Apparatus for monitoring a positional relationship between a boring tool and an inground line

In a system in which a boring tool is moved from a drill rig through the ground by a drill string in a region which includes at least one electrically conductive in-ground line, an apparatus for monitoring a specific positional relationship between the boring tool and said line, said apparatus comprising:

• a transmitter to generate a magnetic locating field from one of either said boring tool or at least an underground length of said line;
• a receiver carried by said boring tool if said field is generated from said line, or connected to said line if said field is generated from said boring tool, to detect an intensity of said magnetic locating field to produce a signal indicative of said magnetic field intensity, said signal being responsive to the positional relationship between the boring tool and said line;
• and
• a display to produce at least one indication responsive to said signal based on the detected intensity of said magnetic locating field as generated from either one of said line or said boring tool.