A Method to Use Modis Water Vapor Products For Correction of Atmospheric-Induced Phase in Interferogram

DInSAR is a major space-geodetic technique widely used in the study of earth surface deformation. A major source of phase errors in DInSAR technique is heterogeneous phase delay caused mainly by variation of water vapors in troposphere, which is a factor limiting applications of DInSAR mainly to arid areas. This paper presents study results of three methods to correct atmospheric phase errors in DInSAR interferograms formed by TerraSAR-X images. The first method is the use of wet delay derived directly from MODIS precipitable water vapor product. The second method employs ground-based meteorological data to calibrate MODIS PWV before computing phase delays. The third method improves the second method by estimating the expected MODIS PWV value at the time of the TerraSAR-X image acquisitions which over the Bangkok test area is 5 hour earlier than that of MODIS. The time-shifted linear fit model along with the IDW interpolation is used to estimate more realistic phase delays over entire imaging area. From the study of this tropical test area, this time-corrected method provides best results while the second method also achieves a significantly better result than those obtained from direct use of MODIS PWV data.