LocationUtils.swift

import Foundation
import CoreLocation

extension FloatingPoint {
    var degreesToRadians: Self { return self * .pi / 180 }
    var radiansToDegrees: Self { return self * 180 / .pi }
}

extension CLLocationCoordinate2D {
    func coordinate(atDistance distanceInKm: Double, atBearingDegrees bearingDegrees: Double) -> CLLocationCoordinate2D {
        let distanceInRadians = distanceInKm / LocationUtils.meanRadiusOfEarth
        let startLatRadians = self.latitude.degreesToRadians
        let startLonRadians = self.longitude.degreesToRadians
        let bearingInRadians = bearingDegrees.degreesToRadians
        let endLatRadians = asin(sin(startLatRadians) * cos(distanceInRadians)
            + cos(startLatRadians) * sin(distanceInRadians) * cos(bearingInRadians))
        var endLonRadians = startLonRadians +
            atan2(
                (sin(bearingInRadians) * sin(distanceInRadians) * cos(startLatRadians)),
                (cos(distanceInRadians) - sin(startLatRadians) * sin(endLatRadians))
            )
        
        // adjust toLonRadians to be in the range -180 to +180...
        endLonRadians = fmod((endLonRadians + 3 * .pi), (2 * .pi)) - .pi
        
        let endLatDegrees = endLatRadians.radiansToDegrees
        let endLonDegrees = endLonRadians.radiansToDegrees
        let result = CLLocationCoordinate2DMake(endLatDegrees, endLonDegrees)
        
        return result
    }
}

enum LocationUtils {
    static let meanRadiusOfEarth = 6371.0 // km
}