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The Washington meridians are four meridians that were used as prime meridians in the United States and pass through Washington, D.C.. The four which have been specified are: # through the Capitol # through the White House # through the old Naval Observatory # through the new Naval Observatory. Their longitudes may be reported in three ways: # relative to the local vertical used by astronomic observations # relative to NAD 27 (North American Datum 1927), an ellipsoid of revolution that is at mean sea level beneath triangulation station Meades Ranch, Kansas (not Earth-centered); # relative to NAD 83, an Earth-centered ellipsoid of revolution with dimensions chosen to best fit the undulating (±100 m) geoid (world-wide mean sea level). NAD83 longitude of the Capitol is about 1.1 arc seconds less than its NAD27 longitude; astronomic longitude there is about 4 arc seconds less than NAD83. ==Capitol meridian== Pierre (Peter) Charles L'Enfant specified the first meridian in his 1791 "''Plan of the city intended for the permanent seat of the government of the United States . . .''".〔(Pierre Charles L'Enfant's 1791 "''Plan of the city intended for the permanent seat of the government ....''" ) ''in'' (official website of the U.S. Library of Congress ). Retrieved 2008-08-13. Freedom Plaza in Northwest Washington contains an inlay of L'Enfant's Plan with a legend identifying the longitude of the Congress house as .〕〔L'Enfant identified himself as "Peter Charles L'Enfant" during most of his life, while residing in the United States. He wrote this name on his ("Plan of the city intended for the permanent seat of the government of t(he) United States ...." ) (Washington, D.C.) and on other legal documents. However, during the early 1900s, a French ambassador to the U.S., Jean Jules Jusserand, popularized the use of L'Enfant's birth name, "Pierre Charles L'Enfant". (See: Bowling, Kenneth R (2002). ''Peter Charles L'Enfant: vision, honor, and male friendship in the early American Republic.'' George Washington University, Washington, D.C.) The National Park Service identifies L'Enfant as "(Major Peter Charles L'Enfant )" and as "(Major Pierre (Peter) Charles L'Enfant )" on its website. The United States Code states in : "(a) In General.—The purposes of this chapter shall be carried out in the District of Columbia as nearly as may be practicable in harmony with the plan of Peter Charles L'Enfant."''〕 (Shortly after L'Enfant prepared this plan, its subject received the name "City of Washington".) His plan stated that the longitude of the Congress House, now called the Capitol, would be . Longitude of the center of its dome (completed in 1863 during the Civil War) is now given by the National Geodetic Survey as . 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「Washington meridian」の詳細全文を読む スポンサード リンク
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