GNSS reference for subscribed precisions

• US 9,223,026 B2
• Filed: 11/13/2012
• Issued: 12/29/2015
• 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): Liu, Harry
• Application Number:
  US13/675,186
• Publication Number:
  US 20140132444A1
• Time in Patent Office: 1,141 Days
• Field of Search: 342/386, 342/357.42, 342/357.46
• US Class Current: 1/1
• CPC Class Codes: G01S 19/04 providing carrier phase data
• CPC Class Codes: G01S 19/074 providing integrity data, e.g. WAAS

Abstract

This application discloses a GNSS reference apparatus having a vector error generator and a reference data server. The vector error generator generates one or more sequences of keyed intentional errors made confidential with confidential error keys, and then combines the sequences to generate a sequence of reference erroneous positions. The reference data server issues GNSS position-determination reference data based on the reference erroneous positions where the keyed intentional errors for at least one of the confidential sequences are reversible with confidential access to the corresponding confidential error key for determining a GNSS-based position.

Claims

1. A GNSS reference apparatus, including:

a vector error generator to generate a sequence of reference erroneous positions by combining one or more sequences of keyed intentional errors, the keyed intentional error sequences made confidential with one or more confidential error keys, respectively; and

a reference data server to issue GNSS position-determination reference data based on the reference erroneous positions to enable GNSS position determination where the keyed intentional errors for at least one of the confidential sequences are reversible with confidential access to a corresponding at least one of the confidential error keys wherein, the vector error generator includes a seed generator to combine a non-confidential frame number with a particular one of the confidential error keys to generate a particular one of the keyed intentional error sequences as a pseudo-random sequence, where the pseudo-random sequence is reproducible at a GNSS rover in data frames with the non-confidential frame number and the particular confidential error key.

2. The GNSS reference apparatus of claim 1, further including:

a synthetic reference carrier phase processor to synthesize GNSS reference carrier phases for the reference erroneous positions from GNSS signals, and wherein the reference data server is configured to provide the synthesized GNSS reference carrier phases in the GNSS position-determination reference data.

3. The GNSS reference apparatus of claim 1, wherein:

the GNSS position-determination reference data is composed to permit a GNSS rover having the confidential access to use the at least one confidential error key for the GNSS position determination.

4. The GNSS reference apparatus of claim 1, further including:

a subscribed precision catalog to classify the confidential error keys and the corresponding keyed intentional error sequences as subscribed or non-subscribed; and

a confidential key messenger to enable the confidential access for the subscribed confidential error keys for the GNSS position determination with a subscribed precision resulting from the non-subscribed keyed intentional error sequences.

5. The GNSS reference apparatus of claim 4, wherein:

the confidential key messenger includes a public key receiver to receive first and second rover public keys for first and second GNSS rovers, respectively, where the first rover public key was associated with a first rover private key for a first GNSS rover and the second rover public key was associated with a second rover private key for a second GNSS rover;

a confidential key encrypter to encrypt first and second sets of the subscribed confidential error keys with the first and second rover public keys, respectively; and

a subscription key transmitter to issue the encrypted first and second subscribed confidential error key sets for decryption with the first and second rover private keys for the GNSS position-determination only for the first and second GNSS rovers, respectively.

6. The GNSS reference apparatus of claim 1, wherein:

the GNSS position determination reference data is composed so that the confidential access to a first but not a second confidential error key enables the GNSS position determination with a precision degraded by the second but not the first keyed intentional error sequence.

7. The GNSS reference apparatus of claim 1, wherein:

the vector error generator includes first and second vector error encoders to use a first and a second of the confidential error keys to generate a first and a second of the keyed intentional error sequences, respectively; and

a vector summer to combine the first and second keyed intentional error sequences with a reference position to generate vectors for the reference erroneous position sequence.

8. The GNSS reference apparatus of claim 7, wherein:

the GNSS position determination reference data is composed for the confidential access to the first but not the second confidential error key to confine a maximum positional error for the GNSS position determination to be greater than a maximum positional error of the reference position but less than a maximum positional error corresponding to the reference erroneous position sequence.

9. The GNSS reference apparatus of claim 1, wherein:

the vector error generator includes subscription filters associated with the confidential error keys to filter the keyed intentional error sequences, respectively; and

a position spread filter to filter the sum of the keyed intentional errors 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 corresponding particular one of the confidential error keys.

10. The GNSS reference apparatus of claim 9, wherein:

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

11. The GNSS reference apparatus of claim 1, further including:

an intentional error parameter generator to provide intentional error parameter sets associated with the confidential error keys, respectively, to define shapes and sizes of the corresponding confidential sequences of keyed intentional errors.

12. The GNSS reference apparatus of claim 11, wherein:

the shapes are selectable by the intentional error parameter sets as a box, a cylinder, or a sphere.

