How to use a compass
Using the compass alone
The first thing you need to learn, are the directions. North, South, East and West. Look at the figure and learn how they are. North is the most important.
There are several kinds of compasses, the one I would recommend:
You see this red and black arrow? It is called the compass needle. On some compasses it might be red and white for instance, but the point is, the red part of it is always pointing towards the earth’s magnetic north pole.
But if you don’t want to go north, but a different direction? You’ve got this turnable thing on your compass. It’s called the Compass housing. On the edge of the compass housing, you will probably have a scale. From 0 to 360 or from 0 to 400. Those are the degrees or the azimuth (or bearing). As well as the letters N, S, W and E for North, South, West and East. If you want to go in a direction between two of these, you would combine them. If you would like to go in a direction just between North and West, you simply say: “I would like to go Northwest “.
Let’s use that as an example: You want to go northwest. What you do, is that you find out where on the compass housing northwest is. Then you turn the compass housing so that northwest on the housing comes exactly there where the large direction of travel-arrow meets the housing.
Hold the compass in your hand. And you’ll have to hold it quite flat, so that the compass needle can turn. Then turn yourself, your hand, the entire compass, just make sure the compass housing doesn’t turn, and turn it until the compass needle is aligned with the lines inside the compass housing.
Now, time to be careful!. It is extremely important that the red, north part of the compass needle points at north in the compass housing. If south points at north, you would walk off in the exact opposite direction of what you want! And it’s a very common mistake among beginners. So always take a second look to make sure you did it right!
A second problem might be local magnetic attractions. If you are carrying something of iron or something like that, it might disturb the arrow. Even a staple in your map might be a problem. Make sure there is nothing of the sort around. There is a possibility for magnetic attractions in the soil as well, “magnetic deviation“, but they are rarely seen. Might occur if you’re in a mining district.
When you are sure you’ve got it right, walk off in the direction the direction of travel-arrow is pointing. To avoid getting off the course, make sure to look at the compass quite frequently, say every hundred meters at least. But you shouldn’t stare down on the compass. Once you have the direction, aim on some point in the distance, and go there. But this gets more important when you use a map.
There is something you should look for to avoid going in the opposite direction: The Sun. At noon, the sun is roughly in South (or in the north on the southern hemisphere), so if you are heading north and have the sun in your face, it should ring a bell.
When do you need this technique? If you are out there without a map, and you don’t know where you are, but you know that there is a road, trail, stream, river or something long and big you can’t miss if you go in the right direction. And you know in what direction you must go to get there, at least approximately what direction. Then all you need to do, is to turn the compass housing, so that the direction you want to go in, is where the direction of travel-arrow meets the housing. And follow the above steps. But why isn’t this sufficient? It is not very accurate. You are going in the right direction, and you won’t go around in circles, but you’re very lucky if you hit a small spot this way. And that’s why I’m not talking about declination here. And because that is something connected with the use of maps. But if you have a mental image of the map and know what it is, do think about it. But I think you won’t be able to be so accurate so the declination won’t make a difference.
If you are taking a long hike in unfamiliar terrain, you should always carry a good map that covers the terrain. Especially if you are leaving the trail. It is in this interaction between the map and a compass, that the compass becomes really valuable.
How to use a compass
Using the compass in interaction with a map
First, a quick summary of what you will learn in this lesson:
- Align the edge of the compass with the starting and finishing point.
- Rotate the compass housing until the orienting arrow and lines point N on the map.
- Rotate the map and compass together until the red end of the compass needle points north.
- Follow the direction of travel arrow on the compass, keeping the needle aligned with the orienting arrow on the housing.
Here is our compass again:
The principles are much the same as in lesson 1 but this time, you are using the map to tell you which way is correct instead of your intuition.
