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Method and apparatus for correcting the output of an onboard vehicle terrestrial magnetism sensor

  • US 5,151,872 A
  • Filed: 07/24/1990
  • Issued: 09/29/1992
  • Est. Priority Date: 10/17/1989
  • Status: Expired due to Fees
First Claim
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1. A method for correcting the output of a terrestrial magnetism sensor mounted on a vehicle comprising the steps of:

  • generating an output from the terrestrial magnetism sensor;

    detecting an error in the output of the terrestrial magnetism sensor caused by extraneous magnetic influence;

    selecting a plurality of data pairs xo, yo form the output of the terrestrial magnetism sensor;

    determining from said plurality of data pairs xo, yo an initial radius ro and initial center coordinates xo, yo of an initial azimuth computation reference circle;

    computing a distance ro between each of said plurality of data pairs xo, yo and said initial center coordinates xo, hd o;

    calculating a difference between each distance ro and said initial radius ro ;

    obtaining a variance σ

    2 from squares of the calculated differences;

    determining an updated radius r'"'"'o and updated center coordinates x'"'"'o, y'"'"'o of the azimuth computation reference circle such that said variance σ

    2 is minimized with respect to changes in coordinates x, y and radius r;

    establishing an updated azimuth computation reference circle from said updated radius r'"'"'o and said updated center coordinates x'"'"'o, y'"'"'o ; and

    correcting the output of the terrestrial magnetism sensor using said updated azimuth computation reference circle.

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