Winter boreal forest canopy BRF results: comparisons between airborne data, laboratory simulations and geometrical-optical model data

A uniform mature jack pine stand was the subject of detailed airborne and field optical measurements as part of the BOReal Ecosystem-Atmosphere Study (BOREAS) under typical winter conditions. Airborne multi-angle imagery was collected on February 8, 1994 with the Compact Airborne Spectrographic Imager (CASI). The airborne data in the solar plane, converted to surface reflectance, provided a direct measure of the canopy bidirectional reflectance factors. Input data required to evaluate the Li and Strahler geometric-optical/mutual shadowing model were acquired on the day prior to the airborne data acquisition. In addition, a scale laboratory canopy model was created of a portion of the BOREAS jack pine site, complete with architectural tree models, replication of the stem map based on aerial photography and a salt background to mimic snow. This model canopy was viewed with the CASI sensor over a wide range of zenith angles within the controlled environment of the laboratory. GOMS simulations of the model canopy were rigorously compared with BRFs extracted from the resulting high resolution imagery