Song, XG, Li, DR, Shan, XJ, Liao, MS, Cheng, L (2009). Correction of atmospheric effect in ASAR interferogram using GPS and MODIS data. CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION, 52(6), 1457-1464.
It is usually believed that the sparse spatial resolution of GPS stations is a main limitation factor for improving correction accuracy when we only use GPS-ZWD data to mitigate atmospheric effect in repeat-pass InSAR measurement. In this paper, a method is investigated to generate water vapor delay map using a few GPS stations and MODIS near-infrared water vapor products, which is used to correct atmospheric effect in interferogram. Firstly, a patch-wise calibration method which partitions the MODIS product as several patches based on the location of GPS stations is adopted to correct the scale error in MODIS water vapor data of every patch with corresponding GPS-ZWD, then the calibrated MODIS data is analyzed using spatial structure function, and spatial distribution law of water vapor in the area of interest is achieved. Finally, this kind of spatial distribution information of water vapor is incorporated into the Kriging interpolator to generate much reasonable water vapor map. The experimental results from two interferograms of Shanghai ASAR data show that the atmospheric water vapor difference map from the GPS+MODIS method can remove not only part of long-wavelength atmospheric components significantly but also some short-wavelength signal, especially ones with strong amplitude. After applying GPS+MODIS method, the global root mean square (rms) atmospheric phase fluctuations of the interferograms dominated respectively by short- and long-wavelength signals decrease significantly by 32.74% and 38.82% respectively. Comparing with GPS+ATM algorithm, we found, the GPS+MODIS method is better than GPS+ATM algorithm to remove atmospheric effect, and it hold stronger ability to reproduce atmospheric signal, especially short- wavelength signal, than GPS+ATM algorithm under existing data condition of Shanghai research area (only six GPS station).