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David Weilacher wrote:

> Would like to know lat/lon of magnetic north pole.
> Best I've found is "Close to 71N by 96W"

Without a date, this is meaningless. The pole may have been there at some
time in the past. Presently, it's closer to N 80 W 105.

There are different ways to define "magnetic north". An intuitive
approach would be to define the magnetic poles as the places where the
magnetic field lines intersect the surface of the earth perpendicularly;
Or, in other words, where inclination is 90 deg. But this is not very
practical, so in reality the definition is more complex. At any rate, the
locations of the magnetic poles change over time.

>
> If I know my position (lat/lon)
> Call the north pole lat declination
> Call its lon GHA
> Would the sight reduction yield an azimuth (Zn) equivalent to compass
> variation?
> (excluding local anomalies)

No, it would not. Consider a simple counter example. Hiking in Austria
with a compass is simple: No mag. variation there. So you would assume
the mag. north pole is due north of Salzburg, wouldn't you? But it isn't.

The magnetic field is not uniform. The field lines are bent in the most
irregular shapes. DMA chart 42, "Charts of the Earth's Magnetic Field" is
a Mercator world map showing lines of identic mag. variation in purple
and lines of identic annual change of variation in blue.

Herbert Prinz (from 1368950/-4603950/4182550 ECEF)

   

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