国产高分三号卫星干涉测量试验

主要利用国产高分三号(GF-3)卫星数据通过合成孔径雷达干涉测量(interferometric synthetic aperture radar,InSAR)技术提取试验区域数字高程模型(digital elevation model,DEM).首先介绍了GF-3卫星及其主要成像模式;然后介绍了InSAR数据处理过程及其关键技术,包括基线估计、影像配准、相位解缠等,并介绍其典型算法;最后利用GF-3试验数据提取DEM并对其进行精度评价.试验验证了目前国产SAR(synthetic aperture radar)卫星在干涉成像、干涉测量方面的能力.     

高分辨率雷达卫星COSMO-SkyMed干涉测量生成DEM的实验研究

介绍了COSMO-SkyMed对地观测系统,分析了高分辨率SAR传感器和Tandem观测星座与相干性之间的关系,并利用间隔1 d的COSMO-SkyMed Tandem数据生成了祁连山区的DEM。提出通过对无地形变化的差分干涉相位进行滤波来提取大气和轨道误差引起的测量偏差,探讨了实验干涉数据去相干的因素,并将生成的DEM与ASTER GDEM进行了对比。     

雷达卫星自动成图的精密干涉测量关键技术

本文介绍用于未来自动成图的数字摄影测量智能化新方法之一：精密干涉测量新方法。它采用合成孔径雷达干涉（interferometric SAR,InSAR）技术获取极高精度的地形信息,现已成为最有效的全球测图手段之一。本文提出了面向全球测图的精密干涉测量系统技术,其中包含测量检校技术、数据处理技术及数据后处理技术。首先,需采用定标设备对几何及干涉参数进行测量检校,主要包括方位向时间延迟、距离向时间延迟、大气延迟及基线误差等。其次,需采用检校参数进行干涉数据处理,获取高精度DEM数据,干涉数据处理的关键技术包括相位初值确定方法等。最后,采用区域网平差、长短基线组合及升降轨融合等后处理技术完成全球DEM数据的生产和精度的逐步提升。本文采用6景覆盖陕西地区的TanDEM-X数据进行了数据处理及后处理试验,并获取了山地区域高程精度为5.07 m,低相干面积为0.8 km²的DEM数据,这为我国1∶50 000乃至1∶25 000比例尺全球测图提供了技术参考。     

InSAR林下地形测绘方法与研究进展

传统光学遥感技术手段在森林覆盖区难以准确获取林下地形,原因在于其只能测量森林冠层顶部高程。微波信号能够穿透森林冠层并记录森林垂直结构信息,为解决林下地形测绘难题带来了契机,如何准确获取林下地形已成为微波遥感领域的研究热点。首先介绍了面向林下地形测绘的合成孔径雷达（synthetic aperture radar,SAR）干涉测高原理及数据获取手段。然后对利用SAR进行林下地形测绘的方法进行了分类,主要包括基于合成孔径雷达干涉测量（interferometric synthetic aperture radar,InSAR）、极化合成孔径雷达干涉测量（polarimetric InSAR,PolInSAR）及基于多基线InSAR/PolInSAR数据的层析SAR（tomographic SAR,TomoSAR）技术的林下地形测绘方法,并介绍了上述3种方法的应用进展。最后在此基础上,从数据获取、误差改正及散射模型构建3个角度分析了林下地形测绘所面临的问题。     

ENVISAT/ASAR多角度干涉雷达数据山区DEM生成及精度分析

在地形起伏较大的山区用干涉SAR生成DEM时,合适的入射角是获取高精度DEM的重要参数之一.本文基于ENVISAT/ASAR多角度干涉雷达数据,SRTM 90米分辨率的DEM以及1:5万的数字化DEM数据,从定性和定量的角度比较和分析了干涉SAR在获取山区DEM时,入射角对DEM精度的具体影响.结果表明:对于ASAR的多入射角干涉雷达数据,在不同入射角条件下由于雷达叠掩和透视收缩的影响,获取的DEM精度差别很大,入射角带来的影响相当显著,比如IS2和IS4角度得到的DEM的精度差超过了6米.因此,在山区干涉SAR地形成图时,必须对入射角的大小进行严格的选择.     

