For centuries, mankind has traveled around the world by land and sea for the purposes of commerce, conquest, migration, and exploration. The skill of navigating from one place to another requires either a first-hand knowledge of ‘the lay of the land’ from repeat trips, or the assistance of maps. For land-based journeys, features such as mountains, rivers, man-made objects and even dominant animal and plants were often described on maps to aid in navigation. For open ocean travel, however, the lack of descriptive features meant that ancient maps were often little help to the seafarer until land was spotted again. But by the mid-1500s (still relatively fresh off the discovery of the ‘New World’), the potential for wide-scale ocean travel – and subsequent land exploration of claimed territories – had become a very important, potentially profitable and exciting prospect among Europeans. The powerful naval nations were eager to extend their territories to the Americas. The difficulty of ascertaining true, off-cardinal directions, however, was the primary handicap of ancient maps: a northwest-southeast line on a map rarely ever corresponded to the actual bearing, making precise sea-travel navigation quite difficult, even for those with a lifetime of training. But then came a breakthrough in 1569, a Flemish cartographer named Gerhardus Mercator developed a map which showed true directions from any one point to another. When a line is drawn (called a loxodrome) connecting the two points, the compass bearing is revealed. As one can imagine, this map soon became an essential tool for all mariners, and became so popular that its general form has been recognizable to people for hundreds of years as a standard way to show the Earth’s surface. This projection also preserves the shape of features relative to other nearby features, such as coastlines and rivers. However, the major drawback of the usefulness of this map projection is that it distorts spatial areas rapidly with increasing latitude (toward the poles). For instance, Greenland (centered at 45 degrees west, 70 degrees north) appears to cover an area comparable to that of the continent of Africa (centered at 20 degrees east, 5 degrees north), but in reality, Africa is nearly 14 times larger! Also, due to the method of mapping this projection, the poles are impossible to show, and only areas very near the equator are represented with accuracy. Despite these limitations, however, the Mercator projection is still employed as a navigational aid to this day, and was instrumental in the advancement of other map projections produced later for other purposes. Source.