TRACKING POSITIONS OF PERSONNEL, VEHICLES, AND INANIMATE OBJECTS

• US 20110204895A1
• Filed: 05/03/2011
• Published: 08/25/2011
• Est. Priority Date: 10/14/2003
• Status: Active Grant

• Current Assignee: Merlin Technologies Incorporated
• Original Assignee: Merlin Technologies Incorporated
• Inventors: Mercer, John E., Zeller, Rudolf, Brune, Guenter W., Chau, Albert W.
• Granted Patent: US 8,686,731 B2
• Time in Patent Office: Days
• US Class Current: 324/326
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: G01D 5/2006 by influencing the self-induction of one or more coils G01D5/22 takes precedence
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/081 the magnetic field is produced by the objects or geological structures characterised by the method of magnetic field measurement G01R33/00
• CPC Class Codes: G01V 3/38 Processing data, e.g. for analysis, for interpretation, for correction

Abstract

A device rotates at least one static magnetic field about an axis, producing a rotating magnetic dipole field, and is movable in relation to the surface of the ground. The field is periodically sensed using a receiver to produce a receiver output responsive to the field. A positional relationship between the receiver and the device is monitored using the output. In one aspect, changing the positional relationship, by moving the device nearer to a boring tool which supports the receiver, causes an increase in accuracy of depth determination. In another aspect, determination of an actual overhead position of the boring tool, and its application, are described. Use of a plurality of measurements over at least one-half revolution of each magnet is disclosed. Establishing a surface radial direction toward a boring tool and resolution of multi-valued parameters is described. Calibration techniques, as well as a three transmitter configuration are also described.

Claims

1. In a system for use in locating a receiver at a receiving position, a method comprising:

providing at least a first, a second and a third transmitter that are spaced apart such that the transmitters produce first, second and third rotating dipole fields, respectively, each of which fields is distinguishable with respect to the others;

establishing a location of each of said transmitters;

receiving the first, second, and third rotating dipole fields at said receiving position to produce a first, a second and a third received signal;

using the first, second and third received signals to determine a first, a second and a third radial distance, respectively, from said receiving position to each of the transmitters; and

thereafter, using the first, second and third radial distances, in conjunction with the location of each transmitter, to determine at least two potential locations of said receiving position in relation to the transmitters.

2. The method of claim 1 wherein receiving establishes only a total signal strength, in three dimensions, for each of the first, second and third received signals.

3. The method of claim 2 wherein the total signal strength received for each transmitter exhibits a given characteristic responsive to each of the first, second and third rotating dipole fields and said given characteristic is established for each transmitter by monitoring each of the first, second and third received signals during its rotation for use in determining said first, second and third radial distances.

4. The method of claim 3 wherein receiving includes monitoring each of the first, the second and the third rotating dipole fields over at least one-half of a revolution to produce the first, the second and the third received signals.

5. The method of claim 4 wherein said given characteristic is a minimum total signal strength.

6. The method of claim 5 wherein said radial distances for each of the transmitters are determined using

R_i=b_mini⁻

1/3

where i is an identification number of the transmitter and b_mini is the minimum total signal strength for each transmitter.

7. The method of claim 1 wherein said first, second and third rotating dipole fields rotate at different first, second and third rotational frequencies.

8. The method of claim 1 including using a first, a second and a third magnet to produce the first, second and third rotating dipole fields, respectively.

9. The method of claim 1 including producing the first, second and third rotating dipole fields in a time division multiplexed manner.

10. The method of claim 1 including selecting one of the two potential locations as an actual location of said receiving position based, at least in part, on a last-known position of the detector.

11. The method of claim 1 wherein said receiver forms part of a boring tool that is moved underground by a drill string having a length and including selecting one of the two potential locations as an actual location of the receiving position based, at least in part, on said drill string length.

12. The method of claim 11 wherein said boring tool moves in an orientation and including detecting said orientation of the boring tool to provide one or more orientation parameters and using the orientation parameters with said drill string length to select one of the two potential locations as an actual location of the receiving position.