Patent ID: 7347280

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 a transmitter for transmitting an electromagnetic locating signal and said system including an above ground arrangement for receiving the electromagnetic locating signal for use in establishing the position of the boring tool, a method comprising: a) providing at least two above ground detectors as part of said above ground arrangement, each of which is configured for receiving said locating signal; b) locating said detectors at initial positions in said region within a dipole range of said electromagnetic locating signal transmitted from the boring tool at a first, start position; c) receiving said electromagnetic locating signal using said detectors with said boring tool first at said start position to produce a first set of electromagnetic data; d) moving the boring tool to a second position; e) receiving said electromagnetic locating signal using said detectors with said boring tool at said second position to produce a second set of electromagnetic data; and f) determining absolute positions of the detectors within said region using information including said first and second sets of electromagnetic data in a predetermined way.