A system, for use with a cannula insertable into human or animal tissue, for measuring relative motion during a surgical procedure includes a probe having a probe tip insertable into the cannula, and means for determining relative motion between the cannula and the probe tip. According to an exemplary embodiment of the present invention, one or more auto-correlation values of a preamble constituting a signal that is received from a base station are calculated. Records within a mapping table are arranged in multiple levels which may be logically ordered by time. That conventional assembly can be deleterious, therefore, applicant has altered the pivot axis of the swing-house assembly.