Transform or convert coordinates of simple features directly with Proj.4 (bypassing GDAL)

Usage

st_transform_proj(x, crs, ...)

# S3 method for sfc
st_transform_proj(x, crs, ...)

# S3 method for sf
st_transform_proj(x, crs, ...)

# S3 method for sfg
st_transform_proj(x, crs, ...)

Arguments

x: object of class sf, sfc or sfg
crs: character; target CRS, or, in case of a length 2 character vector, source and target CRS
...: ignored

Details

Transforms coordinates of object to new projection, using PROJ directly rather than the GDAL API used by st_transform.

If crs is a single CRS, it forms the target CRS, and in that case the source CRS is obtained as st_crs(x). Since this presumes that the source CRS is accepted by GDAL (which is not always the case), a second option is to specify the source and target CRS as two proj4strings in argument crs. In the latter case, st_crs(x) is ignored and may well be NA.

The st_transform_proj method for sfg objects assumes that the CRS of the object is available as an attribute of that name.

Examples

library(sf)
p1 = st_point(c(7,52))
p2 = st_point(c(-30,20))
sfc = st_sfc(p1, p2, crs = 4326)
sfc
#> Geometry set for 2 features 
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: -30 ymin: 20 xmax: 7 ymax: 52
#> Geodetic CRS:  WGS 84
#> POINT (7 52)
#> POINT (-30 20)
st_transform_proj(sfc, "+proj=wintri")
#> Geometry set for 2 features 
#> Geometry type: POINT
#> Dimension:     XY
#> Bounding box:  xmin: -3270597 ymin: 2238779 xmax: 665843 ymax: 5789966
#> Projected CRS: +proj=wintri
#> POINT (665843 5789966)
#> POINT (-3270597 2238779)
library(sf)
nc = st_read(system.file("shape/nc.shp", package="sf"))
#> Reading layer `nc' from data source 
#>   `/home/runner/work/_temp/Library/sf/shape/nc.shp' using driver `ESRI Shapefile'
#> Simple feature collection with 100 features and 14 fields
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -84.32385 ymin: 33.88199 xmax: -75.45698 ymax: 36.58965
#> Geodetic CRS:  NAD27
st_transform_proj(nc[1,], "+proj=wintri +over")
#> Simple feature collection with 1 feature and 14 fields
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -6776724 ymin: 4191803 xmax: -6736158 ymax: 4233249
#> Projected CRS: +proj=wintri +over
#>    AREA PERIMETER CNTY_ CNTY_ID NAME  FIPS FIPSNO CRESS_ID BIR74 SID74 NWBIR74
#> 1 0.114     1.442  1825    1825 Ashe 37009  37009        5  1091     1      10
#>   BIR79 SID79 NWBIR79                       geometry
#> 1  1364     0      19 MULTIPOLYGON (((-6760629 41...
st_transform_proj(structure(p1, proj4string = "+init=epsg:4326"), "+init=epsg:3857")
#> Warning: GDAL Message 1: +init=epsg:XXXX syntax is deprecated. It might return a CRS with a non-EPSG compliant axis order.
#> POINT (779236.4 6800125)