Map Reading

Beginner’s guides

A beginners guide to the compass

By Jonathan Elder

Published on May 1, 2022 4 min read

Types of compass and their features

Improve your map reading skills with this beginner’s guide to the compass. We take a look at the different types of compass, such as a baseplate compass, and explain how to orientate a map with one.

Whether you are out walking or cycling or simply driving somewhere new, being able to use a compass is a great skill that will always come in handy. Rather than just showing north, modern compasses have many features to assist in planning and navigation.

Without a compass, you can still use your map by relying on visible features, but a compass allows you to be more accurate and navigate where there are few obvious landscape features,

Navigation Skills for Walkers

Types of compass

There are loads of magnetic compasses available, from ones attached to penknives to huge, expensive ships compasses. Here’s some of the most common:

Basic compass

Silva Pocket Compass

This will tell you which way is north, but without a rotating bezel or an easy way of alignment, it will never be very accurate. They are inexpensive, but very cheap ones can be poor.

Best for: driving and road cycling where you only need the approximate direction, or as an emergency spare

Baseplate or orienteering compass

OS Compass

This is probably the most flexible type, as it can be used for taking bearings, setting a heading and measuring distances. The clear base allows it to be laid on top of the map.

Best for: accurate navigation with a map

Mirror compass

OS Mirror Compass

Some more advanced compasses have mirror housing. The mirror allows the user to see the bezel and the landscape at the same time improving accuracy.

Best for: long treks in pathless terrain

Sighting compass

Source: Wikimedia commons – Adamantios

This compass is designed to make it easy to take a bearing from a distant object, and are still often used by the military. They don’t have all the features you may want, but can be very accurate.

Best for: Using triangulation to work out exactly where you are

Which compass is best for me?

Know your compass

A compass and its features

Baseplate – The mounting of the compass. Clear, so when placed on top of the map you can still see the map features

Compass housing – Contains the magnetic needle and has the points of the compass printed on a circular, rotating bezel.

Compass needle – Floats in liquid so it can rotate freely but without being too sensitive to movement, the red end points to magnetic north.

Orienting lines – Fixed within the compass housing and designed to be aligned with the eastings on a map.

Orienting arrow – Fixed within the compass housing, aligned to north on the housing. Enables conversion between grid and magnetic north.

Magnetic variation – allows accurateadjustment for magnetic variation or declination

Index line – Fixed beneath the rotating bezel of the compass, it marks the bearing you wish to travel along.

Direction of travel arrow – Shows the direction that you want to travel along once you have taken your bearing. It is an extension of the index line.

Compass scale – Displayed along the edge of the base plate so you can measure distances on maps.

Features of a compass with Steve Backshall

Using your compass

How to orientate a map

Where do you want to go?

From your starting point on the map, place the index line on an imaginary line between where you are now and where you want to be – with the direction of travel arrow on the base plate pointing the way. Start by drawing a line from A to B now.

Holding the baseplate in place, rotate the compass housing so the orienting arrow lines up with grid north on the map. The orienting lines should be parallel with the vertical blue grid lines (eastings).

Adjust for magnetic variationim

Your compass does not point to grid north. Magnetic north throughout Great Britain can range from 0º to 5º. The amount of variation changes every year, so check your OS map to work out the most current value. You’ll find this in the map legend. Add magnetic variation to your bearing by rotating the compass housing.

Adjust the compass, line up the arrow and follow the direction of travel

Take your compass off the map. Hold your compass flat at waist height and turn yourself until the red needle meets up with the letter N and is positioned over the orienting arrow. You’re ready to go. The red direction of travel arrow will point the way.

Compass readings are also affected by the presence of iron and steel objects, so be sure to look out for – and stay away from – pocket knives, belt buckles, mobiles and GPS devices when using your compass.

Beginners guide to using a compass

How to take a compass bearing with Steve Backshall

​Top tip

The red end of the compass points to north, the black end points to south

Using land features instead

As an alternative to using a compass to orientate your map, you can use your eyesight. This method will only work if you are in an area with visible prominent features or landmarks. First, locate yourself next to a feature or landmark and place your finger on the map at the point where you are standing. Then begin to rotate the map so that other features and landmarks on the map begin to line up with the actual ones you can see. The map is now orientated with the land, although not as accurately as it would be using a compass.

For more information on map reading, take a look our collection of guides. We have those for beginners just starting out on their map reading journey, as well as those who are more advanced and looking to hone their skills or set themselves a challenge.

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By Jonathan Elder

Jonathan helps run the OS Shop and GetOutside, and in his free time can be found walking, playing computer games or, in the winter, falling off mountains with a plank of wood strapped to his feet.