The Filtering and Phase Unwrapping of Interferogram

INSAR(Interferometric Synthetic Aperture Radar) has been studied and used widely in the field of generating high accuracy DEM(Digital Elevation Model). The processing of INSAR includes many key technologies, such as image matching, phase unwrapping, baseline estimation, etc. The phase unwrapping is difficult, but it can be made easy and simple by an excellent interferogram filtering, as is often ignored by many people. So, in this paper, the interferogram filtering and phase unwrapping are both studied. In the aspect of filtering, some filtering methods such as mean filtering, median filtering, adaptive filtering, multi-look filtering and the vector filtering are analyzed and compared. The filtering results show that the vector filtering is more excellent than others. Then, it is presented that the interferogram filtering is a critical technology for the phase unwrapping, we should filter the interferogram noises before phase unwrapping, and a new scheme for phase unwrapping is put into practice in the paper. Firstly, the interferogram is filtered by vector filtering method. Secondly, The filtered images generated from different filtering methods are unwrapped successfully by selecting a compatible gate value of coherence or of fake coherence with region grow method. Both the vector filtering for interferogram and the region grow phase unwrapping method can be applied in the successful phase unwrapping. They will promote a wider use of INSAR in generating DEMs.