Compass Background

Compass Background

Background information about compasses

Compass Background 

Compass Background Information

What is a Compass Used For?

A compass is used to ensure that you travel in a particular direction, or to check your position against a known land feature. For most outdoor navigation, use of a compass goes hand in hand with a map.

What is a Compass?

A compass for use in the outdoors is a precision instrument containing a magnetized needle (or pointer) that shows the direction of magnetic north and bearings from it. The needle is suspended in liquid, resting on a tiny pivot so that contact between needle and pivot is not affected by friction. The red side of the needle always* points to magnetic north, with the white side always pointing south.

In the outdoors a compass is used to determine or confirm your direction, or to confirm your position, and is really only of used when used with a map. There may be times when a compass is used without a map, for example when a quick check of general direction is required, but normally a map and compass go hand in hand.

*See Magnetic Anomalies & reverse polatity

Cardinal Points

There are four cardinal points on a compass, being north, south, east and west.

Further divisions of the compass are sub cardinal points, being north east, south east, south west and north west, and these are useful for general descriptions of direction. However, in practice you will describe direction by degrees, as it’s more precise and not open to interpretation.

Left and Right

In everyday life you may talk about and give directions in terms of ‘left and right’, but when navigating you must always refer to points of a compass or degrees rather than left or right. This is because the true direction of left and right depend on which way you’re facing.

The Outdoor or Base Plate Compass

For the purposes of outdoor navigation, the compass we’re interested in is one that has a base plate, as it’s the base plate that is the connection with your map, both from a physical and navigational theory perspective. Compasses without a base plate cannot be used properly with maps and have no place in outdoor navigation.


Some compasses have a fold-down mirror, which is used to increase the accuracy of navigating, in particular when using land to map bearings (or signed bearings). However, the drawbacks of a mirrored compass is that they cost more in the first place, and a more likely to break than a traditional baseplate compass.

Compass Storage

Keep your compass handy so that you can use it as required, rather than having it stored in a rucksack, meaning that you're less likely to use it. Also ensure that you don't keep the compass next to anything magnetic, in particular a mobile phone (which contain magnetic in speakers). Exposing a compass to magnets can result in reverse polarity, meaning that the compass points the opposite way.