Swift 根据经纬度计算距离

//根据角度计算弧度
func radian(d:Double) -> Double {
return d * Double.pi/180.0
}
//根据弧度计算角度
func angle(r:Double) -> Double {
return r * 180/Double.pi
}

//根据两点经纬度计算两点距离
func getDistance(lat1:Double,lng1:Double,lat2:Double,lng2:Double) -> Double {
let EARTH_RADIUS:Double = 6378137.0

let radLat1:Double = self.radian(d: lat1)
let radLat2:Double = self.radian(d: lat2)

let radLng1:Double = self.radian(d: lng1)
let radLng2:Double = self.radian(d: lng2)

let a:Double = radLat1 - radLat2
let b:Double = radLng1 - radLng2

var s:Double = 2 * asin(sqrt(pow(sin(a/2), 2) + cos(radLat1) * cos(radLat2) * pow(sin(b/2), 2)))
s = s * EARTH_RADIUS
return s
}