As China is experiencing the period of rapid social and economic development, man-made electromagnetic noise generated by urban railway has caused an increasingly serious disturbance to geomagnetic observations . As a result, the quality of produced geomagnetic observation data declined sharply. Therefore, it is an urgent task to develop effective methods to reduce this noise. A method of to reduce the noise caused by urban railway transit based on the wavelet domain mixture noise shrink model is proposed. In this paper, we take Tianjin Subway for example to address this approach. A comparative analysis result is made between noise that affects the Tianjin Jinhai observatory and non-noise Hebei Hongshan reference observatory through power spectrum analysis as well as coefficients distribute characteristics in each affected wavelet scales. Non-noise data in midnight between operations of train is identified using an inter-scale wavelet domain model. The thresholds of affected scales are estimated using the inner-scale wavelet domain model. The reduction result shows that in power spectrum, more than lOOdb's noise gain can be reduced to few db's loss. Two non-noise reference observatories' signals are processed by this method, and the average reduction losses are 0. 05nT and 0. 03nT, respectively. The result indicates that the method is able to reduce the noise effectively and improve the quality of geomagnetic observation data.%我国地磁台站观测环境日益受到轨道交通干扰影响,导致地磁观测数据质量下降,制约地磁观测发展.因此,开展干扰抑制的数据处理方法研究,最大限度抑制干扰是提高观测数据质量切实可行的方法.本文提出轨道交通干扰的小波域噪声阈值抑制模型及方法.以天津轨道交通为例,选用受干扰的天津静海地磁台和未受干扰的参考台站河北红山地磁台观测资料,分析并得到受干扰台站轨道交通干扰的功率谱特征和小波域各尺度上的分布特征.采用小波域尺度间模型提取晚间未受干扰时间段；采用尺度内模型对各受干扰尺度阈值进行有效估算并进行抑制.抑制结果表明:该方法使最大100 dB左右干扰增益降低至损失数个分贝.该抑制方法作用在未受干扰的2个参考台站的观测数据,平均抑制损失分别为0.05 nT和0.03 nT.该方法能够较好的抑制轨道交通干扰并最大限度的保留真实的地磁观测数据,提高观测数据质量.
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