geod: liblwgeom geodetic functions

Description Usage Arguments Details Note Examples

Description

liblwgeom geodetic functions for length, area, segmentizing, covers

Usage

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
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

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15
16
17
18
19
library(sf)
nc = st_read(system.file("gpkg/nc.gpkg", package="sf"))
st_geod_area(nc[1:3,])
# st_area(nc[1:3,])
l = st_sfc(st_linestring(rbind(c(7,52), c(8,53))), crs = 4326)
st_geod_length(l)
library(units)
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)])
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)

lwgeom documentation built on Jan. 31, 2020, 5:07 p.m.