The Corsar Project: Can Polarimateric Sar Interferometry Improve Forest Biomass Estimation?

RESUME The main limitation in the application of spaceborne SAR to large-scale forest biomass mapping is the variability in canopy structure and vegetation density. It causes signal saturation and a large residual error in the parameter estimates. A problem in defining retrieval algorithms for forest biomass is that microwaves respond to the shapes, sizes, orientations and dielectric properties of all the illuminated scatterers including the ground. Microwave backscatter models have revealed that the effect of variation in canopy structure on the signal can be higher than the effect of biomass. Polarimetric SAR interferometry potentially offers a means of improving SAR-based estimates of forest biomass by quantifying canopy structural variability. The polarisation information is dependent on the scattering mechanisms, and the interferometric information can be used to determine the vertical location of these scattering events in the canopy. The CORSAR project (Carbon Observation and Retrieval from SAR), which is supported by the UK Natural Environment Research Council (NERC), has the objective to examine polarimetric decomposition and polarimetric SAR interferometry methods for estimating the effects of canopy structure in biomass-backscatter relationships. We present results of the polarimetric coherence optimisation of L-band E-SAR data acquired during the SAR and Hyperspectral Airborne Campaign (SHAC 2000) analysed in relationship to expected tree height.