Rescale sf* objects preserving the CRS
agila5 opened this issue · 2 comments
agila5 commented
Dear all, I created this issue since I have a couple of questions (the second of which is probably just a feature request) regarding the possibility of rescaling sf* objects (i.e. coordinates expressed in metres -> kilometres). The approach I currently adopt is the following:
library(sf)
#> Linking to GEOS 3.11.2, GDAL 3.7.2, PROJ 9.3.0; sf_use_s2() is TRUE
# pt represents a point near Milan. The coordinates are in metres
pt <- st_sfc(st_point(c(1.5e6, 5e6)), crs = 3003)
# Now I rescale it expressing the coordinates in km
st_transform(
pt,
pipeline = "+proj=pipeline +step +proj=unitconvert +xy_out=km"
)
#> Geometry set for 1 feature
#> Geometry type: POINT
#> Dimension: XY
#> Bounding box: xmin: 1500 ymin: 5000 xmax: 1500 ymax: 5000
#> CRS: NA
#> POINT (1500 5000)The previous code clearly works and it's really convenient. However, I was wondering:
- Are there more efficient (that maybe just include less typing and/or easier to remember 😅) alternatives?
- Is it possible to adjust the CRS of the output object using a correctly modified version of the input CRS (instead of the current NA_crs)?
Created on 2024-07-02 with reprex v2.0.2
Session info
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#> ──────────────────────────────────────────────────────────────────────────────edzer commented
I have wondered that myself: https://github.com/r-spatial/sf/blob/main/src/gdal.cpp#L664