Gerhard Mercator was born in Flanders in 1512. At the dawn of the Renaissance, navigators were beginning to sail the seas in search of unknown lands. Cartographic tools were extremely rudimentary, which explains why the first maps they used were so imperfect.
Young Gerard Kremer—his real name—entered the University of Louvain at the age of 18, where the astronomer and cartographer Gemma Frisius (1508–1555) introduced him to mathematics. With the university’s approval, he secured a comfortable income by tutoring students in mathematics and selling instruments he made himself.
Investigating a map
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As early as 1537, Mercator produced a map of the Holy Land, followed the next year by a world map. In 1552, he was appointed professor of cosmography at the University of Duisburg, where he remained until his death in 1594. It was then that he produced his world map using the famous projection that now bears his name.
Mercator’s map resembles a cylindrical projection. Imagine wrapping a cylinder around the equator, with its axis aligned with the Earth’s polar axis, and projecting a point M on the Earth onto the cylinder from O, the center of the Earth. Now unroll the cylinder: what do we see? The meridians are parallel to one another, while the poles are pushed out to infinity. More precisely, if the Earth’s radius is taken as the unit of length, the y-coordinate of the image of a location at latitude θ is tan θ. Northern regions become enormous compared with those at the equator.
