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Map Reading Basics Mountain Climbers Should Know

Updated: Feb 15, 2023

If you are thinking of heading up a mountain like Snowdon (Yr Wyddfa) without taking a map, then think again!

Map reading is the interpretation and understanding of maps. It is composed of many individual navigational skills which are used by mountaineers to travel efficiently and safely through complex and hazardous terrain.

At Walk Snowdonia, we've created this super comprehensive guide that will certainly get your navigation skills heading in the right direction. Carry on reading to learn your way around a map...

Map reading tools/ map & compass/ grid reference card/ pacing card
Map reading tools

Why is map reading important in mountaineering?

Maps are a diagrammatic representation of the real world. They contain a huge amount of information including terrain, features and hazards. Reading them allows the user to find a suitable route from A to B in an efficient, enjoyable and safe manor.

Check out our Map Reading Courses which take place in the spectacular surroundings of the Snowdonia National Park.

What map do you use to find mountains?

To navigate in the mountains you need a level of detailed information which allows route finding through complex terrain in all conditions. This level of detail is only found in the UK on topographic maps which are produced by OS (Ordnance Survey) and Harvey.

Important skills when map reading

There is a broad plethora of skills that hikers and mountaineers use to navigate. The collection of these skills is often referred to as a navigational toolbox. The more tools you have in your toolbox, the better you are at navigating. This will allow you to go into more challenging environments in more adverse conditions.

Basic map reading skills are the ability to:

Intermediate map reading skills include the ability to:

  • Apply distances on the map to the real world using timings (Naysmiths rule) and pacing

  • Take and follow a bearing

  • Aim off

  • Hand rail linear features

  • Identify and tick off features

  • Apply catching features

Advanced map reading skills include the ability to:

  • Box around obstacles

  • Apply relocation techniques (back bearings, slope aspects, resection)

  • Use dead reckoning process

  • Navigate at night

The best way to learn these practical skills is by doing them in the real environment. Consider booking onto a map reading course to learn and practice these skills.

Map Reading at night

Understanding symbols and features of a topographic map

Topographic maps provide detailed information about an area and are used in a variety of situations including engineering, environmental management and conservation, urban planning and outdoor pursuits.

The two types of topographic maps used in the UK for most outdoor activities are produced by Ordnance Survey (OS) and Harvey.

Many of the symbols and features are shown differently on different maps. For example on a OS 1:25,000 Explorer map a footpath is depicted as a green dashed line. On the 1:50,000 Landranger map, produced by the same company, the same footpath will be drawn as an orange dashed line and on the Harvey maps the same footpath will be drawn differently again. For this reason it is good to familiarise yourself with the relevant and important symbols on the map you are using.

The most useful symbols and features when hiking are:

  • Roads & paths

  • Public access and rights of way

  • Natural features (such as contour lines, cliffs, rivers etc.)

  • Vegetation (such as woodland etc.)

  • Leisure information (car parks, toilets etc.)

  • Other features (walls, sheepfolds, bridges etc.)

  • Boundaries (National Park boundary)

Most important Map Symbols for OS & Harvey maps

Common mistakes to avoid when map reading

Making mistakes is easy. Learning from them will make you a better mountaineer.

Confusing the symbols

The symbols on maps can be mixed up especially when your map reading skills are new or when you are using a map for the first time.

Represented by dashed lines on OS Maps are: paths, footpaths, bridleways, permissive footpaths, permissive bridleways, roads under construction, National Boundaries , Country Boundaries, Unitary Authority Boundaries, District Boundaries, National Park Boundaries, Electricity Transmission lines and single track standard gauge railways. This is just one example of an important symbol that can be easy mistaken.

Indistinct footpaths and sheep trails

A really common problem when in the mountains is footpaths disappearing. You can start walking on a clear, obvious and well defined footpath only to find it quickly disappears. Without the right map reading skills, it can feel like you have disappeared too.

Sometimes sheep trails are more obvious than the marked footpath and it is all too easy to inadvertently follow them instead. For this reason our Beginners Navigation Course takes place in an area with lots of indistinct footpaths and sheep trails. This gives learners the skills they need choose the correct footpath, avoid the sheep trails and to know what to do when the footpath vanishes.

Following a bearing off Glyder Fach
Where is the path? Navigating off the Glyders is difficult, even in good visibility

Compass problems

One of the most common issues with the compass for beginners is not holding the compass flat. When the compass is flat it allows the magnetic needle to 'settle' and point north. The magnet on the compass is quite weak therefore won't 'settle' and point north if it isn't flat or you don't give it enough time (a few seconds).

Beware also of a bubble inside the compass as this interferes with the needle and pushes or blocks it so it doesn't point north.

