Quality Mountain Days
 
                                                                 & Advanced workshops


Reading Contours and Relief

Understanding the shape of the land by looking at a map is a very useful skill and can be essential if you’re going to be walking in mountainous terrain. The height and shape of the land is shown on a map using ‘contour lines’. These lines appear as thin orange or brown lines with numbers on them. The number tells you the height above sea level of that line.
A contour line is drawn between points of the same height, so any single contour line will be at the same height all the way along its length. The height difference between separate contour lines is normally 5 metres, but it will be 10 metres in very hilly or mountainous areas. The map key will tell you the contour interval used.

The picture shown illustrates how a landscape can be converted into contour lines on a map. An easy way to understand and visualise contour lines is to think of them as high tide lines that would be left by the sea. As the water level drops it would leave a line every 10 metres on the landscape. These marks would be contour lines.

Being able to visualise the shape of the landscape by looking at the contour lines of a map is a very useful skill that can be developed with practice. It will allow you to choose the best route for your journey. When reading contour lines on a map it’s helpful to remember the numbering on them reads uphill. It might be useful to imagine that to read contour line numbers you have to be stood at the bottom of the hill looking up it, otherwise the numbers would be upside down.

Other useful things to look out for when reading contour lines are rivers, which usually flow into valleys, or areas with very few contour lines, which will be flat.

This picture shows how contour lines can be used on maps to describe different landscapes. Even though all the lines look similar at first, they are describing very different landscape features. The closer together the contour lines, the steeper the slope of the hill. If a hill is very steep the contour lines might even merge into each other.

A spur is a ‘V’-shaped hill that juts out.

A simple way to tell a valley from a spur when looking at contour lines is to remember that if the ‘V’ points uphill it’s a valley, if it points downhill it’s a spur. 

How do we show height on maps?

Contour lines are a map’s way of showing you how high the land is. They join together places of the same height and form patterns that help us to imagine what the land actually looks like.

You will notice that there are a series of contour line that are bold and darker,  These are called index lines and are usually marked with the height above sea level that the contour represents.

These index lines are very useful when calculating the height difference between two points as you can count up in 50 metre increnments instead of 10 m.

There are many areas on the map where the contour height is not shown, the index lines allow us to trace along the contour line easily until we can find the height.
 



 
‘Naismith’s rule’
Remember that the closer together the contour lines are, the steeper the land. Contour lines that are wide apart show us that the land is flatter.
 
When you're travelling across steep landscapes (where contour lines are very close together) it will add time on to your journey.

Naismith said that you should allow an extra minute of walking time for every 10 metres of height that you climb.

On OS maps contour lines are usually drawn at 10 metre intervals on a 1:50 000 scale map and at 10 metre intervals on a 1:25 000 scale map unless the terrain is flatter where 5 metre intervals are used.

With Harveys maps the contour interval is 15 metres so a little care is required if you use both types.






Important: Participation Statement

Climbing, hillwalking and mountaineering are activities with a danger of personal injury or death.
Participants in these activities should be aware of and accept these risks and be responsible for their own actions and involvement.


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