13. The GNSS reference apparatus of claim 1, further including:

an intentional error parameter generator to associate a particular intentional error parameter set with a particular one of the confidential error keys; and

wherein;

the vector error generator includes pseudo-random sequence generators to use the particular one of the confidential error keys to generate confidential pseudorandom sequences;

and a vector error scaler to scale the confidential pseudo-random sequences with the particular intentional error parameter set to provide a particular one of the sequences of keyed intentional errors as vectors having an error zone having a shape and a size controlled by the intentional error parameter set.

14. The GNSS reference apparatus of claim 1, further including:

a confidential key generator to generate the confidential error keys to be irreversible.

23. The GNSS method of claim 14, further including:

providing intentional error parameter sets associated with the confidential error keys, respectively, for defining shapes and sizes of the corresponding confidential sequences of keyed intentional errors.

24. The method of claim 23, wherein:

the shapes are selectable by the intentional error parameter sets as a box, a cylinder, or a sphere.

25. The method of claim 14, further including steps of:

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

wherein;

the step of generating the sequence of reference erroneous positions includes using the particular one of the confidential error keys for generating confidential pseudo-random sequences; and

scaling the confidential pseudo-random sequences with the particular intentional error parameter set for providing a particular one of the sequences of keyed intentional errors as vectors having an error zone having a shape and a size controlled by the intentional error parameter set.

26. The method of claim 14, wherein:

the step of generating the reference erroneous position sequence includes combining a non-confidential frame number with a particular one of the confidential error keys for generating a particular one of the keyed intentional error sequences as a pseudorandom sequence, where the pseudo-random sequence is reproducible at a remote site in data frames with the non-confidential frame number and the particular confidential error key.

27. The method of claim 14, further including a step of:

generating the confidential error keys in the GNSS reference apparatus to be irreversible.

15. A method for providing GNSS reference data for determining a GNSS-based position, including steps of:

using one or more confidential error keys for making one or more sequences of keyed intentional errors confidential in a GNSS reference apparatus;

generating a sequence of reference erroneous positions in the GNSS reference apparatus by combining the one or more confidential keyed intentional error sequences; and

issuing GNSS position-determination reference data from the GNSS reference apparatus based on the reference erroneous positions to enable GNSS position determination where the keyed intentional errors for at least one the confidential sequences are reversible with confidential access for a corresponding at least one of the confidential error keys;

filtering the one of more keyed intentional error sequences with subscription filters respectively associated with the confidential error keys; and

filtering the sum of the keyed intentional error sequences to distribute a particular one of the keyed intentional error sequence into a spread associated with a corresponding particular one of the confidential error keys wherein the step of filtering includes applying a non-linear gain for confining the spread within error boundaries associated with the particular confidential error key.

16. The method of claim 15, further including a step of:

synthesizing GNSS reference carrier phases in the GNSS reference apparatus for the reference erroneous positions from GNSS signals; and

wherein the GNSS position-determination reference data includes the synthesized GNSS reference carrier phases.

17. The method of claim 15, further including a step of:

composing the GNSS position-determination reference data to permit a GNSS rover having the confidential access to use the at least one confidential error key for the GNSS position determination.

18. The method of claim 15, further including steps of:

classifying the confidential error keys and corresponding keyed intentional error sequences as subscribed or non-subscribed; and

providing the confidential access for the subscribed confidential error keys for the GNSS position determination with a subscribed precision resulting from the non-subscribed keyed intentional error sequences.

19. The method of claim 18, wherein:

the step of providing the confidential access includes receiving first and second rover public keys for first and second GNSS rovers, respectively, where the first rover public key was associated with a first rover private key and the second rover public key was associated with a second rover key;

encrypting first and second sets of the subscribed confidential error keys with the first and second rover public keys, respectively; and

issuing the encrypted first and second subscribed confidential error key sets for sets for decryption with the first and second private rover keys for the GNSS position determination only for the first and second GNSS rovers, respectively.

20. The method of claim 15, wherein:

the GNSS position determination reference data is composed so that the confidential access to a first but not a second confidential error key enables the GNSS position determination with a precision degraded by the second but not the first keyed intentional error sequence.

21. The method of claim 15, wherein:

the step of generating the reference erroneous position sequence includes using a first and a second of the confidential error keys for generating a first and a second of the keyed intentional error sequences respectively, and combining the first and second keyed intentional error sequences with a reference position for generating vectors for the reference erroneous position sequence.

22. The method of claim 21, wherein:

the GNSS position determination reference data is composed for the confidential access to the first but not the second confidential error key to confine a maximum positional error for the GNSS position determination to be greater than a maximum positional error of the reference position but less than a maximum positional error corresponding to the reference erroneous position sequence.