You’ve found an OS map at the back of the drawer. It’s a few years old, maybe more. The question is whether you can still trust it.
It’s one of those things most walkers never think to check. And the answer isn’t quite as straightforward as you might hope.
The short answer: there is no fixed update cycle, and for most walking an old map is fine. Ordnance Survey revise their mapping continually rather than on a schedule, and some areas change far more often than others. The scale, the grid and the contours never go out of date. What ages is the detail, mainly paths, roads and buildings, plus one figure in the margin you should never trust on an old sheet.
How often Ordnance Survey maps are updated depends on what part of the map you’re looking at, and some things change a lot more regularly than others. Here’s what you actually need to know before you head out with that old map.
An out-of-date map is only really a problem if you are not confident using it, and the basics of map and compass work on the hill covers the rest.
How Ordnance Survey Actually Updates Its Maps
Ordnance Survey’s mapping data is now fully digital and updated regularly, mostly in urban areas. Rather than waiting to reprint an entire map and update everything at once, they continuously collect new survey data and feed it into their national database.
That database is updated all the time. New roads, buildings, field boundaries, and footpaths are added as they’re surveyed.
What This Means for Printed Maps
The catch is that a printed map is a snapshot of that database at a fixed point in time.
When OS prints a new edition of an Explorer or Landranger map, they pull from the most current data available at that moment. Between print runs, the database keeps changing, but your map doesn’t.
So there are effectively two layers. The live database, which is always being updated. And the printed map in your hands, which was accurate on the day it was printed and has been slowly diverging from reality ever since.
How Often Does a New Edition Get Printed?
There’s no fixed schedule. Popular maps in high-walking areas tend to get updated more frequently than maps of less-visited regions.
In practice, most OS Explorer maps are revised every few years, though some editions stretch longer. The only reliable way to know how current your map is to check the edition date inside the cover.
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What Gets Updated and What Doesn’t
This is the bit that actually matters for walkers. Not everything on a map changes at the same rate.
What Changes Over Time
Public rights of way are the thing most likely to have shifted since your map was printed. New footpaths get added. Existing paths occasionally get diverted around new developments or land changes. If you’re walking a route in an area with a lot of recent development, it’s worth checking.
Roads and tracks change too, especially in areas with new housing or industrial development. If you’re navigating by road intersections near settlements, an old map can occasionally mislead you.
Woodland areas and field boundaries can shift as well, though less dramatically.
| Goes out of date | Never goes out of date |
|---|---|
| Public rights of way, diversions and new paths | The National Grid and grid references |
| Roads, tracks and new housing | Contour lines and the shape of the ground |
| Forestry and woodland cover | The scale, and everything you measure with it |
| Field boundaries, walls and fences | Rivers, lakes and the coastline, near enough |
| Buildings, car parks and access points | Summits, crags and the landforms themselves |
| The grid magnetic angle in the margin | The map symbols and what they mean |
What Stays the Same
Here’s the good news, and it’s important.
Contour lines don’t change. The shape of the land, the hills, the valleys, the ridges, doesn’t move as your map ages. A hill is still a hill. If you want a refresher on reading them, our guide to how to read contour lines breaks it down.
The grid system doesn’t change. In the UK, your grid references work exactly the same on an older map as on a brand new one. Nor does the scale: the 1:25,000 and 1:50,000 ratios mean precisely what they always did, so your distance and timing calculations are unaffected by map age.
Major landmarks like rivers, lakes, and established settlements are stable. Your compass bearings to hilltops, trig points, and natural features aren’t going to be wrong because of map age.
The short version. For open moorland and hill navigation, map age matters very little for most things. For route-finding on footpaths through farmland and settlements, it matters more.
How to Check If Your Map Is Up to Date
Turn your map over or open the cover. You’re looking for the edition date or revision information, usually printed in small text near the legend.
OS typically prints something like “This edition published 2019” or lists a revision date. That tells you the snapshot your map represents.
A few things to weigh up when deciding whether to buy a new one:
- How old is it? A map from the last five years is almost certainly fine for most hill walking. One from 15 to 20 years ago might have footpath changes worth checking.
