A tool for the Ages—the compass is a great companion for any off-trail hiker or explorer. There are many different uses for a compass. Here, we’ll cover the simplest use—taking a bearing. You’ll learn the different parts of a compass, how to use a compass to discover which direction you are heading (taking a bearing), and which direction you are located in from the perspective of another vantage point (taking a back bearing).
But first, you might be tempted to ask, “Why use a compass when there’s GPS?” As with any electronic device, there might not always be strong satellite connection—and in the case of GPS you need three. Also, you’ll be relying on a battery powered device—it may just flat run out on you. So many a trail blazing hiker will pack along a GPS, map, and compass for the trip.
For more information about using this triple threat for navigation in the wild, www.traditionalmountaineering.org gives detailed instructions.
Parts of a Compass
To know how to use a compass, you need to understand the role of each part of the tool. Below is a diagram of a simple orienteering compass and a short explanation for each part.
– Direction of travel arrow. The direction of travel arrow or sighting line is used for sighting and following bearings. The arrow should be pointed in the direction of the destination or landmark you intend to reach.
– Needle. The magnetic needle points to magnetic north.
– Orienting arrow. The north-south orienting arrow (red or black outline of an arrow) is used to align the magnetic needle when taking a bearing. It is also what is adjusted to set the compass for magnetic declination if you’re using your compass with a map. We will learn how to navigate using a map and compass in a future post.
– Compass Dial. Sometimes referred to as the housing, this revolving dial is labeled with the cardinal points and degrees. Rotate the dial to line up the compass needle with the orienting arrow when taking a bearing.
– Base plate. The transparent plate everything else is either printed on or attached to—the base plate can be used as a ruler to measure map distances, which we’ll teach at another time.
Now that we’ve got that down, we’ll offer a few tips on getting accurate compass readings. Don’t worry if you don’t recognize the jargon. We’ll go into depth soon. This advice can be especially helpful since small errors in reading a compass can mean big inaccuracies on the ground:
1. Hold the compass level and steady so the needle swings freely.
2. Hold the compass about waist high in front of the body.
3. Raise and lower eyes when taking a bearing, do not move your head.
4. Always use the same eye when taking a bearing.
5. Turn your body until you are directly facing the object that is being measured.
6. Be aware: Magnetic fields will give incorrect compass readings. Avoid taking readings near magnetic fields such as steel, iron, vehicles, rebar, and clipboards. Even belt buckles, glasses, and rings can interfere when reading a compass.
7. Take bearing twice.
8. Follow the direction of travel arrow, not the compass needle, when walking a bearing.
9. Always follow the line indicated by the compass rather than relying on judgment as to the direction.
10. Use back bearings to ensure you are on track when navigating.
These tips can be found at www.nwcg.gov along with more instructions on how to use a compass.
Orienting a compass
To help the visual learners, refer to the picture below. It’s a picture of the unit circle with the cardinal points and degrees. It looks similar to your compass’ dial.
Cardinal points and degrees on a compass
When using a compass to find magnetic north you’ll need to set the compass dial at 0 degree or 360 degrees in relation to the direction of travel arrow. Holding the compass as recommended above—now turn your body until the magnetic needle is perfectly housed in the orienting arrow and you’ll be facing magnetic north.
Bearings are expressed in angles or a certain number of degrees from magnetic north. To take a bearing find your destination, in this case, by sight since we’re not using a map with our compass today. Face your landmark and turn the dial until the orienting arrow and magnetic arrow line up. Read the angle at the top of the compass—the one that is perfectly aligned with the direction of travel arrow. This is your bearing to your destination.
When taking bearings in the wilderness without a map, it can sometimes be helpful to use an intermediate object to gain your desired destination. Especially if you track through vegetation or are dealing with varying altitudes, each of which could cause you to lose the line of sight to your destination. Set a course for that object first. Then recalculate when you’ve reached this first destination for the final destination.
Back bearings can also be a useful tool for checking to be sure you’re still on course or to alert someone ahead of your location. You can determine your back bearing by either adding or subtracting 180 degrees from your original bearing. So what’s the point? One instance where you may need your back bearing would be to tell a rescue party where you are in relationship to a landmark you and the party can see. With the proper communication device you could tell them which bearing to take; i.e., “I’m 120 degrees from the windmill.” If they begin at the windmill and follow a straight course on the bearing 120 degrees, they can find you. Your compass would read 300 degrees to the windmill (a 180 degrees difference).
Once you have your bearing simply follow the direction of travel arrow, remembering to use the advice given earlier in the article to keep well on course. Don’t turn the dial on your compass until you’ve reached your destination.
Practice in a familiar location
It’s a good idea to give this kind of navigation a spin in a familiar place first. When you feel comfortable with your skill, move out to more challenging terrain.
Using a compass can be a rewarding skill to acquire and, as always, TETON Sports wishes you the best in all your adventuring!