Editing Earth radius (section)

===Arithmetic mean radius===
[[File:WGS84_mean_Earth_radius.svg|thumb|Equatorial (''a''), polar (''b'') and arithmetic mean Earth radii as defined in the 1984 [[World Geodetic System]] revision (not to scale)]]

In geophysics, the [[International Union of Geodesy and Geophysics]] (IUGG) defines the ''Earth's [[arithmetic mean]] radius'' (denoted {{math|''R''<sub>1</sub>}}) to be<ref name="Moritz">Moritz, H. (1980). [https://geodesy.geology.ohio-state.edu/course/refpapers/00740128.pdf ''Geodetic Reference System 1980''] {{Webarchive|url=https://web.archive.org/web/20160220054607/https://geodesy.geology.ohio-state.edu/course/refpapers/00740128.pdf |date=2016-02-20 }}, by resolution of the XVII General Assembly of the IUGG in Canberra.</ref>
:<math>R_1 = \frac{2a+b}{3}.</math>
The factor of two accounts for the biaxial symmetry in Earth's spheroid, a specialization of triaxial ellipsoid.<ref name="Moritz2000">{{cite journal |last=Moritz |first=H. |date=March 2000 |title=Geodetic Reference System 1980 |journal=Journal of Geodesy |volume=74 |issue=1 |pages=128–133 |doi=10.1007/s001900050278 |bibcode = 2000JGeod..74..128. |s2cid=195290884 }}</ref>
For Earth, the arithmetic mean radius is published by IUGG and [[National Geospatial-Intelligence Agency|NGA]] as {{convert|6371.0087714|km|mi|abbr=on}}.<ref name="IAU XXIX"/><ref name="NGA"/>