If you have ever seen a map of the world in a classroom or in an atlas, chances are you have seen the work of Gerardus Mercator, a 16th-century Flemish cartographer (mapmaker). His most famous work, the Mercator projection, is a geographical chart where the spherical globe is flattened into a two-dimensional map, with latitude and longitude lines drawn in a straight grid. Mercator’s view of the world is one that has endured through the centuries and still helps navigators today.

Mercator was born in Flanders (located in modern-day Belgium) in 1512. The son of a cobbler, Mercator grew up in a poor family. He graduated from the University of Louvain in 1532, where he studied mathematics, geography, and astronomy. After graduating, Mercator developed his skills as an engraver, calligrapher, and geographer, and then began making globes and scientific instruments. As his reputation grew, Mercator published several maps of places around the world. These included an early version of his world map, which showed the globe as a heart-shaped projection.

He continued studying the sciences and making maps and instruments for wealthy, and sometimes high-profile, clients. But in 1544, Mercator was arrested under suspicion of heresy; the traveling he did for research had made church officials wary. After spending a few months in prison, he was released and continued his studies.

In 1569, Mercator published his epic world map. This map, with its Mercator projection, was designed to help sailors navigate around the globe. They could use latitude and longitude lines to plot a straight route. Mercator’s projection laid out the globe as a flattened version of a cylinder. All the latitude and longitude lines intersected at 90-degree angles. Because the projection was intended to be a reference for navigation and not land geography, the landmasses on the map are not necessarily proportional to their actual size; at higher latitudes, landmasses appear larger than their actual size. Despite these distortions, Mercator’s projection is still heavily used today.

In addition to publishing his famous projection, Mercator was the pioneer of another geographical tool we use to this day. He coined the term “atlas” (named after the Greek mythological figure who held the world on his shoulders) to describe a collection of maps. Mercator continued his cartography work for the rest of his life, publishing parts of his atlas until his death in 1594.