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

[Even Rouault]

> That's exactly what I had in mind.
> 
> What's semi_major_axis in the celestial_body table used for? To me
> this is basically a default ellipsoid definition for those bodies, but
> bypassing the ellipsoid table. Maybe it makes sense to remove this
> column?

As neither WKT nor PROJ strings have an information on the body, this value is 
used by the Ellipsoid::guessBodyName() method to find a reasonable candidate 
from the semi-major axis value found in the WKT or PROJ string (it uses a 
relative error of 0.5% to decide if there is match or not. Of course that 
would fail if we have 2 bodies of same shape...).
If we have a default ellipsoid concept and a link with the body, then yes this 
column could be removed.

Even

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