# Talk:GRS 80

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What reference system did GRS80 replace? RJFJR 21:21, 21 September 2007 (UTC)

## Geodesy

Almost half this article is taken up by a definition/explanation of geodesy and the purpose of a reference ellipsoid. Given that boththese subjects have their own articles, and that this information isn't repeated for every other reference ellipsoid (WGS 84, Bessel 1841, etc), should this really be here? Wardog (talk) 13:47, 10 March 2008 (UTC)

Moving this could be a good idea. OTOH GRS80 is the de-facto standard, so this is actually a good place for this info 93.106.28.105 (talk) 13:25, 31 January 2015 (UTC)
You mean, the other way around: general stuff about any reference ellipsoid should go in reference ellipsoid. Fgnievinski (talk) 13:44, 31 January 2015 (UTC)

## Random comment

The 1980 Geodetic Reference System (GRS 80) posited a 6 378 137m semi-major axis and a 1/298.257 222 101 flattening. Actually not true: the flattening is not a defining parameter. Instead, the dynamic flattening ${\displaystyle J_{2}}$ and the rate of rotation ${\displaystyle omega}$ are, and the flattening is computed from these (a complex computation, which explains also how WGS84 ended up with different last decimals). 93.106.28.105 (talk) 13:25, 31 January 2015 (UTC)