sf (version 1.0-7)

st_transform: Transform or convert coordinates of simple feature

Description

Transform or convert coordinates of simple feature

Usage

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

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 or prime_meridians; see Details.

path

character; PROJ search path to be set

Details

Transforms coordinates of object to new projection. Features that cannot be transformed are returned as empty geometries.

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/541

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).

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.

See Also

Projecting simple feature geometries to projections not supported by GDAL may be done by st_transform_proj, part of package lwgeom.

sf_project projects a matrix of coordinates, bypassing GDAL altogether

Examples

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")
try(st_transform(sfc, 3857, aoi = c(-280,-90,180,90)))
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))
library(maps)
wrld <- st_as_sf(maps::map("world", fill = TRUE, plot = FALSE))
wrld_wrap <- st_wrap_dateline(wrld, options = c("WRAPDATELINE=YES", "DATELINEOFFSET=180"),
   quiet = TRUE)
wrld_moll <- st_transform(wrld_wrap, "+proj=moll")
plot(st_geometry(wrld_moll), col = "transparent")
sf_proj_info("datum")