DETECTION OF LAND SUBSIDENCE IN BEIJING, CHINA, USING INTERFEROMETRIC POINT TARGET ANALYSIS TECHNIQUE

Land subsidence in Beijing is supposed to be caused by over-exploitation of ground water, which is leading to a rapid decline of water levels, drying out clay layers that finally result in land subsidence. The Interferometric Point Target Analysis (IPTA) is an advanced method to monitor vertical motion of the land surface over time. IPTA identifies backscattering objects, named as coherent points or points targets, at the ground surface that persistently reflect radar radiation emitted by the SAR antenna. The core component of the IPTA technique is the iterative estimation of phase differences for all measurement points over the sets of the SAR data using a linear model. In this paper, IPTA technique was used to retrieve the phase history, extract the linear deformation information from interferometry phase and weaken atmosphere phase delay in Beijing. 20 ENVISAT ASAR images acquired between June-18-2003 and March-14-2007 have been selected. The intention of this article is to demonstrate how IPTA technique could be used to extract valuable information in Beijing area.