Integrated Calibration of Strap-Down Geomagnetic Vector Measurement System

Strap-down geomagnetic vector measurement system usually consists of three-axis magnetometer and inertial units, which is an effective device for measuring geomagnetic vector. However, its measurement accuracy is limited by disturbance of ferromagnetic material, measurement error of magnetometer and error caused by misalignment. Therefore, an integrated calibration method for strap-down geomagnetic vector measurement system is proposed. Firstly, the integrated error model is established, and a system with linear equations constraint is constructed by the measurements of inertial units, three-axis magnetometer and proton magnetometer; secondly, calibration parameters can be estimated by two-step least squares estimation (LSE); finally, geomagnetic vector measurement can be calibrated with these parameters in real time. Simulation results show that the relative errors between estimation and true parameters are less than 3%. Experimental results demonstrate that the errors of strap-down geomagnetic vector measurement system are suppressed effectively after integrated calibration, where North, Vertical and East component measurement errors are reduced from 809.2 nT, 300.0 nT, 776.8 nT to 14.8 nT (1.83% of uncalibrated value), 11.9 nT (3.97%), 32.5 nT (4.18%) respectively, and measurement accuracy of declination and inclination are achieved to 0.1°. Furthermore, the calibration error and time are least compared with traditional methods.