Mercator, Gerardus , Latin form of his real name, Gerhard Kremer [gAr'härt krA'mur] , 1512–94, Flemish geographer, mathematician, and cartographer. He studied in Louvain, where he had a geographical establishment (1534). From 1537 to 1540 he surveyed and mapped Flanders. In 1538 he produced his first map of the world (based on Ptolemy's map); in 1541 he made a terrestrial, and in 1551 a celestial, globe. He was appointed (1552) to the chair of cosmography in Duisburg. In 1554 he made a six-sheet map of Europe. The first map using the projection that bears his name appeared in 1568; it has been more generally used than any other projection for navigators' maps of the world. In 1585, Mercator began an atlas which included many of his earlier maps; the atlas was completed by his son and published in 1594. Mercator did cartographical work for Charles V and was cosmographer to the duke of Jülich and Cleves. He wrote several books on subjects such as ancient geography and the science and mathematics of geography and cartography.