There are so many global positioning systems (GPS) out there from high-accuracy, heavy-duty units that cost thousands all the way down to completely free smartphone applications. In this age of technology, many may wonder, “who needs a compass anyway?” But the truth is that knowing how to use a magnetic compass can still be a very useful skill to have in your quiver.
A compass is superior to a GPS unit in many ways. It is small, lightweight, cheap, needs no power source, apart from the magnetic field of the earth of course ;-), and can be used even under thick cloud cover, tree canopy or other situations where you can’t see the sky and therefore may not have access to GPS satellites.
That being said, of course, a magnetic compass still has a couple of drawbacks. Namely, the requirement to develop skill in order to use it effectively, and the possibility of disruption by other nearby metals (we’ll go over how to account for this later). However, developing the skills to use a compass is not too difficult to do and is very satisfying once mastered.
In this article, you will learn what features to look for in a compass, get an introduction to declination, learn how to take and follow a bearing in the field, and learn how to avoid false compass readings.
Choosing a compass
Before you can learn how to use a compass, it is necessary to make sure to choose a compass that will be useful to you in your two-foot travelling pursuits. There are many varieties you can find, and some will either be too complex or too simple.
When you choose your compass you will need one with the following features:
- A transparent rectangular base plate
- A freely rotating magnetic needle
- A dial around the circumference of the housing graduated clockwise in 2-degree increments
- A set of meridian lines
- An index line
- An orienting arrow
If your compass is missing any of these features, you will not be able to use it effectively to navigate in the backcountry. You can find a good compass with all the necessary components for around $20. I use a Silva Polaris. Silva is a good brand that makes many different compasses. A beginner compass like this Silva Starter has all the necessary bells and whistles and is an excellent value for the price.
You may also want to purchase a compass with adjustable declination like this Silva Ranger or this Suunto MC-2. This raises the price tag up to around $50, but if you are planning on doing a lot of compass navigation it may be worth it. If you don’t want to shell out an extra 30 bucks, don’t worry, there are ways to use a compass without adjustable declination just as effectively.
So what’s all this I’ve been hearing about true North and magnetic North?
You may have heard the terms, true North and magnetic North and wondered what the difference between them is. Well, the short answer is that true North is the top of the globe or the north pole. And magnetic North is based on earth’s magnetic fields. Magnetic North is the place the needle on your compass actually points to. So don’t follow it expecting to find Santa’s house.
The difference between true North and magnetic North is called the declination and depends on where you are standing on the earth.
This is all further complicated by the fact that magnetic North fluctuates and changes over time and by extension, so does declination. The declination of your hometown today is different than it was 5 years ago and different than it will be in five years time.
If you have a good topographic map, which is one of the survival essentials, it will list the declination at the bottom, however, if your map is old it will likely be a little off. Luckily, you can use the NOAA Magnetic Field Calculator to find the current declination anywhere on earth.
So does all this declination stuff really matter, and is it relevant to you? The answer is yes and no, it depends on what you would like to do with your compass. If your buddy gives you a direction to follow that will lead you to a hidden cave from your campsite and uses magnetic north without adjusting for declination, then you don’t have to adjust either.
But if you want to start doing anything much more complicated than that, like orienting your map so that it matches up with the actual land features for example, then you need to know how to account for declination.
There are a few different ways to adjust for declination. One of them is to purchase a compass with the ability to adjust built in, as discussed earlier. Another option is addition and subtraction. And the third option is to just use a wet erase marker to mark the declination on your compass.
We’ll talk more about when and how to account for declination, as well as how to use a compass with a map, in a later post. There’s a lot to learn about using a compass, so in order to avoid getting overwhelmed with everything all at once, for now, let’s just start with the basics.
What in the world is a bearing?
A bearing is a precise description of a direction. If you take a look at your compass you’ll see a dial around the circumference of the housing printed with the cardinal directions, North, South, East, and West. This is called the rotating bezel or the azimuth ring.
