A quantitative measure for the quality of INSAR interferograms based on phase differences

It is well-known that interferometric SAR (INSAR) is a technology for the generation of high-precision digital elevation models (DEM) and the precise measurement of terrain surface deformation. The accuracy of DEM and deformation measurement is highly dependent on the quality of the interferogram generated. Such an interferogram is constructed by a point-wise complex multiplication of corresponding pixels in both datasets, which are respectively contained in master image and registered image. An exanimation of existing literature reveals that there is no, good, quantitative measure for the quality of interferograms, and visual inspection is still the best solutions available so far. By visual inspection, one recognizes those interferograms with continuous fringes as good ones and regards those with many discontinuous interferograms and speckles as being not good. As the pixels in the interferogram represent the phase value values, it is natural to think that, if the quality is good, the phase differences between neighbor pixels should be small, and thus the sum of all phase differences will still be small. This leads to the proposal of "sum of phase differences" (SPD) as a quantitative measure for the quality of interferogram. Two simulation tests have been conducted, and the results show that the SPD is a reliable measure.