地基SAR差分干涉测量大气扰动误差校正

在地基SAR(GB-SAR)差分干涉测量中,大气扰动影响是其测量精度误差的重要来源。提出了一种基于角反射器的地基SAR差分干涉测量大气扰动误差校正方法;该方法利用角反射器作为稳定控制点,根据其干涉相位的变化情况来分析观测区域大气扰动影响,从而实现对其扰动误差的校正。为了检验该校正方法的实用性,进行了三面角反射器外场形变测量中大气扰动误差校正实验,并将其校正结果与基于气象参数补偿法的校正结果进行了对比。结果表明,该校正方法具有很好的可靠性和精确性。     

旋滤波降噪在干涉SAR相位解缠中的应用研究

干涉相位图的降噪滤波，是干涉合成孔径雷达成像中必须的步骤之一。文中根据干涉条纹在切线方向变化最小的特点，利用沿切线方向的曲线窗口对干涉相位图进行旋滤波降噪，并通过对比不同的滤波结果及相应相位解缠结果，证明了旋滤波在保持条纹结构信息，消除噪声和提高相位解缠精度应用中的可行性和有效性。     

一种新的干涉相位图局部自适应滤波方法

为了有效提高对InSAR干涉相位噪声的抑制性能并充分保持干涉相位图细节信息,该文提出一种基于局部地形相位补偿和各向异性高斯滤波函数(AGF)的自适应复相位滤波方法。该方法首先利用局部频率估计方法补偿地形相位,以便于消除局部地形相位对滤波窗口内干涉相位的不利影响。然后,构造了尺度和方向自适应的AGF,并对同分布样本进行局部加权的方向滤波。这里,AGF尺度随相干系数等级自适应变化：在低相干区域,采用的大尺度AGF能够充分地抑制相位噪声;在高相干区域,采用的小尺度AGF能更好地保持相位细节信息。AGF方向根据最大加权相干积累准则确定,以选取同分布的滤波样本估计中心像素相位值。实验结果表明,与多种滤波方法相比,该文方法在减少干涉相位图残点和保持条纹边缘等方面均具有更好的性能。     

一种基于Non-Local Means的地基差分干涉雷达相位滤波改进方法

地基差分干涉雷达相位图中,往往含有大量相位噪声,严重影响相位解缠和形变测量结果.有鉴于此,本文提出一种改进的自适应非局部均值(Non-Local Means)组合滤波算法.该算法首先利用相干系数构造出可自适应的平滑参数模型,有效改善了Non-Local Means算法在滤波参数选择上的固定性.其次,利用维纳滤波可对空变...     

地基SAR基坑微形变监测方法研究

地基SAR作为一种新型地面遥感技术,因其高精度、全天候、设站灵活、实时连续观测等特点,在微形变监测领域具有广泛的应用前景。在深入研究了地基SAR微形变监测关键技术问题的基础上,结合基坑监测特点,采用加权圆周中值滤波去噪,提高干涉图信噪比,削弱噪声引起的相位差;提出了基于PSC网的气象改正,减小气象扰动影响,削弱大气相位差。并将改进方法应用到基坑监测实验。实验结果表明,通过加权圆周中值滤波和PSC网的气象改正有效地削弱地基SAR基坑监测中噪声和大气引起的相位变化,实现了亚毫米级的监测精度。为验证地基SAR监测的准确性,利用高精度全站仪进行了同步观测,监测结果表明二者高度一致,进一步说明了地基SAR技术用于基坑微形变监测的可靠性和可行性。     

干涉圆迹SAR的目标三维重建方法研究

圆迹合成孔径雷达（CSAR）的360全方位观测能够获取目标各方向的散射特征,但是单轨迹圆迹SAR对于强方向性目标高度向散射特征的获取能力非常弱。该文针对典型目标开展3维圆迹SAR干涉方法研究,开展了基于暗室实验的原理性验证,首次给出了实际坦克金属模型的干涉圆迹SAR的3维重建结果,验证了该方法的有效性,同时展示了3维重建与全方位观测相结合在目标精细特征描述方面具有的重要应用潜力。      

干涉合成孔径雷达相位滤波的一种新算法

该文着重就目前国际上研究的一个热点干涉合成孔径雷达成像中的相位滤波问题进行了讨论。提出了一种新的相应滤波方法,可适应干涉条纹方向的变化,十分适用于对干涉条纹密集的区域进行滤波。通过对德国X-SAR数据的处理检验该方法的效果,结果相当理想。此外,这种方法实现起来相当简单。     

