InSAR coherence estimation

For interferometric SAR processing (InSAR), the quality of the interferogram is affected by many factors such as Doppler centroid difference, baseline, atmospheric effect. It can be measured by the estimation of the coherence of the data. It has been shown that the coherence image can be used to do the classification in the area such as water, soil, plants, city or something else. But the coherence estimation is always biased somehow. To find an asymptotically unbiased coherence estimation method is therefore challenging and important for InSAR processing. In this paper, several different coherence estimators are introduced. An accurate coherence computation method using an existing DEM is proposed and illustrated