For hikers, a compass is like car insurance: you never need one except when you do. Say you’re going uphill into a fog bank and suddenly you lose all visual references of your location. You’re flying blind now. Then the trail splits. Which way to turn?
Novices who’ve just tossed their shiny new compass in their pack think they’re covered till they break it out in the middle of said fog bank and realize they have no earthly idea which way to go, based on what that little floating magnetic arrow is telling them. So, it points north. Then what?
You can train yourself to use a compass in your living room; stuff you’ll need to learn:
- How to take a bearing: all this means is looking straight ahead and figuring out where you’re going, relative to magnetic north.
- Combining a map with a compass: This is your only sane option in the aforementioned fog bank. You put your compass on the map to find a heading telling you which way to turn (this is why most compasses are transparent).
- Declination: Your map is oriented to true north, but your compass points to magnetic north. Declination is the difference between the two: for instance, Northern California is a about 15 degrees away from true north, so you have to adjust your compass readings accordingly (though if you’re hiking on established, marked trails you’ll probably never really need to worry about this. But if you’re going overland with topographic maps, it’s vital. Failing to account for declination can throw you off by several miles.)
A site called Compass Dude has all you need to know about the specifics of reading a compass. Check it out, then get out there with a map and see how it all comes together.
Once you’re good at it, you can get into orienteering — the sport of finding one’s way without trails. Steve Sergeant at the WildeBeat has this intro at his podcast.