USING MAGNETOMETER WITH A POSITIONING SYSTEM

• US 20110063167A1
• Filed: 09/15/2009
• Published: 03/17/2011
• Est. Priority Date: 09/15/2009
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Garin, Lionel J., Gum, Arnold J.
• Application Number:
  US12/560,207
• Publication Number:
  US 20110063167A1
• Time in Patent Office: Days
• US Class Current: 342/357.65
• CPC Class Codes: G01C 17/30 Earth-inductor compasses
• CPC Class Codes: G01C 21/20 Instruments for performing navigational calculations G01C21/24, G01C21/26 take precedence
• CPC Class Codes: G01S 19/252 Employing an initial estimate of location in generating assistance data
• CPC Class Codes: G01S 19/26 involving a sensor measurement for aiding acquisition or tracking
• CPC Class Codes: G01S 19/28 Satellite selection

Abstract

A mobile station determines an approximate latitude using a measured feature of the Earth'"'"'s magnetic field. An approximate longitude may also be determined. The mobile station uses the approximate latitude and longitude, if determined, to assist in determining a position fix for the mobile station, e.g., by determining a list of visible satellites in a satellite positioning system (SPS) during search and acquisition of satellite signals and/or using the approximate position as a seed position in the position computation. The feature of the Earth'"'"'s magnetic field may be, e.g., inclination or vertical intensity, and may be determined using data from a three-dimensional magnetometer and a three-dimensional accelerometer. An instantaneous value of the magnetic field feature may be averaged to reduce the affects of motion and the presences of large metallic masses.

Claims

1. A method comprising:

determining an approximate latitude of a mobile station using a mobile station processor based on at least one feature of the Earth'"'"'s magnetic field measured by the mobile station;

determining an approximate longitude of the mobile station using the mobile station processor; and

storing the approximate latitude and the approximate longitude and using the approximate latitude and the approximate longitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix.

2. The method of claim 1, wherein using the approximate latitude and the approximate longitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix comprises determining whether to use a last position fix for the mobile station as a seed position for the search for satellites by comparing the approximate latitude and the approximate longitude to a last position fix.

3. The method of claim 1, wherein using the approximate latitude and the approximate longitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix comprises using the approximate latitude and the approximate longitude as a seed position for the search for satellites.

4. The method of claim 1, wherein the at least one feature of the Earth'"'"'s magnetic field is selected from inclination angle and vertical intensity.

5. The method of claim 1, wherein determining an approximate latitude of a mobile station using a mobile station processor based on at least one feature of the Earth'"'"'s magnetic field measured by the mobile station comprises:

collecting data from a three-dimensional magnetometer inside the mobile station;

determining a value of the at least one feature of the Earth'"'"'s magnetic field using the mobile station processor based on the collected data from the three-dimensional magnetometer; and

converting the value of the at least one feature into an approximate latitude.

6. The method of claim 5, wherein determining an approximate latitude of a mobile station using at least one feature of the Earth'"'"'s magnetic field measured by the mobile station further comprises:

collecting local vertical data; and

using the local vertical data with the collected data from the three-dimensional magnetometer to determine the value of the at least one feature of the Earth'"'"'s magnetic field.

7. The method of claim 5, wherein determining an approximate latitude of a mobile station using at least one feature of the Earth'"'"'s magnetic field measured by the mobile station further comprises:

collecting data from a three-dimensional accelerometer inside the mobile station, the three-dimensional accelerometer having a known orientation with respect to the three-dimensional magnetometer; and

using the collected data from the three-dimensional accelerometer with the collected data from the three-dimensional magnetometer to determine the value of the at least one feature of the Earth'"'"'s magnetic field.

8. The method of claim 7, further comprising filtering the data collected from the three-dimensional accelerometer and filtering the data collected from the three-dimensional magnetometer and using the filtered data collected from the three-dimensional accelerometer and the filtered data collected from the three-dimensional magnetometer to determine the value of the at least one feature of the Earth'"'"'s magnetic field.

9. The method of claim 7, wherein using the collected data from the three-dimensional accelerometer with the collected data from the three-dimensional magnetometer to determine the value of the at least one feature of the Earth'"'"'s magnetic field comprises:

generating an instantaneous value of the at least one feature of the Earth'"'"'s magnetic field using the mobile station processor based on the collected data from the three-dimensional magnetometer with the collected data from the three-dimensional accelerometer; and

averaging the instantaneous value to produce the value of the at least one feature of the Earth'"'"'s magnetic field.

