Four-Scale Linear Model for Anisotropic Reflectance (FLAIR) for Plant Canopies—Part II: Validation and Inversion with CASI, POLDER, and PARABOLA Data at BOREAS

To address the need for a flexible model of the bidirectional reflectance distribution function (BRDF) that is also suitable for inversion, the FLAIR Model (Four-Scale Linear Model for AnIsotropic Reflectance) has been developed [1]. Based on the more detailed Four-Scale Model [2], FLAIR is a linear kernel-like model, developed with the aim of not being limited to specific canopy characteristics or view/illumination geometry, while maintaining a direct relationship between canopy architectural properties and model coefficients. Having been previously demonstrated to have the ability to capture the bi-directional patterns in both forward and inverse modes of calculation, this paper examines the FLAIR model in describing the boreal canopy by applying FLAIR to multiangular data sets obtained by various sensors during BOREAS 1994. Effects of sensor field of view, ranges of view/solar illumination geometry, and multiple sensor use on BRDF derivation and inversion for canopy parameter retrieval are considered.