Mercator, Gerhard (1512-1594)

Flemish cartographer, geographer, and mathematician

Mercator, the world's most influential mapmaker, modernized cartography according to mathematical principles, facilitated navigation by charts, invented the projection that bears his name, and coined the term "atlas" to refer to a book of maps.

Born as Gerhardus Cremer, or Kremer, the son of a shoemaker, on March 5, 1512 in Rupelmonde, Flanders, he began using the Latin form of his surname upon entering the University of Louvain in 1530. Both "mercator" in Latin and "cremer" in Flemish, which is cognate with "Kramer" in German, mean "merchant." Raised by his uncle, Gisbert Mercator, who intended him for the Roman Catholic priesthood through the Brethren of the Common Life, he attended secondary school at 'sHertogenbosch and was apparently quite pious. His religious doubts began when his philosophical and theological studies at Louvain prompted him to consider whether biblical and ancient Greek cosmologies could be reconciled. These questions gradually expanded into concern for accurate geography in support of cosmological beliefs. After receiving his M.A. from Louvain in 1532, he studied mathematics, astronomy , and geography privately under Reiner Gemma Frisius (1508–1555). Also in the early 1530s he acquired skill as an engraver from Gaspar Van der Heyden (Gaspar à Myrica), a goldsmith in the town of Louvain.

In 1536, Mercator created his first important cartographic work: a globe. His reputation grew internationally over the next few years, especially through his maps of Palestine in 1537, the world in 1538, and Flanders in 1540, as well as his celestial globe of 1537 and his terrestrial globe of 1541. His multifaceted expertise as artist, surveyor, instrument maker, geographer, and mathematician all contributed to his fame. About this time he began experimenting with new projections for maps.

Mercator's frequent travels in search of geographical data aroused suspicion, especially when he, a Catholic, ventured into Protestant lands. In 1544, he was arrested for heresy and jailed for seven months. Although he was released through the intercession of the University of Louvain, the whole experience soured him on the Low Countries and Catholicism. He soon converted to Protestantism and, in 1552, moved to Duisburg, a Protestant enclave in northern Germany, where Duke William of Cleves (1516–1592), brother of the fourth wife of English King Henry VIII, planned to establish a university. The university lasted from 1555 to 1818, but was refounded in 1972. Since 1994, its official name in German has been Gerhard-Mercator-Universität-Gesamthochschule Duisburg.

Mercator served in Duisburg as the duke's cosmographer. He ran his own shop, hired his own artisans, published his own books, and did some teaching. Through the patronage of the court of Cleves, the last four decades of Mercator's life were secure, happy, and productive. Among his best works of this period was his 1554 map of Europe .

In 1569, he first published maps based on "Mercator projection." In the systematic vocabulary of cartography, "projection" is a technique or strategy for representing the curved surface of the world or any part of it on the flat surface of a map. There are three general types of projections: cylindrical, conic, and azimuthal, which respectively project the surface of a sphere onto a cylinder, cone, or plane. Some aspect is gained and some aspect is lost with each type. Mercator projection is the best known and most useful of the cylindrical projections. It shows all meridians of longitude as if they were parallel to each other, and thus not converging at the poles; and all parallels of latitude as straight-line segments of equal length, increasing in distance from each other as their distance from the equator increases. The main advantage of Mercator projection is in marine navigation, because all direct sailing courses can be imposed as straight lines. Its main disadvantage is that representations of land areas become more distorted the closer they are to the poles, because of unnatural east-west enlargement.

In 1585, Mercator used the word "atlas" for his book of maps, taking it from the name of the ancient Greek mythological Titan who carried the sky on his shoulders. This gigantic atlas, begun in the 1570s but still unfinished when he died in Duisburg on December 2, 1594, contained corrected versions of the ancient maps of Ptolemy (ca. 130) and detailed, up-to-date maps of many parts of Europe.

See also Latitude and longitude; Mapping techniques; Surveying instruments