Path mapping in underground boring tool applications

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 for use in establishing the position of the boring tool, a method comprising the steps of

• a) providing an above ground detector as part of said arrangement which is configured for receiving said locating signal;
• b) locating the detector at an initial position 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 detector 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 detector with said boring tool at said second position to produce a second set of electromagnetic data;
• and
• f) determining absolute positions of the detector and the boring tool within said region using certain information including said first and second sets of electromagnetic data in a predetermined way.