How to Read a Topographic Map

You unfold the map and see brown rings, blue threads and tiny symbols. It tells you nothing yet. That's normal. Topo maps follow a few rules, and once you know them the squiggles turn into hills.

What kind of map is this?

A topographic map shows the shape of the land, not only the roads. People also call them contour maps or topo maps.¹ The 1:24,000-scale maps are among the best-known U.S. Geological Survey topographic maps.² Other countries have their own national series, and the look of each one varies.¹

Problem one: what do the brown lines mean?

Each contour line joins points at the same height. In plain terms, if you walked along one line you'd never go up or down.¹

The gap between neighbouring lines tells you how steep the ground is.

• Lines close together mean a steep slope.
• Lines far apart mean a shallow slope.³
• Lines that merge show a cliff.³

For a driver, that's the useful part. A track that crosses many tight lines in a short run is climbing or dropping hard. A track following a wide gap is on gentler ground. The map can't tell you the surface or the road condition, so check those with the land manager.

Problem two: how high is each step?

The contour interval is the height difference between one line and the next. On a single map it stays the same.³ One example map on Wikipedia uses 20 feet.³

Look in the margin for the interval. Without it, you can see steep and gentle but you can't put a number on it. Check whether your map counts in feet or metres.

Problem three: what do the symbols mean?

Maps use small signs for roads, buildings, water and more. Colors can be used to indicate a classification of roads.¹ The signs are usually explained in the margin of the map, or on a separate sheet.¹

That margin box is the legend. Read it before you set off. Two maps of the same area from different makers can use different signs for the same thing.¹

Spend a minute on these:

• The line styles for sealed roads, unsealed roads and tracks.
• Gates, fences and private land markings, if the map shows them.
• Water: streams, lakes and crossings.
• The map's date, if it's printed.

A track on a map is not a promise that you can drive it today. Closures and washouts won't appear on a printed sheet. Check with the agency that manages the land before you go.

Problem four: where am I on it?

Match the land to the paper. Find a feature you can see, such as a river bend or a ridge line, and find it on the map. Then use contours to confirm: if the ground falls away to your left, the lines should show that.

A compass helps here, and using one next to a map is a skill worth practising. To tell someone else your position, learn grid references.