Patent ID: 8249689

Claim:
A tracking system, comprising: an array of electromagnetic receivers that sense at least one characteristic of a magnetic field, the array of electromagnetic sensors comprising three co-planar electromagnetic sensors and a fourth electromagnetic sensor that is not co-planar with the three co-planar sensors, wherein the three co-planar electromagnetic sensors and the fourth electromagnetic sensor are each located at a vertex of a tetrahedron, and the three co-planar electromagnetic sensors and the fourth electromagnetic sensor each comprise industry-standard coil architecture (ISCA) type coils; and a processor that receives a signal indicative of the at least one characteristic from the array of electromagnetic receivers and processes the signal to resolve a position of an electromagnetic field generator that generated the magnetic field relative to the array of electromagnetic receivers, wherein processing the at least one signal comprises determining an average magnetic field gradient at the center of the array of electromagnetic receivers, and wherein the average magnetic field gradient is processed to resolve the position of the electromagnetic field generator relative to the array of electromagnetic receivers.