冬小麦红边参数各向异性特征分析

基于冬小麦冠层高光谱二向性反射波谱数据及其配套的非波谱参数，对可见光至近红外波段二向性反射特性和红边参数随观测角度的变化情况进行了分析。结果表明：冬小麦在太阳主平面呈现出强烈的各向异性反射特性。不同叶面积指数下，由于作物冠层的结构特征和其他组分参数发生较大变化，其二向性反射特性在强度和趋势上也有一定的变化。红边幅值及红边峰值面积随观测角度的变化而发生了变化，呈现为各向异性特征,而红边位置几乎不发生变化。鉴于以往采用垂直观测时的红边参数推算植物生化组分含量，该文指出应选取合理观测角度下的红边参数来精确反演其他相关参数。另外为了定量描述红边幅值随观测角度而变化，提出了红边幅值各向异性指数和红边幅值各向异性因子。

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.