Experimental PALSAR Interferometry in Shanghai for ground subsidence monitoring

Jicang Wu(1), Caijun Xu(2), Yangmao Wen(2) and Feng Xiao(1)

(1) Tongji University, Siping Road 1239, Rm B612, 200092, China
(2) Wuhan University, School of Geodesy and Geomatics, 430079, China


Up to February of 2008, we have downloaded 21 PALSAR SLC images from AUIG online data service, including 14 images of FBS and 7 images of FBD. Twenty two pairs of InSAR interferomgrams have been formulated among these SAR images. We have applied the following strategies in InSAR data processing: 1, As FBS and FBD have different spatial resolution, the FBD image will be taken oversampling with a factor of 2 in the range so as to keep the same resolution with FBS image; 2, Two pass interferometry has been used and the SRTM DEM has been applied as external topographic corrections; 3, Since Shanghai is located at the mouth plain of Yangtz river, the ground is very flat and it is difficult to coregister with the external EDM, the Landsat image is applied for helping the coregistration with EDM; 4, As the perpendicular baselines are quite long for these interferometric pairs, there are significant orbital residual fringes in the interferograms. The method of analysis of characters of fringes has been used to eliminate these orbital residuals successfully. After analysis of the twenty two interferograms, we find that the weather (heavy rains), DEM error and also data processing methods limited the capability of PALSAR to monitor the ground subsidence in Shanghai in a short time period. For monitoring the ground subsidence in Shanghai with millimeter accuracy, short baseline, lager amount of SAR data and advanced data processing method, such as PS-InSAR should be employed.



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