Calibration of position and angular data from a magnetic tracking device

This paper describes a method for calibrating data from a magnetic tracking device. Position and orientation data were collected in a 1.6×0.8×1.4 m3 volume using a Polhemus Fastrak® in conjunction with both a long-range and standard transmitter. Position and orientation data were calibrated using a locally linear model based on the position of the measurement. After calibration, the average position and angular errors were less than 1.8 cm and 1.2° up to 1.8 m from the transmitter for the long-range transmitter. For the standard transmitter, even after calibration, errors increased sharply when the sensor was more than 1.2 m from the transmitter. Up to that distance, post-calibration errors were less than 1.2 cm and 1.2°, while up to 1.8 m they were below 5 cm and 4°. These errors could be further reduced by noise filtering. However, use of the standard transmitter is not recommended at distance greater than 1.2 m due to orientation-based effects. It was concluded that for the volume investigated, tracking devices could provide similar three-dimensional accuracy to video systems.