Patent ID: 7080698

Claim:
A method for tracking the position and certain orientation parameters of a transmitter in the ground as the transmitter moves along a path which lies within a particular coordinate system, said method comprising: using the transmitter to transmit an electromagnetic field; providing one or more detectors, each having an electromagnetic field receiving antenna assembly including at least one antenna, and positioning each detector at a fixed position and at a particular orientation within said coordinate system, and determining the position and particular orientation within said coordinate system of the antenna assembly that is associated with each detector provided; at least periodically transmitting said electromagnetic field from said transmitter when the transmitter is at certain positions on said path; when the transmitter is at one point on said path, establishing its position and said certain orientation parameters of the transmitter within the coordinate system; moving said transmitter along said path, which includes said one point, and at least a subsequent second point; after the transmitter moves a distance along said path from said one point to said second point, measuring at least one component of the intensity of said electromagnetic field using said detector or detectors; and determining, at least to an approximation, the position and orientation of the transmitter at said second point within the coordinate system using as a first input the electromagnetic field intensity measurement or measurements taken by said one or more detectors when the transmitter is at said second point.