It is a misunderstanding that log ratio outperforms ratio in change detection of SAR images

Abstract

ABSTRACT Ratio and log ratio operators were widely used in change detection of synthetic aperture radar (SAR) images. It is well known for the researchers who focus on change detection of SAR images that log ratio outperforms ratio because logarithmic transformation can not only transform multiplicative noise into additive noise but also compress the value range of ratio. Nevertheless, this is a misunderstanding because 1) we have proven that the difference images before and after logarithmic transformation have the same receiver operating characteristic (ROC) curve; and 2) by comparing their capability in detecting different change types, we figured out the reason of the inaccurate results is that there are two intensity change types in multi-temporal SAR images and many scholars regarded them as one type (intensity increasing or decreasing). Experimental results on three original and stitched data sets confirm that: log ratio outperforms ratio is a misunderstanding in change detection of SAR images.