where C1 and C2 are the estimates of the covariance matrix acquired
pre- and post-disasters, respectively. Under the null hypothesis,
both images are identical and Q is equal to 0 (Kersten et al., 2005).
The similarity parameter was originally developed as a measure of
similarity between two scattering matrices. For a multi-look case,
the similarity parameter, R, between the covariance matrices of the
two images can be given as