[PROJ] How does proj deal with ellipsoid with respect to reprojection

[Even Rouault]

Brendan,

> Or does the fact
> that my source and target ellipse/datum are the same mean the gnomonic
> projection has the WGS4 coordinates passed directly to it?

Yes, given that the source and target datums are the same, no change in geographic 
coordinate is done.

And given that the implementation of gnomonic is for a sphere only, the flattening 
of WGS84 is ignored. So you'll get the same result as if it was a sphere of radius 
6378137 metres

Even

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