ERS differential SAR interferometry for urban subsidence monitoring of Suzhou, Eastern China

Since the 1980s excessive ground water exploitation in a lot of cities has resulted in significant land subsidence that has damaged buildings, roads, and pipelines. It has also changed the areas affected by flooding. And in recent years the subsidence of the megalopolis has been increasingly serious. Differential SAR interferometry (D-InSAR) with ERS-1/2 SAR data has a high potential for surface displacement mapping in the mm to m range. In this paper the potential of ERS-1/2 SAR interferometry for mapping of subtle land subsidence has been investigated. Our measurements were taken in Suzhou city, Jiangsu province, China. We collected a time series of ERS-1/2 SAR data from February 1993 to February 2000, Eight ERS-1/2 SAR images were used to create seven interferograms, three differential interferograms were produced using three-pass method, which clearly showed the spatial extent of subsidence. The D-InSAR deformation maps were validated by leveling surveys. The correlation between D-INSAR observations and leveling observations was 0.943 and standard error was 0.1706. Based on seven benchmarks, the subsidence rates were estimated the overall trend were in close agreement with D-InSAR results. We concluded that for the mapping of land subsidence in urban environments D-InSAR had a strong potential with regard to cost effectiveness, resolution and accuracy. In many other cities affected by subsidence, D-InSAR should be operationally applied.