OS Team • Map Reading • Jun 05, 2022 • 5 mins
Learn all about contour lines
Learn the use and meaning of contour lines on a map and understand how to use them to when you're out and about or planning routes. Understanding contours will improve your map reading skills.
Hills, slopes and mountains are represented on a map using contour lines. By studying the contour lines you can work out lots about the surrounding terrain including gradients of hills, valleys and steepness of climbs. If you already know the basics, check out our advanced guide to reading contours and relief.
Check out our Pathfinder guide titled Navigation Skills for Walkers which includes information on map reading, compasses and GPS.
How are hills and mountains shown on a map?
The ability to understand the shape of the ground from a map is a useful skill to learn, particularly in mountainous landscapes and when you are out and about hiking. Look for the height and shape of the ground which is shown on 1:25 000 scale maps (OS Explorer) by brown contour lines. A contour is a line drawn on a map that joins points of equal height above sea level. For 1:25 000 scale maps the interval between contours is usually 5 metres, although in mountainous regions it may be 10 metres.
How contour lines show a pair of small hills
You can see from the picture above the link between the shape of a hill and the contours representing it on a map. Another way of thinking about contour lines is as a tide mark left by the sea as the tide goes out, leaving a line every 5 metres.
Top tip!
Remember contour numbering reads up hill – in other words the top of the number is uphill and the bottom is downhill. Also remember the closer contour lines are together, the steeper the slope.
How steep is the slope?
The steeper the slope the closer together the contour lines will be. You can see this in the examples below:
Shallow slope - contours are spaced well apart
Steep slope - contours are close together
Watch Steve Backshall explain contours
Putting it all together
Now you know how contour lines are created, you can use them to visualise the terrain they show, remembering that:
- Contours follow points of equal height. If you can't see a number, follow the line to find one
- On some maps, not all contours will have labels and are printed slightly lighter, but you can work out the height by looking at labelled contours above and below
- The best way to understand contours is to practice by comparing a map to the real world or photographs
Practice map
Contour lines on a map
- The close together contours in the top left show a steep slope
- The spaced out contours in the bottom left show a shallow slope
- The upside down v-shape on the right is a small valley that also goes downhill from the top of the map to the bottom
- There is a hill peak just over 430m at the top centre of the map
- Near the middle of the map, at the 350m contour label, there is a flat area that's a ridge or spur
Now that you have learnt the basics, you can further your knowledge with our advanced guide to reading map contours and relief.
Published: Jun 05, 2022 Edited: Jun 30, 2022
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Greetings, fellow outdoor enthusiasts! I'm here to dive into the intricacies of map reading, particularly focusing on the fascinating world of contour lines. My passion for cartography and outdoor exploration has led me to accumulate a wealth of knowledge in this field, making me your go-to expert for understanding the nuances of terrain representation on maps.
Now, let's delve into the concepts introduced in the article about contour lines. Contour lines are a fundamental aspect of map reading, offering crucial insights into the landscape, be it hills, slopes, or mountains. Here's a breakdown of the key concepts covered in the article:
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Contour Lines:
- Contour lines are illustrated on maps to represent points of equal height above sea level.
- These lines form a network that allows map readers to visualize the elevation and shape of the terrain.
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Mapping Scale:
- The article mentions the use of 1:25,000 scale maps, specifically the OS Explorer maps. This scale is crucial as it determines the level of detail represented on the map.
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Contour Intervals:
- The interval between contour lines on 1:25,000 scale maps is usually 5 meters, though it may vary, particularly in mountainous regions where it could be 10 meters.
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Contour Numbering:
- Contour lines are accompanied by numbers, and the top of the number indicates the uphill direction, while the bottom signifies downhill.
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Interpreting Contour Lines:
- The proximity of contour lines reflects the steepness of the slope. Closer lines denote steeper slopes, while wider spacing indicates a shallower incline.
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Visualizing Terrain:
- Contour lines provide a visual representation of the terrain. They allow readers to discern features such as hills, valleys, and the overall topography.
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Reading Contours in Maps:
- The article emphasizes the importance of practicing map reading by comparing maps to the real world or photographs. This hands-on approach enhances the ability to interpret contour lines accurately.
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Advanced Guide:
- For those seeking to deepen their understanding, the article suggests an advanced guide to reading map contours and relief. This resource likely delves into more intricate aspects of interpreting contour lines.
In conclusion, understanding contour lines is a vital skill for anyone venturing into the great outdoors. By grasping these concepts, you can navigate diverse landscapes with confidence, whether you're hiking through hills or exploring mountainous regions. So, gear up, grab your maps, and let the contours guide you on your next adventure!
