Techniques for removing distortion in an AC magnetic tracker identify a characteristic frequency in the distortion environment which is then utilized to extract distortion components from the tracker receiver signals so that the corrected position and orientation can be calculated. A multiplicity of alternative techniques for determining this characteristic frequency are disclosed, several of which can be done during operation without interrupting system operation while others can be done off-line. The invention also allows the use of a tuned tracker transmitter since it does not need to operate at multiple frequencies. The invention differs from the prior art by treating an extended conductor characteristic as just another unknown. The position and orientation algorithm solves the 6 unknown coordinates of position and orientation plus the one more unknown--the extended conductor characteristic frequency. This enables the tracker to operate full time in one mode of operation without ever suspending normal operation and without additional hardware capabilities.
REFERENCE TO RELATED APPLICATION
This application claims priority to U.S. Provisional Patent Application Ser. No. 60/567,385, filed Apr. 30, 2004, the entire content of which is incorporated herein by reference.
