The Mercator world map of 1569 is titled Nova et Aucta Orbis Terrae Descriptio ad Usum Navigantium Emendate Accommodata (Renaissance Latin for "New and more complete representation of the terrestrial globe properly adapted for use in navigation"). The title shows that Gerardus Mercator aimed to present contemporary knowledge of the geography of the world and at the same time 'correct' the chart to be more useful to sailors. This 'correction', whereby constant bearing sailing courses on the sphere (rhumb lines) are mapped to straight lines on the plane map, characterizes the Mercator projection. While the map's geography has been superseded by modern knowledge, its projection proved to be one of the most significant advances in the history of cartography, inspiring map historian Nordenskiöld to write "The master of Rupelmonde stands unsurpassed in the history of cartography since the time of Ptolemy." The projection heralded a new era in the evolution of navigation maps and charts and it is still their basis.
The map is inscribed with a great deal of text. The framed map legends (or cartouches) cover a wide variety of topics: a dedication to his patron and a copyright statement; discussions of rhumb lines, great circles and distances; comments on some of the major rivers; accounts of fictitious geography of the north pole and the southern continent. The full Latin texts and English translations of all the legends are given below. Other minor texts are sprinkled about the map. They cover such topics as the magnetic poles, the prime meridian, navigational features, minor geographical details, the voyages of discovery and myths of giants and cannibals. These minor texts are also given below.
A comparison with world maps before 1569 shows how closely Mercator drew on the work of other cartographers and his own previous works, but he declares (Legend 3) that he was also greatly indebted to many new charts prepared by Portuguese and Spanish sailors in the portolan tradition. Earlier cartographers of world maps had largely ignored the more accurate practical charts of sailors, and vice versa, but the age of discovery, from the closing decade of the fifteenth century, stimulated the integration of these two mapping traditions: Mercator's world map is one of the earliest fruits of this merger.
Mercator's 1569 map was a large planisphere, i.e. a projection of the spherical Earth onto the plane. It was printed in eighteen separate sheets from copper plates engraved by Mercator himself. Each sheet measures 33×40 cm and, with a border of 2 cm, the complete map measures 202×124 cm. All sheets span a longitude of 60 degrees; the first row of 6 sheets cover latitudes 80°N to 56°N, the second row cover 56°N to 16°S and the third row cover 16°S to 66°S: this latitude division is not symmetric with respect to the equator thus giving rise to the later criticism of a Euro-centric projection.
It is not known how many copies of the map were printed, but it was certainly several hundred. Despite this large print run, by the middle of the nineteenth century there was only one known copy, that at the Bibliothèque Nationale de France. A second copy was discovered in 1889 at the Stadt Bibliothek of Breslau along with maps of Europe and Britain. These three maps were destroyed by fire in 1945 but fortunately copies had been made before then. A third copy was found in a map collection Mappae Geographiae vetustae from the archives of the Amerbach family which had been given to the library of the University of Basel. The only other complete copy was discovered at an auction sale in Luzern in 1932 and is now in the map collection of the Maritiem Museum Rotterdam. In addition to the complete copies there is a single page showing the North Atlantic in the Mercator atlas of Europe in the British Library. Many paper reproductions of all four maps have been made. Those at full scale, providing access to the detail and the artistry of Mercator's engraving, are listed next. Images of the Basil, Paris, and Rotterdam impressions can be found online.
The Basel map is the cleanest of the three extant versions. It is called the 'three strip' version because it is in three separate rows rather than a single assembled sheet. It was photographically reproduced at a reduced scale by Wilhelm Kruecken in 1992; more recently (2011) he has produced a full-scale and full sized (202×124 cm) reproduction of the map along with a five volume account (in German) covering all aspects of Mercator's work. Medium resolution scans of the separate sheets and a composite of all 18 scans are accessible as follows.