Monitoring Ground Subsidence With Permanent Scatterers Interferometry

Differential Synthetic Aperture Radar interferometry (DInSAR) is a newly developed technique for monitoring large-scale ground deformation with some prominent advantages such as high accuracy and pantoscopic view. DInSAR can monitor movements on earth surface at centimeter or even millimeter levels. This is a viable and valuable space-geodetic approach. However, DInSAR technique are still some bottlenecks that need to be solved, such as time decorrelation, baseline decorrelation, atmospheric delay and so on.The newly-proposed PSInSAR (Permanent Scatterers InSAR) is regarded as the most efficient approach in overcoming both decorrelations and atmospheric delays, Using PS points, which can keep phase stable in the temporal series, surface subsidence can be gotten by analyzing the time-series differential phase variation, temporal and spatial baseline can't be considered strictly and the atmospheric effects have been decreased by differential between neighbor points. Nevertheless some problems still exist in the key processing procedures of PSInSAR such as PS detection, network construction and model estimation. Thereby, this thesis focuses on investigating basic principles of PSInSAR and critical algorithms as well as exploring new approaches so as to improve both accuracy and reliability in PSInSAR.The investigations performed in this thesis and relevant conclusions are outlined as follows:First of all,a simple experience model is given by considering a principle of best combinations of temporal baseline, spatial baseline and Doppler centroid frequency difference.The second, based upon detailed analysis about the basic principle of PSInSAR. A three-thresholding algorithm is proposed to improve the quality of PS detection .correlation-coefficient thresholding, amplitude dispersion index thresholding and amplitude index thresholding.The third, a new algorithm called solution-space search has been apply to estimate the parameters in the model of PS neighborhood differential phases. After determining solution-space size, location and search strategy according to some apriori information, the solution-space search method can be used to compute the optimal parameters rapidly.The fourth ,a tree-structure search is proposed to compute Absolute terrain error and linear deformation velocity, analysis PS residues phase, nonlinear deformations and atmospheric phase screen is separated and extravted. The time series of surface displacement was got in the end.Finally, the ground subsidence from 1992 to 2002 over area of shanghai has been successfully detected using a set of PSInSAR computer programs which is developed in the Matlab environment. It is found that the averaged displacement velocity is 9.3mm/a.The derived results are in good agreement with the precision leveling measurements obtained previously.