Position determination using carrier phase measurements of satellite signals

• US 20070052583A1
• Filed: 09/08/2005
• Published: 03/08/2007
• Est. Priority Date: 09/08/2005
• Status: Active Grant

• Current Assignee: Topcon GPS, LLC
• Original Assignee: Topcon GPS, LLC
• Inventors: Veitsel, Victor, Zhodzishsky, Mark, Zinoviev, Alexey
• Granted Patent: US 7,522,099 B2
• Time in Patent Office: Days
• US Class Current: 342/357.240
• CPC Class Codes: G01S 19/43 using carrier phase measurements, e.g. kinematic positioning; using long or short baseline interferometry
• CPC Class Codes: G01S 19/51 Relative positioning

Abstract

Disclosed is a method and apparatus for determining the relative position of a mobile unit that moves from an initial location to a plurality of successive positions. The mobile unit receives signals from a plurality of navigation satellites and tracks the carrier phases of the signals during movement. For each of the received signals, carrier phase increments are calculated over a plurality of epochs. Anomalous carrier phase increments are determined and eliminated from further calculations. The non-eliminated carrier phase increments are then used to calculate coordinate increments for each of the time epochs. If, after elimination, the remaining number of carrier-phase increments is less than a threshold for a particular epoch, then coordinate increments for the particular epoch may be extrapolated using data from prior epochs. In various embodiments, least squares method and Kalman filtering may be used to calculate the coordinate increments. The coordinate increments may then be summed over a plurality of time epochs in order to determine a position of the mobile unit relative to its initial position.

Claims

1. A method for determining relative positions of a mobile unit, wherein said mobile unit moves from an initial location to a plurality of successive positions, said method comprising the steps of:

receiving a plurality of signals from a corresponding plurality of navigation satellites and tracking carrier phases of said signals during movement;

calculating carrier phase increments for each of said signals for each of a plurality of time epochs;

determining which of said carrier phase increments are anomalous and eliminating them from further calculations;

calculating coordinate increments for each of said plurality of time epochs using non-eliminated carrier phase increments; and

summing said coordinate increments over a plurality of time epochs to determine a position of said mobile unit relative to said initial location.

2. The method of claim 1 wherein said step of calculating coordinate increments further comprises the steps of:

generating a transformation matrix G using satellite coordinates for navigation satellites whose carrier phase increments were not determined to be anomalous; and

calculating said coordinate increments using said transformation matrix G and a least squares method.

3. The method of claim 1 wherein said step of determining which of said carrier phase increments are anomalous further comprises the steps of:

calculating residuals of carrier-phase increments; and

comparing said residuals to a threshold.

4. The method of claim 3 wherein said step of eliminating anomalous carrier phase increments from further calculations further comprises the steps of:

determining a maximum residual; and

setting a channel weight for a satellite associated with said maximum residual to zero.

5. The method of claim 4 wherein said step of setting a channel weight for a satellite associated with said maximum residual to zero further comprises the step of:

resetting said channel weight to zero during two consecutive epochs.

6. The method of claim 4 wherein said step of setting a channel weight for a satellite associated with said maximum residual to zero further comprises the step of:

resetting said channel weight to zero during one epoch.

7. The method of claim 1 wherein said step of determining which of said carrier phase increments are anomalous further comprises the steps of:

calculating residuals of carrier-phase increments;

calculating a sum of residuals squares; and

comparing said sum of residuals squares to a threshold.

8. The method of claim 7 wherein said step of eliminating anomalous carrier phase increments from further calculations further comprises the steps of:

determining a maximum residual; and

setting a channel weight for a satellite associated with said maximum residual to zero.

9. The method of claim 8 wherein said step of setting a channel weight for a satellite associated with said maximum residual to zero further comprises the step of:

resetting said channel weight to zero during two consecutive epochs.

10. The method of claim 8 wherein said step of setting a channel weight for a satellite associated with said maximum residual to zero further comprises the step of:

resetting said channel weight to zero during one epoch.

11. The method of claim 1 wherein said step of determining which of said carrier phase increments are anomalous further comprises the step of:

calculating an average weighted residual.

12. The method of claim 11 wherein said step of determining which of said carrier phase increments are anomalous further comprises the step of:

detecting a large difference between carrier phase increments for neighboring epochs.

13. The method of claim 1 further comprising the step of:

after said step of eliminating, determining whether the remaining number of carrier-phase increments is less than a threshold for a particular epoch; and

if the remaining number of carrier-phase increments is less than a threshold for a particular epoch, then extrapolating coordinate increments for said particular epoch using data from prior epochs.

14. The method of claim 1 wherein said step of determining which of said carrier phase increments are anomalous is based at least in part on alarm signals of satellite channel indicators.

