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Method and apparatus for calibrating location finding equipment within a communication system
| Details |
Inventors: Mitzlaff, James Edward; Toone, John Duncan;
Assignee: Motorola, Inc. (Schaumburg, IL)
Primary Examiner: Tarcza; Thomas H.
Assistant Examiner: Phan; Dao L.
Attorney, Agent or Firm: Haas; Kenneth A.
Error vectors are added to any position estimate determined by Location finding equipment (LFE) in order to give a corrected position estimate. Error vectors are determined utilizing calibration terminals (114), which are roaming vehicles that move throughout the communication system's (100) coverage area. Each calibration terminal (114) comprises a remote unit (113) coupled with an independent position determining system (167) such as a Global Positioning System (GPS) receiver. Error vectors are determined by periodically polling calibration terminals (114). In response, each terminal (114) sends back a reply message containing their actual, independently determined location, along with periodically broadcasting a known sequence at increased power utilized by the LFE in determining a position estimate of the calibration terminal (114). The difference between the actual, and LFE determined position estimates are utilized in calculation of error vectors. |
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DETAILED DESCRIPTION OF THE DRAWINGS To overcome the problems described above error vectors are added to any position estimate determined by Location finding equipment (LFE) in order to give a corrected position estimate.
Error vectors are determined utilizing calibration terminals, which are roaming vehicles that move throughout the communication system's coverage area.
Each calibration terminal comprises a remote unit coupled with an independent position determining system such as a Global Positioning System (GPS) receiver.
Error vectors are determined by periodically polling calibration terminals.
In response, each terminal sends back a reply message containing their actual, independently determined location, along with periodically broadcasting a known sequence at increased power utilized by the LFE in determining a position estimate of the calibration terminal.
The difference between the actual, and LFE determined position estimates are utilized in calculation of error vectors.
Because of the roaming nature of the calibration terminals, comparatively few calibration terminals are needed to blanket a cellular communication system's coverage area.
Therefore, the accuracy of the LFE system can be increased without the increased number of calibration terminals needed by prior-art calibration techniques.
Additionally, because calibration terminals roam throughout a coverage area, calibration data can be obtained for much more of the coverage area than is possible with prior-art techniques.
The present invention encompasses a method for calibrating location finding equipment within a communication system.
The method comprises the steps of receiving an independently transmitted first location of a calibration unit and determining, via the location finding equipment, a second location of the calibration unit.
An error vector is determined based on the first and the second location and the location finding equipment is used to determine a location of the remote unit.
Finally, the location of the remote unit is calibrated based on the error vector
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