Uniqueness of multiangular measurements. II. Joint retrieval of vegetation structure and photosynthetic activity from MISR

This paper describes the implementation of a physical and mathematical approach to design a simple 2-dimensional algorithm dedicated to the interpretation of data collected by MISR. One dimension of information fully exploits the spectral information in the blue, red and near-infrared bands while the other dimension capitalizes on the multiangular capability of MISR to assess the anisotropic behaviour of terrestrial surfaces with respect to solar radiation. This approach delivers an estimate of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) that relates to the vegetation photosynthetic activity. The anisotropy shape is strongly related to the architecture of the vegetation and, under some favourable conditions, it permits revealing some type of surface heterogeneity. The proposed VEGetation Activity and Structure (VEGAS) algorithm for MISR therefore delivers two axes of information representing the FAPAR and the vegetation structure at the MISR subpixel full spatial resolution.