Types of Maps

Maps differ in the amount and kind of information they give, and the graphic devices used to convey the information. Some of the types of maps in common use are the following:

General Reference Maps

are maps, usually of relatively large areas, that show major land and water areas, and such features as cities and political boundaries. Atlas maps are generally of this kind.

Topographic Maps,

prepared from original surveys and aerial photographs, show all important natural and man-made features in relatively small areas, usually in considerable detail. Military and most maps published by the U.S. Geological Survey are of this kind.

Planimetric Maps,

unlike topographic maps, make no attempt to show varying elevations. They are drawn as though the earth were a plane (flat) surface.

Charts

are maps used in sea and air navigation. They are specially designed for plotting a course.

Thematic, Or Topical, Maps

provide information on a single subject. Usually the mere outline of the area under consideration is shown. Against this simplified background the special information is made to stand out by various methods. For example, colors or patterns may be used to show the distribution of rainfall, soil types, or election results. Dots may represent places where a firm has retail sale outlets, the location of historical sites, or the like. Variations of quantity—of rainfall, population, or crop yields, for example—may be shown as variations in color or tones of gray; or isopleths (“equal value” lines), such as the isobars on weather maps.

Cartograms

are maplike diagrams. They present statistics in a pictorial way. A cartogram might show, for example, the countries of the world in their proper map position, but with each country distorted to a size proportionate to its population. On such a cartogram, Italy would be more than twice the size of Canada.