A POLinSAR Retrieval Algorithm Applied to Rice Crops

Wide-band fully polarimetric data from rice crops, collected at the EMSL, have been used to test the performance of the random volume over ground (RVoG) inversion scheme [1]. In addition, an adaptation of this algorithm [2, 3], suited for well-defined oriented vegetation, has been also applied to retrieve the height of rice plants and the underlying topography. Due to the short height of rice plants, about 75 cm, the dihedral-type scattering from the flooded ground-stem interaction is the predominant contribution to backscattering. This produces two effects: 1) the concentration of all the coherence data measured, 2) a lack of sensitivity to the vertical structure of rice plants for small vertical wavenumber values. The first consequence enables the retrieval of the ground topography just by observing the phase of any complex coherence value. In general, these estimates are very precise from 2 to 9 GHz. On the other hand, the second consequence reduces the applicability of small baselines and/or low frequencies to retrieve the vegetation height. In the experiments at the EMSL, height estimates with +/-15 cm error can be obtained only from 7 GHz in case of using a baseline of 0.25 degrees and from 5 GHz when the baseline is doubled. The obtained results provide useful information about some parameters of the configuration which are important for the design of future air- or space-borne missions, such as the working frequencies and the baseline requirements. In addition, dual and fully polarimetric configurations have been tested. In general, estimates provided by the first two Pauli components (HH+VV and HH-VV) are very close to the ones derived from the whole set of polarizations.JRC.G.6-Sensors, radar technologies and cybersecurit