[PROJ] Proj6 Docs

[Even Rouault]

> > If just after that and before the first +step, you insert
> > 
> > +step +proj=axisswap +proj=axisswap +order=2,1
> 
> twice?

For example if you transform from EPSG:4326 to something, as PROJ internally 
handles geodetic coordinates in the long, lat order, the pipeline it will 
return will do as a first step an axis inversion from lat, long (the axis 
order of EPSG:4326) to long, lat.
If you actually want to create a pipeline that takes long, lat coordinates, 
you'd have to add an extra axisswap before, or remove the axisswap PROJ 
automatically added.

> 
> Unfortunately, running proj_as_proj_string() on my transform
> <https://gist.github.com/pramsey/22127622023e88cd415cd1524db0a285#file-proj
> -c-L19
> <https://gist.github.com/pramsey/22127622023e88cd415cd1524db0a285#file-proj
> -c-L19>> results in
> 
>   proj_as_proj_string: Object type not exportable to PROJ

Yes, that's what I meant with my above "(not in your case with
alternatives though)". As there are several potential alternatives, the PJ 
object you get cannot be exported as a PROJ string, since the actal PROJ 
string will change depending on the coordinates with which you'll call 
proj_trans()

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