The GeoSail model: a simple addition to the SAIL model to describe discontinuous canopy reflectance

The scattering from arbitrarily inclined leaves (SAIL) model was combined with the Jasinski geometric model to simulate canopy spectral reflectance and fraction of absorbed photosynthetically active radiation (fAPAR) for discontinuous canopies. This model is called the GeoSail model. Tree shapes are described by cylinders or cones distributed over a plane. Spectral reflectance and transmittance of trees are calculated from the SAIL model to determine the reflectance of the three components of the geometric model: illuminated canopy, illuminated background, and shadowed background. Although the GeoSail model is relatively simple, calculations of canopy reflectance and fraction of intercepted photosynthetically active radiation (fIPAR) compared well with measurements collected in field experiments in forests in Minnesota and Oregon.