ZingPath: Earth's Topography and Mapping

A contour map is also known as a topographic map. These maps detail the shape of the Earth's surface using contour lines to represent elevation changes. Topographic maps may also contain symbols that show man-made objects such as buildings and roads.

Each contour line on a map represents a change in elevation, which remains consistent throughout the map. To determine the elevation of each line, a contour line interval key may be present or can be deduced from the labeled reference contour lines. For example, if there are five lines between a 0-foot elevation mark and a 500-foot elevation mark, each line represents a change of 100 feet in elevation.

By examining the contour lines, landforms can be easily identified on a topographic map. A hill is represented by concentric circular shapes with a small circle at the top. A cliff is shown by contour lines that are very close together, sometimes running together and looking like a dark line. A delta plain is represented by a triangle projecting into a lake or sea. A valley is represented by lines that look like nested "V" shapes. The closer the lines are to each other, the steeper the area. On the other hand, the farther lines are from each other, the flatter the area. To determine altitude at a particular location on a map, contour lines are used. Locate a labeled reference contour line, and add or subtract the difference between the reference line and the location line to determine the altitude at any point.

The United States Geographical Survey creates most of the topographic maps that are used in the United States today.