TUTORIAL ON SAR POLARIMETRY

3. SINGLE VS MULTI-POLARIZATION DESCRIPTORS 3.1 Polarisation and Surface Scattering The main problem for the quantitative estimation of soil moisture and/or surface roughness from SAR data lies in the separation of their individual effects on the backscattered signal. Polarimetry plays here an important role as it allows either a direct separation or a parameterisation of roughness and moisture effects within the scattering problem. The scattering problem of electromagnetic waves from randomly rough surfaces has been an actual research topic over decades and is still not satisfactorily solved due to the lack of an exact closed-form solution. However, for many practical application, approximate solutions are sufficient. In the absence of any direct relationship between surface parameters and backscattering signal models empirical relations have been developed. In the field of radar remote sensing the most common approximation methods are based on the evaluation of backscattering amplitudes considering single or dual-channel SAR data. The choice of an appropriate scattering model is essential for the quantitative estimation of the surface parameters. On the one hand it must contain enough physical structure while on the other hand it should have a right balance between the amount of parameters needed for their description and available observables. As natural surfaces are complex stochastic objects a priori information and assumptions can be used to ...