Earth's Coordinate Grid

Gridding the globe with abstract lines has been put forward since the 2nd century BC, when Hipparchus suggested parallels of latitude and meridians of longitude constructed over a spherical model of Earth. Three hundred years later, Claudius Ptolemy refined these ideas and produced map projections with a graticule of longitude and latitude lines.

After the French-sponsored geodetic expeditions in Peru and Lapland in the 1730s, the ellipsoidal shape of the Earth became the basis for more accurate positioning of lines of latitude. After the International Meridian Conference of 1884 recognized the center of the transit instrument of the Royal Observatory at Greenwich, England, as the zero origin for longitude, the prime meridian, most nautical charts, and many maps agreed on the alignment of the longitude and ...