Unbiased estimation of the coherence from multi-look SAR data

The statistics of the classical coherence estimator are derived for Gaussian scenes. It is shown that the coherence estimator is generally biased towards higher values for partially coherent areas. The multi-look coherence estimator is then analyzed, and the statistics of the classical coherence estimator are used to remove the bias from the coherence estimate. A new method for coherence estimation from the multi-look complex coherence, is introduced. It is shown that the multi-look complex coherence estimate is less biased than the multi-look magnitude coherence. The statistics of the complex coherence estimator are derived and used to remove the coherence bias