Convert sfc object to an WKB object

st_as_binary(x, ...)

# S3 method for sfc
st_as_binary(
  x,
  ...,
  EWKB = FALSE,
  endian = .Platform$endian,
  pureR = FALSE,
  precision = attr(x, "precision"),
  hex = FALSE
)

# S3 method for sfg
st_as_binary(
  x,
  ...,
  endian = .Platform$endian,
  EWKB = FALSE,
  pureR = FALSE,
  hex = FALSE,
  srid = 0
)

Arguments

x	object to convert
...	ignored
EWKB	logical; use EWKB (PostGIS), or (default) ISO-WKB?
endian	character; either "big" or "little"; default: use that of platform
pureR	logical; use pure R solution, or C++?
precision	numeric; if zero, do not modify; to reduce precision: negative values convert to float (4-byte real); positive values convert to round(x*precision)/precision. See details.
hex	logical; return as (unclassed) hexadecimal encoded character vector?
srid	integer; override srid (can be used when the srid is unavailable locally).

Details

st_as_binary is called on sfc objects on their way to the GDAL or GEOS libraries, and hence does rounding (if requested) on the fly before e.g. computing spatial predicates like st_intersects. The examples show a round-trip of an sfc to and from binary.

For the precision model used, see also https://locationtech.github.io/jts/javadoc/org/locationtech/jts/geom/PrecisionModel.html. There, it is written that: ``... to specify 3 decimal places of precision, use a scale factor of 1000. To specify -3 decimal places of precision (i.e. rounding to the nearest 1000), use a scale factor of 0.001.''. Note that ALL coordinates, so also Z or M values (if present) are affected.

Examples

# examples of setting precision:
st_point(c(1/3, 1/6)) %>% st_sfc(precision = 1000) %>% st_as_binary %>% st_as_sfc
#> Geometry set for 1 feature 
#> geometry type:  POINT
#> dimension:      XY
#> bbox:           xmin: 0.333 ymin: 0.167 xmax: 0.333 ymax: 0.167
#> CRS:            NA
#> POINT (0.333 0.167)
st_point(c(1/3, 1/6)) %>% st_sfc(precision =  100) %>% st_as_binary %>% st_as_sfc
#> Geometry set for 1 feature 
#> geometry type:  POINT
#> dimension:      XY
#> bbox:           xmin: 0.33 ymin: 0.17 xmax: 0.33 ymax: 0.17
#> CRS:            NA
#> POINT (0.33 0.17)
st_point(1e6 * c(1/3, 1/6)) %>% st_sfc(precision = 0.01) %>% st_as_binary %>% st_as_sfc
#> Geometry set for 1 feature 
#> geometry type:  POINT
#> dimension:      XY
#> bbox:           xmin: 333300 ymin: 166700 xmax: 333300 ymax: 166700
#> CRS:            NA
#> POINT (333300 166700)
st_point(1e6 * c(1/3, 1/6)) %>% st_sfc(precision = 0.001) %>% st_as_binary %>% st_as_sfc
#> Geometry set for 1 feature 
#> geometry type:  POINT
#> dimension:      XY
#> bbox:           xmin: 333000 ymin: 167000 xmax: 333000 ymax: 167000
#> CRS:            NA
#> POINT (333000 167000)