共查询到20条相似文献，搜索用时 62 毫秒
1.
A semiempirical algorithm for SAR wave height retrieval and its validation using Envisat ASAR wave mode data 总被引：2，自引：2，他引：0
Many synthetic aperture radar(SAR) wave height retrieval algorithms have been developed.However,the wave height retrievals from most existing methods either depend on other input as the first guess or are restricted to the long wave regime.A semiempirical algorithm is presented,which has the objective to estimate the wave height from SAR imagery without any prior knowledge.The proposed novel algorithm was developed based on the theoretical SAR ocean wave imaging mechanism and the empirical relation between two types of wave period.The dependency of the proposed model on radar incident and wave direction was analyzed.For Envisat advanced synthetic aperture radar(ASAR) wave mode data,the model can be reduced to the simple form with two input parameters,i.e.,the cutoff wavelength and peak wavelength of ocean wave,which can be retrieved from SAR imagery without any prior knowledge of wind or wave.Using Envisat ASAR wave mode data and the collocated buoy measurements from NDBC,the semiempirical algorithm is validated and compared with the Envisat ASAR level 2 products.The root-mean-square-error(RMSE) and scatter index(SI) in respect to the in situ measurements are 0.52 m and 19% respectively.Validation results indicate that,for Envisat ASAR wave mode data,the proposed method works well. 相似文献
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GF-3号SAR卫星遥感围填海监测方法研究——以大连金州湾为例 总被引：1，自引：0，他引：1
依据不同围填海类型在高分三号(GF-3)合成孔径雷达(synthetic aperture radar,SAR)卫星遥感影像上可分性,建立围填海遥感分类体系及相应的围填海类型解译标志,进而分析SAR图像岸线提取方法,构建GF-3围填海监测技术流程。采用几何主动轮廓模型进行GF-3 SAR影像自动提取海岸线,获得围填海专题图。通过外业精度调查验证GF-3 SAR卫星遥感影像可以有效获取围填海信息。 相似文献
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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 situ wave measurements made by a pitch-and-roll buoy. The comparison revealed that theX -band SAR detected all gravity waves independent of radar look direction, while theL -band SAR detected all range-traveling gravity waves but failed to detect waves in three of four cases in which the waves were traveling within 25° of the azimuth direction. The analysis also indicates that azimuth-traveling waves appear longer and more range-traveling in the SAR imagery than observed by in situ instrumentation. It is postulated that degraded azimuth resolution due to scatterer motion is responsible for these observations. 相似文献
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The observation of tidal patterns, currents, and bathymetry with SLAR imagery of the sea 总被引：3，自引：0，他引：3
Work done until 1978 on the visualization of currents, bathymetry, internal waves, etc., in SLAR imagery of the sea is reported. It did not receive much attention until the SEASAT SAR imagery showed these effects on a global scale. Although we know, qualitatively, how these images come about we are yet far from knowing how to extract more quantitative data from them on depth, current speed, etc. Much research effort is still needed here and for this work a simple real-aperture SLAR can be a very useful tool. 相似文献
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Determination of sea ice motion using digital SAR imagery 总被引：1，自引：0，他引：1
Using digital SEASAT synthetic aperture radar (SAR) imagery, high-precision densely sampled maps of ice motion have been derived by tracking ice features to determine the small-scale spatial variability of ice deformation. The digital SAR imagery was processed to remove geometric distortions and located on the Earth to an accuracy of about 100 m utilizing an algorithm based on the spacecraft orbital data and the characteristics of the SAR data collection system, independent of attitude information or ground reference points. Radiometric enhancement of the imagery using a variable linear stretch algorithm was performed to remove a system-related gradient and improve the identification of sea ice features. Using ice features common to an overlapping pair of images, vector plots of ice motion were then produced. Examples of ice motion are shown in the marginal ice zone and in the central ice pack where mean displacements of 15.3 km/day and 5.0 km/day were measured, respectively. Considering errors in Earth location with those in feature identification an overall error of 150-200 m in displacement measurements was estimated. The ice motion vector plots indicate a high degree of spatial deformation, demonstrating the potential value of spaceborne SAR data for production of precision large-scale maps of ice displacement with a spatial resolution of ice deformation on scales much less than 100 km. 相似文献
