D-InSAR Technique for Land Subsidence Monitoring

The land subsidence has been a global disastrous problem, and the conventional geodetic technique is highly incompetent in the large-scale and serious land deformation monitoring. The D-InSAR technique has been widely applied and deeply researched in the field of the land deformation monitoring. This article first puts forward one of the methods known as time series radar interferometry based on permanent scatterers technique, and then, applies the time series analysis method into D-InSAR. This paper takes the phase difference of two nearer permanent scatterers in an interferogram as research object; therefore, the atmospheric delay impact can be eliminated. In the research, there are several steps including preprocessing radar images, selecting the PS points, combination of PS points, computing the variance of the phase difference for two PS points, integer least-squares adjustment, obtaining land subsidence velocity and so forth. The land subsidence data and the distribution map obtained in this paper by adapting this method to the experiment of Tianjin area subsidence monitoring have been proved to be satisfactory. The method for eliminating the atmospheric delay impact accurately has been realized by combining the time seriesmethod with PS technique. At the same time, it was confirmed that the time series for InSAR is a feasible and effective method for monitoring land deformation. Moreover, it can be concluded from the result obtained in the paper that the selection of PS points is so important that it is worthy studying further on.