SPATIAL CONVERGENCE OF BIDIRECTIONAL REFLECTANCE MODELS

Analyses of bidirectional reflectance data are presented with implicat ions regarding the spatial scales appropriate for inferring irradiance s from radiances reflected by various surface-atmosphere scenes. Multi ple-angle radiance data collected in a nearly simultaneous manner duri ng the 1979 Summer Monsoon Experiment are analyzed using the squared c oherency statistic to suggest a method to deduce the minimum spatial s cale appropriate for irradiance inferences. Spatial convergence of the irradiances inferred from the component radiances is presented as a f unction of averaging distance to imply magnitudes of errors that may r esult from use of ''similar scene'' bidirectional reflectance models. The reduction in the inference errors with an increasing number of ang ular viewing positions is also presented. The data are analyzed in sea rch of preferred viewing directions with the result that little improv ement is imparted to the inference by viewing the scenes from any spec ific view direction.