基于几何配准的多模式SAR影像配准及其误差分析

星载合成孔径雷达影像干涉处理时所需方位向配准精度因成像模式的差异而有所不同,目前在精密轨道条件下以几何配准为基础辅以影像信息的配准方案因其严格的理论模型和较高的精度成为干涉处理的首选。本文以TerraSAR-X影像为例,论证了不同成像模式影像所需的配准精度和卫星轨道精度,并通过理论分析和试验证明了精密轨道条件下,利用几何配准即可满足TerraSAR-X等卫星的条带模式影像干涉处理的需要;聚束模式影像需要在几何配准的基础上利用影像相干性或谱分集进一步优化配准结果。鉴于增强谱分集偏移量估计精度最高,本文进一步利用增强谱分集对比分析了不同轨道不同DEM条件下的几何配准误差。研究结果表明:卫星轨道切向误差是几何配准的主要误差源,目前常用3种DEM几何配准差异远小于0.001个像素,均可满足Sentinel-1影像干涉配准的需要。     

Level Set Method for SAR Image Coregistration

In this letter, a novel approach for the coregistration of synthetic aperture radar (SAR) images is proposed based on the level set method. The features of regions are detected by segmenting the images, and the images are coregistered by matching the detected features. The energy functional of level sets is formulated with respect to detecting and matching features. The coregistration is achieved by minimizing the energy functional. Compared with the conventional tie-patch method, the results on a series of simulated experiments and real SAR data demonstrate the feasibility of the proposed approach.      

附带星历参数的星载合成孔径雷达影像自动配准算法

Fourier-Mellin不变性对称相位匹配滤波器,即symmetric phase-only matched flitering of fourier-mellin invariant(SPOMF-FMI)能解决影像配准的平移、旋转和放缩几何变换问题;然而,该方法在实际应用中具有局限性,包括图像几何尺度和图像非线性几何畸变处理能力.为了克服上述缺陷,提出了一种附带星载参数的星载合成孔径雷达(synthetic aperture radar,SAR)影像自动配准算法.该方法采用由粗到精匹配策略,由距离-多普勒影像粗匹配和改进SPOMF-FMI影像精匹配组成.使用Radarsat-1和ENVISAT ASAR影像做实验,结果表明本方法在处理重复轨道或相同升、降轨星载SAR影像(即确保相似影像纹理测度)配准问题时,能达到子像素级的配准精度.     

精密轨道支持下的哨兵卫星TOPS模式干涉处理

哨兵卫星采用TOPS模式成像,为确保影像干涉相位偏差小于3°,方位向配准精确度需达到0.001个像素。本文论证了哨兵卫星精密轨道条件下进行几何配准即可达到较高的配准精度,满足增强谱分集进行方位向残余偏移量估计的前提条件,并基于DORIS软件实现哨兵卫星TOPS模式影像的几何配准和增强谱分集优化配准处理。地表方位向形变等信号可导致Burst干涉图之间发生相位跳变,并对增强谱分集估计几何配准残余偏移量时产生干扰,本文开展了相关的理论分析和数据处理试验,提出粗差探测方法消除相位跳变对增强谱分集配准的干扰。     

Spatial Interpolation Using Fuzzy Reasoning

Spatial interpolation is an important feature of a Geographic Information System, which is the procedure used to estimate values at unknown locations within the area covered by existing observations. In this paper, we describe a conservative spatial interpolation technique that incorporates the advantages of local interpolation, Euclidean interpolation, and conservative fuzzy reasoning, and a dynamic fuzzy–reasoning–based function estimator with parameters optimised by a genetic algorithm. The main objective of this paper is to formulate a computationally efficient spatial interpolation technique similar to the IDWA technique that can be used in real time application. The main feature of our spatial interpolation technique is a capability for spatial interpolation and extrapolation in a higher–dimensional space. Examples from a rainfall spatial interpolation problem are used to illustrate the applicability of the proposed technique.     

Coregistration Based on Three Parts of Two Complex Images and Contoured Windows for Synthetic Aperture Radar Interferometry

The coregistration of complex image pairs is a very important step in synthetic aperture radar interferometry (InSAR) data processing. This letter proposes a novel coregistration method that only needs three arbitrary parts of the two complex images instead of four parts in the existing coregistration methods. This method constitutes an integrated three-part method for InSAR data processing with our contoured-correlation-interferometry method for phase-image generation. Saving one part transmission makes a significant advantage when processing SAR images on satellites. Furthermore, we demonstrate that, by means of using fringe contoured windows instead of squared windows, the accuracy of the coregistration for both the three-part coregistration method and the existing methods can be improved considerably     

Optimum Data Vector Approach to Multibaseline SAR Interferometry Phase Unwrapping

Phase unwrapping is a key problem not only in all quantitative applications of synthetic aperture radar (SAR) interferometry but also in other fields. In this letter, a new phase unwrapping approach is investigated. Our study is based on the model of the optimum data vector. In order to autocoregister the SAR images, the proposed method takes advantage of the multibaseline optimal weighted joint data vector by extracting all the coherence information available in the neighboring pixels. Moreover, the method employs the projection of the joint signal subspace onto the corresponding noise subspace to estimate the unwrapped interferometric phases (or the terrain heights). The proposed method can accurately determine the dimensions of the noise subspace and provide the robust unwrapped interferometric phases even in the presence of the large image coregistration errors. Moreover, the multibaseline processing idea is a combination of data optimization, image coregistration, interferogram filtering, and phase unwrapping.     

