How to read a topographic map: contour lines, grid references and symbols

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A topographic map shows the shape of the land as well as what is on it: hills, valleys, cliffs, rivers, paths and buildings. Learning to read one makes walking and hiking safer, and turns a flat sheet of paper into a picture of the landscape. Here are the essentials.

Scale

The scale tells you how distance on the map relates to distance on the ground.

At 1:25,000, 1 cm on the map is 250 metres on the ground. This is the usual scale for detailed walking maps, showing field boundaries and small paths.
At 1:50,000, 1 cm is 500 metres. Good for longer routes and an overview.

Use the scale bar printed on the map, or a ruler or compass edge, to measure distances. A piece of string laid along a winding path gives a fairer measure than a straight line.

Contour lines

Contour lines join points of equal height above sea level. They are the key to reading the shape of the land.

The contour interval is the height difference between neighbouring lines, printed in the map's key. It is commonly 5 or 10 metres on walking maps, but check, because it varies between maps and countries.
Thicker "index" contours appear at regular intervals with their height written on them. The numbers are written so that they read uphill.
Close together means steep ground. Far apart means gentle ground. Lines merging or very tightly packed can mean a cliff, which usually has its own symbol.

Recognising terrain features

Hill or summit: a series of closed rings, getting smaller towards the top, often with a spot height.
Valley: contour lines form a V or U shape that points uphill, often with a stream running through it.
Spur or ridge: contour lines form a V or U that points downhill.
Saddle or col: a low point between two high points, looking like an hourglass.
Concave slope: lines close together at the top and spread out at the bottom; you can usually see the whole slope from the top.
Convex slope: spread out at the top and close together at the bottom; the steep part is hidden from above, which can be dangerous in poor visibility.

Grid references

Most topographic maps have a grid of numbered squares, letting you describe any location precisely.

Read along the corridor, then up the stairs: first the number on the bottom or top edge (eastings), then the number on the side (northings).
A four-figure reference identifies a grid square, using the lines at its bottom-left corner.
A six-figure reference divides each square into tenths in both directions, pinpointing a location within about 100 metres on a typical walking map.

Many national mapping systems add letters for larger grid zones. Learn the system for your country's maps, and practise by finding grid references for places you know.

Symbols

The key, or legend, explains the symbols. Common ones include paths and rights of way, different types of road, woodland, water, buildings, churches, viewpoints, parking and boundaries. Colours carry meaning too: blue for water, green for woodland or public access land on many maps, brown or orange for contours. Spend ten minutes with the key before you set out.

Using the map with a compass

Set the map: turn it so that its features line up with what you see around you, or so that the grid north on the map points north on your compass.
Take a bearing: lay the compass edge along your route on the map, turn the housing so its lines match the map's grid lines with the arrow to north, then hold it flat and turn yourself until the needle sits in the arrow. Walk in the direction of travel.
Account for magnetic variation: the difference between grid north and magnetic north. It is printed on the map and changes over time and by location, so use the current value.

Practise on easy, familiar ground before relying on it in hills or bad weather.

Digital maps

Phone apps and GPS devices with topographic maps are excellent, and they can show your exact position. But batteries run out, screens fail in cold and rain, and signal disappears. Download maps for offline use, carry a power bank, and take a paper map and compass as backup, especially in the mountains. What is your favourite map, or where did map reading save your day out? Share your questions and stories in the comments.