Reverse Polarity

On the summit of Carnedd Llewelyn in thick fog, I once found a pair of hikers who were really disorientated. One of their compasses said north was one way and the other compass said it was the complete opposite direction.

This is known as 'reverse polarity' and happens when a compass repolarises after it is exposed to a magnet. Phones, GPS units, pen knives, and underwire bras are all magnetic so be careful where you store your compass.

Luckily my compass was working correctly so I was able to tell them what had happened and which of their compasses was accurate.

Reading the map in the opposite direction

After you have learned the map reading basics a common mistake is to do something in the opposite way to how it should be done. This can include holding the map upside down, confusing the magnetic north - south arrow on the compass or doing back bearings.

Calculating the wrong map measurements

There are many pitfalls with distances and calculating how long it will take to travel them.

For beginners underestimating distances in the mountains is a common mistake. People apply previous experience to guestimate how long a route will take and forget that walking uphill slows you down considerably (1 min per 10m according to Naismith's rule). In addition the terrain of mountains can be much slower due to uneven footpaths, slippery rocks etc.

At an intermediate level, using the correct Romer scale on the compass for the scale of map you are using takes practice and familiarisation with the map & compass. Changing either the map or compass after familiarity has been acquired often causes difficulties.

Ignoring alarm bells on the route

The sun was yet to rise so it was dark. My friend (also a mountaineering professional) and I had just left the car park and were chatting away. After a quick check of the map, the footpath looked like the one we wanted so we set off along it and carried on chatting.

Whilst chatting I started to get the feeling that this wasn't the right path but continued with the walk and conversation.

I stopped and said to my friend, a mountaineering instructor, that this footpath didn't seem right. He agreed. After a quick check of the map we realised we were, in fact, on the wrong path.

There are a few key points here. First of all, everybody gets 'lost' from time to time especially if they aren't paying attention.

Secondly, before we set off we had made a mental picture of what to expect (tick off features). When the reality didn't match our expectations we grew suspicious that something was awry.

This brings us to the third point.

If it doesn't feel right it probably isn't!

Stop and check!

The sooner you stop, pull out the map and check, the better. You might lose a minute of your time but you will either: reassure yourself that you are on the right path or save yourself time and energy walking in the wrong direction.

Not using the map to avoid hazards

Knowing map symbols is useful but it can also save your life. The summit plateau of Ben Nevis has claimed many lives over the years as people take a compass bearing from the summit cairn down the tourist track. The problem is this leads you straight over the cliffs of the north face which are hidden beneath cornices of snow well into summer. Knowing what these cliffs look like on a map can literally save your life.

North Face of Ben Nevis

Learn the map reading basics with Walk Snowdonia

"Give a person a fish and you feed them for a day. Teach them to fish and you feed them for a lifetime." Lao Tsu

We love teaching map reading more than anything else!

Our Beginners Map Reading Course is designed specifically to get you into the mountains and on your own adventure after just one day.

We also offer Bespoke Navigation Courses for people wanting to focus on specific skills or pass mountain training qualifications.

Map Reading Course in Snowdonia
Walk Snowdonia Navigation Course


What are contour lines?

Contour lines are symbols (squiggly lines) on a map that indicate height above sea level. This is why some of them have numbers which tells us the height of the land along which the line is drawn along in meters.

They are useful as they allow us to plot the 3D 'real world' onto a 2D paper map. Without contour lines we would have to take 3D models of the terrain with us instead of a 2D map.

Contour lines are useful as they tell us the height and shape of the terrain. They give us valuable information about the steepness of slopes.

Contour lines which are close together are steep slopes and far apart are gentle slopes.

A huge advantage of contour lines compared to almost all other features and symbols on a map is that they don't change. Rivers change course, lakes appear and disappear and buildings are built and crumble away. Contour lines have changed little if at all since the end of last ice ace. If you drew a topographic map of the British mountains 10 thousand years ago the contour lines would look the same as one drawn today.

Contour lines are really useful in zero visibility. You don't even need to open your eyes to know if you are walking uphill, downhill or on flat terrain. If you have a compass, you can tell the direction of a slope too. The steepness and direction of a slope gives you really valuable information about your location.

The problem with contour lines is that they are difficult to learn to read and take time to understand.

Infographic explaining how contour lines work

Does GPS work in the mountains?

GPS (Global Positioning System) has become part of everyday life, can be found in many devices and is used by many apps. It can be helpful in finding good local restaurants and your way around an unfamiliar city.

GPS units including smartphones are really useful in the mountains as they can tell us live location, the route taken and are a great tool for confirming location (especially on featureless terrain), relocation, reassurance and timesaving.

They are a helpful tool for anyone navigating in the mountains in the 21st century but they shouldn't be used as the only and primary tool of navigation. They should be used in conjunction with other navigation tools such as maps and compass skills because of their problems and limitations.