基于总变分的干涉成像高度计相位滤波方法

宽幅干涉成像高度计采用双天线近天底角短基线干涉测高技术,实现对海洋亚中尺度现象的高时空分辨率与高精度观测。在反演海面高度(SSH)的过程中,干涉相位滤波处理是抑制随机相位噪声,保持相位边缘细节的重要环节。该文针对成像高度计干涉相位随机噪声方差在刈幅范围内分布不均匀的特点,基于宽幅干涉成像高度计相位模型,提出一种改进的总变分正则化滤波方法,可以有效抑制去平地后成像高度计的干涉相位噪声。通过仿真数据验证,滤波相位误差的标准差(STD)由0.32 rad降低至0.023 rad,且刈幅范围内STD最大偏差小于0.001 rad。改进的总变分滤波方法实现全刈幅干涉相位误差精度的均匀分布,较好地保持了分辨率和边缘信息,为海面高程精度的一致性提供有效保障。     

基于导航卫星的干涉SAR数据采集策略优选方法分析

基于导航卫星的干涉SAR(GNSS-InSAR)使用在轨导航卫星作为照射源,近地面部署接收机,利用导航卫星的星座特性以及重轨特性,可实现区域性的连续观测。对于场景1维/3维形变反演而言,需要连续时间的数据采集,由于导航卫星并非严格意义上的重轨,且重轨时间具有不确定性,原始数据冗余度高,数据对齐时截取量大,数据有效性低。该文针对GNSS-InSAR场景数据采集时间精确性问题,提出了一种重轨数据采集优化模型,该方法通过实际轨迹与TLE预测轨迹相结合的方式,通过空间相干系数的滑窗轨迹对齐,以获取相邻天导航卫星重轨时间间隔,实现精确的GNSS-InSAR数据采集,在降低原始数据冗余度下,保证数据的有效合成孔径时间。实测数据表明所提方法的有效性。      

干涉相位图的各向异性扩散方程滤波算法

该文提出了一种基于各向异性扩散偏微分方程抑制干涉合成孔径雷达(INSAR)相位噪声的算法。该算法给出了一种新的基于实数域干涉相位的扩散系数表达式,利用干涉相位图的局部统计特征,在干涉复图像中的均匀区域各向同性扩散,边缘区域各向异性扩散。试验结果表明,该算法在抑制干涉相位噪声的同时保持了条纹边缘细节信息,处理后的相位可以顺利展开。     

地基SAR多阈值迭代优化PS点选择方法

地基合成孔径雷达（Synthetic Aperture Radar,SAR）具有非接触、高精度、大区域、全天时全天候、24小时连续监测的技术优势,是滑坡灾害形变监测预警的重要技术手段,永久散射体(Permanent Scatterer,,PS)的探测是形变反演的关键技术,但使用阈值法筛选永久散射体时,人工调试多个阈值过程繁复且容易出现阈值设置不合理现象。本文提出一种多阈值优化算法,该算法针对地基雷达实现自动确定筛选永久散射体点的阈值,能减少人工设置阈值的不合理现象,省去更换监测场景后繁复阈值调试的过程,自动确定的阈值筛选结果达到比人工反复调整的阈值更优的效果。将该方法应用于四川茂县滑坡的形变监测及昌平凤山露天矿的PS点筛选实验,验证了算法的可行性。实验结果表明三阈值优化算法可以准确的确定阈值,筛选出正确的PS点集。      

EQUIVALENT BASELINE AND INTERFEROMETRIC PHASE OF CLUSTER SATELLITE SAR

The change of the equivalent baseline and interferometric phase of cluster SAR satellites is analyzed when the constellation circles around the Earth and the satellites rotate around the center at the same time. The letter provides assessment of baseline error and phase error which influence the precision of height measurement in the across-track interferometric mode. The mathematical model of cluster satellite movement is built, simulation analyses and the curve of height error are presented. The simulation results show that height measurement error can be compensated by the formulae derived in this letter, therefore, the Digital Elevation Models (DEM‘s) are recovered accurately.     

A Bayesian filtering technique for SAR interferometric phase fields

SAR interferograms are affected by a strong noise component which often prevents correct phase unwrapping and always impairs the phase reconstruction accuracy. To obtain satisfactory performance, most filtering techniques exploit prior information by means of ad hoc, empirical strategies. In this paper, we recast phase filtering as a Bayesian estimation problem in which the image prior is modeled as a suitable Markov random field, and the filtered phase field is the configuration with maximum a posteriori probability. Assuming the image to be residue free and generally smooth, a two-component MRF model is adopted, where the first component penalizes residues, while the second one penalizes discontinuities. Constrained aimulated annealing is then used to find the optimal solution. The experimental analysis shows that, by gradually adjusting the MRF parameters, the algorithm filters out most of the high-frequency noise and, in the limit, eliminates all residues, allowing for a trivial phase unwrapping. Given a limited processing time, the algorithm is still able to eliminate most residues, paving the way for the successful use of any subsequent phase unwrapping technique.     

