[GRASS-dev] Fwd: [PROJ] PROJ 6RC2

[Even Rouault]

On samedi 23 février 2019 15:59:28 CET Markus Neteler wrote:
> Hi devs,
> 
> there is some discussion about packages that need to be patched to use
> proj_api.h or proj.h which will no longer be available in recent PROJ.
> 
> Is there anything to do in GRASS GIS (trunk)?

From what I can see in 
https://github.com/GRASS-GIS/grass-ci/blob/master/lib/proj/do_proj.c
Markus Metz made use of proj.h API of PROJ 5. This should still work with PROJ 
6.

However the way of building pipelines in
https://github.com/GRASS-GIS/grass-ci/blob/master/lib/proj/do_proj.c#L92
from the PROJ string of the source and target CRS (PROJ strings are not a good 
way to capture a CRS definition, mostly due to losing the original datum 
information) will be suboptimal in PROJ 6 since still using a early-binding 
approach with WGS84 as a pivot, instead of the new late-binding capabilities 
brought by PROJ 6.
If GRASS stores EPSG code and/or WKT in addition/instead of PROJ strings, then 
using proj_create_crs_to_crs() will lead to more accurace results in 
circumstances where WGS84 is not a natural pivot, like the case of 
NAD27+NVGD29 to NAD83+NAVD88 that Paul Ramsey exposed in
http://blog.cleverelephant.ca/2019/02/proj4-postgis.html

Even

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