- Where are you walking? Remote moorland and mountain terrain, age doesn’t matter much. Lowland farmland, areas of development, or the urban fringe, worth cross-referencing with a current digital map before you go.
- Are you relying on a specific path? If your route depends on a particular right of way through fields or private land, a quick check on the OS Maps app confirms whether the path still runs as shown.
When It’s Worth Buying a New Map
If your map is showing genuine signs of age, places you know that aren’t on it or obvious development that isn’t shown, it’s probably time for a new one. OS Explorer maps are usually around £11, a little more for the waterproof Active version.
If you’re planning a serious walk and in any doubt, the OS Maps app subscription gives you access to the most current data on your phone as a digital backup. Keep your paper map as the primary. Use digital to fill any gaps.
That switch matters more than it used to, because UK magnetic variation is in the middle of crossing from west to east. There is more on it in how to use a compass on a map, including why the old “grid to mag, add” rule is no longer safe to teach.
Does It Actually Matter for Navigation?
For most walkers doing most walks, the honest answer is that it matters less than you might think.
The fundamental navigation skills, reading contours and using the grid system, work identically on an old map as a new one. The terrain doesn’t move.
Where it genuinely matters is footpaths in agricultural land, where diversions and new routes can appear, and urban-edge walking, where development changes the landscape faster than print cycles can keep up.
The One Exception: Magnetic Declination
There’s one thing on an older map that absolutely cannot be trusted for compass work. The magnetic north figure printed in the margin.
On a UK map that figure is the grid magnetic angle, the difference between grid north on your map and magnetic north on your compass needle. The magnetic pole shifts constantly, so the figure was accurate when the map was surveyed and drifts from then on. Ordnance Survey say so themselves: the angle given on each map “is correct only at the time of printing”. On a map that’s 10 or 20 years old, that number will be noticeably wrong. Use it to set a bearing and you could end up significantly off course.
The fix takes about 30 seconds. Before any walk involving compass work, look up the current figure for where you’re walking rather than reading it off the map margin. The British Geological Survey hosts the calculator for this, its Grid Magnetic Angle Calculator, which takes a postcode or a grid reference. Ordnance Survey point walkers to that same tool rather than running one of their own.
Get the current figure, apply it, and your old map is as reliable as a brand new one for compass navigation.
If you are working out which sheet you need in the first place, OS map numbers will find it, and how to read a map scale covers the part of the map that never goes out of date at all.
How often are OS maps updated?
There is no fixed cycle. Ordnance Survey revise their mapping continually rather than on a schedule, adding changes to a national database as they are surveyed. Some areas change far more often than others. A printed sheet is a snapshot of that database on the day it went to press, so how current your map is depends on the edition you own rather than on any published timetable.
Is my old OS map still safe to use?
For most walking, yes. The grid, the contours, the scale and the landforms do not change, and those are what you actually navigate by. What ages is the detail: paths, roads, forestry and buildings. If your route depends on a specific footpath or a specific access point, check it against current mapping before you go.
What is the one thing on an old map you cannot trust?
The grid magnetic angle printed in the margin. Ordnance Survey say themselves that the figure is correct only at the time of printing, and magnetic north keeps moving. On a map ten or twenty years old that number will be noticeably wrong. Look up the current figure for your location instead of reading it off the sheet.
Are digital OS maps more up to date than paper ones?
Usually, but not by as much as people assume, and neither is live. The app is redrawn from the same national database, so it reflects changes sooner than a printed sheet can. It still is not updated the day a forestry block comes down. Both are a snapshot. A digital one is just a more recent snapshot.
How do I find out how old my OS map is?
Look for the edition or revision date, usually printed on the cover or in the margin alongside the copyright line. That tells you when the sheet was published, which is the date the mapping was frozen at. It is a more useful number than the copyright year on its own.
When is it actually worth buying a new OS map?
When the ground you walk has genuinely changed, when your copy is falling apart, or when you are going somewhere unfamiliar and want the current detail rather than a best guess. Buying a new sheet every few years for an area you know well is rarely money well spent.
