Location detection method, location detection system and location detection program

• US 6,865,394 B2
• Filed: 01/18/2002
• Issued: 03/08/2005
• Est. Priority Date: 01/31/2001
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Kuwahara, Mikio, Ogino, Atsushi, Ishifuji, Tomoaki
• Primary Examiner(s): Urban, Edward F.
• Assistant Examiner(s): PHAN, HUY Q
• Application Number:
  US10/050,856
• Publication Number:
  US 20020132625A1
• Time in Patent Office: 1,145 Days
• Field of Search: 4554561-4566, 342/450, 342/452, 342/457, 342/458, 342463-465, 342/357.01, 342/357.08, 342/357.1, 342/357.02, 342/357.13, 701/207, 701/213, 701/214
• US Class Current: 455/456.1
• CPC Class Codes: G01S 1/022 Means for monitoring or calibrating
• CPC Class Codes: G01S 5/14 Determining absolute distances from a plurality of spaced points of known location

Abstract

A positioning method, which is related to a technique to measure a correct position of a terminal by preventing time required for the position measurement, of calculating a position of a receiver according to signals from a plurality of wireless transmitters includes a first step of measuring propagation delay time of the signal from each of the wireless transmitters and calculating a position of the receiver and a standard deviation about measuring distance error, a second step of calculating a positioning error of the receiver a third step of determining, according to the positioning error calculated by the second step, wireless transmitters in directions nearer to a direction in which the positioning error is large, and a fourth step of re-detecting signals from the wireless transmitters determined by the third step and thereby re-calculating the position of the receiver.

Claims

1. A positioning method of calculating a position of a receiver according to propagation delay time of signals from a plurality of wireless transmitters, comprising:

a first step of detecting a signal from each of the wireless transmitters, obtaining a position of each of the wireless transmitters from which the signal is detected, measuring propagation delay time of the signal from each of the wireless transmitters, and calculating a position of the receiver and a standard deviation about measuring distance error associated with the measurement of the propagation delay time;

a second step of calculating a positioning error of the receiver according to the position of each of the wireless transmitters and the position of the receiver and the standard deviation calculated in said first step;

a third step of determining, according to the positioning error of the receiver calculated in said second step, wireless transmitters in directions nearer to a direction in which the positioning error is large; and

a fourth step of re-detecting signals from the wireless transmitters in directions nearer to a direction in which the positioning error is large determined in said third step and thereby re-calculating the position of the receiver.

2. A positioning method according to claim 1, further comprising a step of determining termination of the positioning operation by said fourth step according to a result of comparison between the positioning error of the receiver calculated in said second step and a predetermined value.

3. A positioning method according to claim 1, wherein said fourth step comprises

calculating a position of the receiver according to each propagation delay time measured by re-detecting a signal from each of the wireless transmitters in directions nearer to a direction in which the positioning error is large determined in said third step, each standard deviation about measuring distance error associated with the measurement of the propagation delay time, the propagation delay time of each said wireless terminal measured before the re-detection, the standard deviation calculated before the re-detection, and the position of each said wireless transmitter and

renewing the propagation delay time and the standard deviation about measuring distance error for each of the wireless transmitters in directions nearer to a direction in which the positioning error is large determined in said third step.

4. A positioning method of calculating a position of a receiver according to propagation delay time of signals from a plurality of wireless transmitters, comprising:

a first step of detecting a signal from each wireless transmitter, obtaining a position of each wireless transmitter from which the signal is detected, measuring propagation delay time of the signal from said each wireless transmitter, and calculating a position of the receiver and a standard deviation about measuring distance error associated with the measurement of the propagation delay time;

a second step of calculating a positioning error of the receiver according to the position of each wireless transmitter and the position of the receiver and the standard deviation calculated in said first step;

a third step of determining, according to the positioning error of the receiver calculated in said second step, wireless transmitters in directions nearer to a direction in which the positioning error is large; and

a step of calculating a positioning error of the receiver at re-detection of a signal from each of the wireless transmitters in directions nearer to a direction in which the positioning error is large determined in said third step and thereby calculating a required number of re-detection to re-detect signals from each of the wireless transmitters in directions nearer to a direction in which the positioning error is large; and

re-calculating the position of the receiver according to each propagation delay time measured by re-detecting a signal from each of the wireless transmitters as many times as indicated by the required number of re-detection, each standard deviation about measuring distance error associated with the measurement of the propagation delay time, the propagation delay time of each said wireless terminal measured before the re-detection, the standard deviation calculated before the re-detection, and the position of each said wireless transmitter.

