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Re: [OM] OT Maps True vs Mag North Was: newspaper photographers are smar

Subject: Re: [OM] OT Maps True vs Mag North Was: newspaper photographers are smart, ri...
From: Doggre@xxxxxxx
Date: Fri, 21 Sep 2001 05:59:20 EDT
In a message dated 9/20/01 10:02:53 PM Pacific Daylight Time, 
JamesBCouch@xxxxxxxxxxxxx writes:

> Actually Chris, here in the states the term is magnetic declination, usually
>  shortened by most folks to declination. Magnetic declination actaully 
varies 
> quite
>  a bit here in the states 22-21 deg east in most of Washington state. In the
>  'midwest' (Ohio) declination is 0. In Maine declination is 20 deg WEST!
>  Declination is also used for grid difference, and refered to as Grid 
> Declination.
  
To a mariner, the U.S. Navy & Coast Guard, and I think aviators (help me out 
here, Chris) "deviation" is compass error, caused by nearby magnetic metals 
(like the hull of a ship) which is corrected (mostly) with the compensating 
magnets inside the compass housing.  Tough to get all "deviation" out of a 
compass.

A chart showing the deviation of a compass at various headings (determined by 
"swinging ship") is posted alongside the compass binnacle.

The horizontal variation in the earth's magnetic field from True geographic 
north is termed "Variation".

Rich (no more OT from me this week, promise)

P.S.  What's a "map"?

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