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The Influence Of Declination
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When you try to find a way where is no one or the borders of a defined area you should know about the influence of declination while converting map directions into field directions.
For sure you know there is a distance between geographic and magnetic north pole.
Declination could reach more than 30º depending on your current location.
The magnetic pole isn't static so declination is changing over the years.
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For bearing a direction you read from a map you have to know the actual declination.
You should find this information on your map if it's a good one.
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You should also find a note about how much the yearly change is and how old the information is.
The 13º declination west from example can be found in eastern Canada and U.S.A., southern Africa or northeastern Russia.
If there are no of these needed informations you have to check out the declination first before bearing any directions.
See our outdoor tip September 1999 to learn how.
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Using of a compass without declination correction can cause mistakes if you don't notice the declination.
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While transfering map angels (directions) to field you have to add west declination and to deduct east declinations.
From field to map west declination has to be deducted and an east declination has to be added.
The image shows how to adjust a compass without correction for bearing north on 13º west declination.
Mistakes will lead you to a wrong direction the double value of declination!
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Yes, that's very difficult sometimes, especially when you do it the first time.
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A compass with declination correction is much easier to use:
You adjust the declination one time only and bearing every wanted direction or angle or working with a map is possible without any further calculations.
Okay, these compasses are a little bit more expensive than compasses without correction.
But you will change your mind when you get lost only because wrong calculations of declination!
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check out: Find out the declination - outdoor tip September 1999
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