Gerardus Mercator

Gerardus Mercator devised the map projection that made ocean navigation practical. Born Gerard de Kremer in Flanders in 1512, the seventh child of a shoemaker, he was educated by an uncle who was a priest, took a degree at Louvain, and studied mathematics, geography and astronomy privately after finding the university's Aristotelian curriculum incompatible with what he observed. He learned engraving, instrument making and italic lettering, and made globes, astrolabes and surveying instruments. He was arrested for heresy in 1544 and held for seven months on suspicion of Lutheran sympathies, and was released for lack of evidence; forty-two others were burned, buried alive or beheaded. He moved to Duisburg in 1552 for safety. The projection was published in 1569 on a world map in eighteen sheets. Its principle is that the meridians are drawn as parallel vertical lines and the spacing of the parallels is progressively stretched towards the poles by exactly the amount needed to keep angles true. The consequence is that a line of constant compass bearing — a rhumb line — appears as a straight line, which means a navigator can lay a ruler between two points and read off a heading. The cost is area. Greenland appears comparable to Africa and is fourteen times smaller, which is the standing criticism of the map. He coined the word atlas for a collection of maps, after the Titan, and published one from 1595. He also produced editions of Ptolemy and a chronology, and died in 1594. His projection is still the basis of almost every online map service.

• Lived: 1512 CE – 1594 CE
• Nationality: Flemish
• Roles: cartographer, geographer, mathematician