Congruence in least-squares phase unwrapping

Least-squares phase unwrapping algorithms of SAR interferometry minimize the squares of the differences between the gradients of the wrapped input phase and those of the unwrapped solution. These algorithms seem to lack the accuracy of some path-following algorithms, however, even when weighted least-squares techniques are used to mask out corrupted phase values. The reason for this is that least-squares solutions are not congruent to the wrapped input phase. The author introduces a congruence operation that forces any solution to be congruent to the wrapped input phase. This operation dramatically reduces the errors and renders least-squares solutions as accurate as those from path-following algorithms