Castellón de la Plana, or simply Castellón is the capital city of the province of Castellón, in the Valencian Community, Spain. It is located in the east of the Iberian Peninsula, on the Costa del Azahar by the Mediterranean Sea. The mountain range known as Desert de les Palmes rises inland north of the town.

A prime meridian is an arbitrarily-chosen meridian in a geographic coordinate system at which longitude is defined to be 0°. Together, a prime meridian and its anti-meridian form a great circle. This great circle divides a spheroid, like Earth, into two hemispheres: the Eastern Hemisphere and the Western Hemisphere. For Earth's prime meridian, various conventions have been used or advocated in different regions throughout history. Earth's current international standard prime meridian is the IERS Reference Meridian. It is derived, but differs slightly, from the Greenwich Meridian, the previous standard.