Chris Tedder Wrote:
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>
> According to the calculator, magnetic declination
> for Giza ranged from 1.35 degs E in 1960 to 3.12
> degs E in 2004 - a 1.77 degs eastward drift over
> 44 years, which is about 0.04023 degs / year. So
> if the data for 1960 - 2004 is used as an
> indication for 1910, it was about 0.66 degs W of
> true north.
>

Be very carefull here!!
Magnetic variance / declination does not change linear over the years.

Look at this graph for Halifax for example:



Jeff


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Science: An orderly arrangement of what at the moment seem to be facts.
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