Compute distances in Swift
Solver for the inverse geodesic problem in Swift.
The inverse geodesic problem must be solved to compute the distance between two points on an oblate spheroid, or
ellipsoid in general. The generalization to ellipsoids, which are not oblate spheroids is not further considered here,
hence the term ellipsoid will be used synonymous with oblate spheroid.
The distance between two points is also known as the
Vincenty distance.
Here is an example to compute the distance between two points (the poles in this case) on the
WGS 84 ellipsoid.
import geodesic
let d = distance((lat: Double.pi / 2,lon: 0), (lat: -Double.pi / 2, lon: 0))
and that’s it.
At least clang-3.6
is required. On linux one might need to install it explicitly. There are no dependencies on macOS.
let package = Package(
dependencies: [
.package(url: "https://github.com/dastrobu/geodesic.git", from: "1.4.0"),
]
)
This Swift package is a wrapper for the
C implementation of the geodesic routines in GeographicLib.
The goal of this Swift package is to make some algorithms from
GeographicLib available to the Swift world. Alternatively one can employ the
package vincenty
which is a much simpler solver for the inverse geodesic problem, completely written in Swift. Vincenty’s formulae does,
however, have some convergence problems in rare cases and may not give the same accuracy as Karney’s algorithm.
The computation does always converge and is said to compute up to machine precision. See documentation
of GeographicLib for details.
By default the
WGS 84 ellipsoid
is employed, but different parameters can be specified, e.g. for the
GRS 80 ellipsoid.
distance((lat: Double.pi / 2, lon: 0), (lat: -Double.pi / 2, lon: 0),
ellipsoid (a: 6378137.0, f: 1/298.257222100882711))
swift build
fails. No problems with clang on Linux.