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That would lead one to believe the field would be more, or less constant in its polarity. There is a physical axis for the earth, and there is a magnetic axis. As the north magnetic pole "wanders", the south magnetic pole moves in a like manner. But there has to be something else going on for both the magnetic north and south poles to be moving.
The best way to deal with declination is to buy a compass that can adjust for magnetic declination, set it to the correct declination of where you are, and go forth. The map and compass will align without your doing any mental correction (very important if you're under stress!) Do not buy/use a compass that is too difficult for you to use.
Second determine the desired declination value. The examples below use the angle between mag and grid north or angle G-M (FM3-25-26 P.64). Don’t forget to calculate the Magnetic declination value for the current year. Third and here is the secret to visualizing declination, draw the declination diagram.
Henceforth, at least until Magnetic North moves again, you can use the Declination Line(s) to orient the map to Magnetic North, and use the compass without having to consider/adjust for the declination. Back in the day, for maps we used a lot, we'd use a parallel ruler to locate and draw declination lines in several key places on the map.
The article has a chart "Simple Declination Chart" showing Map to Compass with West declination as "adding declination" and East declination as subtracting declination. Then has compass to map (what I am wanting to learn) showing with West declination to subtract declination and with East declination to add declination.
Global Village Idiot Scout. Joined Jul 7, 2013 Messages 942 Likes 3,595 Location NW Indiana
I am unclear on a facet of declination adjustment. If declination is, for example, 13.00 degrees east and it changes 0.1 degree west per year, what would be the declination five years from now?
Actually a magnetic needle will point north so even a cheap compass is accurate unless the needle has undergone a pole reversal. Magnetic north is magnetic north and the only way a compass can point off north is if there is an external influence like a magnetic metal near it or, I suppose if somebody in the factory somehow got the magnet glued ...
Nope. Magnetic declination is simply the difference between magnetic north and true north. Both the compass pointer and the needle should point in just about the same direction (magnetic north), which they are. I rarely use a compass, except in poor visibility. Otherwise, I prefer to read the ground having previously studied a map.
It is also "GI-proof" and is both heavy and bulky and not that easy to use with maps. The army uses magnetic readings, the fire direction center takes care of the conversion to true. The Dakar is lighter and more compact, has a declination adjustment, the lens allowing reading to 1 degree as well as all of the functionality of the baseplate ...