Retrieve coordinate reference system from sf or sfc object

Source: R/st_crs2.R

This function is a wrapper for sf::st_crs, unless threating numeric character strings as integers, and accepting also UTM timezones, paths of spatial files and paths of text files containing WKT like .prj (see details) .

st_crs2(x, ...)

Arguments

x

numeric, character, or object of class sf or sfc, being:

  • EPSG code: numeric (e.g. 32632) or character (in the form "32632" or "EPSG:32632");

  • UTM zone: numeric (e.g. 32, interpreted as 32 North) or character (e.g. "32" or "32N" for zone 32 North, "32S" for 32 South);

  • WKT test: passed as character string or as path of a text file containing it (e.g. the path of a .prj file);

  • PROJ.4 string, passed as character (e.g. "+proj=utm +zone=32 +datum=WGS84 +units=m +no_defs" (NOTE: this representation is deprecated with PROJ >= 6 -- see http://rgdal.r-forge.r-project.org/articles/PROJ6_GDAL3.html -- so a warning is returned using it, unless the string contains only the epsg code -- e.g. "+init=epsg:32632", in which case the EPSG code is taken);

  • path of a spatial file (managed by sf::st_read or stars::read_stars), passed as character string of length 1;

  • spatial file of class sf or sfc.

...

other parameters passed to sf::st_crs.

Value

An object of class crs of length 2.

Details

See sf::st_crs for details.

Note

License: GPL 3.0

References

L. Ranghetti, M. Boschetti, F. Nutini, L. Busetto (2020). "sen2r": An R toolbox for automatically downloading and preprocessing Sentinel-2 satellite data. Computers & Geosciences, 139, 104473. doi:10.1016/j.cageo.2020.104473 , URL: https://sen2r.ranghetti.info/.

Author

Luigi Ranghetti, phD (2019)

Examples

## CRS from EPSG
st_crs2(32609)
#> Coordinate Reference System:
#>   User input: EPSG:32609 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     USAGE[
#>         SCOPE["Engineering survey, topographic mapping."],
#>         AREA["Between 132°W and 126°W, northern hemisphere between equator and 84°N, onshore and offshore. Canada - British Columbia (BC); NorthW Territories (NWT); Yukon. United States (USA) - Alaska (AK)."],
#>         BBOX[0,-132,84,-126]],
#>     ID["EPSG",32609]]
st_crs2("EPSG:32609")
#> Coordinate Reference System:
#>   User input: EPSG:32609 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     USAGE[
#>         SCOPE["Engineering survey, topographic mapping."],
#>         AREA["Between 132°W and 126°W, northern hemisphere between equator and 84°N, onshore and offshore. Canada - British Columbia (BC); NorthW Territories (NWT); Yukon. United States (USA) - Alaska (AK)."],
#>         BBOX[0,-132,84,-126]],
#>     ID["EPSG",32609]]

## CRS from UTM zone
st_crs2(9)
#> Coordinate Reference System:
#>   User input: EPSG:32609 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     USAGE[
#>         SCOPE["Engineering survey, topographic mapping."],
#>         AREA["Between 132°W and 126°W, northern hemisphere between equator and 84°N, onshore and offshore. Canada - British Columbia (BC); NorthW Territories (NWT); Yukon. United States (USA) - Alaska (AK)."],
#>         BBOX[0,-132,84,-126]],
#>     ID["EPSG",32609]]
st_crs2("09")
#> Coordinate Reference System:
#>   User input: EPSG:32609 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     USAGE[
#>         SCOPE["Engineering survey, topographic mapping."],
#>         AREA["Between 132°W and 126°W, northern hemisphere between equator and 84°N, onshore and offshore. Canada - British Columbia (BC); NorthW Territories (NWT); Yukon. United States (USA) - Alaska (AK)."],
#>         BBOX[0,-132,84,-126]],
#>     ID["EPSG",32609]]
st_crs2("9N")
#> Coordinate Reference System:
#>   User input: EPSG:32609 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     USAGE[
#>         SCOPE["Engineering survey, topographic mapping."],
#>         AREA["Between 132°W and 126°W, northern hemisphere between equator and 84°N, onshore and offshore. Canada - British Columbia (BC); NorthW Territories (NWT); Yukon. United States (USA) - Alaska (AK)."],
#>         BBOX[0,-132,84,-126]],
#>     ID["EPSG",32609]]
st_crs2("09S")
#> Coordinate Reference System:
#>   User input: EPSG:32709 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9S",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9S",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",10000000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["(E)",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["(N)",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     USAGE[
#>         SCOPE["Engineering survey, topographic mapping."],
#>         AREA["Between 132°W and 126°W, southern hemisphere between 80°S and equator, onshore and offshore."],
#>         BBOX[-80,-132,0,-126]],
#>     ID["EPSG",32709]]