利用残余点优选InSAR干涉相位条纹图的研究

该文基于相位展开中残余点的概念,深入研究了残余点发生概率与配准精度间的内在联系,根据所得出的模型,提出以残余点的数目作为衡量不同配准结果的准则。挑选出最佳的条纹图,从而最大程度地减小数字高程图中因配准所引起的误差．实际数据的研究表明,该方法简便精确、行之有效．     

基于注意力网络的地基SAR时序差分相位分类方法

地基合成孔径雷达(Ground Based Synthetic Aperture Radar,GBSAR)是目前露天矿山工作帮及排土场进行亚毫米级形变监测的主要技术手段之一,但监测过程中出现的多径效应造成的差分相位变化会被错误识别为形变.针对识别形变精度低的问题,本文开展了差分干涉相位时序特征表达方法的研究,并以此为基...     

Modeling and reduction of SAR interferometric phase noise in the wavelet domain

This paper addresses the problem of interferometric phase noise reduction in synthetic aperture radar interferometry. A new phase noise model in the complex domain is introduced and validated by using both simulated and real interferograms. This noise model is also derived in the complex wavelet domain, where a novel noise reduction algorithm, which is not based on a windowing process and without the necessity of phase unwrapping, is addressed. The use of the wavelet transform allows to maintain the spatial resolution in the filtered phase image and prevents to filter low coherence areas. By using both, simulated as well as real interferometric phase images, the performance of this algorithm, in terms of noise reduction, spatial resolution maintenance, and computational efficiency, is reported and compared with other conventional filtering approaches.     

交轨干涉SAR涌浪干涉相位模型及数值模拟

建立了包含海表面高度和速度聚束的交叉轨迹干涉合成孔径雷达(AcrossTrack Interferometric Synthetic Aperture Radar,XTI-SAR)涌浪干涉相位模型,得到了涌浪成像的解析表达式.进一步研究了XTI-SAR沿方位向传播的涌浪成像机制.定义二次谐波振幅与基波振幅比率来表征成像非线性,通过比较XTI-SAR和沿轨迹干涉合成孔径雷达(Along-Track Interferometric Synthetic Aperture Radar,ATI-SAR)相位的二阶调和分量,分析不同海况和干涉SAR参数情况下的数值模拟,结果表明:当速度聚束弱时,XTI-SAR相位比ATI-SAR相位具有较强的非线性,ATI-SAR比XTI-SAR更适合测量海浪.当速度聚束强时,XTI-SAR相位比ATI-SAR相位具有较弱的非线性,XTI-SAR比ATI-SAR更适合测量海浪.     

SAR interferometric signatures of forest

The potential of SAR interferometry for forest mapping and monitoring is discussed. It is shown that forest can clearly be discriminated from other land categories. Furthermore it is possible to distinguish a number of forest types. The presented approach is based on the SAR interferometric correlation and the backscatter intensities using ERS-1 SAR repeat-pass data. Baseline, time interval, and seasonal dependences were analyzed, substantiating a wide applicability of the approach. Data over an Alaskan test site were used to extend the results found over temperate forest to boreal forest and to demonstrate the potential of the described technique over remote areas. In addition, repeat-pass SAR interferometry was found to be particularly sensitive to change. Examples for the recognition of freezing, mechanical cultivation of agricultural fields, and canopy growth are shown     

Using APES for interferometric SAR imaging

We present an adaptive finite impulse response (FIR) filtering approach, which is referred to as the Amplitude and Phase EStimation (APES) algorithm, for interferometric synthetic aperture radar (SAR) imaging. We compare the APES algorithm with other FIR filtering approaches including the Capon and fast Fourier transform (FFT) methods. We show via both numerical and experimental examples that the adaptive FIR filtering approaches such as Capon and APES can yield more accurate spectral estimates with much lower sidelobes and narrower spectral peaks than the FFT method. We show that although the APES algorithm yields somewhat wider spectral peaks than the Capon method, the former gives more accurate overall spectral estimates and SAR images than the latter and the FFT method.     

Simulation of interferometric SAR response for characterizing thescattering phase center statistics of forest canopies

A coherent scattering model for tree canopies is employed in order to characterize the sensitivity of an interferometric SAR (INSAR) response to the physical parameters of forest stands. The concept of an equivalent scatterer for a collection of scatterers within a pixel, representing the vegetation particles of tree structures, is used for identifying the scattering phase center of the pixel whose height is measured by an INSAR. Combining the recently developed coherent scattering model for tree canopies and the INSAR Δk-radar-equivalence algorithm, accurate statistics of the scattering phase-center location of forest stands are obtained numerically for the first time. The scattering model is based on a Monte Carlo simulation of scattering from fractal-generated tree structures, and therefore is capable of preserving the absolute phase of the backscatter. The model can also account for coherent effects due to the relative position of individual scatterers and the inhomogeneous extinction experienced by a coherent wave propagating through the random collection of vegetation particles. The location of the scattering phase center and the correlation coefficient are computed using the Δk-radar equivalence simply by simulating the backscatter response at two slightly different frequencies. The model is successfully validated using the measured data acquired by JPL TOPSAR over a selected pine stand in Raco, MI. A sensitivity analysis is performed to characterize the response of coniferous and deciduous forest stands to a multifrequency and multipolarization INSAR in order to determine an optimum system configuration for remote sensing of forest parameters