The IERS Reference Meridian (IRM), also called the International Reference Meridian, is the prime meridian (0° longitude) maintained by the International Earth Rotation and Reference Systems Service (IERS). It passes about 5.3 arcseconds east of George Biddell Airy's 1851 transit circle, and thus it differs slightly from the historical Greenwich Meridian. At the latitude of the Royal Observatory, Greenwich the difference is 102 metres (335 ft).
It is the reference meridian of the Global Positioning System (GPS) operated by the United States Space Force, and of WGS 84 and its two formal versions, the ideal International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).
Location
The most important reason for the 5.3 seconds of longitude offset between the IERS Reference Meridian and the Airy transit circle is that the observations with the transit circle were based on the local vertical, while the IERS Reference is a geodetic longitude, that is, the plane of the meridian contains the center of mass of the Earth.
The International Hydrographic Organization adopted an early version of the IRM in 1983 for all nautical charts. It was adopted for air navigation by the International Civil Aviation Organization on 3 March 1989.Tectonic plates slowly move over the surface of Earth, so most countries have adopted for their maps an IRM version fixed relative to their own tectonic plate as it existed at the beginning of a specific year. Examples include the North American Datum 1983 (NAD83), the European Terrestrial Reference Frame 1989 (ETRF89), and the Geocentric Datum of Australia 1994 (GDA94). Versions fixed to a tectonic plate differ from the global version by at most a few centimetres.
The IERS system is not quite fixed to any point attached to the Earth. For example, all points on the European portion of the Eurasian plate, including the Royal Observatory, are moving northeast at about 2.5 cm per year relative to it. The IRM is the weighted average (in the least squares sense) of the reference meridians of the hundreds of ground stations contributing to the IERS network. The network includes GPS stations, satellite laser ranging (SLR) stations, lunar laser ranging (LLR) stations, and the highly accurate very long baseline interferometry (VLBI) stations. All stations' coordinates are adjusted annually to remove net rotation relative to the major tectonic plates. If earth had only two hemispherical plates moving relative to each other around any axis which intersects their centres or their junction, then the longitudes (around any other rotation axis) of any two, diametrically opposite, stations must move in opposite directions by the same amount. The 180th meridian (the meridian at 180° both east and west of the Prime Meridian) is opposite the IERS Reference Meridian and forms a great circle with it dividing the earth into Western Hemisphere and Eastern Hemisphere.
Universal Time is notionally based on the prime meridian. Because of changes in the rate of Earth's rotation, standard international time UTC can differ from the mean observed solar time at noon on the prime meridian by up to 0.9 of a second. Leap seconds are inserted from time to time, to keep UTC close to Earth's angular position relative to the Sun; see mean solar time.
List of places
Starting at the North Pole and heading south to the South Pole, the IERS Reference Meridian passes through eight countries and three oceans (Arctic Ocean, Atlantic Ocean and Southern Ocean):
See also
- 1st meridian east
- 1st meridian west
- 180th meridian
- Coordinated Universal Time
- Prime meridian
- Prime meridian (Greenwich)
References
Notes
- The astronomic latitude of the Royal Observatory is 51°28'38"N whereas its latitude on the European Terrestrial Reference Frame (1989) datum is 51°28'40.1247"N.
Citations
- Malys, Stephen; Seago, John H.; Palvis, Nikolaos K.; Seidelmann, P. Kenneth; Kaplan, George H. (1 August 2015). "Why the Greenwich meridian moved". Journal of Geodesy. 89 (12): 1263–1272. Bibcode:2015JGeod..89.1263M. doi:10.1007/s00190-015-0844-y.
- IRM on grounds of Royal Observatory from Google Earth Accessed 30 March 2012
- "A manual on the technical aspects of the United Nations Convention on the Law of the Sea – 1982" (PDF). Archived from the original (PDF) on 2008-09-10. Retrieved 2012-03-28. (4.89 MB) Section 2.4.4.
- WGS 84 Implementation Manual Archived 2008-10-03 at the Wayback Machine page i, 1998
- McCarthy, Dennis D.; Petit, Gérard, eds. (2004), "Conventional Terrestrial Reference System and Frame", IERS Conventions (2003) (Technical report), IERS Technical Note, 32, retrieved 2021-07-23
- ITU Radiocommunication Assembly (2002). "Standard-frequency and time-signal emissions" (PDF). International Telecommunication Union. Retrieved 5 February 2022.
