Ground subsidence monitoring of Shanghai Inner Viaduct by TerraSAR images

Shanghai is the central city of the Yangtze River Delta Urban Agglomeration and the second largest municipality in China. Shanghai has formed a three-dimensional transportation network consisting of ground roads, elevated roads, river crossing tunnels and bridges, as well as metros and elevated rail transit. As soft soil basement, monitoring ground subsidence of the Shanghai Inner Viaduct is very important for its safety and maintaining work. Multitemporal interferometric synthetic aperture radar (MT-InSAR) is a technology that uses high spatial resolution satellite images to detect high-precision surface variations. In this paper, we use 37 scenes of TerraSAR-X ascending images with a high resolution of 3 meters acquired from March 2009 to October 2012 to detect and process high coherence points along Shanghai Inner Viaduct. Then, we use the unsupervised classification method of K-means for the separation of elevated points and ground points. A total of 14,869 points are obtained along the viaduct, and 7,668 of them are on the viaduct. The average deformation rate of elevated points and ground points are 0.38 mm/year and -1.15 mm/year respectively. The result shows that high resolution SAR images can be used to monitor the deformation of the Shanghai inner viaduct efficiently and the settlement of the viaduct is more stable than its nearby ground.