Multiresolution phase unwrapping for SAR interferometry

An approach to two-dimensional (2-D) phase unwrapping for synthetic apertur e radar (SAR) interferometry is presented, based on separate steps of coars e phase and fine phase estimation. A technique called adaptive multiresolut ion is introduced for local fringe frequency estimation, in which differenc e frequencies between resolution levels are estimated and summed such that a sufficiently conservative phase gradient field is maintained, A coarse un wrapped phase of the full terrain height is then constructed using weighted least-squares based on coherence weighting. This coarse phase is used in a novel approach to slope-adaptive spectral shift filtering and to reduce th e phase variation of the interferogram. The resulting interferogram can be more accurately multilooked and unwrapped with any algorithm, In this paper , fine phase construction is done with weighted least-squares and with weig hts determined by simple morphological operations on residues. The approach is verified on a simulated complex interferogram and real SAR data.