5. A positioning method according to claim 4, wherein said third step determines order of the wireless transmitters in directions nearer to a direction in which the positioning error is large according to the positioning error calculated in said second step and a quotient obtained for each of the wireless transmitters in association with the standard deviation about measuring distance error in a direction cosine for the receiver.

6. A positioning system for calculating a position of a receiver according to propagation delay time of signals from a plurality of wireless transmitters, comprising:

a receiver unit for receiving a signal from each of said wireless transmitters;

a delay profile generator for generating a delay profile of a signal from said each wireless transmitter and for outputting the delay profile;

a propagation time measurement unit for analyzing the delay profile and for thereby measuring propagation delay time of the signal;

a storage unit for storing data required to calculate a position of the positioning system; and

a processing unit for controlling said receiver unit, said delay profile generator, said propagation time measurement unit, and said storage unit for processing various data used to calculate the position and for thereby conducting a positioning operation, wherein said processing unit comprises;

position calculating means for obtaining a position of said positioning system according to the propagation delay time measured by said propagation time measurement unit;

standard deviation calculating means for calculating a standard deviation about measuring distance error associated with the measurement of the propagation delay time; and

error calculating means for calculating a positioning error of said positioning system according to the position of each of said wireless transmitters, the position of said positioning system calculated by said position calculating means, and the standard deviation calculated by said standard deviation calculating means.

7. A positioning system according to claim 6, further comprising determining means for determining wireless transmitters in directions nearer to a direction in which the positioning error is large according to the positioning error calculated by said error calculating means, wherein:

said position calculating means re-calculates the position of said positioning system according to signals from said re-detected wireless transmitters in directions nearer to a direction in which the positioning error is large; and

said error calculating means re-calculates the positioning error of said positioning system using the re-calculated position of said positioning system.

8. A positioning system according to claim 6, further comprising a display unit for displaying thereon the position of said positioning system calculated by said positioning means and the positioning error calculated by said error calculating means, wherein:

said processing unit calculates an ellipse indicating a range of error according to the positioning error of said positioning system; and

said display unit displays the position of said positioning system and the positioning error by the ellipse.

9. A positioning system according to claim 8, wherein said display unit displays the position of said positioning system, the positioning error, and map information supplied from a map database.

10. A positioning system according to claim 8, wherein said display unit displays a probability of inclusion of the position of said receiver in the ellipse indicating the range of error.

11. A position information supplying method for use with a position information supplying system comprising a handset including a positioning unit for calculating a position according to propagation delay time of signals from a plurality of wireless transmitters and a position information recognizing unit for supplying the position calculated by the positioning unit, in a format recognizable by a user, wherein:

the positioning unit determines wireless transmitters in directions nearer to a direction in which the positioning error is large, re-detecting signals from the wireless transmitters in directions nearer to a direction in which the positioning error is large, re-calculating the position of the handset, and outputting information of the position to a communication network; and

the position information recognizing unit receives a result of the positioning operation received from the positioning unit via the communication network, generating information recognizable by a user by combining the result of the positioning operation with map information corresponding thereto, and outputting the information.

12. A position information supplying method according to claim 11, wherein:

the positioning unit outputs, as a result of the positioning operation, the position of the handset and the positioning error of the handset; and

the position information recognizing unit outputs, as information recognizable by a user, map information supplied from a map database together with the position and the positioning error of the handset as a result of a positioning operation by the handset.

13. A position information supplying method according to claim 12, wherein the positioning error of the handset is outputted by displaying an ellipse indicating a range of error.