Anisotropic diffusion in synthetic aperture radars

Speckle effects are commonly observed in synthetic aperture radar (SAR) image, which applies in many land applications, such as agriculture or forestry. However, although the human eye is able to derive the meaningful information from the SAR image, automatic processing is very difficult because of the noise effect present in the image. In this paper, anisotropic diffusion is modified in logarithmic domain to remove the speckle noise in ERS and JERS satellite data. The modified diffusion method is employed as a tensor, varying with both the location of a pixel in the image and the orientation of the local image geometry vicinity the pixel. In our algorithm, SAR images are transformed into logarithmic domain and using the modified anisotropic diffusion to smooth out the noise; consequently, the smoothed image is converted by an exponential function. Simulation results on the satellite images are provided to indicate the effectiveness of the proposed method when used to remove the effects of speckle noise almost as well as that of the additive noise. The evaluation of the proposed method employs the theoretical gain in equivalent numbers of looks (ENL)