[PROJ] Proj 6 API questions

[Nyall Dawson]

On Tue, 19 Mar 2019 at 15:46, Kristian Evers <kreve at sdfe.dk> wrote:
>
>
>
> On 19 Mar 2019, at 04:20, Nyall Dawson <nyall.dawson at gmail.com> wrote:
>
> On Mon, 18 Mar 2019 at 16:42, Kristian Evers <kreve at sdfe.dk> wrote:
>
> It would be interesting to see the difference between the ellipsoid tables from
> The QGIS and PROJ databases.
>
>
> Using the latest approach, the older QGIS ellipsoids I haven't been
> able to match are whittled down to:
>
> acronym/name/major/minor
>
> ['andrae','Andrae 1876 (Den., Iclnd.)', 6377104.43,6355847.415233333],
> ['CPM','Comm. des Poids et Mesures 1799',6375738.7,6356666.221912112],
> ['delmbr','Delambre 1810 (Belgium)',6376428.0,6355957.926163724],
> ['Earth2000','Earth2000',6378140.0,6356750.0],
> ['kaula','Kaula 1961',6378163.0,6356776.99208691],
> ['lerch','Lerch 1979',6378139.0,6356754.291510342],
> ['MERIT','MERIT 1983',6378137.0,6356752.298215969],
> ['mprts','Maupertius 1738',6397300.0,6363806.282722513],
> ['new_intl','New International 1967',6378157.5,6356772.2],
> ['WGS60','WGS60',6378165.0,6356783.286959437]
>
>
> Okay, that’s not too bad. Most of them are also in `proj -le`. I think only EARTH2000 and MERIT
> are unknown to PROJ today.
>
> Any clues on these?
>
>
> They can be added to the database as custom ellipsoids under the PROJ authority. The
> reason they are not there now must be because they are unused by the operations in
> the EPSG registry. Pull requests are welcome :-)

Done in https://github.com/OSGeo/proj.4/pull/1337

Now -- my final question on this topic (I hope!)

The interplanetary ellipsoid definitions in proj vary from those in
QGIS' database. E.g.

Adrastea2000
Proj: +R=8200
QGIS: +a=10000 +b=7000

Thebe2000
Proj: +R=49300
QGIS: +a=58000 +b=42000

The QGIS ones were introduced by
https://github.com/qgis/QGIS/commit/6055a4f566c16e4ae4686d5f666fa12408f2de03
- but there's no source listed there, and I cannot find where these
values were taken from, or why they differ from Proj.

Unless anyone has any clues, I'm inclined to ignore this difference
and accept proj's values as the standard used by QGIS (and if there's
any future objection the discussion can be directed to the proj
project, where it belongs).

Nyall