A New 3-D Minimum Cost Flow Phase Unwrapping Algorithm Based on Closure Phase

Abstract

Phase unwrapping (PU) is a critical step in interferometric synthetic aperture radar (InSAR) processing chain, which can directly affect the quality of the final results. In order to improve the accuracy and robustness of PU algorithm, especially for the interferograms that have relatively long perpendicular baselines, in this article, we propose a new 3-D minimum cost flow (MCF) algorithm based on closure phase. Different from current 3-D PU algorithms that aim to solve the unwrapped phase gradients (UPGs) among different interferograms and usually follow a 1+2D mode, this new approach establishes a mathematical constraint within the closure phases and unwraps them jointly. This constraint is based on a prior knowledge that the sums of UPGs, where the UPGs are in the azimuth/range plane whereas belongs to different interferograms in the closure phase, can be obtained before PU. The main advantage of this new approach is that neither a temporal deformation model nor a preliminary atmospheric phase calibration is required before PU. Besides, this new approach combines the MCF model and phase consistency, showing advantages in reducing the chance of phase aliasing. We implement our new approach in both continuous and discrete interferograms and use real SAR data to validate the performance by comparing with the 2-D MCF algorithm in SNAPHU and the 3-D PU algorithm in StaMPS.