Method and apparatus for substituting sensor data for satellite signal in GPS receiver

• US 6,691,031 B2
• Filed: 05/31/2002
• Issued: 02/10/2004
• Est. Priority Date: 05/31/2002
• Status: Expired due to Term

• Current Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: Magellan Corporation (Thales SA)
• Inventors: Lokshin, Anatole M., Kulik, Viktor, Efseaff, John M.
• Primary Examiner(s): Cuchlinski, Jr., William A.
• Assistant Examiner(s): Hernandez, Olga
• Application Number:
  US10/158,973
• Publication Number:
  US 20030225514A1
• Time in Patent Office: 620 Days
• Field of Search: 701/213, 731/78.R, 342/83, 342/98, 342/100
• US Class Current: 701/213
• CPC Class Codes: G01S 19/235 Calibration of receiver components
• CPC Class Codes: H03L 1/026 by using a memory for digitally storing correction values H03L1/025 takes precedence

Abstract

Embodiments of the present invention are directed to a method and apparatus for substituting temperature sensor data for a satellite signal in a GPS receiver. In one embodiment of the present invention, a mathematical model of a GPS receiver'"'"'s clock'"'"'s response to temperature change is maintained. In one embodiment, the mathematical model is a third order polynomial. In one embodiment, when a GPS receiver has contact with at least four GPS satellites, the receiver collects data on changes in temperature and resulting changes in the GPS receiver'"'"'s clock frequency. The data is incorporated into the GPS receiver'"'"'s mathematical model. In one embodiment, the data is incorporated by modifying one or more coefficients in the mathematical model. In one embodiment, if a GPS receiver only has contact with three GPS satellites, changes in temperature and the mathematical model are used to estimate an adjustment to the signal generated by the clock.

Claims

1. A method of calculating a GPS solution comprising:

maintaining a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

generating an estimated frequency value using said mathematical model; and

substituting said estimated frequency value for a set of satellite data;

wherein said step of generating comprises;

storing a known temperature;

storing a known frequency wherein said known frequency is calculated from a full GPS solution at said known temperature;

calculating a difference between a first value generated by said mathematical model at a current temperature and a second value generated by said mathematical model at said known temperature;

adding said difference to said known frequency.

2. The method of claim 1, wherein said known frequency is the most recent frequency calculated from the full GPS solution.

3. A method of calculating a GPS solution comprising:

maintaining a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

generating an estimated frequency value using said mathematical model; and

substituting said estimated frequency value for a set of satellite data;

wherein said model is a third order polynomial.

4. A method of calculating a GPS solution comprising:

maintaining a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

generating an estimated frequency value using said mathematical model; and

substituting said estimated frequency value for a set of satellite data;

wherein said step of maintaining comprises;

calculating a difference between a first frequency calculated from the full GPS solution and a second frequency calculated using said mathematical model; and

adjusting said mathematical model using said difference.

5. The method of claim 4, wherein said step of maintaining further comprises:

storing said difference in a difference table; and

determining whether said difference table contains sufficient entries to reliably calculate an adjustment to the mathematical model.

6. The method of claim 5, wherein said difference table does not have a constant temperature step.

7. The method of claim 4, wherein said step of calculating and said step of adjusting are preformed periodically.

8. The method of claim 4, wherein said step of adjusting adjusts said mathematical model based on a previously performed adjustment.

9. A method of calculating a GPS solution comprising:

maintaining a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

generating an estimated frequency value using said mathematical model; and

substituting said estimated frequency value for a set of satellite data;

further comprising;

fixing an altitude value at a last known value.

10. A method of calculating a GPS solution comprising:

maintaining a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

generating an estimated frequency value using said mathematical model; and

substituting said estimated frequency value for a set of satellite data;

further comprising;

determining an altitude value from a sensor data item.

11. The method of claim 10, wherein said step of determining comprises:

calculating a change between said sensor data item and a second sensor data item; and

converting said change into an altitude change.

12. A GPS solution calculator comprising:

a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

a model maintaining unit configured to maintain said mathematical model;

a frequency generator configured to generate an estimated frequency value using said mathematical model; and

a substitution unit configured to substitute said estimated frequency value for a set of satellite data;

wherein said frequency generator comprises;

a first storage unit configured to store a known temperature;

a second storage unit configured to store a known frequency wherein said known frequency is calculated at said known temperature;

a calculator configured to calculate a difference between a first value generated by said mathematical model at a current temperature and a second value generated by said mathematical model at said known temperature;

an adding unit configured to add said difference to said known frequency.

13. The GPS solution calculator of claim 12, wherein said known frequency is the most recently calculated frequency from the full GPS solution.

14. A GPS solution calculator comprising:

a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

a model maintaining unit configured to maintain said mathematical model;

a frequency generator configured to generate an estimated frequency value using said mathematical model; and

a substitution unit configured to substitute said estimated frequency value for a set of satellite data;

wherein said model is a third order polynomial.

15. A GPS solution calculator comprising:

a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

a model maintaining unit configured to maintain said mathematical model;

a frequency generator configured to generate an estimated frequency value using said mathematical model; and

a substitution unit configured to substitute said estimated frequency value for a set of satellite data;

wherein said model maintaining unit comprises;

a calculator configured to calculate a difference between a first frequency calculated from the full GPS solution and a second frequency calculated using said mathematical model; and

an adjustment unit configured to adjust said mathematical model using said difference.

