How to read contour lines

Contour lines are how a flat map shows the shape of the land. Once you can read them, a page of orange squiggles turns into hills, valleys and cliffs.

What a contour line is

A contour line joins together points that are the same height above sea level. Imagine flooding the land and letting the water rise 10 metres at a time: each new shoreline is a contour line. Walk along one and you’d never go up or down.

On most British walking maps, and in Contour, there’s a contour every 10 metres. Every fifth line, at 50 metres, 100 metres and so on, is drawn bolder and usually has its height written on it. These are called index contours, and they’re the quickest way to tell which way is up.

Spacing shows steepness

The closer the lines, the steeper the ground. Ten metres of height packed into a short distance is a steep slope; the same ten metres spread over a long way is gentle.

Which way is uphill?

Contour lines don’t have arrows, so look for clues: the heights written on index contours, spot heights (a dot with a number, often on a summit), the sea or a lake (always at the bottom), and streams, which always run downhill along the bottom of valleys.

Recognising landforms

Hills and summits

Closed rings that get smaller as they go up. The smallest ring is the top; there’s often a spot height inside it.

Valleys

Contours bend into V or U shapes, with the point of the V pointing uphill. A stream, drawn in blue, often runs along the middle.

Spurs and ridges

Also V or U shapes, but the point of the V points downhill. A spur is a tongue of high ground sticking out from a hill. The easiest way to tell a spur from a valley is to check the heights on either side.

Cols and saddles

A dip in the high ground between two summits, shaped like a horse’s saddle. Contours form an hourglass between two sets of rings.

Putting it into practice

When you look at real land (or a view in Contour), describe it in these terms: “I’m on a slope that drops steeply to the sea on my left, with a rounded hill ahead and a valley running down to my right.” Then hunt the map for that pattern: steep contours meeting the coast, rings ahead, Vs pointing back up towards you. It’s the core skill of navigation, and every round of Contour is practice for it.