International Terrestrial Reference Frame However, The International Meridian Conference did not take this into account. The difference between the direction of a plumb line and a line perpendicular to the surface of the ellipsoid of revolution at a particular observatory is the deflection of the vertical. A given ellipsoid would be a good compromise for measurements in a given area, such as a country or continent. Scientists proceeded to define ellipsoids of revolution. However, due to uneven distribution of the Earth‘s mass it was not possible to plumb in various locations, which if extended downward, would all pass through a single point, the centre of the Earth. During time of the conference, scientists made measurements to determine the deflection of the vertical on a large scale. The meridian chosen was that which passed through the Airy transit circle at Greenwich and it became the prime meridian. In 1884, the International Meridian Conference took place to establish an internationally recognised single meridan. The line down the middle of the map is the Greenwich meridian. This became Great Britain‘ s meridian in 1851. The final meridian was established as an imaginary line from the north pole to the south pole passing through the Airy transit circle. Through the years, the meridian was moved about 10 meters on several occasions, because transit circles with newer and better instruments were built, on each occasion next door to the existing one. In 1721, Great Britian established its meridian through an early transit circle at the newly established Royal Observatory at Greenwich. The British Meridianīefore a common meridian was established, many maritime countries began establishing their own. The French argued for a neutral line, mentioning the Azores and the Bering Strait but eventually abstained and continued to use the Paris meridian until 1911. At the International Meridian Conference held in Washington, D.C., 22 countries voted to adopt the Greenwich meridian as the prime meridian of the world. At the opposite end of the Earth, at #180^0# longitude is the meridian where east and west also meet.On October 13, 1884, Greenwich was adopted as the universal meridian, dividing the Earth into the Eastern and the Western hemisphere. Today's definition, the "Greenwich Meridian" was selected in 1884, by the International Meridian Conference in the United States, which also determined the standard of time zones used throughout the world.Įverything west of the prime meridian is called the western hemisphere, and east of it is the eastern hemisphere. It's definition has changed over time in different parts of the world. Unlike the equator, which is determined by the Earth's axis of rotation and the location of it's poles, the prime meridian is essentially arbitrarily drawn. The difference between seasons is minimal in areas near the Equator, and temperatures are generally high year round (with exceptions based on altitude). The Equator on earth is an interesting place because of the Earth's rotation. In general, equators are features of all orbiting planets, defined as "the intersection of a sphere's surface with the plane perpendicular to the sphere's axis of rotation and midway between the poles" ( Wikipedia ). The prime meridian is an imaginary line dividing the earth into East and West Hemispheres, at 0° longitude. The equator is an imaginary line dividing the earth into North and South Hemispheres, at 0° latitude.
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