Patent ID: 6882154

Claim:
In a system in which a boring tool is connected to a drill string having a length which 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 arrangement for tracking a plurality of positional relationships between the boring tool and each of said lines, a configuration comprising: a transmitter arrangement for generating a mmgnetic field from said boring tool; a plurality of detector arrangements, each of which is connected with a respective one of said lines, for detecting a relative change in a characteristic of said field, which characteristic varies as a function of said specific positional relationship between said boring tool and each of said lines as the boring tool moves through the ground within said region; a monitoring arrangement for monitoring a value of at least one parameter relating to the way in which said drill string is fed out; and a processing arrangement cooperating with said plurality of detector arrangements for correlating the detected relative changes in said characteristic with the value of said one parameter in a way which indicates certain changes in the positional relationship between said boring tool and each respective line without the need to establish an actual distance between the boring tool and each line.