利用SAR影像配准偏移量提取地表形变的方法与误差分析

单一的InSAR观测技术可提取地表沿雷达视线方向(LOS)上的一维位移,而利用SAR影像配准过程中的同名像素偏移量可提取地表沿雷达方位向(近南北向)与距离向(近东西向)的二维形变场,与LOS方向的一维形变形成优势互补。本文在分析SAR影像配准偏移量提取地表形变场方法的基础上,推导建立了雷达方位向与距离向形变提取的误差模型,探讨了该方法提取地表形变的主要误差源。以Bam地震ASAR影像和玉树地震PALSAR影像为数据源,分别开展同震形变场的提取与误差分析试验,结果表明,基于SAR像素配准偏移量提取同震形变场的精度主要受匹配窗口尺寸与过采样因子影响,形变提取误差随匹配计算窗口的增大而减小,形变提取精度随过采样因子的增大有适量提高,地形起伏效应在高差较大的SAR影像区域中表现较为显著。     

一种基于曲线SAR的三维目标特征提取与自聚焦新算法

曲线合成孔径雷达（Curvilinear Synthetic Aperture Radar,简称曲线SAR）是一种新的三维成像模式，通过让载机作曲线飞行，曲线SAR系统能同时在方位维和高度维形成大的合成孔径。本文提出一种曲线SAR的三维目标特征提取和自聚焦新方法。新方法是建立在一种灵活的接收数据模型之上的参数化的新方法。仿真实验证明了所提方法的有效性。     

联合实、复相关函数的干涉SAR图像配准方法

SAR复图像配准是干涉SAR数据处理中的关键步骤之一,配准精度直接影响后续产品的质量。提出一种基于联合实、复相关函数的星载干涉SAR图像配准方法。首先,在分析已有配准测度函数各自特性的基础上,结合国际上干涉SAR数据处理经验,认为在全球干涉测量任务背景下,相关函数是一种稳健、普适性的干涉SAR图像配准测度函数。然后,针对相关函数存在实、复相关计算,分析实、复相关函数各自的特点以及适应情况,提出配准灵敏度准则,从而能够有效地自适应地选取相应的配准相关度量。最后,给出配准算法的详细实现步骤。复杂地区的实测数据处理结果验证了方法的有效性。     

Bistatic Spotlight SAR Processing Using the Frequency-Scaling Algorithm

This letter derives the bistatic point target spectrum for the translational invariant case. Based on the derived spectrum and the linear approximation of the bistatic range cell migration factor, a bistatic frequency-scaling algorithm (FSA) is proposed for spotlight synthetic aperture radar data processing. This algorithm leads to a very precise and efficient processing since it performs the focusing in the frequency domain and no interpolation is required in the whole processing chain. In addition, it is shown that the case considered in the monostatic FSA is a specialization of the more general one considered in this letter. Finally, simulation results are provided to illustrate the validity of the presented approach.     

Tropospheric corrections to SAR interferometry from GPS observations

Interferometric synthetic aperture radar (InSAR) techniques have been recognized as an ideal tool for many ground deformation monitoring applications. However, the spatially and temporally variable delay of the radar signal propagating through the atmosphere is a major limitation to accuracy. The dominant factor to be considered is the tropospheric heterogeneity, which can lead to misinterpretation of InSAR results. In this paper, a between-site (BS) and between-epoch (BE) double-differencing algorithm for the generation of tropospheric corrections to InSAR results based on GPS observations is tested. In order to correct the radar results on a pixel-by-pixel basis, the GPS-derived corrections have to be interpolated. Using experimental data it has been found that the inverse distance weighted and kriging interpolation methods are more suitable than the spline interpolation method. Differential corrections as large as several centimeters may have to be applied in order to ensure sub-centimeter accuracy for the InSAR result. The algorithm and procedures described in this paper could easily be implemented in a continuous GPS network data center. The interpolated image of BS, single-differenced tropospheric delays can be derived as a routine product to assist radar interferometry.     

