GDAL version, supported file formats, cache size, and PROJ coordinate transformation control

Set the GDAL warning level or get a data.frame with the available GDAL drivers (file formats), or, if warn=NA and drivers=FALSE, you get the version numbers of one or all of the GDAL, PROJ and GEOS libraries.

GDAL is the software library that terra builds on to read and write spatial data and for some raster data processing. PROJ is used for transformation of coordinates ("projection") and GEOS is used for geometric operations with vector data.

The current GDAL configuration options and obtained with getGDALconfig and changed with setGDALconfig.

proj_ok checks if the PROJ database with CRS definitions can be found.

projNetwork controls whether PROJ can access network resources for coordinate transformations. By default, network access is enabled to provide high-accuracy grid-based datum transformations where available. When disabled, PROJ falls back to "ballpark transformations" (of unknown accuracy) which could lead to errors of hundreds of meters in some cases. When enabled, PROJ downloads transformation grids from https://cdn.proj.org, requiring network connectivity and valid SSL certificates. After a successful run, the files are cached locally.

projPaths gets or sets the search paths that PROJ uses to find coordinate system definitions and transformation grids. This allows users to specify custom locations for PROJ data files, such as when using offline installations or custom grid files. By default, it operates on PROJ search paths, but can also set GDAL search paths when with_proj=FALSE.

Usage

gdal(warn=NA, drivers=FALSE, ...)
gdalCache(size=NA)
setGDALconfig(option, value="")
getGDALconfig(option)
clearVSIcache()
libVersion(lib="all", parse=FALSE)
unloadGDALdrivers(x)
proj_ok()
projNetwork(enable, url="")
projPaths(paths, with_proj = TRUE)

Arguments

warn: If NA and drivers=FALSE, the version of the library specified by lib is returned. Otherwise, the value should be an integer between 1 and 4 representing the level of GDAL warnings and errors that are passed to R. 1 = warnings and errors; 2 = errors only (recoverable errors as a warning); 3 = irrecoverable errors only; 4 = ignore all errors and warnings. The default setting is 2
drivers: logical. If TRUE a data.frame with the raster and vector data formats that are available.
...: additional arguments (for backwards compatibility only)
size: numeric. The new cache size in MB
option: character. GDAL configuration option name, or a "name=value" string (in which case the value argument is ignored
value: character. value for GDAL configuration option. Use "" to reset it to its default value
lib: character. "gdal", "proj", or "geos", or any other value to get the versions numbers of all three
parse: logical. Should the version be parsed into three numerical values (major, minor and sub versions)?
x: character. Drivers names such as "GTiff" to be unloaded. Or "" to reload all drivers
enable: logical. If TRUE, enable PROJ network access for high-accuracy grid-based transformations. If FALSE, disable network access and use ballpark transformations. If missing, return the current network status
url: character. Optional URL for PROJ network endpoint. If empty string (default), uses PROJ's default network settings (https://cdn.proj.org)
paths: character. Vector of file paths to directories containing PROJ data files. If missing, returns the current search paths
with_proj: logical. If TRUE (default), set PROJ search paths. If FALSE, set GDAL search paths

Value

character vector of search paths. When setting paths, the result is returned invisibly.

Note

While some spatial analyses may not be greatly affected by PROJ network settings (ballpark vs. grid-based transformations), the differences can be significant, especially when a transformation involves a shift in datum between different coordinate reference systems. For applications requiring high positional accuracy, ensure network access is enabled or grids are locally available. Grids can be pre-downloaded using the projsync utility or installed via system packages, such as proj-data on Ubuntu/Debian systems. Downloaded grids are cached locally and then reused for subsequent transformations.

Examples