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A) Obtain the local magnetic declination for the area represented on your map. At the bottom of every USGS map is a diagram that displays the difference & direction between true north (represented as a star), grid north (abbreviated as GN), and magnetic north (abbreviated as MN). Magnetic declination is the number of degrees and direction between true north and magnetic north. Because declination varies over time, it is advisable to get a reasonably current figure. If your USGS map is more than 15 years old (the declination date appears in the diagram), here's an easy-to-use website that gives you the information you need:
Magnetic Declination Calculator
If magnetic north is east of true north, the local declination is positive
If magnetic north is west of true north, the local declination is negative.
B) Draw a line on the map that connects your starting point with the destination (your "map bearing").
C) Distance yourself from any nearby metal such as keys, belt buckle, desk, car, fence etc.
D) Place the compass on the map so the baseplate is parallel to the line you drew. Make sure the direction of travel arrow points to your destination.
E) Rotate the dial until compass ring north agrees with map north. Do not move the compass when you rotate the dial.
F) Remove the compass from the map and, with the direction of travel arrow pointing directly away from you, rotate your body and the compass all in one motion until the red magnetic needle overlays the orienting arrow.
G) If local declination is positive, then subtract the declination amount (turn the dial clockwise). If local declination is negative, then add the declination amount (turn the dial counter clockwise).
H) Again, with the direction of travel arrow pointing directly away from you, rotate your body and compass all in one motion until the red magnetic needle overlays the orienting arrow. Sight a landmark along this direction of travel and proceed to it. Repeat this step until you reach your destination.
