PS InSAR processing methodologies in the detection of ground surface deformation: a case study of Nantong City

Abstract

Over the last two decades, Synthetic Aperture Radar Interferometric (InSAR) has proven a remarkable potential tool for observing the Earth surface, especially for mapping the Earth's topography and deformation. It can resolve surface displacement with centimetric accuracy, tens meters of spatial resolution and monthly temporal resolution. The permanent scatterer (PS) technique has been developed later in the 1990s first by A. Ferretti to overcome the major limitations of repeat-pass SAR interferometry: temporal and geometrical decorrelation as well as atmospheric delays. The Ferretti's method, referenced as the Permanent Scatterers TechniqueTM in their patented procedure, works best in urban areas containing large numbers of man-made structures, which tend to be angular and often produce very efficient reflectors that dominate background scattering. In this paper, a series of fifteen ENVISAT ASAR acquisitions of the city of Nantong, located at the mouth of Yangtze River adjacent to Shanghai, covering the period from 2006 to 2007, was analyzed. The PS-InSAR technique and Geographic Information System (GIS) spatial analysis were used to detect ground deformation in the urban area. Results show there was no large, continuous subsidence occurs in the city, however seven subsidence bowls were found. This can be used to define the risk zones for future ground subsidence.