On the use of ERS-1 SAR data over hilly terrain: necessity of radiometric corrections for thematic applications

A radiometric correction method for the quantitative use of ERS SAR data acquired over hilly terrain is illustrated over a Mediterranean forest test-site. It is based on a DEM coupled to the SAR acquisition geometry. It is shown that uncorrected σ⁰ information is mainly related to the ground scattering area (8 dB variations), and the useful thematic information (2-3 dB) is therefore masked. Once calibrated, pixel intensity decreases with local incidence angle (variations up to 1.5 dB) and this variability can be reduced using an empirical cosine model. Then, the thematic benefits of such corrections are illustrated for surface discrimination and parameter estimation, along with a discussion on applicability and limitations