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liblwgeom geodetic functions

Source: R/geod.R
geod.Rd

liblwgeom geodetic functions for length, area, segmentizing, covers

Usage

st_geod_area(x)

st_geod_length(x)

st_geod_segmentize(x, max_seg_length)

st_geod_covers(x, y, sparse = TRUE)

st_geod_covered_by(x, y, sparse = TRUE)

st_geod_distance(x, y, tolerance = 0, sparse = FALSE)

Arguments

x

object of class sf, sfc or sfg

max_seg_length

segment length in degree, radians, or as a length unit (e.g., m)

y

object of class sf, sfc or sfg

sparse

logical; if TRUE, return a sparse matrix (object of class sgbp), otherwise, return a dense logical matrix.

tolerance

double or length units value: if positive, the first distance less than tolerance is returned, rather than the true distance

Details

st_area will give an error message when the area spans the equator and lwgeom is linked to a proj.4 version older than 4.9.0 (see lwgeom_extSoftVersion)

longitude coordinates returned are rescaled to [-180,180)

Note

this function should is used by st_distance, do not use it directly

Examples

library(sf)
nc = st_read(system.file("gpkg/nc.gpkg", package="sf"))
#> Reading layer `nc.gpkg' from data source 
#>   `/home/runner/work/_temp/Library/sf/gpkg/nc.gpkg' using driver `GPKG'
#> Simple feature collection with 100 features and 14 fields
#> Geometry type: MULTIPOLYGON
#> Dimension:     XY
#> Bounding box:  xmin: -84.32385 ymin: 33.88199 xmax: -75.45698 ymax: 36.58965
#> Geodetic CRS:  NAD27
st_geod_area(nc[1:3,])
#> Units: [m^2]
#> [1] 1137388604  611077263 1423489919
# st_area(nc[1:3,])
l = st_sfc(st_linestring(rbind(c(7,52), c(8,53))), crs = 4326)
st_geod_length(l)
#> 130359.3 [m]
library(units)
#> udunits database from /usr/share/xml/udunits/udunits2.xml
pol = st_polygon(list(rbind(c(0,0), c(0,60), c(60,60), c(0,0))))
x = st_sfc(pol, crs = 4326)
seg = st_geod_segmentize(x[1], set_units(10, km))
plot(seg, graticule = TRUE, axes = TRUE)

pole = st_polygon(list(rbind(c(0,80), c(120,80), c(240,80), c(0,80))))
pt = st_point(c(0,90))
x = st_sfc(pole, pt, crs = 4326)
st_geod_covers(x[c(1,1,1)], x[c(2,2,2,2)])
#> Sparse geometry binary predicate list of length 3, where the predicate
#> was `covers'
#>  1: 1, 2, 3, 4
#>  2: 1, 2, 3, 4
#>  3: 1, 2, 3, 4
pole = st_polygon(list(rbind(c(0,80), c(120,80), c(240,80), c(0,80))))
pt = st_point(c(30,70))
x = st_sfc(pole, pt, crs = 4326)
st_geod_distance(x, x)
#> Units: [m]
#>         [,1]    [,2]
#> [1,]       0 1378923
#> [2,] 1378923       0