10. The method of claim 7, further comprising:

detecting acceleration perturbations in the data collected from the three-dimensional accelerometer;

detecting magnetic perturbations in the data collected from the three-dimensional magnetometer; and

preventing the collected data from the three-dimensional accelerometer and the collected data from the three-dimensional magnetometer from being used to determine the value of the at least one feature of the Earth'"'"'s magnetic field when at least one of detected acceleration perturbations and detected magnetic perturbations are outside a range.

11. The method of claim 1, wherein determining an approximate longitude of the mobile station using the mobile station processor is based on a time difference between a local time zone and a reference time zone and comprises:

storing a longitude from the reference time zone;

determining the time difference between the local time zone and the reference time zone;

converting the time difference to a longitude difference; and

using the longitude difference and the longitude from the reference time zone to determine the approximate longitude of the mobile station.

12. The method of claim 11, wherein determining the time difference between the local time zone and the reference time zone comprises determining the number of times zones between the local time zone and the reference time zone.

13. The method of claim 11, wherein determining the time difference between the local time zone and the reference time zone comprises calculating the difference in time at the local time zone and time at the reference time zone.

14. The method of claim 1, wherein determining an approximate longitude of the mobile station using the mobile station processor is based on a received area code or country code signal.

15. A mobile station comprising:

a three-dimensional magnetometer;

a three-dimensional accelerometer;

a satellite positioning system receiver;

a processor connected to receive data from the satellite positioning system receiver, data from the three-dimensional magnetometer and data from the three-dimensional accelerometer;

memory connected to the processor; and

software held in the memory and run in the processor to determine a value of the at least one feature of the Earth'"'"'s magnetic field using the data from the three-dimensional magnetometer and the data from the three-dimensional accelerometer and to determine an approximate latitude using the value of the at least one feature of the Earth'"'"'s magnetic field, and to use the approximate latitude in the search for satellites in a satellite positioning system (SPS) that are visible to the satellite positioning system receiver during search and acquisition of satellite signals for a position fix.

16. The mobile station of claim 15, further comprising a receiver that receives an external local time signal, wherein software held in the memory and run in the processor causes the processor to determine a time difference between the local time zone obtained from the external local time signal and a reference time zone, to determine an approximate longitude using the time difference, and to use the approximate longitude to determine a position fix for the mobile station.

17. The mobile station of claim 16, wherein a longitude from the reference time zone is stored in the memory, the software held in the memory and run in the processor causes the processor to convert the time difference to a longitude difference and combines the longitude difference and the stored longitude to determine the approximate longitude.

18. The mobile station of claim 16, wherein the software held in the memory and run in the processor causes the processor to determine the time difference between the local time zone obtained from the external local time signal and the reference time zone by at least one of determining the number of times zones between the local time zone and the reference time zone and calculating the difference in time at the local time zone and time at the reference time zone.

19. The mobile station of claim 15, further comprising a receiver that receives an external area code or country code signal, wherein the software held in the memory and run in the processor causes the processor to determine an approximate longitude based on the area code or country code signal.

20. The mobile station of claim 15, wherein the at least one feature of the Earth'"'"'s magnetic field is selected from inclination angle and vertical intensity.

21. The mobile station of claim 15, further comprising a first filter that filters the data from the three-dimensional accelerometer and a second filter that filters the data from the three-dimensional magnetometer before the processor determines a value of the at least one feature of the Earth'"'"'s magnetic field.

22. The mobile station of claim 21, wherein software held in the memory and run in the processor causes the processor to be the first filter and the second filter.

23. The mobile station of claim 15, wherein the processor determines the value of the at least one feature of the Earth'"'"'s magnetic field by generating an instantaneous value of the at least one feature of the Earth'"'"'s magnetic field and filters the instantaneous value to produce the value of the at least one feature of the Earth'"'"'s magnetic field.

24. The mobile station of claim 15, wherein software held in the memory and run in the processor causes the processor to detect acceleration perturbations in the data from the three-dimensional accelerometer and detect magnetic perturbations in the data from the three-dimensional magnetometer and prevent the data from the three-dimensional accelerometer and the data from the three-dimensional magnetometer from being used to determine a value of the at least one feature of the Earth'"'"'s magnetic field when at least one of detected acceleration perturbations and detected magnetic perturbations are outside a range.

