Contours and terrain

Seeing shape in lines.

How they work

Each contour joins points of equal height, at a fixed interval such as ten metres. Close together means steep, far apart means gentle, and the pattern reveals the landform.

A V pointing uphill is a valley or stream; pointing downhill, a spur.
Concentric rings shrinking inwards mark a summit.

Practical use

Terrain shape is the most reliable thing to navigate by, because it does not change. Fences, tracks and forest edges all do.