Talk:Earth ellipsoid

Suggested merging into Reference ellipsoid.

I oppose this suggestion. This article contains information specific to the earth ellipsoid, which is easier to find than if one had to search all through the longer article. JamesBWatson (talk) 12:32, 21 December 2009 (UTC)

agreed; removing the tag, then. Fgnievinski (talk) 06:32, 24 May 2010 (UTC)

Given the overlapping data, I have no problem with merging this article with Figure of the Earth as the unique information can be logically added, and readily located with proper bolded headings that also facilitate future searches. Importantly, regardless of whether the Earth ellipsoid table is merged, or left in the current article, it should be noted the data is flawed. Both the Equatorial and Polar columns specify "axis (m)", which means the data must reflect the earth's diameter. However, it was apparently lifted from information that was called out as a radius [such as shown in the Figure of the Earth article], so a simple calculation now shows the earth's circumference to be half-sized! Gmuday1 (talk) 20:56, 14 September 2011 (UTC)

This whole area of Wiki is a mess, with much duplication of topics. For example this page Earth Ellipsoid, overlaps with [Reference ellipsoids]], Figure of the Earth, geodetic system, geographic coordinate system , Latitude, and probably many others. There could be some short term rationalising but perhaps a more thorough appraisal is need. It is clear that the table of ellipsoid definitions should appear only in one place. I would suggest putting it into Figure of the Earth.

None of the articles really bring out the distinction between purely geometrical ellipsoids and those which also model the dynamics and the gravity field. The latter are geodetic reference systems. That opens up a whole can of worms. Comments?   Peter Mercator (talk) 22:23, 11 January 2012 (UTC)

Comments?  Peter Mercator (talk) 22:23, 11 January 2012 (UTC)

Struve's measurements & calcs (published 1858)

Among the historic projects, there should be a listing of the Struve Geodetic Arc. I request that someone do this. Oaklandguy (talk) 00:20, 14 September 2017 (UTC)

Laplace and Bowditch

In Bowditch's translation of Laplace, Laplace gives a value for the ellipticity of 1/277, although Bowditch points out that his numbers give 1/250 instead. Shouldn't one of these or the related numbers be included in this table for the year 1799? — Preceding unsigned comment added by 68.232.114.38 (talk) 18:14, 23 May 2018 (UTC)

Deleted material; editorial mess; discuss merge again?

User:Qwfp deleted material important to the meaning of Earth ellipsoid, stating Additional parameters are required for a complete specification of a geodetic reference system, but that's not covered in the lead, nor should it be.. Some observations.

• I agree that the mass function wikilink was incorrect. It ought to have been something like Theoretical gravity.
• I agree that the description of the other parameters was unclear, possibly incomplete (depending on… things), and poorly written.
• I disagree that the lede should not mention that other parameters are involved in specifying the Earth ellipsoid. It should also describe them simply, and not just presume that readers are too stupid to care about them; that’s not the intent of MOS:INTRO.
• I disagree that deleting all mention of these parameters is better than improving the description.
• Much more problematically, as discussed on this page many years ago, there is no evident distinction in purpose between Earth ellipsoid and Reference ellipsoid. There is much overlapping material, and meanwhile, neither article discusses the geophysical parameters in any meaningful way. Instead, they both discuss the geometric parameters, with much problematic repetition, imprecision, and disorganization.

I suggest we rename this article to List of Earth ellipsoids, remove the body text, reorganize Reference ellipsoid, and add in any material not already there that would be removed from this article. Strebe (talk) 19:05, 3 July 2020 (UTC)

Proposed merge of Reference ellipsoid into Earth ellipsoid

wide overlap fgnievinski (talk) 01:04, 1 May 2021 (UTC)

(And I note the first related discussion has been more than a decade ago: #Suggested merging into Reference ellipsoid; good grief. fgnievinski (talk) 01:07, 1 May 2021 (UTC))

• Comment: I think that before a merger is decided, we should clarify the terminology. For example, this article justifies some of its terminology using the first citation, but that article uses "geodetic ellipsoid" for "Earth ellipsoid" and "mean ellipsoid" for "mean Earth ellipsoid". One reason for that, presumably, is that other planetary bodies can also be approximated by ellipsoids. However, a casual browse of the literature leaves me with the impression that "reference ellipsoid" is commonly used as the general term. In that case, this article should merge into Reference ellipsoid. RockMagnetist(talk) 17:13, 4 May 2021 (UTC)

• Modeling the figure of the Earth is the main motivation and application for reference ellipsoids, hence the main topic is Earth ellipsoid (or Earth's ellipsoid); other planets can be briefly discussed in a short section at the end or just mentioned with a see-also link to planetary ellipsoid. fgnievinski (talk) 05:46, 6 May 2021 (UTC)

• Comment: I feel that the geophysical literature needs to be surveyed in order to make a responsible choice here. First, “Earth's ellipsoid” would not a good choice regardless; the term of art is “Earth ellipsoid”, as the article is already named. Whether “reference ellipsoid” and “Earth ellipsoid” have the same connotations, and which one is prevalent, is something we should bring citations here to support. Strebe (talk) 18:10, 6 May 2021 (UTC)

Accepting that some would prefer more research, but that there seems to be a consistent desire for consolidation of some form, I've somewhat boldly completed the merge proposed, without prejudicing subsequent decisions to move or restructure the article.   Y Merger complete. Klbrain (talk) 09:09, 26 November 2022 (UTC)

The two articles should be kept apart, because there is a slightly different meaning. The Earth Ellipsoid may be any ellipsoid modelling something of the Earth, maybe the gravity field. The Earth ellipsoid itself is only defined by its shape (e.g. the Bessel ellipsoid or GRS80), but not by its position within Earth or its orientation.

In order to become a Reference Ellipsoid (a Geodetic Datum), the ellipsoid has to be placed somewhere in reference to the Earth.

For instance, Germany and Austria both use the Bessel ellipsoid as an Earth Ellipsoid, but placed differently. So although the Earth Ellipsoids are the same (magnitude, shape), the Geodetic Datum giving the Reference Ellipsoid is different. EinMathematikerInAustria (talk) 17:33, 29 September 2023 (UTC)

Section on meridional curvature radius is wrong

The quantity M presented in the article as the meridional curvature radius is in fact the quantity usually named N, the normal curvature radius of the first vertical (West-East direction), not in the meridional direction as claimed. So that section is wrong and misleading. EinMathematikerInAustria (talk) 17:24, 29 September 2023 (UTC)

Thanks for pointing that out. I have corrected and cited it. Strebe (talk) 22:35, 30 September 2023 (UTC)