Patent ID: 8228028

Claim:
A method of magnetic tracking in a tracking volume in the presence of movable magnetic-field distorter, comprising: generating a magnetic field capable of being sensed by a magnetic-field sensor when the magnetic-field sensor is located in the tracking volume; obtaining first magnetic-field data regarding the magnetic field via the magnetic-field sensor while the magnetic-field sensor is in the tracking volume; calculating, within a machine, position and orientation of the magnetic-field sensor as a function of the first magnetic-field data and a difference between a first set of data items and a second set of data items, wherein the first set of data items results from second magnetic-field data collected from the tracking volume when the movable magnetic-field distorter is present in the tracking volume, and the second set of data items results from third magnetic-field data collected from the tracking volume when the movable magnetic-field distorter is not present in the tracking volume; and outputting from the machine information that is a function of the position and orientation of the magnetic-field sensor.