st_transform: Transform or convert coordinates of simple feature

Description

Transform or convert coordinates of simple feature

Usage

st_can_transform(src, dst)
st_transform(x, crs, ...)
# S3 method for sfc
st_transform(
  x,
  crs = st_crs(x),
  ...,
  aoi = numeric(0),
  pipeline = character(0),
  reverse = FALSE,
  desired_accuracy = -1,
  allow_ballpark = TRUE,
  partial = TRUE,
  check = FALSE
)
# S3 method for sf
st_transform(x, crs = st_crs(x), ...)
# S3 method for sfg
st_transform(x, crs = st_crs(x), ...)
st_wrap_dateline(x, options, quiet)
# S3 method for sfc
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)
# S3 method for sf
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)
# S3 method for sfg
st_wrap_dateline(x, options = "WRAPDATELINE=YES", quiet = TRUE)
sf_proj_info(type = "proj", path)

Arguments

src: source crs
dst: destination crs
x: object of class sf, sfc or sfg
crs: target coordinate reference system: object of class crs, or input string for st_crs
...: ignored
aoi: area of interest, in degrees: WestLongitude, SouthLatitude, EastLongitude, NorthLatitude
pipeline: character; coordinate operation pipeline, for overriding the default operation
reverse: boolean; has only an effect when pipeline is defined: if TRUE, the inverse operation of the pipeline is applied
desired_accuracy: numeric; Only coordinate operations that offer an accuracy of at least the one specified will be considered; a negative value disables this feature (requires GDAL >= 3.3)
allow_ballpark: logical; are ballpark (low accuracy) transformations allowed? (requires GDAL >= 3.3)
partial: logical; allow for partial projection, if not all points of a geometry can be projected (corresponds to setting environment variable OGR_ENABLE_PARTIAL_REPROJECTION to TRUE)
check: logical; if TRUE, perform a sanity check on resulting polygons
options: character; should have "WRAPDATELINE=YES" to function; another parameter that is used is "DATELINEOFFSET=10" (where 10 is the default value)
quiet: logical; print options after they have been parsed?
type: character; one of have_datum_files, proj, ellps, datum, units, path, or prime_meridians; see Details.
path: character; PROJ search path to be set

Details

st_can_transform returns a boolean indicating whether coordinates with CRS src can be transformed into CRS dst

Transforms coordinates of object to new projection. Features that cannot be transformed are returned as empty geometries. Transforms using the pipeline= argument may fail if there is ambiguity in the axis order of the specified coordinate reference system; if you need the traditional GIS order, use "OGC:CRS84", not "EPSG:4326". Extra care is needed with the ESRI Shapefile format, because WKT1 does not store axis order unambiguously.

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

For a discussion of using options, see https://github.com/r-spatial/sf/issues/280 and https://github.com/r-spatial/sf/issues/1983

sf_proj_info lists the available projections, ellipses, datums, units, or data search path of the PROJ library when type is equal to proj, ellps, datum, units or path; when type equals have_datum_files a boolean is returned indicating whether datum files are installed and accessible (checking for conus). path returns the PROJ_INFO.searchpath field directly, as a single string with path separaters (: or ;).

for PROJ >= 6, sf_proj_info does not provide option type = "datums". PROJ < 6 does not provide the option type = "prime_meridians".

for PROJ >= 7.1.0, the "units" query of sf_proj_info returns the to_meter variable as numeric, previous versions return a character vector containing a numeric expression.

Examples

Run this code

p1 = st_point(c(7,52))
p2 = st_point(c(-30,20))
sfc = st_sfc(p1, p2, crs = 4326)
sfc
st_transform(sfc, 3857)
st_transform(st_sf(a=2:1, geom=sfc), "+init=epsg:3857")
if (sf_extSoftVersion()["GDAL"] >= "3.0.0") {
  st_transform(sfc, pipeline =
	  "+proj=pipeline +step +proj=axisswap +order=2,1") # reverse axes
  st_transform(sfc, pipeline =
	  "+proj=pipeline +step +proj=axisswap +order=2,1", reverse = TRUE) # also reverse axes
}
nc = st_read(system.file("shape/nc.shp", package="sf"))
st_area(nc[1,]) # area from long/lat
st_area(st_transform(nc[1,], 32119)) # NC state plane, m
st_area(st_transform(nc[1,], 2264)) # NC state plane, US foot
library(units)
set_units(st_area(st_transform(nc[1,], 2264)), m^2)
st_transform(structure(p1, proj4string = "+init=epsg:4326"), "+init=epsg:3857")
st_wrap_dateline(st_sfc(st_linestring(rbind(c(-179,0),c(179,0))), crs = 4326))
sf_proj_info("datum")

Run the code above in your browser using DataLab