共查询到20条相似文献,搜索用时 0 毫秒
1.
An ERS-1 synthetic aperture radar image of a tropical squall linecompared with weather radar data 总被引:1,自引:0,他引:1
Lin I.-I. Alpers W. Khoo V. Lim H. Lim T.K. Kasilingam D. 《Geoscience and Remote Sensing, IEEE Transactions on》2001,39(5):937-945
A radar image acquired by the C-band synthetic aperture radar (SAR) aboard the European Remote Sensing satellite ERS-2 over the coastal waters south of Singapore showing radar signatures of a strong tropical squall line (“Sumatra Squall”) is compared with coincident and collocated weather radar data. Squall line features such as the gust front, areas of updraft convergence, and rain areas are identified. Possible attenuation effects from the rain drops in the atmosphere under very heavy rain (rain rate >100 mm/h) is suggested. In addition, the possibility of extracting the associated geophysical parameters, i.e., rain rate and wind speed from SAR imagery is investigated. The rain rate is estimated from the attenuation signature in the SAR image. Comparison between the estimated rain rate and weather radar rain rate shows consistency. Wind speed associated with the squall line is estimated based on the CMOD4 wind scatterometer model. The estimated wind speed pattern appears to be in agreement with the observed squall line structure. Possible errors in the wind estimation due to effects of rain are suggested 相似文献
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A LUMINANCE EDGE EXTRACTION METHOD USING GRADIENT OF GRAY LEVEL FOR SYNTHETIC APERTURE RADAR IMAGERY
In the multistage imaging processing for SAR digital imaging and applications ofSAR imagery,extraction of luminance edge for the SAR imageis often required.It is well studiedto extract the luminance edge for ordinary images,The methods using gradient are effective andcommonly used.Because of the serious noise of coherent speckle exists in SAR images,somepeople believe that edge extraction by using gradient for SAR imagery gives poor results.Inthis paper,we have derived a rather ideal method for the extraction of luminance edge for SARimagery with the consideration of the characteristics of SAR imagery.This method uses therelative average gradient and combines detection with tracking. 相似文献
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Japanese Earth Resources Satellite-1 synthetic aperture radar 总被引:2,自引:0,他引:2
Nemoto Y. Nishino H. Ono M. Mizutamari H. Nishikawa K. Tanaka K. 《Proceedings of the IEEE. Institute of Electrical and Electronics Engineers》1991,79(6):800-809
The spaceborne synthetic aperture radar (SAR) to be launched on the Japanese Earth Resources Satellite-1 is described. The SAR is operated in the L -band. 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°. 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 相似文献
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The effects of Gaussian random and linear phase change on the response of the matched azimuth processor of a synthetic aperture imaging radar is analyzed numerically. 相似文献
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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 well as the degradation in azimuthal resolution as a function of ocean wave amplitude, wave frequency, direction of wave propagation, and radar wavelength, incidence angle, and integration time. 相似文献
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Focusing bistatic synthetic aperture radar using dip move out 总被引:18,自引:0,他引:18
D'Aria D. Guarnieri A.M. Rocca F. 《Geoscience and Remote Sensing, IEEE Transactions on》2004,42(7):1362-1376
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 Born approximation (no multiple reflections), seismic bistatic acquisitions are transformed into monostatic ones using a simple operator named "dip move out" (DMO). In essence, the elliptical locus of the reflectors corresponding to a spike in the bistatic survey is forward modeled as if observed in a monostatic one. The outcome of the model, the so-called smile, is a short operator, slowly time varying but space stationary. To transform a bistatic survey into a monostatic one, it is enough to convolve the initial dataset with this smile. Based on the well-known similarity between seismic and SAR surveys, DMO is first described in its simple geometric understanding and is then used in the SAR case. The same processing that is being used for movement compensation can be applied to the bistatic to monostatic survey transformation. Synthetic examples are also provided. 相似文献
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Ozdemir C. Bhalla R. Trintinalia L.C. Hao Ling 《Antennas and Propagation, IEEE Transactions on》1998,46(12):1845-1852
The antenna synthetic aperture radar (ASAR) imaging concept is introduced. We present the ASAR imaging algorithm to pinpoint the locations of secondary scattering off a platform from antenna radiation data. It is shown that a three-dimensional (3-D) ASAR image of the platform can be formed by inverse Fourier transforming the multifrequency, multiaspect far-field radiation data from an antenna mounted on the platform. This concept is demonstrated using the computed radiation data from the code Apatch, which employs the shooting and bouncing ray (SBR) technique. Furthermore, we develop a fast ASAR algorithm specially tailored for the SBR approach. By taking advantage of the ray tracing information within the SBR engine, we demonstrate that the fast approach can result in the same quality of image as the frequency-aspect algorithm at only a fraction of the computation time 相似文献
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Engen G. Johnsen H. Krogstad H.E. Barstow S.F. 《Geoscience and Remote Sensing, IEEE Transactions on》1994,32(2):340-352
