What is a contour interval on a topographical map?

The space between contour lines on a topographical map is a contour interval. The contour interval is an even space that represents an increase in elevation. For instance, if the map uses a 20-foot interval, there are contour lines at zero, 20, 40, 60, 80 and 100 feet.

Topographical maps can use larger intervals to indicate steeper terrain with larger increases in elevation. The shapes of contour lines and contour intervals are used to indicate the shape of the land mass it represents. The size of the contour interval indicates the steepness of the incline. Short contour intervals represent steep inclines, while long contour intervals equal flatter or more gentle slopes.