Polarized visible light as an aid to vegetation classification

Radiation, when reflected from the surface of the earth, can be described in terms of both its radiance and its polarization and yet remote sensing has concerned itself with the measurement of radiance and has paid little attention to the measurement of polarization. However, the use of polarization measurements in remote sensing may increase as NASA have included polarizing filters on the satellite-borne Multispectral Resource Sampler (MRS), which may be launched in the mid-1980s. Photographic measurements of percent reflected visible light (percent RVL) and percent polarised visible light (percent PVL) were taken from a light aircraft on two summer days and two winter days. The study area was a heathland with seven land cover classes. In the summer, percent RVL, percent PVL, and percent RVL plus percent PVL could discriminate four land-cover classes. In the winter percent RVL plus percent PVL could discriminate five land-cover classes, percent PVL could discriminate four land-cover classes and percent RVL could discriminate only three land-cover classes. It was concluded that measurements of percent PVL when combined with measurements of percent RVL improved vegetation discrimination in winter months.