Determining latitude at sea has always been relatively simple; sailors merely needed to measure the angle of the North Star or the midday sun above the horizon. Determining longitude, however, was the greatest scientific puzzle of the 17th and 18th centuries.
If you're interested in how this applies to specific regions, I can find the longitude of a particular city or explain how the International Date Line works in more detail. 3.2.4 Solar System Targets Observing Windows
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A meridian is an imaginary half-circle from the North Pole to the South Pole. Unlike latitude (which has a natural zero at the equator), longitude’s zero line is —chosen by people, not nature.
This is the starting point for measuring longitude, designated as 0° longitude. By international agreement, it passes through the Royal Observatory in Greenwich, London. meridian longitude
Meridian longitude is directly responsible for how we calculate time across the globe. Because the Earth rotates 360° on its axis every 24 hours, it moves through 15° of longitude every single hour (
当时，各国都悬赏巨额奖金。1714年，英国国会更是通过了著名的“经度法案”，悬赏高达（相当于现在数百万美元）的奖金。
This article will dissect everything you need to know about meridian longitude: its definition, its history, how it differs from latitude, why the Prime Meridian matters, and how modern technology revolutionizes our use of these ancient lines.
If you encounter coordinates, here is the standard format: . Determining latitude at sea has always been relatively
This line became known as the , designated as 0° longitude .
Meridians and longitude provide a fundamental framework for locating positions on Earth. Accurate use requires clear datum/reference, awareness of measurement methods and potential errors, and appropriate map projections for practical applications.
Telescopes must track objects across the sky using coordinates that include hour angles derived from longitude. Similarly, space agencies choose launch sites near the equator (low latitude) but must calculate the Earth’s rotational velocity—which varies by longitude—to slingshot rockets into orbit efficiently.
While we no longer rely on paper charts and mechanical marine chronometers to cross the oceans, meridians of longitude remain deeply embedded in modern technology. This is the starting point for measuring longitude,
is a geographic coordinate that specifies the east‑west position of a point on Earth’s surface. It is measured as an angle from the prime meridian (0° longitude) to the meridian passing through the point, ranging from 0° to 180° east or west.
Unlike the Equator—which is naturally fixed by the Earth's rotation—there is no natural physical marker for 0∘0 raised to the composed with power
Every meridian runs directly north and south.
Today, the meridian longitude remains as relevant as ever, though its application has evolved. Global Positioning Systems (GPS) use a "Reference Meridian" that differs slightly from the physical line at Greenwich due to shifts in tectonic plates and more precise satellite measurements. From the flight paths of commercial airliners to the data packets traveling through undersea fiber-optic cables, our entire global infrastructure relies on the mathematical certainty of these vertical lines. The meridian longitude is more than just a map coordinate; it is the universal language of space and time that connects every corner of the globe.
By providing a comprehensive overview of meridian longitude, we hope to have equipped you with a deeper understanding of this essential geographic concept.