Two-layered forest models in multi-baseline PolInSAR

The scope of this paper is to provide a general discussion about the role of two-layered models in the investigation of forested areas through multi-baseline PolInSAR data, with particular reference to three questions: i) to what extent do two-layered models correctly represent Radar scattering from forested areas? ii) what is the physical meaning associated with each layer? iii) is it sufficient to correctly retrieve forest top height to claim the whole model is correct? The discussion will be provided by considering the general problem of decomposing the second order statistics of the data into ground-only and volume-only contributions. Such an approach allows a compact representation of physically valid models through two real numbers, and a straightforward interpretation of their physical features. The discussion will be supported by experimental results from the ESA campaigns BioSAR 2007 (semi-boreal forest, PBand), BioSAR 2008 (true boreal forest, P-Band and L-Band), and TropiSAR1 (tropical forest, P-Band).