An improved method for Persistent Scatterer （ PS） detection was presented in this paper. Based on the time series of SAR amplitude data

the PS Candidates （ PSCs） were first selected using both amplitude threshold and amplitude dispersion index threshold. The true PSs were then screened out from the PS Candidate （ PSC） set by an iterative process based on phase stability a nalysis. The deformation values of the true PSs were finally estimated. The experiments of PS detection and deformation extraction were performed using 16 high resolution SAR images collected by the X-band radar sensor onboard the German satellite T erraSAR-X covering Shanghai. The test results demonstrated that the PS points detected by the improved method were more accurate and reliable than those identified by traditional methods. The maximum subsidence rate in the investigated area reached - 51 mm / a and the average subsidence rate was - 15. 8 mm / a. The subsidence rate error derived by PSI was ± 4. 45 mm / a compared with ground-based measurements derived by precise leveling. This confirms that the PSI technique is reliable for extracting regional ground subsidence using the proposed method.