IERS Reference Meridian facts for kids
The IERS Reference Meridian (IRM) is like the Earth's main starting line for measuring how far east or west places are. It's also called the International Reference Meridian. Imagine a line drawn from the North Pole to the South Pole, passing through a special spot near Greenwich, England. This line is set by a group of scientists called the International Earth Rotation and Reference Systems Service (IERS).
This modern meridian is the official zero-degree longitude for many important global systems. For example, it's used by the Global Positioning System (GPS) that helps you find your way around. It's also the basis for WGS 84, which is a key system for mapping the Earth. The IERS Reference Meridian is very close to the older Greenwich Meridian, but it's slightly different. At the Royal Observatory, Greenwich, the difference is about 102 meters (335 feet).
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What is the IERS Reference Meridian?
The IERS Reference Meridian is the most accurate and up-to-date way to define the zero-degree longitude around the world. It helps everyone agree on a common starting point for maps and navigation. Think of it as the central line on a giant globe that helps us measure all other longitudes.
Why is it Important?
This special meridian is crucial for many modern technologies. It's the backbone for:
- GPS: The Global Positioning System, which uses satellites to pinpoint locations on Earth, relies on the IRM.
- Global Mapping: It's used in advanced mapping systems like WGS 84, which helps create accurate digital maps for everything from your phone to airplanes.
- International Standards: Organizations like the International Hydrographic Organization (for sea charts) and the International Civil Aviation Organization (for air travel) use the IRM to make sure everyone's maps and navigation tools are consistent.
Where is the Meridian Located?
The IERS Reference Meridian passes very close to the historic Greenwich Meridian in England. The small difference between them exists because scientists now use more advanced ways to measure Earth. The older Greenwich Meridian was based on observations from a telescope. The IERS Reference Meridian, however, uses a more modern, mathematical model of the Earth's shape. This means it considers the Earth's true center and shape, not just what can be seen from one spot.
Measuring Earth's Position
Scientists use a network of hundreds of ground stations all over the world to define the IERS Reference Meridian. These stations use different high-tech methods to measure Earth's position very precisely. Some of these methods include:
- GPS/GNSS stations: These are like super-accurate GPS receivers.
- Satellite Laser Ranging (SLR): This involves bouncing lasers off satellites.
- Lunar Laser Ranging (LLR): Similar to SLR, but bouncing lasers off the Moon!
- Very Long Baseline Interferometry (VLBI): This uses radio telescopes to observe distant cosmic objects.
All these measurements are combined and averaged to create the most accurate reference meridian possible.
How Plate Tectonics Affects Maps
Did you know that the Earth's surface is always moving? Giant pieces of the Earth's crust, called tectonic plates, slowly slide around. Because of this, the exact position of a place on Earth changes over time. To keep maps accurate, many countries use versions of the IERS Reference Meridian that are "fixed" to their own tectonic plate. This means their maps show locations relative to their own moving landmass. For example, the North American Datum 1983 (NAD83) is a system used in North America that accounts for the movement of that continent.
Time and the Meridian
The concept of Universal Time is closely linked to the prime meridian. This is because the prime meridian is the starting point for measuring longitude, which also helps us understand time zones around the world.
However, the Earth's rotation isn't perfectly steady. It can speed up or slow down very slightly. To keep our clocks in sync with the Earth's actual position relative to the Sun, scientists sometimes add a "leap second" to Coordinated Universal Time (UTC). This ensures that UTC, our international standard time, stays very close to the average solar time at the prime meridian.
Countries and Oceans Along the Meridian
The IERS Reference Meridian travels from the North Pole all the way to the South Pole. On its journey, it crosses through eight countries and three major oceans: the Arctic Ocean, the Atlantic Ocean, and the Southern Ocean.
