Modelling the Scattering of Light by Vegetation in Optical Remote Sensing: Statement of the Problem for the 3-D Homogeneous Case

This paper review the problem of radiation transfer in geophysical media, comparing the particular issues occurring in plant canopies to those occurring in the atmosphere. The discussion takes place in the context of remote sensing applications, where the main constraint is to be able to invert the photon transport model against observations to retrive the properties of the observed media.To facilitate the solution of the radiative coupling between the vegetation and atmospheric layers, we use the same formal approach in both media, and specify the extinction and differential scattering coefficients in a similar way. The accurate description of the radiation transfer within a vegetation layer is complicated by the fact that both of these coefficients depend on the position of the external sources of radiation, and by the lack of precise knowledge about the radiative boundary conditions at the top and bottom of this layer. Effective solutions to the radiation transfer problem in plant canopies requires the introduction of specific hypotheses, for instance in the treatment of the multiple scattering contribution.JRC.(SAI)-Space Application Institut