GNSS post positioning with selected precision

• US 8,199,049 B2
• Filed: 11/18/2008
• Issued: 06/12/2012
• Est. Priority Date: 05/26/2005
• Status: Active Grant

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Talbot, Nicholas Charles, Weisenburger, Shawn, Bird, David G.
• Primary Examiner(s): Issing, Gregory C
• Application Number:
  US12/313,185
• Publication Number:
  US 20090102714A1
• Time in Patent Office: 1,302 Days
• Field of Search: 342/357.26
• US Class Current: 342/357.26
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/22 Multipath-related issues

Abstract

A computer apparatus for post positioning with a selected precision. The apparatus includes a GNSS post processor to post process reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver to compute a secure position for the rover receiver not available to a user. The apparatus includes a vector offset generator to use the selected precision to compute a dither level for offset vectors to degrade an intrinsic precision of the secure position to provide a user-available position for the rover receiver at the selected precision.

Claims

1. A computer apparatus for post positioning with a selected precision, comprising:

a global navigation satellite system (GNSS) post processor to post process reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver to compute a secure position, said secure position not available to a user, for said rover receiver; and

a vector offset generator to use a selected precision to compute a dither level for a sequence of offset vectors to degrade an intrinsic precision of said secure position to provide a user-available position for said rover receiver at said selected precision; and

wherein;

the vector offset generator includes an accuracy leveler to compensate said selected precision for a variation in said intrinsic precision by computing a smaller said dither level when said intrinsic precision is less precise.

2. The apparatus of claim 1, wherein:

the post processor is constructed to perform said post process in a different geographical place and at a later time than said rover GNSS carrier phases are observed.

3. The apparatus of claim 1, wherein:

the post processor includes an intrinsic precision estimator to compute said intrinsic precision based on covariance matrix components of a position fix for said secure position.

4. The apparatus of claim 1, wherein:

said selected precision includes a selected horizontal precision and a selected vertical precision; and

said accuracy leveler includes a horizontal precision compensator to compensate said selected horizontal precision for a horizontal component of said intrinsic precision to provide a horizontal component of said dither level, and a vertical precision compensator to compensate said selected vertical precision for a vertical component of said intrinsic precision to provide a vertical component of said dither level.

5. The apparatus of claim 4, wherein:

said accuracy leveler further includes an east horizontal scaler to use an east part of said horizontal intrinsic precision component to scale said horizontal dither level to provide an east dither level; and

a north horizontal scaler to use a north part of said horizontal intrinsic precision component to scale said horizontal dither level to provide a north dither level.

6. The apparatus of claim 1, wherein:

said secure position includes east, north and up components; and

further comprising;

a random process generator having east, north and up random processors constructed to use east, north and vertical components of said dither level to provide east, north and up sequences, respectively, for said offset vectors; and

a position dither processor to add said east, north and up sequences to said east, north and up components, respectively, of said secure position to provide said user-available position.

7. The apparatus of claim 6, wherein:

the random process generator includes a bias generator to generate east, north and up biases corresponding to a particular data set of said rover carrier phases to bias mean levels of said east, north and up sequences, respectively.

8. A computer apparatus for post positioning with a selected precision, comprising:

a global navigation satellite system (GNSS) post processor to post process reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver to compute a secure position, said secure position not available to a user, for said rover receiver;

a vector offset generator to use a selected precision to compute a dither level for a sequence of offset vectors to degrade an intrinsic precision of said secure position to provide a user-available position for said rover receiver at said selected precision; and

a DOP scaler to compute said selected precision by using at least one of a selected DOP scale factor and a selected DOP offset for processing a dilution of precision (DOP) of a constellation of satellites used for determining said secure position.

9. The apparatus of claim 8, wherein:

the DOP scaler includes a horizontal precision selector to calculate a horizontal component of said selected precision by multiplying a horizontal component of said DOP (HDOP) by a selected HDOP scale factor and adding a selected HDOP offset.

10. In a computer apparatus a post processing method for providing a selected precision for a position, comprising:

post processing reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver for computing a secure position, said secure position not available to a user, for said rover receiver; and

computing a dither level for a sequence of offset vectors for degrading an intrinsic precision of said secure precision for providing a user-available position at said selected precision for said rover receiver; and

wherein;

computing said dither level includes compensating said selected precision for a variation in said intrinsic precision by computing a smaller said dither level when said intrinsic precision is less precise.

