January 13, 2009

LAI Validation

The algorithm is based on the SAIL model of radiative transfer in the canopy + soil system (Verhoef, 1985 ; Kuusk, 1995 ; Bicheron and Leroy, 1999). The canopy is represented as a turbid medium of leaves with spherical orientation. More specifically, the single scattering component is that of Nilson and Kuusk (1989)'model, while the multiple scattering component is that of the SAIL model. The directional and spectral optical properties of the soil are modelled using Walthall et al. (1985) and a model derived from that of Price (1990) respectively. The leaf optical properties are described with the PROSPECT model (Jacquemoud and Baret, 1990), as a function of leaf components (chlorophyll concentration Cab, senescent pigments concentration Cs, dry matter content Cdm, number of layers N in a leaf). In direct mode, the canopy model predicts the top of canopy reflectance at any wavelength and sun-view direction as a function of the soil and canopy parameters : LAI, N, Cab, Cs, Cdm, l* (ratio of leaf size divided by canopy height), soil spectral slopes a1 and a2.


Bicheron, P., and M. Leroy, 'A method of biophysical parameter retrieval at global scale by inversion of a vegetation reflectance model', Remote Sensing of Environment, 67, pp. 251-266, 1999.

Jacquemoud, S. and F. Baret, 'PROSPECT : a model of leaf optical properties spectra', Remote Sensing of Environment, 34, 75-91, 1990.

Kuusk, A., 'A fast invertible canopy reflectance model', Remote Sensing of Environment, 51, 342-350, 1995.

Nilson, T., and A. Kuusk, 'A reflectance model for the homogeneous plant canopy and its inversion', Remote Sensing of Environment, 27, 157-167, 1989.

Price, J.C., 'On the information content of soil reflectance spectra', Remote Sensing of Environment, 33, 113-121, 1990.

Verhoef, W., 'Light scattering by leaf layers with application to canopy reflectance modelling: the SAIL model', Remote Sensing of Environment, 16, 125-141, 1984.

Walthall, C.L., J.M. Norman, J.M. Welles, G. Campbell, and B.L. Blad, 'Simple equation to approximate the bidirectional reflectance from vegetative canopies and bare soil surfaces', Applied Optics, 24, n°3, 383-387, 1985.