The Hayford ellipsoid is a
geodetic reference ellipsoid
An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations ...
, named after the US
geodesist
Geodesy ( ) is the Earth science of accurately measuring and understanding Earth's figure (geometric shape and size), orientation in space, and gravity. The field also incorporates studies of how these properties change over time and equival ...
John Fillmore Hayford
John Fillmore Hayford (May 19, 1868 – March 10, 1925) was an eminent United States geodesist. His work involved the study of isostasy and the construction of a reference ellipsoid for approximating the figure of the Earth. The crater Hayford on ...
(1868–1925), which was introduced in 1910. The Hayford ellipsoid was also referred to as the International ellipsoid 1924 after it had been adopted by the
International Union of Geodesy and Geophysics IUGG in 1924, and was recommended for use all over the world. Many countries retained their previous ellipsoids.
The Hayford ellipsoid is defined by its
semi-major axis
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis (major semiaxis) is the lon ...
= and its
flattening
Flattening is a measure of the compression of a circle or sphere along a diameter to form an ellipse or an ellipsoid of revolution ( spheroid) respectively. Other terms used are ellipticity, or oblateness. The usual notation for flattening ...
= 1:297.00. Unlike some of its predecessors, such as the
Bessel ellipsoid
The Bessel ellipsoid (or Bessel 1841) is an important reference ellipsoid of geodesy. It is currently used by several countries for their national geodetic surveys, but will be replaced in the next decades by modern ellipsoids of satellite geode ...
( = , = 1:299.15), which was a European ellipsoid, the Hayford ellipsoid also included measurements from
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
, as well as other continents (to a lesser extent). It also included
isostatic measurements to reduce
plumbline divergences. Hayfords ellipsoid did not reach the accuracy of
Helmerts ellipsoid published 1906 ( = , = 1:298.3).
It has since been replaced as the "International ellipsoid" by the newer
Lucerne ellipsoid
, neighboring_municipalities= Adligenswil, Ebikon, Emmen, Horw, Kriens, Malters, Meggen, Neuenkirch
Lucerne ( , ; High Alemannic: ''Lozärn'') or Luzern ()Other languages: gsw, Lozärn, label= Lucerne German; it, Lucerna ; rm, Lucerna . is ...
(1967) and
GRS 80
The Geodetic Reference System 1980 (GRS 80) is a geodetic reference system consisting of a global reference ellipsoid and a normal gravity model.
Background
Geodesy is the scientific discipline that deals with the measurement and representation ...
(1980).
See also
*
Earth ellipsoid
An Earth ellipsoid or Earth spheroid is a mathematical figure approximating the Earth's form, used as a reference frame for computations in geodesy, astronomy, and the geosciences. Various different ellipsoids have been used as approximations ...
Sources
*
Defense Mapping Agency
The National Geospatial-Intelligence Agency (NGA) is a combat support agency within the United States Department of Defense whose primary mission is collecting, analyzing, and distributing geospatial intelligence (GEOINT) in support of nationa ...
: ''Geodesy for the layman'', 1983, p.
Geodesy
Geophysics
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