Improved Component Compensation of Magnetic Interferential Field for Geomagnetic Vector Measurement System Using 3-D Helmholtz Coil

Owing to the ferromagnetism interferential field, the component compensation of magnetic field distortion is vital for a geomagnetic field vector measurement system. However, magnetic interferences, such as eddy-current field, have not been considered in the traditional component compensation methods due to the reference component magnetic field, and its variation with time is difficult to obtain. In this article, a new compensation method using a 3-D Helmholtz coil is proposed, in which the eddy-current field related to the reference component magnetic field and its variation with time are integrated into a compensation model. In addition, the rotation equipment is not necessarily needed to construct the equations of an error model, and the 3-D Helmholtz coil is used to generate any required compensation data to estimate the compensation model error parameters, which makes the compensation procedure more simple and convenient. In order to verify the effectiveness of the proposed method, the experiment is conducted, and the results demonstrate that the proposed method contributes to the accuracy improvement of the geomagnetic vector measurement system. After compensation, the rms errors of North, East, Vertical components, and total intensity are reduced from 3648.3, 2986.2, 3496.2, and 3894.1 to 38.72, 29.58, 35.42, and 42.82 nT, respectively.

I. Introduction

Geomagnetic field vector information (North, East, and Vertical component) is of great importance in many applications, such as geological survey, autonomous underwater vehicles (AUVs) navigation, and unexploded ordnance detection (UXO) [1], [2], [3]. The geomagnetic vector measurement system mainly consists of a three-axis fluxgate magnetometer and inertial units. The three-axis magnetometer gives the projection of geomagnetic field on a magnetometer coordinate, and inertial units provide the attitude of magnetometer; with attitude information provided by the inertial units, such vector is transformed into the geographic coordinate system [4], [5].