GPS satellites work by transmitting a unique signal which GPS devices decode to tell them the exact location of the satellite. The GPS device uses this information and trilateration to calculate the users exact location. Therefore, the more satellites the GPS unit is in contact with the more accurate it is.

GPS units (mobile phones in particular) can be dangerously inaccurate because of a lack of satellites, sub optimal satellite geometry, reflected signals (eg. off cliffs) and blocking. My GPS unit is mostly accurate but frequently 'out', sometimes by hundreds of metres. If you are trying to avoid a cliff, then this could, and has, cost lives.

GPS units (especially mobile phones) are also limited by their battery life which depletes faster than normal due to the cold and constantly searching for a signal.

In addition, GPS and phones are prone to damage from dropping, crushing or water damage.

GPS Unit

Which is the best map for hiking?

The topographic maps which provide the information you need for hiking in the UK are produced by OS and Harvey.

OS Maps

The OS maps used by hikers are OS Explorer and OS Landranger maps.

OS Explorer (orange cover) maps are more popular for hikers as they are produced at a scale of 1:25k.

The OS Landranger (pink cover) maps are at a scale of 1:50k.

Harvey Maps

Harvey maps are usually drawn at the 1:25k scale or 1:40k scale. Harvey also produce useful National Trail maps such as 'The Coast to Coast'.

What are map scales?

Maps are a diagrammatic representation of the real world.

It would be impractical to carry a full size map with you but if you did it would be at a scale of 1:1. That means that a 100m wall would be represented by a line on a map that is 100m long (that would be a big map).

Because of the impracticalities of this Cartographers (map makers) essentially zoom out and shrink the map by what is called a 'scale' so the map can fit in your pocket.

On a 1:25,000 map, 1 cm on the map is equivalent to 25,000 cm in real life. It is a bit like zooming out 25,000 times. On a map with a scale of 1:50,000, 1 cm on the map is equivalent to 50,000 cm in real life.

Area covered by two different map scales

Which is the best map scale?

Maps which are more zoomed in like a map at 1:25,000 have more detail so are especially useful if you intend to go off a marked footpath.

Maps which are more zoomed out, such as maps at a 1:40,000 or 1:50,000 scale, are often detailed enough for hiking. They are especially useful for longer journey's or winter conditions when much of the detail of a 1:25,000 map is buried under the snow.

Are OS Maps or Harvey Maps better?

OS Maps and Harvey maps both have their advantages and disadvantages and it often comes down to personal preference.

OS Leisure maps are designed for all sorts of leisure activities which includes hiking. Therefore they contain a huge amount of information, much of it not relevant for mountaineers.

For novice map readers all of this information can be [very] confusing and even for the seasoned professional this information is often irrelevant. For example, knowing where the civil parish boundary lies or whether a pit is filled with sand or gravel hasn't been of use to me yet but this level of information is included on OS Leisure Maps.

Harvey maps are designed specifically for hikers. As a consequence they only contain relevant information needed for hiking.

All Harvey maps are waterproof and weigh less than OS maps. Most of the clients on our navigation courses find Harvey Maps easier to use.

However, the 1:40k scale used on some Harvey maps aren't on some Compass Romas which makes it difficult to measure distances.

The contour lines on Harvey maps represent 15m of elevation and are more difficult (for me personally) to work with than OS contour lines which represent 10m of elevation. It is easier to apply Naysmiths Rule to OS maps as you add 1 minute per 10m of ascent which is easy when the contour lines are drawn 10m apart.

In spite of this, people using a map for the first time usually find the contour lines on a Harvey map easier to interpret as they are visually easier to understand. This is because there are less contour lines and they are coloured grey for rocky ground and cliffs & crags are clearly marked.

Ground more than 600m high is shaded grey on the Harvey 1:40k maps which makes identifying mountains and high ground at a glance easy.

What's the difference between True north, Grid North and magnetic north?

True North is the line from your location to the North Pole.

Grid North are the parallel lines drawn on a map which point towards north (blue on an OS map and grey on Harvey maps). One of these lines on a map is the same as True North (the line at longitude 2 degrees west of the zero Greenwich Meridian line) whereas the rest are slightly out. This is because map makers are trying to depict the 3D shape of our earth on a 2D paper map.

Magnetic North is what your compass needle points to. The position of this moves continually due to natural changes in the Earth’s magnetic field.

Correcting for magnetic variation is not currently worth worrying about for most navigation situations in the UK because the three 'Norths' are so similar or exactly the same.

Interestingly the 'triple alignment' of all three 'Norths' converged over the UK occurred for the first time in map making history in 2022. This rare phenomena is predicted to continue until July 2026.


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