[PROJ] [EXTERNAL] Re: Proj 6 API questions

[Nyall Dawson]

On Tue, 26 Mar 2019 at 17:58, Lesparre, Jochem
<Jochem.Lesparre at kadaster.nl> wrote:
>
>
> > I honestly don't have any plans to change this behavior. I cannot see
> > a way to remove this choice from users, as QGIS projects don't have a
> > single CRS, but they DO need a single ellipsoid. The best we can do is
> > make sure that a good default selection is given to users, but we
> > cannot totally remove this choice.
>
> To add a 3rd opinion in the debate: I think the ellipsoid should should NOT automatically be set to the ellipsoid of a CRS used by the user, but it should by default kept set to GRS80, unless the user explicitly manually selects another ellipsoid. GRS80 is scientifically the best ellipsoid, all others are outdated (not the most accurate estimation of the size of the earth), unconventional (seldomly used) or wrong (e.g. due to rounding of parameters). The only exception would be extra-terrestrial CRSs: there GRS80 make no sense and the scientifically best ellipsoid of the planet in question should be selected by default. When a user is using a national CRS based on a old ellipsoid, (s)he mostly doesn't want distances and areas based on this outdated ellispoid but distances and areas computed in the best way possible, which is GRS80.

I'm very much in favour of this approach!

I wonder if this is something which belongs in the proj db itself.
I.e. some API to query the recommended ellipsoid for a given planetary
body.

Nyall

>
> Kind regards, Jochem
>
>
>
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