Method For Guiding A Downhole Tool Assembly Using An Above-Ground Receiver System

A tracking system for tracking movement of a downhole tool, the downhole tool comprising a transmitter, the system comprising:

• a remote unit comprising a first receiver assembly, the assembly comprising:
• a tri-axial antenna to detect a magnetic field in three dimensions and to generate a first antenna signal indicative of the detected field;
• and
• a radio antenna to transmit the first antenna signal;
• a second receiver assembly comprising:
• a tri-axial antenna to detect the magnetic field in three dimensions and to generate a second antenna signal indicative of the detected field;
• a radio antenna to receive the first antenna signal from the first receiver assembly;
• and
• a processor to receive the first and second antenna signals and determine a location of the downhole tool using the first and second antenna signals.

A horizontal directional drilling system comprising:

• a rotary drive;
• a drill string operatively connected to the rotary drive at a first end;
• a downhole tool connected to a second end of the drill string, the downhole tool comprises a magnetic field transmitter;
• a first receiver assembly comprising a tri-axial antenna used to detect the magnetic field and generate a first antenna signal;
• a second receiver assembly comprising a tri-axial antenna used to detect the magnetic field and generate a second antenna signal;
• and
• a processor to receive and process the first and second antenna signals to determine a location of the downhole tool.