利用参数独立分解的星载SAR干涉测量检校方法

在星载干涉合成孔径雷达中，干涉参数的准确性对高程精度起着至关重要的作用。传统干涉测量检校方法往往将影响量级不同的干涉参数组合在一起解算，无法精确获得每项干涉参数的修正量。针对此问题，本文提出一种利用参数独立分解的干涉测量检校方法。首先，根据三维重建模型，确定与干涉SAR测高有关的参数；随后，在确保几何参数精度的前提下，对干涉参数的敏感度进行定量分析；最后，采用独立检校算法解算每一项干涉参数误差，完成干涉测量检校模型的建立。本文选择陕西渭南区域4对TerraSAR-X/TanDEM-X数据进行了试验分析。结果表明，对于该试验数据，采用本文提出的参数独立分解方法，干涉测量检校后干涉结果的高程精度优于2.54 m，平原地区获取DEM的绝对高程精度优于1.21 m，山地地区获取DEM的绝对高程精度优于3.11 m，验证了本文方法的有效性和正确性，为我国平原及山区1：25 000比例尺的干涉SAR地形图测绘提供了技术基础。     

TanDEM-X双站SAR干涉测量及研究进展

较全面、系统地介绍了Tan DEM-X/Terra SAR-X双站SAR科学计划,重点涉及其科学目标、Tan DEM-X卫星参数、轨道结构以及干涉数据获取模式等相关内容,并讨论了双站SAR成像、极化In SAR和数字波束成形等干涉测量新技术及其研究进展。这些双站SAR新技术的实现将大大地推动SAR干涉测量在全球地形测绘、冰川学、海洋学及地质学等领域中的应用。     

宽幅InSAR大地测量学与大尺度形变监测方法

随着人们对大尺度地形信息与地表环境变化监测需求的提升,以及哨兵1号（Sentinel-1A）、大地2号（ALOS-2）等合成孔径雷达（synthetic aperture radar,SAR）卫星的宽幅模式数据不断获取,宽幅雷达干涉测量（SAR interferometry,InSAR）技术已成为大尺度地形测绘、地球动力学（地震、火山、滑坡等）与人工地物结构健康监测等领域的研究热点。分析了两类宽幅SAR数据,即扫描（ScanningSAR,ScanSAR）模式与逐行扫描地形观测（terrain observation by progressive scans SAR,TOPSAR）模式开展干涉测量的主要限制条件与解决方法,探讨了宽幅InSAR形变监测关键误差估计与改正方法、时间序列分析技术与方位向位移观测技术,并给出2008年矩震级Mw 7.1新疆于田地震同震、震后形变监测应用。随着宽幅SAR数据的不断积累,宽幅InSAR大地测量学有望得到深入发展与应用。     

基于有理多项式模型的星载高分InSAR影像制作数字高程模型的研究

合成孔径雷达干涉测量是一种利用SAR影像复数据的相位信息提取地面三维信息的技术,它通过获取地面目标在两幅SAR影像上的相位差值来解算该点的三维坐标。有理多项式（RPC,Rational Polynomial Coefficient）模型作为一种数学意义上的几何模型,它独立于传感器和平台,简单且具有通用性,可建立地面任意坐标与影像空间的关系。本文在RPC模型用于替代星载SAR的距离多普勒模型和星载InSAR的干涉相位方程基础上,研究 RPC模型应用于星载高分辨率InSAR影像制作DEM的可行性和精度。利用兰州COSMO-SkyMed数据和资源三号三线阵数据制作的DEM为参考数据进行实验验证,RPC模型用于InSAR技术生成的DEM,中误差为7.55米。     

小波域多时相干涉SAR数据融合

大气因素和高斯白噪声对由星载干涉SAR系统获取的干涉图相位有很大的影响，可能会极大地降低结果DEM的精度，提出了一种对多时相干涉SAR数据生成的独立DEM进行权重融合的方法，该算法在小波域当中估计了大气和高斯噪声的误差功率，并对多时相DEM进行权重融合。用河北省尚义县地区的ERS-1和ERS-2数据的研究表明，此算法可以很好地提高由干涉SAR获取的DEM的精度。     

Topographic correction of ALOS-PALSAR images using InSAR-derived DEM

Topographic corrections of synthetic aperture radar (SAR) images over hilly regions are vital for retrieval of correct backscatter values associated with natural targets. The coarse resolution external digital elevation models (DEM) available for topographic corrections of high resolution SAR images often result into degradation of spatial resolution or improper estimation of backscatter values in SAR images. Also, many a times the external DEMs do not spatially co-register well with the SAR data. The present study showcases the methodology and results of topographic correction of ALOS-PALSAR image using high resolution DEM generated from the same data. High resolution DEMs of Jaipur region, India were generated using multiple pair SAR images acquired from ALOS-PALSAR using interferometric (InSAR) techniques. The DEMs were validated using differential global positioning system measured elevation values as ground control points and were compared with photogrammetric DEM (advanced spaceborne thermal emission and reflection radiometer – ASTER) and SRTM (Shuttle Radar Topography Mission) DEM. It was observed that ALOS-PALSAR images with optimum baseline parameters produced high resolution DEM with better height accuracy. Finally, the validated DEM was used for topographic correction of ALOS-PALSAR images of the same region and were found to produce better result as compared with ASTER and SRTM-DEM.     

