From PROJ 7 (and partly 7.1), it is becoming possible to use transformation grids downloaded on demand to improve coordinate operation accuracy from a content download network (CDN). These functions report on and control the use of the CDN.
is_proj_CDN_enabled() enable_proj_CDN() disable_proj_CDN() proj_CDN_user_writable_dir() get_proj_search_paths() set_proj_search_paths(paths)
a character vector of existing directories
The PROJ user-writable CDN directory is set as soon as the internal search path is queried, and for most uses, the default value will allow all programs using PROJ such as R packages, QGIS, GRASS, etc., to access any downloaded grids. Grids are checked for staleness at regular intervals. This directory may be set to a non-default value with the PROJ_USER_WRITABLE_DIRECTORY environment variable before rgdal (and any other package using PROJ) is loaded and attached, from PROJ >= 7.1.0.
Logical values and/or character vector search paths, often NULL for earlier versions of PROJ.
is_proj_CDN_enabled() #>  FALSE proj_CDN_user_writable_dir() #>  "/home/rsb/.local/share/proj" get_proj_search_paths() #>  "/home/rsb/.local/share/proj" "/usr/local/share/proj" #>  "/usr/local/share/proj"