Inversion of vegetation canopy reflectance models for estimating agronomic variables. III. Estimation using only canopy reflectance data as illustrated by the suits model

Abstract

The technique for estimating agronomic and spectral parameters for a vegetation canopy from the canopy reflectance (CR) data, described earlier (Goel et al., 1984), has been improved. These improvements are twofold: first, one can now, in principle, estimate various parameters using only CR data, in the infrared band, for a set of solar/view angles; second, the method is now computationally much more efficient. These improvements are illustrated via Suits' model. An analysis of the sensitivity of the calculated agronomic and spectral parameters to changes in the CR is also carried out. This analysis suggests that, in general, for expected levels of errors in the measurement of CRs and the accuracy with which the Suits model is likely to represent CR, one is unlikely to be able to estimate agronomic parameters like leaf area index (LAI) and average leaf angle (ALA) using only measured CR data. Such a determination will likely require ancillary data on the reflectance and transmittance of vegetation elements and on the soil reflectance.