Here's a list of the places it passes through:
| Co-ordinates (approximate) |
Country, territory or sea | Notes |
|---|---|---|
| 90°0′N 0°0′E / 90.000°N 0.000°E | Arctic Ocean | |
| 85°46′N 0°0′E / 85.767°N 0.000°E | Exclusive Economic Zone (EEZ) of Greenland (Denmark) | |
| 81°39′N 0°0′E / 81.650°N 0.000°E | Greenland Sea | |
| 80°29′N 0°0′E / 80.483°N 0.000°E | EEZ of Svalbard (Norway) | |
| 76°11′N 0°0′E / 76.183°N 0.000°E | International waters | |
| 73°44′N 0°0′E / 73.733°N 0.000°E | EEZ of Jan Mayen (Norway) | |
| 72°53′N 0°0′E / 72.883°N 0.000°E | Norwegian Sea | |
| 69°7′N 0°0′E / 69.117°N 0.000°E | International waters | |
| 64°42′N 0°0′E / 64.700°N 0.000°E | EEZ of Norway | |
| 63°29′N 0°0′E / 63.483°N 0.000°E | EEZ of Great Britain | |
| 61°0′N 0°0′E / 61.000°N 0.000°E | North Sea | |
| 53°46′N 0°0′E / 53.767°N 0.000°E |  United Kingdom |
From Tunstall, East Riding of Yorkshire to Peacehaven in East Sussex, passing through Greenwich |
| 50°47′N 0°0′E / 50.783°N 0.000°E | English Channel | EEZ of Great Britain |
| 50°14′N 0°0′E / 50.233°N 0.000°E | English Channel | EEZ of France |
| 49°20′N 0°0′E / 49.333°N 0.000°E |  France |
From Villers-sur-Mer to Gavarnie |
| 42°41′N 0°0′E / 42.683°N 0.000°E |  Spain |
From Cilindro de Marboré to Castellón de la Plana |
| 39°56′N 0°0′E / 39.933°N 0.000°E | Mediterranean Sea | Gulf of Valencia; EEZ of Spain |
| 38°52′N 0°0′E / 38.867°N 0.000°E | Spain |
From El Verger to Calp |
| 38°38′N 0°0′E / 38.633°N 0.000°E | Mediterranean Sea | EEZ of Spain |
| 37°1′N 0°0′E / 37.017°N 0.000°E | Mediterranean Sea | EEZ of Algeria |
| 35°50′N 0°0′E / 35.833°N 0.000°E |  Algeria |
From Stidia to Algeria-Mali border near Bordj Badji Mokhtar |
| 21°52′N 0°0′E / 21.867°N 0.000°E |  Mali |
Passing through Gao |
| 15°00′N 0°0′E / 15.000°N 0.000°E |  Burkina Faso |
|
| 11°7′N 0°0′E / 11.117°N 0.000°E |  Togo |
For about 600 m |
| 11°6′N 0°0′E / 11.100°N 0.000°E |  Ghana |
For about 16 km |
| 10°58′N 0°0′E / 10.967°N 0.000°E | Togo |
For about 39 km |
| 10°37′N 0°0′E / 10.617°N 0.000°E | Ghana |
From the Togo-Ghana border near Bunkpurugu to Tema Passing through Lake Volta at 7°46′N 0°0′E / 7.767°N 0.000°E |
| 5°37′N 0°0′E / 5.617°N 0.000°E | Atlantic Ocean | EEZ of Ghana |
| 1°58′N 0°0′E / 1.967°N 0.000°E | International waters | |
| 0°0′N 0°0′E / 0.000°N 0.000°E | Passing through the Equator (see Null Island) | |
| 51°43′S 0°0′E / 51.717°S 0.000°E | EEZ of Bouvet Island (Norway) | |
| 57°13′S 0°0′E / 57.217°S 0.000°E | International waters | |
| 60°0′S 0°0′E / 60.000°S 0.000°E | Southern Ocean | International waters |
| 69°36′S 0°0′E / 69.600°S 0.000°E | Antarctica | Queen Maud Land, claimed by  Norway |
| 90°0′S 0°0′E / 90.000°S 0.000°E | Antarctica | Amundsen–Scott South Pole Station,  United States South Pole |
See Also
- 1st meridian east
- 1st meridian west
- 180th meridian
- Coordinated Universal Time
- Prime meridian
- Prime meridian (Greenwich)
