ABSTRACT
A map projection is a 2-D model whereby the curved surface of the Earth is portrayed on a flat map. If one looks only at a small portion of the Earth’s surface such as a city map, it appears that local features on the map correctly portray the same features as viewed by a person walking or driving in that area. However, when dealing with larger and larger portions of the Earth’s surface, distortion and the challenge of true map representation grow exponentially. An extreme example of distortion is recognized by many elementary schoolchildren who look at a comparison of Alaska and Brazil-first on the globe, then on a Mercator world map. On the globe, Alaska appears noticeably smaller than Brazil, but on a Mercator map projection of the world, Alaska appears much larger than Brazil. The problem is that, on the globe, all meridians converge at the North Pole and South Pole. On the projection at the equator, the spacing of the meridians is identical to the meridian spacing on the globe. But the meridians remain parallel on the projection, and features nearer the poles appear grossly exaggerated in size. In fact, neither the North Pole nor the South Pole can be shown on a Mercator map, which touches the Earth at the equator as shown in Figure 10.1a.
