Find CRS transformation pipelines

Find candidate coordinate transformation pipelines between two coordinate reference systems. This can be used to examine which transformations are available, whether they require grid files, and what accuracy they provide.

Usage

proj_pipelines(from, to, authority="", AOI=NULL, use="NONE", 
  grid_availability="USED", desired_accuracy=-1.0, strict_containment=FALSE, 
  axis_order_authority_compliant=FALSE)

Arguments

from: character, SpatRaster, SpatVector, or any object from which crs() can extract a CRS
to: same types as for from
authority: character. Constrain output pipelines to those from this authority (e.g. "EPSG"). Default "" means no constraint
AOI: SpatExtent. Area of interest for the transformation in degrees. For an area of interest crossing the anti-meridian, west should be greater than east, e.g. ext(150, 210, 0, 30)
use: character. One of "NONE", "BOTH", "INTERSECTION", "SMALLEST", indicating how areas of interest of source and target CRS are used. Ignored when AOI is specified
grid_availability: character. One of "USED" (grid availability is used for sorting; operations with missing grids are sorted last), "DISCARD" (discard operations if a required grid is missing), "IGNORED" (ignore grid availability; results presented as if all grids were available), or "AVAILABLE" (results presented as if grids known to PROJ were available; typical when networking is enabled)
desired_accuracy: numeric. Only return pipelines with at least this accuracy (in metres). Use -1 (the default) to impose no accuracy constraint
strict_containment: logical. If FALSE (the default), permit partial matching of the area of interest. If TRUE, the area of interest must be strictly contained
axis_order_authority_compliant: logical. If FALSE (the default), always use longitude/easting for the first axis. If TRUE, follow the axis order given by the CRS definitions

Value

A data.frame with "pipelines" and the following columns:

description: human-readable description
definition: PROJ pipeline definition string
has_inverse: logical; whether the pipeline has an inverse
accuracy: accuracy in metres; -1 indicates unknown (ballpark) accuracy
grid_count: number of grids required by this pipeline
instantiable: logical; whether the pipeline can be used (all required grids are available)
from_crs: character; the CRS of the input data
to_crs: character; the CRS of the output data

Note

Requires PROJ >= 7.1 (inc" 3). See projNetwork to enable online grid downloading.

Examples

# Simple case: WGS84 to UTM zone 32Nproj_pipelines("EPSG:4326", "EPSG:32632")

# Many pipelines between NAD83/Conus Albers and WGS84
pp <- proj_pipelines("EPSG:5070", "EPSG:4326")
nrow(pp)
#> [1] 53

# Only pipelines that work without downloading grids
pp_local <- proj_pipelines("EPSG:5070", "EPSG:4326", grid_availability="DISCARD")
pp_local
#>                                                                                          description
#> 1                             Inverse of Conus Albers + NAD83 to WGS 84 (1) + axis order change (2D)
#> 2                             Inverse of Conus Albers + NAD83 to WGS 84 (3) + axis order change (2D)
#> 3                             Inverse of Conus Albers + NAD83 to WGS 84 (2) + axis order change (2D)
#> 4 Inverse of Conus Albers + Ballpark geographic offset from NAD83 to WGS 84 + axis order change (2D)
#>                                                                                                                                                                                                                                                                                                   definition
#> 1                                                                                                                                                 +proj=pipeline +step +inv +proj=aea +lat_0=23 +lon_0=-96 +lat_1=29.5 +lat_2=45.5 +x_0=0 +y_0=0 +ellps=GRS80 +step +proj=unitconvert +xy_in=rad +xy_out=deg
#> 2 +proj=pipeline +step +inv +proj=aea +lat_0=23 +lon_0=-96 +lat_1=29.5 +lat_2=45.5 +x_0=0 +y_0=0 +ellps=GRS80 +step +proj=push +v_3 +step +proj=cart +ellps=GRS80 +step +proj=helmert +x=1 +y=1 +z=-1 +step +inv +proj=cart +ellps=WGS84 +step +proj=pop +v_3 +step +proj=unitconvert +xy_in=rad +xy_out=deg
#> 3 +proj=pipeline +step +inv +proj=aea +lat_0=23 +lon_0=-96 +lat_1=29.5 +lat_2=45.5 +x_0=0 +y_0=0 +ellps=GRS80 +step +proj=push +v_3 +step +proj=cart +ellps=GRS80 +step +proj=helmert +x=-2 +y=0 +z=4 +step +inv +proj=cart +ellps=WGS84 +step +proj=pop +v_3 +step +proj=unitconvert +xy_in=rad +xy_out=deg
#> 4                                                                                                                                                 +proj=pipeline +step +inv +proj=aea +lat_0=23 +lon_0=-96 +lat_1=29.5 +lat_2=45.5 +x_0=0 +y_0=0 +ellps=GRS80 +step +proj=unitconvert +xy_in=rad +xy_out=deg
#>   has_inverse accuracy grid_count instantiable
#> 1        TRUE        4          0         TRUE
#> 2        TRUE        4          0         TRUE
#> 3        TRUE        8          0         TRUE
#> 4        TRUE       -1          0         TRUE

# Using a SpatRaster as input
r <- rast(ncols=10, nrows=10, crs="EPSG:4326")
proj_pipelines(r, "EPSG:3857")
#>                                                      description
#> 1 axis order change (2D) + Popular Visualisation Pseudo-Mercator
#>                                                                                                                       definition
#> 1 +proj=pipeline +step +proj=unitconvert +xy_in=deg +xy_out=rad +step +proj=webmerc +lat_0=0 +lon_0=0 +x_0=0 +y_0=0 +ellps=WGS84
#>   has_inverse accuracy grid_count instantiable
#> 1        TRUE        0          0         TRUE

Usage

Arguments

Value

Note

See also

Examples