GPS reference system providing a synthetic offset vector for dithering a rover station position

• US 20060267838A1
• Filed: 05/27/2005
• Published: 11/30/2006
• Est. Priority Date: 05/27/2005
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Bird, David G.
• Granted Patent: US 7,202,813 B2
• Time in Patent Office: Days
• US Class Current: 342/357.410
• CPC Class Codes: G01S 19/04 providing carrier phase data

Abstract

A positioning system or synthetic phase processor or rover station for providing high integrity positions with graduated accuracies. The positioning system includes one or more real time kinematic (RTK) reference stations for receiving GPS signals at established reference positions and measuring reference phases. The positioning system or the rover station selects a synthetic offset vector and uses the synthetic offset vector for inferring synthetic reference phases to a synthetic position. The rover station uses the synthetic reference phases with actual or virtual reference positions for determining a rover position having an added positional error controlled by the synthetic offset vector. For another embodiment a secure rover station dithers a secure position with a synthetic offset vector for providing an unsecure rover position having the added positional error.

Claims

1. A global navigation satellite system (GNSS) reference system for controlling accuracy of a geographical position of a rover station, comprising:

a reference global navigation satellite system (GNSS) receiver for measuring a reference phase of a GNSS signal;

a vector generator for providing a synthetic offset vector; and

a reference data provider for issuing reference data including said reference phase and said synthetic offset vector, said reference data for use by a rover station for providing a rover position having an added positional error proportional to said synthetic offset vector.

2. The system of claim 1, wherein:

said reference data is protected by security provisions for inhibiting the use of said reference data from providing a position of said rover station without said added positional error.

3. The system of claim 1, wherein:

said rover station includes a rover GNSS receiver for measuring a rover phase of said GNSS signal and using said rover phase and said reference phase for determining a secure position not available to a user of said rover station; and

a position dither processor for dithering said secure position with said synthetic offset vector for generating an unsecure position and issuing said unsecure position as said rover position to said user.

4. The system of claim 3, wherein:

said reference data includes a plurality of reference network phases, including said reference phase, measured by a plurality of reference network GNSS receivers at a plurality of reference network positions, respectively, said reference network phases and said reference network phases used for determining a virtual reference phase for a virtual reference position not co-located with any of the reference network GNSS receivers, said virtual reference phase and said virtual reference position for use in said rover station for determining said secure rover position.

5. The system of claim 1, further comprising:

an anomaly detector for detecting an anomaly when a residual phase for said GNSS signal exceeds a threshold corresponding to a selected integrity limit for said secure position, and inhibiting the availability of said rover position to a user of said rover station when said anomaly is detected.

6. The system of claim 5, wherein:

said added positional error is in a range of about ten centimeters to about two meters; and

said selected integrity limit is less than about twenty centimeters.

7. The system of claim 1, wherein:

the vector generator includes a random process for providing a stream of random vectors as said synthetic offset vector.

8. The system of claim 7, wherein:

said random process is constrained with maximum input values for confining said synthetic offset vector to one of a horizontal plane, a vertical direction, a spherical error zone, a cylindrical error zone, or a box error zone.

9. A method for controlling accuracy of a geographical position of a rover station, comprising:

measuring a reference phase of a global navigation satellite system (GNSS) signal with a reference GNSS receiver;

generating a synthetic offset vector; and

issuing reference data including said reference phase and said synthetic offset vector, said reference data for use by a rover station for providing a rover position having an added positional error proportional to said synthetic offset vector.

10. The method claim 9, wherein:

issuing said reference data includes protecting said reference data with security provisions for inhibiting the use of said reference data from providing a position of said reference station without said added positional error.

11. The method of claim 9, further comprising:

said rover station includes a rover GNSS receiver for measuring a rover phase of said GNSS signal and using said rover phase and said reference phase for determining a secure position not available to a user of said rover station; and

a position dither processor for dithering said secure position with said synthetic offset vector for generating an unsecure position and issuing said unsecure position as said rover position to said user.

12. The method of claim 11, wherein:

said reference data includes a plurality of reference network phases, including said reference phase, measured by a plurality of reference network GNSS receivers at a plurality of reference network positions, respectively, said reference network phases and said reference network phases used for determining a virtual reference phase for a virtual reference position not co-located with any of the reference network GNSS receivers, said virtual reference phase and said virtual reference position for use in said rover station for determining said secure rover position.

13. The method of claim 9, further comprising:

detecting an anomaly when a residual phase for said GNSS signal exceeds a threshold corresponding to a selected integrity limit for said secure position; and

inhibiting the availability of said rover position to a user of said rover station when said anomaly is detected.

14. The method of claim 13, wherein:

said added positional error is in a range of about ten centimeters to about two meters; and

said selected integrity limit is less than about twenty centimeters.

15. The method of claim 9, wherein:

generating said synthetic offset vector includes using a random process for providing a stream of random vectors as said synthetic offset vector.

16. The method of claim 15, wherein:

generating said synthetic offset vector further includes constraining said random process with maximum input values for confining said synthetic offset vector to one of a horizontal plane, a vertical direction, a spherical error zone, a cylindrical error zone, or a box error zone.

17. A tangible medium containing a set of instructions for causing a processor to carry out the following steps for controlling accuracy of a geographical position of a rover station, comprising:

measuring a reference phase of a global navigation satellite system (GNSS) signal with a reference GNSS receiver;

generating a synthetic offset vector; and

issuing reference data including said reference phase and said synthetic offset vector, said reference data for use by a rover station for providing a rover position having an added positional error proportional to said synthetic offset vector.

18. The medium claim 17, wherein:

issuing said reference data includes protecting said reference data with security provisions for inhibiting the use of said reference data from providing a position of said reference station without said added positional error.

19. The medium of claim 17, wherein:

said rover station includes a rover GNSS receiver for measuring a rover phase of said GNSS signal and using said rover phase and said reference phase for determining a secure position not available to a user of said rover station; and

a position dither processor for dithering said secure position with said synthetic offset vector for generating an unsecure position and issuing said unsecure position as said rover position to said user.

20. The medium of claim 17, wherein:

said reference data includes a plurality of reference network phases, including said reference phase, measured by a plurality of reference network GNSS receivers at a plurality of reference network positions, respectively, said reference network phases and said reference network phases used for determining a virtual reference phase for a virtual reference position not co-located with any of the reference network GNSS receivers, said virtual reference phase and said virtual reference position for use in said rover station for determining said secure rover position.

21. The medium of claim 17, further comprising:

detecting an anomaly when a residual phase for said GNSS signal exceeds a threshold corresponding to a selected integrity limit for said secure position; and

inhibiting the availability of said rover position to a user of said rover station when said anomaly is detected.

22. The medium of claim 21, wherein:

said added positional error is in a range of about ten centimeters to about two meters; and

said selected integrity limit is less than about twenty centimeters.

23. The medium of claim 17, wherein:

generating said synthetic offset vector includes using a random process for providing a stream of random vectors for said synthetic offset vector.

24. The medium of claim 23, wherein:

generating said synthetic offset vector further includes constraining said random process with maximum input values for confining said synthetic offset vector to one of a horizontal plane, a vertical direction, a spherical error zone, a cylindrical error zone, or a box error zone.