Méridián

Méridián is the Hungarian term for meridian, a great circle that passes through the North and South Poles, defining a line of longitude on the Earth's surface. Each meridian intersects the equator at a right angle and, together with its opposite meridian, forms a 180-degree half-circle. Longitudes are measured east or west from the prime meridian, which is defined as 0°. The most widely used prime meridian runs through Greenwich, England, chosen at the 1884 International Meridian Conference, which established a global standard for navigation and timekeeping. The full longitude system ranges from 0° at Greenwich to 180° east and west, with the 180th meridian approximately coinciding with the International Date Line.

In astronomy, a celestial meridian is the imaginary great circle that passes through the observer’s zenith and the celestial poles, dividing the sky into eastern and western halves; it is used to describe when astronomical objects culminate or transit.

Méridián coordinates are essential for mapmaking, navigation, and timekeeping. Local solar noon occurs when the Sun lies on the observer’s meridian. Modern geospatial technologies rely on geodetic datums such as WGS84 to define meridians on the curved surface of Earth.

The term méridián is also used in Hungarian to denote any line of longitude. The concept of meridians extends beyond Earth to other planets, where meridians are defined similarly as lines of longitude on their surfaces.