  The performance of model-based decomposition approaches rooted in the
Freeman-Durden concept is an active research line in PolSAR field according to
the considerable attention it has deserved along the last twenty years.
Certainly, most of subsequent proposals have been driven by the only objective
of getting a better qualitative balance among scattering mechanisms according
to theoretical expectations. This idea is not a negative aspect per se, as has
led to a more rigorous understanding of orientation effects in both urban and
natural areas and hence to improved land cover classifications. However, an
in-depth quantitative analysis on the output parameters is usually lacking in
this topic. The attention has been mostly paid to the power of dominant
contributions, whereas the accuracy and interpretation of other parameters
useful for practical applications have been almost systematically overlooked.
The questions that remain to be answered are: What is the actual role of all
parameters describing the models? Can we assign them a consistent physical
interpretation or are some of them acting just as fitting parameters? The
present work aims to promote the discussion on these open issues regarding the
quantitative assessment of model-based PolSAR decomposition schemes. To proceed
with, we have simulated the coherency matrix according to one of existing
general models and different scenarios. The inversion performance has been
analysed in terms of the histograms of output parameters, standard deviation
and bias. The analysis reveals that even the backscattering powers associated
with all three basic scattering mechanisms are estimated with a non-negligible
error higher than 10% for some cases. Despite these conclusions are subject to
a particular model and inversion approach they suggest that a careful
consideration of physically-based decompositions outcomes should be taken.
