Taking and following a bearing with a baseplate compass

A baseplate compass has three parts that work together: a transparent baseplate with a ruler and a direction-of-travel arrow, a rotating liquid-filled housing with a degree ring and parallel orienting lines, and the magnetic needle inside. The liquid calms the needle so that it does not keep trembling back and forth.

On the map you use the compass as a protractor. You lay the edge of the plate from your position to the destination and turn the housing until its orienting lines are parallel to the map's north–south lines. The needle plays no part in this. You can now read the direction as a number on the degree ring.

Outside, you turn with the compass in front of your belly until the red end of the needle sits exactly in the housing's orienting arrow. At that moment the direction arrow on the plate points exactly in the direction you measured on the map. Because the needle points to magnetic north and the map is aligned to a slightly different north, a correction may be needed – declination, whose value is printed on your map.

Hold the compass level, otherwise the needle drags and sticks. Hold it steady in front of your body and turn your whole body, not just your wrist. Make sure the needle sits with its red end in the orienting arrow – a very common mistake is to line it up with the white south end. Then you walk in exactly the opposite direction.

Keep away from anything magnetic or carrying current: phone, torch, knife, magnetic clasps on jackets or map cases, cars, fences, power lines. Even small objects close to the compass can noticeably deflect the needle.

Do not stare at the needle while walking. Pick a distinctive point in the arrow's direction – a striking tree, a rock – walk to it, and from there find the next one. You walk straighter that way and can watch the ground in front of you.

An angle error grows with every step. One degree off puts you about 17 metres beside your target after one kilometre; at five degrees it is almost 90 metres. In forest or fog that can be enough to walk past a hut without seeing it.

That is why experienced navigators always combine a bearing with other clues: how far have I walked? Which terrain features should be appearing now – a stream, the foot of a slope, a clearing? If these features fail to appear, they stop and reassess instead of simply walking on.

A useful technique is aiming off: if your destination lies on a long stream or path, you deliberately aim a little to one side. When you then hit the stream, you know exactly which way to turn.

A bearing is a straight line – the terrain is not. Never follow it stubbornly over cliffs, through water, across avalanche slopes or into gorges. Go around and then pick up the bearing again. If there is no safe way, turning back is the right decision.

A compass needs a known starting point. If you have no idea where you are, it can still show you a direction, but it cannot tell you whether that direction leads to your destination. In that situation the STOP rule comes first: stop, think, observe, plan.

Near the magnetic poles and in places with strongly iron-rich rock the compass becomes unreliable. For most hiking areas this is not an issue, but it is good to know if the needle behaves strangely.

Practise first on a field or in a park you know. Set a number, for example 90 degrees, and walk 50 paces in that direction. Then set 210 and walk another 50 paces, then 330 and 50 paces again. If you did everything right, you will be roughly back where you started – a triangle.

Then practise with a map: choose a point on the map that you can see, measure the direction and check whether the direction arrow outside really points at it. Try the back bearing too: to go back, turn until the red end of the needle sits in the south part of the housing, without changing the setting.

A compass is light, robust and needs no battery. A simple model with a rotating housing and a ruler is perfectly adequate for almost all hikes.