Model for inferring soil surface roughness from soil directional reflectance data

A simple geometrical model was used as a computer tool to infer soil surface geometry from soil bidirectional reflectance data. The model simulates rough soil surfaces as equal-sized spheroids regularly spaced on a flat horizontal surface. The geometrical structure is illuminated by the direct solar beams and diffuse skylight. The normalised soil bidirectional reflectance (NR) data collected along the solar principal plane are the basic input into the model. The NR is defined as the proportion of the total radiance measured from an off-nadir direction to the radiance measured from the nadir direction The shape of the spheroids, the distance between them, and the skylight condition parameter are output data of the model.