Precise location and orientation of a concealed dipole transmitter

• US 20100141261A1
• Filed: 12/05/2008
• Published: 06/10/2010
• Est. Priority Date: 12/05/2008
• Status: Active Grant

• Current Assignee: MetroTech Corporation Inc.
• Original Assignee: MetroTech Corporation Inc.
• Inventors: Li, Kun, Waite, James W., Overby, Johan, Gargov, Dimitar
• Granted Patent: US 8,188,745 B2
• Time in Patent Office: Days
• US Class Current: 324/329
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005

Abstract

A method for determining the location of an underground sonde transmitter is disclosed. In some embodiments, the method includes measuring a set of complex electromagnetic field magnitude and phase strengths at one or more of positions while traversing a target sonde path at any angle using one or more electromagnetic coil sensors, modeling a set of expected complex electromagnetic strengths of a hypothetical sonde at the one or more of positions 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.

Claims

1. A method for determining the location and orientation of a sonde, the method comprising:

measuring a set of complex electromagnetic field magnitude and phase strengths at one or more positions while traversing a target sonde path at any angle using one or more electromagnetic coil sensors;

modeling a set of expected complex electromagnetic strengths of a hypothetical sonde at each of the one or more positions 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.

2. The method of claim 1, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors.

3. The method of claim 1, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors; and

an off-axis yaw angle of the target sonde from a reference direction relative to one or more of the electromagnetic coil sensors.

4. The method of claim 1, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors;

an off-axis yaw angle of the target sonde from a reference direction relative to one or more of the electromagnetic coil sensors; and

a pitch angle of the target sonde relative to one or more of the electromagnetic coil sensors.

5. The method of claim 1, wherein the target sonde comprises a multi-axis dipole transmitter capable of transmitting at a unique operating frequency per axis.

6. The method of claim 5, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors;

an off-axis yaw angle of the target sonde from a reference direction relative to one or more of the electromagnetic coil sensors;

a pitch angle of the target sonde relative to one or more of the electromagnetic coil sensors; and

a roll angle of the target sonde about its longitudinal axis.

7. The method of claim 1, wherein modeling the set of expected complex field strengths includes optimizing each of the each of the sets of individual models related to each of the one or more electromagnetic coil sensors at the receiver and each of one or more target sonde target transmitter directions.

8. The method of claim 7, wherein optimizing includes applying a Levenburg-Marquardt algorithm.

9. The method of claim 1, further comprising determining a confidence bound for each of the parameters after the residual error has converged to a minimum tolerance.

10. A multi-axis dipole transmitter apparatus including a plurality of transmission axes, each transmission axis comprising:

a dipole antenna arranged so that its dipole axis is unique to the other transmission axes configured inside a cylindrical enclosure; and

a multi-frequency generation circuit capable of generating an output transmission frequency unique to the axis configured inside the cylindrical enclosure.

11. The multi-axis dipole transmitter apparatus of claim 10, wherein the dipole antenna of each transmission axis comprises a current transformer including a primary winding, a ferrite torroid, and a low resistance secondary loop.

12. The dipole transmitter of claim 10, where the output transmission frequency is a modulated carrier signal that includes an embedded phase reference.

13. The multi-axis dipole transmitter of claim 10, where the number of transmission axes is two and each axis is driven by a unique frequency, the axes are orthogonally arranged with respect to each other, and a third transmission frequency drives both axes.

14. The multi-axis dipole transmitter of claim 13, where an excitation voltage representing the third frequency is combined, separately, with a first frequency in the current transformer included in a first axis of the plurality of transmission axes and with a second frequency in the current transformer included in a second axis of the plurality of transmission axes, wherein the transmitter is configured such that an electromagnetic field generated based on the third frequency has an effective axis along a longitudinal axis of the transmitter.

15. 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.

16. The sonde locator of claim 15, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors.

17. The sonde locator of claim 15, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative one or more of the electromagnetic coil sensors; and

an off-axis yaw angle of the target sonde from a reference direction relative to one or more of the electromagnetic coil sensors.

18. The sonde locator of claim 15, where the sonde locator is integrated into a cart capable of traversing a path at arbitrary angle relative to the orientation of the target sonde.

19. The sonde locator of claim 18, wherein the cart includes at least one wheel.

20. The sonde locator of claim 19, wherein at least one of the one or more electromagnetic coil sensors is integrated within a well of the at least one wheel.

21. The sonde locator of claim 15, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors;

an off-axis yaw angle of the target sonde from a reference direction relative to one or more of the electromagnetic coil sensors; and

a pitch angle of the target sonde relative to one or more of the electromagnetic coil sensors.

22. The sonde locator of claim 15, wherein the position locator includes a real-time kinematic GPS system.

23. The sonde locator of claim 15, wherein the sonde is a multi-axis dipole transmitter operating at a unique frequency per axis.

24. The sonde locator of claim 23, wherein the parameters related to the target sonde include at least:

a 3-dimensional position of the target sonde relative to one or more of the electromagnetic coil sensors;

an off-axis yaw angle of the target sonde from a reference direction relative to one or more of the electromagnetic coil sensors;

a pitch angle of the target sonde relative to one or more of the electromagnetic coil sensors; and

a roll angle of the target sonde about its longitudinal axis.

25. The sonde locator of claim 15, wherein the display further indicates to the user location information provided by the position locator.

26. The sonde locator of claim 15, wherein the display further indicates to the user the determined parameters and measurement confidence information.

27. The sonde locator of claim 15, wherein the processor includes software for further performing a determination of a confidence bound for each of the parameters after the residual error has converged to a minimum tolerance.

28. The sonde locator of claim 15, wherein the position locator is configured to determine the position of the sonde locator within an earth-based coordinate frame.

29. The sonde locator of claim 28, wherein the position locator determines the precise position of the target sonde by translating the determined position within the sonde locator-based coordinate frame into the earth-based coordinate frame.

30. A method for tracking the location and orientation of a dipole transmitter target sonde between two arbitrary points comprising a known beginning point and a known ending point, comprising:

computing a first optimal path for the target sonde between the beginning point and the ending point;

measuring a set of complex electromagnetic field magnitude and phase values at one of a plurality of incremental positions of target sonde following the optimal path using a plurality of electromagnetic coil sensors;

generating a set of expected complex electromagnetic field values of a hypothetical sonde at the one incremental position based on an extended Kalman filter for each of the electromagnetic coil sensors, the set of expected complex electromagnetic field values corresponding to a model for the target sonde; and

estimating a revised optimal path of the target sonde from the one incremental position to the ending point based on the residual error between the measured field values and the expected field values.

31. The method of claim 30, wherein a receiver utilized to measure the set of complex electromagnetic field values is fixed aboveground and the target sonde is in motion underground.

32. The method of claim 30, wherein a receiver utilized to measure the set of complex electromagnetic field values is in motion aboveground and the target sonde is fixed underground.

33. The method of claim 30, wherein a receiver utilized to measure the set of complex electromagnetic field values is in motion above ground, the target sonde is in motion underground, and the motion of the receiver is tracked across the ground by a position system.

34. The method of claim 33, wherein the motion of receiver is decoupled from the motion of the target sonde.