A method for determining the 3D location and orientation of a fiducial reference comprises disposing the fiducial reference so as to render a part of the fiducial reference observable by a tracker obtaining from the tracker scan data of the part of the fiducial reference that is observable by the tracker obtaining predetermined geometric information about location points on the fiducial reference, the geometric information containing three-dimensional coordinates of the location points relative to the structure of the fiducial reference identifying within the scan data at least three location points having coordinates in the predetermined geometric information and determining from the scan data and the coordinates of the three identified location points in the predetermined geometric information the 3D location and orientation of the fiducial reference.