Automatic subpixel registration for a tunable hyperspectral imaging system

Hyperspectral imagery of the Earth's surface is increasingly being acquired from aerial platforms. The many bands acquired by typical hyperspectral instruments are collected either in a push-broom, scanning, or staring fashion. Staring methods can be used in ground- and aerial-based applications and have the advantage of readily producing coherent images. Staring remote sensing instruments need some form of coregistration to match band-to-band pixel locations because it takes some time for the instrument to acquire images and save them as the aerial platform moves above the target scene. A well-known method for registration is the phase correlation (PC), which may be used to register images to an accuracy of /spl plusmn/1 pixels. This letter reports an enhancement to the PC method that allows for subpixel registration of hyperspectral images. The x-y location at which the maximum correlation function occurs is fitted with a cubic interpolation to find the maximum. This method was implemented to recover subpixel rotation and translation accuracy from an airborne hyperspectral imaging system, dubbed the Portable Hyperspectral Tunable Imaging System. Results showed that the approach improves up to 9.5% of the normalized cross correlation between wavebands in comparison with the PC method alone.     

GPS卫星精密星历内插方法比较分析

借助GPS卫星精密星历,使用Lagrange多项式插值法和Chebyshev多项式拟合法内插出GPS卫星的瞬时位置,确定了插值精度与插值阶数的关系,并对这两种方法的优缺点进行了对比分析。计算结果表明:内插卫星瞬时坐标时所选取的插值阶数不应过高或过低,三维坐标分量在最佳插值精度时选取的插值阶数并不完全相同,Chebyshev多项式拟合法相比Lagrange多项式插值法的插值效果更好。因此,建议在优先选用Chebyshev多项式拟合法内插卫星瞬时坐标的同时,对三维坐标分量分别选取不同的插值阶数,以达到最优的插值精度。     

基于激光三维扫描技术的一种分类出地面点的方法

激光三维扫描技术可以直接获取地面三维数据,比传统测量方法具有高精度、高密集、高效率和成本低的优点.数据的分类是激光三维扫描技术中的关键问题之一.本文通过反复建立三角形的过程分类出地面点,并在实例中应用,效果良好.本方法简单易行,但是还存在着一些缺点有待改进.     

全球MODIS气温数据的修正秩克里金插值分析

高维数据插值是大数据分析的一个基本内容,传统克里金插值方法的计算复杂度,是O(n3),即随数据观测量的增大其计算复杂度以3次方速度增长,无法满足实时性应用需求强的克里金插值。修正秩克里金(FRK)方法通过矩阵分解降低大维矩阵的运算维数来简化矩阵计算,提高计算速度。在大数据分析背景下,借助FRK方法对全球MODIS气温数据进行统计建模并计算实现气温数据的插值分析。将其与普通克里金(OK)作对比实验,结果表明,相较于OK方法,FRK方法的插值精度并没有降低;在计算效率方面,使用FRK方法进行插值时,随数据量增大,耗时程度趋于缓慢平稳增长,而同一环境下的OK方法耗时随数据量增大呈指数增长趋势。相对于传统克里金方法,FRK能够在保证插值精度的同时显著降低其计算复杂度,缩短插值时间。     

基于卫星精密轨道数据的复图像对精确配准

图像精确配准是InSAR数据处理中关键步骤之一。在介绍复图像对配准过程后,利用Doris软件逐步实现复图像对粗配准、精配准;深入分析配准过程中相干系数的变化,总结干涉条纹图、相干图特点,证实基于精密卫星轨道数据可以实现图像对精确配准的可行性。     

滑动聚束模式SAR影像干涉处理方法

合成孔径雷达聚焦成像时,因地球旋转和传感器姿态控制误差而产生的非零多普勒中心在聚焦影像方位线中引入了线性相位,因此在干涉处理时方位线不能作为基带信号进行重采样。为了确保相位信息在重采样过程中不出现损失,一般采用内插核调制的方法完成方位线重采样。滑动聚束模式影像因成像的特殊性,聚焦影像的多普勒中心分布更加复杂,其方位线为时变信号。分析了滑动聚束模式影像点目标的多普勒历程,多普勒中心在方位线的变化规律,时变信号的内插方法,并通过模拟实验验证非零多普勒中心对内插精度的影响,最后对DORIS软件重采样环节进行改进,即采用新的多普勒中心表达式对内插核进行调制完成影像重采样,实现TerraSAR-X卫星滑动聚束模式影像的干涉处理。     

基于FFT的快速SAR分布目标回波模拟算法

大面积分布目标的合成孔径雷达 (SAR)回波模拟需要大量的运算 ,文中提出了一种合成孔径雷达回波模拟的快速算法 ,算法利用时域插值和FFT来缩减运算量 ,对于大面积目标回波模拟时 ,该算法有很高的效率。文中详细分析sinc函数插值所带来的误差以及补偿方法 ,并在次基础上提出了一种利用增采样插值方法 ,该方法以增加少量运算为代价 ,使得模拟精度的大幅度提高。文中比较了传统方法和基于FFT的快速SAR分布目标回波模拟算法的模拟结果 ,证明了这种快速算法确实行之有效