Are you wondering how to declinate a compass? The earth has two "norths", magnetic north and true north. Declination is the difference between magnetic north and true north, which is different in all locations world wide. A compass will point to magnetic north and generally maps use true north so the difference between what you see on your compass and map can be many degrees different so the object is to bring them together on the compass.
The items needed to set declination on your compass are:
- Current map showing declination lines for the area
- Quality compass
The process to set declination on a compass will be something like this.
- Obtain current maps. Magnetic north moves constantly so it is important to obtain current maps.
- Obtain quality compass. A quality compass will give you a better reading and have several features which make it easier to use and set declination. A good compass can have a clear base plate with markings made to coincide with map usage. Even if it does not have this, a good compass will have a way to set declination for an area. It may be a screw, it may be a way of moving the bezel ring to set it and keep it set. This is important if you are moving and using your compass to "shoot a direction". Without a set mark, you will always have to pull out a map and look at degree markings and "calculate" the declination, or simply "guess", not a good thing. Another feature a good compass will have is individual degree markings on the 360 degree compass ring. Some cheaper models show only the four directions or show a degree mark every five or ten degrees. Which again makes it a guessing game.
- Study your compass. Most compasses will have a way of setting the pointer for declination. Study this, and learn how to maneuver it. The ring or pointer will rotate around a 360 degree ring and you will be setting it over one of the marks on that ring.
- Look up declination. The map will have declination lines which will be expressed in degrees east or west of north. They will be different for each area so make sure to get the correct degree. Example. Declination is twenty degrees east of north, or twenty degrees west of north.
- Set compass declination. Using the method available on your compass, bezel ring or whatever it may be, set the declination. The trick here is to remember which direction to turn the bezel or set method. The declination pointer should start at zero degrees over north. The if it calls for twenty degrees east of north you turn the pointer counter clockwise to set the declination pointer at twenty degrees. If the map calls for twenty degrees west of north you would move the declination pointer clockwise over to the 340 degree marking, or basically subtracting twenty degrees from 360 degrees which is twenty degrees west of north. It sounds confusing but when looking at the compass it will make more sense.
Your compass is now set for declination. Luckily on most good compasses it "locks" into place until you reset it. Remember, being lost is not the time to learn how to use your compass, practice this all well in advance. Good luck and enjoy the wilderness.
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