Why poor visibility changes everything

On a clear day, navigation is mostly confirmation. You can see the ridge or path and match it to the map. Fog, darkness, heavy rain or snow removes those confirmations. You are left with a bearing, a distance and your discipline. So practise on ordinary days, when you can check your answers against the real world.

Poor visibility also slows you down. A three-hour route in sunshine may take five in mist. Add tiredness, cold and a headtorch, and small errors grow. Build a simple routine that works when you cannot see the next marker.

• Plan for less distance: allow extra time and choose a shorter, lower route if cloud or darkness is likely.
• Carry the right tools: a map, a compass, a headtorch with spare batteries, a whistle, extra layers, food and water.
• Tell someone: leave your route, start time and expected finish with a responsible person.

Prepare your map and compass before you need them

Fold your map so the relevant area is visible, or use a map case. Know the scale: 1:25,000 shows walls, streams and small paths; 1:50,000 is lighter but useful for mountain days. Check the map margin for magnetic declination. In the UK it is small, but know whether to add or subtract it.

Learn the parts of your compass. The baseplate has a direction-of-travel arrow. The bezel rotates and carries the orienting lines and the orienting arrow. The magnetic needle has a red end that points to magnetic north. Before you leave, check that the needle swings freely and that the bezel turns smoothly.

• Set the map: lay the compass flat on the map, align the orienting lines with the grid lines, and turn the map until the red needle sits inside the orienting arrow.
• Keep it dry: a wet map tears and a fogged compass is useless. Use a case and a lanyard.
• Know your escape routes: identify valleys, tracks and roads that lead to safety if the weather turns.

Taking a bearing you can actually follow

To take a bearing from the map, place the long edge of the baseplate from where you are to where you want to be. The direction-of-travel arrow must point towards your destination. Rotate the bezel until the orienting lines are parallel with the map's grid lines and the N on the bezel points to grid north. Read the number at the index line.

Now hold the compass flat in front of you. Turn your whole body until the red magnetic needle sits inside the orienting arrow. The direction-of-travel arrow now points along your bearing. Pick a feature in that direction—a rock, a tree, a patch of heather—and walk to it. In poor visibility, look up, choose a target, walk, then check again.

• Adjust for declination: if the map margin tells you to add or subtract degrees, do it before you walk.
• Use aiming off: aim slightly to one side of a stream or wall. When you hit it, you know which way to turn.
• Use handrails: follow a wall, fence or stream that runs in your direction of travel.
• Count paces: know your double paces per 100 metres on flat, uphill and downhill ground.

Matching features to the map when you can only see a few metres

In mist, you will not see the whole landscape. You must navigate from one small feature to the next. A bend in a path, a stream junction, a wall corner, a boulder or a contour shape can all confirm your position. Use them like stepping stones.

Contours tell you whether the ground rises, falls or stays level. If the ground climbs when the map says it should drop, stop and reassess. Check your compass, pacing and last feature.

• Attack points: aim for an obvious feature near your destination, then navigate precisely from there.
• Tick features: note each one as you pass it. This stops you drifting into wishful thinking.
• Back bearings: take a bearing back to your last known point. If it does not match, you are not where you think you are.
• Stop when unsure: eat, drink, put on a layer, get out of the wind and take ten minutes to re-plan.

Practise in the dark, in the mist and in familiar places

The best place to learn is somewhere you know well. Go out on a clear evening and take bearings between features you can see. Then try the same route at night or in low cloud. Compare what the compass says with what your eyes and map tell you. That feedback is how skill becomes instinct.

Practise in short, safe sessions. Try a local park, a quiet footpath or a familiar hill. Set a bearing for 200 metres, walk it, then take a back bearing to check you are on line. Do this until the routine feels calm rather than complicated.

• Start small: ten minutes of practice is better than a two-hour epic.
• Go with someone: two heads are better in fog, and it is safer.
• Use a headtorch: practise changing batteries and using red light to preserve night vision.
• Review afterwards: ask what went well and what you would do differently.

Carry a paper map and compass even if you use a phone. Batteries die and cold drains them. Keep them accessible, not buried at the bottom of your pack. Finally, be willing to turn around. Good navigators notice early, stay calm and make a sensible decision.