An algorithm that extracts the directional ocean wave spectrum from synthetic aperture radar (SAR) ocean image spectra is implemented and applied to spaceborne C-band SAR data obtained from the ERS-1 satellite. The nonlinear iterative algorithm is based on the Hasselmann's forward spectral transform extended to include the range bunching effect. An analytic expression for the wave spectral increment is derived based on the exact gradient of the quasilinear ocean-to-SAR transform. Enhanced wave spectra have been obtained using first-guess wave spectra either from the numerical wave model WINCH operated by the Norwegian Meteorological Institute or synthesized from nondirectional wave data and meteorological conditions. The inverted spectra are compared to in situ directional wave data. It is concluded that the wave imagery from ERS-1 appears to be of excellent quality, and as soon as the backscatter modulation transfer functions are properly understood, satellite SAR data will be an important tool for enhancing and extending conventional wave measurements and results from numerical wave models 相似文献
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This paper addresses target discrimination in synthetic aperture radar (SAR) imagery using linear and nonlinear adaptive networks. Neural networks are extensively used for pattern classification but here the goal is discrimination. We show that the two applications require different cost functions. We start by analyzing with a pattern recognition perspective the two-parameter constant false alarm rate (CFAR) detector which is widely utilized as a target detector in SAR. Then we generalize its principle to construct the quadratic gamma discriminator (QGD), a nonparametrically trained classifier based on local image intensity. The linear processing element of the QCD is further extended with nonlinearities yielding a multilayer perceptron (MLP) which we call the NL-QGD (nonlinear QGD). MLPs are normally trained based on the L(2) norm. We experimentally show that the L(2) norm is not recommended to train MLPs for discriminating targets in SAR. Inspired by the Neyman-Pearson criterion, we create a cost function based on a mixed norm to weight the false alarms and the missed detections differently. Mixed norms can easily be incorporated into the backpropagation algorithm, and lead to better performance. Several other norms (L(8), cross-entropy) are applied to train the NL-QGD and all outperformed the L(2) norm when validated by receiver operating characteristics (ROC) curves. The data sets are constructed from TABILS 24 ISAR targets embedded in 7 km(2) of SAR imagery (MIT/LL mission 90). 相似文献
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Segmentation of polarimetric synthetic aperture radar data 总被引:6,自引:0,他引:6
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 相似文献
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张锡祥 《中国电子科学研究院学报》2006,1(2):107-113
合成孔径雷达(SAR)是当前的一种新型雷达体制,它既能测定目标的座标位置又能对目标成像,不论在军用还是在民用都有广泛的应用和广阔的发展前景,当然也就成了雷达干扰研究的重点对象。我们应用了几年的时间,分析了对SAR的干扰原理;推导出对SAR的干扰方程;做了多种仿真干扰试验,室内小功率模拟干扰试验和实际飞行干扰试验,获得大量干扰数据和干扰图像,证明了推导的干扰方程的正确性。还证明了常规脉冲雷达的干扰方程与SAR的干扰方程可以统一成一种方程。只是在计算干扰等效功率时,取不同的干扰压制系数即可。 相似文献
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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. Using this model, algorithms are generated for absolute and relative radiometric calibration of SAR imagery. These algorithms are parametrically exercised using radar system parameters from an existing airborne SAR system to determine their impact on the relative error bound 相似文献
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Gray A.L. Farris-Manning P.J. 《Geoscience and Remote Sensing, IEEE Transactions on》1993,31(1):180-191
It is shown that interference can be observed by coherently combining pairs of either X - or C -band airborne synthetic aperture radar (SAR) images from separate passes over the same test site. Coherence between separate images is obtained only if the aircraft is flown, and the data are processed in such a way that each resolution cell in the two images is viewed with very nearly the same geometry. Successful repeat-pass interferometric results were obtained from those passes flown by the CCRS Convair 580 aircraft with flight-line offsets of less than a few tens of meters. A summary of the experiment, the phase correction of nonrectilinear aircraft motion, and the subsequent data processing is provided 相似文献
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Space-time processing for multichannel synthetic aperture radar 总被引:2,自引:0,他引:2
Synthetic aperture radar (SAR) provides high-resolution images of a non-moving ground scene, but fails to indicate the presence and position of moving objects. As in airborne MTI (moving-target indication) systems the solution to this problem is to use an array of antennas or subapertures and several receiving channels (`MSAR', or multichannel SAR), and to apply multichannel clutter suppression. One of the most efficient methods is adaptive space-time processing (STAP), which can be simplified to frequency-dependent spatial processing in the Doppler domain. Some of these techniques applied to SAR are reviewed and illustrated with data gathered by the German experimental multichannel SAR system `AER-II' 相似文献
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A simple method of electronically processing synthetic aperture arrays is presented. The processing technique is based on the fact that synthetic aperture recorded signals are one-dimensional Fresnel zone-plate lenses. By essentially employing unfocussed processing methods on individual Fresnel zone-plates and then appropriately summing the results, a narrow beam "semifocussed" aperture may be formed, using only binary electronics. 相似文献
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合成孔径雷达(SAR)能够全天时全天候工作,在对地遥感领域具有广泛和深入的应用。视频SAR将SAR成像获得的空间维度信息拓展到时-空维度,可以获取更加丰富的遥感信息。传统SAR频段较低,导致合成孔径时间长,数据计算量大,高帧频输出难度很大;而低频段太赫兹波对目标细节感知能力强,合成孔径短,特别适合于微弱目标的视频感知。本文设计了一种工作在W波段的视频SAR系统,采用收发分置连续波固态前端体制,输出峰值功率1 W,最大发射带宽可达1 GHz;采用极坐标格式算法(PFA)结合GPU架构实现高帧率低延时成像。仿真试验表明,系统成像分辨力可达0.15 m,成像帧率约5 Hz。 相似文献
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Two sequences of operations necessary for implementation of high resolution image formation in strip and spotlight modes of the synthetic aperture radar (SAR) are presented. The sequences are mapped onto a mesh-connected SIMD architecture. The mapping includes not only parallel implementation of all the basic computation steps, but also all the necessary data transformation and communication operations. Detailed estimates of the processing times are provided for Hughes Research Laboratories Systolic/Cellular architecture.This work was partially supported by NSF grant No MIP-8714689 相似文献