Map Projections

The basic problem in displaying the real world, which appears in three dimensions, onto the two-dimensional surface of a map is addressed by the map projection. Because there is no way to accomplish this transformation without distorting at least one of the basic elements indicated on the map (angles, areas, distance, and direction), a means of projecting the information contained on the map must be selected. Although no map can show all of these basic relationships in their true dimensions, many projections are able to display at least one of them accurately and truly. For this reason, it is quite important that when using a map for a specific purpose, attention is paid to the projection of the map. Geographers and others working with maps must be aware of the limitations of the projection they employ to display their data, and how it may affect the spatial relationships they wish to analyze. In theory, a limitless number of map projections might be constructed, and with the development of computer cartography, many options are readily available. Today, with a click of the computer mouse the projection of a map and the information it contains may be changed instantaneously, an option made available to geographers only in recent years. A number of projections have limited application and are used only for highly specialized work. However, over the past several centuries, some projections have become “standard” in the sense that they are used more than others for certain purposes such as comparing relationships between areas, navigating on the high seas or during transoceanic flights, or other types of uses.