Receiver of a satellite positioning system and associated method

• US 6,549,850 B2
• Filed: 07/02/2001
• Issued: 04/15/2003
• Est. Priority Date: 07/02/2001
• Status: Active Grant

• Current Assignee: Suunto Oy (Anta International Group Holdings Ltd.)
• Original Assignee: Suunto Oy (Anta International Group Holdings Ltd.)
• Inventors: Punkka, Eero, Lindman, Erik, Karttunen, Vesa
• Primary Examiner(s): Zanelli, Michael J.
• Application Number:
  US09/897,634
• Publication Number:
  US 20030004639A1
• Time in Patent Office: 652 Days
• Field of Search: 701/213, 701/214, 701/226, 342/357.12, 342/357.15
• US Class Current: 701/213
• 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

Abstract

A receiver of a satellite positioning system, the receiver being capable of receiving signals from satellites, determining an estimated latitude and determining an estimated longitude. The receiver being responsive to the estimated latitude, estimated longitude and information indicating orbits of the satellites for identifying a group of available satellites, for performing a search for signals transmitted by satellites which belong to the group of satellites, and for calculating the positional coordinates of the receiver based on signals received from satellites which belong to the group of satellites.

Claims

1. A method for determining positional coordinates of a receiver receiving signals from satellites in a satellite navigation system, said method comprising:

carrying out measurements in order to obtain a measurement result describing properties of a magnetic field at a location of the receiver,

obtaining an estimated latitude based on said measurement result,

comparing a local time indicated by a clock in said receiver and a satellite time in order to identify a time zone where said receiver is located,

obtaining an estimated longitude based on the identified time zone,

identifying a group of available satellites based on the estimated latitude, the estimated longitude and information indicating orbits of the satellites within said system,

performing a search for signals transmitted by satellites which belong to said group of available satellites, and

determining the positional coordinates of the receiver based on signals received from the satellites which belong to said group of available satellites.

2. The method of claim 1, wherein

the step of carrying out measurements is carried out by measuring an angle between a direction of said magnetic field and a horizontal plane at the location of the receiver, and

the step of obtaining an estimated latitude is carried out by selecting said measured angle as the estimated latitude of the receiver.

3. The method of claim 1, wherein

the step of carrying out measurements is carried out by measuring an angle between a direction of said magnetic field and a horizontal plane at the location of the receiver, and

the step of obtaining an estimated latitude is carried out by using said measured angle to retrieve the estimated latitude from a table containing different angles and corresponding latitude values.

4. The method of claim 1, wherein

the step of carrying out measurements is carried out by measuring a field strength of said magnetic field in a horizontal direction in order to obtain said measurement result, and

the step of obtaining the estimated latitude is carried out by comparing the obtained measurement result to predetermined field strength values with corresponding latitude values in order to obtain a preliminary latitude of said receiver.

5. The method of claim 1, wherein

the step of carrying out measurements is carried out by measuring a field strength of said magnetic field in a vertical direction in order to obtain said measurement result, and

the step of obtaining the estimated latitude is carried out by comparing the measurement result to predetermined field strength values with corresponding latitude values in order to obtain a preliminary latitude of said receiver.

6. A receiver of a satellite positioning system comprising:

reception means for receiving signals transmitted by satellites,

means for measuring a magnetic field at a location of said receiver in order to obtain a measurement result describing properties of said magnetic field and for obtaining an estimated latitude based on the measurement result,

a clock for keeping track of a local time at the location of the receiver, and

means for comparing the local time indicated by said clock and a satellite time in order to identify a time zone where said receiver is located and for obtaining an estimated longitude based on said identified time zone,

said receiver identifying a group of available satellites from the estimated latitude, the estimated longitude, and information indicating orbits of the satellites, performing a search for signals transmitted by satellites which belong to said group of satellites, and calculating the positional coordinates of the receiver based on signals received from satellites which belong to said group of satellites.

7. The receiver of claim 6, wherein said means for measuring the magnetic field includes means for measuring an angle between the direction of said magnetic field and a horizontal plane at the location of the receiver, whereby the measured angle is selected as the estimated latitude.

8. The receiver of claim 6, wherein said means for measuring the magnetic field includes means for measuring a field strength of said magnetic field in a horizontal direction in order to obtain said measurement result, and wherein said receiver is adapted to compare the measurement result to predetermined field strength values with corresponding latitude values in order to identify a predetermined field strength value which substantially equals the measurement result, and where the latitude value corresponding to the identified field strength value is selected as a preliminary latitude value.

9. The receiver of claim 6, wherein said means for measuring the magnetic field of the earth includes means for measuring a field strength of said magnetic field in a vertical direction in order to obtain said measurement result, and wherein said receiver is adapted to compare the measurement result to predetermined field strength values with corresponding latitude values in order to identify a predetermined field strength value which substantially equals the measurement result, and where the latitude value corresponding to the identified field strength value is selected as a preliminary latitude value.

10. The receiver of claim 6, wherein said receiver further comprises means for measuring the direction of a gravitational force of the earth at the location of the receiver and for using said measured direction in order to determine a direction of a horizontal plane.

11. The receiver of claim 6 wherein said receiver is a portable receiver having an energy source including a battery.

12. The receiver of claim 6 wherein said receiver is a wearable receiver having an energy source including a battery.

13. A receiver for determining a location, said receiver forming at least part of a satellite positioning system, said satellite positioning system having a plurality of groups of satellites, each satellite transmitting signals including a satellite time, said receiver comprising:

a reception device adapted to receive signals transmitted by said satellites,

a clock adapted to track a local time at said location of the receiver,

an electronic compass providing a measured value of a magnetic field of the earth, and

a microcontroller,

a memory having a program stored therein, said program having steps including;

estimating a latitude based on said measured value,

estimating a longitude by comparing the local time with said satellite time obtained from the signals received by the reception device,

selecting a group of available satellites based on the estimated latitude and the estimated longitude, and

searching for signals from the group of available satellites.

14. The receiver of claim 13 wherein the steps further include the step of calculating positional coordinates of the receiver based on signals received from the group of available satellites, said receiver further including a display adapted to display said positional coordinates.

15. The receiver of claim 13 further comprising a user interface for setting the clock to the local time.

16. The receiver of claim 13 wherein the electronic compass is adapted to measure an angle of the magnetic field and wherein the step of estimating the latitude includes converting said angle into an estimated longitude.

17. The receiver of claim 13 wherein the electronic compass measures a strength of the magnetic field and wherein the step of estimating the latitude includes converting the measured strength of the magnetic field into an estimated longitude.

18. The receiver of claim 13 further comprising a detector for measuring a direction of a gravitational force.

19. The receiver of claim 13 wherein the receiver is a portable receiver.