多频率InSAR提取沼泽湿地DEM精度对比分析

选取3种波长的干涉SAR数据对提取沼泽湿地区域的DEM，并随机从1：10 000地形图中选取111个点数据进行精度验证，最后对比分析了沼泽湿地植被对于不同SAR波长的干涉相干性差异。结果表明：L-band ALOS-1 PALSAR精细模式的HH单视复数数据与1：10 000地形图数据吻合度较好，76.58%的高程值差异在3 m以内，其相干系数比C-band Sentinel-1A IW模式的VV单视复数数据和X-band TerraSAR HH单视复数数据要高；更适合利用雷达干涉测量技术提取沼泽湿地的DEM；不同湿地植被类型的相干系数有较大差异，岛状林和灌草结合的湿地植被分布区相干系数值较大，而浅水沼泽植被区和深水沼泽植被区相对较低。     

Improved topographic mapping through high-resolution SAR interferometry with atmospheric effect removal

The application of SAR interferometry (InSAR) in topographic mapping is usually limited by geometric/temporal decorrelations and atmospheric effect, particularly in repeat-pass mode. In this paper, to improve the accuracy of topographic mapping with high-resolution InSAR, a new approach to estimate and remove atmospheric effect has been developed. Under the assumptions that there was no ground deformation within a short temporal period and insignificant ionosphere interference on high-frequency radar signals, e.g. X-bands, the approach was focused on the removal of two types of atmospheric effects, namely tropospheric stratification and turbulence. Using an available digital elevation model (DEM) of moderate spatial resolution, e.g. Shuttle Radar Topography Mission (SRTM) DEM, a differential interferogram was firstly produced from the high-resolution InSAR data pair. A linear regression model between phase signal and auxiliary elevation was established to estimate the stratified atmospheric effect from the differential interferogram. Afterwards, a combination of a low-pass and an adaptive filter was employed to separate the turbulent atmospheric effect. After the removal of both types of atmospheric effects in the high-resolution interferogram, the interferometric phase information incorporating local topographic details was obtained and further processed to produce a high-resolution DEM. The feasibility and effectiveness of this approach was validated by an experiment with a tandem-mode X-band COSMO-SkyMed InSAR data pair covering a mountainous area in Northwestern China. By using a standard Chinese national DEM of scale 1:50,000 as the reference, we evaluated the vertical accuracy of InSAR DEM with and without atmospheric effects correction, which shows that after atmospheric signal correction the root-mean-squared error (RMSE) has decreased from 13.6 m to 5.7 m. Overall, from this study a significant improvement to derive topographic maps with high accuracy has been achieved by using the proposed approach.     

稀少控制的多平台星载SAR联合几何定标方法

几何定标采用地面控制点获取距离-多普勒模型中的精确几何参数,用于完成星载SAR影像高精度几何定位。但在广域范围内,特别是高山地区域,控制点极难获取。此外,传统定标方法仅面向单一平台SAR影像,尚不能实现多平台影像的联合几何定标。针对上述问题,本文提出一种基于稀少控制的多平台星载SAR联合几何定标方法。该方法从包含实测控制点的主影像出发,使用点位追踪算法获取主影像与从影像之间的连接点,并以连接点为桥梁逐级完成从影像的几何定标。本文采用京津冀地区南北向分布共计235 km的3景TerraSAR-X、3景TanDEM-X、5景高分三号影像进行联合几何定标试验,仅使用5个控制点即完成了所有影像的几何定标,并利用SF-3050星站差分GNSS接收机采集实测GPS点进行精度评价。结果表明使用稀少控制点定标后的TSX/TDX影像的几何定位精度优于3 m,GF-3影像的几何定位精度优于7.5 m,验证了该方法的有效性和正确性。     

基于高分三号卫星SAR影像的DOM制作方法研究

将星载SAR影像作为光学卫星难以获取数据地区的重要补充数据源,是基础地理信息更新的一种手段。通过对SAR影像成像机理、光谱几何特征等进行研究,总结基于高分三号卫星SAR影像处理的方法和流程,形成星载SAR影像制作DOM产品的生产技术方案,为大规模开展生产实践提供借鉴。     

