Soil moisture retrieval under forest using polarimetric decomposition techniques at P-band

Soil moisture estimation was investigated in forested environments by applying long wavelength SAR at P-band together with an innovative polarimetric decomposition technique adjusted for forest vegetation scattering. Oriented volumes, exhibiting no azimuthal symmetry (T 22 ≠T 33 ), are incorporated in the scattering model for forest canopies. After extraction of the ground (surface, dihedral) components, applying an innovative surface-dihedral dominance criterion, both components are inverted for soil moisture under forested vegetation cover. Fully polarimetric SAR data of DLR's E-SAR system acquired during the OPAQUE 2007 in Saxony (Germany) and during the BioSAR 2008 campaign in Krycklan (Sweden) were used for algorithm analyses. The results for soil moisture inversion under forest indicates inversion rates between 15vol.% and 21vol.%. A first validation with in situ measurements from FDR-probes reveals a RMSE of 12.8vol.% for the OPAQUE test site.