Estimation of stationary and nonstationary coherence in SAR imagery

Coherence estimation for nonstationary targets is discussed. It is shown that the averaged sample coherence obtained from complex coherence maps or coherence magnitude maps is suitable for estimation of nonstationary coherence. The averaged sample (complex) coherence permits the calculation of an unbiased coherence estimate provided that the original signals can be assumed to be locally stationary over a sufficiently coarse resolution cell. Implications for the estimation in SAR interferometry of the topographic phase corrected coherence are explored