红外与毫米波学报, 2011, 30 (4): 316, 网络出版: 2011-08-18   

不同尺度的微分窗口下土壤有机质的一阶导数光谱响应特征分析

Analysis on derivative spectrum feature for SOM under different scales of differential window
作者单位
1 西北农林科技大学 资源环境学院, 陕西 杨凌712100
2 咸阳师范学院 资源环境系, 陕西 咸阳712000
摘要
使用高光谱仪ASD Field Spec在波长范围400~1000 nm内采集有机质含量不同的土壤反射光谱数据并作对数变换处理; 之后在不同尺度的微分窗口下求取其一阶导数(一阶导数光谱)并进行小波阈值去噪; 从一阶导数光谱中提取特征参数表征有机质含量变化.结果表明, 微分窗口尺度w=1~5时, 土壤一阶导数光谱中含有大量噪声, 对一阶导数光谱曲线形态和有机质吸收特征的识别造成严重干扰; 微分窗口尺度w=6~15时, 土壤一阶导数光谱中的噪声得到一定程度的去除, 但仍无法准确判别有机质的吸收特征; 微分窗口尺度w=16~30时, 土壤一阶导数光谱中的噪声被有效去除, 其中当w=19时, 从一阶导数光谱中提取的特征参数MD19s与土壤有机质含量的相关系数为-0.803.MD19s能够较为准确地指示有机质含量变化, 而且运算简单, 易于实现, 为在精准农业中采用可见/近红外反射光谱分析技术快速检测土壤有机质提供了新的途径.
Abstract
The hyper-spectral reflectance of soil was measured by a ASD FieldSpec within 400~1000 nm, then treated with logarithmic transformation. First derivative of soil spectra with different scales of differential window were acquired and denoised by the threshold denoising method based on wavelet transform. From the first derivative of soil spectra, feature parameters used as indicators for soil organic matter content were extracted. Results show that: (1) When the number of the scale of differential window was set as W=1~5, it is difficult to identify the spectrum contour and response feature in first derivative of soil spectra because of much noise. (2) When W=6~15, noise in first derivative of soil spectra is partly removed, and spectrum contour is identified roughly. However spectral response feature resulted from different organic content levels can not be identified clearly. (3) When W=16~30, noise in first derivative of soil spectrua is removed effectively. The coefficient of correlation between organic matter content and feature parameter MD19s is 0.803. MD19s can be used as one of the best indicators for soil organic matter content.

刘炜, 常庆瑞, 郭曼, 邢东兴, 员永生. 不同尺度的微分窗口下土壤有机质的一阶导数光谱响应特征分析[J]. 红外与毫米波学报, 2011, 30(4): 316. LIU Wei, CHANG Qing-Rui, GUO Man, XING Dong-Xing, YUAN Yong-Sheng. Analysis on derivative spectrum feature for SOM under different scales of differential window[J]. Journal of Infrared and Millimeter Waves, 2011, 30(4): 316.

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