A phase unwrapping method using direct residue removing

There have been proposed many phase unwrapping methods, which are roughly divided into two types; (quality guided) path following and least squares. Both types of method, however, do not have enough performance; the former can not unwrap areas having lower quality than residues do, and the latter needs iterative calculation which takes much time. The authors propose a new method that improves the performance both in accuracy and in efficiency. The basic idea of the method is to divide the interferogram into irrotational (residue free) and rotational components. Both components are merged after unwrapping them. A direct residue removing technique is used for getting the irrotational component, and the rotational one is obtained by subtracting the irrotational component from the original interferogram. As it is impossible to unwrap the rotational component, they propose a new algorithm for merging the both components without applying actual unwrapping operation. In this algorithm, positive and negative residues are paired and added to irrotational component sequentially. Virtual residues are used for balancing the numbers of them. As the combination of residues controls the quality of the unwrapped phase, the optimized pairing gives us the minimum L⁰ measure. The performance of the proposed method was confirmed by processing an actual ERS-1 SAR interferogram