Patent ID: 7373993

Claim:
A system for use with a horizontal directional drilling machine to monitor a position of a downhole tool assembly within a borehole, the system comprising: a first beacon supported by the downhole tool assembly and adapted to transmit a first signal indicative of the position of the downhole tool assembly; a second beacon supported by the downhole tool assembly and spatially separated from the first beacon, wherein the second beacon is adapted to transmit a second signal indicative of the position of the downhole tool assembly; and a receiving assembly adapted to determine the position of the downhole tool assembly disposed within the borehole using both the first signal transmitted from the first beacon and the second signal transmitted from the second beacon, the receiving assembly comprising an antenna arrangement adapted to detect the first signal transmitted from the first beacon and the second signal transmitted from the second beacon and a processor supported by the receiving assembly and adapted to process the detected signals to determine the position of the first beacon and the position of the second beacon.