[PROJ] Proj6 Docs

[Paul Ramsey]

Hi all,
I apologize for list spamming, I guess I'm just impatient to get proj6
support into PostGIS :)

I did up a little test program to try and learn more about how to do
this in the large in PostGIS, and I'm kind of confused with the many
forms "PJ" can take...

https://gist.github.com/pramsey/22127622023e88cd415cd1524db0a285

When I run the program, I get

proj_crs_get_coordinate_system: Object is not a SingleCRS
proj_cs_get_axis_count: Object is not a CoordinateSystem
axis_count = -1

So... my PJ is a full pipeline, I guess, since it came from
proj_create_crs_to_crs().
But how do I extract the first SingleSRS from the pipeline? The last?
(I'll only be doing two-system pipelines in my use case.)

Are the proj6 docs built out anywhere online? Do they address this?

P.