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

• US 20050116858A1
• Filed: 11/04/2004
• Published: 06/02/2005
• Est. Priority Date: 11/12/2003
• Status: Active Grant

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Odamura, Satoshi
• Granted Patent: US 7,245,256 B2
• Time in Patent Office: Days
• US Class Current: 342/357.620
• 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.

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

6. 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 judgment.

7. The position-finding system as set forth in claim 6, 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.

8. 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.

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

10. 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.

11. The server as set forth in claim 10, 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.

12. The server as set forth in claim 10, 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.

13. 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.

14. The mobile terminal as set forth in claim 13, 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.

15. The mobile terminal as set forth in claim 13, 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.

16. The mobile terminal as set forth in claim 13, 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.

17. The mobile terminal as set forth in claim 16, 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.

18. The mobile terminal as set forth in claim 13, 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.

19. The mobile terminal as set forth in claim 13, wherein said mobile terminal is comprised of a mobile phone.

20. 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.

21. The GPS receiver as set forth in claim 20, 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.

22. The GPS receiver as set forth in claim 20, 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.

23. The GPS receiver as set forth in claim 20, 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.

24. The GPS receiver m as set forth in claim 23, 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.

25. The GPS receiver as set forth in claim 20, 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.

26. 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.

27. The method as set forth in claim 26, 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.

28. The method as set forth in claim 26, 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.

29. The method as set forth in claim 26, 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.

30. The method as set forth in claim 29, 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.

31. The method as set forth in claim 26, 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.

32. 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.

33. The program as set forth in claim 32, 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.

34. The program as set forth in claim 32, wherein said three-dimensional position-finding and said two-dimensional position-finding is selected in accordance with accuracy of said altitude data.

35. The program as set forth in claim 32, 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 judgment.

36. The program as set forth in claim 35, 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.

37. The program as set forth in claim 32, 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.