Two skills that belong together

A grid reference is an address. It tells you, to the nearest hundred metres or better, exactly which patch of hillside you are standing on. A landmark is a witness. It confirms that the patch you have calculated really is the one beneath your boots. Use only the grid reference and you can be precise but wrong — a misread easting can put you a kilometre up the wrong glen. Use only landmarks and you can be confident but vague, especially in mist when every peat hag looks the same.

Put the two together and navigation becomes a conversation between map and ground. The reference gives you a claim; the landmark gives you the evidence. In clear weather that is a pleasant habit. In driving cloud on a Cairngorm plateau or a wet afternoon on the Pennine tops, it is the difference between a good day out and a call to mountain rescue.

Reading the National Grid on a British map

Ordnance Survey maps are covered by the National Grid, a mesh of squares one kilometre across. Each square has a two-letter prefix, then numbers. Read eastings before northings — along the corridor, then up the stairs. A four-figure reference such as 6421 identifies a whole kilometre square, which is far too coarse for navigation. A six-figure reference, say 642 218, narrows it to a 100-metre square, and that is the standard you should be aiming for while walking.

• On a 1:25,000 Explorer map, one grid square measures 4 cm on paper.
• On a 1:50,000 Landranger, the same kilometre is just 2 cm.
• Estimate tenths of a square by eye, then check with the roamer scale on your compass baseplate.
• Always quote eastings first, then northings, with a clear gap between the two halves.

It is worth practising until you can give a six-figure reference in a few seconds. If you have to ring for help, a crisp, correct reference is the single most useful thing you can say.

Fixing your position where you stand

The map only helps if you know where you are on it. Start with the obvious: are you on a path, a ridge, a stream junction, a wall corner? These are the features that survive mist. If nothing obvious presents itself, take a bearing to two identifiable points — a summit cairn, a trig pillar, a distinctive crag — and convert those bearings into back bearings drawn on the map. Where the two lines cross is your position. A third line gives you a check, and if the triangle is large, your identification of a feature is wrong.

You can also use distance. Pace out a known leg, or time it against your own walking speed. Most hillwalkers manage roughly 4 km per hour on the flat, less uphill, and a good deal less in deep heather or bog. Calibrate your own pace on familiar ground so that the numbers mean something real.

Landmarks you can trust

Not every feature deserves your confidence. Good landmarks are fixed, distinctive and marked on the map. Poor ones are vague, repeated across the landscape, or move.

• Reliable: trig pillars, summit cairns, boundary stones, ladder stiles, footbridges, lochans, stream confluences, wall and fence corners, large crags.
• Unreliable: lone boulders, stock gates in open country, sheep tracks, boggy path junctions, and any feature that appears half a dozen times on the same hillside.

Contours are landmarks too. A distinctive spur, a steepening of the slope, or the point where the ground begins to fall away in a particular direction can confirm a grid reference as surely as a cairn. Learn to read the shape of the land as a feature in its own right.

Combining both in poor visibility

When the cloud comes down, break the journey into short legs. For each leg, note the grid reference you are leaving, the bearing you will walk, the distance, and the grid reference you expect to reach. Identify one or two landmarks that should appear on the way — a stream crossing, a fence line, a change in slope — and treat them as collecting features. If you meet them in the right order, your navigation is working. If one is missing, stop and re-fix before pressing on.

Two techniques pair beautifully with grid references. Aiming off means deliberately walking a few degrees to one side of your target so that when you hit a linear feature — a wall, a stream, a path — you know which way to turn. A handrail is that same linear feature used as a guide along your route. Both reduce the accuracy you need from a single bearing, and both are easy to record as grid references on the map margin.

At every pause, ask two questions. What reference am I at? What landmark confirms it? If you cannot answer both, you are guessing.

Making it second nature

Practise in fair weather so the skills are already fluent when the weather turns. On a clear day, stop at random and give a six-figure reference, then check it against a landmark you can see. Time your legs and note your pace over rough ground. Draw your intended route as a series of references before you set off, and mark the landmarks that will confirm each one.

Do this often enough and the two habits fuse. You will glance at the map, name a grid square, look up at the ridge, and know — without drama — that you are exactly where you think you are. That quiet certainty is what makes a long day on the hills such a pleasure, whatever the cloud is doing.