Compass and Mapping techniques

The compass is a very versatile instrument. Although it has been succeeded with the more modern and precise GPS (Global Positioning System) it's simplicity will help you out in any survival situation. The compass maybe used for hobby purposes or for trekking along in the countryside. These articles will explain the correct use of a compass and several applications of it. If you already know about the compass feel free to jump to any section listed below.

Contents Introduction and types of compasses Description of the compass The map - Types and Symbols  Setting the map Bearings and back-bearings Finding your exact location by triangulation The romer card and 6 digit representation Let's plot and adventure together!!

Section 1 : Types of compasses

These are several types of compasses in use. They range from the very simple to more advanced types. The simple Silva model which only consists of the magnet and an orienteering arrow. This is a beginners compass and for occasional use it it the beast choice. It has a resolution of 2º and has markings in centimeters and inches. The base is transparent so it can be used directly on a map.

The are other compasses for other types of activities such as waterborne compasses, compasses held like a wristwatch. Some even come with a whistle! They all have varying degrees of resolution either 10º, 5º or 2º. They come in different sizes  shapes and weight.

For the enthusiast or  someone preparing for an long trek and needs a reliable compass there are compasses with a sighting mirror, high resolution 2º, luminous points and romer scales. If you are preparing a survival kit, for example you are going abroad, in a politically unstable country your best investment would be in a military compass with has been tested in both temperature extremes, -40ºC to +150ºC.

Section 2 : Description of the compass

In this compass tutorial we shall focus and use the simple Silva type compass. Shown below is a diagram and it's associated explanations.

This is the basic type of compass.  Let's us begin with our first lesson. Note the following:

• DO not take a reading near metallic objects. This will result in an error. Over large distances errors may put off course by miles. The compass may even lose it's magnetic charge. Here is a simple way to check your compass. 

Hold the compass and see where the North is, and memorize the position. Now go to another part of the room and let it settle to the North position again. If these two are the same than the compass is OK. If it is rotating or it is in a wrong position then there is a chance that it has been de-magnetized. Then your best option is to get a second compass and compare them together. Do not let them come near each other as they will interfere with each other.

• When taking a reading always hold the compass in a horizontal position. The needle may be placed either in oil for professional compasses to stop quickly or else in air. If the compass is pointed down an incorrect reading will result.

• When taking a reading always let the compass come to rest.

We are now prepared to use our compass for the first time. Take a distance from the computer ( It generates magnetic fields ) let the compass find North. Rotate the dial till the N position is aligned with the needle and both are aligned with the direction arrow. They should be aligned as shown in the first diagram.

Now you are supposed to be standing to the magnetic North pole. Suppose we want to move in a 060º direction. Now there are two ways of specifying direction. The first is in decimal notation from 0º to 359º. The second is by specifying directions such as NE for 045º or 30º South for 210º. In this tutorial we shall use the first notation.

So back to our subject. Turn till the direction arrow is aligned with the 60º mark on the dial. Now you are facing the direction we want to move. If this was a real situation we would sight an object about 150m away, put the compass in out pocket and walk towards this objective. When we would reach it we would repeat the same process sight another objective and repeat it till we would arrive. This would cancel out the effect of any detours and inaccuracies. 

On to the next part