GPS position-finding system and method of finding position of GPS terminal

• US 7,245,256 B2
• Filed: 11/04/2004
• Issued: 07/17/2007
• Est. Priority Date: 11/12/2003
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Odamura, Satoshi
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Nguyen, Nga X.
• Application Number:
  US10/980,825
• Publication Number:
  US 20050116858A1
• Time in Patent Office: 985 Days
• Field of Search: 342/357.09, 342/357.03, 342/357.11, 342/357.15, 342/357.02
• US Class Current: 342/357.62
• 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

A position-finding system is comprised of a terminal having a global positioning system (GPS) for finding a position thereof, and a server which calculates altitude data, based on terrain data in an area in which the terminal is. The terminal includes a controller which selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured, in accordance with the altitude data provided from the server.

Claims

1. A position-finding system comprising:

a terminal having a global positioning system (GPS) for finding a position thereof; and

a server which calculates an altitude of said terminal, based on terrain data in an area in which said terminal is,

said terminal including a controller which selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured, in accordance with said altitude data provided from said server,

wherein said controller selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with accuracy of said altitude data.

2. The position-finding system as set forth in claim 1, wherein said server is comprised of a first device which acquires information relating to a plurality of base stations/cells which are captured by said terminal, and a second device which makes altitude data relating to an area covered by said plurality of base stations/cells.

3. The position-finding system as set forth in claim 1, wherein said server further includes a third device which calculates a profile of altitude in an area, based on said terrain data, and makes accuracy/variance data indicative of accuracy or variance of said altitude data, based on said profile of altitude.

4. The position-finding system as set forth in claim 1, wherein said controller selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with whether there is said altitude data or not.

5. The position-finding system as set forth in claim 1, wherein said controller judges accuracy of said altitude data, based on predetermined standard, and selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with the result of judgement.

6. The position-finding system as set forth in claim 5, wherein said controller uses a difference between said altitude data and maximum or minimum altitude in a cell in which said terminal is, as said predetermined standard.

7. The position-finding system as set forth in claim 1, wherein said controller selects said three-dimensional position-finding when a position of said terminal is to be found only by said global positioning system.

8. The position-finding system as set forth in claim 1, wherein said terminal is comprised of a mobile phone.

33. The position-finding system as set forth in claim 1, wherein said server is comprised of a first device which acquires information relating to a plurality of base stations/cells which are captured by said terminal, and a second device which makes altitude data relating to an area covered by said plurality of base stations/cells and stores the altitude data in a database in which map data of the area covered by said plurality of base/stations/cells is already stored therein, and

wherein the maximum or minimum altitude in a cell is obtained from the map data stored in the database.

9. A server constituting a position-finding system together with a terminal having a global positioning system (GPS) for finding a position thereof,

wherein said server calculates altitude data, based on terrain data in an area in which said terminal is, and

said terminal selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured, in accordance with said altitude data provided from said server,

wherein said controller selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with accuracy of said altitude data.

10. The server as set forth in claim 9, wherein said server is comprised of a first device which acquires information relating to a plurality of base stations/cells which are captured by said terminal, and a second device which makes altitude data relating to an area covered by said plurality of base stations/cells.

11. The server as set forth in claim 9, wherein said server includes a third device which calculates a profile of altitude in an area, based on said terrain data, and makes accuracy/variance data indicative of accuracy or variance of said altitude data, based on said profile of altitude.

34. The server as set forth in claim 9, wherein said server is comprised of a first device which acquires information relating to a plurality of base stations/cells which are captured by said terminal, and a second device which makes altitude data relating to an area covered by said plurality of base stations/cells and stores the altitude data in a database in which map data of the area covered by said plurality of base/stations/cells is already stored therein, and

wherein the maximum or minimum altitude in a cell is obtained from the map data stored in the database.

12. A mobile terminal having a global positioning system (GPS) for finding a position thereof, comprising a controller which selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured, in accordance with altitude data calculated based on terrain data in an area in which said mobile terminal is.

13. The mobile terminal as set forth in claim 12, wherein said controller selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with whether there is said altitude data or not.

