Phase unwrapping through a branch-cut-based cut-bridging and window-patching method.

The processing required for interferometric synthetic aperture radar (SAR) applications includes a technique for unwrapping the phase in a two-dimensional region. The phase-unwrapping technique is often based on Goldstein's branch-cut approach. However, this conventional approach leaves holes that are isolated by branch cuts when interferograms have high noise levels. We improve the conventional approach with two new features: (1) we slightly loosen the phase-gradient constraint at the boundary of the already unwrapped area and force growth of the unwrapped area into holes through bridging cuts wherever appropriate; and (2) we recursively fill progressively smaller closed areas by adding rectangular patches while maintaining maximum phase consistency in the overlapped unwrapped areas. The approach is verified with actual SAR data.