<P> Coordinates: 51 ° 28 ′ 40.12" N 0 ° 00 ′ 05.31" W ﻿ / ﻿ 51.4778111 ° N 0.0014750 ° W ﻿ / 51.4778111; - 0.0014750 </P> <P> A prime meridian, based at the Royal Observatory, Greenwich, in London, was established by Sir George Airy in 1851 . By 1884, over two - thirds of all ships and tonnage used it as the reference meridian on their charts and maps . In October of that year, at the behest of U.S. President Chester A. Arthur, 41 delegates from 25 nations met in Washington, D.C., United States, for the International Meridian Conference . This conference selected the meridian passing through Greenwich as the official prime meridian due to its popularity . However, France abstained from the vote, and French maps continued to use the Paris meridian for several decades . In the 18th century, London lexicographer Malachy Postlethwayt published his African maps showing the "Meridian of London" intersecting the Equator a few degrees west of the later meridian and Accra, Ghana . </P>

What longitude would you expect to see given for greenwich on a map