (SWE) for dry snow. Overlapping ascending and descending orbits from the ERS-1 (European Remote-Sensing Satellite) 3-day repeat phase are used to construct a near-daily time series of an Arctic Alaskan snowpack (Kuparuk Watershed, Brooks Range, Alaska) in March of 1994. Despite having no direct SWE measurements within the study area, data from meterological stations (e.g. temperature, wind speed/direction, and precipitation) are used to interpret the spatial variation within each change in SWE map over the 3-day periods. A significant precipitation event is recorded within the time series and compared to a time period depicting little to no snow as precipitation. Promising results within this study area have deemed the need for additional research sites in the Western United States where this 3-day repeat phase of the ERS-1 satellite brackets a precipitation event and meterological stations exist directly measuring SWE.

Deeb, E. J.; Forster, R. R.

2006-12-01

432

Synthetic Aperture Radar Remote Sensing of Bottom-Fast ice in the Mackenzie Delta Region, Northwest Territories, Canada  

Microsoft Academic Search

Bottom-fast ice (BFI) refers to sea- or lake-ice that freezes to the sea- or lake-bed during the course of the winter season. The timing and distribution of BFI controls the mean annual temperature of the upper sediment column and therefore the potential for development and maintenance of permafrost and the thickness of the sub-bottom active layer. Air- and satellite-borne Synthetic

S. M. Solomon; G. Manson; D. Monita; T. Hirose; D. Power

2004-01-01

433

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

434

Southern San Andreas-San Jacinto fault system slip rates estimated from earthquake cycle models constrained by GPS and interferometric synthetic aperture radar observations  

NASA Astrophysics Data System (ADS)

We use ground geodetic and interferometric synthetic aperture radar satellite observations across the southern San Andreas (SAF)-San Jacinto (SJF) fault systems to constrain their slip rates and the viscosity structure of the lower crust and upper mantle on the basis of periodic earthquake cycle, Maxwell viscoelastic, finite element models. Key questions for this system are the SAF and SJF slip rates, the slip partitioning between the two main branches of the SJF, and the dip of the SAF. The best-fitting models generally have a high-viscosity lower crust (? = 1021 Pa s) overlying a lower-viscosity upper mantle (? = 1019 Pa s). We find considerable trade-offs between the relative time into the current earthquake cycle of the San Jacinto fault and the upper mantle viscosity. With reasonable assumptions for the relative time in the earthquake cycle, the partition of slip is fairly robust at around 24-26 mm/a for the San Jacinto fault system and 16-18 mm/a for the San Andreas fault. Models for two subprofiles across the SAF-SJF systems suggest that slip may transfer from the western (Coyote Creek) branch to the eastern (Clark-Superstition hills) branch of the SJF from NW to SE. Across the entire system our best-fitting model gives slip rates of 2 ± 3, 12 ± 9, 12 ± 9, and 17 ± 3 mm/a for the Elsinore, Coyote Creek, Clark, and San Andreas faults, respectively, where the large uncertainties in the slip rates for the SJF branches reflect the large uncertainty in the slip rate partitioning within the SJF system.

Lundgren, Paul; Hetland, Eric A.; Liu, Zhen; Fielding, Eric J.

2009-02-01

435

Theory for synthetic aperture radar imaging of the ocean surface - With application to the Tower Ocean Wave and Radar Dependence experiment on focus, resolution, and wave height spectra  

NASA Astrophysics Data System (ADS)

A one-dimensional model for simulating azimuthal SAR imaging of the ocean surface is developed which can admit both the 'distributed surface' and 'velocity bunching' approaches. Computer simulations demonstrate that the time-dependent modulation patterns due to the radar cross section variation and the velocity bunching effects provide optimum focusing around half the phase velocity of the long wave. The results indicate that in the Tower Ocean Wave and Radar Dependence experiment, SAR imaging at L band is approximately linear.

Kasilingam, Dayalan P.; Shemdin, Omar H.

1988-11-01

436

Study of synthetic aperture radar data compression and encoding. Part 3: Performance evaluation of speckle suppression and data compression algorithms  

NASA Astrophysics Data System (ADS)

Rate distortion bounds for SAR images are compared with rate versus distortion relations obtained with speckle suppression and data compression algorithms. A method for optimally processing multispectral SAR-images is given. It uses the spectral correlation between the mean return power corresponding to each spectral channel. Real SAR-data is processed with the algorithms and subjected to information extraction experiments. Synthetic SAR-images can not efficiently be processed by the speckle suppression algorithm for one and four looks, if the goal is to obtain a least squares estimate of the reference image. For Seasat imagery (4 looks) data reduction with a compression ratio of 8, without speckle suppression, gives very acceptable results, with almost no impact on image segmentation for land scenes and on Fourier analysis for ocean scenes. The extraction of dominant ocean wave length and direction is not influenced by data compression and speckle suppression applied to Seasat data, even when the compression ratio is 20, and the appearance of Seasat imagery improves if speckle suppression is applied.

Huisman, W. C.; Verhoef, W.; Okkes, R. W.

1986-03-01

437

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

438

Wideband planar phased array antenna at Ku frequency-band for synthetic aperture radars and radar-guided missiles tracking and detection  

Microsoft Academic Search

This paper introduces the complete design, simulation and implementation of 1×2, 1×4, 1×8 sub-arrays antennas and 8×8 planar phased array antenna including power combiners and matching networks. U-slotted rectangular microstrip patch antenna element with aperture coupled feeding technique and impedance bandwidth of more than 20% at center frequency of 17.75 GHz is used as an array element. Method of moment

W. Swelam; A. A. Mitkees; M. M. Ibrahim

2006-01-01

439

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

440

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