Modeling And Estimating Atmospheric Phase Of SAR In-Terferogram And Differential Water Vapor Decomposition

Abstract:Spatial-temporal variation of water vapor is the major limitaion for the measurement accuracy of Interferometric Synthetic Aperture Radar (InSAR). Massonnet et al.(1994), are the earliest report for atmospheric delay in SAR interferogram. To this day, lots of attempts have been done to correct atmospheric effects on InSAR. Meanwhile, exploiting atmospheric delays to retrieve the spatial variation of water vapor, can conversely provide a new data source for meteorologic studies. On this basis, the study mainly focuses on the research of atmospheric delay component on InSAR. The main contributions are concluded as follows:(1) A good study on the behaviors of atmospheric signals on InSAR for priori informations are useful for modeling atmospheric effects. In this paper, ERS Tandem interferometric pairs in typical regions are selected to make a quantitative analysis of the atmospheric effects on InSAR. Relevant conclusions are drawn that, exponential model is prior to linear model for modeling the vertically stratified component of atmospheric phase on interferogram, and Matern variogram model can discribe the Kolmogorov statistics of the turbulent component, better than traditional spherical model. The analysis can be used to found a higher precision model for the atmospheric phases in InSAR.(2) In order to mitigate atmospheric effects on SAR interferometry, we proposed a strategy for modeling and estimating the atmospheric phases in SAR Interferogram based on the analysis of its characteristics. The strategy first regresses the model parameters of the stratified atmospheric components with the method of robust estimation. Then, it uses Matern variogram model-based Kriging interpolation to estimate the turbulent atmospheric components. Finally, it corrects the atmospheric effects in InSAR measurements with the estimated stratified and turbulent atmospheric components. The results show that, after the atmospheric correction, the standard deviation of the differences between reconstructed with InSAR and reference DEM reduce significantly。(3) A new method, based on the stacking approach of small baseline subset (SBAS), is proposed to utilize a multitude of SAR interferograms on time series to retrieve the spatial variation of water vapor at each SAR acquisition, by means of modern surveying adjustment. Among that, we assume the temporal mean of spatial variation of water vapor at all SAR acquisition decays toward zero, thus resolving rank-defective in SBAS by adding a constraint. Then, we applied the method to18Envisat-ASAR images over a scene from the north China plain area as example. The result shows that, the estimated spatial distribution of water vapor at each SAR acquisition is almost consistent with MERIS. This further demostrates that the method proposed is feasible to decompose differential water vapor based on InSAR time series. There are22figures,4tables and55references in the thesis.