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[TowerTalk] FW: Magnetic Declination

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Subject: [TowerTalk] FW: Magnetic Declination
From: (Bill Coleman)
Date: Sat, 6 Oct 2001 14:47:01 -0400
On 9/22/01 6:22 PM, John Farber at wrote:

>Magnetic declination is not the same thing as magnetic deviation. I think
>you guys are talking about deviation from true North, whereas mag
>declination is the vertical angle the field lines make going into the Earth,
>and that varies by latitude.

Magnetic Deviation is defined as the error in the compass itself, due to 
its installation or other surrounding objects with metal fields.

What they really mean is Magnetic Variation, which is the difference 
between true north and magnetic north due to the offset in the two poles, 
plus any magnetic composition of the earth itself.

Unfortunately, Topographical maps usually refer to Variation as 
Declination, hence the confusion.

Bill Coleman, AA4LR, PP-ASEL        Mail:
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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