st_as_binary {sf}

Convert sfc object to an WKB object

Description

Convert sfc object to an WKB object

Usage

st_as_binary(x, ...)

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

## S3 method for class '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
st_point(c(1/3, 1/6)) %>% st_sfc(precision =  100) %>% st_as_binary %>% st_as_sfc
st_point(1e6 * c(1/3, 1/6)) %>% st_sfc(precision = 0.01) %>% st_as_binary %>% st_as_sfc
st_point(1e6 * c(1/3, 1/6)) %>% st_sfc(precision = 0.001) %>% st_as_binary %>% st_as_sfc