Method and apparatus for establishing a borehole parallel to an existing underground cable

摘要

The position of a boring head (16) during boring operation in the vicinity of an existing utility conveyance (22) that radiates a locating signal can be determined by establishing the ratio of the strength of the locating signal of the cable induced in the boring head to the strength of the locating signal on the conveyance. Should the ratio exceed a prescribed value, indicating that the boring head is too close to the existing conveyance, then an alert is generated. Advantageously, the position of the boring head during a boring operation may be controlled in feed-back loop fashion in accordance with the ratio to maintain the boring head substantially parallel to the existing conveyance.