The IERS Reference Meridian IRM also called the International Reference Meridian is the prime meridian 0 longitude maintained by the International Earth Rotation and Reference Systems Service IERS It passes about 5 3 arcseconds east of George Biddell Airy s 1851 transit circle and thus it differs slightly from the historical Greenwich Meridian At the latitude of the Royal Observatory Greenwich the difference is 102 metres 335 ft 0 class notpageimage Modern IERS Reference Meridian on Earth Countries that touch the Equator red and the Prime Meridian blue It is the reference meridian of the Global Positioning System GPS operated by the United States Space Force and of WGS 84 and its two formal versions the ideal International Terrestrial Reference System ITRS and its realization the International Terrestrial Reference Frame ITRF LocationThe most important reason for the 5 3 seconds of longitude offset between the IERS Reference Meridian and the Airy transit circle is that the observations with the transit circle were based on the local vertical while the IERS Reference is a geodetic longitude that is the plane of the meridian contains the center of mass of the Earth The International Hydrographic Organization adopted an early version of the IRM in 1983 for all nautical charts It was adopted for air navigation by the International Civil Aviation Organization on 3 March 1989 Tectonic plates slowly move over the surface of Earth so most countries have adopted for their maps an IRM version fixed relative to their own tectonic plate as it existed at the beginning of a specific year Examples include the North American Datum 1983 NAD83 the European Terrestrial Reference Frame 1989 ETRF89 and the Geocentric Datum of Australia 1994 GDA94 Versions fixed to a tectonic plate differ from the global version by at most a few centimetres The IERS system is not quite fixed to any point attached to the Earth For example all points on the European portion of the Eurasian plate including the Royal Observatory are moving northeast at about 2 5 cm per year relative to it The IRM is the weighted average in the least squares sense of the reference meridians of the hundreds of ground stations contributing to the IERS network The network includes GPS stations satellite laser ranging SLR stations lunar laser ranging LLR stations and the highly accurate very long baseline interferometry VLBI stations All stations coordinates are adjusted annually to remove net rotation relative to the major tectonic plates If earth had only two hemispherical plates moving relative to each other around any axis which intersects their centres or their junction then the longitudes around any other rotation axis of any two diametrically opposite stations must move in opposite directions by the same amount The 180th meridian the meridian at 180 both east and west of the Prime Meridian is opposite the IERS Reference Meridian and forms a great circle with it dividing the earth into Western Hemisphere and Eastern Hemisphere Universal Time is notionally based on the prime meridian Because of changes in the rate of Earth s rotation standard international time UTC can differ from the mean observed solar time at noon on the prime meridian by up to 0 9 of a second Leap seconds are inserted from time to time to keep UTC close to Earth s angular position relative to the Sun see mean solar time List of placesMap all coordinates using OpenStreetMap Download coordinates as KML GPX all coordinates GPX primary coordinates GPX secondary coordinates Starting at the North Pole and heading south to the South Pole the IERS Reference Meridian passes through eight countries and three oceans Arctic Ocean Atlantic Ocean and Southern Ocean Co ordinates approximate Country territory or sea Notes90 0 N 0 0 E 90 000 N 0 000 E 90 000 0 000 North Pole Arctic Ocean85 46 N 0 0 E 85 767 N 0 000 E 85 767 0 000 EEZ of Greenland Denmark Exclusive Economic Zone EEZ of Greenland Denmark 81 39 N 0 0 E 81 650 N 0 000 E 81 650 0 000 Greenland Sea Greenland Sea80 29 N 0 0 E 80 483 N 0 000 E 80 