Effects of off-nadir view angles on the detected spectral response of vegetation canopies

Abstract

The effect of view angle upon the detected spectral response of vegetation canopies is studied, using NERC 1982 airborne multispectral scanner campaign data. An attempt is made to distinguish between the effects of atmosphere and the anisotropic reflectance of vegetation canopies. The influence of atmospheric backscatter is found to be greatest at very short wavelengths (0.42-0.45 μm) Preliminary results confirm that the detected spectral response of vegetation canopies varies with view angle and that the nature and extent of these variations are wavelength-dependent and cover-type dependent. In general, direction-dependent reflectance is symmetric about the nadir value for the visible wavebands, but is manifestly asymmetric in the far-red to near-infrared wavebands. Off-nadir effects for vegetation canopies are found to be smallest in the middle-infrared wavebands.