Statistical evaluation and bias removal of multi-look effect on Entropy/ alpha/Anisotropy in polarimetric target decomposition

Entropy, alpha and anisotropy (H/alpha/A) of the polarimetric target decomposition has been an effective and popular tool for polarimetric SAR image analysis and for geophysical parameter estimation. However, multi-look processing can severely affects the values of these parameters. In this paper, Monte Carlo simulation is used to evaluate the multi-look effect on these parameters for various media of grass, forest and urban. Due to insufficient averaging, entropy is underestimated and anisotropy is overestimated. We also found that the bias in Alpha angle can be either under or overestimated depending on scattering mechanisms. Based on simulation results, efficient bias removal procedures have been developed. In particular, the entropy bias can be precisely corrected independent of radar frequency and SAR systems. Data from L-band DLR/E-SAR and L-band JPL/AIRSAR, and X-band PI-SAR data are used for demonstration.