This article was updated on 27/10/2016
If you spend any time at all off the beaten track, you need to know how to find yourself using a map and compass.
True, modern smartphone technologies and navigation equipment are excellent at pinpointing your exact location, but all it take is for mobile service to drop out or for a battery do die to leave you high and dry. Technology should always be part of your backup plan in the outdoors.
If you’re going hiking, skiing the backcountry, or 4WDriving in the Outback, you should always take a map and a reliable compass so that you can locate your position and, in turn, work out how to get back the way you came. Learning the basic technique of triangulation is one step towards being able to navigate your way out of any potentially bad situation.
Important: Triangulation is one of many navigation techniques that you can use to get yourself 'unlost'. However, there are a number of situations in which it will not help you if you are lost in the outdoors, such as:
1. If visibility is poor, i.e. it's dark, foggy, or you are in dense bush.
2. You can locate a landmark but cannot accurately identify it on your map.
3. You can identify a landmark but it is so far away that it does not appear on the map you are carrying.
Before learning triangulation, it's important to understand its limitations in real-world situations and to know when to use alternative techniques.
To triangulate your position using a map and compass you will need:
A compass with a rotating bezel (housing)
A good map that is up to date - (hiking and camping stores offer good quality maps of the area).
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First up, let’s make sure we know the various parts of the compass, and how they work.
Parts of a Compass
Baseplate – the baseplate is the flat rectangular surface that you hold when using your compass. A good compass should have a clear baseplate.
Direction of Travel Arrow – this is the long arrow that points towards the top of the baseplate.
Ruler – you’ll notice the sides of your compass are marked like a ruler. This allows you to determine distance between points on a map depending on the maps scale and the scale represented on your compass’ baseplate.
Rotating Housing with Dial – the dial in the centre of your compass will rotate 360 degrees, and shows the cardinal points north, south, east, and west, and the degrees between them.
Orienting Arrow – on the rotating dial you’ll see that below the N for north, is either an arrow, or two lines running from north to south. Use the orienting arrow to line the dial up with the needle locating magnetic north.
Magnetic Needle – the red tip of the needle swings to point magnetic north independent from which way you rotate the baseplate.
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Magnetic North & True North
Did you know there are different types of north? At least in navigation there are. Magnetic north is the direction that the needle of your compass points to following the Earth’s magnetic field, while true north is the direction following a meridian line on a map towards the geographic North Pole.
These two points differ depending on where you are in the world, and will change slowly over time as the Earth’s magnetic field slowly moves. The difference between magnetic north and true north is called magnetic declination.
There are, however, places around the world in which true north and magnetic north line up perfectly. The Agonic Line runs from north to south along this point, and it is your position either side of the Agonic Line that determines whether you add, or subtract the magnetic declination in your area. Your map sure show you which side of the Agonic line you are located, but if not, check online before you leave.
How do you determine whether you add or subtract declination? It’s easy to remember: if you are east of the Agonic line and you are triangulating your position using field bearings, you add the declination to your bearing; if you are west, you subtract it. If you are converting a map bearing to the field, you reverse this process.
Hiking in the Cathedral Range State Park, VIC.
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A good hiking or backpacking map will show you the Magnetic Declination in your location. The angle between these two points is shown on the map in degrees, and in minutes east or west. Keep in mind that if you are using an old map, this figure may have changed, so it’s a good idea to update your map using figures found online before you leave on your trip
In Victoria, we are east of the Agonic line, so in the video above, we are adding our magnetic declination to our bearing.
Please note: the above video simplifies the process and assumes you have adjusted for magnetic declination which in this case is 11° 44’, east.
Finding north is a good exercise for working out the basics of how a compass works.
Finding North: a simple exercise to get started
To make sure you understand the various parts of your compass let’s find north.
Lay the compass flat allowing the needle to swing and settle at magnetic north.
Now turn while holding the compass to point the Direction of Travel Arrow in towards magnetic north, and rotate the housing so that the Orienting Arrow is also in line.
You should have all three pointing towards north. This is one of the steps you will take when finding your position on a map.
Finding yourself using a map and compass
In order to find yourself using a map and compass, you are going need a good view of your surroundings. Climb to a high point such as a ridgeline where you have a good view (ideally 360 degree) of the surrounding area. With a good view, your compass, and your map of the area, we can now go through the steps for pinpointing your location using two bearings, also known as Triangulation.
Example of a good view...
First, take note of the magnetic declination at your location. You are going to need to adjust your bearing for declination.
Next, find two landmarks: let’s say you can see a distant ridgeline, and an obvious valley in the distance. They should ideally be 60° apart to get an accurate reading.
Now, point the Direction of Travel Arrow at the ridgeline and allow the red tip of the needle to settle at magnetic north.
Rotate the housing so that the Orienting Arrow lines up with the Needle.
We can now read the bearing at the point where the Direction of Travel Arrow intersects the dial.
In this example the ridgeline is at 132° from north. We have added 11°, calculating for the magnetic declination displayed on our map, giving us a bearing of 143°.
We can now take our second bearing. Point your compass at the second landmark and repeat the process as before. In this example, the Valley is at 26° giving us a final bearing of 37°.
Now that we have our bearings we can apply them to the map.
To do this:
Lie your compass flat on the map, making sure you don’t move the housing.
Align needle (which should still be in line with orienting arrow) with north on your map. Your direction of travel arrow should be pointing in the direction of the landmark on the map.
Find your first landmark and lie your compass so that the corner of the baseplate touches it.
Draw a line that follows your bearing using the ruler on the edge of the baseplate. You can make the line as long as you like.
Repeat the process for your second bearing.
The point where the two lines meet is where you are!
Note: if you already have one point of reference, such as the trail you are hiking on, you only need to take one field bearing as the point where that bearing intersects the trail on the map will show you where you are. This is known as Free Triangulation.
There, you’ve found yourself in the wilderness. If that was all a bit much, make sure you watch the video, it’ll help the steps sink in. Get out there and practice, ideally somewhere close to home at first so that next time you are off-piste, or off-road, you know how to pinpoint your location and get home safely.