Satellite radar interferometry for monitoring subsidence induced by longwall mining activity using Radarsat-2, Sentinel-1 and ALOS-2 data

This paper describes the simulation and real data analysis results from the recently launched SAR satellites, ALOS-2, Sentinel-1 and Radarsat-2 for the purpose of monitoring subsidence induced by longwall mining activity using satellite synthetic aperture radar interferometry (InSAR). Because of the enhancement of orbit control (pairs with shorter perpendicular baseline) from the new satellite SAR systems, the mine subsidence detection is now mainly constrained by the phase discontinuities due to large deformation and temporal decorrelation noise.This paper investigates the performance of the three satellite missions with different imaging modes for mapping longwall mine subsidence. The results show that the three satellites perform better than their predecessors. The simulation results show that the Sentinel-1A/B constellation is capable of mapping rapid mine subsidence, especially the Sentinel-1A/B constellation with stripmap (SM) mode. Unfortunately, the Sentinel-1A/B SM data are not available in most cases and hence real data analysis cannot be conducted in this study. Despite the Sentinel-1A/B SM data, the simulation and real data analysis suggest that ALOS-2 is best suited for mapping mine subsidence amongst the three missions. Although not investigated in this study, the X-band satellites TerraSAR-X and COSMO-SkyMed with short temporal baseline and high spatial resolution can be comparable with the performance of the Radarsat-2 and Sentinel-1 C-band data over the dry surface with sparse vegetation.The potential of the recently launched satellites (e.g. ALOS-2 and Sentinel-1A/B) for mapping longwall mine subsidence is expected to be better than the results of this study, if the data acquired from the ideal acquisition modes are available.     

机载干涉SAR测绘制图应用系统研究

介绍我国机载干涉SAR系统及测绘应用概况,介绍机载干涉SAR生成DEM、SAR正射校正、地形引起的SAR后向散射畸变校正、机载SAR图像解译、雷达图像与光学影像的融合、雷达"空中三角测量"等关键技术研究进展.最后,介绍机载干涉SAR系统在泰山试验区的测绘制图实验情况.     

Interferometric Baseline Performance Estimations for Multistatic Synthetic Aperture Radar Configurations Derived from GRACE GPS Observations

Recent studies have demonstrated the usefulness of global positioning system (GPS) receivers for relative positioning of formation-flying satellites using dual-frequency carrier-phase observations. The accurate determination of distances or baselines between satellites flying in formation can provide significant benefits to a wide area of geodetic studies. For spaceborne radar interferometry in particular, such measurements will improve the accuracy of interferometric products such as digital elevation models (DEM) or surface deformation maps. The aim of this study is to analyze the impact of relative position errors on the interferometric baseline performance of multistatic synthetic aperture radar (SAR) satellites flying in such a formation. Based on accuracy results obtained from differential GPS (DGPS) observations between the twin gravity recovery and climate experiment (GRACE) satellites, baseline uncertainties are derived for three interferometric scenarios of a dedicated SAR mission. For cross-track interferometry in a bistatic operational mode, a mean 2D baseline error (1σ) of 1.4 mm is derived, whereas baseline estimates necessary for a monostatic acquisition mode with a 50 km along-track separation reveal a 2D uncertainty of approximately 1.7 mm. Absolute orbit solutions based on reduced dynamic orbit determination techniques using GRACE GPS code and carrier-phase data allows a repeat-pass baseline estimation with an accuracy down to 4 cm (2D 1σ). To assess the accuracy with respect to quality requirements of high-resolution DEMs, topographic height errors are derived from the estimated baseline uncertainties. Taking the monostatic pursuit flight configuration as the worst case for baseline performance, the analysis reveals that the induced low-frequency modulation (height bias) fulfills the relative vertical accuracy requirement (σ<1 m linear point-to-point error) according to the digital terrain elevation data level 3 (DTED-3) specifications for most of the baseline constellations. The use of a GPS-based reduced dynamic orbit determination technique improves the baseline performance for repeat-pass interferometry. The problem of fulfilling the DTED-3 horizontal accuracy requirements is still an issue to be investigated. DGPS can be used as an operational navigation tool for high-precision baseline estimation if a geodetic-grade dual-frequency spaceborne GPS receiver is assumed to be the primary instrument onboard the SAR satellites. The possibility of using only single-frequency receivers, however, requires further research effort.Deutsche Forschungsgemeinschaft (DFG) research fellow until Sept. 2004 at the Microwaves and Radar Institute, Deutsche Zentrum für Luft- und Raumfahrt (DLR) e.V., 82234 Weßling, Germany