GNSS rover having subscribed precision

• US 9,470,798 B2
• Filed: 11/13/2012
• Issued: 10/18/2016
• Est. Priority Date: 11/13/2012
• Status: Active Grant

• Current Assignee: Trimble Inc.
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Bird, David G.
• Primary Examiner(s): Galt, Cassie
• Application Number:
  US13/675,242
• Publication Number:
  US 20140132443A1
• Time in Patent Office: 1,435 Days
• US Class Current: 1/1
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry

Abstract

This application discloses a GNSS rover having a data receiver, a position processor and a vector error reverser. The data receiver receives GNSS position-determination reference data based on a reference erroneous position having one or more keyed intentional errors made confidential with confidential error keys. The position processor uses the GNSS position-determination reference data to determine a rover erroneous position corresponding to the reference erroneous position. The vector error reverser uses confidential access to at least one confidential error key to reverse the corresponding confidential keyed intentional error in the rover erroneous position to determine a subscribed rover position.

Claims

1. A GNSS rover for determining a GNSS-based position, including:

a carrier phase processor configured to determine rover carrier phases from GNSS signals;

a data receiver configured to receive GNSS position-determination reference data based on a reference erroneous position having one or more keyed intentional errors made confidential with one or more confidential error keys, respectively, the GNSS position-determination reference data including GNSS reference carrier phases synthesized for the reference erroneous position;

a rover position processor configured to compare the synthesized reference carrier phases with the rover carrier phases to determine a rover erroneous position having a non-subscribed vector error based on the sum of the keyed intentional errors; and

a vector error reverser having confidential access to at least one of the confidential error keys, the vector error reverser configured to reverse at least one of the confidential keyed intentional errors from the rover erroneous position to compute a subscribed rover position.

2. The GNSS rover of claim 1, wherein:

the reference erroneous position is a vector combination of the one or more confidential keyed intentional errors and a reference position for a GNSS reference apparatus; and

the vector error reverser is configured to use confidential access to some but not all of the confidential error keys to compute the subscribed rover position with a maximum positional error that is worse than a maximum positional error of the reference position but better than a maximum positional error of the reference erroneous position.

3. The GNSS rover of claim 1, wherein:

the confidential error keys and the corresponding keyed intentional errors are classified in a GNSS reference apparatus as subscribed or non-subscribed; and

the vector error reverser is configured to use the subscribed confidential error keys to reverse the corresponding subscribed keyed intentional errors from the rover erroneous position to compute the subscribed rover position with a subscribed precision that results from the non-subscribed keyed intentional errors.

4. The GNSS rover of claim 1, wherein:

the confidential error keys and the corresponding keyed intentional errors are classified in a GNSS reference apparatus as subscribed or non-subscribed; and

the vector error reverser includes one or more vector error encoders to use the subscribed confidential error keys to reproduce the subscribed keyed intentional errors; and

a vector summer to use the reproduced subscribed keyed intentional errors with the rover erroneous position to compute the subscribed rover position.

5. The GNSS rover of claim 1, wherein:

the vector error reverser includes one or more subscription filters to filter sequences of the keyed intentional errors respectively associated with confidential error keys that are subscribed and a position spread filter to filter the sum of the keyed intentional error sequences, the combination of a particular one of the subscription filters and the position spread filter constructed to distribute a particular one of the keyed intentional error sequences into a spread associated with a particular one of the subscribed confidential error keys.

6. The GNSS rover of claim 5, wherein:

the subscription filter includes a non-linear part to confine the spread within error boundaries associated with the particular confidential error key.

7. The GNSS rover of claim 1, further including:

an intentional error parameter generator to provide intentional error parameters associated with a particular one of the confidential error keys to define a shape and size of an error zone for a vector sequence for the keyed intentional error corresponding to the particular confidential error key.

8. The GNSS rover of claim 7, wherein:

the shape is selectable to be a box, a cylinder, or a sphere.

9. The GNSS rover of claim 1, further including:

a subscription precision enabler to associate a subscribed one of the confidential error keys with an intentional error parameter set; and

wherein;

the vector error reverser includes a pseudo-random sequence generator to use the subscribed confidential error key to generate confidential pseudo-random sequences;

a vector error scaler to scale the confidential pseudo-random sequences with the intentional error parameter set to generate a subscribed one of the keyed intentional errors in a pseudo-random vector sequence having an error zone controlled by the intentional error parameter set; and

a summer to combine the subscribed keyed intentional error vector sequence with a vector sequence for the rover erroneous position to compute a vector sequence for the subscribed rover position.

10. The GNSS rover of claim 1, wherein:

the vector error reverser includes a seed generator having non-confidential access to a frame number and confidential access to a subscribed one of the confidential error keys, the seed generator configured to combine the non-confidential frame number with the subscribed confidential error key to generate a confidential pseudo-random sequence for the keyed intentional errors; and

a summer to combine the keyed intentional error sequence with a sequence for the rover erroneous position in order to compute a sequence for the subscribed rover position.

11. The GNSS rover of claim 1, wherein:

the confidential error keys are irreversible.

12. The GNSS rover of claim 1, further including:

a confidential key messenger to enable the confidential access to the at least one confidential error key according to a subscription from a GNSS reference apparatus.

