[PROJ] Am I supposed to get same results with libproj if passing proj4 +proj from/to crs ?

[Sandro Santilli]

On Wed, Nov 10, 2021 at 12:48:47AM +0100, Even Rouault wrote:
> Sandro,
> 
> there is a NAD27 to WGS84 datum shift involved. So this might depend on the
> transformations registered in the PROJ database of the version you use and
> the grids available.
> 
> Result (-11708740.522541871, 3209723.515103944) is suboptimal as it is the
> you get when no grids are used
> 
> Result (-11708734.486616733, 3209717.223316072) is the one using the conus /
> us_noaa_conus.tif grid
> 
> Whether PROJ networking is enabled (PROJ_NETWORK=ON) can influence the
> result (if it is set, then the conus grid will be used even if not installed
> locally)

Thanks. I confirm moving /usr/share/proj/conus away gives me the
suboptimal result unless I set PROJ_NETWORK=ON env variable.

Now back to pyproj: the python module seems to ship with its own
libproj shared library, which does NOT find the "conus" grid.
It works fine with PROJ_NETWORK=ON but otherwise it gives the
suboptimal result.

How do I tell in which paths does such library look into,
and Which env variable (if any) would give that library instruction
as to where to look for the grids ?

--strk;