11. The method of claim 10, wherein:

post processing is performed in a different geographical place and at a later time than said rover GNSS carrier phases are observed.

12. The method of claim 10, wherein:

post processing includes computing said intrinsic precision based on covariance matrix components of a position fix for said secure position.

13. The method of claim 10, wherein:

said selected precision includes a selected horizontal precision and a selected vertical precision; and

compensating said selected precision includes compensating said selected horizontal precision for a horizontal component of said intrinsic precision to provide a horizontal component of said dither level; and

compensating said selected vertical precision for a vertical component of said intrinsic precision to provide a vertical component of said dither level.

14. The method of claim 13, wherein:

computing said dither level further includes using an east part of said horizontal intrinsic precision component for scaling said horizontal dither level for providing an east dither level; and

using a north part of said horizontal intrinsic precision component for scaling said horizontal dither level for providing a north dither level.

15. The method of claim 10, wherein:

said secure position includes east, north and up components; and

further comprising steps of;

generating east, north and up pseudorandom sequences having east, north and vertical components of said dither level, respectively for said offset vectors; and

adding said east, north and up sequences to said east, north and up components of said secure position to provide said user-available position.

16. The method of claim 15, further comprising:

generating east, north and up biases corresponding to a particular data set of said rover carrier phases; and

biasing mean levels of said east, north and up sequences with said east, north and up biases, respectively.

17. In a computer apparatus a post processing method for providing a selected precision for a position, comprising:

post processing reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver for computing a secure position, said secure position not available to a user, for said rover receiver;

computing a dither level for a sequence of offset vectors for degrading an intrinsic precision of said secure precision for providing a user-available position at said selected precision for said rover receiver; and

computing said selected precision by using at least one of a selected DOP scale factor and a selected DOP offset for processing a dilution of precision (DOP) of a constellation of satellites used for determining said secure position.

18. The method of claim 17, wherein:

computing said selected precision includes calculating a horizontal component of said selected precision by multiplying a horizontal component of said DOP (HDOP) by a selected HDOP scale factor and adding a selected HDOP offset.

19. A computer-readable non-transitory medium having computer-executable instructions stored or carried thereby that when executed by a processor, perform a method comprising steps of:

post processing reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver for computing a secure position, said secure position not available to a user, for said rover receiver; and

computing a dither level for a sequence of offset vectors for degrading an intrinsic precision of said secure precision for providing a user-available position at said selected precision for said rover receiver; and

wherein;

computing said dither level includes compensating said selected precision for a variation in said intrinsic precision by computing a smaller said dither level when said intrinsic precision is less precise.

20. The medium of claim 19, wherein:

said selected precision includes a selected horizontal precision and a selected vertical precision; and

compensating said selected precision includes compensating said selected horizontal precision for a horizontal component of said intrinsic precision to provide a horizontal component of said dither level; and

compensating said selected vertical precision for a vertical component of said intrinsic precision to provide a vertical component of said dither level.

21. The medium of claim 20, wherein:

computing said dither level further includes using an east part of said horizontal intrinsic precision component for scaling said horizontal dither level for providing an east dither level; and

using a north part of said horizontal intrinsic precision components for scaling said horizontal dither level for providing a north dither level.

22. A computer-readable non-transitory medium having computer-executable instructions stored or carried thereby that when executed by a processor, perform a method comprising steps of:

post processing reference GNSS carrier phases from a reference system and rover GNSS carrier phases from a rover receiver for computing a secure position, said secure position not available to a user, for said rover receiver;

computing a dither level for a sequence of offset vectors for degrading an intrinsic precision of said secure precision for providing a user-available position at said selected precision for said rover receiver; and

computing said selected precision by using at least one of a selected DOP scale factor and a selected DOP offset for processing a dilution of precision (DOP) of a constellation of satellites used for determining said secure position.

23. The medium of claim 22, wherein:

computing said selected precision includes calculating a horizontal component of said selected precision by at least one of multiplying a horizontal component of said DOP (HDOP) by a selected HDOP scale factor and adding a selected HDOP offset.