Anisotropic Phase Unwrapping for Synthetic Aperture Radar Interferometry

This paper presents a new phase unwrapping method for synthetic aperture radar interferometry (InSAR). Compared with other phase observations, InSAR data are unique due to the foreshortening effect in SAR images. This effect makes the interferogram phase anisotropic, i.e., the statistics of phase gradients along the ground-range axis are different from those in the azimuth direction. Furthermore, the distribution of phase gradients in the ground-range direction is not symmetric. The proposed method targets the most likely unwrapped phase by considering the foreshortening effect in SAR observation, noise characteristics in InSAR phase data, and fractional Brownian surface as a suitable model for natural topography. Experiments with simulated terrains and real InSAR data show that the method gives comparable or better digital elevation model results than the other tested methods.