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This special issue includes papers selected from EUSAR 2004. The publisher suggested including the top 10% of the EUSAR 2004 programme. As we had 280 presented papers including posters we came up with a selection of 26 papers. Bec...
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This special issue includes papers selected from EUSAR 2004. The publisher suggested including the top 10% of the EUSAR 2004 programme. As we had 280 presented papers including posters we came up with a selection of 26 papers. Because of the large number of pages this special issue has therefore been published in two parts. With EUSAR a unique, worldwide forum for everyone working in the SAR field - scientists, system designers, teachers and users - was established. Each EUSAR conference represents the most recent state-of-the-art in SAR in the world and exhibits perspectives for future activities. The selection of papers included in this double issue reflects these intentions.
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We propose a novel method to select long-term coherent targets from a set of repeated-pass interferometric acquisitions. The major assumption is that targets are so close together to share the same optical path. This leads to an e...
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We propose a novel method to select long-term coherent targets from a set of repeated-pass interferometric acquisitions. The major assumption is that targets are so close together to share the same optical path. This leads to an efficient singular-value-decomposition-based estimator of the targets' phase and, then, to PS detection. The estimated phase can be used to define the PS coherence for each image. Being sensitive to acquisition and processing artifacts, the PS coherence is a valuable tool for quality assessment of the interferometric stack. Results are shown with real data sets in both single and full polarizations.
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A Bayesian approach is presented for model-based classification of images with application to synthetic-aperture radar. Posterior probabilities are computed for candidate hypotheses using physical features estimated from sensor da...
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A Bayesian approach is presented for model-based classification of images with application to synthetic-aperture radar. Posterior probabilities are computed for candidate hypotheses using physical features estimated from sensor data along with features predicted from these hypotheses. The likelihood scoring allows propagation of uncertainty arising in both the sensor data and object models. The Bayesian classification, including the determination of a correspondence between unordered random features, is shown to be tractable, yielding a classification algorithm, a method for estimating error rates, and a tool for evaluating the performance sensitivity. The radar image features used for classification are point locations with an associated vector of physical attributes; the attributed features are adopted from a parametric model of high-frequency radar scattering. With the emergence of wideband sensor technology, these physical features expand interpretation of radar imagery to access the frequency- and aspect-dependent scattering information carried in the image phase.
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Precise eruption rates of active pahoehoe Lava flows on Kilauea volcano, Hawaii, have been determined using spaceborne radar data acquired by the Space Shuttle Imaging Radar-C (SLR-C). A coastal site downslope from the Pu'u O'o ve...
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Precise eruption rates of active pahoehoe Lava flows on Kilauea volcano, Hawaii, have been determined using spaceborne radar data acquired by the Space Shuttle Imaging Radar-C (SLR-C). A coastal site downslope from the Pu'u O'o vent was imaged once per day, on each of the four days of October 7-10, 1994. Day-to-day decorrelation due to resurfacing was determined by interferometric combination of the data at 15 m resolution over a wide area. On successive days, new lava resurfaced 335 700 m(2), 368 775 m(2), and 356 625 m(2). Assuming an average pahoehoe flow thickness of 50 cm, a mean effusion rate for this period is approximately 2 m(3)/s. The radar observations show persistent surface activity at each site, rather than downslope migration of coherent lava flows. [References: 11]
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ArcSAR is a ground-based synthetic aperture radar (GBSAR) that has recently been receiving increasing interest in the scientific literature. While the conventional GBSAR exploits the movement of an antenna along a linear rail to s...
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ArcSAR is a ground-based synthetic aperture radar (GBSAR) that has recently been receiving increasing interest in the scientific literature. While the conventional GBSAR exploits the movement of an antenna along a linear rail to synthesize a large aperture, an ArcSAR exploits the spatial diversity of the data acquired by an antenna fixed to a rotating arm. The great advantage of ArcSAR is its capability to synthesize images at 360° with a constant resolution in azimuth. In this paper, the authors propose and test a new focusing algorithm that does not require to operate in the far field and neither with narrow beam antennas; moreover, it is flexible enough to focus on any plane (not necessarily on the rotation plane) as well as in the whole 3-D space. Furthermore, the authors demonstrate theoretically and experimentally that ArcSAR images can be affected by a “defocusing effect” of the targets far from the rotation plane, which has to be taken into consideration when designing such radars.
