The Flemish cartographer Gerhardus Mercator (1512-1594) was among the first makers of modern atlases and is best known for his great world map, or chart, using the projection that has acquired his name.

In the history of cartography the work of Gerhardus Mercator illustrated a significant departure (though by no means a complete break) with the geographical traditions of the Middle Ages and those established by the revived Ptolemaic geography. It also signaled the late Renaissance convergence of academic cartography with the practical needs of navigators, an important step in the creation of that dynamic unity between science and technology that is one of the signal characteristics of the modern world.

Mercator was born Gerhard Kremer in Rupelmonde, Flanders, on March 5, 1512. He studied with the cosmographer Gemma Phyrisius at the University of Louvain and gained practical experience as an instrument maker and surveyor. His early successes brought him into close contact with the court of Emperor Charles V; but under growing pressure for his Protestant beliefs, he emigrated to the German Rhineland in 1552. There he settled permanently with his workshop in Duisburg, and in 1564 he became cosmographer to the court of the Duke of Jülich, Cleve, and Berg.

Mercator's early works prepared the way for his world map of 1569. These included maps of the Holy Land (1537), the world (1538), Flanders (1540), Europe (1554; rev. ed. 1572), and Britain (1564). He also constructed terrestrial and celestial globes (1541 and 1551). These maps reflected the critical compilation and rendition of a growing body of data that were typical of the cartographical methods of the time. The 1554 map of Europe showed Mercator's willingness to abandon the theories of Ptolemy and other predecessors in the light of further advances in knowledge. The length of the Mediterranean was shortened by 10 degrees (though remaining disproportionately long), and the stretch of land between the Baltic and the Black seas was widened.

Others may have experimented with the "Mercator projection" before Mercator; he was the first, however, to give cartographical rendition to the solution to the problem for which the projection was designed. This was the problem of plotting loxodromes (rhumb lines, or lines of constant bearing) as straight lines on a navigator's chart. Meridians of longitude converge at the poles, but if lines of constant bearing are plotted as cutting across them at constant angles, they must appear as parallel on the flat map, or chart. This requirement in turn necessitates a proportional increase in parallels of latitude from the Equator to the poles (proportional to the increasing east-west distances between the meridians). The shape of sectional areas is preserved, and the loxodromes can now be plotted as straight lines, although this is achieved at the expense of distortion of the world map as a whole (that is, the radical increase in relative proportions from Equator to poles, hence the apparent gigantism of land masses like Australia and Greenland on a Mercator projection map). This was the solution rendered in the 1569 world map, but it was not fully accepted by navigators until small area charts based on the projection began to be published in the next century.

The rest of Mercator's life was taken up with a three-part publishing project. He planned to print maps based on Ptolemy's Geography, maps of the ancient world, and an atlas of modern maps. The Ptolemaic maps were published in 1578, and the modern atlas appeared in three sections between 1585 and 1595. The entire work (mainly maps of western and southern Europe), totaling 107 maps, was published in 1595. Mercator, however, had died the year before at Duisburg, on Dec. 2, 1594.

Further Reading

• Mercator's place in the history of cartography is discussed in Lloyd Arnold Brown, The Story of Maps (1949), and Gerald Roe Crone, Maps and Their Makers: An Introduction to the History of Cartography (1953; 4th rev. ed. 1968). His relation to the new geographical knowledge is examined in the appropriate chapters of Boies Penrose, Travel and Discovery in the Renaissance, 1420-1620 (1952), and John Horace Parry, The Age of Reconnaissance (1963).
• Blondeau, R. A., Mercator van Rupelmonde, Tielt: Lannoo, 1993.