Patent ID: 6859162

Claim:
In a system for locating electrically conductive underground objects by the reception of radio waves created by current flow through the underground object, a method of removing ambiguity of direction of current flow in the object comprising the steps of: a) creating an RF signal, f(t), including a modulation signal and having an average value of zero and such that f ( t )≠ f ( t=K ) where K in an arbitrarily selected number, b) applying the RF signal to the underground object to cause a current to flow through the underground object, c) detecting a received RF signal including the modulation signal emitted from the object, and d) decoding the received RF signal to recover the modulation signal and comparing relative phase of the applied RF signal to the modulation signal and relative phase of the received RF signal and the recovered modulation signal to ascertain direction of current flow through the object.