A Beginner's Guide to Reading Ordnance Survey Maps

By Packing a Day Rucksack for British Weather
Comments 35
29 Aug 2026

A Beginner's Guide to Reading Ordnance Survey Maps

The Legend Is Your First Friend

Every Ordnance Survey map carries its own instruction manual in the margin. Before you leave the car park, spend five minutes with the legend. On the 1:25,000 Explorer series, the detail is generous: field boundaries, gates, stiles, streams, and every public right of way. The 1:50,000 Landranger series covers more ground but hides smaller paths. For hillwalking and rambling, start with Explorer if you can.

Notice the colours. Green dashes mark public footpaths. Orange dashes mark bridleways, where you may meet horses and cyclists. Green crosses show byways open to all traffic. Black dashed lines are often other paths, not necessarily public rights of way. Access land is usually washed in a pale orange tint. These symbols are not decoration; they tell you where you may legally walk and where the ground may be muddy, steep, or fenced.

Grid References: A Language Worth Learning

Grid references pin a point on the map with a string of numbers. Always read eastings first, then northings — along the corridor, up the stairs. A four-figure reference, such as 2345, gives a one-kilometre square. A six-figure reference, such as 234456, narrows it to 100 metres. An eight-figure reference, 23454567, is accurate to 10 metres and is what mountain rescue would like in an emergency.

To estimate the third and sixth digits, imagine the kilometre square divided into ten equal strips both ways. If your point sits six-tenths across and four-tenths up, the digits are 6 and 4. Practise at home with a known hill, a favourite bothy, or a car park. On the hill, a six-figure reference is usually plenty for a path junction. Write it down or tell someone. It turns “somewhere on the ridge” into a precise conversation.

Contours: Seeing the Shape of the Land

Contour lines join points of equal height. On most Explorer maps they are spaced at 5 or 10 metres of ascent. Read them like a story. Lines packed tightly together mean steep ground — possibly crags. Widely spaced lines mean gentle slopes or flat valley floors. A ring contour with a spot height marks a summit. Hachured lines show cliffs or rocky edges.

Look for the shape of the letter V. Where a contour crosses a valley, the V points uphill, following the stream. Where it crosses a spur or ridge, the V points downhill, away from the high ground. That single rule helps you tell a re-entrant from a shoulder even in mist. Count the contours between your start and your target to estimate total climb. A 200-metre ascent over two kilometres is a steady pull; the same ascent over 500 metres is a lung-buster.

Rights of Way and Access Land

Public footpaths are legal lines, but the physical path may be faint, overgrown, or diverted around a bog. A green dashed line on the map does not guarantee a gravel motorway. Look for supporting evidence: a stile, a gate, a waymark, a worn trod, a break in a wall. If the path vanishes, use the map’s boundaries and contours to relocate it. Walk on the line if you can, but do not trample crops or disturb livestock.

Access land, shown by the orange tint, gives you more freedom to roam away from paths, but it comes with responsibilities. Keep to the Countryside Code: close gates, take litter home, keep dogs under control near livestock, and avoid ground-nesting birds in spring. Bridleways are for walkers, horse riders, and cyclists. Byways may carry vehicles. Knowing which symbol you are following keeps you on the right side of both the law and the landowner.

From Map to Hillside: A Simple Routine

Start by setting the map with a compass so that north on the map points to north on the ground. Then thumb the map: fold it small, keep your thumb on your current position, and turn it as you walk. This tiny habit saves constant refolding and keeps you oriented. Pick two or three features ahead — a stream junction, a wall corner, a ring contour — and tick them off as you pass.

For timing, use a simple rule: allow 4 kilometres per hour on easy ground, plus one minute for every 10 metres of ascent. Add extra for stiles, gates, bog, and photo stops. If the mist comes down, use handrails: follow a wall, fence, or stream to a known point. Aim off deliberately to one side of your target so you know which way to turn when you hit a catching feature. And always carry a paper map and compass, even if you also use a device. Batteries die; contour lines do not.

Navigation

Understanding Access Rights in England and Wales

Always leave no trace, avoid fragile habitats, and follow local access rules when sleeping quietly on remote hills.

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5 Comments

Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply
- John Abraham says Jul 21, 2024 at 10:00am
  
  I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
  Reply
  - Robert Sonnysays Jul 21, 2024 at 10:00am
    
    I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
    Reply
Robert Sonny says Jul 21, 2024 at 10:00am

I must explain to you how all this mistaken idea of denouncing pleasure and praising pain was born and I will give you a complete account of the system
Reply

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