The Specificity of P Band Polinsar Data over Vegetation

RESUME A polarimetric and PolInSAR analysis has been conducted on the Nezer forest (Southern France) at L and P band on high resolution SAR data acquired with the ONERA RAMSES system in January 2004. The dataset was investigated for its potential for retrieval of forest parameters from SAR data using three different techniques: • Radiometric inversion from the cross-polarized term, • PolInSAR inversion based on the random-volume over ground model • An approach based on the anisotropy parameter. This paper concentrates on polarimetric and PolInSAR inversion. The observed linear regression between anisotropy and vegetation height is inverted and provides a RMS error of the order of 2m. This technique displays no saturation at P band. The PolInSAR data behaviour over the forest is consistent with the RVoG model. The standard inversion described in the literature is modified to account for the higher expected penetration at P band, by selecting a given extinction coefficient or a range of extinction coefficients. The inversion results are precise to within 1.2m. When the baseline is properly selected, the extinction coefficient is a weak parameter. The concept of Compact Polarimetry (CP) as proposed by JC Souyris [9] is explored in the context of PolInSAR inversion and the accuracy of the Compact PolInSAR inversion is shown to be very similar to the one obtained with the full polarimetry. A preliminary assessment of the ionospheric effect on such an inversion shows low sensitivity of the inversion to Faraday effects when the one-way rotation is less than 15°. The mode where the transmit wave is circularly polarised is extremely promising..