GPS reference system providing synthetic reference phases for controlling accuracy of high integrity positions

• US 20060279455A1
• Filed: 06/08/2005
• Published: 12/14/2006
• Est. Priority Date: 06/08/2005
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Bird, David G., Connor, Dennis
• Granted Patent: US 7,292,183 B2
• Time in Patent Office: Days
• US Class Current: 342/357.410
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

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 positioning system for providing synthetic reference data for controlling geographical position accuracy, comprising:

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

a synthetic phase processor for using said reference phase for inferring a synthetic reference phase at a synthetic position, said synthetic position separated from a reference position by a selected non-zero synthetic offset vector; and

providing said synthetic reference phase and said reference position for use by a rover station including a rover GNSS receiver for determining a rover position with respect to said reference position having an added positional error proportional to said synthetic offset vector.

2. The positioning system of claim 1, wherein:

the synthetic phase processor uses 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, for determining a virtual reference phase for a virtual reference position not co-located with the reference GNSS receiver, and provides said virtual reference position as said reference position.

3. The positioning system of claim 1, wherein:

the reference GNSS receiver is located at a master reference network position separated from said reference position by a non-zero virtual vector; and

the synthetic phase processor determines a non-zero master synthetic vector from a sum of said synthetic offset vector and said virtual vector, and uses a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, including said master reference network position, with said master synthetic vector for determining said synthetic reference phase.

4. The positioning system of claim 1, wherein:

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

5. The positioning system of claim 4, wherein:

said random process vector generator 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.

6. The positioning system of claim 1, further comprising:

an anomaly detector for determining a reference phase residual corresponding to a difference between a current and a previous difference between a reference phase measurement at a first reference network position and a reference phase measurement at a second reference network position;

detecting an anomaly when said phase residual exceeds a threshold corresponding to a selected integrity limit; and

inhibiting said rover GNSS receiver from said determination of said rover position when said anomaly is detected.

7. The positioning system of claim 6, 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.

8. A method for providing synthetic reference data for controlling geographical position accuracy, comprising:

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

inferring a synthetic reference phase for said GNSS signal to a synthetic position using said reference phase, said synthetic position separated from a reference position by a selected non-zero synthetic offset vector; and

providing said synthetic reference phase and said reference position for use by a rover GNSS receiver for determination of a rover position with respect to said reference position having an added positional error proportional to said synthetic offset vector.

9. The method of claim 8, further comprising:

determining a virtual reference phase for a virtual reference position from a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, not co-located with said virtual reference position; and

wherein

the step of providing said synthetic reference phase and said reference position includes providing said virtual reference position as said reference position.

10. The method of claim 8, wherein:

said reference phase is measured at a master reference network position separated from said reference position by a non-zero virtual vector; and

inferring said synthetic reference phase includes determining a non-zero master synthetic vector from a sum of said synthetic offset vector and said virtual vector; and

using a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, including said master reference network position, with said master synthetic vector for determining said synthetic reference phase.

11. The method of claim 8, further comprising:

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

12. The method of claim 11, further comprising:

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 by constraining said random process with maximum input values.

13. The method of claim 8, further comprising:

determining a reference phase residual corresponding to a difference between a current and a previous difference between a reference phase measurement at a first reference network position and a reference phase measurement at a second reference network position;

detecting an anomaly when said phase residual exceeds a threshold corresponding to a selected integrity limit; and

inhibiting said rover GNSS receiver from said determination of said rover position 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. A tangible medium containing a set of instructions for causing a processor to carry out the following steps for controlling geographical position accuracy, comprising:

receiving information for a measurement defining a reference phase for a global navigation satellite system (GNSS) signal;

inferring a synthetic reference phase for said GNSS signal to a synthetic position using said reference phase, said synthetic position separated from a reference position by a selected non-zero synthetic offset vector; and

providing said synthetic reference phase and said reference position for use by a rover GNSS receiver for determination of a rover position with respect to said reference position having an added positional error proportional to said synthetic offset vector.

16. The medium of claim 15, further including steps of:

determining a virtual reference phase for a virtual reference position from a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, not co-located with said virtual reference position; and

wherein

providing said synthetic reference phase and said reference position includes providing said virtual reference position as said reference position.

17. The medium of claim 15, wherein:

said reference phase is measured at a master reference network position separated from said reference position by a non-zero virtual vector; and

inferring said synthetic reference phase includes determining a non-zero master synthetic vector from a sum of said synthetic offset vector and said virtual vector; and

using a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, including said master reference network position, with said master synthetic vector for determining said synthetic reference phase.

18. The medium of claim 15, containing further instructions for:

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

19. The medium of claim 18, containing further instructions 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 by constraining said random process with maximum input values.

20. The medium of claim 15, wherein:

determining a reference phase residual corresponding to a difference between a current and a previous difference between a reference phase measurement at a first reference network position and a reference phase measurement at a second reference network position;

detecting an anomaly when said phase residual exceeds a threshold corresponding to a selected integrity limit; and

inhibiting said rover GNSS receiver from said determination of said rover position when said anomaly is detected.

21. The medium of claim 20, 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.