Meridian (geography)
A meridian is a line of longitude connecting the poles.
A meridian in geography and geodesy is the locus connecting points of equal longitude, serving as a coordinate line for longitudes. On a spherical Earth model, a meridian is a great semicircle; on an ellipsoidal model, it is half of a north-south great ellipse.
- field
- Geography, geodesy
- known_for
- Line of longitude; basis for time zones and navigation
- etymology
- From Latin meridies, meaning 'midday'
Lore & Background
The term meridian comes from the Latin meridies, meaning 'midday'; the subsolar point passes through a given meridian at solar noon. The same Latin stem gives rise to a.m. (ante meridiem) and p.m. (post meridiem). The first prime meridian was set by Eratosthenes in 200 BCE, but had problems due to lack of latitude measurement. By the early modern era, multiple locations were used as prime meridians, with Paris and Greenwich being most often acknowledged.
Reader's Guide
The meridian is fundamental to global navigation, timekeeping, and mapping. The concept of the meridian also underlies the magnetic meridian (used with compasses) and the true meridian (found by astronomical observations). Standard meridians, such as the 30th meridian east for Eastern European Time, are used to determine standard time zones, though some countries use offsets of 30 or 45 minutes. Navigators historically used the Sun's altitude at local meridian passage to calculate latitude.
Did You Know?
- The term 'meridian' comes from the Latin 'meridies', meaning 'midday'.
Frequently Asked Questions
Who is Meridian (geography)?
A meridian is an imaginary line of longitude that links Earth's two poles, forming the structural backbone of our global coordinate system. In geodesy it represents every point that shares the same longitude value.
What are Meridian (geography)'s powers/role?
Meridians slice the globe into longitudinal segments and serve as the foundation for time-zone boundaries and maritime navigation. On a spherical Earth model each one traces a great semicircle, while on the WGS 84 ellipsoid it becomes half of a north-south great ellipse.
Where does Meridian (geography)'s name come from?
The term descends from the Latin word 'meridies,' meaning midday, because the sun peaks directly overhead when it crosses a given meridian. This etymology ties the line directly to its earliest practical use in solar timekeeping.
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