ABSTRACT
The visual detection of vehicles and personnel depends upon a number of factors: reflected/emitted color (photometry), contrast (spectral resolution), shapes, and motion. Optical polarization has not been used although radar, its relative, has been readily accepted and applied. There are clear analogs between radar optics and light optics. Radar is used in four polarized modes to observe vertical (V), horizontal (H), and crosspolarized (HV, VH) reflectance. In addition, because of the high spectral coherence length of radar signals (monochromaticity), radio interferometry can be used as in astronomy. Like that of the angular resolution of radar is governed by the size of the antenna aperture, but the bigger the antenna the weaker the signal that can be observed.
