植被冠层反射太阳光会产生部分偏振光, 这为偏振遥感探测提供了信息源。 利用地基平台开展野外偏振测量是非常重要的研究, 它不仅能获取植被冠层本质的偏振反射特性, 而且还可以与机载或者星载平台数据进行匹配； 虽然研究者们已经通过机载或者星载偏振探测器获取了大量植被冠层的偏振反射信息, 但是关于地面植被冠层偏振反射分布特性的研究却很少。 因此, 为了详细研究植被冠层的偏振反射特性, 基于野外多角度高光谱偏振测量与偏振反射物理机制, 分析了植被冠层偏振光谱特性及其偏振反射分布特性； 随后, 反演了两种偏振模型的参数, 将测量值与模拟值进行对比分析。 研究结果发现, 植被冠层的偏振反射具有明显的各项异性特征, 而且与波长之间存在微弱的关系； 同时, 偏振模型可以很好地模拟植被冠层的偏振反射信息, 可以作为研究植被冠层的理论依据。 该研究测量的偏振反射信息与模型计算值之间呈现良好的吻合性, 既描述了植被冠层偏振反射分布特性, 又证明模型的有效性和测量结果的准确性。 对植被冠层偏振特性的详细研究, 不仅有助于完整地解释植被冠层与电磁波之间的辐射响应特征, 而且对于偏振遥感对地观测以及地表偏振信息对大气偏振信息的研究也具有重要科学价值。

For remote sensing of vegetation, light scattered from canopy is partly polarized, which is the basis data for the polarized remote sensing. Thus, it is significant to perform the field polarization measurement of vegetation canopy using the ground-base instrument. The field polarization measurement data not only contain the physical polarization property of vegetation canopy, but also can be used to match with the polarimetry measurements from airborne and spaceborne sensors. Several previous studies have paid some attentions to the polarization of vegetation canopies, because of some airborne and spaceborne instruments can be used to obtain multi-angular polarized information. However, the investigation about the field measurements is rare. To study the contribution of this polarized light to multi-angular observations of reflectance over vegetation canopy, a hyperspectral bidirectional polarized reflectance data of one type of vegetation canopy acquired over a wide viewing range in field was analyzed in this paper. Then, it was analyzed with respect to basic physical polarized reflectance mechanisms. The impact of angular data sampling and the variation of the polarized spectral reflectance were also analyzed. Furthermore, we compared the modeled polarization from two current polarimetric models with our measured polarization of vegetation canopy at selected wavelength. Analyses showed that all the models were good fitted to the measurements; there was a very small spectral variability of the polarized reflectance of vegetation canopies. The good agreement between polarization measurements and modeled results confirms the ability of models and the accuracy of field experiments. These results, deepening our understanding of the scattering properties of vegetation canopies, suggest that we can model the polarization accurately by all the current polarimetric models; they are valuable for the development of polarized remote sensing applications on earth science and useful for studying the contribution of earth polarization on the atmosphere polarization.