Review of Polarimetric Indicators for Forest Characterisation over Several Sites

Global warning is now known to be the major environmental issue mankind will have to face in the next decade. Monitoring of vegetation and biomass is clearly an essential piece of information required at all levels ranging from the scientific studies to understand and forecast, to the political world responsible for drafting remediation policies and evaluating their impact. Microwave remote sensing with the low-frequency SAR technique can provide a useful characterization of forest (spatial coverage, species, density, height...) at a global scale, relying on the all-weather imaging capabilities of SAR linked with the significant penetration of the low-frequency EM wave in the canopy. In this paper, we will review the potential polarimetric indicators and evaluate their performance over several types of forest. We will particularly focus on the impact of the topography and the influence of the weather conditions.