Quantification of the topographic slope from radar satellite imagery

A specificity of Synthetic Aperture Radar (SAR) scenes is to display geometric distortions depending on both the system of acquisition ant its relation with the topography. Establishing the geometric relationship between the radar sensor parameters and the related surface deformation should therefore provide quantitative information on the topographic surface. Here, we propose a new technique for the computation of the terrain slope, which is based on the quantification of the geometric deformation generated during the acquisition of a SAR scene. The method uses a pair of radar scenes consisting of an orthorectified image and another in slant-range geometry to compute the local topographic slope of a reference ground segment identified on both images. Computed slope values using ENVISAT-ASAR and TerraSAR-X images and compared with measurements taken in the field in the Djebel En Negueb anticline located in south-central Tunisia reach 3° with both data.