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    Re: Annual Increase of Variation
    From: Brian Whatcott
    Date: 2002 Feb 13, 12:13 -0600

    At 06:40 AM 2/13/02, you wrote:
    >It is my understanding that the magnetic north pole lives at somewhere
    >around 75 north by 95 west;  this being the area that most compasses point
    >to. (except french ones I'm told).
    >The "pole" is moving west approx 1 degree of longitude per
    >year.  Longitude where we are is pretty fat compared to 75 north plus a 1
    >degree change in longitude that far away makes for a very small great
    >circle correction to us.
    >I would still like to know if there is a geographical position of the pole
    >that I could use to reduce a variation.
    Here are some recent determinations of the co ordinates of the magnetic
    north pole (as variously defined!)
    N81.5 W112.0 (2002)
    N79.0 W105.1   (1996 dip model)
    N78.3 W104.0  (1994)
    N77.0 W102.3   (1983)
    This USGS chart gives the general drift:
    You will need Acrobat to read this PDF file.
    I recently did a regression on 100 years of total field intensity data for
    this area.
    The fitting equation shows that by AD 2985, the field strength will have
    gone to zero (if everything proceeds according to its current decay rate -
    but it won't!)
    Brian Whatcott
       Altus OK                      Eureka!

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