The Basics of Using a Compass

A compass is an important tool to have along on your adventures, but how do you use it?

The first thing to keep in mind is that a compass works because it is magnetic. The needle will point toward anything that is metal or has a magnet in it. Knives, axes, saws, metal buckles on packs, metal belt buckles, metal pens, wrist watches, metal jewelry, and cell phones can all distort the reading on your compass to some degree. The distortion may be minimal in some cases, but the difference will undoubtedly be there. When you are trying to take an accurate reading, make sure that nothing metal is close enough to pull the needle away from magnetic north, which is where it’s supposed to be pointing.

Once your metal gear is away from the compass you can work on getting an accurate reading. The compass is made of a few different parts, and some parts will vary between compass models. I will focus on two models from Suunto that are representative of many popular models from various brands. These two are the MC-2 Global (MC-2G) and the MCB.

The MC-2G is, in my opinion, just about the best you can get without investing in a pocket transit, which is essentially a supremely accurate compass used for surveying. The level of precision required for surveying is generally more than is necessary for most land navigation applications. Many of the compasses available at the average hiking store are made to be used in either the northern hemisphere or the southern hemisphere. If you are reading this in the northern hemisphere, the compasses you find in stores will almost certainly be made for the northern hemisphere. The MC-2G is a global compass, meaning that it can be used on either side of the equator. The compass housing, where the needle is located, is slightly taller than those that are hemisphere specific. This allows the needle to move more freely inside. It also makes it easier to use while walking since it does not need to be held as flat. The MCB compass I have is made to be used in the northern hemisphere, so it needs to be held more consistently flat to function properly.

Now then. On to the parts. Opening the compass, you will see that there is a mirror in the lid and a needle in the base. You will also see a ring with numbers on it surrounding the needle. This is the bezel ring. Inside the bezel ring you should see an arrow that moves when you turn the bezel ring. This is the orienting arrow. Somewhere near the hinges on the base you may see an additional arrow. This is the directional arrow. Some compasses will have one orienting arrow on either side of the needle housing at the base of the lid. The MCB compass in the top photo shows two orienting arrows at the base of the lid. At the top of the lid, you will see a notch. Many compasses, though not all of them, also have a notch in the bottom of the lid. These notches are used for sighting and aiming the compass. Along with the notches, you may also notice a line down the center of the mirror. The line ensures that the compass is actually pointing where you are aiming.

Now that the basic parts are identified, it’s time to try shooting an azimuth. Hold the compass in a way that is comfortable but leave a finger or thumb free on both hands. You will need them to turn the bezel ring. I usually like to hold the compass so that my left thumb and right index finger can turn the bezel. Position the lid so that you can easily see the needle and the orienting arrow in the mirror. Find something to aim at and look through one of the notches to aim the compass. Look at the line on the mirror and make sure that it is directly in the center of the base. With the 360- or 0-degree mark on the bezel ring at the front near the hinges and the 180-degree mark on the opposite side, the line on the mirror should be directly on top of both numbers. The compass is now pointing directly where you are aiming it.

Once you have gotten everything lined up on the compass, rotate the bezel ring until the orienting arrow is directly underneath the north end of the needle. Many compasses will have an orienting arrow that is the same color as the north end of the needle. Green and red are both common, but the orienting arrow and north end of the needle are red on most of the compasses I have used. An easy way to remember how to line them up is to think of red in the shed. The red end of the north needle goes inside the red orienting arrow. With the needle and arrow lined up, take a look at the number at the top of the bezel ring. You have now taken an azimuth. A back azimuth is a related compass reading and is simply 180 degrees in the opposite direction. If your traveling azimuth is 90 degrees, or due east, your back azimuth will be 270 degrees, or due west. All this means is that your direction of travel will be 270 degrees to go back the way you came. In the last photo, my direction of travel is approximately 162 degrees. The approximate back azimuth to go back the way I came is approximately 342 degrees.

Congratulations, you have now taken an azimuth on a compass!

Check back for future posts on related material, including magnetic declination, using a compass with a map, and reading a topographic map.