AN IMPROVED SAR OFFSET TRACKING METHOD TO MEASURE LARGE SURFACE DEFORMATIONS

摘要

For analyzing the mechanism of surface deformation, Synthetic Aperture Radar (SAR) techniques have been widely used because it has the capabilities of all-weather observation and high spatial resolution. Among the techniques, SAR offset tracking method would be a feasible solution in the case of abrupt and large deformation observation because it is not necessary to phase unwrapping procedure. It can provide unambiguous ground displacements in both the range and azimuth directions. To define relative movements of features, the method uses an intensity cross-correlation method between pairs of SAR images. The measurement performance of the method depends on the existence of identical features in the pairs of images at the scale of the feature window. For the reason, this paper proposes an efficient SAR offset tracking method considering multiple feature window sizes. The method exploits an iterative SAR offset tracking with multiple feature window sizes and then the final range and azimuth displacement maps were generated by averaging the each offset measurements after removing the outliers. The performance of this method was tested using European Remote Sensing 2 (ERS-2) SAR data sets that observed the co-seismic displacements of the 1999 Hector Mine earthquake event in California. The RMSE (root-mean-square errors) between the final range and azimuth displacements maps and GPS measurements are about 5.92 cm and 6.95 cm, respectively. Especially, the proposed method can improve the trade-off relationship between measurement accuracy and resolution according to the feature window sizes, because the proposed method considers multiple deformation information using multiple feature window sizes.