In geography and geodesy, a meridian is an imaginary north-south line on the Earth's surface that connects both geographic poles and is used to measure longitude. Every point on a specific meridian has the same longitude, which represents the angular distance east or west of a starting reference line known as the Prime Meridian. The Prime Meridian and Global Grid The Prime Meridian , designated as 0∘0 raised to the composed with power
longitude, is the internationally agreed-upon starting point for longitudinal measurement.
Origin: In 1884, the International Meridian Conference held in Washington, D.C., officially selected the meridian passing through the Royal Observatory in Greenwich, London, as the global standard. Hemispheres: Together with its opposite, the 180∘180 raised to the composed with power
antimeridian, the Prime Meridian divides the Earth into the Eastern and Western Hemispheres. Measurement: Longitude is measured in degrees ( ∘raised to the composed with power ), minutes ( ), and seconds ( 180∘180 raised to the composed with power East (positive values) and 180∘180 raised to the composed with power West (negative values). Physical and Geometric Characteristics
Unlike lines of latitude (parallels), which are parallel to each other, meridians have unique geometric properties: meridian longitude
Convergence: All meridians meet at the North and South Poles. This means the distance between meridians is greatest at the Equator and decreases to zero as they approach the poles.
Great Circles: Each meridian is half of a Great Circle—a circle whose center is the center of the Earth.
Equal Length: Every meridian is approximately the same length, stretching from pole to pole. Timekeeping and Navigation
Meridians are the foundational element for global timekeeping and modern navigation: In geography and geodesy, a meridian is an
The Martian Prime Meridian - Longitude “Zero” - NASA Science
A meridian is an imaginary north–south line on the Earth's surface that connects both geographic poles and is used to indicate longitude . While latitude measures distance north or south of the equator, longitude measures how far east or west a point is from a specific reference line . 1. The Prime Meridian (0° Longitude)
The Prime Meridian serves as the starting point for all longitude measurements, designated as 0° longitude . Prime Meridian, Longitude & Latitude - Britannica
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 Beyond Earth: Meridians on Other Worlds The concept
The 2025 Jeep Meridian includes "Longitude" as its entry-level trim and "Longitude Plus" as a mid-tier option.
The concept of meridian longitude is so powerful that we export it to other celestial bodies. Mars has its own Prime Meridian, passing through a small crater named Airy-0. Venus, despite its insane rotation, has a defined prime meridian. Even the Moon has a prime meridian (visible from Earth, near the "Bruce" crater).
These extraterrestrial meridians allow planetary scientists to map rover locations, plan landings, and coordinate interplanetary missions.
Directly opposite the Prime Meridian lies the Antimeridian at 180° longitude. This line is unique because it serves as the basis for the International Date Line (IDL). While the IDL zigzags to avoid cutting through countries, the 180° meridian is its geometric spine. Cross this line eastward, and you subtract a day; cross it westward, and you add a day.
While Greenwich is the global standard, other meridians hold historical or scientific importance.
| Meridian | Longitude | Significance | | :--- | :--- | :--- | | Paris Meridian | 2°20'14.03" E | Rival to Greenwich; used on French maps until 1911. | | Washington Meridian | 77°03'56.05" W | Used by US Navy before 1884. | | Puerto Rico Trench | 66° W | Deepest point in Atlantic, critical for oceanography. | | International Date Line | 180° (approx) | Demarcates calendar days. |