准确监测土壤有机碳密度SOCD(Soil Organic Carbon Density)对调控土壤碳汇、合理利用土壤资源具有重要意义.机载高光谱影像为精细化SOCD制图提供了重要数据源.由于机载高光谱在数据收集过程中易受到外部因素的影响,光谱中存在噪声影响SOCD的估算精度.因此,本研究旨在探究基于机载高光谱影像估算SOCD的技术流程.对原始光谱进行预处理,包括一阶微分FD(First Derivative)和包络线去除CR(Continuum Removal)变换.采用遗传算法GA(Genetic Algorithm)选择特征波段,并结合不同回归方法,如偏最小二乘回归 PLSR(Partial Least Square Regression)、多元线性回归 MLR(Multiple Linear Regression)、支持向量机 SVM(Support Vector Machine)和人工神经网络 ANN(Artificial Neural Network)估算SOCD.结果表明,在经过GA特征波段选择后,原始光谱、FD光谱和CR光谱预测SOCD的精度均有所提高.使用原始光谱特征波段,PLSR、MLR、SVM和ANN共4种模型预测SOCD的决定系数R2分别为0.672、0.621、0.551和0.678.使用FD与CR光谱特征波段的R2范围分别在0.452-0.593和0.332-0.602,具有较大的误差.利用原始光谱的特征波段进行SOCD数字制图,不同回归模型预测的SOCD在空间上具有较为相似的变化趋势,与SOCD测量值较为相近,绝对误差较大的点多出现在采样点边缘附近.
Mapping of soil organic carbon density at farmland scale based on airborne hyperspectral images
Accurate monitoring of Soil Organic Carbon Density(SOCD)is important for regulating soil carbon sinks and rationally using soil resources.Airborne hyperspectral images provide important data sources for SOCD mapping.The noise in the spectrum affects the accuracy of SOCD estimation because airborne hyperspectral images are easily affected by external factors during data collection.A set of technical processes that are suitable for airborne hyperspectral data processing is still lacking.Therefore,this study aims to investigate the technical process of SOCD estimation based on airborne hyperspectral images.The original spectra are preprocessed by First Derivative(FD)and Continuum Removal(CR)transform.Genetic Algorithm(GA)was used to select the feature bands.Different regression methods,such as Partial Least-Squares Regression(PLSR),Multiple Linear Regression(MLR),Support Vector Machine(SVM),and Artificial Neural Network(ANN),were used to estimate SOCD.Results showed that the accuracy of SOCD prediction for original,FD,and CR spectra was improved after feature band selection by GA.With the feature bands of original spectra,the R2 of SOCD predicted by PLSR,MLR,SVM,and ANN are 0.672,0.621,0.551,and 0.678,respectively.The range of R2 are 0.452-0.593 and 0.332-0.602 with FD and CR feature bands,respectively,which demonstrate large errors.The feature bands of the original spectrum were used in this study for SOCD mapping.The SOCD predicted by four regression models has a highly similar trend in space and is similar to the SOCD measured value.The points with large absolute errors mostly occur near the edges of the sampling points.
万方数据
维普
