On 1/25/17 4:12 AM, john@kk9a.com wrote:
Some day the magnetic pole will flip to the south pole. This will really
change the declination numbers!
John KK9A
Go to
https://maps.ngdc.noaa.gov/viewers/historical_declination/
and select the arctic map, and click the checkbox for "modeled
historical track of poles" or "observed pole locations"
and you'll instantly see why people are talking about "the poles are
going to flip relatively soon"...
As a practical matter, in Southern California, where for years the
declination sits around 14-15 degrees (magnetic pole to the right of
the geographic north), the change was about 0.1 degree/year. So a 10
year old topo map would be wrong by a degree.
in 1900, the 15 degree line crossed just south of the Salton Sea (which
didn't exist then...) and the 16 degree line went through the Channel
Islands and Ventura county. In late 70s, the declination in Ventura
County was about 14.7 degrees. In 1990s it was around 14.1 degrees, in
2004 about 13.5, in 2013 about 12.8
In the middle of the US, (along the agonic line, as it happens, but
that's coincidence), the pole is essentially moving straight away, so
the declination is changing slowly. in Europe, though, the pole is
moving cross ways relative to the line towards true north, so the
declination is changing quite quickly.
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