GPS rover station for synthesizing synthetic reference phases for controlling accuracy of high integrity positions

• US 7,079,075 B1
• Filed: 06/07/2005
• Issued: 07/18/2006
• Est. Priority Date: 06/07/2005
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Bird, David G., Connor, Dennis
• Primary Examiner(s): PHAN, DAO LINDA
• Application Number:
  US11/146,757
• Time in Patent Office: 406 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: G01C 15/00 Surveying instruments or accessories not provided for in groups G01C1/00 - G01C13/00
• 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 rover station operating with a global navigation satellite system (GNSS) reference system for controlling geographical position accuracy, comprising:

a secure signal receiver for receiving secure reference data having information for a reference phase for a GNSS signal and a reference position;

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

a rover GNSS receiver for using said reference position and said synthetic reference phase for determining a position of the rover station with respect to said reference position having an added positional error proportional to said synthetic offset vector.

2. The rover station of claim 1, wherein:

said reference data is protected by security provisions for inhibiting the use of said reference data by an unauthorized user.

3. The rover station of claim 1, wherein:

said reference data includes information for a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, including a master reference network position separated from said reference position by a non-zero virtual vector; and

the secure synthetic phase processor determines a master synthetic vector from a sum of said synthetic offset vector and said virtual vector; and

uses said master synthetic vector with said reference network phases and said reference network positions for determining said synthetic reference phase.

4. The rover station 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 rover station 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 rover station of claim 1, wherein:

the rover GNSS receiver measures a rover phase for said GNSS signal and determines a phase residual corresponding to a difference between a current phase difference and an expected phase difference, said current phase difference based on a difference between said measured rover phase and said synthetic reference phase, said expected phase difference based on previous determinations of differences between said measured rover phase and said synthetic reference phase; and

further comprising;

an anomaly detector for detecting an anomaly when said phase residual exceeds a selected integrity limit, and inhibiting the use 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 in the range of about one centimeter to about twenty centimeters.

8. A method in a rover station operating with a global navigation satellite system (GNSS) reference system for controlling geographical position accuracy, comprising:

receiving secure reference data having information for a reference phase for a GNSS signal and a reference position;

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

using said reference position and said synthetic reference phase for determining 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, wherein:

said reference data is protected by security provisions for inhibiting the use of said reference data by an unauthorized user.

10. The method of claim 8, wherein:

said reference data includes information for a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, including 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 master synthetic vector from a sum of said synthetic offset vector and said virtual vector; and

using said master synthetic vector with said reference network phases and said reference network positions for determining said synthetic reference phase.

11. The method of claim 8, further comprising:

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

12. The method of claim 11, further comprising:

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.

13. The method of claim 8, further comprising:

measuring a rover phase for said GNSS signal;

determining a phase residual corresponding to a difference between a current phase difference and an expected phase difference, said current phase difference based on a difference between said measured rover phase and said synthetic reference phase, said expected phase difference based on previous determinations of differences between said measured rover phase and said synthetic reference phase;

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

inhibiting the use 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 in the range of about one centimeter to 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 secure reference data having information for a reference phase for a GNSS signal and a reference position;

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

using said reference position and said synthetic reference phase for determining 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, wherein:

said reference data is protected by security provisions for inhibiting the use of said reference data by an unauthorized user.

17. The medium of claim 15, wherein:

said reference data includes information for a plurality of reference network phases, including said reference phase, measured at a plurality of reference network positions, respectively, including 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 master synthetic vector from a sum of said synthetic offset vector and said virtual vector; and

using said master synthetic vector with said reference network phases and said reference network positions for determining said synthetic reference phase.

18. The medium of claim 15, further including steps for:

using a random process for selecting said synthetic offset vector.

19. The medium of claim 18, wherein:

selecting 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 or a vertical direction.

20. The medium of claim 15, further including steps for:

measuring a rover phase for said GNSS signal;

determining a phase residual corresponding to a difference between a current phase difference and an expected phase difference, said current phase difference based on a difference between said measured rover phase and said synthetic reference phase, said expected phase difference based on previous determinations of differences between said measured rover phase and said synthetic reference phase;

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

inhibiting the use 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 in the range of about one centimeter to about twenty centimeters.