Swift 计算地图上两点的物理距离

方法一

参考：Moving a CLLocation by x meters

使用 Haversine Formula，公式考虑了地球的曲率，能够精确计算两个点之间的距离。

func calculateDistance(from coord1: CLLocationCoordinate2D, to coord2: CLLocationCoordinate2D) -> Double { 

    let earthRadius: Double = 6372797.6
    
	// 将经纬度转换为弧度 
    let lat1 = coord1.latitude * .pi / 180 
    let lat2 = coord2.latitude * .pi / 180 
    let deltaLat = (coord2.latitude - coord1.latitude) * .pi / 180 
    let deltaLon = (coord2.longitude - coord1.longitude) * .pi / 180 
    
    // Haversine公式 
    let a = sin(deltaLat / 2) * sin(deltaLat / 2) + cos(lat1) * cos(lat2) * sin(deltaLon / 2) * sin(deltaLon / 2) 
    let c = 2 * atan2(sqrt(a), sqrt(1 - a)) 
    
    // 返回的距离单位为米 
    return earthRadius * c 
}

方法二

将经纬度转换成墨卡托投影坐标，然后通过 MKMapPoint.distance 计算两点的距离。

let coordinate1 = CLLocationCoordinate2D(latitude: 28.209321, longitude: 112.843033)
let coordinate2 = CLLocationCoordinate2D(latitude: 28.209321, longitude: 112.843033)

let point1: MKMapPoint = MKMapPoint(Coordinate1)
let point2: MKMapPoint = MKMapPoint(Coordinate2)

let distance = point1.distance(to: point2)