In the previous section, we learned about the map and what everything means on it, if you haven’t read it yet then go back and check it out here. Now we are going to cover one of the most useful assets when navigating, Contour Lines.

Contour Lines

Contour lines are imaginary lines of a constant height that mean you can accurately determine the shape of the landscape. Contour lines make the difference between a typographic map and a normal map, and can be used for navigation without any of the other features.  Many things can change on the ground such as woods are cut down, streams dry up, footpaths get redirected and buildings are built/demolished. Contours are one of your few constants on a map that you can rely on to not change much as your map gets older, for instance if a river dried up you may not be able to see the river displayed on the map but you will be able to see the change in the shape of the land from the contours like a valley to the dried up river.

The basics

So how do lines on a flat map let us know the shape of the land? Imagine you are standing on a hill and there is a line of constant height across the slope where you are standing. Then look up the slope at the ground 10m above you and there is another line. If the ground is steep then the line will be closer to you because it takes less distance for the ground to gain 10m in elevation. Conversely, if the ground is only a shallow gradient then the line would be further away because there is more distance for the ground to gain 10m in elevation.

So to put it simply, the closer the lines are together then the steeper the slope is.

Generally, contour lines are spaced 10 metres apart which means that there is 10m of elevation on the ground between those imaginary lines. Always check exactly what height difference there is between the contours on your map, if you can’t find where it is said on the map then look at the height numbers next to a contour line and find the next line with a height number, whatever the height difference is divided by the amount of contours between them is the amount of elevation each contour represents. If you need to identify which direction a hill is going, one easy way is that the numbers are always facing uphill so if you are reading the number upside down then it will be a downward slope. Another useful thing about these maps is that there is usually a thicker line at certain intervals, usually 50m or 100m, these make it easier to count up the contours and calculate height quickly.

So let’s look at some real-world examples and some of the common things you may be looking for out in the field.

Valley

A valley is a low area between two peaks, they usually contain a river at the bottom of them(the blue line). So on the map on the right, you can see contour lines showing the slope rising from each side of the river.

Cliffs/Steep drops

It is important to be able to recognise steep drops and cliffs when navigating so that you can stay away from going over the top of them. Contours get very close together and merge plus there is also thick black shading depicting the cliffs and rock outcrops.

Slope

On a slope you will see contours going in a linear fashion across the slope, the steeper the slope the closer the contours.

Saddle or Col

A saddle or col is simply a dip between two peaks so using the example below on the left of the saddle you see a steep-ish slope up to the top. In the middle, there is very little contour lines meaning there is a large, fairly flat area and on the right is a shallow slope up to the right-hand peak. On the front and back of the saddle there is a shallow valley where the two peaks meet.

Ridges

Ridges are the opposite of valleys, expect to see a v-shape in the contour lines.

Learning to read contours can take some time to get used to but with practice, you can learn to quickly make a mental image of what the terrain should look like from the contour lines on your map. Look at these examples and remember what shapes the lines are and look for similar examples on a map you have, try to find ridges, valleys, saddles, also pick a random point on the map and try to work out what terrain you might see if you were standing at that location.