A real-time calibration method of magnetometer array’s misalignment errors with ac modulated three-axis coil

•An ac modulated three-axis coil calibrates misalignment errors of magnetometer array.•Varied currents of coils eliminate the necessity of non-magnetic rotation platform.•Ac responses of magnetometers are demodulated robustly with magnetic interferences.•Established theoretical model eliminates the necessity of total field magnetometer.•Errors of measured magnetic field gradient and localization decrease after the calibration. The misalignment errors of magnetometer array are vulnerable to vibrations, which deteriorates the magnetic anomaly detection performance severely and brings strong demands for real-time calibrations. We propose a real-time calibration method of magnetometer array’s misalignment errors, which utilizes a standard three-axis coil to generate an alternating current magnetic field with varied magnitudes and directions. Then the misalignment errors are calibrated by minimizing the difference between experimentally calibrated magnetic fields of magnetometers and theoretically calculated magnetic fields of coils with the Levenberg–Marquardt algorithm and Biot-Savart’s law. It does not require the expensive high-precision non-magnetic rotation platform, homogenous magnetic environment and additional scalar magnetometer compared to the conventional methods, which facilitates the real-time calibration with ambient magnetic fluctuations. The investigations demonstrate that the X-axis magnetic field gradient is decreased from 3665 nT to 68 nT and localization error is reduced from 1.6 m to 0.11 m with the proposed calibration method.