Investigation of linear spectral mixtures of the reflectance spectra using laboratory simulated forest scenes

In this study, we used laboratory data to investigate the effects of multiple scattering between tree crowns and snow background on the linearity of mixtures of the reflectance of winter forest scenes. Several scenes were designed in the laboratory to simulate the natural forest winter landscape. Hyperspectral images of the designed scenes were acquired by the Compact Airborne Spectrographic Imager (CASI). Each scene was decomposed by linear spectral unmixing of the scene reflectance spectrum using sunlit crown, shaded crown, sunlit background, and shaded background as end members. The SPRINT canopy model was employed to evaluate the results of the linear spectra unmixing approach. Our results show that if a linear unmixing approach is used for the designed scenes, the errors in the fractions of end members are as high as 25 percent relative to the fractions obtained by the SPRINT model. This investigation suggests that non-linear mixture models may be needed to account for the multiple scattering between tree crowns and snow background.