Space-borne and ariborne SAR (Synthetic Aperture Radar) systems and SAR application technology have recently advanced greatly and interferometric SAR (InSAR) techniques can now be more effectively applied and used in many geological and engineering problems. There are several SAR data acquisition geometries for interferometric applications and PS (Permanent Scatter) InSAR (SAR interferometry) technique can accurately measure very small deformations on the Earth's surface with greatly increased precision. In this paper, the PSInSAR technique is tested and utilized to monitor and measure the land surface subsidence of areas near Incheon Port, and selected locations in Busan, Korea. All available JERS-1 (Japanese Earth Resource Satellite-1) L-band SAR data were acquired, processed and used to estimate the ground subsidence and subsidence rates, which range up to 30 mm/year.