Position measurement device, terminal provided therewith, and position measurement method

• US 20030130792A1
• Filed: 02/26/2003
• Published: 07/10/2003
• Est. Priority Date: 09/18/2001
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Mori, Shinichiro
• Granted Patent: US 6,763,302 B2
• Time in Patent Office: Days
• US Class Current: 701/213
• CPC Class Codes: G01C 21/165 combined with non-inertial navigation instruments
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: G01S 19/49 whereby the further system is an inertial position system, e.g. loosely-coupled
• CPC Class Codes: G01S 19/50 whereby the position solution is constrained to lie upon a particular curve or surface, e.g. for locomotives on railway tracks

Abstract

The present invention provides a position measurement device which can measure a position even in the case where the number of satellites necessary for position measurement with GPS cannot be ensured. In the case where the number of satellites necessary for position measurement cannot be acquired, a first position measurement device according to the present invention measures the position by finding the displacement distance from the nearest position, on the basis of three-dimensional acceleration detected by a three-dimensional acceleration sensor, for example.

Claims

1. A position measurement device comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point; and

a distance measuring unit for measuring a displacement distance from a prescribed position obtained by said position measuring unit;

wherein said position measuring unit measures the position of the measurement point based on of said displacement distance and at least one piece of radio wave information received from the satellites, the number of which is less than said prescribed number, in the case where the number of satellites from which radio wave information can be received is less than said prescribed number.

2. The position measurement device, according to claim 1, comprising an acceleration detecting unit for detecting the acceleration in each of three dimensions;

wherein said distance measuring unit measures the displacement distance from the prescribed position measured by said position measuring unit on the basis of said acceleration measured by said acceleration detecting unit.

3. The position measurement device, according to claim 1, wherein said position measuring unit measures the position of said measurement point, based on said displacement distance and two or more pieces of radio wave information received from two or more satellites, the number of which is less than said prescribed number.

4. The position measurement device, according to claim 1, wherein said position measuring unit measures the position of said measurement point, based on said displacement distance and one piece of radio wave information received from one satellite, the number of which is less than said prescribed number.

5. The position measurement device, according to claim 4, wherein said position measuring unit determines the position of the measurement point to be the center of a circle constituting a first position group where a second position group, that is a set of the positions of the measurement point based on said displacement distance, overlaps a third position group, that is a set of positions of the measurement point based on said radio wave information.

6. The position measurement device, according to claim 5, wherein said position measuring unit determines the radius of said circle to be the error of said determined position.

7. The position measurement device, according to claim 1, comprising a direction measuring unit for measuring the displacement direction from the prescribed position detected by said position measuring unit;

wherein, said position measuring unit measures the position of the measurement point based on said displacement distance and said displacement direction in the case where not even one piece of radio wave information is received from a satellite.

8. The position measurement device, according to claim 7, comprising an acceleration detecting unit for detecting the acceleration in each of three dimensions;

wherein said direction measuring unit measures said displacement direction on the basis of the acceleration detected by said acceleration detecting unit.

9. The position measurement device, according to claim 7, comprising an angular velocity detecting unit for detecting the angular velocity in each of three dimensions;

wherein said direction measuring unit measures said displacement direction on the basis of the angular velocity detected by said angular velocity detecting unit.

10. A position measurement device comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point; and

a distance and direction measuring unit for measuring a displacement distance and displacement direction from a prescribed position obtained by said position measuring unit;

wherein said position measuring unit measures the position of the measurement point on the basis of said displacement distance and said displacement direction, in the case where the number of satellites from which radio wave information can be received is less than said prescribed number.

11. The position measurement device, according to claim 10, comprising an acceleration detecting unit for detecting the acceleration in each of three dimensions;

wherein said distance measuring unit measures the displacement distance and displacement direction on the basis of the acceleration measured by said acceleration detecting unit.

12. The position measurement device, according to claim 10, comprising:

an acceleration detecting unit for detecting the acceleration in each of three dimensions; and

an angular velocity detecting unit for detecting the angular velocity in each of three dimensions;

wherein said distance measuring unit measures the displacement distance on the basis of the acceleration measured by said acceleration detecting unit, and the displacement direction on the basis of the angular velocity detected by said angular velocity detecting unit.

