de Amorim, J. and Martins-Filho, L., "Implementation and Testing of Magnetometer Calibration Algorithms for Autonomous Navigation Systems Application," SAE Technical Paper 2015-36-0174, 2015, doi:10.4271/2015-36-0174.
The attitude of autonomous marine, land, air or space vehicles can be determined from the state estimation by means of mathematical tools such as Extended Kalman filter. In the process of calculation of this value, three-axis inertial and non-inertial sensors are used. From the knowledge of the orientation of the main axis, it is implemented the automatic control of the vehicle.The solid-state magnetometer is a non-inertial sensor with three axes that provides both the direction and the magnitude of the magnetic field vector which it is being submitted. However, measurements of the Earth's magnetic field vector, obtained using the three-axis magnetometer, are not accurate. In the vehicle itself, the presence of ferrous materials creates disturbances in the Earth's magnetic field, distorting the measured field. The accuracy of the magnetometer can be improved by means of various calibration methods, which, in summary, calculate the vector components of the bias, the systematic error, which can be modeled as a magnetic field that overlaps and distorts the actual terrestrial magnetic field. More than 90% of the measured geomagnetic field is generated in the earth's outer core and can be described by mathematical models that serve as reference to some of the magnetometer calibration algorithms.