When you’re used to hiking well-developed trails, it’s all too easy to just follow the signs and not worry about navigation. Bringing a compass seems unnecessary when the path is clearly defined and helpful markers are posted at every intersection.
But what if something goes wrong? Some menacing teenagers remove those essential signs, or heavy rains wash away the unambiguous route? Or perhaps more likely, what if you’re hiking above treeline where there’s little vegetation and no real trail to follow, or you just want to take a trip into the remote backcountry where nobody has set up trail markers?
Learning how to use a map and compass is one of the most essential skills for backcountry navigation. Even with all the GPS technology we have today, it pays to know how to find your way around using no more than a compass and the Earth’s magnetic field – just ask anyone whose had their phone battery die on the trail, or hiked through a thick forest that satellite signals couldn’t penetrate. Fortunately, the Earth’s magnetic field is always there to help you plot a course.
But just because a map and compass are low-tech doesn’t mean they’re easy to use. Navigating with them requires a thorough understanding of how they work, a fair amount of practice, and a little bit of patience. But it’s well worth it to not be at the mercy of electronic devices when you’re in the backcountry.
Before you set off trying to use a compass, it pays to learn how they work. The most basic compass is a circular capsule filled with a liquid, inside of which is a magnetized needle. The needle orients itself parallel to the Earth’s magnetic field and continually points north.
Types of Compasses
While we’ve probably all seen a basic compass and understand how they work, they’re not particularly useful for navigation. These are some alternative compass types and their different navigational purposes.
This type of compass is designed for the sport of orienteering, in which participants run or otherwise navigate a cross-country course as quickly as possible using a map and compass.
These minimalist compasses, which usually have cardinal directions rather than degree markings, attach to the thumb so the user can hold the compass and map in the same hand.
With their durable design, these compasses are popular with the military. They look very similar to a standard compass except they’re encased in a round metal container. When the container is open, a small arm folds out, which has a lens that points towards the compass face.
The lid of the compass has a small slit, and when aligned properly, the user can read the bearing from the compass face through the lens while simultaneously looking through the slit to a landmark.
You’ll most likely use a baseplate compass for navigating in the wilderness. They’re very versatile, and the features listed below make them quite useful in combination with a map.
Features of a Baseplate Compass
Unlike a basic circular compass, these compasses has a roughly rectangular baseplate. The baseplate is translucent and lets you see through it to a map. One half of the baseplate is occupied by the circular compass and its bezel, while the other half acts as a straight edge to be overlaid on a map.
It also has some ruler markers that can be cross-referenced with the map’s scale to figure out the distance in the real world. Some baseplate compasses also include a magnifying lens, which is helpful for reading small print on a map.
Direction of Travel Arrow
This arrow on the compass is used to mark the direction you intend to travel. If you’re following a trail on a map, you’ll point the arrow in the direction of that path.
The bezel (the ring around the outside edge of the compass face) on a baseplate compass is marked with degrees (0-360) and can be rotated around the compass capsule. You’ll be using the bezel to take a bearing – more on that below.
The index line is just outside the 12:00 position on the compass bezel. It marks the point on the bezel where you’ll read your bearing.
There’s a set of lines on the base of the compass capsule, which are intended to be aligned with the vertical lines on a quadrangle map. Aligning them correctly is important for keeping the compass squared with north on the map.
Like the orienting lines, the orienting arrow is marked on the base of the compass capsule. When you have the orienting lines aligned with the map’s grid, the orienting arrow will point north on the map.
Declination Scale and Indicator
Inside the compass capsule, you’ll usually see a scale reading 0-60. This indicates the declination adjustment, and it can be set to either east or west, depending on your location. We’ll discuss how and why to set declination later on.
How to Read a Compass
Now that you understand the different parts of the compass, it’s time to learn how to use it properly. Reading a compass is not particularly difficult – the red arrow points north after all – but there’s a bit more to it than you probably think.
True North vs. Magnetic North
One of the first things that confuses novice navigators is that their compass does not actually point to the geographic North Pole. Rather, the needle directs you toward the magnetic north pole, which is in Arctic Canada and about 500 kilometers from the geographic North Pole.
As a result, readings you take on your compass will be off by a few degrees, referred to as the declination. That may not sound like a lot, but for each degree it’s off by, you can end up a hundred feet off course for every mile of travel.
Fortunately, most topographical maps will include the declination for your area, which you can use to make adjustments to the compass. It’s important that you use maps that are relatively recent, as declination changes over the years. If your map is old, you can look up the current declination online.
How to correct for declination
The adjustment for declination is usually located inside a small hole on the backside of the baseplate, underneath the compass capsule. To adjust it, insert the key that came with the compass into the hole, and turn it until the declination indicator points to the correct number of degrees on the scale.
How to figure out which direction you’re facing
Now that the compass is pointing towards the geographic North Pole, you can finally figure out which direction you’re facing. To do this, hold the compass so the direction of travel arrow is pointing away from you. Look to where the red end of the compass needle is pointing; this is north.
