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    Re: Newbie - Variation Question
    From: Yves Arrouye
    Date: 2002 Feb 12, 21:29 -0800

    > That is the way the french deal with variation (declinaison)
    > The basic formula being:
    > True + Variation = Magnetic
    > They consider :
    > West variation as positive and
    > East variation as negative
    > So the negative East variation is added to True to get the Magnetic.
    Difference between France and Quebec? ;-) I learned
            Cv = Cc + W             (True = Magnetic + Variation)
            W positive if East
            W negative if W
    Fromn that one finds
            Cc = Cv - W
    so that would say subtract too. (Le Cours de Navigation des Glenans, 1990,
    says "if the variation is East, it is substracted from the true heading".
    Also, when taking sightings, the sentence "Est-ce Plus ou Est-ce Moins (Est
    Plus, Ouest Moins)" is used to go from magnetic to true.)
    It is the first time I hear about East variation being considered negative,
    but this all arithmetic, right? Add the negative quantity, or substract the
    positive one, who cares? If Andrew's GPS let him enter "15 E" for the
    variation, then his magnetic headings should be 15 degrees less than the
    true heading (doesn't this GPS come with a manual? What does it say?). If he
    entered "+15" thinking that this means "15 E" then Pierre's explanation
    justifies it. Pierre, any pointers to texts that refer to the variation as
    negative if East? All I can find says through a quick France Google pages
    says it's positive if East.

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