翻訳と辞書
Words near each other
・ If (Kana Nishino song)
・ If (magazine)
・ If (Mindless Self Indulgence album)
・ If (Pink Floyd song)
・ If (They Made Me a King)
・ If 2
・ If 3
・ If 4
・ If 6 Was 9
・ If 60's Was 90's
・ Ieronim Yasinsky
・ Ieronymos I of Athens
・ Ieronymos II of Athens
・ Ieropotamos
・ IERS (disambiguation)
IERS Reference Meridian
・ Ieruga River
・ Ierul Morii River
・ Ierul Rece River
・ Ierul Îngust River
・ Ierța River
・ IES
・ IES Alfonso X
・ IES Beatriz Galindo
・ IES College of Engineering
・ IES Fortuny
・ IES Group of Institutions
・ IES Jaume Vicens Vives
・ IES La Flota
・ IES Ltd


Dictionary Lists
翻訳と辞書 辞書検索 [ 開発暫定版 ]
スポンサード リンク

IERS Reference Meridian : ウィキペディア英語版
IERS Reference Meridian

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 or about at the latitude of the Royal Observatory, Greenwich.〔(History of the Prime Meridian – Past and Present )〕〔(IRM on grounds of Royal Observatory from Google Earth ) Accessed 30 March 2012〕〔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.〕 It is also the reference meridian of the Global Positioning System (GPS) operated by the United States Department of Defense, and of WGS84 and its two formal versions, the ideal International Terrestrial Reference System (ITRS) and its realization, the International Terrestrial Reference Frame (ITRF).
== Location ==
The 5.3 arcsecond 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.〔 Section 2.4.4.〕 The IRM was adopted for air navigation by the International Civil Aviation Organization on 3 March 1989.〔(WGS 84 Implementation Manual ) page i, 1998〕 Tectonic plates slowly move over the surface of the 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.
However, the IRM is not fixed to any point on Earth. Instead, all points on the European portion of the Eurasian plate, including the Royal Observatory, are slowly moving northeast about 2.5 cm per year relative to it. Thus this 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.
Universal Time is notionally based on the WGS84 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 second. Leap seconds are inserted periodically to keep UTC close to Earth's angular position relative to the Sun; see mean solar time.

抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
ウィキペディアで「IERS Reference Meridian」の詳細全文を読む



スポンサード リンク
翻訳と辞書 : 翻訳のためのインターネットリソース

Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.