# Geographic coordinate system

The first concept needed is called latitude (Lat, or the Greek symbol "phi", $\scriptstyle{\phi}\,\!$). For it, the Earth is cut up into 180 circles, from the Equator. The poles are at 90°, the North Pole is at 90° N(orth), the South Pole is at 90° S(outh). Places with the same latitude are on a circle, around the Earth.
The other concept is called longitude (Long, or the Greek symbol "lambda", $\scriptstyle{\lambda}\,\!$), sometimes referred to as "meridian". The 0° longitude line (or zero meridian) goes through the Royal Observatory in Greenwich. Greenwich is a part of London. Then lines are drawn in a similar way; the opposite (or "antipodal") meridian of Greenwich is considered both 180°W(est), and 180°E(ast).