The Application Of InSAR To Monitor Land Subsidence In Cangzhou Region

With the development of the city, The damage of the land subsidence becamemore and more severe. Although the routine measures have the higher accuracy, theircosts are very high, their sample density is very low and their measure cycle is verylong, all of them couldn't satisfy the demand of the recent society. InterferometricSynthetic Aperture Radar(InSAR) had become the most potential technique. It couldsample densely, measure the land subsidence in the short cycle, and its cost is cheaper.Grounddwater withdrawal was started in 1965 in Cangzhou city. Thenground-subsidence occurred in the early of 70's. There is close relation- ship betweenthe discharge of groundwater withdrawal and the value of ground-subsidence. In thesubsiding center of Cangzhou City, the land surface had sunk for 30 years by 2001and the subsidence amount reached more than 2 m, which caused waterlogging ofsome segments in the city. And the subsidence in the river bed will seriously influencethe security of the Water Transfering Project From South to North China.Satellite Interferometric Synthetic Aperture Radar (InSAR) is a revolutionarytechnique that allows scientists to measure and map changes on the Earth's surface assmall as a few millimeters. By bouncing radar signals off the ground surface from thesame point in space but at different times, the radar satellite can measure the changein distance between the satellite and ground (range change) as the land surface upliftsor subsides. Maps of relative ground-surface change (interfe- ograms) are constructedfrom the InSAR data to help scientists understand how ground-water pumping,hydrocarbon production, or other human activities cause the land surface to uplift orsubside.This paper collected 10 scenes ERS-1/2 SAR SLC image(July 1992 to October 1997)about Cangzhou region. The area of these images is l00km×100km, entirely coveringall the region. After analyzing these images, the author got some experiences: Thesituation of vegetation in the region was a very important factor for the application ofInSAR, because it directionly changed the time and range of the application of InSAR;In order to obtain the DEM, we should choose the middling baseline;In addition, weshould consider the stability and accuracy of the satellite.Satellite Interferometric Synthetic Aperture Radar (InSAR) had shown us itsunique advantage and high degree of accuracy, and would be the direction of thefuture monitoring technology of land subsidence.