A region-growing algorithm for InSAR phase unwrapping

This paper describes a new region-growing algorithm for interferometric syn thetic aperture radar (SAR) phase unwrapping. The algorithm is designed to handle noisy interferograms and based on the following principles. 1) Unwrapping is carried out on the perimeter of "growth regions," and thes e regions are allowed to grow with consistency checking. 2) Phase information from neighboring pixels is used to predict the correct phase of each new pixel to be un wrapped. 3) Reliability check is applied to each unwrapping attempt, and the thresho ld used in the cheek is gradually relaxed so that the most robust unwrappin g path is followed, 4) As regions grow into one another, they are merged by adjusting their amb iguity numbers, and further reliability cheeks must be passed for merging t o be allowed. To verify the proposed algorithm, the region-growing phase unwrapping algor ithm has been compared with two of the most widely used algorithms: the cut -line (CL) (also known as residue-linking) algorithm and the weighted least -squares (WLS) algorithm. The FRINGE Sardegna interferogram has been used b ecause it has steep topography that causes problems for many phase unwrappi ng algorithms, It has been shown that the region-growing algorithm can unwr ap well into low coherence regions, while making few ambiguity-level errors . This can be attributed to the diversity of growth paths used by the algor ithm, in which difficult areas are approached from many directions.