Get precision
Set precision
st_precision(x)st_set_precision(x, precision)
st_precision(x) <- value
object of class sfc or sf
numeric, or object of class units with distance units (but see details); see st_as_binary for how to do this.
precision value
If precision is a units object, the object on which we set precision must have a coordinate reference system with compatible distance units.
Setting a precision has no direct effect on coordinates of geometries, but merely set an attribute tag to an sfc object.
The effect takes place in st_as_binary or, more precise, in the C++ function CPL_write_wkb, where simple feature geometries are being serialized to well-known-binary (WKB).
This happens always when routines are called in GEOS library (geometrical operations or predicates), for writing geometries using st_write or write_sf, st_make_valid in package lwgeom; also aggregate and summarise by default union geometries, which calls a GEOS library function.
Routines in these libraries receive rounded coordinates, and possibly return results based on them. st_as_binary contains an example of a roundtrip of sfc geometries through WKB, in order to see the rounding happening to R data.
The reason to support precision is that geometrical operations in GEOS or liblwgeom may work better at reduced precision. For writing data from R to external resources it is harder to think of a good reason to limiting precision.
st_as_binary for an explanation of what setting precision does, and the examples therein.
x <- st_sfc(st_point(c(pi, pi)))
st_precision(x)
st_precision(x) <- 0.01
st_precision(x)
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