基于岭回归的土壤含水率高光谱反演研究
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国家重点研发计划项目(2017YFC0403302、2016YFD0200700)和杨凌示范区科技计划项目(2016NY-26)


Inversion of Soil Moisture Content from Hyperspectra Based on Ridge Regression
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    摘要:

    以以色列南部Seder Boker地区采集的粘壤土样品为研究对象。在室内利用ASD FieldSpec 3型高光谱仪获取土壤的原始光谱,在进行数据预处理和不同数学变换后,共获取了4种光谱指标:光谱反射率(REF)、倒数之对数(LR)、一阶微分(FDR)和去包络线(CR)。采用偏最小二乘回归法(PLSR)、逐步回归法(SR)和岭回归法(RR)构建了基于不同指标的土壤含水率高光谱反演模型,并对反演结果进行精度验证与比较。结果表明:REF-PLSR模型在所有回归模型中的反演与预测效果均为最优(R2c=0.990,R2p=0.987),在逐步回归模型和岭回归模型中,LR-SR(R2c=0.981,R2p=0.971)、LR-RR(R2c=0.975,R2p=0.979)均为最佳模型。对于其他3种指标,虽然逐步回归法和岭回归法的建模效果较偏最小二乘回归法略有下降,但R2c均大于0.9,R2p均大于0.8,RPD均大于2.5,RMSE均小于0.03,模型仍具有较好的反演效果;逐步回归法和岭回归法均实现了模型的简化,但岭回归法采用有偏估计从而提高了模型的稳健性,且实现了波段的优选(用于建模的波段数仅为全光谱的03%)。粘壤土土壤含水率LR-RR高光谱反演模型的建立为高光谱模型的优化、土壤含水率的快速测定提供了途径。

    Abstract:

    Obtaining soil moisture quickly and timely can grasp the needs of water of the crops, which is very important for the agricultural production. Soil spectral reflectance provides an alternative method to classical physical and chemical analysis of soil in laboratory for the estimation of a large range of key soil properties. Therefore, the soil moisture was quickly achieved by using hyperspectral technology and the application of ridge regression was explored in the optimization and quantitative analysis of hyperspectral bands. Totally 91 soil samples were collected from the soil depth of 0~5cm in Seder Boker area in the southern Israeli. These soil samples were analyzed in the process of physical and chemical properties in laboratory. After that, the raw hyperspectral reflectance of soil samples was measured by an ASD FieldSpec 3 instrument equipped with a high intensity contact probe under the darkroom conditions. Next, the raw spectral reflectance (REF) was transformed to three spectral indices, i.e. inverselog reflectance (LR), the first order differential reflectance (FDR) and continuum removal reflectance (CR). Regression models of soil moisture with different indices were established by three methods: partial least squares regression (PLSR), stepwise regression (SR) and ridge regression (RR). The inversion results of the model were validated and compared with each other. The results showed that the method of LR transform can eliminate the interference of external factors much better, and it appeared to be the optimal spectral index in stepwise regression model and ridge regression model (R2c were 0.981 and 0.975, and R2p were 0.971 and 0.979). For the three spectral indices about REF, FDR and CR, although the modeling effect of SR and RR was slightly lower than that of PLSR, the coefficient of modeling determination was above 0.9. Both SR and RR had simplified and optimized the model, but RR had better validation results and the number of bands used for modeling was only 0.3% of the full spectrum (400~2400Nm). After comparing the three regression models established with the four spectral indices, the LR-RR model not only had the characteristics of simple model and less calculation, but also improved the robustness of the model better by using biased estimation at the cost of losing the part accuracy. The result indicated that ridge regression method can not only achieve the efficient selection of hyperspectral bands, but also use the LR-RR hyperspectral inversion model for the reference of monitoring the aerospace hyperspectral remote sensing of regional soil moisture in the future.

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张智韬,王海峰,KARNIELI Arnon,陈俊英,韩文霆.基于岭回归的土壤含水率高光谱反演研究[J].农业机械学报,2018,49(5):240-248. ZHANG Zhitao, WANG Haifeng, KARNIELI Arnon, CHEN Junying, HAN Wenting. Inversion of Soil Moisture Content from Hyperspectra Based on Ridge Regression[J]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(5):240-248

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  • 收稿日期:2017-10-27
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  • 在线发布日期: 2018-05-10
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