| US 7,460,066 B2 | ||
| Positioning system | ||
| Masayuki Ikeda, Shiojiri (Japan) | ||
| Assigned to Seiko Epson Corporation, (Japan) | ||
| Filed on Jan. 25, 2008, as Appl. No. 12/11,361. | ||
| Application 12/011361 is a division of application No. 11/609048, filed on Dec. 11, 2006, granted, now 7,348,920. | ||
| Application 11/609048 is a division of application No. 10/780288, filed on Feb. 17, 2004, granted, now 7,277,050, filed on Oct. 02, 2007. | ||
| Claims priority of application No. 2003-054021 (JP), filed on Feb. 28, 2003; and application No. 2004-031058 (JP), filed on Feb. 06, 2004. | ||
| Prior Publication US 2008/0129590 A1, Jun. 05, 2008 | ||
| This patent is subject to a terminal disclaimer. | ||
| Int. Cl. G01S 5/14 (2006.01); G01S 3/02 (2006.01); H04Q 7/20 (2006.01) | ||
| U.S. Cl. 342—357.14 [342/357.09; 342/357.1; 342/463] | 11 Claims |
| 1. A positioning system for determining a position of a positioning terminal, the system including a plurality of first signal
sources each emitting a respective first signal, and one or more second signal sources each emitting a respective second signal,
the first signals being synchronous with a reference time and the second signals being non-synchronous with the first signals,
said system determining the position of the positioning terminal based on a signal propagation time and signal propagation
speed of at least one of the first and second signal sources, said positioning system comprising:
a measurement device associated with each second signal source that receives the first signals from the first signal sources
to determine a position P of the measurement device and a time of measurement when the measurement device receives the first
signals and for, based on the time of measurement, measuring a receiving time (TR), based on the reference time, of a predetermined
event of the second signals;
a control device that determines a signal propagation time (t) between the measurement device and its associated second signal
source by calculating a relative distance |P−Q| between the measurement device and its associated second signal source based
on the position P measured by the measurement device and a position Q of the second signal source and by dividing the resulting
distance by the signal propagation speed, and that determines a time (TT), based on the reference time, at which the second
signal source originates the predetermined event by solving TR−t;
the positioning terminal including a receiving device that receives signals from the first and second signal sources; and
a communication device that communicates between the control device and the positioning terminal,
wherein the communication device communicates the time TT to the positioning terminal, and
wherein the positioning terminal receives the time TT from the communication device and uses the time TT to receive from among
the first and second signals for determining the position of the positioning terminal.
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