Longitude Longitude is a geographical coordinate that represents the measurement east or west of the prime meridian – the meridian that runs through Greenwich, England. It is an angular measurement usually expressed in degrees. Lines of longitude are depicted as circles around the earth passing through the Poles. These lines run around the earth vertically (up and down) and meet at the North and South Poles. Each line, or meridian, measures one arc degree of longitude. The line of longitude passing through the prime meridian is internationally accepted as the line of 0° of longitude, while the antemeridian, halfway around the world, measures 180°, Philadelphia measures 75°W and Tokyo measures 140°E.
