A physically-based model for retrieving foliar biochemistry and leaf orientation using close-range imaging spectroscopy
In close-range remote sensing, a leaf becomes a more complex medium. In a leaf, its curved surface affects to reflectance. To account this BRDF effect, specular parameter (b_spec) and incident angle (theta_i) are integrated to PROSPECT model. Interestingly, b_spec has more influence to leaf strong absorption region. In that region, most of incident light is absorbed by leaf internal media and then only specularly reflected. Also theta_i has similar sensitivity profile to ALA in PROSAIL. theta_i would be a factor to interpret within-crown PROSAIL parameters.
Reference
Jay, S., Bendoula, R., Hadoux, X., Féret, J. B., & Gorretta, N. (2016). A physically-based model for retrieving foliar biochemistry and leaf orientation using close-range imaging spectroscopy. Remote Sensing of Environment, 177, 220-236.