Take a map. In our first example, we look at a map made for orienteering. You want to go from the trail-crossing at A, to the rock at B. Of course, to use this method successfully, you’ll have to know you really are at A. What you do, is you put your compass on the map so that the edge of the compass is at A. The edge you must be using, is the edge that is parallel to the direction of travel arrow. And then, put B somewhere along the same edge, like it is on the drawing. Of course, you could use the direction arrow itself, or one of the parallel lines, but usually, it’s more convenient to use the edge.
Time to be careful again! The edge of the compass, or rather the direction arrow, must point from A to B! And again, if you do this wrong, you’ll walk off in the exact opposite direction of what you want. So take a second look.
Keep the compass steady on the map. What you are going to do next is that you are going to align the orienting lines and the orienting arrow with the meridian lines of the map. The lines on the map going north, that is. While you have the edge of the compass carefully aligned from A to B, turn the compass housing so that the orienting lines in the compass housing are aligned with the meridian lines on the map. During this process, you don’t mind what happens to the compass needle.
There are a number of serious mistakes that can be made here. Let’s take the problem with going in the opposite direction first. Be absolutely certain that you know where north is on the map, and be sure that the orienting arrow is pointing towards the north on the map. Normally, north will be up on the map. The possible mistake is to let the orienting arrow point towards the south on the map. And then, keep an eye on the edge of the compass. If the edge isn’t going along the line from A to B when you have finished turning the compass housing, you will have an error in your direction, and it can take you off your course.
When you are sure you have the compass housing right, you may take the compass away from the map. And now, you can in fact read the azimuth off the housing, from where the housing meets the direction arrow. Be sure that the housing doesn’t turn, before you reach your target B!
The final step is similar to what you did in lesson 1. Hold the compass in your hand. And now you’ll have to hold it quite flat, so that the compass needle can turn. Then turn yourself, your hand, the entire compass, just make sure the compass housing doesn’t turn, and turn it until the compass needle is aligned with the lines inside the compass housing.
The mistake is again to let the compass needle point towards the south. The red part of the compass needle must point at north in the compass housing, or you’ll go in the opposite direction.
It’s time to walk off. But to do that with optimal accuracy, you’ll have to do that in a special way as well.
Hold the compass in your hand, with the needle well aligned with the orienting arrow. Then aim, as careful as you can, in the direction the direction of travel-arrow is pointing. Fix your eye on some special feature in the terrain as far as you can see in the direction. Then go there. Be sure as you go that the compass housing doesn’t turn. If you’re in a dense forest, you might need to aim several times. Hopefully, you will reach your target B when you do this.
How to use a compass
For the absolute beginners, it is important that they master the techniques described in lesson 1 and 2. This can be done partially with practice without going anywhere. In this first exercise the aim is solely to choose the right control from several you can see. This way, you get practice, but need not fear getting lost. It requires some work done, however. Check out this figure:
To the right is a map of your backyard. In the middle is a symbol , which is a symbol used in orienteering to denote start and finish when they are at the same place (Otherwise, start is a triangle, and finish two concentric circles). There are controls all around you, and all of them can be seen from this center.
A control, as used in orienteering, looks like
and they are placed in all the circles. The map here is of course an imaginary map, and you would have to draw a map of your own back yard. The scale isn’t very important, but it has to be correct with regards to the compass. Also on the figure above is a detail from the upper left corner of the map as it would look in the real (imaginary…) world. You should draw all buildings, large rocks, bushes and trees and other features you see, like you see from the detail.
Let’s move to the bush. Compass usage is most important when you haven’t got any other features to guide you, such as paths, streams etc. This makes things more difficult, of course, and it is easier to get lost. Which means we are talking about the feared “feeling of being lost”. Therefore, it is essential to plan the exercises with a “security net”, so there is no chance of really getting lost. This is achieved by ensuring there are features like roads, large paths, streams etc. that can’t be missed, if the control is missed.
It may be a good idea to put the start at a point that is visible from quite a distance, like a tower, for instance (the ‘T’ in the start symbol means tower). This time, the place you use should be covered by a real map, preferably with a large scale. Two controls are indicated as examples. Neither of the controls are visible from the start, which means you would need to use more techniques to get there. While only two controls are indicated here, there are supposed to be controls all the way around, like in the previous example. And also like in the previous example, they are supposed to run back and forth. The distance from the start should be around 100 meters, and must not be more than 200 meters.
