基于迭代查表法的固定翼时间域航空电磁数据电导率深度成像研究

发布时间：2018-03-16 09:28

本文选题：固定翼航空电磁　切入点：电导率深度成像　出处：《吉林大学》2017年硕士论文　论文类型：学位论文

【摘要】：固定翼时间域航空电磁探测(Fixed-wing Airborne Time-domain Electromagnetic)是一种基于电磁感应定律,以固定翼飞机为载体的地球物理探测方法,具有探测深度深,效率高,成本低等优势,被广泛应用于地质勘查,油气探测等领域。航空电磁探测系统在飞行测量过程中,由于飞行速度,飞机姿态,气压等因素,引起飞行高度和接收线圈姿态角度的改变,影响观测数据,使得电导率深度成像(CDI,Conductivity-Depth Imaging)结果存在误差。本文在国家自然科学基金项目“固定翼时间域航空电磁探测整体反演方法研究”的资助下,研究了飞行高度、接收线圈俯仰姿态角度(pitch)变化引起电磁响应变化,而探测系统无法准确获得pitch、飞行高度,因此本文提出了基于迭代查表法的电导率深度成像算法。主要研究内容包括以下方面:基于航空电磁探测理论,推导了接收线圈任意姿态角度变化下的三分量一维正演计算方法;研究了飞行高度变化对电磁响应的影响;研究了接收线圈摇摆(roll),俯仰(pitch),偏航(yaw)角度变化下的电磁响应特征。针对常规航空电磁系统难以获得pitch信息,将pitch作为参数引入到电导率深度成像中,研究了带pitch的B场双分量(水平分量Bx、垂直分量Bz)查表CDI算法。正演计算多个固定飞行高度各时间道的Bx-Bz-?-pitch数据表,根据实测飞行高度找到对应飞行高度、对应时间道数据表,通过线性插值得到视电导率(?),根据扩散公式求得成像深度,最终实现带pitch的电导率深度成像算法。在高度计示数不准确情况下,将飞行高度和pitch同时作为参数引入到电导率深度成像中,研究了带飞行高度和pitch的迭代查表CDI算法。通过正演计算,建立多个固定飞行高度下各时间道的Bx-Bz-?-pitch数据表和多个固定俯仰姿态角度下各时间道的Bx-Bz-?-height数据表。根据实测Bx、Bz电磁响应在两个数据表中进行查表迭代计算,直至最后一次迭代的?、height和pitch全部满足精度要求,则迭代结束,得到视电导率,飞行高度和俯仰姿态角度信息。利用扩散公式计算各层深度,用平均视电导率计算成像深度,最终实现带飞行高度和pitch的迭代查表电导率深度成像算法。仿真结果表明迭代查表法电导率深度成像不仅优于未考虑飞行高度和俯仰姿态角度误差下的成像结果,而且即使获得比较准确的飞行高度信息,迭代查表法电导率深度成像精度也提高了10%左右。迭代查表法在获得视电导率的同时获得height、pitch,对比分析了迭代查表法获取辅助参数与系统测量参数间误差;研究了迭代查表法对系统辅助参数测量精度要求;构建了一维和准二维大地模型,验证了在飞行高度初始值满足精度的要求下,迭代查表法CDI得到的height和pitch与理论值误差分别在20%和10%范围内。
[Abstract]:Fixed-wing Airborne Time-domain electromagnetic sounding (Fixed-wing Airborne Time-domain electromagnetic) is a geophysical detection method based on the law of electromagnetic induction. It has the advantages of deep detection depth, high efficiency and low cost, so it is widely used in geological exploration. In the course of flight measurement, the flight altitude and attitude angle of receiving coil are changed due to the factors such as flight speed, aircraft attitude, air pressure, etc., which affect the observation data. In this paper, the flight altitude is studied with the aid of the project of National Natural Science Foundation "Research on the whole inversion method of fixed wing time domain aero-electromagnetic exploration", which results in the error of the results of the conductivity depth imaging (CDII) and Conductivity-Dependency Imaging. The change of pitching attitude angle of the receiving coil causes the change of electromagnetic response, but the detection system can not accurately obtain the pitching, flying altitude, In this paper, we propose a depth imaging algorithm for electrical conductivity based on iterative look-up table method. The main research contents are as follows: based on the theory of airborne electromagnetic detection, The three-component one-dimensional forward calculation method for receiving coil with arbitrary attitude angle is derived, and the influence of flight altitude on electromagnetic response is studied. In this paper, the electromagnetic response characteristics of the receiving coil under the change of yaw-yaw-yaw-angle are studied. The pitch is introduced into the conductivity depth imaging because it is difficult for the conventional aeronautical electromagnetic system to obtain the pitch information. In this paper, the CDI algorithm of B field double component (horizontal Bx, vertical Bz) lookup table with pitch is studied. According to the measured flight altitude, the corresponding flight height is found, the corresponding time track data table is obtained, and the apparent conductivity is obtained by linear interpolation. According to the diffusion formula, the imaging depth is obtained, and the conductivity depth imaging algorithm with pitch is finally realized. In the case of inaccurate altimeter indication, the flight altitude and pitch are introduced into the conductivity depth imaging simultaneously as parameters. The iterative lookup table CDI algorithm with flight altitude and pitch is studied. Bx-Bz-? -height data Table. Based on the measured BxBz electromagnetic response, the look-up table is calculated in two tables until the last iteration. The height and pitch all meet the precision requirement, then the iteration ends, and the information of apparent conductivity, flying altitude and pitching attitude are obtained. The diffusion formula is used to calculate the depth of each layer, and the imaging depth is calculated by the average apparent conductivity. Finally, an iterative lookup table conductivity depth imaging algorithm with flight altitude and pitch is implemented. The simulation results show that the iterative look-up table method is not only superior to the imaging results without considering the flight altitude and pitch angle errors, but also the simulation results show that the proposed method is better than that without considering the flight altitude and pitch angle errors. And even if you get more accurate altitude information, The depth imaging accuracy of the iterative look-up table method is also improved by about 10%. The error between the iterative lookup table method and the system measurement parameters is compared and analyzed, while the apparent conductivity is obtained at the same time as the apparent conductivity is obtained by the iterative lookup table method. In this paper, the accuracy requirement of the system aided parameter measurement by the iterative lookup table method is studied, and the one and two dimensional geodetic model is constructed, which verifies that the initial flight altitude value meets the precision requirement. The errors between the height and pitch obtained by CDI and the theoretical values are in the range of 20% and 10%, respectively.
【学位授予单位】：吉林大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：P631.326

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