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# Understanding Contour Lines on a Map

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In this video, you will learn how about the contour lines of a hiking map

These are essential to know whether you're going up or down, and by how much.

Voice-over by Dominic di Rollo

Understanding contour lines on a map.

In this video, you are going to learn how to read and to use the contour lines on a map.

Put simply, for the entire area of the map they allow you to the answer the question : "is the terrain flat or sloping? " and if the answer is sloping : "is it sloping uphill or downhill?" The information from the contour lines is essential for planning your hikes.

First of all, what is a contour line? It's an imaginary line which connects points of the same altitude. On a map these are represented by continuous lines, which can be of different thicknesses.

Two adjacent contour lines are spaced by a certain interval, or difference in altitude, like 2 steps on a staircase.

For example, if this interval is 10m, the terrain increases in height by 50m every 5 contour lines.

This interval, or difference in altitude, which is equidistant, is generally 10m on a 1:25000 map.

How do we use contour lines? Every 5th contour line is slightly thicker, this is an index contour line. The index contour line is often a round number which corresponds to the altitude of all the points along the line.

Note that the numbers are usually written in the direction of the summit.

The contour lines allow you to estimate the difficulty of a trail : the closer together they are, the steeper the slope, the further apart they are the gentler the slope.

To practice, use a map you have at home, or for a hike you're planning and try to imagine the landscape in 3D from the contour lines on the 2D map.

Now you know how to use the contour lines, you can start planning your hikes. Over to you!