Longitudes are vertical map lines on the Earth, also known as meridians. They are a way to show distance from the Prime Meridian that runs through Greenwich England.
Longitude is shown as positive (+) degrees east of the Prime Meridian and negative (-) degrees west. The 180-degree longitude is the International Date Line locate opposite the Prime Meridian. Unlike latitudes that vary in length according to their placement, longitudes are all the same length meeting at the north and south poles.
Longitudes and latitudes solve the global positioning problem by providing a systematic method for giving a precise location anywhere on the Earth. Each longitude is divided into 60 minutes and each minute is divided into 60 seconds. The degree of longitude at the equator is approximately 69 miles. The degree distance varies as the longitude moves away from the equator.