光谱学与光谱分析, 2015, 35 (1): 162, 网络出版: 2015-01-28
EEMD在土壤剖面反射光谱消噪中的应用
EEMD De-Noising of Reflecting Spectrum in Soil Profiles
土壤剖面光谱 集合经验模态分解 信号消噪 消噪效果 Soil-profile spectrum Ensemble empirical mode decomposition Signal de-nosing De-noising effect
摘要
实测光谱常含有大量干扰信息, 消噪在光谱数据处理和分析中极为重要, 它直接影响后续的定量分析和信息挖掘。因此, 选择适当的消噪方法是改善光谱分析精度, 提升光谱分析能力的一个关键性突破。集合经验模态分解(EEMD)方法是一个以信号固有特征尺度为度量的时空滤波过程, 能充分保留信号本身的非线性和非平稳特征, 在信号的滤波和消噪中具有较大的优势。结合EEMD的多尺度滤波特性, 提出了一种新的EEMD阈值光谱消噪方法, 并应用于新疆塔里木河中游典型绿洲33个土壤剖面反射光谱数据的预处理。为探讨EEMD阈值法在土壤剖面反射光谱消噪中的效用, 对EEMD阈值法和小波阈值法的消噪结果进行了对比分析。结果表明: 与传统的小波阈值法相比, EEMD阈值法消噪结果的信噪比从14.836 6 dB提高到34.275 7 dB, 均方根误差由6.786 1×10-5降到7.240 6×10-6, 相关系数从0.982 5提高到0.999 8, EEMD阈值法的三个消噪效果衡量指标均优于小波阈值法。证明了EEMD阈值法可有效地去除土壤剖面光谱噪声, 较好地保留了光谱的细节信息, 提高了光谱的定量分析精度, 且与小波阈值消噪方法相比具有较强的可靠性和自适应优势, 作为光谱数据预处理的一种新方法, 其应用前景良好。
Abstract
In the present paper, based on the multi-resolution attribute of EEMD (ensemble empirical mode decomposition) method, we presented a new de-noising method for analyzing spectrum, and applied it to process the reflecting spectrum data of 33 soil profiles in the typical oasis located in the middle reaches of the Tarim River. To explore the de-noising effect of EEMD threshold method for reflecting spectrum in soil profiles, we compared EEMD threshold method with wavelet transform method. The results showed that compared with traditional wavelet transform method, the signal to noise ratio (SNR) was improved from 14.836 6 to 34.275 7 dB, and the root mean square error (RMSE) was reduced to 7.240 6×10-6 from 6.786 1×10-5 and the correlation coefficient (r) increased from 0.982 5 to 0.999 8. Therefore, three de-noising effect indicators of EEMD threshold method are better than those of wavelet transform method. This proved that the EEMD threshold method can effectively eliminate the noise of soil-profile spectrum and also preserve the detailed information of the original spectra well. Thus, the analysis precision of the spectrum will be improved. In addition, by contrast with the wavelet threshold method, the EEMD threshold method is adaptive and is fairly reliable. As a new method for spectral pretreatment, the EEMD threshold method will have a good application prospect in spectra de-noising.
邓凯, 丁建丽, 杨爱霞, 牛增懿. EEMD在土壤剖面反射光谱消噪中的应用[J]. 光谱学与光谱分析, 2015, 35(1): 162. DENG Kai, DING Jian-li, YANG Ai-xia, NIU Zeng-yi. EEMD De-Noising of Reflecting Spectrum in Soil Profiles[J]. Spectroscopy and Spectral Analysis, 2015, 35(1): 162.