How to Take Bearings With a Compass From a Survey Map
You can get anywhere with a map and compass. You must know how to use them, however, and use them often or else they are useless. If you have a map of your local area, you can go out and practice your orienteering skills using familiar landmarks. This should help you guide yourself through unfamiliar terrain, too.
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Instructions
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Map to Compass Bearing
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1
Start at a spot that you can identify on your survey map. Look at your map and choose a place that you would like to walk to. You shouldn't be able to see your destination from where you stand.
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2
Place your map flat on the ground, or some other dry, flat surface.
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3
Place your compass on the map. Place your compass on the map so that one edge is touching the point of your current position. Align the compass so that the big arrow in the center of the base points toward your destination on the map. You may need to use your straight edge to find this line accurately.
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4
Look at your map. There should be parallel lines running north-south across it. Rotate the dial of your compass until the orienteering arrow in the center is parallel with these lines.
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5
Write down the bearing indicated on the dial. Depending on where you are, you must now either add or subtract your declination, which should be indicated on your map. This step is necessary in order to account for the difference between true north and magnetic north. This new bearing is the one you should follow in order to reach your destination.
Compass to Map
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A distant mountain is a good landmark to aim for. Look around you and find a landmark in the distance that you would like to identify.
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Point your compass at the landmark and take a bearing by rotating the dial until the movable magnetic arrow lines up with the arrow in the center of the dial.
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Account for your declination by subtracting or adding it to your bearing. Dial your compass to this new bearing.
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Place your compass on your map with one edge touching your current location, and rotate the entire compass until the arrow in the center of the dial runs parallel to the lines on your map. Make sure this arrow points to the north rather than the south.
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10
Extend the edge of your compass that touches your current destination using your straight edge. This line should run through the landmark you are trying to identify.
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Tips & Warnings
A good way to remember whether to add or subtract declination is the rhyme, "Declination west, compass best. Declination east, compass least." So, if you are on the East Coast, meaning your declination is west, your compass will point more toward the west and you must subtract your declination to bring this bearing to a map, and vice versa.
References
- Photo Credit compass on a map 3 image by Sergey Mostovoy from Fotolia.com compass and old map image by Vasiliy Koval from Fotolia.com die berge image by Jörg Jahn from Fotolia.com
