Mercator Maps

What makes a map using Mercator Projection, as it has become known, different to other maps? It is that the meridians are vertical parallel lines of equal spacing and the latitude parallels are parallel straight lines in the horizontal plane. This means that when a straight line is drawn on a Mercator map it is a line of constant true bearing as the ratios of longitude and latitude are accurate at any point. This is what makes maps using Mercator Projection ideal for charting courses at sea. Mercator Projection (also known as Cylindrical Projection) is less useful in the making of world maps due to the way in which it distorts scale, resulting in areas becoming overly large the farther they are away from the equator.

Mercator published his world map in 1569 having expressed his intention to make it suitable for navigation. The map was originally entitled Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendate Accommodata, the latter part of which translates as ‘Adapted for Use in Navigation’. The use of parallel lines against which courses are plotted heralded a major change in the way charts and maps were produced, and still forms the basis on which modern, sophisticated navigation methods are based. Mercator was also a skilled engraver and he produced the plates from which the Mercator map was printed in eighteen separate sheets. Before Mercator’s world map there had been a considerable division between the elegant, colourful maps produced by cartographer’s and the more practical charts produced by those who navigated the seas. Mercator’s work drew on the best of both, a fact that he acknowledges in one of the many texts to be found on his world map.

Before producing his most famous work, Mercator had produced another world map with a projection in the shape of two hearts. Mercator did not accept the biblical explanation of the creation of the world, and his beliefs found him in trouble with the Inquisition. In 1544 Mercator was imprisoned for several months, suspected of Lutheranism. Mercator had not published or preached anything that expressed his opinion on the word of the bible, yet it took seven months for his friends and supporters to secure his release from a dungeon in a local castle.

Mercator, so famed for having made such a major contribution to the navigation of the seas, never spent a day out at sea.