Surface roughness and slope measurements using polarimetric SAR data

Abstract

In this paper, the circular polarization coherence, /spl rho//sub RRLL/, is investigated as a potential estimator of terrain surface roughness and small-scale slopes. The studies utilize microwave backscatter collected from 1) dielectric surfaces in an anechoic chamber and 2) a desert test site using P-, L-, and C-band NASA/JPL AIRSAR data. These experimental studies and supporting theory, indicate a sensitive decrease of |/spl rho//sub RRLL/| with increasing surface roughness ks over a range 0 /spl les/ ks /spl les/ 1. For the present studies this decrease is caused largely by the depolarizing effects of small-scale surface slopes in the azimuth direction rather than by volume, or multiple scatter. For cases when the scatter is reflection symmetric, the value of |/spl rho//sub RRLL/| depends on the surface roughness and on the local incidence angle. The dependence of |/spl rho//sub PRRLL/| on the local incidence angle is supported by theory and experimental results. For these same scattering cases, however, |/spl rho//sub PRRLL/| is independent of the surface dielectric constant. Estimation of the functional dependency of |/spl rho//sub PRRLL/| versus ks, for a mid-range incidence angle, has been carried out using roughness estimates derived from an empirical model.