The conformity coefficient or how to explore the scattering behaviour from compact polarimetry mode

In a previous paper, we have investigated the potential of the compact polarimetry mode at longer wavelengths in a space environment for soil moisture estimation. At longer wavelengths, one of the main challenges in dealing with compact polarimetry is the Faraday rotation estimation and correction. One proposed technique relies on bare surface scattering properties. Identifying the bare surfaces can be done using the conformity coefficient. This new coefficient can also be used to discriminate between surface, volume and double bounce scattering. It provides similar results to the Freeman-Durden classification in discriminating bare surfaces. In this paper, the study is pursued to include theoretical approach to the comparison. The potential of the conformity coefficient is benchmarked further against the well-known entropy-alpha-anisotropy classification. The comparison between these techniques is first performed theoretically and the effect of noise is investigated. These techniques are then applied to existing datasets coming from various sources, airborne sensors as RAMSES and AIRSAR and spaceborne sensors as PALSAR data and the results are cross-evaluated. The Faraday rotation can be estimated from full polarimetric data as was proposed by both Freeman and Bickel & Bates. These approaches are not applicable to compact polarimetry data. In a previous paper, it was shown how bare surface behavior can be used to perform this estimation. In this paper, the performance of this estimation is evaluated on PALSAR data and on airborne data where a constant ionosphere is simulated. The results are contrasted with estimates derived from full polarimetric data.