How to calculate the distance between two GPS coordinates without using Google Maps API?

Question

I\'m wondering if there\'s a way to calculate the distance of two GPS coordinates without relying on Google Maps API.

My app may receive the coordinates in float or

Answer 1

Converted the accepted answer to Swift 3.1 (works on Xcode 8.3), in case anyone needs it:

public static func calculateDistanceMeters(departure: CLLocationCoordinate2D, arrival: CLLocationCoordinate2D) -> Double {

    let rad_per_deg = Double.pi / 180.0 // PI / 180
    let rkm = 6371.0                    // Earth radius in kilometers
    let rm = rkm * 1000.0               // Radius in meters

    let dlat_rad = (arrival.latitude - departure.latitude) * rad_per_deg // Delta, converted to rad
    let dlon_rad = (arrival.longitude - departure.longitude) * rad_per_deg

    let lat1_rad = departure.latitude * rad_per_deg
    let lat2_rad = arrival.latitude * rad_per_deg

    let sinDlat = sin(dlat_rad/2)
    let sinDlon = sin(dlon_rad/2)
    let a = sinDlat * sinDlat + cos(lat1_rad) * cos(lat2_rad) * sinDlon * sinDlon
    let c = 2.0 * atan2(sqrt(a), sqrt(1-a))

    return rm * c
}