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 x 0.8 x 1.4m (3) volume using a Polhemus Fastrak(R) in conjunction with both a long-rang e and standard transmitter. Position and orientation data were calibrated u sing 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 degrees up to 1.8 m from the transmitter for the long-range transm itter. For the standard transmitter, even after calibration, errors increas ed 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 degree s, while up to l.g m they were below 5 cm and 4 degrees. These errors could be further reduced by noise filtering. However, use of the standard transm itter 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. (C) 2000 Elsevier Science Ltd. All rights reserved.