13. The GNSS rover of claim 12, wherein:

the confidential key messenger includes a rover public key derived from one or more secret rover keys;

a key transmitter to issue the rover public key;

a subscription key receiver to receive a subscribed one of the confidential error keys in a message encrypted with the rover public key; and

a confidential error key extractor to use the secret rover keys to extract the subscribed confidential error key from the encrypted message.

14. A method for determining a GNSS-based position, including:

determining rover carrier phases from GNSS signals received at a GNSS rover;

receiving GNSS position-determination reference data in a data receiver, the GNSS position-determination reference data based on a reference erroneous position having one or more keyed intentional errors made confidential with one or more confidential error keys, respectively, the GNSS position-determination reference data including GNSS reference carrier phases synthesized for the reference erroneous position;

comparing the rover carrier phases to the synthesized reference carrier phases in a GNSS rover position processor to determine a rover erroneous position having a non-subscribed vector error based on the sum of the keyed intentional errors; and

computing a subscribed rover position in a vector error reverser having confidential access to at least one of the confidential error keys by reversing at least one of the confidential keyed intentional errors from the rover erroneous position.

15. The method of claim 14, wherein:

the reference erroneous position is a vector combination of the sum of the one or more confidential keyed intentional errors and a reference position of a GNSS reference apparatus; and

the confidential access to some of the confidential error keys enables the computation of the subscribed rover position with a maximum positional error that is worse than a maximum positional error of the reference position but better than a maximum positional error of the reference erroneous position.

16. The method of claim 14, wherein:

the confidential error keys and the corresponding keyed intentional errors are classified as subscribed or non-subscribed in a GNSS reference apparatus; and

the step of computing the rover position includes reversing the subscribed keyed intentional errors for providing a subscribed precision that results from the non-subscribed keyed intentional errors.

17. The method of claim 14, wherein:

the confidential error keys and the corresponding keyed intentional errors are classified as subscribed or non-subscribed in a GNSS reference apparatus; and

the step of computing the subscribed rover position includes using the subscribed confidential error keys for reproducing the subscribed keyed intentional errors; and

using the reproduced keyed intentional errors with the rover erroneous position.

18. The method of claim 14, wherein:

the step of computing the subscribed rover position includes filtering sequences of the keyed intentional errors respectively associated with confidential error keys that are subscribed and filtering the sum of the keyed intentional error sequences, the combination of the filtering constructed to distribute a particular one of the keyed intentional error sequences into a spread associated with a particular one of the subscribed confidential error keys.

19. The method of claim 18, wherein:

the step of filtering the keyed intentional error sequence includes applying a non-linear gain for confining the spread within error boundaries associated with the particular confidential error key.

20. The method of claim 14, further including:

providing intentional error parameters associated with a particular one of the confidential error keys for defining a particular shape and size for a vector sequence for the keyed intentional error corresponding to the particular confidential error key.

21. The method of claim 20, wherein:

the shape is selectable to be a box, a cylinder, or a sphere.

22. The method of claim 14, further including:

associating a subscribed one of the confidential error keys with an intentional error parameter set; and

wherein;

the step of computing the subscribed rover position includes using the subscribed confidential error key for generating pseudo-random sequences;

scaling the pseudo-random sequences with the intentional error parameter set for providing a subscribed one of the keyed intentional errors as a pseudo-random vector sequence having an error zone controlled by the intentional error parameter set; and

combining the keyed intention error vector sequence with a vector sequence for the rover erroneous position for computing a vector sequence for the subscribed rover position.

23. The method of claim 14, further including:

combining a non-confidential frame number with the confidential error key for generating a pseudo-random sequence for the keyed intentional errors; and

wherein;

the step of computing the subscribed rover position includes combining the sequence of the keyed intentional errors with a sequence for the rover erroneous position.

24. The method of claim 14, wherein:

the one or more confidential error keys are secret and irreversible.

25. The method of claim 14, further including:

enabling the confidential access to the least one of the confidential error keys according to a subscription from a GNSS reference apparatus.

26. The method of claim 25, wherein:

the step of enabling the confidential access includes providing a rover public key derived from one or more secret rover keys;

issuing the rover public key;

receiving a subscribed one of the confidential error keys in a message encrypted with the rover public key; and

using the secret rover keys to extract the subscribed confidential error key from the encrypted message.

27. An apparatus including one or more processors, one or more memories, and one or more programs stored in the memories and configured to be executed by the processors, the programs including:

instructions for determining rover carrier phases from GNSS signals received at a GNSS rover;

instructions for receiving GNSS position-determination reference data based on a reference erroneous position having one or more keyed intentional errors made confidential in a GNSS reference apparatus with one or more confidential error keys, respectively, the GNSS position-determination reference data including GNSS reference carrier phases synthesized for the reference erroneous position;

instructions for comparing the synthesized reference carrier phases with the rover carrier phases to determine a rover erroneous position having the one or more keyed intentional errors; and

instructions for computing a subscribed rover position with confidential access to at least one of the confidential error keys for reversing at least one of the confidential keyed intentional errors from the rover erroneous position.