Error-separation method for the calibration of magnetic compass

Magnetic compass is widely used in the navigation system by measuring the orientation of the earth's magnetic field and must be calibrated before used to eliminate the errors caused by the bias, misalignment, inconsistence in sensitivity, etc. In this paper, the fully digital magnetic compass was developed by using magnetic-induced magnetometers and MEMS accelerometers and the error-separation method based on a non-magnetic three-axis rotation platform was presented to calibrate the magnetic compass. The parameters about misalignment and non-orthogonality of the sensor axes and the response curve of the sensor's output signals to earth magnetic fields were obtained. Furtherly, the sensitivity of magnetometers and the bias from the offset and hard-magnetic interference were estimated according to the response curve. The independent effect of non-orthogonality and misalignment, bias and inconsistence in sensitivity on the heading error can be evaluated with the error-separation method, respectively. After calibration, the maximum heading error of magnetic compass was about 0.4° when both pitch angle and roll angle were in the range from −60° to 60°, indicating the error-separation method is effective and efficient to calibrate magnetic compasses.