Multibaseline gradient ambiguity resolution to support Minimum Cost Flow Phase Unwrapping

The TanDEM-X Mission has as primary objective to generate a high resolution global Digital Elevation Model. This paper proposes a new method for multibaseline Phase Unwrapping which is the critical point of this generation. We propose to combine both Minimum Cost Flow (MCF) and Maximum a Posteriori (MAP) estimation. The latter is used to solve phase gradient ambiguities. The problem is posed as an energy minimization one and solved using Belief Propagation (BP) which is an iterative process. Nevertheless, although very good results are obtained on loopy graphs, it is not guaranteed to converge. Thus, phase unwrapping of the most accurate interferogram is finally performed with the MCF algorithm and takes as input the unwrapped gradients.