Speckle Filtering of SAR Images - A Comparative Study Between Complex-Wavelet-Based and Standard Filters

We present a comparative study between a complex Wavelet Coeecient Shrinkage (WCS) lter and several standard speckle lters that are widely used in the radar imaging community (Lee, Kuan, Frost, Geometric, Kalman, Gamma, etc.). The WCS lter is based on the use of Symmetric Daubechies (SD) wavelets which share the same properties as the real Daubechies wavelets but with an additional symmetry property. The ltering operation is an elliptical soft-thresholding procedure with respect to the principal axes of the 2-D complex wavelet coeecient distributions. Both qualitative and quantitative results (signal to mean square error ratio, equivalent number of looks, edgemap gure of merit) are reported. Tests have been performed using simulated speckle noise as well as real radar images. It is found that the WCS lter performs equally well as the standard lters for low-level noise and slightly outperforms them for higher-level noise.