iOS 根據兩點經緯度計算距離的樣本

根據兩點經緯度計算距離方法：

- (double)latitudeAndLongitudeWithLon1:(double)lon1 lat1:(double)lat1 lon2:(double)lon2 lat2:(double)lat2{
    double er = 6378137; // 6378700.0f;
    //ave. radius = 6371.315 (someone said more accurate is 6366.707)
    //equatorial radius = 6378.388
    //nautical mile = 1.15078
    double radlat1 = M_PI*lat1/180.0f;
    double radlat2 = M_PI*lat2/180.0f;
    double radlong1 = M_PI*lon1/180.0f;
    double radlong2 = M_PI*lon2/180.0f;
    if( radlat1 < 0 ) radlat1 = M_PI/2 + fabs(radlat1);// south
    if( radlat1 > 0 ) radlat1 = M_PI/2 - fabs(radlat1);// north
    if( radlong1 < 0 ) radlong1 = M_PI*2 - fabs(radlong1);//west
    if( radlat2 < 0 ) radlat2 = M_PI/2 + fabs(radlat2);// south
    if( radlat2 > 0 ) radlat2 = M_PI/2 - fabs(radlat2);// north
    if( radlong2 < 0 ) radlong2 = M_PI*2 - fabs(radlong2);// west
    //spherical coordinates x=r*cos(ag)sin(at), y=r*sin(ag)*sin(at), z=r*cos(at)
    //zero ag is up so reverse lat
    double x1 = er * cos(radlong1) * sin(radlat1);
    double y1 = er * sin(radlong1) * sin(radlat1);
    double z1 = er * cos(radlat1);
    double x2 = er * cos(radlong2) * sin(radlat2);
    double y2 = er * sin(radlong2) * sin(radlat2);
    double z2 = er * cos(radlat2);
    double d = sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2)+(z1-z2)*(z1-z2));
    //side, side, side, law of cosines and arccos
    double theta = acos((er*er+er*er-d*d)/(2*er*er));
    double dist  = theta*er;
    return dist;
}

列印：

NSLog(@"%f米",[self latitudeAndLongitudeWithLon1:32.000000 lat1:35.000000 lon2:37.000000 lat2:40.000000]);
註：這裡返回的單位是米