Influence of topography and sensor view angles on NIR/red ratio and greenness vegetation indices of wheat

Abstract

Reflectance factors of winter wheat were measured with aground-based radiometer to determine the effect of topography and sensor view angle on the diurnal behaviour of two spectral vegetation indices. Data are presented for fields with 10^° slopes in a topographically complex area of central Italy. The ratio of reflectances in near-infrared (NIR) (0.78 to 0.89 μm) to red (0.63 to 0.69 μm) was less sensitive to field aspect than greenness. However, when nadir and off-nadir view angles were compared for the same aspect, greenness displayed less variability. Field aspect and view angle had less effect on both indices when solar zenith angles were small.