Monitoring city subsidence by D-InSAR in Tianjin area

D-InSAR technique has been widely adopted to monitor land subsidence caused by withdrawal of water, oil, gas, and other minerals. Though many cities in China have seriously suffered from land subsidence caused by ground water over-extracting, few of them have enough money to do the leveling control of the subsidence. Compared with leveling and GPS surveying, D-InSAR is more cost-efficient and precise. As Tianjin city has scores of ERS-1/2 SAR data, thousands of valuable leveling data, smooth topography and severe subsidence, it is an ideal place to test and analyze D-lnSAR technique. However, D-InSAR is liable to be contaminated by atmosphere delay, temporal decorrelation and baseline errors. As these errors cannot be removed by SAR data processing, some auxiliary data such as leveling data and DEM data have been introduced into D-InSAR data processing. Therefore, This work accurately analyzes the features of atmosphere delay and temporal decorrelation with the auxiliary data in Tianjin urban area. The results demonstrate that D-InSAR can detect subsidence within three months. Further actions will be undertaken to improve the D-InSAR subsidence monitoring system, such as using Envisat data, gathering GPS zenith delay data to eliminate the atmosphere delay, and so on. The ultimate interest of our research is to establish a robust, cost efficient city subsidence monitoring system by using D-InSAR technique and other measurement.