13. A portable terminal having a position measurement device, the position measurement comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point; and

a distance measuring unit for measuring a displacement distance from a prescribed position obtained by said position measuring unit;

wherein said position measuring unit measures the position of the measurement point based on of said displacement distance and at least one piece of radio wave information received from the satellites, the number of which is less than said prescribed number, in the case where the number of satellites from which radio wave information can be received is less than said prescribed number.

14. A position measurement method comprising the steps of:

finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point;

measuring the displacement distance from a prescribed position obtained in said first step; and

measuring the position of the measurement point, based on at least one piece of radio wave information received from the satellites, the number of which less than said prescribed number, and on said displacement distance, in the case where the number of satellites, from which radio wave information can be received, is less than said prescribed number.

15. An azimuth measurement device comprising:

a plurality of azimuth measuring units disposed in mutually separate locations and detecting respectively the intensities of magnetic fields, including at least geomagnetism, to measure azimuth; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism on the basis of a comparison of the intensities of magnetic fields detected by each of said plurality of azimuth measuring units.

16. The azimuth measurement device, according to claim 15, wherein said determining unit determines that no external magnetic fields are present in the case where the intensities of the magnetic fields detected by each of said plurality of azimuth measuring units are approximately the same, and determines that external magnetic fields are present in the case where there is a difference that is greater than or equal to a prescribed value in the intensities of said magnetic fields.

17. An azimuth measurement device comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point;

an azimuth measuring unit for detecting the intensities of magnetic fields, at least including geomagnetism;

a data storing unit for storing the geomagnetic intensities corresponding to a plurality of positions; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism at the position measured by-said position measuring unit, on the basis of the intensity of the magnetic field detected by said azimuth measuring unit at said position and the geomagnetic intensity corresponding to said position, that is stored in said data storing unit.

18. A portable terminal having an azimuth measurement device, the azimuth measurement device comprising:

a plurality of azimuth measuring units disposed in mutually separate locations and detecting respectively the intensities of magnetic fields, including at least geomagnetism, to measure azimuth; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism on the basis of a comparison of the intensities of magnetic fields detected by each of said plurality of azimuth measuring units.

19. A portable terminal having an azimuth measurement device, the azimuth measurement device comprising:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point;

an azimuth measuring unit for detecting the intensities of magnetic fields, at least including geomagnetism;

a data storing unit for storing the geomagnetic intensities corresponding to a plurality of positions; and

a determining unit for determining the presence of external magnetic fields other than geomagnetism at the position measured by said position measuring unit, on the basis of the intensity of the magnetic field detected by said azimuth measuring unit at said position and the geomagnetic intensity corresponding to said position, that is stored in said data storing unit.

20. A communication system comprising a server and a terminal able to communicate with the server through a network,

wherein said terminal comprises:

a position measuring unit for finding two-dimensional position information, at least including latitude and longitude, of a measurement point, on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point;

an azimuth measuring unit for detecting the intensity of magnetic field, at least including geomagnetism; and

a first communicating unit for sending the position measured by said position measuring unit and the intensity of the magnetic field at that position to said server, and receiving a response from the server; and

wherein said server comprises;

a data storing unit for storing data of the geomagnetic intensities corresponding to a plurality of positions;

a determining unit for determining the presence of external magnetic fields other than geomagnetism at said position on the basis of said measured position and said magnetic field intensity sent from said terminal, and the geomagnetic intensity corresponding to the position stored in said data storing unit; and

a second communicating unit for receiving said position and said magnetic field intensity sent from said terminal, and returning, in response thereto, said determination results to said terminal.

21. A method for detecting external magnetic fields comprising the steps of:

detecting the intensities of the magnetic fields, at least including geomagnetism, using a plurality of magnetism detecting units disposed in mutually separate locations; and

determining the presence of external magnetic fields other than geomagnetism on the basis of a comparison of the intensities of the magnetic fields detected by each of said plurality of magnetism detecting units.

22. A method for detecting external magnetic fields comprising:

finding two-dimensional position information, at least including latitude and longitude, of a measurement point on the basis of radio wave information received from a prescribed number, that is three or more, of satellites, and measuring the position of the measurement point;

detecting the intensities of magnetic fields, at least including geomagnetism; and

determining the presence of external magnetic fields other than geomagnetism at the position on the basis of a comparison of the intensities of the magnetic fields detected in said second step at the position measured in said first step, with the geomagnetic intensity corresponding to that position.