Method for determining accurately coordinates of a GPR antenna relative to a fixed reference

• US 6,670,906 B1
• Filed: 11/20/2001
• Issued: 12/30/2003
• Est. Priority Date: 11/20/2000
• Status: Expired due to Fees

• Current Assignee: Geophysical Survey Systems, Inc.
• Original Assignee: Geophysical Survey Systems, Inc.
• Inventors: Schutz, Alan E., Roberts, Roger
• Primary Examiner(s): Lobo, Ian J.
• Application Number:
  US09/988,570
• Time in Patent Office: 770 Days
• Field of Search: 342/22, 342/453, 342/450, 367/907
• US Class Current: 342/22
• CPC Class Codes: G01S 13/885 for ground probing prospecting or detecting using electromagnetic waves G01V3/12
• CPC Class Codes: G01S 13/89 for mapping or imaging
• CPC Class Codes: G01S 5/0284 Relative positioning
• CPC Class Codes: G01S 5/16 using electromagnetic waves other than radio waves
• CPC Class Codes: H01Q 21/28 Combinations of substantially independent non-interacting antenna units or systems multiple beam H01Q25/00
• CPC Class Codes: H01Q 9/285 Planar dipole H01Q9/065 takes precedence; patch antenna H01Q9/0407
• CPC Class Codes: H01Q 9/40 Element having extended radiating surface
• CPC Class Codes: Y10S 367/907 Coordinate determination

Abstract

A method and apparatus for determining accurately a coordinate of a transmitting/receiving antenna pair relative to a predetermined reference position. The method includes placing a transmitting antenna in proximity to a reflective strip, transmitting a first signal from the transmitting antenna and detecting a reflection of the first signal received from the reflective strip at the receiving antenna located at a fixed distance from the transmitting antenna. The method further comprises determining a coordinate of the antennas relative to the reflective strip based on a parameter of the reflection. The method may further comprise detecting a second signal received by the receiving antenna from a conductive strip located proximate to the reflective strip, and determining a second coordinate of the antennas based at least on a time difference between transmitting the first signal from the transmitting antenna and receiving the second signal at the receiving antenna.

Claims

1. A method for determining a coordinate of an antenna relative to a predetermined reference, the method comprising acts of:

placing transmitting and receiving antennas in proximity to a reflective strip;

transmitting a first signal from the transmitting antenna;

detecting a reflection of the first signal received by the receiving antenna from the reflective strip;

determining a coordinate of at least one of the receiving antenna and the transmitting antenna relative to the reflective strip based on a parameter of the reflection.

2. The method as claimed in claim 1, wherein placing transmitting and receiving antennas in proximity to a reflective strip includes placing a single antenna that performs both a transmitting and receiving function in proximity to the reflective strip.

3. The method as claimed in claim 1, further comprising acts of:

detecting a second signal received by the receiving antenna from a conductive strip located proximate to the reflective strip;

determining a second coordinate of at least one of the receiving antenna and the transmitting antenna based at least on a time difference between transmitting the first signal from the transmitting antenna and receiving the second signal at the receiving antenna.

4. The method as claimed in claim 3, further comprising acts of:

determining an average time difference between transmitting the first signal from the transmitting antenna and receiving the second signal at the receiving antenna over a plurality of scans; and

determining a propagation constant of a medium below the conductive strip based at least in part on the average time difference.

5. The method as claimed in claim 1, further comprising acts of:

placing optical beacons at a plurality of predetermined locations;

detecting signals from the optical beacons with optical detectors located proximate to at least one of the transmitting and receiving antennas; and

determining a coordinate of at least one of the transmitting and receiving antennas based on a time difference between the optical signals detected by the optical detectors.

6. The method as claimed in claim 1, further comprising acts of:

providing a grid overlaying a surface to be surveyed;

receiving an optical signal from an optical sensor, located proximate to at least one of the transmitting and receiving antennas, when the optical sensor passes over a grid line of the grid; and

determining a position of at least one of the transmitting and receiving antennas based on reception of the optical signal.

