Introduction to maps 1.1: Scales

Updated: May 18



This is the first in a series of articles on navigation from At The Edge Mountaineering. Over the next few weeks, we will explore different elements of navigation from starting out, to more advanced techniques that will set you up for a leadership walking award.


These will be short articles giving you basic knowledge at home. For more detail and to practice the theory, book onto on of my Navigation courses.



First in this series: Introduction to Maps Part 1: Scales


Understanding maps and scales can be difficult to master to begin with but is very important when it comes to planning walks and navigating in the hills and mountains. A map with too much detail can make it difficult to read and distracts you from the important information. Too little detail and it becomes just as difficult to navigate with due to not having enough information to figure out where you are!


So how do I know which map to choose? Firstly, lets look at what maps are available to us.


A map is a bird's eye view of an area, depicting the land in 2D to allow the user to navigate in any conditions. In the UK, the two main map producers are Ordnance Survey and Harvey Maps.


Ordnance survey, or OS, produce maps for the entire UK in two main scales: 1:25,000 and 1:50,000. (More on scales later) They use a contour interval of 5m or 10m.


Harvey Maps produce maps for select areas of the UK specifically for hill walkers. These mainly focus on the popular hill and mountain areas with more areas being added regularly. The main map scales for Harvey's Maps are 1:25,000 and 1:40,000. They use a contour interval of 10m or 15m.



Map Scales:


Like with a scale model, maps are scaled so that a measurement on the map equals an actual measurement on the ground, but scaled up. For example, on a 1:25,000 scaled map, 1cm measured on a map using a ruler equals 25,000cm (250m) on the ground.


From Left to Right:

  1. OS map 1:25,000 scale (1cm = 25,000cm (250m) / 1mm = 25m / 4cm = 1km)

  2. OS map 1:50,000 scale (1cm = 50,000cm (500m) / 1mm = 50m / 2cm = 1km)

  3. Harvey map 1:25,000 scale (As with OS scale)

  4. Harvey map 1:40,000 scale (1cm = 40,000cm (400m) / 1mm = 40m / 2.5cm = 1km)


Notice the level of detail compared to the map scale. The larger the scale (1:25,000) the more detail is shown. The smaller the scale (1:50,000) the less detail is shown but more of an area is shown.


Imagine you are hovering only 100m above the ground and looking straight down. You will see far more detail and a smaller area than if you were, say, 500m above the ground. This is how map scales work, in a nutshell.


The level of detail shown on OS and Harvey maps is very similar. However, there are a few major differences and several subtle ones too, which we will cover later in this article.

Choosing a map:


Deciding on which map to choose depends on what you are doing in the hills and mountains. Above is a selection of the most popular types of maps used in the hills and mountains:

(Top: Left - Right)

OS Landranger Map 1:50,000

OS Explorer Map 1:25,000

OS Explorer Active Map (Laminated) 1:25,000


(Bottom: Left - Right)

Harvey Superwalker Map (XT25) 1:25,000

Harvey British Mountain Map 1:40,000


OS 1:25,000 scale maps offer the most detail and cater for a wide variety of activities in the hills and mountains. They are great for micro and night navigation, and for navigating in featureless terrain due to the greater level of contour information (10m intervals).


However, with lots of detail, this sometimes clutters the map and takes away the focus on the smaller contour features.


OS 1:50,000 scale maps takes away a lot of the details and focuses mainly on the larger contour features and other major features seen on the ground. This scale is perfect for winter navigation when snow can cover the smaller features such as footpaths, smaller contour features and rocky ground.


Harvey British Mountain Maps 1:40,000 scale is tailored more towards climbers and mountaineers who will not necessarily need to navigate to small features. They show enough detail and contour info but have de-cluttered the map by removing rocky details, for example, that are not necessary for navigation. Another example is that the contours are grey on rocky ground and crags are clearly marked. The major climbing crags are marked in red to help climbers and mountaineers find their climb.


However, the 15m contour interval does take away some of the finer detail and makes navigation across featureless terrain more difficult.


Take a look at the three examples below to see how the different map scales show more or less detail. Notice the difference in detail from Cosdon Hill/Beacon to Belstone Tor.

When deciding on a map, have a think about what your intended use is. This may sound silly, "it's obviously to navigate with", I hear you cry, however have a look at a few examples below:


  • Featureless terrain/Winter navigation: 1:50,000

  • Night navigation or micro navigation: 1:25,000

  • Long distance walk/expedition: 1:40,000 / 1:50,000

  • Complex ground: 1:25,000


I will note here though, that it is worth taking two maps with you when ever you are out in the hills and mountains and this generally involves taking two different scales of map of the same area. This gives you the option to change between scales when appropriate and also gives you a spare map in case one gets lost to the elements!


For example, if I am doing a multi-day walk and wild camp in the Lake District, I would take a 1:50,000 OS map or 1:40,000 Harvey map as it covers the entire area I will be covering (so I won't need multiple maps) and then a 1:25,000 map covering the area I will be wild camping in as this will show a greater level of detail as I may be required to navigate that area in darkness/poor visibility and the greater level of detail will help me to find my camp site.


Harvey Maps differ to OS maps in many ways and one of these ways is on their 1:40,000 British Mountain Maps. Not only does their scale sit between the 1:25,000 and 1:50,000 but they also include contour colouring at differing altitudes to help visualise the major landforms and also the inclusion of larger scale areas on the reverse of their maps for the most popular peak or peaks.


The image above shows Ben Nevis enlarged to 1:15,000 offering more detail to help navigation.


The Lake District Harvey British Mountain Map includes a 1:20,000 scale map of both the Scafell Pike area and the Summit of Pillar on the reverse of the main 1:40,000 maps


These two images show Ben Nevis again but this time showing how a 1:40,000 Harvey Maps (right) who use contour colouring to help visualise major land forms, compared to 1:25,000 OS maps (left). Notice the lack of cluttering in the Harvey Map and see how contour features are more clearly defined.


It is very important to know what scale of map you are using as this will have an impact when it comes to measuring distance (we will cover this in a later article). ALL maps will have the scale printed on the cover and on the map itself.

So just be aware.


Both Harvey Maps and OS Maps have a wider range of maps and scales that they produce, from road maps and cycling maps to National Trail maps and bespoke mapping. What we have focused on in this article is their more popular maps which most of us will use regularly.

Below is the question sheet to this article.

Question Sheet 1.1
.pdf
Download PDF • 684KB

Answers to these questions are in the next Part of this series.

Next Up:


The next article in this series will be Part 2: Symbols and Features


Stay tuned for updates by signing up to my Newsletter!

Learn More:


For more information on Ordnance Survey and Harvey Maps take a look at the links below:


I hope this article has proved useful for those of you new to navigation and trying to get your head around maps and scales. To learn more about map scales, navigation and to get out into the hills and mountains, take a look at my navigation courses and get in touch!


All successful bookings for my courses will receive a 10% off discount code to use on Harvey Maps and products from their website!


See you At The Edge!

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