transform geometries in stars objects to a new coordinate reference system, without warping

Source: R/transform.R

transform geometries in stars objects to a new coordinate reference system, without warping

# S3 method for stars
st_transform(x, crs, ...)

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

Arguments

x

object of class stars, with either raster or simple feature geometries
crs

object of class crs with target crs
...

ignored

Details

For simple feature dimensions, st_transform is called, leading to lossless transformation. For gridded spatial data, a curvilinear grid with transformed grid cell (centers) is returned, which is also lossless. To convert this to a regular grid in the new CRS, use st_warp (which is in general lossy).

See also

st_warp

Examples

geomatrix = system.file("tif/geomatrix.tif", package = "stars")
(x = read_stars(geomatrix))

#> stars object with 2 dimensions and 1 attribute
#> attribute(s):
#>  geomatrix.tif  
#>  Min.   : 74.0  
#>  1st Qu.:107.0  
#>  Median :123.0  
#>  Mean   :126.8  
#>  3rd Qu.:132.0  
#>  Max.   :255.0  
#> dimension(s):
#>   from to  offset delta                       refsys point values x/y
#> x    1 20 1841002   1.5 PROJCS["WGS 84 / UTM zone...  TRUE   NULL [x]
#> y    1 20 1144003  -1.5 PROJCS["WGS 84 / UTM zone...  TRUE   NULL [y]
#> sheared raster with parameters: -5 -5 
new = st_crs(4326)
y = st_transform(x, new)
plot(st_transform(st_as_sfc(st_bbox(x)), new), col = NA, border = 'red')

plot(st_as_sfc(y, as_points=FALSE), col = NA, border = 'green', axes = TRUE, add = TRUE)

image(y, col = heat.colors(12), add = TRUE)

plot(st_as_sfc(y, as_points=TRUE), pch=3, cex=.5, col = 'blue', add = TRUE)

plot(st_transform(st_as_sfc(x, as_points=FALSE), new), add = TRUE)