Meridian Longitude |best| May 2026

While latitude measures distance north or south of the Equator, longitude measures distance east or west of a reference line. This system allows any location on Earth to be pinpointed with exact coordinates. A meridian is an imaginary semicircle that connects the North Pole to the South Pole. Every meridian is a line of constant longitude. If you stand on any point along a given meridian, your clock time (based on the sun’s position) will be the same as anyone else on that line.

All meridians are halves of —the largest possible circles on a sphere. This means the shortest path between two points on Earth (a geodesic) often follows an arc of a meridian or intersects them at various angles. The Prime Meridian: The Starting Point For longitude to be measurable, a zero point is necessary. Today, that zero point is the Prime Meridian , which runs through the Royal Observatory in Greenwich, England . Established by international agreement in 1884, the Greenwich Meridian is designated as 0° longitude . meridian longitude

When you look at a globe, you see a grid of crisscrossing lines. The vertical lines—running from the North Pole to the South Pole—are called meridians . Together with their angular measurement, they define longitude . While latitude measures distance north or south of