# geod: liblwgeom geodetic functions In lwgeom: Bindings to Selected 'liblwgeom' Functions for Simple Features

 geod R Documentation

## liblwgeom geodetic functions

### Description

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)
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 May 31, 2023, 6:06 p.m.