Motion noise reduction in drone magnetometry using a dead-zone-free total-field magnetometer system

Abstract

In recent years, drone magnetometry has gained popularity in geophysics mainly due to its time efficiency and low cost in acquiring magnetic data over large areas. In drone magnetometry, a total-field magnetometer is usually suspended from a drone to avoid magnetic interference from the drone. Therefore, the magnetometer can experience uncontrolled yaw-pitch-roll rotations during flight. As a result, both the dead zone and the heading effects of total-field magnetometers pose significant challenges in drone magnetometry. The former causes the magnetic field readings to drop out, while the latter leads to significant motion-induced magnetic noise. We study a commercially available magnetometer system for drone magnetometry. This system eliminates the dead-zone effect by having two orthogonally oriented sensors operating simultaneously. The combined single-output magnetometer is intrinsically dead zone free, but it still has the heading effect. We investigate a compensation method to mitigate the heading effect. Heading-effect calibration data are first collected and then applied to magnetic survey data. Our study shows that the heading-induced motion noise can be suppressed by an order of magnitude through this method. Peak-to-peak noise of 0.2 nT is demonstrated for survey data at a 20 Hz sample rate. This advance overcomes a fundamental challenge in drone magnetometry and could make drone magnetometry the technique of choice for future magnetic surveys.