Patent ID: 7071695
Filing Date: 2006-07-04
Classification: E21B,G01V

Abstract:
1. In a system in which a boring tool including a drill string is fed out in a way which moves the boring tool through the ground in a region which includes a plurality of electrically conductive in-ground lines, an apparatus for tracking the specific positional relationships between the boring tool and each of said lines, said apparatus comprising: a plurality of transmitters, each transmitter generating a magnetic field at least from an underground length of each respective line; a field strength detector carried by said boring tool for detecting a relative change in a particular characteristic of said fields, which characteristic varies for each line as a function of its specific positional relationship with the boring tool as the boring tool moves through the ground within said region; a monitoring unit for monitoring a value of at least one parameter relating to the way in which said drill string is fed out; and a processor responsive to said field strength detector and said monitoring unit for correlating the detected relative changes in said characteristic of said fields with the value of said parameter in a way which indicates certain changes in the specific positional relationship between said boring tool and each respective line without the need to establish an actual distance between the boring tool and said line.