15. The method of claim 1 further comprising the step of:

using coordinate increments calculated during a period of time when said mobile unit is stationary as a correction extrapolation during later periods of time when said mobile unit is moving.

16. The method of claim 1 wherein, during a motion interval, said mobile unit traverses a closed loop and returns to said initial location, said method further comprising the steps of:

determining a starting position of said mobile unit at said initial position prior to said traversal;

determining a finishing position of said mobile unit when it returns to said initial location after said traversal; and

calculating the difference between said finishing position and said starting position; and

using said difference as an error of calculated coordinate increments.

17. The method of claim 16 wherein said step of using said difference as an error of calculated coordinate increments further comprises the steps of:

dividing said difference by a number of elapsed epochs to determine an average error of coordinate increments; and

using said average error of coordinate increments as a correction for measured coordinate increments during said motion interval.

18. The method of claim 1 further comprising the step of:

receiving data from a base station via a communication channel;

wherein said step of calculating coordinate increments is further based upon said received data from said base station utilizing differential processing mode so that highly correlated components of base and rover errors are eliminated.

19. A mobile unit comprising:

means for receiving a plurality of signals from a corresponding plurality of navigation satellites and tracking carrier phases of said signals during movement;

means for calculating carrier phase increments for each of said signals for each of a plurality of time epochs;

means for determining which of said carrier phase increments are anomalous and eliminating them from further calculations;

means for calculating coordinate increments for each of said plurality of time epochs using non-eliminated carrier phase increments; and

means for summing said coordinate increments over a plurality of time epochs to determine a position of said mobile unit relative to said initial location.

20. The mobile unit of claim 19 wherein said means for calculating coordinate increments further comprises:

means for generating a transformation matrix G using satellite coordinates for navigation satellites whose carrier phase increments were not determined to be anomalous; and

means for calculating said coordinate increments using said transformation matrix G and a least squares method.

21. The mobile unit of claim 19 wherein said means for determining which of said carrier phase increments are anomalous further comprises:

means for calculating residuals of carrier-phase increments; and

means for comparing said residuals to a threshold.

22. The mobile unit of claim 21 wherein said means for eliminating anomalous carrier phase increments from further calculations further comprises:

means for determining the maximum residual; and

means for setting a channel weight for a satellite associated with said maximum residual to zero.

23. The mobile unit of claim 22 wherein said means for setting a channel weight for a satellite associated with said maximum residual to zero further comprises:

means for resetting said channel weight to zero during two consecutive epochs.

24. The mobile unit of claim 22 wherein said means for setting a channel weight for a satellite associated with said maximum residual to zero further comprises:

means for resetting said channel weight to zero during one epoch.

25. The mobile unit of claim 19 wherein said means for determining which of said carrier phase increments are anomalous further comprises:

means for calculating residuals of carrier-phase increments;

means for calculating a sum of residuals squares; and

means for comparing said sum of residuals squares to a threshold.

26. The mobile unit of claim 25 wherein said means for eliminating anomalous carrier phase increments from further calculations further comprises:

means for determining a maximum residual; and

means for setting a channel weight for a satellite associated with said maximum residual to zero.

27. The mobile unit of claim 26 wherein said means for setting a channel weight for a satellite associated with said maximum residual to zero further comprises:

means for resetting said channel weight to zero during two consecutive epochs.

28. The mobile unit of claim 26 wherein said means for setting a channel weight for a satellite associated with said maximum residual to zero further comprises:

means for resetting said channel weight to zero during one epoch.

29. The mobile unit of claim 19 wherein said means for determining which of said carrier phase increments are anomalous further comprises:

means for calculating an average weighted residual.

30. The mobile unit of claim 19 wherein said means for determining which of said carrier phase increments are anomalous further comprises:

means for detecting a large difference between carrier phase increments for neighboring epochs.

31. The mobile unit of claim 19 further comprising:

means for using coordinate increments calculated during a period of time when said mobile unit is stationary as a correction extrapolation during later periods of time when said mobile unit is moving.

32. The mobile unit of claim 19 further comprising:

means for determining a starting position of said mobile unit at an initial position prior to a traversal;

means for determining a finishing position of said mobile unit when it returns to said initial location after said traversal; and

means for calculating the difference between said finishing position and said starting position; and

means for using said difference as an error of calculated coordinate increments.

33. The mobile unit of claim 32 wherein said means for using said difference as an error of calculated coordinate increments further comprises:

means for dividing said difference by a number of elapsed epochs to determine an average error of coordinate increments; and

means for using said average error of coordinate increments as a correction for measured coordinate increments during said motion interval.