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    Re: Historical Magnetic Variation/Declination
    From: Brooke Clarke
    Date: 2004 Jun 19, 18:57 -0700
    Hi Frank:

    The patented MC-1G Global compass  works at any latitude  and  would  point to a local pole.
    While on a polar flight between washington state and London I found that a magnetic compass was useless for some time when we were near the North pole and  even the MC-1G would have a problem when too close to a pole.

    One thought I have had is to combine a 3-D magnetic field sensor and a 3-D accelerometer and in static situations you could determine the difference between down and the magnetic filed and compare that to the World Magnetic Model.  This result would probably be only a few spots on the Earth where you might be, but during a reversal if there were multiple poles, then you could only navigate within one poles region.

    Have Fun,

    Brooke Clarke, N6GCE
    http://www.PRC68.com

    Frank Reed wrote:
    Brooke C wrote:
    "I'm not sure what yo mean by "regions of high field inclination"."

    Regions close to the magnetic poles where the field lines are nearly vertical. If you have a multipolar field, like the sort of field you might have during a polarity reversal, then you will have a number of poles scattered around the globe possibly in places that would be inconvenient.

    Since you certainly seem to know your sensors (I enjoyed your web page very much), in this "what-if" scenario where the field becomes multipolar, could one design a magnetic compass that would yield useful directional information (like standard compass bearing) even very close to a magnetic pole? If you had to cross an ocean where a magnetic pole is right in the middle of your trackline, could you have a compass that would yield useful information all the way across?

    Frank R
    [ ] Mystic, Connecticut
    [X] Chicago, Illinois
       
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