ABSTRACT

The monitoring of crop production on a global basis has been a major basic research program funded by NASA. The object is to investigate and improve the modeling of plant canopies and so acquire the potential information in remote sensing that is based on the fundamental physical properties in the input data. Vanderbilt et al. [1] used polarization measurements of two wheat canopies to measure a reflectance factor that is composed of two components of reflected light, specular and diffuse. They identify two key angles: (1) the angle of the polarizer for minimum flux and (2) the angle of incidence of sunlight specularly reflected by a leaf to a sensor. The data were acquired with an Exotech Model 20C spectroradiometer located 6 m above the soil. A rotatable piece of Lsheet was attached to the entrance port. Vanderbilt et al. [1] obtained quantities of maximum reflectance and minimum reflectance (which are related to the position of the polarizer) as well as quantities related to the first and second Stokes parameters and the degree of linear polarization. Their extensive series of measurements were possible only in a laboratory setup.