This is the greater challenge. This is a real orientering map, “Eggemoen”, published by Ringerrike Orienteringslag©, used here with permission. The first control is the easiest. One crosses several roads and paths on the way to the control, and there are paths leading into the control from each side. The crossing of roads has mainly two purposes: You can see how far have gone, and secondly, it helps to build confidence. It doesn’t play a very important role in finding the control, because the compass is supposed to play the main role in that. It can be used to correct the bearing if it is obviously wrong though. The control has also a “security net” – the road just after the control. If the control is missed, it provides a way to get back in, a detail that cannot easily be mistaken. The red arrow indicates such a detail.
How to use a compass
There is something called magnetic declination. You see, the compass is pointing towards the magnetic north pole, and the map is pointing toward s the geographic north pole, and that is not the same place. To make things even more complicated, there is on most hiking-maps something (that is very useful) called the UTM-grid. This grid doesn’t have a real north pole, but in most cases, the lines are not too far away from the other norths. Since this grid covers the map, it is convenient to use as meridians.
On most orienteering maps (newer than the early 70’s), this is corrected, so you won’t have to worry about it. But on topographic maps, this is a problem. First, you’ll have to know how large the declination is, in degrees. This depends on where on the earth you are. So you will have to find out before you leave home. Or somewhere on the map, it says something about it. One thing you have to remember in some areas, the declination changes significantly, so you’ll need to know what it is this year.
If you are using a map with a “UTM-grid”, you want to know how this grid differs from the magnetic pole.
When you are taking out a course, you will do that more or less as described in lesson 2,
but this time, you must also look out so that you don’t align the orienting lines with the grid lines pointing west or east, or south for that matter. When you have taken out a course like you’ve learned, you must add or subtract an angle, and that angle is the angle you found before you left home, the angle between the grid lines or meridians and the magnetic north.
The declination is given as e.g. “15 degrees east”. When you look at the figure, you can pretend that plus is to the right, or east, and minus is to the left and west. Like a curved row of numbers. So when something is more than zero you’ll subtract to get it back to zero. And if it is less, you’ll add. So in this case you’ll subtract 15 degrees to the azimuth, by turning the compass housing, according to the numbers on the housing. Now, finally, the direction of travel-arrow points in the direction you want to go. Again, be careful to aim at some distant object and off you go.
You may not need to find the declination before you leave home, actually. There is a fast and good method to find the declination wherever you are. This method has also the advantage that corrects for local conditions that may be present. This is what you do:
- Determine by map inspection the grid azimuth from your location to a known, visible, distant point. The further away, the more accurate it gets. This means you have to know where you are, and be pretty sure about one other feature in the terrain.
- Sight on that distant point with the compass and note the magnetic azimuth. You do that by turning the compass housing so that it is aligned with the needle. You may now read the number from the housing where it meets the base of the direction of travel-arrow.
- Compare the two azimuths. The difference is the declination.
- Update as necessary. You shouldn’t need to do this very often, unless you travel in a terrain with lots of mineral deposits.
You can’t always expect to hit exactly what you are looking for. In fact, you must expect to get a little off course.
How much you get off course depends very often on the things around you. How dense the forest is, fog, visibility is a keyword. And of course, it depends on how accurate you are. You do make things better by being careful when you take out a course, and it is important to aim as far ahead as you can see.
In normal forest conditions we say that as a rule of thumb, the uncertainty is one tenth of the distance traveled. So if it is like in the figure, you go 200 meters on course, it is possible that you end up a little off course, 20 meters or so. If you’re looking for something smaller than 20 meters across, there is a chance you’ll miss. If you want to hit that rock in our example, you’ll need to keep the eyes open!
In the open mountain areas, things are of course a lot easier when you can see far ahead of you.