GPS coordinates

Hi,

im trying to create an application that can calculate the distance between gps coordinates. i have the formula, however, i have problems implementing it in the GUI. The following code is an example. Help.

using System;
using System.Text;

public class CDistanceBetweenLocations
{
    public static double Calc(double Lat1,
                  double Long1, double Lat2, double Long2)
    {
        /*                
            dlon = lon2 - lon1
            dlat = lat2 - lat1
            a = (sin(dlat/2))^2 + cos(lat1) * cos(lat2) * (sin(dlon/2))^2
            c = 2 * atan2(sqrt(a), sqrt(1-a))
            d = R * c
               
            Where
                * dlon is the change in longitude
                * dlat is the change in latitude
                * c is the great circle distance in Radians.
                * R is the radius of a spherical Earth.
                * The locations of the two points in
                    spherical coordinates (longitude and
                    latitude) are lon1,lat1 and lon2, lat2.
        */
        double dDistance = Double.MinValue;
        double dLat1InRad = Lat1 * (Math.PI / 180.0);
        double dLong1InRad = Long1 * (Math.PI / 180.0);
        double dLat2InRad = Lat2 * (Math.PI / 180.0);
        double dLong2InRad = Long2 * (Math.PI / 180.0);

        double dLongitude = dLong2InRad - dLong1InRad;
        double dLatitude = dLat2InRad - dLat1InRad;

        // Intermediate result a.
        double a = Math.Pow(Math.Sin(dLatitude / 2.0), 2.0) +
                   Math.Cos(dLat1InRad) * Math.Cos(dLat2InRad) *
                   Math.Pow(Math.Sin(dLongitude / 2.0), 2.0);

        // Intermediate result c (great circle distance in Radians).
        double c = 2.0 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1.0 - a));

        // Distance.
        // const Double kEarthRadiusMiles = 3956.0;
        const Double kEarthRadiusKms = 6376.5;
        dDistance = kEarthRadiusKms * c;

        return dDistance;
    }

    public static double Calc(string NS1, double Lat1, double Lat1Min,
           string EW1, double Long1, double Long1Min, string NS2,
           double Lat2, double Lat2Min, string EW2,
           double Long2, double Long2Min)
    {
        double NS1Sign = NS1.ToUpper() == "N" ? 1.0 : -1.0;
        double EW1Sign = NS1.ToUpper() == "E" ? 1.0 : -1.0;
        double NS2Sign = NS2.ToUpper() == "N" ? 1.0 : -1.0;
        double EW2Sign = EW2.ToUpper() == "E" ? 1.0 : -1.0;
        return (Calc(
            (Lat1 + (Lat1Min / 60)) * NS1Sign,
            (Long1 + (Long1Min / 60)) * EW1Sign,
            (Lat2 + (Lat2Min / 60)) * NS2Sign,
            (Long2 + (Long2Min / 60)) * EW2Sign
            ));
    }

    public static void Main(string[] args)
    {
        if (args.Length < 12)
        {
            System.Console.WriteLine("usage: DistanceBetweenLocations" +
                    " N 43 35.500 W 80 27.800 N 43 35.925 W 80 28.318");
            return;
        }
        System.Console.WriteLine(Calc(
            args[0],
            System.Double.Parse(args[1]),
            System.Double.Parse(args[2]),
            args[3],
            System.Double.Parse(args[4]),
            System.Double.Parse(args[5]),
            args[6],
            System.Double.Parse(args[7]),
            System.Double.Parse(args[8]),
            args[9],
            System.Double.Parse(args[10]),
            System.Double.Parse(args[11])));

    }

}