Meridians Of - Longitudes

Longitude is measured in degrees, from 0° to 180° East or West. The Starting Point: The Prime Meridian

Meridians of longitude are a triumph of geometric reasoning and international cooperation. Although naturally defined as great circles converging at the poles, their numbering is purely conventional—a reminder that maps and coordinate systems are human inventions superimposed on physical reality. From Harrison’s chronometer to GPS satellites, the ability to determine longitude precisely has reshaped navigation, commerce, and global connectivity. Today, every smartphone user relies on an implicit network of reference meridians, instantaneously converting satellite signals into an east–west coordinate.

The original Airy transit circle at Greenwich (established 1851) defines the “Greenwich Meridian.” However, modern satellite navigation uses the , which is about 102 meters east of Airy’s meridian due to improved geodetic models and tectonic drift. meridians of longitudes

Coordinated Universal Time (UTC) is still based on the Prime Meridian at Greenwich. Summary Table: Longitude vs. Latitude Longitude (Meridians) Latitude (Parallels) Direction North-South (Pole to Pole) East-West (Parallel to Equator) Measures Distance East or West Distance North or South Reference Line Prime Meridian (0°) Equator (0°) Range 0° to 180° 0° to 90° Relationship Converge at the poles Always parallel

Twenty-five nations agreed to:

Here are some key characteristics of meridians of longitude:

Situated roughly along the , the International Date Line serves as the boundary where one calendar day changes to the next. Longitude is measured in degrees, from 0° to

The term comes from the Latin meridies , meaning "midday." Historically, this is because the Sun crosses a specific meridian (reaches its highest point in the sky) at the same local time for all locations along that line.