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    Re: Deviation Card with GPS
    From: George Huxtable
    Date: 2006 Jul 31, 05:57 -0500

    Red wrote

    |
    | George-
    | It would seem like the answer lies in a few short sentences in this
    article:
    |
    | > Bill mentioned Richard Langley's article, referred to in [894] as-
    | >
    | > ""Getting Your Bearings: The Magnetic Compass and GPS":
    | > <http://gauss.gge.unb.ca/papers.pdf/gpsworld.september03.pdf>
    |
    | To the effect that the two sensors will each present the same data
    stream to the
    | computer, but 90d out of phase. Therefore when the computer compares
    the two
    | data streams it can count phase crossings to "count" a full circle.
    And the rest
    | apparently has to do with a 4-dimensional equation  in which the
    datastreams
    | should produce a defined ellipse, with any difference from the
    predicted shape
    | being mathematically reolvable (to those four varables) to produce
    the deviation
    | error.
    |
    | In simple words, the fluxgate compass is reaeding and comparing two
    data streams
    | and can calculate the deviation from them, with no time base needed,
    and in fact
    | only a 90d turn needed for a minimal solution. I assume the 720 slow
    rate turns
    | suggested in the instructions that I have seen are there because
    that gives the
    | computer better detail to work with, producing a more reliable
    correction.

    ==================

    Comment from George-

    Well, if that interpretation suffices for Red, good luck to him.

    For others, however, I recommend that they read the articles that were
    recommended, rather than going from Red's interpretation.

    George.
    |
    |
    | |
    |


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