On the bezel outside of the cardinal directions there are 360-degree markings, and if you chose a good compass these should be measured in 2-degree increments. Basically, a bearing is a degree measurement of direction. So a bearing of due south would be 180 degrees.
You can use bearings to communicate a precise direction you want someone to follow.
Let’s say your friend is off on a backpacking trip to your favorite area, and you want to tell her where the best campsite is. If you can give her a landmark to start at, a bearing to follow, and a description of where to stop, she will be able to find your campsite.
The process of taking and following field bearings is relatively simple and a good starting point in learning to use a magnetic compass. So let’s try it.
Meet Fred, he’ll help you with your field bearings
Did you know that the red portion of the magnetic rotating needle on your compass has a name? His name is Fred. And it’s important to get red Fred into his red shed, otherwise known as the orienting arrow.
When you want to take a field bearing begin by holding the compass flat in your hand and pointing the direction of travel arrow (the big arrow at the top of the compass) toward a landmark in the desired direction. Then, without moving the compass body, rotate the bezel until the magnetic needle is within the orienting arrow, or in other words until the shed meets Fred.
Once Fred is inside his shed you can read the bearing at the index line. It’s that easy!
The process of following a field bearing is similar. Let’s say your friend tells you there’s a hidden waterfall 240 degrees from the giant ponderosa pine in your campsite. Stand at the ponderosa pine and rotate the bezel until the 240-degree mark is at the index line. Then, keeping the compass flat in your hand, rotate your body until Fred is in his shed. Then follow the direction of travel arrow until you reach the waterfall
You can combine multiple bearings and landmarks to give someone precise directions to a desired point. Just remember that any bearing is relative to where you are standing. If your friend tells you to follow the bearing from the ponderosa pine and instead you start from the firepit, you won’t end up in the right place!
Video tutorial coming soon
False readings and magnetic anomalies
Because a compass works via the attraction of a small magnet to the magnetic field of the earth, metal objects may deflect the magnetic needle resulting in false readings.
It is important to keep this in mind while you use your compass. For example, don’t hold the compass with the same hand as your wristwatch. Other metal objects to avoid include cell phones, keys, power lines etc. This is also why your compass will probably not be accurate indoors as there are likely many metal objects within your home and any other buildings you may be in.
Many rocks that are found in nature are also magnetically active.
Some parts of the earth are so filled with these rocks that they create a magnetic anomaly or a place where your compass will absolutely not work. There are magnetic anomalies in many parts of the earth including the Kursk area of Russia, Mt. Jim in Australia, and the lava flows of the El Malpais in New Mexico.
These areas are well documented, however it is possible that you may come across a local magnetic anomaly in your travels. The anomalies that you encounter will likely have a small enough influence that they shouldn’t disrupt your bearing for long.
However, it still pays to be wary of them. The solution to this problem is to frequently check the consistency of your bearing along a transect or line.
To do this identify two points (such as tree’s or features) that are lined up straight in front of you. Take a bearing with the two points lined up, then walk forward several feet straight towards your points (at least 100-150 yards). Take another bearing with the objects still lined up.
If the bearings are very different it means one of them was affected by a magnetic anomaly. 1
Practice, practice, practice
Congratulations, now you know how to choose a great compass, and use it to take and follow field bearings effectively. This is an excellent start. There are a few more compass related skills you need to learn before you’re ready to throw out the GPS and go compass-solo in the wilderness.
So don’t forget to practice. You can practice in a city park or even your backyard. You can even practice with a friend and give each other bearings to follow. You can even practice taking bearings along a transect to check for a magnetic anomaly. (Who knows you may find one) Once you are confident with your field bearing skills, you will be ready to move onto the next steps.
Check out this post to learn about reading a topographic map.
And stay tuned for a post on how to use a compass and a map together, coming soon. You can also refer to this excellent REI article for further reading in the meantime.
Soon you will find your newfound compass skills beginning to serve you well as a great backup to your GPS unit and you will even be able to navigate entirely by compass and map alone, in no time.
As always if you have any questions or comments please feel free to contact me or leave a comment below.
Now get out there and get adventuring!