Anisotropic characteristics analysis of red edge parameters of winter wheat

Based on canopy hyperspectral bidirectional reflectance data and their ancillary parameters, bidirectional reflectance properties of winter wheat were analyzed in the visible and near infrared(VNIR) spectral bands. The results show that winter wheat exhibits strong anisotropic characteristics in the solar principal plane. In addition, the bidirectional reflectance properties of winter wheat change in intensity and trend, because the canopy structural properties change with growth stages and leaf area index(LAI). The changes of red edge parameters with the change of view zenith angle in the solar principal plane were also analyzed, and the red edge amplitude and area of red edge are different at different view zenith angles, whereas the position of red edge almost does not shift. But the values of red edge amplitude and area of red edge at nadir view zenith angle were chosen by many researchers when inversing plant biochemical concentration. This paper suggested that red edge parameters at appropriate view zenith angle should be chosen to inverse other plant biochemical parameters accurately. In this paper, in order to depict quantitatively the change of red edge amplitude with view zenith angles in the solar principal plane, the anisotropy index and the anisotropy factor of red edge amplitude were put forward.