[R-sig-Geo] PROJ 6 may impact workflows and packages using sf or rgdal

[Roger Bivand]

Changes introduced in PROJ 6, whether using the new proj.h API (sf) or the 
old proj_api.h API (rgdal, lwgeom) may impact R workflows and packages 
using sf or rgdal for transforming coordinate reference systems.

Because +datum= is effectively defunct, and will be gone in PROJ 7 (March 
2020), any data including CRS set correctly for previous PROJ will risk no 
longer be transformed correctly. Work is ongoing to establish how users 
can adapt to this, but it will be very risky to assume that 
transformations that worked in PROJ 4 will necessarily work as well or 
better in PROJ >= 6 without manual intervention.

Discussion is welcomed, in particular on: 
https://github.com/r-spatial/discuss/issues/28 based on 
https://github.com/r-spatial/sf/issues/1146; further analysis described in 
the workshop document on https://rsbivand.github.io/geostat19_talk/.

Please examine your workflows and packages, check whether your work is 
affected, and contribute to discussions through the issues on github. This 
list may be used, but it'll be best to keep things connected.

Roger

-- 
Roger Bivand
Department of Economics, Norwegian School of Economics,
Helleveien 30, N-5045 Bergen, Norway.
voice: +47 55 95 93 55; e-mail: Roger.Bivand using nhh.no
https://orcid.org/0000-0003-2392-6140
https://scholar.google.no/citations?user=AWeghB0AAAAJ&hl=en