Using Permanent Scatterer Insar to Monitor Land Subsidence along High Speed Railway- the First Experiment in China

We present in this contribution the results of the first experiment to monitor land subsidence along JingJin High Speed Railway (JingJin HSR), which connects Beijing city and Tianjin city and is the first high speed railway in China, by using the Permanent Scatterer InSAR (PSI). Since the length of the railway is usually beyond the standard scenes coverage of the ongoing radar satellite, i.e. ENVISAT and RADARSAT SAR images which has a ground coverage of 100×100 km, we have developed techniques in this work for land subsidence monitoring of very extended areas with multi-track long strip SAR images. In particular, we have studied the method for integrating multi-track PSI for large coverage subsidence mapping. We applied the ENVISAT ASAR data acquired from Jan, 2007 to Dec, 2008 in neighboring tracks (Track-218 and track-447, Frame 2799 to 2817) to perform the PSI analysis. The PSI estimated subsidence velocity map in adjacent track have been integrated to generate the large coverage subsidence velocity map; these result are relevant to an area in the North China Plain that extends for about 200×150 km. For detailed investigation of JingJin HSR, a buffer zone with a width of 3 km in each side of the railway have been generated and the subsidence values have been extracted from the merged velocity map. The results clearly indicate the distribution and magnitude of the subsidence zone along Jing-Jin high speed railway and they demonstrate the approach to analyze the subsidence of very extended areas.