Meridian (geography)
A line of longitude connecting points of equal longitude.
A meridian in geography and geodesy is the locus connecting points of equal longitude, forming 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, navigation
- known_for
- Line of longitude; basis for time zones and navigation
- prime_meridian
- IERS Reference Meridian (current); historically Greenwich
- etymology
- 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
with twenty-six countries present, voted to establish a single prime meridian passing through Greenwich. This was influenced by the USA already using Greenwich for its national time zone system and by 72% of world commerce depending on sea-charts using Greenwich as the Prime Meridian. The magnetic meridian is an equivalent line connecting magnetic poles, and the angle between magnetic and true meridian is magnetic declination, important for compass navigation.
Did You Know?
- The term meridian comes from Latin meridies, meaning 'midday'.
- The first prime meridian was set by Eratosthenes in 200 BCE.
More in Phantom Places & Discovery 1-24
Elsewhere in the Phantom Places & Discovery universe
Spotted an error? Know more?
This is a living reference — every entry is fact-audited, and reader corrections feed straight into our audit queue. Suggest an edit · See this site's audit record