## CRS from WKT (string or path)
(wkt_32n <- sf::st_as_text(sf::st_crs(32609)))
#> [1] "PROJCS[\"WGS 84 / UTM zone 9N\",GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\",SPHEROID[\"WGS 84\",6378137,298.257223563]],PRIMEM[\"Greenwich\",0],UNIT[\"degree\",0.0174532925199433,AUTHORITY[\"EPSG\",\"9122\"]],AUTHORITY[\"EPSG\",\"4326\"]],PROJECTION[\"Transverse_Mercator\"],PARAMETER[\"latitude_of_origin\",0],PARAMETER[\"central_meridian\",-129],PARAMETER[\"scale_factor\",0.9996],PARAMETER[\"false_easting\",500000],PARAMETER[\"false_northing\",0],UNIT[\"metre\",1],AXIS[\"Easting\",EAST],AXIS[\"Northing\",NORTH],AUTHORITY[\"EPSG\",\"32609\"]]"
st_crs2(wkt_32n)
#> Coordinate Reference System:
#>   User input: PROJCS["WGS 84 / UTM zone 9N",GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-129],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["metre",1],AXIS["Easting",EAST],AXIS["Northing",NORTH],AUTHORITY["EPSG","32609"]] 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["easting",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["northing",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     ID["EPSG",32609]]
writeLines(wkt_32n, wkt_32n_path <- tempfile())
st_crs2(wkt_32n_path)
#> Coordinate Reference System:
#>   User input: PROJCS["WGS 84 / UTM zone 9N",GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AUTHORITY["EPSG","4326"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-129],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["metre",1],AXIS["Easting",EAST],AXIS["Northing",NORTH],AUTHORITY["EPSG","32609"]] 
#>   wkt:
#> PROJCRS["WGS 84 / UTM zone 9N",
#>     BASEGEOGCRS["WGS 84",
#>         DATUM["World Geodetic System 1984",
#>             ELLIPSOID["WGS 84",6378137,298.257223563,
#>                 LENGTHUNIT["metre",1]]],
#>         PRIMEM["Greenwich",0,
#>             ANGLEUNIT["degree",0.0174532925199433]],
#>         ID["EPSG",4326]],
#>     CONVERSION["UTM zone 9N",
#>         METHOD["Transverse Mercator",
#>             ID["EPSG",9807]],
#>         PARAMETER["Latitude of natural origin",0,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8801]],
#>         PARAMETER["Longitude of natural origin",-129,
#>             ANGLEUNIT["degree",0.0174532925199433],
#>             ID["EPSG",8802]],
#>         PARAMETER["Scale factor at natural origin",0.9996,
#>             SCALEUNIT["unity",1],
#>             ID["EPSG",8805]],
#>         PARAMETER["False easting",500000,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8806]],
#>         PARAMETER["False northing",0,
#>             LENGTHUNIT["metre",1],
#>             ID["EPSG",8807]]],
#>     CS[Cartesian,2],
#>         AXIS["easting",east,
#>             ORDER[1],
#>             LENGTHUNIT["metre",1]],
#>         AXIS["northing",north,
#>             ORDER[2],
#>             LENGTHUNIT["metre",1]],
#>     ID["EPSG",32609]]

if (FALSE) {
## CRS from spatial file path
raster_path <- system.file(
  "extdata/out/S2A2A_20190723_022_Barbellino_BOA_10.tif", 
  package="sen2r"
)
vector_path <- system.file(
  "extdata/vector/barbellino.geojson", 
  package="sen2r"
)
try( st_crs2(raster_path) )
st_crs2(vector_path)

## CRS from spatial files
st_crs2(stars::read_stars(raster_path))
st_crs2(sf::read_sf(vector_path))

## CRS from PROJ.4 string
# (avoid using this with PROJ >= 6!)
st_crs2("+init=epsg:32609") # this makes use of the EPSG code
st_crs2("+proj=utm +zone=9 +datum=WGS84 +units=m +no_defs")
st_crs2(raster::raster(raster_path)) # st_crs(raster) uses the PROJ.4 as input
}