The purpose of the investigation described here was to analyze angular bidirectional reflectance variations and test the hypothesis that first order variations could be described from a consideration of shadows created by surface perturbations. The results reported here demonstrate the validity of this approach, and while it is not suitable for calculating absolute spectral reflectance characteristics, the development of such a model was not the objective of the investigation since other models already exist for these calculations. Instead, a model was needed which can make relative angular corrections to bidirectional reflectance measurements independent of the details of surface geometry. The theoretical model derived in this investigation from an analysis of shadow formation is such a model.

Date of this Version