基于高光谱数据的土壤有机质含量反演模型比较
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上海市科学技术委员会科研计划项目(13231203602)


Comparison on Inversion Model of Soil Organic Matter Content Based on Hyperspectral Data
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    摘要:

    以土壤多样化的陕西省横山县为研究区域,比较了3种基于高光谱数据的土壤有机质含量反演模型,在实验室利用ASD Field Spec FR地物光谱仪对横山县野外采集的土壤样品进行光谱测定,并通过重铬酸钾氧化容量法测定土壤有机质含量。然后对原始光谱反射率的倒数进行微分运算获得其一阶导数光谱,将原始光谱反射率、一阶导数光谱分别与土壤有机质含量进行相关性分析,得到相关性系数r较高的特征波段的一阶导数光谱,直接建立基于一阶导数光谱的多元线性逐步回归分析(MLSR)模型。同时针对这些相关性系数较高的特征波段的一阶导数光谱进行主成分分析(Principal component analysis, PCA),利用主成分分析得到的结果分别建立BP神经网络反演模型(PCA-BP)和多元线性逐步回归分析模型(PCA-MLSR)。用上述3种方法进行土壤有机质含量反演,并对3种反演结果进行精度验证与比较。实验分析结果表明:在3种模型中,基于主成分分析结果构建的PCA-BP模型在土壤有机质含量反演中决定系数(R2)最高,为0.8930,均方根误差(RMSE)为0.1185%;其次为运用全部主成分PCA分析结果构建的多元线性逐步回归模型,R2为0.7407,RMSE为0.1613%;而采用一阶导数光谱反射率构建的多元线性逐步回归模型中,最佳反演模型R2仅为0.6899,RMSE为0.1710%。由此说明,PCA-BP模型有机质含量反演精度明显高于多元线性逐步回归模型,利用全部主成分进行多元逐步回归,其有机质含量反演精度优于仅用累计方差贡献率大于90%的主成分进行多元逐步回归的精度,可以更好地反演土壤有机质的含量。

    Abstract:

    Hengshan county of Shaanxi was taken as research area, three kinds of soil organic matter content inversion model based on hyperspectral data were compared. The soil samples were collected in the field. The ASD Field Spec FR was used to measure the soil samples’ spectrum. The content of soil organic matter was measured via potassium dichromate oxidation volumetric method in laboratory. Then the first derivative of spectral data was obtained by applying the reciprocal difference to original spectral reflectance, and the multiple linear stepwise regression (MLSR) analysis model of the first derivative of spectral data was constructed. The correlations between the original spectral reflectance, the first derivative of spectrum and soil organic matter content were analyzed. The first derivative spectra of the characteristic bands which had high correlation coefficient with soil organic matter content were obtained. Based on the first derivative spectra, the MLSR model was established. Meanwhile, the principal component analysis (PCA) was performed for the first derivative spectra of the characteristic bands with high correlation coefficient. The PCA-BP model and PCA-MLSR model were established by the results of PCA. The soil organic matter content was inversed by three methods, and the inversion accuracy was validated and compared with each other. The results showed that the coefficient of determination (R2) and root mean square error (RMSE) between the measured value and inversion value were 0.8930 and 0.1185% with PCA-BP model, respectively, and the R2 and RMSE between the measured value and inversion value were 0.7407 and 0.1613% with PCA-MLSR model, respectively. However, in these MLSR models which based on the first derivative spectra, R2 and RMSE between the measured value and inversion value were 0.6899 and 0.1710% with the optimal inversion model, respectively. Based on the results, the inversion accuracy of soil organic matter content in PCA-BP model was higher than that of MLSR model. In MLSR model, the inversion accuracy of soil organic matter content by using all principal component was better than that only using the partial principal component, of which the cumulative variance contribution was greater than 90%. The content of soil organic matter can be well inversed.

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叶勤,姜雪芹,李西灿,林怡.基于高光谱数据的土壤有机质含量反演模型比较[J].农业机械学报,2017,48(3):164-172.

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  • 收稿日期:2016-07-29
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  • 在线发布日期: 2017-03-10
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