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Compasses

Compasses determine direction by using Earth's magnetic field to guide a magnetized needle. It can be used to point a certain direction, orient a map, or get the bearing of an object.

Ensure the compass is flat (along a tangent line to earth). Replace a compass if there are imperfections, such as bubbles in the compass housing fluid. If in doubt, use multiple compasses. Keep all magnetized objects away from compasses, including metal poles, some electronic devices, and magnets. Move around to confirm that the compass points in the same direction. Use only on planets with a magnetic field that has magnetic north near true north unless you are using it for other purposes.

Adjusting for declination

Maps are usually oriented to true north, located at the north pole. However, the Earth's magnetic field doesn't line up exactly. Compasses point toward magnetic north, whereas maps point toward true north, leading to inaccuracies. Adjusting for this difference is necessary unless you are in an area where the poles line up.

1. Find declination. It will sometimes be indicated on the map, but keep in mind declination changes. Alternatively, find it online.
2. If declination is easterly, add your declination to your heading. If westerly, subtract from heading.
3. If necessary, draw magnetic north-south lines on your map and use that to orientation.

Traveling a certain direction

Make sure to adjust for declination if you desire to travel in true directions rather than magnetic directions.

1. Rotate the compass housing until the desired direction lines up with the direction of travel arrow.
2. Turn until the north end of the needle (usually red) lines up with the north end of the orienting needle
3. Move in the direction of the direction of travel arrow. Don't continuously focus on the compass; walk toward a landmark that is in the correct location.

Orienting maps

Orienting a map means rotating it until it lines up with what it shows.

Without a compass:

1. Find an easily recognizable landmark
2. Find the landmark on the map
3. Turn map until the landmark on the map lines up with the actual landmark
4. Verify with other landmarks if necessary

With compass

1. Find north-south line on map
2. Adjust for declination if necessary
3. Rotate map until north-south line lines up with north end of needle
4. Verify with other landmarks if necessary

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