Cartography: from Ptolemy through a 1500 map to the Cassini triangles

The English term "cartography" is new. It came into the language in the nineteenth century from the French "cartographie", which in turn rests on the medieval Latin "carta", meaning map. Still, it is not always possible to say clearly whether an old object was a map or something else. The definition of a map is itself imprecise, so no single artefact is widely accepted as the first map. People began documenting space with cave paintings and engravings on tusks and stones.

Ionians made the oldest Greek maps of the world, among them Anaximander and Hecataeus of Miletus. Advanced geographical knowledge came before Greek colonial expansion. Cartographers used it alongside travellers' observations and a mathematical approach. Claudius Ptolemy belongs to the same current. His works describe the Baltic Sea, the coast of Gaul, Sicily and several other regions and rivers.

1500: two Americas in one drawing

The Spanish cartographer and traveller Juan de la Cosa sailed with Christopher Columbus. He created the first known cartographic rendering to show both Americas at once, as well as Africa and Eurasia. The era after 1492 is the period of the Columbian exchange, a broad flow of animals, plants, people and culture between the continents. In his 1537 treatise "Treatise in Defense of the Marine Chart", Pedro Nunes argued that parallels and meridians should be straight lines on a sea chart. He did not know how to solve the problems this causes. The situation lasted until Gerardus Mercator developed the projection named after him: conformal, cylindrical, first presented in 1569. In the eighteenth century it became the standard navigational projection, because rhumb lines are straight on it. Its drawback is the inflated size of areas far from the equator. Greenland and Antarctica look much larger than they really are.

Triangles at the command of the Sun King

Under the patronage of Louis XIV and Jean-Baptiste Colbert, members of the Académie des Sciences made many breakthrough discoveries in cartography to make their work accurate. Among the most important was the work of Giovanni Domenico Cassini, who improved the method of determining longitude by observing the motion of Jupiter's moons. Cassini, with the help and support of the mathematician Jean Picard, developed a system for joining provincial topographic data into a single map of the country, using a triangulation network.