Fast Alternatives to $H/\alpha$ for Polarimetric SAR

The polarimetric entropy ( H ) and the alpha angle (α) are two important parameters for analyzing polarimetric synthetic aperture radar data. However, for some special cases, the unstableness of the alpha angle is found; in addition, time consumption for extracting both the parameters will become quite tedious for very large images by pixelwise eigendecomposition. To overcome these shortcomings, a fast algorithm to calculate the polarimetric entropy and two new parameters are proposed in this paper. The first parameter has similar properties to the alpha angle but is stable; the second also behaves similar to the polarimetric entropy. More importantly, both new parameters can be derived very quickly. Like the unsupervised H α classification, the image can also be classified based on the two new parameters. The NASA/JPL AIRSAR L-band data of San Francisco are applied in the experiment.