7. The method as claimed in claim 1, further comprising acts

placing a plurality of magnetic devices at predetermined locations within an area to be surveyed;

providing a magnetic sensor located proximate to at least one of the transmitting and receiving antennas;

receiving a signal from the magnetic sensor when the magnetic sensor passes near one of the plurality of magnetic devices; and

determining a position of at least one of the transmitting and receiving antennas based on reception of the signal.

8. A method for determining a coordinate pair of an antenna location relative to a predetermined reference, the method comprising acts of:

placing the antenna proximate to a structure including first and second conductive strips located on either side of a reflective strip;

transmitting a first signal from the antenna;

measuring at least one parameter of a second signal received by the antenna, the second signal corresponding to a reflection of the first signal by the reflective strip;

transmitting a third signal from the antenna to the first conductive strip;

measuring at least one parameter of the third signal received by the antenna from the second conductive strip;

determining a first coordinate of the antenna based on a measurement of the at least one parameter of the second signal; and

determining a second coordinate of the antenna based on a measurement of the at least one parameter of the third signal.

9. The method as claimed in claim 8, wherein the act of measuring at least one parameter of the third signal includes measuring a time difference between a time of transmission of the third signal and a time of reception by the antenna of the third signal.

10. The method as claimed in claim 8, wherein the first and second conductive strips are joined.

11. The method as claimed in claim 8, further comprising acts of:

placing optical beacons at a plurality of predetermined locations;

detecting signals from the optical beacons with optical detectors located proximate to at least one of the transmitting and receiving antennas; and

determining a coordinate of at least one of the transmitting and receiving antennas based on a time difference between the optical signals detected by the optical detectors.

12. The method as claimed in claim 8, further comprising acts of:

providing a grid overlaying a surface to be surveyed;

receiving an optical signal from an optical sensor, located proximate to at least one of the transmitting and receiving antennas, when the optical sensor passes over a grid line of the grid; and

determining a position of at least one of the transmitting and receiving antennas based on reception of the optical signal.

13. The method as claimed in claim 8, further comprising acts of:

placing a plurality of magnetic devices at predetermined locations within an area to be surveyed;

providing a magnetic sensor located proximate to at least one of the transmitting and receiving antennas;

receiving a signal from the magnetic sensor when the magnetic sensor passes near one of the plurality of magnetic devices; and

determining a position of at least one of the transmitting and receiving antennas based on reception of the signal.

14. An apparatus for determining a coordinate of an antenna relative to a predetermined reference, the apparatus comprising:

a transmitting antenna that transmits a signal;

a reflective strip that reflects at least a portion of the signal transmitted by the transmitting antenna;

a receiving antenna that receives a reflected signal from the reflective strip;

a controller, coupled to the receiving antenna, that measures at least one parameter of the reflected signal and determines the coordinate of at least one of the transmitting antenna and the receiving antenna based on a measurement of the parameter.

15. The apparatus as claimed in claim 14, further comprising:

a plurality of optical beacons, disposed at predetermined locations, that transmit optical signals;

at least one optical detector, located proximate to at least one of the transmitting antenna and the receiving antenna and coupled to the controller, that detects the optical signals from the plurality of optical beacons;

wherein the controller determines the coordinate of at least one of the transmitting antenna and the receiving antenna based on the optical signals detected by the at least one optical detector.

16. The apparatus as claimed in claim 14, further comprising:

a conductive strip substantially surrounding the reflective strip;

wherein the controller is adapted to measure at least one parameter of a second signal received from conductive strip by the receiving antenna, the second signal corresponding to at least a portion of the signal transmitted by the transmitting antenna that travels along the conductive strip; and

wherein the controller is adapted to determine a second coordinate of at least one of the transmitting antenna and the receiving antenna based on a measurement of the at least one parameter of a second signal.

