By: Blonde Two
Learn to read a map and enjoy the outdoors safely on our Two Blondes navigation courses
Map scales can be a bit confusing when you first start using them but once you have tried to do micro navigation using a 1:50,000 map or attempted to follow a 1:25,000 one whilst travelling by car, you start to realise that there is a point to learning the differences. We explain the two most popular Ordnance Survey map scales for you (hopefully without having to do too much maths).
Ordnance Survey 1:25,000 Scale Maps (other maps really aren’t available)
Name: Explorer (Sexy Exy)
Maths (sorry): A 1:25,000 scale means that each millimetre on your map represents 25,000 mm or 25 metres on the ground (therefore 4mm on your 1:25,000 map will represent 100 metres and 4 cm will represent 1 km).
Grid Squares: 1 blue grid square (4cm) represents 1 kilometre, which takes 15 minutes to walk and almost no time to drive.
Amount of Detail: A 1:25,000 map will give you enough detail to do walking, running and off-road cycling plus micro and night navigation.
Area Covered: A 1:25,000 map will cover a smaller area than a 1:50,000 map. This means that if you are doing a long walk, run or cycle you might need 2 or even 3 maps. This is when a mapping app like OS Maps, which allows you to plot and print just your planned route, can come in useful.
Example: Here is a square kilometre at a 1:25,000 scale of our favourite areas of Dartmoor for teaching navigation. Note the man made workings that are shown around Crazy Well Pool, the details in the wall system and the contour details around Kink in Leat (not yet an official title).
Copyright Ordnance Survey 2017
Ordnance Survey 1:50,000 maps
Name: Landranger (Larry to his friends)
Maths (still sorry): A 1:50,000 scale means that each millimetre on your map represents 50,000 millimetres or 50 metres on the ground. (Therefore 2 mm on the map represents 100 metres and 2 cm a kilometre).
Grid Squares (this bit is like magic): 1 blue grid square (this time 2cm) represents 1 kilometre, which takes 15 minutes to walk and almost no time to drive.
Amount of Detail: You can use a 1:50,000 map for walking but it will only show larger features such as roads and large paths. We wouldn’t recommend this map scale for any walk that requires accurate navigation (which, to our minds, is all of them). 1:50,000 maps are great for an overview of an area or for road cycling.
Area Covered: The reason some people prefer 1:50,000 maps is because they cover a bigger area and allow you to see the whole picture of the landscape around you. They are also far easier to follow in the car although for longer car journeys Ordnance Survey also produce 1:250,000 scale maps such as these lovely maps of Scotland.
Example: Here is a square kilometre at a 1:50,000 scale of the same area of Dartmoor. You can see that this map wouldn’t be much good for teaching navigation. The man made workings around Crazy Well Pool are not defined (although the contour lines give some indication), the wall system is not shown at all and the contour details around Kink in Leat are almost invisible.
Copyright Ordnance Survey 2017
We hope that this has helped you to understand map scales a bit better. If you don’t trust our maths (and this might be wise) feel free to have a look at this even simpler explanation of map scales from Ordnance Survey themselves. You might also enjoy looking at Steve Backshall on video (he is saying some sensible things about maps but you can just look at him if you prefer!)
Or… if you prefer Blondes… here’s B2 teaching navigation skills in Epping Forest as part of the Ordnance Survey Street2Peak project.
Two Blondes Walking offer a range of walking and wild camping workshops throughout the year. Take a look at our courses page below and get in touch if you have any questions.