[TowerTalk] Strange behavior

[jimlux]

On 1/25/17 4:12 AM, john at 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.