Radiometric correction of SAR images A new correction algorithm

Abstract

Spatial variations of the backscatter coefficient result from synthetic aperture radar imaging systems and their platforms. An adaptive algorithm has been developed to correct the multiplicative variation of the backscatter in the longitudinal (parallel to flight line) and lateral (perpendicular to flight line) directions. The coefficient of variation along the parallel and lateral profiles, which consist of the means of the pixels along these lines perpendicular to the respective profiles, is constant. This implies that the radiometric variations are multiplicative. Because standard correction methods such as polynomial transfer functions give unsatisfactory results, an adaptive correction algorithm was developed to correct these images. The algorithm produces a transfer function by means of a filtering window which moves along the profile in what is essentially a moving mean procedure. However, the length of the window is automatically adjusted as a function of the variation of the profile. The adjustment is based on a calculation of the probability that values to be included or excluded from the window belong to the included population. The effects of the successive correction steps were monitored using several thematic test sites. The resultant images provide both increased quality and quantity of data without any degradation of the statistical properties of the data.