483 0 000 EEZ of Svalbard Norway EEZ of Svalbard Norway 76 11 N 0 0 E 76 183 N 0 000 E 76 183 0 000 International waters International waters73 44 N 0 0 E 73 733 N 0 000 E 73 733 0 000 EEZ of Jan Mayen EEZ of Jan Mayen Norway 72 53 N 0 0 E 72 883 N 0 000 E 72 883 0 000 Norwegian Sea Norwegian Sea69 7 N 0 0 E 69 117 N 0 000 E 69 117 0 000 International waters International waters64 42 N 0 0 E 64 700 N 0 000 E 64 700 0 000 EEZ of Norway EEZ of Norway63 29 N 0 0 E 63 483 N 0 000 E 63 483 0 000 EEZ of Great Britain EEZ of Great Britain61 0 N 0 0 E 61 000 N 0 000 E 61 000 0 000 North Sea North Sea53 46 N 0 0 E 53 767 N 0 000 E 53 767 0 000 United Kingdom United Kingdom From Tunstall in East Riding to Peacehaven passing through Greenwich50 47 N 0 0 E 50 783 N 0 000 E 50 783 0 000 English Channel English Channel EEZ of Great Britain50 14 N 0 0 E 50 233 N 0 000 E 50 233 0 000 EEZ of France English Channel EEZ of France49 20 N 0 0 E 49 333 N 0 000 E 49 333 0 000 France France From Villers sur Mer to Gavarnie42 41 N 0 0 E 42 683 N 0 000 E 42 683 0 000 Spain Spain From Cilindro de Marbore to Castellon de la Plana39 56 N 0 0 E 39 933 N 0 000 E 39 933 0 000 Mediterranean Sea Mediterranean Sea Gulf of Valencia EEZ of Spain38 52 N 0 0 E 38 867 N 0 000 E 38 867 0 000 Spain Spain From El Verger to Calp38 38 N 0 0 E 38 633 N 0 000 E 38 633 0 000 Mediterranean Sea Mediterranean Sea EEZ of Spain37 1 N 0 0 E 37 017 N 0 000 E 37 017 0 000 EEZ of Algeria Mediterranean Sea EEZ of Algeria35 50 N 0 0 E 35 833 N 0 000 E 35 833 0 000 Algeria Algeria From Stidia to Algeria Mali border near Bordj Badji Mokhtar21 52 N 0 0 E 21 867 N 0 000 E 21 867 0 000 Mali Mali Passing through Gao15 00 N 0 0 E 15 000 N 0 000 E 15 000 0 000 Burkina Faso Burkina Faso11 7 N 0 0 E 11 117 N 0 000 E 11 117 0 000 Togo Togo For about 600 m11 6 N 0 0 E 11 100 N 0 000 E 11 100 0 000 Ghana Ghana For about 16 km10 58 N 0 0 E 10 967 N 0 000 E 10 967 0 000 Togo Togo For about 39 km10 37 N 0 0 E 10 617 N 0 000 E 10 617 0 000 Ghana 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 7 767 0 000 Lake Volta 5 37 N 0 0 E 5 617 N 0 000 E 5 617 0 000 EEZ of Ghana in Atlantic Ocean Atlantic Ocean EEZ of Ghana1 58 N 0 0 E 1 967 N 0 000 E 1 967 0 000 International waters International waters0 0 N 0 0 E 0 000 N 0 000 E 0 000 0 000 Equator Passing through the Equator see Null Island 51 43 S 0 0 E 51 717 S 0 000 E 51 717 0 000 EEZ of Bouvet Island EEZ of Bouvet Island Norway 57 13 S 0 0 E 57 217 S 0 000 E 57 217 0 000 International waters International waters60 0 S 0 0 E 60 000 S 0 000 E 60 000 0 000 Southern Ocean Southern Ocean International waters69 36 S 0 0 E 69 600 S 0 000 E 69 600 0 000 Antarctica Antarctica Queen Maud Land claimed by Norway90 0 S 0 0 E 90 000 S 0 000 E 90 000 0 000 Amundsen Scott South Pole Station Antarctica Amundsen Scott South Pole Station United States South PoleSee also1st meridian east 1st meridian west 180th meridian Coordinated Universal Time Prime meridian Prime meridian Greenwich ReferencesNotes The astronomic latitude of the Royal Observatory is 51 28 38 N whereas its latitude on the European Terrestrial Reference Frame 1989 datum is 51 28 40 1247 N Citations Malys Stephen Seago John H Palvis Nikolaos K Seidelmann P Kenneth Kaplan George H 1 August 2015 Why the Greenwich meridian moved Journal of Geodesy 89 12 1263 1272 Bibcode 2015JGeod 89 1263M doi 10 1007 s00190 015 0844 y IRM on grounds of Royal Observatory from Google Earth Accessed 30 March 2012 A manual on the technical aspects of the United Nations Convention on the Law of the Sea 1982 PDF Archived from the original PDF on 2008 09 10 Retrieved 2012 03 28 4 89 MB Section 2 4 4 WGS 84 Implementation Manual Archived 2008 10 03 at the Wayback Machine page i 1998 McCarthy Dennis D Petit Gerard eds 2004 Conventional Terrestrial Reference System and Frame IERS Conventions 2003 Technical report IERS Technical Note 32 retrieved 2021 07 23 ITU Radiocommunication Assembly 2002 Standard frequency and time signal emissions PDF International Telecommunication Union Retrieved 5 February 2022
