Autocalibration of a magnetic compass without heading reference

The electric compass is a useful tool to measure the heading, but it has measurement errors that are sensitive to the external interferences. In this paper, a new method based on improved ellipse fitting model is proposed to calibrate the interference error without heading reference. A process is developed with estimating accurate parameters base on least-squares algorithm. The max deviation angle measured by the compass is 2.1° during the experiment. It is much below the compass initial accuracy and it shows that this method can be used as a reference.