A magnetic compass aligns itself with magnetic North. Depending on where you stand, magnetic North falls a few degrees off true North. We call the discrepancy between these two measurements declination. With declination in consideration, a compass shows which way is North, South, East and West.
Orient a Map
If you have a map of your area, you can align the map so it matches the land features in relationship to where you stand. This is called orienting a map. You can orient a map just by sight, but when you don't know the land features around you, you can use a compass to orient your map instead.
Take a Bearing on a Map
You can measure the distance in angles, the bearing, between two features on a map with a compass. You will not usually take a bearing this way to use in actual navigation, but you may want to practice this skill to familiarize yourself with the concept of a bearing.
Shoot a Bearing in the Field
When you know where you are on a map, you can shoot a bearing of your destination--say a peak several miles away--in order to give you a degree to follow as you travel. For example, if you can see Granite Peak in the distance, and that's your destination, you can take the bearing of Granite Peak and record the number you find. As you travel, orient your course to stay in the direction of the bearing you took so you don't get lost.
If you don't know where you are, but do recognize the features around you and on your map, the compass can pinpoint your location through triangulation. Triangulation takes two bearing measurements from two known land features and plots them on a map. The lines drawn on a map from these two bearings will intersect at one point. This point shows where you stand.
Article Written By Kathrine Cole
Kathrine Cole is a professional outdoor educator. She teaches rock climbing, backpacking, cycling, and bike maintenance classes. She is a graduate of the National Outdoor Leadership School, a Wilderness First Responder, and a Leave No Trace Trainer.