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System for detecting the location and orientation of a temporarily inaccessible object

  • US 5,014,008 A
  • Filed: 02/27/1990
  • Issued: 05/07/1991
  • Est. Priority Date: 06/28/1988
  • Status: Expired due to Term
First Claim
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1. A system for detecting the location and orientation of a temporarily inaccessible object, such as a boring mole or a locator unit in an underground pipeline, comprising providing that object with first means (1) for generating a rotating electromagnetic field, and detecting the presence of the object from the electromagnetic radiation by coil aerial means (6) at a receiver, characterised in that the object is further provided with second means (7) for generating a further electromagnetic field of frequency and phase related to the rotary field, and in that the receiver is further provided with means (9) for deriving from the further field a reference frequency and with means (13) for relating to that reference frequency the signal from the rotating field as received by an aerial (6) of the coil aerial means having a set orientation, the phase difference being indicative of the departure (α

  • ) of the first generating means, and hence of said object, from a base orientation.

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