The distinctive characteristic of a topographic map is the use of elevation contour lines to show the shape of the Earth’s surface. Elevation contours are imaginary lines connecting points having the same elevation on the surface of the land above or below a reference surface, which is usually mean sea level.

Contour lines are lines drawn on a map with equal elevation points, so elevation would be constant if you followed the contour line physically. The elevation and terrain shape of the contour lines shows. It is useful because they show the form of the land surface on the map–its topography.

In cartography, a contour line (often just called a “contour”) joins points of equal elevation (height) above a given level, such as mean sea level. A contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

Contour lines are lines drawn on a map connecting points of equal elevation, meaning if you physically followed a contour line, elevation would remain constant. Contour lines show elevation and the shape of the terrain. They’re useful because they illustrate the shape of the land surface — its topography — on the map.

Google Maps now has Terrain View, which enables users to see terrain maps for an area. Terrain view shows the 3D elevation of natural geographic features, such as mountains and canyons. Topographic contour lines are overlaid on the map to show elevation levels with altitude information displayed in gray numbers.

Contour line, a line on a map representing an imaginary line on the land surface, all points of which are at the same elevation above a datum plane, usually mean sea level.