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The diversity of magnetic field information obtained in marine geomagnetic measurements is of great relevance to defining detailed features of the targets. In this article, a solution algorithm based on the combination of scalar and vector fields is proposed. The magnetic direction of the geomagnetic field was obtained by repeatedly applying bias fields, and the multiparameter integrated measurement is realized based on the geometric relationship of the geomagnetic parameters. To make an instrument feasible for undersea measurement, a miniaturized multiparameter magnetometer was constructed within the limited space of a pressure tank, using an Overhauser scalar sensor and a spherical coil for generating bias fields. Test platforms were built to evaluate the scalar sensor and spherical coil. Results from a nonmagnetic laboratory showed that the expanded uncertainty of the scalar sensor was 0.11 nT, whereas the magnetic field generated by the spherical coil had 97% uniformity and completely engulfed the scalar sensor. Moreover, field experiments indicated that the standard deviation of prototype instrument in magnetic direction (3 $^{\prime \prime }$ ) was close to that of declination–inclination magnetometer, whereas its standard deviation in Z -component of 0.24 nT was better than that of a commercial fluxgate magnetometer. It also had markedly better measurement stability, with no temperature drift.

The initial orientation error of a coil vector magnetometer directly determines the measurement accuracy of the magnetic field direction. The traditional initial orientation method requires auxiliary manually operated instruments. To solve this problem, we propose an electrical orientation method based on applying bias fields. To analyze quantitatively the orientation error of the proposed method, a physical model for the coil orientation indicator and measurement errors of the magnetic direction was developed that exploits measurements of the deflected field obtained after applying two oppositely directed bias fields. The simulation results show that, when the difference indicator is 0.7 nT, the measurement error of the magnetic direction is less than $9\,''$ . Moreover, when the bias field strength is greater than 30% of the geomagnetic field strength during the orientation operation, the influence of the change in strength of the bias field on the measurement error of the magnetic direction diminishes significantly. The indirect effect of the measurement error of the total-field sensor on the measurement accuracy of the magnetic direction was also analyzed. To verify this method, we designed an experimental setup and conducted a comparative experiment. The results show that as the difference indicator increases, the measurement error of the magnetic direction increases accordingly. When this indicator is adjusted to about 0.7 nT, the measurement error of the magnetic direction is less than $11.16''$ , which is in agreement with theoretical results.