By identifying temporarily stable natural reflectors or persistent scatterers (PS), the PSInSAR

(Persistent Scatterers for SAR Interferometry) technique can analyze the subset of pixels in SAR images, even with

long temporal and space baselines, so as to achieve high accuracy deformation measurement. The authors adopted the

PSInSAR process briefly summarized in this paper and applied this method in Tianjin area to detect the deformation

phenomena by using ENVISAT ASAR images. Calibration of ASAR images can help us select more PSCs. Using calibrated

backscattering coefficient threshold, we can discard the pixels whose amplitudes are relatively stable and whose

backscattered signals are weak and incoherent. The results obtained by processing 14 images show the distribution

and the relative deformation value of the displacement field. The estimated linear velocities of PS are not

accurate enough because of the relatively small number of images.