Now, twist the bezel on the compass so the needle is inside the orienting arrow. The rear end of the direction of travel arrow will now point toward the direction you’re facing. This isn’t really sufficient for navigational purposes, but it’s useful for orienting your body.
If you don’t have a compass with you, remember that the sun rises in the east and sets in the west. If it’s before noon, you’re facing north if the sun is on your right side; in the afternoon, you’re facing north if the sun is on your left.
Using a Map and Compass
You now have a basic understanding of how a compass works; but unless you’re walking through the Sahara desert or a featureless, flat plain, knowing your direction isn’t sufficient. You’ll need to combine your directional knowledge with a map that shows landmarks and routes.
Orienting yourself with the compass and map
Let’s start by looking at how to orient yourself with a map and compass when you know where you are. This is how you’ll determine which path to take when you come to a fork in the trail.
Place the compass on the map, and turn it so the direction of travel arrow is facing the same way you are. Then, turn the bezel so that the orienting lines are aligned with the north-south lines on the map. You are now oriented with the map and can use it and the compass to find your way.
How to take a bearing
Taking a bearing is another way of saying “setting a course with your map.” – in other words, using the map to figure out where you are and which direction you want to go. Start by placing the compass on your map. Point the direction of travel arrow either towards a landmark or in the direction of the trail, and then rotate the compass bezel until the needle is inside the orienting arrow. The index line now is now pointing to the bearing on the bezel. You have your bearing!
Obviously, most trails are not perfectly straight, so you’ll need to make some choices about how you want to use your bearing. The simplest method is to take a bearing towards an important landmark, maybe a bridge or campsite. Because you’re following a trail, you won’t always be walking directly toward that landmark, but you can follow along on the map and get a general idea of whether you’re on course.
The other method is to take a bearing to reach the next point where the trail curves. This means taking bearings much more frequently, but you can be certain that the direction it’s pointing is exactly the way you need to go.
How to find your location when lost
You’re in the woods and you’ve just realized you have no idea where you are. The best way to find your position is to take a bearing of a landmark, which works well if you’re in an open area where you can see for a miles.
Line the compass up on the map so the corner of the baseplate with all the markings is touching the landmark you want to reach. Then, rotate the baseplate until the orienting lines are aligned with the north-south grid lines on the map. You should now be able to draw a line from the corner of the baseplate to your location. Unfortunately, that alone won’t tell you much because you could be anywhere along the line.
To get your exact position, you’ll need to use triangulation. Sight another landmark in the distance, and take a bearing of it following the same steps you did for the first one. Choosing a landmark that’s far away from the first one will give you a more accurate reading. You’ll now have two lines drawn on the map, and the point where they intersect is your position. You can take a third bearing to ensure accuracy, but it’s not necessary.
How to plan a route on the map
To plan a route, place the compass capsule on the map at your location, and move the other end of the baseplate to align with where you want to go. The direction of travel arrow will point toward your destination. Then, rotate the compass bezel until the orienting lines are parallel with your map’s north-south grid lines (not the contour lines indicating elevation). The index line will now point to a degree number on the bezel, which is your bearing angle.
At this point, you can put the map away and hold the compass in your hand so the direction of travel arrow is pointing away from you. Now, turn your body until the north end of the compass needle is inside the orienting arrow. As the north end of most compass needles are red and the orienting arrow looks like the outline of a building, this step is remembered as “getting red in the shed,” Now you can follow your direction of travel arrow to the destination.
Can you use a compass to tell time?
The short answer is no. Technically, a compass could be used to construct a rudimentary sundial if you know your position’s latitude and have a protractor. However, you’re better off making an educated guess based on the sun’s position in the sky.
Can you use a compass to measure angles?
Yes. To do this, rotate the compass bezel until the zero degree mark is over the needle (which is pointing north). Now, turn towards the object you want to measure the angle to. The degree marking the needle now points to will give the angle between magnetic north and your object. That’s probably not what you were looking for, but now you can turn to your second object and repeat the same steps. To get the angle between the two, subtract the first degree measurement from the second one.
Can you use a compass to measure distance?
Basic trigonometry says that if you know the size of two angles and the length of one side of a triangle, you can figure out the length of the other two sides by finding the tangent.
Can you use a compass in the Arctic or at the North Pole?
Compasses can be used in the Arctic, but declination calculations become more much critical the closer you are to the magnetic north pole. In certain parts of the Arctic, the difference between the geographic north pole and the magnetic north pole could be 90 degrees or more. If you were to stand right at the magnetic north pole, the compass would not function at all.
Can you use a compass on the moon?
No, compasses rely on a magnetic field to function. The moon’s magnetic field is very weak, and Earth’s magnetic field only extends about a quarter of the way to the moon.
How can you use a compass to find south?
Follow the other end of the compass arrow. Compasses always point north, if you want to travel in a southernly direction, turn the compass so that the needle points in the opposite direction as the direction of travel arrow. Then follow along that course.