The Compass
There are several types of compass availible on the market. The price may vary from £10.00 for a basic model to £20.00 for a model with more scales. As a general rule the price will increase as more scales are added to the base. A typical compass is shown below. Note that there are likely to be more scales on a real compass.
The first use of the compass is to orientate the map. This means that the compass is used to line the map up in such a way that the features around you are in the correct place when you look at the map. It is not always necessary (and in fact it is better not to if possible) to use the compass for this. You could use known or recognizable features around you to perform this task. For example assume you are at the cross on the map (and know this since it is a peak). You can see the lake and the peak shown on the map in good visibility. You can rotate the map so that these line up appropriately and therefore you can identify the point labeled with a star.
If you cannot do this using features then you should use the compass to line up North on the map with North on the ground. The map will then be pointing the same way as if you had orientated it using features on the ground.
The main use of the compass is for navigating in poor visibility. It should be used along with the techniques of timing and pacing. Here will will discuss how to take a bearing from the map and follow it. We will assume that we wish to go from the blue dot to the green dot.
1. Put the compass on the map ensuring that the base is aligned with the points which you wish to move between. The direction of travel indicator should point the way you want to go.
2. Rotate the compass housing so that the orienting lines are lined up so the red north arrow on the housing points to grid north. Note it does not matter which way the needle is pointing.
3. Take the compass away from the map, and add magnetic deviation to the bearing. At the time of writing this was 4º. It varies depending on where in the world you are. It also reduces by approx ½º every 4 years.
4. Take the compass and whilst keeping it flat, rotate the whole compass so that the needle is in the center of the red arrow on the housing.
5. Looking down on the compass follow the direction arrow to a feature such as a large rock (but not a moving one such as a sheep). Now walk to this feature keeping track of the distance walked. Now find another feature in the same way, and continue till you reach your destination.
It is possible to reverse this procedure, and take a bearing from the ground and convert it to the map. This is usually done to check the bearing of a wall for example, or to pinpoint your location using features such as lakes and peaks. To do this
1. Point the direction arrow along the line of the wall or to the feature.
2. Rotate the housing so that the needle is within the red section of the housing.
3. Subtract magnetic deviation.
4. Place the compass on the map and line up the housing with the grid lines.
5. The direction arrow now points in the direction of the wall, or towards the feature from where you are.
By using this technique with two (or better still three) features you can locate your position on the map.
These are the main uses for the compass, and they should be practiced in good visibility so that they can be applied in poor weather when you will really need them. The most common mistake is to be 180º out because you have lined the housing up incorrectly, or pointed the compass in the wrong direction on the map. It is best to guess the bearing first and this mistake will then become obvious.
FINALLY, ALWAYS TRUST THE COMPASS
Last updated: 11/09/01