Meridian Coordinates -

Located on the opposite side of the Earth from the Prime Meridian, this line marks the transition between calendar days.

In geography and navigation, meridian coordinates are the vertical components of the geographic coordinate system used to determine a precise location on Earth. NOAA's National Ocean Service (.gov) Meridians of Longitude meridian coordinates

For centuries, the lack of a standardized "zero meridian" was a logistical nightmare. Sailors and cartographers used various reference points based on their home nations; the French used Paris, the Spanish used Cadiz, and the British used Greenwich. It was not until the International Meridian Conference of 1884 that Greenwich, London, was largely adopted as the Prime Meridian (0° longitude). Located on the opposite side of the Earth