What Do Compasses Do?

Compasses are basically designed to show you where north is in the real world. Knowing where north is allows you to identify all of the other directions in the "compass rose" (east, west, south, northeast) as you travel and to head in those directions.

Orienteering-style compasses take this one step further, by allowing you to assign a specific numerical direction (or "bearing") to any direction in the full 360° circle around you. This means you can head toward a very specific spot, rather than simply heading "south-southwest" or "almost due east."

To convert general compass directions into bearings, an orienteering-style compass has a special rotating bezel mounted around the outside edge of the compass needle. This bezel, which is divided into 360° usually in 2° to 5° increments°, measures the direction towards a given object in terms of an angle; specifically, the clockwise angle between a straight line pointing due north and a straight line pointing toward the object. This bezel allows you to express any specific direction as a number between 0 and 360.

Why Are Precise Directions Important?

Why is it more helpful for you to know that the campsite you want to get to lies on a bearing of 40° instead of "to the northeast"? Because the more accurate your direction of travel is, the more likely you are to get where you want to go.

Following a bearing that is just one degree off can translate into almost 100 feet of error after just one mile. That means that after a 5-mile hike, you may miss your target by almost five hundred feet. In the wilderness, a few dozen feet can mean the difference between spotting a campsite or trail and missing it completely. Simply heading "somewhere to the north" can cause serious problems.

Being able to measure directions in terms of specific compass bearings can also help in a number of unique situations. For example:

  • Knowing the bearing that you're heading towards can keep you on track even if your target (a mountain, a river, a house) gets hidden by bad weather, nightfall or an obstacle.
  • Knowing the bearing that you're heading toward can keep you on track even if you have to detour around an object in your path (your compass will allow you to turn from your original course, get around the obstacle safely, then turn back and find your exact course again).
  • If you know where you are on your map, you can take a bearing on a target on your map, then follow that bearing in the real world, even if you've never actually seen the object that you're heading towards.
  • Knowing how to take bearings can help you pinpoint your location on your map even if you are completely lost (see the section on triangulation below for details).

When Is Compass Navigation Useful?

On most backpacking trips, especially those planned by beginners, compass navigation is seldom necessary. Simply following the trail carefully and checking your map from time to time should get you from campsite to campsite safely.

But knowing how to use a map and compass is still very important for all backpackers. Because if you get lost, or you have to cross an area of land without trails, your map and compass may be the only tools that can get you back to camp safely.

Trick of the Trade - Triangulation

Triangulation is one of the most common and most useful navigation techniques that uses both a map and a compass. It's a simple procedure that, when done correctly, can pinpoint your exact position on your map even if you have no idea where you are.

Triangulation is based on the principle that once you've taken a bearing on a visible landmark (i.e., established in what direction that landmark lies from your present position), you can logically assume that your position lies somewhere along a line drawn to that landmark along that bearing. If you take 2 accurate bearings on 2 separate landmarks, and draw a line on your map from each landmark along the bearings taken, your location will be where the two lines intersect!

How to Find Out More

To find out more about basic map and compass navigation, check REI's great selection of basic navigation books, or call your local REI and ask about their hands-on basic navigation clinics. The more you learn before you start backpacking, the safer you will be!