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随着合成孔径雷达（ＳＡＲ）的应用研究程度的深入，要求较为精确地掌握目标体的雷达后向散射特征，这样必须对ＳＡＲ图象进行真实值的定标与校验。本文基于基本散射理论对ＳＡＲ系统的增益进行分解，指出各个相关参数的获取方法，最后给出定标和数据处理流程图 相似文献
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An ice-motion tracking system at the Alaska SAR facility 总被引：2，自引：0，他引：2
Kwok R. Curlander J.C. McConnell R. Pang S.S. 《Oceanic Engineering, IEEE Journal of》1990,15(1):44-54
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An important research area in oceanographic surveying and mapping is to obtain submarine topography by remote sensing technique, especially by SAR imagery. In this article, problems related to SAR imagery are analyzed to provide references for the further research. 相似文献
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I~IOXThe image technology of the synthetic aperture radar (SAR) is one of most important advances in spaceberne microwave remote sensing (Larson et al., 1976). It has extensive application in the ocean remote sensing, such as inversion of the sea subdue winds and currentS, reconstruction of underwater hatom topography and so on. Owing tO the high conductivity of sea water, an electromagnetic wave actually cannot penetrate into the sea water, with extremely smallPenetration depth (abbot 1 c… 相似文献
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用合成孔径雷达图像反演浅海水下地形的一种方法 总被引：2，自引：0，他引：2
海流与海底地形的相互作用导致了海表面的粗糙起伏,从而引起对海面观测的雷达散射截面的变化。在浅海海流速度垂直分布廓线为均匀的假定下,由流体连续性方程和驰豫时间近似下流体力学弱相互作用的理论,已证明雷达散射截面的空间变化正比于海流方向上海流速度变化的梯度。研究了合成孔径雷达(SAR)对海面的观测图像在无槽道信息和海流方向预知条件下,提出用散射系数的二维相关函数确定海流方向。在海流速度和方向已知条件下,推导了由雷达散射截面的空间变化迭推反演浅海水下地形的公式,并研究了航天飞机SIR-CSAR在我香港特区海域的二维图像反演浅海水下地形的应用。 相似文献
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针对中国南海ERS-2／SAR三维对流涡旋图像,分别利用Young的协方差方法和惯性子域方法,反演了对流海洋大气边界层高度、海洋大气边界层垂直对流尺度速度、表面浮力通量、Obukhov长度、稳定性校正后的海面风速和海面风速稳定性校正因子。结果表明,2种反演方法的结果符合较好,在一定程度上说明利用协方差方法和惯性子域方法从卫星SAR图像反演海洋大气边界层参数的有效性。 相似文献
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V. G. Bondur V. A. Dulov A. B. Murynin Yu. Yu. Yurovsky 《Izvestiya Atmospheric and Oceanic Physics》2016,52(9):888-903
The results of studying sea-wave spectra in a wide wavelength range using high resolution (0.5–1.0 m) satellite optical imagery spectra and the results of measurements carried out from an oceanographic platform using string-wave recorders, stereo system, and drifting wave buoys are presented in this paper. The wave spectra retrieved from satellite imagery and sea-truth data have been compared. A comparison has shown the adequacy of the purposely developed retrieval methods. Power approximation indices for spatial spectra in the 0.04–5.0-m wavelength range have been found. It has been shown that the wave spectra measured experimentally by satellite-based and in-situ methods best approximate the Toba spectrum. 相似文献
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Using surface wave parameters and a high-resolution surface wind field derived from Synthetic Aperture Radar (SAR) image mode
data, we have investigated the spatial modification of SAR spectra. We found a surface wind front, formed by sheltering effect
of the Kii Mountains, separating high and low wind-speed regions in a sea area of an European Remote-Sensing Satellite (ERS)
SAR image off the Kii Peninsula. A swell system propagating westward dominates in the whole sea area covered by the SAR image.
The wavelength retrieved from the SAR spectra in the sheltered (non-sheltered) region is longer (shorter). Since the distributions
of surface wave parameters and surface wind speed are so well correlated, it can be considered that the SAR spectra are modified
differently by the sheltered/non-sheltered surface winds. In order to examine the phenomena observed on the SAR image we have
estimated the wind-wave SAR spectrum using the SAR surface winds, a wind-wave spectrum model and a SAR wave imaging model.
