The Study And Analysis Of PSInSAR In Land Subsidence Monitoring

China is a country prone to geological disasters, Land subsidence, landslide and other geological disasters with characteristics of surface deformation, has caused serious harm to the country and the people. According to incomplete statistics, there are currently about 96 cities and regions, which have different degrees of subsidence. And the land subsidence in Tianjin is very representative.Synthetic aperture radar differential interferometry- DInSAR, with advantages of wide-coverage, high-resolution, all-weather, all-time, etc, is a promising monitoring technique of surface deformation. However, in practical application, time and space decorrelation, noise and errors, atmospheric phase and atmospheric delay, etc, have reduced its accuracy for deformation information acquisition, even make it unenforceable in some cases.PSInSAR (permanent scatter InSAR) is possible to avoid many of the limitations of conventional DInSAR by only analyzing pixels, which behave like point scatters and retain some degree of correlation. However, in almost all of its previous algorithms, an initial set of PS pixels is selected using amplitude variation, which doesn't work very well in non-urban areas, and the approximate temporal model for deformation required to refine PS, estimate and remove nuisance terms, which is complicated and also the aim of study, is usually assumed to be constant in rate, or periodic in nature.This study doesn't continue to explore non-linear or more complex motion model, but introduced a new PSInSAR, which uses spatial correlation of interferogram phase to find a network of stable pixels in almost all terrain without prior knowledge of temporal variations in the deformation. As the new method is not restricted by deformation model, we can get the deformation information for each data-acquisition time, which improves the time resolution and has a significant guide to the analysis of the deformation laws and causes.Phase-unwrapping is a key point in the workflows of InSAR, DInSAR and PSInSAR, which involves2-D and 3-D phase unwrapping for space regular and non- regular grid distribution data. Some related algorithms are summarized, compared and practiced in this study.We have collected 14 ENVISAT ASAR SLCs covering from Oct 2003 to Dec 2005 for Tianjin area, and by using the new PSInSAR technique, which is based on phase spatial correlation analyzing, PS selection, noise estimation, phase unwrapping and deformation information extraction are applied to these ASAR images. A L0-norm pseudo-3D algorithm is implemented for phase unwrapping. As the PS are discrete and irregularly distributed, Kriging interpolation and deformation contours are applied to get continuous deformation senses. Monitoring results in 3D views, side views and profile maps are also generated. Some subsidence centers are analyzed by deformation time series. At last, combined with the mining of ground water and economic station of this area, the cause of deformation is analyzed, and suggestions on subsidence control are proposed.