Atmospheric correction in time-series SAR interferometry for land surface deformation mapping – A case study of Taiyuan, China
Published in August 01, 2016
The dominant error source of Synthetic Aperture Radar Interferometry (InSAR) is atmospheric phase screen (APS), resulting in phase delay of the radar signal propagating through the atmosphere. The APS in the atmosphere can be decomposed into stratified and turbulent components. In this paper, we introduced a method to compensate for stratified component in a radar interferogram using ERA-Interim reanalysis products obtained from European Centre for Medium-Range Weather Forecasts (ECMWF). Our comparative results with radiosonde data demonstrated that atmospheric condition from ERA-Interim could produce reasonable patterns of vertical profiles of atmospheric states. The stratified atmosphere shows seasonal changes which are correlated with time. It cannot be properly estimated by temporal high-pass filtering which assumes that atmospheric effects are random in time in conventional persistent scatterer InSAR (PSI). Thus, the estimated deformation velocity fields are biased. Therefore, we propose the atmosphere-corrected PSI method that the stratified delay are corrected on each interferogram by using ERA-Interim. The atmospheric residuals after correction of stratified delay were interpreted as random variations in space and time which are mitigated by using spatial–temporal filtering. We applied the proposed method to ENVISAT ASAR images covering Taiyuan basin, China, to study the ground deformation associated with groundwater withdrawal. Experimental results show that the proposed method significantly mitigate the topography-correlated APS and the estimated ground displacements agree more closely with GPS measurements than the conventional PSI.
合成孔径雷达干涉测量（InSAR）的主要误差来源是大气相位屏幕（APS），它会导致雷达信号在大气中传播时产生相位延迟。大气中的APS可以分解为分层成分和湍流成分。本文介绍了一种利用欧洲中期天气预报中心（ECMWF）提供的ERA-Interim再分析产品来补偿雷达干涉图中分层成分的方法。与气象探测数据的比较结果表明，ERA-Interim的大气条件能够产生合理的垂直大气状态剖面模式。分层大气呈现季节性变化，且与时间相关。在传统的持久散射体InSAR（PSI）方法中，时空高通滤波假设大气效应是时间上随机的，无法正确估算，因此，所估计的变形速率场会产生偏差。因此，我们提出了大气校正的PSI方法，通过使用ERA-Interim对每个干涉图中的分层延迟进行修正。修正分层延迟后的大气残差被解释为时空中的随机变化，通过时空滤波来缓解。我们将该方法应用于覆盖中国太原盆地的ENVISAT ASAR影像，研究与地下水开采相关的地面变形。实验结果表明，所提出的方法显著减轻了与地形相关的大气相位屏幕（APS），并且估计的地面位移比传统的PSI方法与GPS测量结果更加吻合。