We assume that the SAR spectrum related to the swell is homogeneous in the area imaged by SAR, and that the SAR spectrum of
the wind-wave components causes the observed SAR spectra modification. Differences between the observed SAR spectra and the
estimated SAR spectra in the sheltered and non-sheltered regions agree well with each other. In the present case, it can be
concluded that the observed SAR spectra can be regarded as a linear combination of the wind-wave SAR spectra and the swell
SAR spectra. 相似文献
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针对机载合成孔径雷达(SAR)对海探测特点,采用多入射角法从SAR数据本身得到与海浪参数反演区域时空匹配的同步海面风速和风向,并结合线性变换关系,计算得到海浪初猜谱对应的仿真SAR图像谱,将仿真SAR图像谱和观测SAR图像谱输入代价函数中进行迭代运算,通过非线性方程的解算得到最适海浪谱;采用交叉谱法去除海浪传播180°方向模糊,最终得到海浪参数。论文提出的基于同步风场的机载SAR海浪参数反演方法,充分利用了机载SAR海洋环境探测的优势,解决了传统SAR海浪参数反演中初猜谱构造依赖外部风场的问题,机载同步飞行试验的海浪参数反演结果与浮标观测值的有效波高、波向的均方根误差分别为0.23 m和13.23°,验证了该方法的有效性,可为机载SAR海浪参数反演业务化提供支持。 相似文献
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Orbital motion of azimuth waves imposes differential Doppler shifts on wave imagery as seen by a SAR. This paper shows that these Doppler shifts are a function only of the wave and sensor geometry, and are not a function of SAR parameters. The azimuth wave reflectivity so modulated is equivalent to a redistributed scatterer density which can be used as an input with the SAR modulation transfer function for general distributed scenes to derive the azimuth wave image. The static scatterer density is calculated for a variety of sea states. Wave accelerations are not of first-order importance. Scatterer fade (decorrelation) is of central importance, as it impacts the SAR transfer function that is effective in wave imaging. 相似文献
17.
Employing a synthetic aperature radar (SAR) imaging model based on fundamental models of nonlinear hydrodynamics, electromagnetic scattering from a two-scale surface, and SAR imaging of a time-variant scene, the optimal (minimum mean-square error) estimates of the parameters of a sinusoidal, long gravity wave, and the short gravity wave ensemble are found in an efficient recursive form and their performance evaluated, generally by numerical simulation, in a one-dimensional stationary version. An application is made to Seasat-SAR complex imagery. 相似文献
18.
The main objective of this paper is to propose a newly developed ocean Significant Wave Height(SWH) retrieval method from Envisat Advanced Synthetic Aperture Radar(ASAR) imagery. A series of wave mode imagery from January, April and May of 2011 are collocated with ERA-Interim reanalysis SWH data. Based on the matched datasets, a simplified empirical relationship between 22 types of SAR imagery parameters and SWH products is developed with the Genetic Algorithms Partial Least-Squares(GA-PLS) model. Two major features of the backscattering coefficient σ_0 and the frequency parameter S_(10) are chosen as the optimal training feature subset of SWH retrieval by using cross validation. In addition, we also present a comparison of the retrieval results of the simplified empirical relationship with the collocated ERA-Interim data. The results show that the assessment index of the correlation coefficient, the bias, the root-mean-square error of cross validation(RMSECV) and the scattering index(SI) are 0.78, 0.07 m, 0.76 m and 0.5, respectively. In addition, the comparison of the retrieved SWH data between our simplifying model and the Jason-2 radar altimeter data is proposed in our study.Moreover, we also make a comparison of the retrieval of SWH data between our developed model and the wellknown CWAVE_ENV model. The results show that satisfying retrieval results are acquired in the low-moderate sea state, but major bias appears in the high sea state, especially for SWH5 m. 相似文献
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It is shown that sea-surface height may not be estimated directly from the phase of complex synthetic aperture radar (SAR) imagery. 相似文献
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Different ocean features usually appear in synthetic aperture radar (SAR) images simultaneously. This makes the image compli- cated and hard to understand. Because of lower signal-to-noise rate , it is much more difficult to separate different ocean features than to separate different land features. A completely novel method is presented to separate ocean features from multifrequency po- larimetric SAR imagery. AIRSAR data from Jet Propulsion Laboratory (JPL), National Aeronautics and Space Administration (NASA) are used in the case studies and good results are achieved. 相似文献