玉米全氮含量高光谱遥感估算模型研究

    Hyperspectral remote sensing estimation models for nitrogen contents of maize

    • 摘要: 该文对不同品种玉米测定了其室内光谱反射率及其对应的全氮含量,采用相关性分析以及单变量线性与非线性拟合分析技术,对全氮含量与原始光谱反射率、光谱反射率一阶微分、一些高光谱特征参数(如红边波长、红边位置以及红边面积等)以及由一阶微分光谱所构建的一些比值植被指数和归一化植被指数之间的关系进行了分析,结果表明:全氮含量与原始光谱在716 nm处具有最大相关系数(r=-0.847),呈极显著负相关,并且基于此波长所构建的对数关系估算模型明显优于线性模型;与光谱反射率一阶微分值在759 nm处具有最大相关系数(r=0.944),呈极显著正相关,并且基于此波长所构建的线性和非线性模型的拟合效果接近;对于所选取的3类高光谱特征变量,全氮含量除了与黄边位置(λy)以及由红边面积和黄边面积所构建的比值植被指数和归一化植被指数的相关性较弱之外,与其余变量均呈极显著相关关系,说明由这些变量对玉米全氮含量进行估算具有可行性;对所建立的各类方程进行精度检验,最终筛选确定由759 nm处的光谱反射率一阶微分值所构建的指数模型作为对玉米全N含量的预测模型最为理想。

       

      Abstract: The hyperspectral reflectances of different organs(including leaves, stem) and corresponding nitrogen contents of different species of maize were measured in the experiment. The correlation among raw hyperspectral reflectance, hyperspectral characteristic variables, RVI, NDVI and chlorophyll contents were analyzed. The results show that the raw spectral reflectance has the maximum negative correlation coefficient at 716 nm(r=-0.847) with nitrogen contents and the logarithm model constructed with reflectance at this point is the better one as compared to linear model; the first derivative spectral reflectance has the maximum positive correlation coefficient at 759 nm(r=0.944) and the linear and non-linear models have the similar capacity for the nitrogen estimation; as to hyperspectral characteristic variables, they all show significant correlation with nitrogen contents except λy, SDr/SDy and (SDr+SDy)/(SDr-SDy). Those results indicate that the variables adopt in this paper have great potential for nitrogen content estimation. By the precision evaluation of estimation models, the logarithm models constructed by the first derivative reflectance at 759 nm was proved to be the best for the estimation of maize nitrogen contents.

       

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