Importance

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Abstract

The apparatus and method of the invention relates to the formation of ducts or passageways, referred to as ducts underground by using existing lengths of plant such as pipes, cables or wires, or a length of plant laid in predetermined position as a guidance or reference for the drill head used to form the duct or passageway as it passes through the ground. The plant is used to generate an electromagnetic field which is sensed by at least one electromagnetic field sensor mounted in the drill head, said sensor rotated to allow comparison of signals and the distance of the drill head from the plant to be calculated. Other sensors can also be provided to determine other positional characteristics of the drill head with respect to the plant. This allows the duct to be formed with the avoidance of potentially hazardous plant and/or along a path which is determined with reference to the plant. The apparatus can also be used as a guidance means without the drill to pass along existing passageways and indicate the path of the same using the same operating procedure.

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First Claim