Patent ID: 7021403

Claim:
In a system for tracking the position of a boring tool in the ground as the boring tool moves along an underground path which lies within a region, said boring tool including means for transmitting an electromagnetic locating signal and said system including an above ground arrangement for receiving the electromagnetic locating signal, an improvement comprising: providing at least two above ground detectors, each of which is configured for receiving said locating signal; locating said detectors at initial positions in said region within range of said electromagnetic locating signal transmitted from the boring tool at its initial position, said detectors including tilt sensors for measuring the tilt angles of each detector such that the tilt angles of each detector form part of said certain information; providing transmitter means forming one part of at least a first one of said detectors for transmitting a relative locating signal to other detectors in a setup mode; receiving said relative locating signal using a second one of said detectors in said setup mode; determining the position of the second detector relative to the first detector based on the received relative locating signal receiving said electromagnetic locating signal in a predetermined way using said first and second detectors to produce electromagnetic data; and establishing initial absolute positions of said detectors and said boring tool within said region using certain information including the electromagnetic data and said tilt angles in conjunction with the relative position established between the detectors moving one of said detectors to a new, unknown location while the other detector remains in its initial, known position; and transmitting said relative locating signal to establish the new location of the moved detector relative to the other detector so as to also establish the absolute position of the moved detector in said region.