1) Lines of latitude and longitude allow us to accurately describe locations on Earth. Lines of latitude run east-west and indicate how far north or south a place is from the equator, while lines of longitude run north-south and indicate how far east or west a place is from the prime meridian. 2) The prime meridian passes through Greenwich, England and is defined as 0° longitude. Longitude lines are numbered up to 180° east and west of the prime meridian. 3) To write the latitude and longitude coordinates of a location, write the latitude value first, followed by the longitude value. For example, the coordinates of Madrid are 40° 26' N 3° 42' W.