Topography is the physical shape of the land, particularly as it relates to elevation. Topographic maps are two-dimensional graphical representations of the three-dimensional topography that also provide a detailed and accurate inventory of what exists on the land surface, such as geographic and cultural features.

Topographic maps are distinguished from other maps in their representation of elevation as contour lines. Contour lines are drawn to match the shape of physical features and successive contour lines represent ascending or descending elevations. This allows a user to quickly discern the shape of any landform, determine its elevation, and estimate the rate of elevation changes. For example, a round hill would appear as a series of concentric closed loops that become successively smaller with increased elevation. The closer the contour lines are to one another, the steeper the slope.

In addition to contoured elevations, topographic...