| Connects | Points of equal elevation |
| Close together | Steep terrain |
| Far apart | Gentle terrain |
| Contour interval | Elevation change per line |
A contour line on a topographic map connects points of equal elevation, so the pattern of lines reveals the terrain’s shape and steepness. Lines close together indicate steep ground; lines far apart indicate gentle slopes. The contour interval — the elevation change between adjacent lines — is given in the map’s legend.
Reading them
Counting contours gives you elevation gain; tight lines mark a steep slope or ridge. They’re the heart of a topographic map.
Frequently asked questions
What is a contour line?
A contour line is a line on a topographic map that joins all points at the same elevation. Following one keeps you at a constant height. Together, contour lines turn flat paper into a readable picture of hills, valleys, and slopes.
What does the spacing of contour lines mean?
Spacing shows steepness: lines packed closely together indicate steep terrain (lots of elevation change over a short distance), while widely spaced lines indicate gentle, flat-ish ground. A cliff appears as contours that nearly merge.
What is the contour interval?
The contour interval is the vertical distance between adjacent contour lines, stated in the map legend (for example, 40 feet or 10 meters). Knowing it lets you calculate elevation change along a route by counting the lines you cross.
Sources
- Topographic map symbols — USGS
- Map reading — The Mountaineers