14. The mobile terminal as set forth in claim 12, wherein said controller judges accuracy of said altitude data, based on predetermined standard, and selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with the result of judgement.

15. The mobile terminal as set forth in claim 14, wherein said controller uses a difference between said altitude data and maximum or minimum altitude in a cell in which said terminal is, as said predetermined standard.

16. The mobile terminal as set forth in claim 12, wherein said controller selects said three-dimensional position-finding when a position of said mobile terminal is to be found only by said global positioning system.

17. The mobile terminal as set forth in claim 12, wherein said mobile terminal is comprised of a mobile phone.

18. A GPS receiver having a global positioning system (GPS) for finding a position thereof, comprising:

a controller which selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured, in accordance with altitude data calculated based on terrain data in an area in which said GPS receiver is; and

a database which stores minimum and maximum altitude information of a plurality of cells,

wherein said controller uses a difference between said altitude data and said maximum and minimum altitude in a cell in which said terminal is, as a predetermined standard in determining whether or not to select three-dimensional position-finding or two-dimensional position finding.

19. The GPS receiver as set forth in claim 18, wherein said controller selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with whether there is said altitude data or not.

20. The GPS receiver as set forth in claim 18, wherein said controller selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with accuracy of said altitude data.

21. The GPS receiver as set forth in claim 18, wherein said controller judges accuracy of said altitude data, based on predetermined standard, and selects one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with the result of judgment.

22. The GPS receiver as set forth in claim 18, wherein said controller selects said three-dimensional position-finding when a position of said GPS receiver is to be found only by said global positioning system.

23. A method of finding a position of a terminal in a position-finding system comprised of said terminal and a server,

said terminal including a global positioning system (GPS) for finding a position thereof;

and a controller which selects one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured,

said method comprising;

(a) calculating altitude data, based on terrain data in an area in which said terminal is, said step (a) being to be carried out by said server; and

(b) selecting one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with said altitude data, said step (b) being to be carried out by said terminal,

wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in said step (b) in accordance with accuracy of said altitude data.

24. The method as set forth in claim 23, wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in said step (b) in accordance with whether there is said altitude data or not.

25. The method as set forth in claim 23, further comprising (c) judging accuracy of said altitude data, based on predetermined standard, and wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in said step (b) in accordance with the result of judgment.

26. The method as set forth in claim 25, wherein a difference between said altitude data and maximum or minimum altitude in a cell in which said terminal is located is used as said predetermined standard.

27. The method as set forth in claim 23, wherein said three-dimensional position-finding is always selected in said step (b) when a position of said terminal is to be found only by said global positioning system.

35. The method as set forth in claim 23, further comprising:

storing the altitude data obtained in step (a) in a database in which map data of the area covered by a plurality of base/stations/cells is already stored therein, and

wherein the maximum or minimum altitude in a cell is obtained from the map data stored in the database.

28. A program for causing a controller equipped in a terminal to find a position thereof in a position-finding system comprised of said terminal and a server,

said terminal including a global positioning system (GPS) for finding a position thereof;

said controller selecting one of three-dimensional position-finding in which a position is calculated through the use of four or more satellites and two-dimensional position-finding in which a position is calculated in a circumference in which only three satellites can be captured,

said server calculating altitude data, based on terrain data in an area in which said terminal is,

steps executed by said controller in accordance with said program including selecting one of said three-dimensional position-finding and said two-dimensional position-finding in accordance with said altitude data provided from said server,

wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in accordance with accuracy of said altitude data.

29. The program as set forth in claim 28, wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in accordance with whether there is said altitude data or not.

30. The program as set forth in claim 28, wherein said steps further include judging accuracy of said altitude data, based on predetermined standard, and wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in accordance with the result of judgement.

31. The program as set forth in claim 30, wherein a difference between said altitude data and maximum or minimum altitude in a cell in which said terminal is located is used as said predetermined standard.

32. The program as set forth in claim 28, wherein said three-dimensional position-finding is always selected when a position of said terminal is to be found only by said global positioning system.