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

[Even Rouault]

Trent,

thanks, this was helpful. So the situation was that QGIS database and old 
https://svn.osgeo.org/metacrs/sr.org/srsbrowser/data/IAU2000.wkt incorrectly 
used the IAU2000_Semimajor and IAU2000_Semiminor to create a bi-axial 
ellipsoid for bodies where the three axis values where different. Which got 
fixed by 
https://github.com/USGS-Astrogeology/GDAL_scripts/blob/master/
OGC_IAU2000_WKT_v2/IAU2000_v2.wkt and what ESRI has picked up, which uses a 
sphere with IAU2000_Mean instead.

> 
> We are also working toward providing these "IAU" codes to GDAL.

You meant PROJ, right ? ;-) GDAL has no longer any CRS database now.

> Unfortunately, this will in addition to any planetary Esri codes already
> supported.

There could be several options:
- remove the ESRI definitions since the ellipsoid they define are not used by 
other objects
- do not touch the ESRI definitions, and add IAU next to it
- (more involved, would require database schema change, and likely software 
logic too to make something useful of it). Import IAU, and create a link from 
ESRI definitions to IAU ones (when identical/compatible)

Even

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