Transform or convert coordinates of simple feature
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)source crs
destination crs
object of class sf, sfc or sfg
target coordinate reference system: object of class `crs`, or input string for st_crs
ignored
area of interest, in degrees: WestLongitude, SouthLatitude, EastLongitude, NorthLatitude
character; coordinate operation pipeline, for overriding the default operation
boolean; has only an effect when pipeline is defined:
if TRUE, the inverse operation of the pipeline is applied
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)
logical; are ballpark (low accuracy) transformations allowed? (requires GDAL >= 3.3)
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)
logical; if TRUE, perform a sanity check on resulting polygons
character; should have "WRAPDATELINE=YES" to function; another parameter that is used is "DATELINEOFFSET=10" (where 10 is the default value)
logical; print options after they have been parsed?
character; one of have_datum_files, proj, ellps, datum, units or prime_meridians; see Details.
character; PROJ search path to be set
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 unambigiously.
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).
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.
st_transform_proj, part of package lwgeom.
sf_project projects a matrix of coordinates, bypassing GDAL altogether
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(sfc, 3857)
#> Geometry set for 2 features
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: -3339585 ymin: 2273031 xmax: 779236.4 ymax: 6800125
#> Projected CRS: WGS 84 / Pseudo-Mercator
#> POINT (779236.4 6800125)
#> POINT (-3339585 2273031)
st_transform(st_sf(a=2:1, geom=sfc), "+init=epsg:3857")
#> Simple feature collection with 2 features and 1 field
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: -3339585 ymin: 2273031 xmax: 779236.4 ymax: 6800125
#> Projected CRS: WGS 84 / Pseudo-Mercator
#> a geom
#> 1 2 POINT (779236.4 6800125)
#> 2 1 POINT (-3339585 2273031)
try(st_transform(sfc, 3857, aoi = c(-280,-90,180,90)))
#> Warning: GDAL Error 1: Invalid dfWestLongitudeDeg
#> Error : values for area of interest not accepted
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
}
#> Geometry set for 2 features
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: -30 ymin: 20 xmax: 7 ymax: 52
#> CRS: NA
#> POINT (7 52)
#> POINT (-30 20)
nc = st_read(system.file("shape/nc.shp", package="sf"))
#> Reading layer `nc' from data source
#> `/tmp/RtmpxmZ5jE/temp_libpathf41261b39098/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_area(nc[1,]) # area from long/lat
#> 1137107793 [m^2]
st_area(st_transform(nc[1,], 32119)) # NC state plane, m
#> 1137598162 [m^2]
st_area(st_transform(nc[1,], 2264)) # NC state plane, US foot
#> 12244955726 [US_survey_foot^2]
library(units)
#> udunits database from /usr/share/xml/udunits/udunits2.xml
set_units(st_area(st_transform(nc[1,], 2264)), m^2)
#> 1137598162 [m^2]
st_transform(structure(p1, proj4string = "+init=epsg:4326"), "+init=epsg:3857")
#> POINT (779236.4 6800125)
st_wrap_dateline(st_sfc(st_linestring(rbind(c(-179,0),c(179,0))), crs = 4326))
#> Geometry set for 1 feature
#> Geometry type: MULTILINESTRING
#> Dimension: XY
#> Bounding box: xmin: -180 ymin: 0 xmax: 180 ymax: 0
#> Geodetic CRS: WGS 84
#> MULTILINESTRING ((-179 0, -180 0), (180 0, 179 0))
sf_proj_info("datum")
#> data frame with 0 columns and 0 rows