高光谱空间中混合象元非线性反射特征研究

Study on the Nonlinear Characteristics of the Mixed Pixel's Reflectance in Hyperspectral Space

在入射天顶角为50°,探测方位角为45°的实验条件下,利用地物多角度二向反射平台和FieldSpec3Hi-Res便携式地物波谱仪获取了24组荷叶与水体组成的混合象元反射波谱,并根据其波谱特性建立了高光谱空间。通过计算不同荷叶面积比例的混合象元反射光谱与参照光谱的波谱角及相似度,分析了相似度与荷叶面积比例的关系,在此基础上采用线性模型、对数模型、二次多项式模型进行拟合,拟合优度分别为63.6%,76.2%和82.9%,根据混合像元光谱矢量与参照反射光谱矢量之间的实际关系,确定最佳拟合模型具有非线性的分段特征。在分析拟合曲线的基础上,提出水生植物与水体组成的混合像元可能具有植被特征临界值的设想,研究结果有利于加深对混合象元的理解,同时也为混合象元的光谱分解提供了新的思路。

Under the experimental condition of the 50 degree incidence zenith angle and 45 degree detection azimuth,24 groups of reflectance spectral of the mixed pixel of lotus and water body acquired using the reflex platform and FieldSpec 3 Hi-Res portable spectrum instrument.The hyperspectral space was built based on the reflectance character.The relationship between similarity and the index of lotus area ratio was analyzed using the linear,logarithm and quadratic curve fitting,and the goodness of fitting is 63.6%,76.2% and 82.9% respectively.According to the real relationship of the mixed pixel spectral vector and the reference spectral,the best fitting model has nonlinear characteristics.The idea that the mixed pixel may have the critical value was proposed on the base of the analysis.The research result will help understand the mixed pixel further,and provide a new direction for unmixing the mixed pixel.