[PROJ] Proj6 Docs

[Even Rouault]

> > Perhaps I should since the above explanation are probably
> > just an implementation detail for your use case ?

OK, fix just pushed.

> Yes, I’m only looking for source/target so I can figure out if I need to do
> an axis swap before (or after) feeding the transformation. Is there a
> decent way to stick a swap directing onto the end/start of the
> transformation so I get it “for free” when I run proj_trans?

That would involve hand editing the pipeline.

proj_as_proj_string(ctx, P, PJ_PROJ_5, nullptr) will return a PROJ string that 
generally begin with "+proj=pipeline" (not in your case with alternatives 
though)

If just after that and before the first +step, you insert

+step +proj=axisswap +proj=axisswap +order=2,1

(or you append it at the end if you want to reverse the order for the output)

And then you can recreate a PJ pipeline with that string with proj_create()

Or course if you do an axisswap just before/after another one, their effect 
cancels each other, so you could optimize by removing it;

Even

-- 
Spatialys - Geospatial professional services
http://www.spatialys.com