A Novel Coil-Based Overhauser Vector Magnetometer for the Automatic Measurement of Absolute Geomagnetic Total Field and Directions

The absolute measurement of geomagnetic parameters can be applied directly not only in magnetic navigation and target detection but also in the correction of relative measurement. The absolute geomagnetic measurement generally adopts a combined measurement mode. Owing to differences in the principles of different magnetometers, it is difficult to comprehensively apply absolute data. To address this problem, we propose a novel automatic measurement model for the absolute geomagnetic total field and directions. Gearing toward field mobile measurement, we developed an integrated vector magnetometer using an improved Overhauser total-field sensor and a miniaturized spherical magnetic field generator. Component test results obtained for an artificial magnetic field generator show that the expanded uncertainty of Overhauser sensor with reduced dimensions was still below 0.10 nT, and the magnetic gradient formed by the applied bias fields had no negative effect on the performance of Overhauser sensor. In overall tests conducted in geomagnetic observatories, between the proposed magnetometer and a standard manually operated declination-inclination magnetometer, the differences of inclination and declination were only 14.40" and 12.96", respectively. The noises of total field, horizontal component, and declination measured by the proposed magnetometer were 0.02 nT, 0.08 nT, and 0.47", respectively, which are much lower than those of a state-of-the-art standard variometer. The proposed magnetometer is expected to be applied to unattended monitoring of geomagnetic field for the geomagnetic navigation, exploration of weak magnetic anomaly produced by the deep mineral resources, automatic remote detection of moving magnetic targets, fine-scale characterization of the plate tectonics, etc.