R/bearing.R

In r-spatial/lwgeom: Bindings to Selected 'liblwgeom' Functions for Simple Features

#' compute azimuth between sequence of points
#'
#' compute azimuth between sequence of points
#' @param x object of class \code{sf}, \code{sfc} or \code{sfg}
#' @export
#' @examples
#' library(sf)
#' p = st_sfc(st_point(c(7,52)), st_point(c(8,53)), crs = 4326)
#' st_geod_azimuth(p)
st_geod_azimuth = function(x) {
	stopifnot(st_is_longlat(x))
	stopifnot(all(st_is(x, "POINT")))
	p = st_crs(st_geometry(x), parameters = TRUE)
	ret = CPL_geodetic_azimuth(st_geometry(x), p$SemiMajor, p$InvFlattening)
	units(ret) = as_units("rad")
	ret
}