The state-of-the-art on radiative transfer modeling in vegetation cano
pies and the application of such models to the interpretation and anal
ysis of remotely sensed optical data is summarized. Modeling of top-of
-the-atmosphere and top-of-the-canopy radiance field is developed as b
oundary value problems in radiative transfer. The parameterization of
the constituent functions with simple models and/or empirical data is
outlined together with numerical solution methods and examples of resu
lts of model validation. Caveats in the assignment of signal character
istics to surface properties are itemized and discussed with example r
esults. Algorithms to estimate surface properties from remote observat
ions are classified as spectral vegetation indices, model inversion, e
xpert systems, neural networks, and genetic algorithms. Their applicab
ility is also discussed.