Coordinate Systems and Map Datums

The geographic coordinate system locates any point on Earth using latitude, the angular distance north or south of the equator, and longitude, the angular distance east or west of an agreed reference meridian. That reference meridian was itself the subject of international negotiation: at the International Meridian Conference held in Washington, D.C., in October 1884, delegates from twenty-five nations voted to adopt the meridian passing through the Royal Observatory at Greenwich, England, as the universal prime meridian of zero degrees longitude, a choice reflecting Greenwich's already dominant role in international maritime navigation and timekeeping, though the delegation from Santo Domingo, in the present-day Dominican Republic, voted against the resolution, and France and Brazil abstained.