16. The GPS solution calculator of claim 15, wherein said model maintaining unit further comprises:

a difference table;

a storage unit configured to store said difference in said difference table; and

a determiner configured to determine whether said difference table contains sufficient entries to reliably calculate an adjustment to the mathematical model.

17. The GPS solution calculator of claim 16, wherein said difference table does not have a constant temperature step.

18. The GPS solution calculator of claim 15, wherein said calculator and said adjustment unit are further configured to operate periodically.

19. The GPS solution calculator of claim 15, wherein said adjustment unit is further configured to adjust said mathematical model based on a previously performed adjustment.

20. A GPS solution calculator comprising:

a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

a model maintaining unit configured to maintain said mathematical model;

a frequency generator configured to generate an estimated frequency value using said mathematical model; and

a substitution unit configured to substitute said estimated frequency value for a set of satellite data;

further comprising;

an altitude determiner configured to fix an altitude value at a last known value.

21. A GPS solution calculator comprising:

a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

a model maintaining unit configured to maintain said mathematical model;

a frequency generator configured to generate an estimated frequency value using said mathematical model; and

a substitution unit configured to substitute said estimated frequency value for a set of satellite data;

further comprising;

an altitude determiner configured to determine an altitude value from a sensor data item.

22. The GPS solution calculator of claim 21, wherein said altitude determiner comprises:

a calculator configured to calculate a change between said sensor data item and a second sensor data item; and

a conversion unit configured to convert said change into an altitude change.

23. A computer program product comprising:

a computer usable medium having computer readable program code embodied therein configured to calculate a GPS solutions said computer program product comprising;

computer readable code configured to cause a computer to maintain a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

computer readable code configured to cause a computer to generate an estimated frequency value using said mathematical model; and

computer readable code configured to cause a computer to substitute said estimated frequency value for a set of satellite data;

wherein said computer readable code configured to cause a computer to generate comprises;

computer readable code configured to cause a computer to store a known temperatures;

computer readable code configured to cause a computer to store a known frequency wherein said known frequency is calculated at said known temperature;

computer readable code configured to cause a computer to calculate a difference between a first value generated by said mathematical model at a current temperature and a second value generated by said mathematical model at said known temperature;

computer readable code configured to cause a computer to add said difference to said known frequency.

24. The computer program product of claim 23, wherein said known frequency is the most recently calculated frequency from the full GPS solution.

25. A computer program product comprising:

a computer usable medium having computer readable program code embodied therein configured to calculate a GPS solution said computer program product comprising;

computer readable code configured to cause a computer to maintain a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

computer readable code configured to cause a computer to generate an estimated frequency value using said mathematical model; and

computer readable code configured to cause a computer to substitute said estimated frequency value for a set of satellite data;

wherein said model is a third order polynomial.

26. A computer program product comprising:

a computer usable medium having computer readable program code embodied therein configured to calculate a GPS solution, said computer program product comprising;

computer readable code configured to cause a computer to maintain a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

computer readable code configured to cause a computer to generate an estimated frequency value using said mathematical model; and

computer readable code configured to cause a computer to substitute said estimated frequency value for a set of satellite data;

wherein said computer readable code configured to cause a computer to maintain comprises;

computer readable code configured to cause a computer to calculate a difference between a first frequency calculated from the full GPS solution and a second frequency calculated using said mathematical model; and

computer readable code configured to cause a computer to adjust said mathematical model using said difference.

27. The computer program product of claim 26, wherein said computer readable code configured to cause a computer to maintain further comprises:

computer readable code configured to cause a computer to store said difference in said difference table; and

computer readable code configured to cause a computer to determine whether said difference table contains sufficient entries to reliably calculate an adjustment to the mathematical model.

28. The computer program product of claim 27, wherein said difference table does not have a constant temperature step.

29. The computer program product of claim 26, wherein said computer readable code configured to cause a computer to calculate is further configured to cause a computer to calculate periodically and wherein said computer readable code configured to cause a computer to adjust is further configured to cause a computer to adjust periodically.

30. The computer program product of claim 26, wherein said computer readable code configured to cause a computer to adjust is further configured to cause a computer to adjust said mathematical model based on a previously performed adjustment.

31. A computer program product comprising:

a computer usable medium having computer readable program code embodied therein configured to calculate a GPS solution said computer program product comprising;

computer readable code configured to cause a computer to maintain a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

computer readable code configured to cause a computer to generate an estimated frequency value using said mathematical model; and

computer readable code configured to cause a computer to substitute said estimated frequency value for a set of satellite data;

further comprising;

computer readable code configured to cause a computer to fix an, altitude value at a last known value.

32. A computer program product comprising:

a computer usable medium having computer readable program code embodied therein configured to calculate a GPS solution said computer program product comprising;

computer readable code configured to cause a computer to maintain a mathematical model of a relation between a frequency of a crystal oscillator and a temperature;

computer readable code configured to cause a computer to generate an estimated frequency value using said mathematical model; and

computer readable code configured to cause a computer to substitute said estimated frequency value for a set of satellite data;

further comprising;

computer readable code configured to cause a computer to determine an altitude value from a sensor data item.

33. The computer program product of claim 32, wherein said computer readable code configured to cause a computer to determine comprises:

computer readable code configured to cause a computer to calculate a change between said sensor data item and a second sensor data item; and

computer readable code configured to cause a computer to convert said change into an altitude change.