17. The apparatus as claimed in claim 16, wherein the coordinate is a Cartesian coordinate.

18. The apparatus as claimed in claim 16, further comprising:

a plurality of optical beacons, disposed at predetermined locations, that transmit optical signals;

at least one optical detector, located proximate to at least one of the transmitting antenna and the receiving antenna and coupled to the controller, that detects the optical signals from the plurality of optical beacons; and

wherein the controller determines the coordinate of at least one of the transmitting antenna and the receiving antenna based on the optical signals detected by the at least one optical detector.

19. The apparatus as claimed in claim 16, further comprising:

at least one optical sensor located proximate to at least one of the transmitting antenna and the receiving antenna and coupled to the controller, the at least one optical sensor providing a signal to the controller based on optical characteristics of a surface being surveyed;

wherein the controller determines a position of at least one of the transmitting antenna and the receiving antenna based on the signal from the optical sensor.

20. A system that provides an image of a subsurface area, the system comprising:

a control unit;

an antenna, coupled to the control unit, that transmits signals into a medium and receives reflected signals from the medium, the antenna being moved over the area in parallel lines to provide scans of radar data of the area; and

a reflective strip that reflects at least a portion of a signal transmitted by the antenna to provide a reflected signal;

wherein the control unit utilizes at least a portion of the reflected signal received by the antenna to provide an accurate position of the antenna in one dimension, the position being used to align successive scans of radar data to provide the image.

21. The system as claimed in claim 20, further including a conductive strip, wherein:

the antenna transmits a signal that propagates on the conductive strip, a portion of the signal being received by the antenna after a time interval; and

the control unit is adapted to determine a position of the antenna in a second dimension based on the time interval.

22. A system that provides an image of a subsurface area, the system comprising:

a control unit;

an antenna, coupled to the control unit, that transmits signals into a medium and receives reflected signals from the medium, the antenna being moved over the area in parallel lines to provide scans of radar data of the area; and

means for determining accurately a position of the antenna relative to a predetermined reference location, comprising a magnetic sensing assembly including a plurality of magnetic devices disposed at predetermined locations in the area, and at least one magnetic sensor located proximate to the antenna, that detects the magnetic devices;

wherein the at least one magnetic sensors provides a signal to the control unit, indicating detection of one of the plurality of magnetic devices, and wherein the control unit determines a position of the antenna based on the signal provided by the at least one magnetic sensor.

23. A system that provides an image of a subsurface area, the system comprising;

a control unit;

an antenna, coupled to the control unit, that transmits signals into a medium and receives reflected signals from the medium, the antenna being moved over the area in parallel lines to provide scans of radar data of the area; and

means for determining accurately a position of the antenna relative to a predetermined reference location, comprising an optical sensing assembly including at least one optical sensor located proximate to the antenna, the at least one optical sensor providing an optical signal based on optical characteristics of the area;

wherein the control unit determines a position of the antenna based at least in part on the optical signal.

24. A system that provides an image of a subsurface area, the system comprising:

a control unit;

an antenna, coupled to the control unit, that transmits signals into a medium and receives reflected signals from the medium, the antenna being moved over the area in parallel lines to provide scans of radar data of the area; and

means for determining accurately a position of the antenna relative to a predetermined reference location, comprising a controller coupled to the antenna, and

an optical sensing assembly including a plurality of optical beacons, disposed at predetermined locations in the area, that transmit optical signals; and

at least one optical detector, located proximate to the antenna and coupled to the controller, that detects the optical signals from the plurality of optical beacons;

wherein the controller determines the coordinate of the antenna based on the optical signals detected by the at least one optical detector.

25. A system that provides an image of a subsurface area, the system comprising:

a control unit;

an antenna, coupled to the control unit, that transmits signals into a medium and receives reflected signals from the medium, the antenna being moved over the area in parallel lines to provide scans of radar data of the area; and

means for determining accurately a position of the antenna relative to a predetermined reference location, comprising a combination of a reflective strip that reflects at least a portion of a signal transmitted by the antenna to provide a reflected signal, wherein the control unit utilizes at least a portion of the reflected signal received by the antenna to provide an accurate position of the antenna in one dimension, the position being used to align successive scans of radar data to provide the image, and

at least one of an optical sensing assembly and a magnetic sensing assembly.