New improvements of the extended minimum cost flow phase unwrapping for processing multitemporal full resolution interferograms

We present an efficient space-time phase unwrapping (PhU) algorithm allowing us to analyze sequences of multitemporal full resolution differential Synthetic Aperture Radar (SAR) interferograms for the generation of deformation time-series. The core of the proposed technique is represented by the extended minimum cost flow (EMCF) PhU algorithm. Our method is based on a joint analysis of the spatial and temporal relationships among a set of properly selected multitemporal differential interferograms. More specifically, the key idea is to split the complex MCF network problem into that of simpler sub-networks. Accordingly, we start by identifying and solving a primary network that involves a proper selection of coherent pixels of the computed interferograms, representing the backbone structure of the overall network. Subsequently, this result is applied for constraining the solution of the sub-networks connected to the primary one, involving the entire set of analyzed pixels. This task is achieved by solving a constrained optimization problem based on the computation of a Constrained Delaunay Triangulation in the Azimuth/Range domain. The experimental results, achieved by applying the proposed approach to a dataset consisting of European Remote Sensing (ERS) SAR data acquired, from June 1992 to August 2007 over the Napoli (Italy) bay area, confirm the effectiveness of the proposed PhU approach.