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1. (WO2019063983) A METHOD AND SYSTEM FOR CALIBRATING A SYSTEM PARAMETER
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CLAIMS

1. A method for performing in a positioning, navigation, tracking, frequency-measuring, or timing system, comprising:

providing first and second estimates of at least one system parameter during a first time period, wherein the at least one system parameter has a true value and/or true evolution over time during the first time period;

providing a local signal;

receiving, at a receiver, a signal from a remote source;

providing a correlation signal by correlating the local signal with the received signal;

providing amplitude and/or phase compensation of at least one of the local signal, the received signal and the correlation signal based on each of the first and second estimates so as to provide first and second amplitude-compensated and/or phase-compensated correlation signals corresponding to the first and second estimates of the at least one system parameter during the first time period, and;

determining which of the first and second estimates is nearer the true value and/or true evolution over time of the at least one system parameter during the first time period, based on a comparison between the first and second amplitude-compensated and/or phase-compensated correlation signals.

2. The method of claim 1 , wherein the first and second estimates of the at least one system parameter are used to provide respective first and second predictions of the phase and/or amplitude evolution of the received signal from the remote source during the first time period, and wherein the amplitude and/or phase compensation is performed based on said first and second predictions.

3. The method of claim 2, wherein the amplitude and/or phase compensation is based on a plurality of vectors derived from the first and second predictions.

4. The method of any of the preceding claims, further comprising the step of providing a measured or assumed movement of the receiver during the first time period, and wherein the amplitude and/or phase compensation is based on the measured or assumed movement of the receiver.

5. The method of claim 4 wherein the first and second estimates are based on the measured or assumed movement of the receiver.

6. The method of claim 5, wherein the first and second estimates are based on a measured movement of the receiver, provided by at least one sensor configured to make measurements from which position and/or orientation and/or movement may be determined.

7. The method of claim 6, wherein the at least one sensor is an inertial measurement unit.

8. The method of claim 6 or claim 7, wherein the at least one system parameter is a bias of the at least one sensor.

9. The method of any of the preceding claims, wherein the at least one system parameter is a parameter of a motion and/or position and/or orientation of the receiver during the first time period.

10. The method of claim 9, wherein the at least one system parameter is one of: a receiver velocity, a receiver position, a receiver orientation a receiver heading, a receiver heading offset, a step length of a user of the receiver, and a line-of-sight vector between the receiver and the remote source.

11. The method of any of the preceding claims, wherein the at least one system parameter is a frequency reference error of the receiver or remote source.

12. The method of any of the preceding claims, wherein the step of determining which of the first and second estimates is nearer the true value and/or true evolution over time of the at least one system parameter comprises selection of the correlation signal having the highest correlation.

13. The method of claim 12, wherein the selected correlation signal is constrained to lie within a frequency window of width that is inversely proportional to the coherent integration time of the correlation.

14. The method of claim 13, wherein the coherent integration time is greater than or equal to one second.

15. The method of claim 13 or claim 14, wherein a lower bound on a difference between the first and second parameter estimates is inversely proportional to the coherent integration time.

16. The method of any of the preceding claims, further comprising storing in memory the estimate that is determined to be nearer the true value and/or true evolution over time of the system parameter.

17. The method of any of the preceding claims, further comprising the step of providing a third estimate of the at least one system parameter during the first time period, wherein the third estimate is based upon the determination of which of the first and second estimates was nearer the true value and/or true evolution over time of the at least one system parameter during the first time period.

18. The method of any of the preceding claims, wherein the receiver is a GNSS receiver and the remote source is a GNSS satellite.

19. A computer readable medium comprising instructions that when executed by a computer cause the computer to perform the method of any of the preceding claims.

20. A positioning, navigation, tracking, frequency-measuring, or timing system, comprising:

a local signal generator, configured to provide a local signal;

a receiver configured to receive a signal from a remote source;

a correlation unit configured to provide a correlation signal by correlating the local signal with the received signal, and;

a processor configured to perform the steps of:

providing amplitude and/or phase compensation of at least one of the local signal, the received signal and the correlation signal based on first and second estimates of at least one system parameter during a first time period so as to provide first and second amplitude-compensated and/or phase-compensated correlation signals corresponding to the first and second estimates of the at least one system parameter during the first time period, wherein the at least one system parameter has a true value and/or true evolution over time during the first time period and;

determining which of the first and second estimates is nearer the true value and/or true evolution over time of the at least one system parameter during the first time period, based on a comparison between the first and second amplitude-compensated and/or phase-compensated correlation signals.

21. The system of claim 20, wherein the processor is further configured to provide first and second predictions of the phase and/or amplitude evolution of the received signal from the remote source during the first time period based on the respective first and second estimates of the at least one system parameter, and wherein the amplitude and/or phase compensation is performed based on said first and second predictions.

22. The system of claim 20 or claim 21 , wherein the amplitude and/or phase compensation is based on a plurality of vectors derived from the first and second predictions.

23. The system of any of claims 20 to 22, further comprising a motion module configured to provide a measured or assumed movement of the receiver during the first time period, and wherein the amplitude and/or phase compensation is based on the measured or assumed movement of the receiver.

24. The system of claim 23, wherein the first and second estimates are based on the measured or assumed movement of the receiver.

25. The system of claim 23 or claim 24, wherein the motion module comprises at least one sensor configured to make measurements from which position and/or orientation and/or movement may be determined.

26. The system of claim 25, wherein the at least one sensor is an inertial measuring unit.

27. The system of any claim 25 or claim 26, wherein the at least one system parameter is a bias of the at least one sensor.

28. The system of any of claims 20 to 27, wherein the at least one system parameter is a parameter of a motion and/or position and/or orientation of the receiver during the first time period.

29. The system of claim 28, wherein the at least one system parameter is one of: a receiver velocity, a receiver position, a receiver orientation, a receiver heading, a receiver heading offset, a step length of a user of the receiver, and a line-of-sight vector between the receiver and the remote source.

30. The system of any of claims 20 to 29, wherein the at least one system parameter is a frequency reference error of the receiver or remote source.

31. The system of any of claims 20 to 30, wherein the receiver is a GNSS receiver and the remote source is a GNSS satellite.

32. The system of any of claims 20 to 31 , further comprising a memory configured to store the estimate that is determined to be nearer the true value and/or true evolution over time of the system parameter.

33. The system of any of claims 20 to 32, wherein the processor is further adapted to provide amplitude and/or phase compensation of at least one of the local signal, the received signal and the correlation signal based on a third estimate of the at least one system parameter during the first time period,

wherein the third estimate is based upon the determination of which of the first and second estimates was nearer the true value and/or true evolution over time of the at least one system parameter during the first time period.