Changelog

deprecation of project(), CRSargs(), asSGDF_GROD(), readGDAL(), writeGDAL(), create2GDAL(), showWKT(), showEPSG(), readOGR(), ogrFIDs(), ogrInfo(), ogrDrivers(), writeOGR(), ogrListLayers(), GDALinfo(), print.GDALobj(), GDALcall(), rawTransform(), OGRSpatialRef() in favour of functions and methods ib sf and terra.
handle -Wstrict-prototypes int main() to int main(void) in configure.ac
update src/Makevars.ucrt to upgraded MXE geospatial libraries
address https://github.com/r-spatial/sf/pull/2009 in src/Makevars.ucrt
set PROJ4 warnings default to “none”
fix -Wstrict-prototypes warnings in code

update src/Makefile.ucrt to accommodate the GDAL raster Geospatial PDF driver for reading

restore PROJ path assignment for PROJ >= 6 not using PROJ_LIB (was used for PROJ 6 but not > 6) https://github.com/rsbivand/rgrass/issues/52
Update src/Makevars.win to GDAL 3.4.1 for R < 4.2 https://github.com/r-spatial/sf/pull/1919

also convert BOUNDCRS to PROJCRS by default in OGRSpatialRef() and getProjectionRef()
test for chunks table in cache.db in vignette
quietening tests only differing by proj.db version.

Add environment variable access to –with-data-copy by PROJ_GDAL_DATA_COPY (https://github.com/r-spatial/sf/issues/1605)
Adaptations for PROJ 8.
Handle mixed 2D/3D in readOGR(): (https://github.com/r-spatial/sf/issues/1683)
Add tweak for UCRT builds.
Thin examples for spTransform().

Attempt to remove further valgrind leak in proj6.cpp: PROJcopyEPSG() and in ogr_proj.cpp, both wrongly placed object destructors.
Modified roundtripping all declared projections in ?project examples because some listed projections for PROJ >= 5 provoke valgrind leakages by returning very large out-of-scope values for input coordinates (0, 0); inversion of these is not attempted; some listed projections are not projections.

Suggest rgeos to write pre-SFS multipolygon objects to avoid unpleasant workaround.
Try to eliminate current valgrind leaks, starting from (https://github.com/r-spatial/gstat/issues/82).
Try to increase robustness to installation with early PROJ 6 versions, which often lack functionality found necessary later (for example visualization order); the code had assumed that this function always was available and behaved as it now does. There are now graceful failures when not available.

Dan Baston: raster speedups
PROJ 7.2.1 includes a bug-fix for +proj=ob_tran cases that required changes in detection and handling of target/source CRS reversal, https://lists.osgeo.org/pipermail/proj/2020-December/009999.html

condition tests/test_enforce_xy.R on PROJ >= 6 and GDAL >= 3 (email BDR, I forgot to re-check with PROJ-5.2.0/GDAL-2.2.4).
Adaptation to EPSG 10 database format started (from PROJ 7.2); choose DB columns by name not number in vignette.

"CRS" instantiation now prefers PROJ: use rgdal::set_prefer_proj(FALSE) to return to earlier behaviour. It seems that access from C/C++ code to mechanisms in PROJ offers more depth than going through GDAL to PROJ. This "CRS" instantiation in sp and raster; Proj4 and WKT2 strings may differ depending on whether instantiation is straight from PROJ or goes via GDAL. Confirmed with multiple reverse dependency checks over almost 900 CRAN packages.
By default use PROJ function to extract the source CRS from a "BOUNDCRS". When +towgs84= is given, PROJ and GDAL see the apparent source Proj4 string as implicitly implying a coordinate operation transforming to target WGS84, leading to the WKT2 representation being a "BOUNDCRS", not a "PROJCRS" or "GEOGCRS", and thus causing misunderstandings later in searching for the most accurate coordinate operation for a transformation. May be controlled by setting the get_source_if_boundcrs= in sp::CRS() from sp 1.4-4 (2020-10-07). Confirmed with multiple reverse dependency checks over almost 900 CRAN packages.
Add support for instantiating from "OGC:CRS84" to provide a guaranteed GIS/visualization axis order WGS84 instantiator (preferred to "EPSG:4326").
Permit empty string in SRS_string= argument to sp::CRS() and functions called by it.
Use GDAL ORSIsProjected() instead of simply looking for "+proj=longlat" in the Proj4 string representation where possible.

Typo in C code; use try() around Area-of-Interest calculation for coordinate operations (email BDR, I forgot to re-check with PROJ-5.2.0/GDAL-2.2.4).

Add support for instantiating from "ESRI:".
Add Area-of-Interest to coordinate operation search (reduces the number of candidates found in many cases), and use in rgdal::spTransform() by default (use_aoi=FALSE to suppress); illustrate in vignette https://cran.r-project.org/web/packages/rgdal/vignettes/CRS_projections_transformations.html.
Harden to condition on PROJ functions only available from 6.2.0; block "+proj=ob_tran tests for PROJ 6.0.0-6.1.1.
Support PROJ CDN https://cdn.proj.org for on-demand download of transformation grids if requested by user; document in vignette https://cran.r-project.org/web/packages/rgdal/vignettes/CRS_projections_transformations.html.

Released to match sp 1.4.0 (2020-02-21) to 1.4-2 (2020-05-20) following months of development adapting to breaking changes in the external libraries used here: PROJ and GDAL; see also https://cran.r-project.org/web/packages/sp/news.html.
Expose options("rgdal_show_exportToProj4_warnings"="none") to mute Proj4 string degradation warnings.
Add new vignette https://cran.r-project.org/web/packages/rgdal/vignettes/CRS_projections_transformations.html.
CRAN Windows binary uses PROJ >= 6 and GDAL >= 3
Add PROJ-based CRS comparison: compare_CRS().
project() and spTransform() use WKT2 comment if available, fallback to Proj4 representation if not.
List coordinate operations (based on pyproj code): list_coordOps().
Add enforce_xy= arguments to try to ensure that only GIS/visualization axis order is present.
Add "CRS" object comment carrying WKT2 (2019) multiline string representation on read operations.
Use "CRS" object comment carrying WKT2 (2019) multiline string representation on write operations.

Version 1.6-4 (development, rev. 1188-)