Two new practical methods for phase unwrapping

In phase unwrapping, an error made at a pixel has a tendency to spread and corrupt the phase values over large areas of an interferogram. It is therefore important that a phase unwrapping algorithm be designed with a mechanism to unwrap the areas with reliable data first and to stop itself from unwrapping across a pixel at which the unwrapped phase cannot be determined with confidence. Two new practical phase unwrapping methods incorporating this requirement are reported. The first method uses the consistency between predicted phase values as a measure of confidence. The second method considers local variations of the phase value and decides if appropriate unwrapping of individual pixels will allow confident fitting of a plane over a 3-by-3 pixel region. Both of these methods have been found to he capable of unwrapping reasonably noisy SAR interferograms.