Meridian Longitude — High Quality

A meridian is an imaginary vertical line on the Earth's surface that connects the North and South Poles. These lines are used to measure longitude, which indicates how far east or west a location is from a starting point called the Prime Meridian.  Core Concepts  What is longitude? - NOAA's National Ocean Service

A History of Desperation: The Longitude Problem

The history of meridian longitude is one of life, death, and genius. For centuries, sailors could measure latitude easily (using the North Star or the sun at noon). But longitude was a murderous puzzle. meridian longitude

While modern geodesy uses a 3D ellipsoid model (like WGS84) rather than a perfect sphere, the underlying graticule of meridian longitude remains the standard. As we map other planets—Mars, Venus, the Moon—we arbitrarily assign them a prime meridian (for Mars, it passes through the Airy-0 crater). The same logic of converging north-south lines applies across the solar system. A meridian is an imaginary vertical line on

Meridian Longitude in the Modern World: GPS and Beyond

Today, we don't need marine chronometers. The Global Positioning System (GPS) relies on a constellation of 31 satellites, each carrying atomic clocks. Your phone receives signals from at least four satellites and triangulates your position. But the underlying geometry is still meridian longitude. - NOAA's National Ocean Service A History of