-------- Forwarded Message --------
Subject: Fwd: Re: [TowerTalk] Finding North (was Strange behavior)
Date: Wed, 25 Jan 2017 12:35:36 -0600
From: Gary Huber <GLHuber@msn.com><mailto:GLHuber@msn.com>
Organization: AB9M
As a former Field Artilleryman, I suggest you look at ;
http://usacac.army.mil/sites/default/files/misc/doctrine/CDG/cdg_resources/manuals/fm/fm6_50.pdf
5-5 for POLARIS METHOD of determining TRUE NORTH see page 5-10. (at this time
the accuracy error is about 2 mils with a circle having 6400 mils)
For the more accurate Polaris-Kochab method, see pages 5-3 thru 5-9.
Even with a declinated magnetic instrument, the declination constant can vary
dramatically in areas containing iron ore.
For radio work this may be trying to use a precision instrument for rough
trigonometry.
73 ES DX,
Gary - AB9M
-------- Forwarded Message --------
Subject: Re: [TowerTalk] Strange behavior
Date: Wed, 25 Jan 2017 05:39:21 -0800
From: jimlux <jimlux@earthlink.net><mailto:jimlux@earthlink.net>
To: towertalk@contesting.com<mailto:towertalk@contesting.com>
On 1/25/17 4:12 AM, john@kk9a.com<mailto: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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