A Mercator projection image courtesy of Indiana State University Cartography Dept.

      A map projection attempts to represent one reality in the context of another. In cartography, this means representing a round object, the earth, on a flat surface, paper. The word derives from the Latin “pro,” meaning “forward,” and “iacere,” “to throw.” (Thus, a movie is “thrown forward” onto a screen.)

      The most familiar projection is that of Gerardus Mercator (1512-1594), a Flemish geographer. Mercator envisioned the spherical earth contained in a cylinder. He produced a map with a symmetrical grid in which the meridians are shown as parallel lines. Though it revolutionized cartography, Mercator’s projection seriously distorts extreme latitudes; Greenland appears huge and Antarctica looks like a white elephant lying along the South Pole, which takes up the entire bottom edge of the map. In addition, on a Mercator map a straight line drawn between two points is often not the most direct route.

Politics and Projection Distorting an awkwardly spherical world into an orderly array of rectangles seems a harmless activity, but Mercator's on-location surveys of Flanders landed him in jail for seven months. He's still generating controversy. German historian Arno Peters has argued that the widespread use of Mercator's projection diminishes the importance of equatorial regions in the minds of people in the developed nations in temperate latitudes. His map aimed to portray relative land areas accurately (though creating new distortions in the process). Cartographers bristled, saying Mercator maps were intended for navigation. However, many readers from landlocked communities will recall Mercator projections from their schoolroom walls. [ed.] For more about this debate go to Carto-controversy, Tales of Maps as Weapons of Persuasion and Deception by Mark Monmonier in Mercator's World.

      Other projections avoid the errors of Mercator but insert distortions of their own. Some represent shape accurately, but not distance; others the reverse. A conic projection envisions the earth in a cone (imagine a Sno-Cone) and then flattens out the result. Shapes of the target area are preserved, but not distances. An azimuthal projection takes a specific point and flattens out the surface around it (imagine smashing an orange onto a plate). While it shows accurate distances from the target area, it distorts the peripheral shapes.

      Like a still photograph, a map projection freezes a mutable three-dimensional object into a static two-dimensional image. Since the earth is three-dimensional and constantly changing (albeit slowly), no two-dimensional map can show its surface with complete accuracy. As T.S. Eliot says in “The Hollow Men” (1925):

      “Between the idea
      And the reality
      Between the motion
      And the act
      Falls the Shadow”