Why the mist changes the rules

On a bright day most of us navigate with our eyes. We spot the ridge ahead, line up a gully, wander a little and correct. In mist, visibility can drop to thirty metres and every one of those cues vanishes. The landscape becomes a grey room with no walls, and the only thing telling you where you are is the map, the compass and your own careful counting.

The good news is that nothing here is complicated. It is a handful of simple skills, and they only work if you have practised them somewhere safe before the cloud comes down on a long day out.

Before you leave the car park

Poor visibility navigation is mostly about preparation. Fold the map so the relevant section faces you, keep it in a clear case, and keep a thumb on your current position. A map that has to be unfolded and refolded in a wet wind is a map you will not use.

• Check your compass before you set off: the bezel should turn smoothly, the needle should settle without sticking, and there should be no bubble in the capsule.
• Wear the compass on a lanyard so it cannot be dropped in heather or blown off a summit.
• Read the magnetic variation printed in the map margin. In the UK it is small — usually a degree or two — but on long legs it is worth adding to bearings taken from the map.
• Keep a spare compass and a headtorch in your pack. Phone batteries die fastest when you need them most.

Taking a bearing and walking on it

A bearing is simply the direction you want to travel, measured in degrees. Take it like this:

• Lay the compass on the map with its long edge along your intended line of travel, the direction-of-travel arrow pointing the way you want to go.
• Turn the bezel until the orienting lines are parallel with the map's north–south grid lines, with the orienting arrow pointing to the top of the map.
• Read the number at the index line. That is your grid bearing. Allow for magnetic variation on longer legs.
• Hold the compass flat at waist height and turn your whole body until the red end of the needle sits inside the orienting arrow. The direction-of-travel arrow now points where you want to go.

The classic mistake is walking with your nose glued to the compass, drifting slowly off line. Instead, look up, pick a feature that sits on the bearing — a boulder, a peat hag, a distinctive tuft of grass — walk to it, then take the bearing again. In thick mist, shorten the legs to fifty or a hundred metres.

Two refinements are worth knowing. A back bearing, taken on the reverse direction, tells you whether you have drifted. And aiming off — deliberately heading a few degrees to one side of your target — means that when you meet a wall, stream or track you know which way to turn rather than guessing.

Pacing, timing and leapfrogging

Distance matters as much as direction. On level ground an average adult takes roughly 65 double paces per 100 metres, and rather more going uphill or through bog. Count in blocks of a hundred paces so you do not have to hold a large number in your head.

Timing works alongside pacing. A common rule of thumb is four kilometres per hour on a good path, plus about a minute for every ten metres of ascent, and considerably slower in deep heather or soft snow. If your pacing and your timing agree, you can trust your position.

If you are walking with someone else, leapfrog. One person stays put while the other walks forward on the bearing, then stops and is waved left or right into line. It is slow, it is sociable, and in genuine white-out it is the most reliable method there is.

Reading contours when you can see nothing

Contours on both 1:25,000 and 1:50,000 maps are usually drawn at ten-metre intervals, which makes them a measuring tool. Counting three contours up from a stream crossing means you have climbed thirty metres — enough to tell you roughly where you sit on a slope.

The shapes matter too. Contours that form a V pointing uphill are a re-entrant; a V pointing downhill is a spur. Tightly packed lines mean steep ground, widely spaced lines mean gentle ground, and black hachures mark crags you should not be walking over in mist. Closed loops mark summits, hollows — and tarns, which sit in their own little bowl and appear as a small blue shape inside a ring of contour.

Pair contours with handrails — walls, fences, streams, ridgelines — that you can follow, and catching features that will stop you if you overshoot: a loch shore, a forestry edge, a road.

Bothies, tarns and the value of practice

A grid reference for a bothy is not the same as finding it. A small building in a big landscape is easy to miss, so approach it along a handrail — a burn or a boundary wall — and aim off to one side. Then, when you meet your handrail, you know exactly which way to turn. Tarns make excellent targets for the same reason: a shoreline is large, obvious and unambiguous. Hit it, then follow it round to the outflow or the spur you want.

Practice deliberately. Choose a familiar hill, wait for a misty day, and spend an hour walking 200- and 400-metre legs on a bearing, checking each one off against features you already know. Add pacing, then add a contour interpretation exercise on a slope you can see through gaps in the cloud. Do it again after dark.

Build the skills slowly, in small doses, on ground where a mistake costs nothing but pride. Then, when the cloud really does come down on a remote plateau far from the nearest bothy, you will already know how to walk yourself home.