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 . . ." (see: L'Enfant Plan).<ref>(1) Freedom Plaza in Northwest Washington contains an inlay of L'Enfant's Plan with a legend identifying the longitude of the Congress house as .(2) 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, poipularized 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."</ref> (Shortly after L'Enfant prepared this plan, its subject received the name "City of Washington".) His plan stated near its right side that the longitude of the Congress house, now called the Capitol, was . L'Enfant's plan contained the following explanatory note: In order to execute the above plan, Mr. Ellicott