Variance in bidirectional reflectance over discontinuous plant canopies

An exploratory study of the variance of the bidirectional reflectance over discontinuous plant canopies indicates that the patterns in variance can be related to the properties of the plant canopies. The spatial variance of t he bidirectional reflectance calculated from ASAS images shows peak values at the hotspot and near nadir This behavior can be explained by the geometr ic effect of discontinuous tr-es crowns and the regularization effect. Vali dation of Jupp and Woodcock's two-component geometric optical (GO) model (1 992) shows that ii captures the basic features of the spatial variance of t he bidirectional reflectance over discontinuous plant canopies. Their two-c omponent GO model is modified to account for the spatial interactions of fo ur scene components. Validation shows that the modified GO model improves p redictions. This exploratory study will benefit future use of directional i magery to recover surface parameters by helping characterize the distributi onal properties of directional imagery (C) Elsevier Science Inc.