Enhanced precise location

• US 8,515,689 B2
• Filed: 09/12/2008
• Issued: 08/20/2013
• Est. Priority Date: 05/18/2007
• Status: Active Grant

• Current Assignee: MetroTech Corporation Inc.
• Original Assignee: MetroTech Corporation Inc.
• Inventors: Li, Kun, Waite, Jim, Welaratna, Ruwan, Overby, Johan, Salvagione, Paolo
• Primary Examiner(s): Teixeira Moffat, Jonathan C
• Assistant Examiner(s): PARK, HYUN D
• Application Number:
  US12/209,999
• Publication Number:
  US 20090128156A1
• Time in Patent Office: 1,803 Days
• Field of Search: 702/38, 702/59, 702/33, 702/35, 702/57, 702/58, 324/67
• US Class Current: 702/38
• CPC Class Codes: G01R 29/085 for detecting presence or location of electric lines or cables fault detection G01R31/50; fault location G01R31/08
• 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 3/104 using several coupled or uncoupled coils G01V3/101 takes precedence
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G01V 3/38 Processing data, e.g. for analysis, for interpretation, for correction

Abstract

A method for determining the location of underground cables and pipes is disclosed. In some embodiments, the method includes measuring a set of electromagnetic field magnitudes and phases at a plurality of positions while traversing a target line parallelly using 3D electromagnetic coil sensors, the 3D electromagnetic coil sensors being orthogonally oriented to the target line, modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of the positions to form a set of values corresponding to a set of individual models for the target line, determining which of the set of individuals models is a best model, determining confidence information at each of the positions based on a comparison between the measured set of complex electromagnetic magnitudes and phases and the best model, and determining parameters at each of positions related to the target line from the best model.

Claims

1. A method for determining a location of underground cables and pipes, comprising:

measuring a set of complex electromagnetic field magnitudes and phases at a plurality of positions while traversing a target line in a substantially parallel direction using a plurality of 3-dimensional electromagnetic coil sensors, the plurality of 3-dimensional electromagnetic coil sensors being mounted on opposite sides of a cart frame within wheel wells of a cart-based location receiver such that there is a horizontal separation between the plurality of 3-dimensional electromagnetic coil sensors, and such that the plurality of 3-dimensional electromagnetic coil sensors are oriented substantially orthogonal to the target line;

modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of the plurality of positions to form a set of hypothesized values corresponding to a set of individual models for the target line, the modeling including using an estimation of a current attenuation at two nearest side tones to update a fit factor, the side tones defined by a carrier frequency and a modulation frequency;

determining which of the set of individuals models is a best model;

determining confidence information at each of the plurality of positions based on a comparison between the measured set of complex electromagnetic magnitudes and phases and the best model; and

determining parameters at each of the plurality of positions related to the target line from the best model.

2. The method of claim 1, wherein the parameters related to the target line include at least one estimated value chosen from a list consisting of a centerline position, depth of the target line, and a current carried in the target line.

3. The method of claim 1, wherein the set of complex electromagnetic field magnitudes includes electromagnetic field magnitudes and phases.

4. The method of claim 1, wherein modeling the set of expected complex field magnitudes includes optimizing each of the set of individual models.

5. The method of claim 4, wherein optimizing includes applying a Levenburg-Marquardt algorithm.

6. The method of claim 1, further comprising:

determining a set of precise locations corresponding with the plurality of positions.

7. The method of claim 6, further comprising:

associating the set of precise locations with the determined parameters and determined confidence information; and

exporting the set of precise locations, the determined parameters, and the confidence information to a geographic information system (GIS) mapping environment.

8. The method of claim 1, wherein determining a set of precise locations includes determining the location of the plurality of positions within a first reference frame and translating the location of the plurality of positions within the first reference frame to a second reference frame.

9. The method of claim 1, further comprising:

generating a warning if the determined confidence information meets and/or exceeds a predetermined confidence value.

10. The method of claim 1, wherein measuring a set of complex electromagnetic field magnitudes while traversing a target line comprises traversing a path substantially parallel to the target line with the cart-based location receiver.

