Opening up a new Ordnance Survey (OS) map can feel like you’re looking at a secret code. It’s a beautiful, confusing jumble of squiggly lines, strange symbols, and a grid of blue numbers.
But I promise you, it’s a code that is incredibly easy to crack.
This map is your key to unlocking the British countryside. It’s the single most powerful tool you can carry, and learning to read it is the most rewarding skill a hiker can master.
It’s the difference between following a route and understanding a landscape.
In our Beginner’s Guide to Hiking Navigation, we explained why a map and compass are your ultimate, reliable backup. Now, let’s show you how to use one. We’ll skip the complex theory and focus on the practical skills you’ll use on every single walk.
Part 1: Which Map Do I Need? Explorer vs. Landranger
The first thing you’ll notice in any shop is two different types of OS map: one with an orange cover and one with a pink cover.
- Explorer (Orange): This is the walker’s map. It’s a 1:25,000 scale, which means every 4cm on the map represents 1km on the ground. It is incredibly detailed—it shows field boundaries, types of woodland, and most importantly, every single public right of way. This is the one you want.
- Landranger (Pink): This is a 1:50,000 scale (2cm = 1km). It covers a larger area but has far less detail. It’s great for long-distance cycling or planning a road trip, but it doesn’t show all the footpaths you’ll need for hiking.
The Golden Rule: For hiking, always buy the orange Explorer map for the area you’re visiting.
Part 2: The Legend (How to Read Map Symbols)
The legend is your map’s dictionary. It’s usually found in a panel at the side or bottom. You don’t need to memorise it, but you do need to know where to find the most important symbols for a walker.
The Most Important Symbol: Public Rights of Way
These are the magic green lines that show you where you are legally allowed to walk.
- Green Dashed Line: Public Footpath (for walkers only).
- Longer Green Dashed Lines: Public Bridleway (for walkers, horse riders, and cyclists).
- Green ‘Plus’ Line (++): Byway Open to All Traffic.
Any other path or track, shown as a black dashed line, is not a public right of way. It might be a permissive path, or it might be private. Sticking to the green lines is the best way to avoid getting lost or trespassing.
Other Key Symbols to Know:
- Roads: From the thick red ‘A’ roads to the thin yellow ‘C’ roads.
- Landmarks: White P in a Blue Sqaure (Parking), Blue Tankard Glass (Inn), a cross (Church), a triangle (Trig Point).
- Terrain: Coniferous (pointy) trees for dark forests, Non Coniferous (round) trees for deciduous woodland. Blue lines for streams and rivers.
Eg, here is a trig point blue triangle. The flower pattern around it means Prominent Viewpoint.
Part 3: The Secret Code – How to Read Contour Lines
This is the most important skill you will learn. The squiggly brown lines all over your map are contour lines. Each line joins points of equal height above sea level.
They turn a 2D piece of paper into a 3D landscape in your mind.
The Two Golden Rules of Contours:
- If the lines are VERY CLOSE together, the ground is STEEP.
- If the lines are FAR APART, the ground is GENTLE or FLAT.
That’s it. You can now look at a route and see exactly where the big climbs are.
Here is the famous part of the Yorkshire 3 Peaks as you approach Ingleborough. A relatively steady climb before a sharp steep section on the left before the summit. This is the lay of the land.
And here is how it looks on the map where you can see the contour lines get a lot closer together.
How to Spot Hills and Valleys:
- Spotting a Hill: Look for circles or ovals of contour lines getting smaller and smaller. The smallest circle at the top is the summit.
- Spotting a Valley: Look for a V-shape in the contour lines. The ‘V’ will always point uphill, towards the source of the stream that (even if it’s dry) carved it out.
- Spotting a Ridge: This is the opposite of a valley. It’s a long, U- or V-shape in the contours pointing downhill.
So here is a good hill example. Great Mell Fell in the Lake District. You can see how the countours circle close together around the hill slopes and a small circle at the top.
And here is a classic example of how a valley looks.
This is the glorious perefectly shaped High Cup Nick. You can clearly see the V shape of the contour lines as the valley narrows to the top:
Part 4: The Blue Lines – How to Use Grid References
The blue lines that form a grid across your map are part of the Ordnance Survey National Grid. They let you pinpoint your exact location. The numbers for these lines are in the margin.
The rule for finding a location is simple: “Along the corridor, then up the stairs.”
Find the 4-Figure Reference (Finds a Square):
- Find the two-digit number for the vertical line to the left of your square (along the corridor).
- Find the two-digit number for the horizontal line at the bottom of your square (up the stairs).
- Put them together. If your “corridor” number is 45 and your “stairs” number is 15, your 4-figure grid reference is 45 15. This is great for telling someone the general area you’re in.
Example: You want to tell somebody the 4 digit grid reference for Horton-in-Ribblesdale Train Station. A train station is a red circle with black outline.
Along the corridor = 80 (the line that is to the left of the station)
Up the stairs = 72 (the line that is underneath)
The 4 digit grid reference is 8072
But what if you want to be more precise? A spot within the square?
Find the 6-Figure Reference (Finds a Point):
- This is just a more detailed version. Imagine the square (45 15) is divided into a 10×10 grid.
- First, go “along the corridor” to line 45. Then, estimate how many tenths you need to go across to your point. Let’s say it’s 3 tenths. Your first number is 453.
- Next, go “up the stairs” to line 15. Then, estimate how many tenths you need to go up to your point. Let’s say it’s 8 tenths. Your second number is 158.
- Your 6-figure grid reference is 453 158. This is what you would give to emergency services.
Example: You want to tell someone exactly where you are. You know you are stood by Lumley Moor Reservoir, but giving them a simple 4 digit reference could mean you are anywhere around it. So you want to tell them you are situated on the path next to the reservoir, right above the second ‘o’ of the word moor on this map.
So. Along the corridor 22. Plus 2 tenths of the square in.
Up the stairs 70. Plus 6 tenths of the square up.
The 6 digit reference is 222706.
Part 5: Your First Practical Skill – Orienting Your Map
This is the simplest and most useful thing you can do on a walk. “Orienting the map” means aligning it with the landscape in front of you, so what’s left on the map is left in real life.
All you need is your compass.
- Place your compass flat on your map.
- Find the North-South (blue) grid lines on your map. Rotate your compass bezel (the dial) so that the ‘N’ for North on the dial is pointing to the top of the map.
- Align the “orienting lines” inside the compass housing so they are parallel with the blue grid lines on the map.
- Now, holding the map and compass steady together, turn your whole body…
- …until the red end of the magnetic needle is “boxed” perfectly inside the orienting arrow on your compass.
Stop. You’re done.
Your map is now perfectly aligned with the world around you. The path heading left on your map is the path heading left in front of you. The hill you see to your right is the hill shown to the right on your map.
Conclusion: Practice Makes Perfect
You now know the four essential building blocks of map reading:
- Which map to buy (Explorer).
- How to read symbols (The Legend).
- How to see hills (Contours).
- How to orient your map (Compass).
Like any new skill, this takes practice. The best way to learn is to do it. On your next walk (even one you know well), take out your map and orient it. Look at the contour lines and match them to the hills you can see. Find the symbols for the pub or car park.
This skill is your key to a lifetime of adventure, and the foundation for safely exploring all the routes we share here on BaldHiker.
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