Precise location and orientation of a concealed dipole transmitter

A sonde locator comprising:

• a plurality of electromagnetic coil detectors configured to measure the electromagnetic field magnitude and phase generated by least one dipole transmitter axis of a target sonde, the plurality of electromagnetic coil sensors being at arbitrary orientation to the target sonde;
• circuitry coupled to receive signals from the plurality of electromagnetic coil sensors and provide quadrature signals indicating a set of measured complex electromagnetic field strengths related to each electromagnetic coil sensor at the receiver and at least one transmitter dipole direction;
• a position locator for indicating a precise position of the sonde locator;
• a processor coupled to receive the complex electromagnetic field strength and phase and the position and calculate parameter values related to the target sonde;
• and
• a display coupled to the processor, the display indicating to a user the values related to the target sonde, wherein
• the processor includes software for performing the following:
• measuring a set of complex electromagnetic field magnitude and phase strengths at one or more positions determined by the position locator while traversing a target sonde path at any angle using one or more of the electromagnetic coil sensors;
• modeling a set of expected complex electromagnetic strengths of a hypothetical sonde at each of the one or more positions determined by the position locator for one or more of the electromagnetic coil sensors, the set of expected electromagnetic field values corresponding to a model for the target sonde;
• and
• estimating parameters related to the target sonde based on the residual error between the measured set of complex electromagnetic field values and the modeled set of expected complex electromagnetic field strengths, wherein a final estimated parameter set is determined after the residual error has converged to a minimum tolerance.