GPS rover station providing a high integrity position with a selected error

• US 7,468,693 B1
• Filed: 04/30/2007
• Issued: 12/23/2008
• Est. Priority Date: 05/26/2005
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Bird, David G.
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/799,022
• Time in Patent Office: 603 Days
• Field of Search: 342/357.01, 342/357.02, 342/357.03, 342/357.06, 701/207, 701/213, 701/215
• US Class Current: 342/357.41
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/13 Receivers
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry

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 positioning system or 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 rover station for providing a position with a selected error, comprising:

a rover global navigation satellite system (GNSS) receiver constructed for using a GNSS signal for determining a first position not available to a user of the rover station; and

a position dither processor for adding a non-zero synthetic offset vector to said first position for providing a second position available to said user.

2. The rover station of claim 1, wherein:

the rover GNSS receiver is constructed for measuring rover phases for said GNSS signal, and using said rover phases and reference phases received from a GNSS reference system for said GNSS signal for determining said first position.

3. The rover station of claim 2, further comprising:

an anomaly detector for detecting an anomaly when a phase residual exceeds a selected phase residual limit; and

wherein;

the rover GNSS receiver is constructed for using said rover phases and said reference phases for determining said phase residual and using a detection of said anomaly for determining when said second position cannot be provided with a selected integrity.

4. The rover station of claim 3, wherein:

the rover GNSS receiver is constructed for inhibiting the availability of said second position when said anomaly is detected.

5. The rover station of claim 3, wherein:

said synthetic offset vector is up to about five meters; and

said selected integrity is less than about fifty centimeters.

6. The rover station of claim 3, wherein:

the rover GNSS receiver is constructed for determining said phase residual as a difference between a current phase difference and an expected phase difference, said current phase difference based on differences between said measured rover phases and said reference phases, said expected phase difference based on previous determinations of differences between said measured rover phases and said reference phases.

7. The rover station of claim 2, wherein:

the rover GNSS receiver is constructed for using a plurality of reference network phases, including said reference phases, measured by a plurality of reference network GNSS receivers at a plurality of reference network positions, respectively, with said plurality of reference network positions for determining virtual reference phases for a virtual reference position not co-located with any of said reference network GNSS receivers, and using said virtual reference phases and said virtual reference position for determining said first position.

8. The rover station of claim 1, wherein:

the position dither processor includes a vector generator for providing a stream of vectors for said synthetic offset vector, and dithering said first position with said stream of vectors for providing said second position.

9. The rover station of claim 8, wherein:

said vector generator is constrained for generating said synthetic offset vector within one of a horizontal plane, a vertical direction, a zone having a spherical boundary, a zone having a cylindrical boundary, or a zone having a box-shaped boundary.

10. A tangible medium containing a set of instructions for causing a processor to carry out the following steps for providing a position with a selected error, comprising:

using a global navigation satellite system (GNSS) signal for determining a first position not available to a user of the rover station; and

adding a selected non-zero synthetic offset vector to said first position for providing a second position available to said user.

11. A method for providing a position with a selected error, comprising:

using a global navigation satellite system (GNSS) signal for determining a first position not available to a user of the rover station; and

adding a selected non-zero synthetic offset vector to said first position for providing a second position available to said user.

12. The method of claim 11, further comprising:

receiving said GNSS signal;

measuring rover phases for said GNSS signal;

receiving reference phases from a GNSS reference system for said GNSS signal;

computing said first position from said measured rover phases and said reference phases.

13. The method of claim 12, wherein:

determining a phase residual based on said rover phases and said reference phases;

detecting an anomaly when said phase residual exceeds a selected phase residual limit; and

using a detection of said anomaly for determining when said second position cannot be provided with a selected integrity.

14. The method of claim 13, further comprising:

inhibiting the availability of said second position when said anomaly is detected.

15. The method of claim 13, wherein:

said synthetic offset vector has a length up to about five meters; and

said selected integrity is less than about fifty centimeters.

16. The method of claim 13, wherein:

determining said phase residual includes determining a difference between a current phase difference and an expected phase difference, said current phase difference based on differences between said measured rover phases and said reference phases, said expected phase difference based on previous determinations of differences between said measured rover phases and said reference phases.

17. The method of claim 12, wherein:

determining said first position includes using a plurality of reference network phases, including said reference phases, measured by a plurality of reference network GNSS receivers at a plurality of reference network positions, respectively, with said plurality of reference network positions for determining virtual reference phases for a virtual reference position not co-located with any of the reference network GNSS receivers; and

using said virtual reference phases and said virtual reference position for determining said first position.

18. The method of claim 11, further comprising:

generating a stream of vectors for said synthetic offset vector; and

dithering said first position with said stream of vectors for providing said second position.

19. The method of claim 18, further comprising:

constraining said synthetic offset vector to one of a horizontal plane, a vertical direction, a zone having a spherical boundary, a zone having a cylindrical boundary, or a zone having a box-shaped boundary.