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

[Sandro Santilli]

I'm trying to obtain the *same* transformations from different
libproj versions (5.2.0 and 7.2.1) by passing the *same*
proj4 strings to the transformation, but I'm instead getting
different results.

In order to more easily test this I'm a small python script
using pyproj:

  http://strk.kbt.io/tmp/transform_test.py

The script projects coordinates 0,0 from EPSG:32040
to EPSG:3857, using the proj4 string found in 
PostGIS 3.1.4 spatial_ref_sys for those SRIDs.

On a machine (pyproj-3.2.1 using libproj-ce980207.so.22.1.1)
I'm getting these coordinates in output:

  (-11708740.522541871, 3209723.515103944)

On another machine (pyproj-2.6.1 using libproj.so.19)
I'm getting these coordinates:

  (-11708734.486616733, 3209717.223316072)

Can you think of a reason why I'd get different numbers ?
Would it be a regression for the libproj-ce980207.so.22.1.1
version to return different numbers ?

Please keep me in Cc in case of replies as I don't think I'm
receiving emails sent to this list.

--strk;

  Libre GIS consultant/developer
  https://strk.kbt.io/services.html