Geographic longitude

Longitude is the angular distance between the meridian passing through a point and the prime meridian (Greenwich Meridian). Since it is an angle, it is measured in degrees, with values ranging from 0° (Greenwich Meridian) to 180° east or west. Each degree is divided into 60 minutes, and each minute into 60 seconds. Along with latitude, longitude forms the two geographic coordinates necessary to locate a point on the Earth's surface. For example, the longitude of A Coruña is 8° 23' 45'' W, and that of Barcelona is 2° 10' 35'' E. West longitude is usually expressed with the letter W, from the English word "West.".