We present a quality control methodology for the currents of marine controlled-source electromagnetic transmitters . The quality level of the transmitting current directly affects the signal-to-noise ratio (SNR) of the electromagnetic-field data, as received by a multicomponent electromagnetic receiver from the seabed. Although the transmitting-current stability is sufficient under normal circumstances, the SNR of the received signal can change owing to factors such as outside noise. In some emergency cases such as instrument failure or a sudden increase in electromagnetic interference that we are not aware of, the frequency and properties of the transmitting current, such as its size and waveform, may change. The traditional current monitoring and data playback tools fail to detect and evaluate the anomalies well and in a timely manner, which introduces considerable errors in the later data-processing procedure. Pertaining to these issues, this paper proposes a comprehensive quality evaluation method for the transmitting current. The proposed algorithm, based on the analytic hierarchy process, is first used to analyze five current stability parameters – current frequency, positive amplitudes, negative amplitudes, discrepancy of ideal waveform, and waveform repetition – and then to define the harmonic energy and calculate the quality of transmitting current (QTC) index of the final data to assess the quality of the transmitting current comprehensively. The results of a marine experiment performed in 2016 show that the algorithm can identify abnormal current data and quantitatively evaluate the current conditions. Under normal circumstances, the QTC index is less than 2 %. The key findings are that the QTC index changes to more than 4 % and some curvilinear features are observed if the transmitting-current quality is poor. These results will provide a positive, significant guide for the evaluation and monitoring of transmitting-current data in marine experiments.

中文翻译：

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基于层次分析法的船用电磁控制源电流综合数据质量评估方法

我们为船用受控源电磁变送器的电流提出了一种质量控制方法。发射电流的质量水平直接影响电磁场数据的信噪比（SNR），这是由多分量电磁接收器从海底接收到的。尽管在正常情况下发射电流的稳定性已经足够，但是由于诸如外界噪声之类的因素，接收信号的SNR可能会发生变化。在某些紧急情况下，例如仪器故障或我们不知道的电磁干扰突然增加，传输电流的频率和特性（例如大小和波形）可能会发生变化。传统的电流监控和数据回放工具无法及时正确地检测和评估异常，这在以后的数据处理过程中引入了相当大的错误。针对这些问题，本文提出了一种针对传输电流的综合质量评估方法。所提出的算法基于层次分析法，首先用于分析五个电流稳定性参数-电流频率，正振幅，负振幅，理想波形的差异和波形重复-然后定义谐波能量并计算质量最终数据的传输电流（QTC）指标的评估，以全面评估传输电流的质量。2016年进行的海洋实验结果表明，该算法可以识别异常当前数据并定量评估当前条件。在正常情况下，QTC指数小于2％。关键发现是，如果传输电流质量较差，则QTC指数变化超过4％，并且观察到一些曲线特征。这些结果将为评估和监测海洋实验中的传输电流数据提供积极，重要的指导。