Quicklook coherence estimation from multilook SAR imagery

This work presents applications of an unsupervised method capable of providing estimates of temporal coherence starting from a pair of multilook detected Synthetic Aperture Radar (SAR) images of the same scene. The method relies on robust measurements of the temporal correlation of speckle patterns between the two pass dates. To this end, a nonlinear transformation aimed at decorrelating the data across time while retaining the multiplicative noise model was defined as the pixel geometric mean and ratio of the two overlapped images. The temporal correlation coefficient (TCC) of speckle is analytically derived from the noise variances, measured in the transformed pair of images as regression coefficients of local standard deviation to local mean, calculated on homogeneous, i.e., non-textured, pixels. Experiments carried out on two pairs of multitemporal SAR observations, from the ERS-1/2 Tandem mission show that coherence quicklooks having comparable accuracy, even though considerably lower spatial resolution than those calculated from single-look complex (SLC) data, are easily obtained for coherence browsing.