GNSS post positioning with elongated dither sequence

• US 20090140914A1
• Filed: 11/18/2008
• Published: 06/04/2009
• 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.
• Granted Patent: US 8,358,242 B2
• Time in Patent Office: Days
• US Class Current: 342/357.410
• CPC Class Codes: G01S 19/04 providing carrier phase data

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 random process generator to generate a sequence of offset vectors to dither the secure position according to a computed dither level to provide the selected precision for a user-available position for the rover receiver.

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 for said rover receiver, said secure position not available to a user; and

a random process generator to generate a sequence of offset vectors to dither said secure position according to a computed dither level to provide said selected precision for a user-available position for said rover receiver.

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, further comprising:

a seed generator to associate a seed with a particular data set of said rover carrier phases; and

wherein;

the random process generator is constructed to use said seed to generate the same said sequence of said offset vectors each time said sequence of said offset vectors is generated for said particular data set.

4. The apparatus of claim 1, wherein:

the random process generator includes a Normal sequence generator to provide a Normal sequence; and

an elongator to elongate said Normal sequence with a selected settling time constant.

5. The apparatus of claim 4, wherein:

the random process generator includes a bias generator to generate a bias error vector to associate with a particular data set of said rover carrier phases; and

said elongator is constructed to use said bias error vector to bias a mean of said sequence of said offset vectors for said particular data set.

6. The apparatus of claim 1, wherein:

the random process generator includes east, north and up random processors constructed to use computed east, north and up components of said dither level to provide corresponding sequences of east, north and up scalar offsets, respectively, said sequence of said offset vectors comprised of said sequences of said east, north and up scalar offsets.

7. The apparatus of claim 6, further comprising:

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

8. The apparatus of claim 1, further comprising:

a vector offset generator to compute said dither level to degrade an intrinsic precision of said secure position to provide said selected precision.

9. The apparatus of claim 8, 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.

10. The apparatus of claim 9, further comprising:

a DOP scaler to compute said selected precision by using 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.

11. A method for post positioning with a selected precision, 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 for said rover receiver, said secure position not available to a user; and

generating a sequence of offset vectors to dither said secure position according to a computed dither level for providing said selected precision for a user-available position for said rover receiver.

12. The method of claim 11, wherein:

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

13. The method of claim 11, wherein:

generating said sequence includes associating a seed with a particular data set of said rover carrier phases; and

using said seed for generating the same said sequence of said offset vectors each time said sequence of said offset vectors is generated for said particular data set.

14. The method of claim 11, wherein:

generating said sequence includes providing a Normal sequence; and

elongating said Normal sequence with a selected settling time constant.

15. The method of claim 14, further comprising:

generating a bias error vector to associate with a particular data set of said rover carrier phases; and

wherein;

generating said sequence includes using said bias error vector to bias a mean of said sequence of said offset vectors for said particular data set.

16. The method of claim 11, wherein:

generating said sequence includes using computed east, north and up components of said dither level for providing sequences of east, north and up scalar offsets, respectively, said sequence of said offset vectors comprised of said sequences of said east, north and up scalar offsets.

17. The method of claim 16, further comprising:

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

18. The method of claim 11, further comprising:

computing said dither level to degrade an intrinsic precision of said secure position for providing said selected precision.

19. The method of claim 18, further comprising:

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 method in claim 19, further comprising:

computing said selected precision by using 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.

21. A computer-readable 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 for said rover receiver, said secure position not available to a user; and

generating a sequence of offset vectors to dither said secure position according to a computed dither level for providing said selected precision for a user-available position for said rover receiver.

22. The medium of claim 21, further comprising:

generating said sequence includes associating a seed with a particular data set of said rover carrier phases; and

using said seed for generating the same said sequence of said offset vectors each time said sequence of said offset vectors is generated for said particular data set.

23. The medium of claim 21, further comprising:

generating said sequence includes providing a Normal sequence;

and elongating said Normal sequence with a selected settling time constant.

24. The medium of claim 23, further comprising:

generating a bias error vector to associate with a particular data set of said rover carrier phases; and

wherein;

generating said sequence includes using said bias error vector to bias a mean of said sequence of said offset vectors for said particular data set.

25. The medium of claim 21, wherein:

generating said sequence includes using computed east, north and up components of said dither level for providing sequences of east, north and up scalar offsets, respectively, said sequence of said offset vectors comprised of said sequences of said east, north and up scalar offsets.