11. A line locator, comprising:

a plurality of 3-dimensional electromagnetic coil detectors configured to measure a complex electromagnetic field magnitude and phase generated at least by a target line as the plurality of 3-dimensional electromagnetic coil detectors are moved along the target line, the plurality of 3-dimensional electromagnetic coil detectors being mounted on opposite sides of a cart frame within wheel wells of a cart-based location receiver such that there is a horizontal separation between the plurality of 3-dimensional electromagnetic coil detectors, and such that the plurality of 3-dimensional electromagnetic coil detectors are oriented substantially orthogonal to the target line;

circuitry coupled to receive signals from the plurality of 3-dimensional electromagnetic coil detectors and provide quadrature signals indicating a measured complex electromagnetic field magnitude and phase;

a position locator for indicating a precise position of the line locator;

a processor coupled to receive the complex electromagnetic field magnitude and phase and the position and calculate values related to the target line;

and a display coupled to the processor, the display indicating to a user the values related to the target line, wherein the processor includes software for performing the following;

modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of a plurality of positions determined by the position locator to form a set of hypothesized values corresponding to a set of individual models for the target line, the modeling including using an estimation of a current attenuation at two nearest side tones to update a fit factor, the side tones defined by a carrier frequency and a modulation frequency;

determining which of the set of individuals models is a best model;

determining target line location confidence information at each of the plurality of positions based on a comparison between the measured set of complex electromagnetic field magnitudes and phases and the best model;

and determining parameters at each of the plurality of positions related to the target line from the best model.

12. The line locator of claim 11, wherein the parameters related to the target line include at least one estimated value chosen from a list consisting of a centerline position, depth of the target line, and a current carried in the target line.

13. The line locator of claim 11, wherein the cart is capable of traversing a path substantially parallel to the target line.

14. The line locator of claim 13, wherein the cart includes at least one wheel.

15. The line locator of claim 14, wherein at least one of the plurality of 3-dimensional electromagnetic coil detectors is integrated within a well of the at least one wheel.

16. The line locator of claim 11, wherein the position locator further indicates locator position confidence information.

17. The line locator of claim 16, wherein the display further indicates to the user the locator position confidence information.

18. The line locator of claim 11, wherein the position locator includes an real-time kinematic GPS system.

19. The line locator of claim 11, wherein the position locator includes precise survey grade location equipment.

20. The line locator of claim 11, wherein the display further indicates to the user location information provided by the position locator.

21. The line locator of claim 11, wherein the display further indicates to the user the determined target line location confidence information.

22. The line locator of claim 11, wherein the position locator is configured to determine the position of the line locator within a line locator-based coordinate frame and within a earth-based coordinate frame.

23. The line locator of claim 22, wherein the position locator determines the precise position of the line locator by translating the determined position within the line locator-based coordinate frame into the earth-based coordinate frame.

24. A method for determining a location of underground cables and pipes, comprising:

measuring a set of complex electromagnetic field magnitudes and phases at a plurality of positions while traversing a target line in a substantially parallel direction using a plurality of 3-dimensional magnetometer sensors, the plurality of 3-dimensional magnetometer sensors being mounted on opposite sides of a cart frame within wheel wells of a cart-based location receiver such that there is a horizontal separation between the plurality of 3-dimensional magnetometer sensors, and such that the plurality of 3-dimensional magnetometer sensors are oriented substantially orthogonal to the target line;

modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of the plurality of positions to form a set of hypothesized values corresponding to a set of individual models for the target line, the modeling including using an estimation of a current attenuation at two nearest side tones to update a fit factor, the side tones defined by a carrier frequency and a modulation frequency;

determining which of the set of individuals models is a best model;

determining confidence information at each of the plurality of positions based on a comparison between the measured set of complex electromagnetic field magnitudes and phases and the best model; and

determining parameters at each of the plurality of positions related to the target line from the best model.

25. A line locator, comprising:

a plurality of 3-dimensional magnetometer detectors configured to measure a complex electromagnetic field magnitude and phase generated at least by a target line as the plurality of magnetometer detectors are moved along the target line, the plurality of 3-dimensional magnetometer detectors being mounted on opposite sides of a cart frame within wheel wells of a cart-based location receiver such that there is a horizontal separation between the plurality of 3-dimensional magnetometer detectors, and such that the plurality of 3-dimensional magnetometer detectors are oriented substantially orthogonal to the target line;

circuitry coupled to receive signals from the plurality of 3-dimensional magnetometer detectors and provide Quadrature signals indicating a measured complex electromagnetic field magnitude and phase;

a position locator for indicating a position of the line locator;

a processor coupled to receive the complex electromagnetic field magnitude and phase and the position and calculate values related to the target line; and

a display coupled to the processor, the display indicating to a user the values related to the target line, wherein the processor includes software for performing the following;

modeling a set of expected complex electromagnetic field magnitudes of a single underground conductor at each of a plurality of positions determined by the position locator to form a set of hypothesized values corresponding to a set of individual models for the target line, the modeling including using an estimation of a current attenuation at two nearest side tones to update a fit factor, the side tones defined by a carrier frequency and a modulation frequency;

determining which of the set of individuals models is a best model;

determining target line location confidence information at each of the plurality of positions based on a comparison between the measured set of complex electromagnetic field complex electromagnetic field magnitudes and phases and the best model; and

determining parameters at each of the plurality of positions related to the target line from the best model.