Definition

The SPHEROID based upon an inve­stigation made in 1909 by Hayford, a geodesist of U.S. Coast & Geodetic Survey, using the large TRIANGULA­TION NET then existing in the U.S. A., and taking into account the inequal density of the EARTH's CRUST. The Geodetic and Geophysical Union (now the International Union of Geodesy and Geophys­ics) adopted in 1924 the Hayford's spheroid (with some slight modifica­tions) as the INTERNATIONAL ELLIPSOID OF REFERENCE.