Terrain-flattened gamma nought Radarsat-2 backscatter

Radarsat-2 offers a variety of new modes and capabilities. We present results from rigorous application of geometric and radiometric calibration to backscatter values, enabling comparisons between different modes. First, the system's a priori geometric accuracy was tested (tiepoint free) by comparing the measured positions of corner reflectors in ultrafine images with predicted locations calculated based on the satellite state vectors and radar timing annotations. Second, the geometric accuracy of the dual-pol ScanSAR SCNB mode was tested by correlating each backscatter image to a radar image simulation calculated using the same product annotations. Third, the radar image simulation was used to normalize the backscatter values in both polarisations, generating terrain-flattened gamma nought values that were then terrain geocoded. Fourth, the available ascending and descending SCNB image pair was overlaid with and without such radiometric terrain correction applied. The advantages gained by using terrain-flattened gamma nought are discussed.