What does longitude measure?

Longitude measures the distance east or west of the prime meridian, which is an imaginary line that runs from the North Pole to the South Pole and is designated as 0 degrees longitude. The prime meridian serves as the reference point for determining how far a location is either east or west. When you move east or west from this line, the degrees of longitude increase, eventually reaching a maximum of 180 degrees at the International Date Line.

This measurement is essential for navigation and mapping, as it allows for precise location tracking on the Earth's surface. Understanding longitude is fundamental in geographic coordinates, which pair latitude (measuring distance north or south of the equator) with longitude to pinpoint locations around the globe.