Spatial Convergence of Bidirectional Reflectance Models

John M. Davis Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado

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Stephen K. Cox Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado

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Abstract

Analyses of bidirectional reflectance data are presented with implications regarding the spatial scales appropriate for inferring irradiances from radiances reflected by various surface–atmosphere scenes. Multiple-angle radiance data collected in a nearly simultaneous manner during the 1979 Summer Monsoon Experiment are analyzed using the squared coherency statistic to suggest a method to deduce the minimum spatial scale appropriate for irradiance inferences. Spatial convergence of the irradiances inferred from the component radiances is presented as a function of averaging distance to imply magnitudes of errors that may result from use of“similar scene” bidirectional reflectance models. The reduction in the inference errors with an increasing number of angular viewing positions is also presented. The data are analyzed in search of preferred viewing directions with the result that little improvement is imparted to the inference by viewing the scenes from any specific view direction.

Corresponding author address: Dr. John M. Davis, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371.

Email: jmdavis@lamar.colostate.edu

Abstract

Analyses of bidirectional reflectance data are presented with implications regarding the spatial scales appropriate for inferring irradiances from radiances reflected by various surface–atmosphere scenes. Multiple-angle radiance data collected in a nearly simultaneous manner during the 1979 Summer Monsoon Experiment are analyzed using the squared coherency statistic to suggest a method to deduce the minimum spatial scale appropriate for irradiance inferences. Spatial convergence of the irradiances inferred from the component radiances is presented as a function of averaging distance to imply magnitudes of errors that may result from use of“similar scene” bidirectional reflectance models. The reduction in the inference errors with an increasing number of angular viewing positions is also presented. The data are analyzed in search of preferred viewing directions with the result that little improvement is imparted to the inference by viewing the scenes from any specific view direction.

Corresponding author address: Dr. John M. Davis, Department of Atmospheric Science, Colorado State University, Fort Collins, CO 80523-1371.

Email: jmdavis@lamar.colostate.edu

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