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In the above article
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Due to the larger orbital arc and longer synthetic aperture time in medium Earth orbit (MEO) synthetic aperture radar (SAR), it is difficult for conventional SAR imaging algorithms to achieve a good imaging result. An improved hig...
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Due to the larger orbital arc and longer synthetic aperture time in medium Earth orbit (MEO) synthetic aperture radar (SAR), it is difficult for conventional SAR imaging algorithms to achieve a good imaging result. An improved higher order nonlinear chirp scaling (NLCS) algorithm is presented for MEO SAR imaging. First, the point target spectrum of the modified equivalent squint range model-based signal is derived, where a concise expression is obtained by the method of series reversion. Second, the well-known NLCS algorithm is modified according to the new spectrum and an improved algorithm is developed. The range dependence of the twodimensional point target reference spectrum is removed by improved CS processing, and accurate focusing is realized through range-matched filter and range-dependent azimuth-matched filter. Simulations are performed to validate the presented algorithm. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
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This paper describes a small unmanned aerial vehicle (UAV)-based synthetic aperture radar (SAR) system using low-cost radar (5-6 GHz), position (GNSS/RTK) and attitude (IMU) sensors for the generation of high-resolution images. Me...
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This paper describes a small unmanned aerial vehicle (UAV)-based synthetic aperture radar (SAR) system using low-cost radar (5-6 GHz), position (GNSS/RTK) and attitude (IMU) sensors for the generation of high-resolution images. Measurements using straight as well as highly curved flight trajectories and varying flight speeds are presented, showing range and cross-range lobe-widths close to the theoretical limits. An analysis of the improvements obtained by the use of attitude angles (roll, pitch, and yaw), to correct for the relative offsets in antenna positions as the UAV moves, is included. A capability to generate SAR images onboard with the back-projection algorithm has been implemented using a GPU accelerated single-board computer. Generated images are transmitted to ground using a Wi-Fi data link.
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High-resolution radar imaging requires wide bandwidths and highly dense samplings of both time/frequency and spatial domains. However, the rapidly developing field of compressive sensing (CS) breaks this rule and paves a way for s...
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High-resolution radar imaging requires wide bandwidths and highly dense samplings of both time/frequency and spatial domains. However, the rapidly developing field of compressive sensing (CS) breaks this rule and paves a way for simultaneously achieving high-resolution imaging with a significantly reduced number of samples. Although CS is seemed to be an intuitively attractive approach, the ongoing studies have shown the application of CS to synthetic aperture radar (SAR) data to be a challenging task in practice. In this work, as a contribution to these efforts, we address the potential use of CS in millimeter-wave inverse SAR (ISAR) imaging. Various simulation and experimental imaging results are presented to demonstrate the validity and the robustness of the proposed CS-based reconstruction from very limited samples.
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Satellite-based radar interferometry is a technique capable of measuring small surface elevation changes at large scales and with a high resolution. In vadose zone hydrology, it has been recognized for a long time that surface ele...
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Satellite-based radar interferometry is a technique capable of measuring small surface elevation changes at large scales and with a high resolution. In vadose zone hydrology, it has been recognized for a long time that surface elevation changes due toswell and shrinkage of clayey soils can serve as an estimate for soil water storage change. Therefore, satellite-based radar interferometry can potentially offer an alternative methodology to estimate soil water storage change at field or regional scales. This paper introduces principles of satellite-based radar interferometry and identifies limitations and potential applications of the technique to measure surface elevation changes from clay shrinkage. In situ measurements were performed and a linearrelation between soil water storage depletion and layer shrinkage was obtained. Data from the TerraSAR-X satellite over the measurement area were analyzed to identify the most favorable conditions for radar interferometry to measure vertical shrinkage. High-quality phase observations over clayey areas in polders with limited vegetation can be explained from differences in land use and soil type. Signal noise over sparsely vegetated agricultural fields was successfully reduced by multilooking over agricultural fields at the cost of spatial resolution. Good resemblance between in situ measured shrinkage and differential phase change was found in a test period. Based on this study, we expect that radar interferometric processing of data from the future satellite mission Sentinel-1 can play a crucial role in providing much-needed observations of vadose zone processes at the field scale and beyond.
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