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This Algorithm Theoretical Basis Document (ATBD) describes an algorithm used to retrieve information on the nature and properties of vegetated terrestrial surfaces from an analysis of Level P products derived from the SPOT4/VEGETATION instrument developed jointly by several European countries. The algorithm takes the form of a spectral index, i.e. a set of formulae, which transform calibrated spectral directional reflectances into a single numerical value. The index has been optimised to assess the presence on the ground of healthy live green vegetation. The optimisation procedure has been constrained to provide an estimate of the Fraction of Absorbed Photosynthetically Active Radiation (FAPAR) in the plant canopy. This algorithm delivers, in addition to the FAPAR product, the so-called rectified reflectance values in the red and near-infrared spectral bands. These are virtual reflectances largely decontaminated from atmospheric and angular effects, which are still depending on the sensor and platform orbital specifications. This document identifies the sources of input data, outlines the physical principles and mathematical background justifying this approach, describes the proposed algorithm, and lists the assumptions and limitations of this technique.

Additional information

Authors: GOBRON N ET AL, European Commission, Joint Research Centre, Institute for Environment and Sustainability, Ispra (IT)
Bibliographic Reference: EUR 20146 EN (2002), pp.19. Euro: Free of charge
Availability: Available from European Commission, JRC Knowledge Management Unit, Ispra (IT) Tel: +39 033278 9843 or +39 033278 9864 Fax: +39 033278 9623 E-mail:
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