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The scattered signal, as we have seen, will in general have different polarization characteristics than the incident one. This is true even in very simple models such as reflection from a (non-perfectly conducting) flat surface (see [Beckmann et al., 1963], page 160):
At grazing angles, it was already pointed out by [Katzberg et al., 1996] that the polarization of a GPS signal becomes linear . This is because the ocean surface is a partially conducting dielectric. Thus, with the exception of near-vertical specular incidence, depolarization is expected to occur even in a superscalar model (that is, assuming the surface is flat for polarization analysis purposes) . The same phenomenon occurs in scattering from the sea at optical frequencies.
Research on the polarization aspects of GNSS reflected signals and their possible geophysical content is an on-going active area of work. In [Katzberg et al., 1996] it is pointed out that it may be necessary or even desirable to measure the scattered power in both polarizations. More later?
Giulio Ruffini Fores