殷长春,,
刘云鹤,
张博,
蔡晶
吉林大学地球探测科学与技术学院, 长春 130026
基金项目: 国家重点研发计划（2018YFC0807900，课题2），国家自然科学基金项目（41530320，41774125，41904104），国家重点研发计划重点专项（2017YFC0601900，2016YFC0303100），中国科学院先导专项（XDA14020102），北京市科技计划"地球深部探测技术攻关"专项（Z181100005718001）和中央级公益性科研院所基本科研业务费专项经费（JYYWF20180103）联合资助
详细信息
作者简介: 任秀艳, 女, 1989年生, 博士后, 主要从事电磁勘探理论、航空电磁三维正反演研究.E-mail:jdrxy1990@163.com
通讯作者: 殷长春, 男, 1965年生, 教授, 国家海外高端人才, 主要从事电磁勘探理论、航空和海洋电磁方面的研究.E-mail:yinchangchun@jlu.edu.cn
中图分类号: P631收稿日期:2018-08-21
修回日期:2019-12-11
上线日期:2020-02-05
Calibration of airborne EM system over a conductive underground
REN XiuYan,YIN ChangChun,,
LIU YunHe,
ZHANG Bo,
CAI Jing
College of Geo-exploration Sciences and Technology, Jilin University, Changchun 130026, China
More Information
Corresponding author: YIN ChangChun,E-mail:yinchangchun@jlu.edu.cn
MSC: P631--> Received Date: 21 August 2018
Revised Date: 11 December 2019
Available Online: 05 February 2020
摘要
摘要:航空电磁系统校准是开展实际测量工作的基础，校准情况直接影响数据处理和解释.传统校准方法通常假设在自由空间中进行，忽略导电大地耦合影响.然而，实际工作中很难找到绝对高阻的校准场地，导电大地对系统校准和观测数据的影响无法忽视.本文以频率域航空电磁系统为例，对导电大地上航电系统校准技术和校准误差改正方法进行研究.我们首先推导了层状导电大地上水平共面和直立共轴线圈系统的校准公式，结果表明导电大地对航电系统校准尤其是水平共面装置的高频信号影响很大.针对校准过程中大地电导率已知的情况，本文采用非线性方程求解技术一次性确定校准线圈位置和Q值；在没有任何辅助信息情况下，也可直接利用实测数据计算校正因子进行迭代求解.测试结果表明该方法快速、准确、有效.考虑到系统相位和增益调整直接影响观测数据，本文提出了航空电磁数据校准误差的改正算法.实测数据误差改正结果表明，导电大地对高频信号影响严重，校准误差改正后的航空电磁数据与实际地质资料更好吻合.
关键词: 航空电磁/
频率域/
系统校准/
导电大地/
误差改正
Abstract:Airborne electromagnetic (AEM) calibration is the preliminary work of field exploration,which directly influences the quality of data processing and interpretation. Traditional calibration assumes that the underground at the calibration site is very resistive,so that the induction of the earth can be neglected and the calibrated gain of the AEM system well approximates that when the system is calibrated in the free air space. However,it is sometimes very difficult to find such an ideal site in the production,and the earth influences largely on AEM data,especially when the calibration is conducted on conductive underground.
This paper systematically studied the AEM system calibration above the conductive earth and the data correction of calibration error. We take frequency-domain AEM system as example and derivate the calibration formula for both horizontal coplanar and vertical coaxial systems above the conductive layered earth. The ratio of normalized field from the conductive earth and free-space has been used to evaluate the effect of conductive earth on the EM signal. During the calibration,when a priori information on earth conductivity at the calibration site is available,we will directly obtain the location and Q-value of calibration coil by solving a non-linear equation. Otherwise,an iterative technique has been developed to search the earth conductivity from the AEM measurements over the calibration site. Considering that the calibration of the phase and gain influence all the survey data,we propose an algorithm that uses the ratio of normalized magnetic field in the conductive earth model and in the free-space to calculate a factor for the correction of the calibration error.
The numerical experiments show that the conductive earth largely influence the signal,especially for horizontal coplanar configuration in high frequencies. The iterative results without any auxiliary information show that one can obtain the earth resistivity through several iterations from the survey data (in-phase and quadrate parts) and the correction factor efficiently and accurately. The processing of the survey data shows the effectiveness of calibration method.
Key words:Airborne EM/
Frequency-domain/
Calibration/
Conductive earth/
Error correction
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