25. The mobile station of claim 15, wherein software held in the memory and run in the processor causes the processor to use the approximate latitude in the search for satellites in a satellite positioning system (SPS) that are visible to the satellite positioning system receiver during search and acquisition of satellite signals for a position fix comprises software run in the processor causing the processor to determine whether to use a last position fix for the mobile station as a seed position for the search for satellites by comparing the approximate latitude to a last position fix.

26. The mobile station of claim 15, wherein software held in the memory and run in the processor causes the processor to use the approximate latitude in the search for satellites in a satellite positioning system (SPS) that are visible to the satellite positioning system receiver during search and acquisition of satellite signals for a position fix comprises software run in the processor causing the processor to use the approximate latitude as a seed position for the search for satellites.

27. A mobile station comprising:

means for measuring at least one feature of the Earth'"'"'s magnetic field;

means for determining an approximate latitude of the mobile station using the measured at least one feature of the Earth'"'"'s magnetic field;

means for determining an approximate longitude of the mobile station; and

means for using the approximate latitude and the approximate longitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix.

28. The mobile station of claim 27, wherein the means for measuring at least one feature of the Earth'"'"'s magnetic field comprises a three-dimensional magnetometer and a three-dimensional accelerometer that has a known orientation with respect to the three-dimensional magnetometer, and a processor that receives data from the three-dimensional magnetometer and the three-dimensional accelerometer and calculates a value for the at least one feature of the Earth'"'"'s magnetic field.

29. The mobile station of claim 28, further comprising a means for filtering out perturbation effects of metallic masses on the three-dimensional magnetometer and motion of the three-dimensional accelerometer.

30. The mobile station of claim 28, further comprising a means for detecting acceleration perturbations;

a means for detecting magnetic perturbations; and

a means to prevent the data from the three-dimensional accelerometer and the data from the three-dimensional magnetometer from being used to calculate a value for the at least one feature of the Earth'"'"'s magnetic field when at least one of detected acceleration perturbations and detected magnetic perturbations are outside a range.

31. The mobile station of claim 27, wherein the means for determining an approximate latitude of the mobile station using the measured at least one feature of the Earth'"'"'s magnetic field comprises a processor that converts the measured at least one feature of the Earth'"'"'s magnetic field into an approximate latitude.

32. The mobile station of claim 27, wherein the means for determining an approximate longitude of the mobile station comprises a clock receiver that receives a local time signal;

memory storing the longitude from the reference time zone and a processor coupled to the memory and the clock receiver, the processor determines the time difference between the local time zone determined from the local time signal received by the clock receiver and the reference time zone;

the processor converts the time difference into a longitude difference; and

combines the longitude difference and the longitude from the reference time zone to determine the approximate longitude.

33. The mobile station of claim 27, wherein the means for determining an approximate longitude of the mobile station comprises a receiver for receiving an area code or country code signal and a processor coupled to the receiver, the processor determines the approximate longitude based on the area code or country code signal received by the receiver.

34. The mobile station of claim 27, wherein the at least one feature of the Earth'"'"'s magnetic field is selected from inclination angle and vertical intensity.

35. The mobile station of claim 27, wherein the means for using the approximate latitude and the approximate longitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix determines whether to use a last position fix for the mobile station as a seed position for the search for satellites by comparing the approximate latitude and the approximate longitude to a last position fix.

36. The mobile station of claim 27, the means for using the approximate latitude and the approximate longitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix uses the approximate latitude and the approximate longitude as a seed position for the search for satellites.

37. A computer-readable medium including program code stored thereon, comprising:

program code to determine the value of at least one feature of the Earth'"'"'s magnetic field using magnetometer data referenced to a local vertical direction;

program code to determine an approximate latitude mobile station using the value of the at least one feature of the Earth'"'"'s magnetic field; and

program code to use the approximate latitude in the search for satellites in a satellite positioning system (SPS) that are visible to the mobile station during search and acquisition of satellite signals for a position fix.

38. The computer-readable medium of claim 37, further comprising program code to determine an approximate longitude using the time difference between a local time zone and a reference time zone.

39. The computer-readable medium of claim 37, further comprising program code to determine an approximate longitude using a local area code or country code.

40. The computer-readable medium of claim 37, wherein the program code to determine the value of at least one feature of the Earth'"'"'s magnetic field using magnetometer data referenced to a local vertical direction comprises program code to calculate at least one of inclination angle and vertical intensity using magnetometer data and accelerometer data.