A Calibration Method for Misalignment Error in Geomagnetic Navigation Systems Under Small-Range Attitudes

The geomagnetic navigation has been widely applied in various fields, with one of its pivotal challenges being the calibration of misalignment error between the triaxial magnetometer and inertial navigation systems (INSs). Traditional methods are not suitable for scenarios such as submarines and warships, where it is inconvenient to change large-range attitudes. Therefore, a novel misalignment error model is developed in this article. Then, based on this model, an objective function containing deviation angles between the magnetometer and INS is constructed. Finally, the deviation angles are solved through optimization algorithms, and the calibrated azimuth can be obtained. Moreover, the issue of unknown actual geomagnetic fields is resolved using the differential approach during parameter estimation. The method proposed in this article neither require data collection under large-range or strictly controlled attitudes nor does it necessitate auxiliary equipment. Both simulation and experimental results confirm the validity and feasibility of the method. The experimental results show that the maximum error in azimuth is approximately 0.6° and the mean absolute deviation (MAD) of the horizontal and vertical components of the geomagnetic field are reduced from 1083.5639 and 933.2666 to 120.7572 and 127.9542 nT, respectively. The results indicate that the method can effectively calibrate misalignment error under small-range attitudes, thereby achieving high-precision navigation.