Interferogram phase noise reduction using morphological and modified median filters

Phase unwrapping for SAR interferometry is one of the barriers for obtaining an operational interferometric SAR system (InSAR). For filtering the phase one uses mainly a low pass linear filter applied on the complex interferometric image before evaluating the phase. This paper compares three different non linear methods which filter the wrapped phase map. The first method is based on a morphological filter, the second one is a modified median filter and the third is a modified mode filter. All filters are built considering the periodic character of the wrapped phase function. The characteristics of these filtering approaches are compared, and the number of residues are calculated after each filtering step.