Centimeter positioning using low cost single frequency GNSS receivers

• US 8,400,352 B2
• Filed: 11/02/2010
• Issued: 03/19/2013
• Est. Priority Date: 11/03/2009
• Status: Active Grant

• Current Assignee: Novatel Incorporated (Hexagon AB)
• Original Assignee: Novatel Incorporated (Hexagon AB)
• Inventors: Fenton, Patrick C.
• Primary Examiner(s): Phan, Dao
• Application Number:
  US12/917,625
• Publication Number:
  US 20110102254A1
• Time in Patent Office: 868 Days
• Field of Search: 342/357.21, 342/357.26, 342/357.27, 342/357.4, 701/470, 701/477
• US Class Current: 342/357.27
• CPC Class Codes: G01S 19/44 Carrier phase ambiguity resolution; Floating ambiguity; LAMBDA [Least-squares AMBiguity Decorrelation Adjustment] method

Abstract

A global positioning system includes a base GNSS receiver that determines position and carrier phase measurements for GNSS satellites in view and a rover GNSS receiver, which is a single frequency receiver that captures GNSS satellite signals transmitted in the single frequency band during a capture window from a plurality of GNSS satellites, the plurality being large enough to provide a carrier phase data set from which a solution to associated integer carrier phase ambiguities is over determined. The system determining from the captured signals, a search space associated with the satellites in view, the code phase delays and associated position uncertainty. The system resolving the integer carrier cycle ambiguities using double difference carrier phase measurements associated with signal power values that are over a predetermined threshold value. The system resolving the carrier cycle ambiguities over the capture window to a single solution set and determining the position of the rover GNSS receiver to an accuracy within centimeters using the resolved carrier phase measurements.

Claims

1. A method for determining global position, the method including the steps of:

operating one or more rover GNSS receivers to capture line-of-sight GNSS satellite signals transmitted in a given single frequency band over a capture window from a plurality of satellites large enough to provide a carrier phase data set from which a solution to associated integer carrier phase ambiguities is over determined;

processing samples of the satellites signals to determine code phase delays, carrier phase measurements and associated signal power;

determining a search space in which to resolve the integer carrier cycle ambiguities based on the satellites in view, code phase delays and position uncertainty;

resolving integer carrier cycle ambiguities using the carrier phase measurements and power measurements from the rover GNSS receiver and carrier phase measurements from one or more base GNSS receivers that alone or together have clear views of the sky, by manipulating carrier phase double difference measurements to identify a single set of solutions for the integer carrier cycle ambiguities over the capture window in the search space; and

determining the position of the rover GNSS receiver to an accuracy within centimeters using resolved carrier phase measurements.

2. The method of claim 1, further including the rover GNSS receivers turning off radio front ends after capturing the satellite signals.

3. The method of claim 1, wherein the step of resolving integer carrier cycle ambiguities uses the code phase delay and carrier phase measurements corresponding to signals from 10 or more satellites in view.

4. The method of claim 1, wherein the capture window has a length of 1 second or less.

5. The method of claim 1 wherein the one or more rover GNSS receivers determine code phase delays, carrier phase measurements and signal power using tracking assistance information provided by the one or more base GNSS receivers.

6. The method of claim 1, wherein the code phase delays and carrier phase measurements that are utilized correspond to signal power values above a predetermined threshold.

7. The method of claim 1 further including a step of turning off a radio frequency front end of the rover GNSS receiver after the signals from the capture window have been processed to produce corresponding digital inphase and quadrature samples and the samples are transmitted to the processors.

8. The method of claim 1 wherein the search space is one in which the satellite geometries of the satellites in view are orthogonal.

9. The method of claim 5 wherein the rover GNSS receiver further determines pseudoranges and provides the pseudoranges to one or more of the base GNSS receivers.

10. The method of claim 1 wherein the step of determining code phase delays and carrier phase measurements includes

convolving fast Fourier transforms (FFTs) of the captured signals and locally generated versions of the codes contained in the captured signals,

taking inverse FFTs of the convolutions, and

determining coinciding maximum I and Q correlation values.

11. The method of claim 1 further including using in the ambiguity resolution the carrier phase measurements associated with power values above a predetermined threshold.

12. The method of claim 1 wherein the rover GNSS receiver provides the captured signals to one or more of the base GNSS receivers for processing and turn off radio front ends.

13. A system for determining global position including:

one or more base GNSS receivers that alone or together have a clear view of at least portions of the sky, the base GNSS receivers determining position and carrier phase measurements for satellites in view;

a rover GNSS receiver for capturing during a capture window GNSS satellite signals transmitted in a given frequency band by a plurality of GNSS satellites in view, the plurality being large enough to provide a carrier phase data set from which a solution to associated integer carrier phase ambiguities is over determined,

one or more processors for determining code phase delays, carrier phase measurements and signal power values for the captured GNSS satellite signals,

the one or more processors resolving integer carrier cycle ambiguities using the code phase delays, carrier phase measurements and signal power values from the rover GNSS receiver and the position and carrier phase measurements from base GNSS receiver by manipulating double difference carrier phase measurements over a search space determined for the satellites in view, and based on code phase delays and associated position uncertainties at the rover GNSS receiver, and

determining the position of the rover GNSS receiver to an accuracy within centimeters using resolved carrier phase measurements.

14. The system of claim 13, wherein the respective rover GNSS receivers turn off radio front ends after capturing the satellite signals.

15. The system of claim 13, wherein the one or more processors use the code phase delays and carrier phase measurements corresponding to signals from 10 or more satellites in view.

16. The system of claim 13, wherein the capture window is less than or equal to 1 second in length.

17. The system of claim 13, wherein the one or more bases stations provide tracking assistance information to the one or more processors that determine the code phase delays and carrier phase measurements for the rover GNSS receiver.

18. The system of claim 13 wherein the respective rover GNSS receivers turn off radio frequency front ends after the signals from the capture window have been processed to produce corresponding digital inphase and quadrature samples.

19. The system of claim 16 wherein certain of the one or more processors that determine code phase delay and carrier phase measurements are in the rover GNSS receivers, and others of the one or more processors that resolve integer carrier cycle ambiguities are in one or more base stations associated with the base GNSS receivers, and the rover GNSS receiver provides code phase delay and carrier measurement information to the one or more base stations.

20. The system of claim 19 wherein the processors in the rover GNSS receivers further determine pseudoranges and provide the pseudoranges to one or more of the base GNSS receivers as position information.

21. The system of claim 13 wherein the one or more processors determining code phase delays and carrier phase measurements by

convolving FFTs of the captured signals and locally generated versions of the codes contained in the captured signals,

taking inverse FFTs of the convolutions, and

determining coinciding maximum I and Q correlation values.

22. The system of claim 13 wherein the one or more processors use in resolving the integer carrier cycle ambiguities the code phase delays and carrier phase measurements associated with signal power values above a predetermined threshold.

23. The system of claim 13 wherein the one or more processors are in one or more base stations associated with the base GNSS receivers and the rover GNSS receivers provide the captured signals to the base GNSS receivers for processing.