Patent ID: 7896107

Claim:
An on-grade tracking system for use with a horizontal directional drill system having a downhole tool, the downhole tool being steerable along a desired subsurface path, the tracking system comprising: a reference line assembly adapted to generate a virtual reference line having a grade corresponding to a grade of the desired subsurface borepath, the reference line assembly comprising: a survey system adapted to determine an absolute position of the reference line assembly using signals received from a plurality of global positioning satellites; a transmitter adapted to transmit data related to the reference line and the position of the reference line assembly; a tracking receiver system comprising: a survey system adapted to determine an absolute position of the tracking receiver system using signals received from a plurality of global positioning satellites; a sensor assembly adapted to detect signals emitted from the downhole tool; a receiver assembly adapted to receive data transmitted from the reference line assembly; and a processor adapted to process the signals received to determine the position of the downhole tool relative to the reference line.