Calibration of Magnetic Field Sensors with two mass-market GNSS receivers

Global Navigation Satellite System (GNSS) signals, inertial measurements (angular rates, accelerations) and magnetometer measurements complement each other for position determination: GNSS provides a precise and drift-free position solution but is susceptible to signal outages. Inertial measurements are continuously available and of higher rate but suffer from integration drifts. Magnetic field measurements provide an instantaneous orientation in static conditions but are affected by both static and dynamic disturbances. In this paper, we provide a calibration method for magnetometers, which determines the biases and misalignment errors of the magnetometer as well as the magnetic flux including static disturbances. The method uses the iterative Gauss-Newton method and precise attitude information (heading, pitch) obtained from two low-cost GPS receivers. The attitude determination requires a tree search of the carrier phase integer ambiguities using a priori information on the distance between both GPS receivers. We also verified the proposed method with kinematic measurements from the CMPS10 sensor. We observe an accuracy of a few degrees for the unfiltered heading and a heading offset of less than 10 degrees in 99.5% of all measurement epochs.