The term comes from the Latin meridies , meaning "midday." Historically, this is because the Sun crosses a specific meridian (reaches its highest point in the sky) at the same local time for all locations along that line.
Understanding Meridians of Longitude: The Vertical Lines That Map Our World meridians of longitudes
Meridians of Longitude: Geometrical Foundations and Their Role in Global Spatial Referencing The term comes from the Latin meridies , meaning "midday
Maritime nations offered huge prizes (e.g., British Longitude Act of 1714) for a practical method. John Harrison’s marine chronometer (H4, 1761) solved it by keeping precise time from a reference meridian (Greenwich) during a sea voyage. Comparing shipboard local time (derived from solar altitude) with chronometer time gave longitude directly. meaning "midday." Historically