Optimizing and validating an electromagnetic tracker in a human performance laboratory

Measurement errors have previously been observed using electromagnetic motion trackers in applied laboratories. The aims of this study were to optimize the layout of a human performance laboratory for assessing ergometer rowing technique, and to assess the precision and repeatability of measured rotations and trajectories using the Flock of Birds electromagnetic tracker. Four experiments investigated system performance over a large experimental volume: optimization of laboratory space, repeatability of laboratory layout, precision of measured rotations, and repeatability of measured displacements. Measurement accuracy was influenced by varying the global position of the system transmitter; results suggested a correlation with increasing distance between the electromagnetic source and equivalent sensors. Bringing the transmitter or sensors into closer proximity of metallic items may be another source of measurement error. An optimal location for the transmitter was identified, into which the transmitter was repositioned with good repeatability. Measurements were not negatively affected by the presence of a rowing ergometer in the experimental volume. Induced sensor rotations were reconstructed with high precision, and the system calculated small changes in sensor displacement with good repeatability. The system is a suitable technology for measuring the trajectory and rotation of moving body segments in applied human movement laboratories.