using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace GPS
{
    public class Class1
    {
        public static float Calculate_Distance(float lat1, float lon1, float lat2, float lon2)
        {
            float pi = 3.141592654;
            float earth_radius = 6378.137;
            float Distance;
            lat1 = lat1 / 180 * pi;
            lon1 = lon1 / 180 * pi;
            lat2 = lat2 / 180 * pi;
            lon2 = lon2 / 180 * pi;

            Distance = (Math.Acos(Math.Sin(lat1) * Math.Sin(lat2) + Math.Cos(lat1) * Math.Cos(lat2) * Math.Cos(lon2 - lon1))) * earth_radius * 1000;
            return Distance;
        }
    }
}

.lib "GPS.dll"


Calculate_Distance#(lat1#, lon1#, lat2#, lon2#):"Calculate_Distance"

Print Calculate_Distance#(10,20,30,40)