Calculate distance between two points on globe from latitude and longitude coordinates.

The C# implementation of the Haversine formula is:

 public double GetDistanceBetweenPoints(double lat1, double long1, double lat2, double long2)

    {

        double distance = 0;

       

        double dLat = (lat2 - lat1) / 180* Math.PI;

        double dLong = (long2 - long1) / 180 * Math.PI;

 

        double a = Math.Sin(dLat / 2) * Math.Sin(dLat / 2)

                    + Math.Cos(lat2) * Math.Sin(dLong/2) * Math.Sin(dLong/2);

        double c = 2 * Math.Atan2(Math.Sqrt(a), Math.Sqrt(1 - a));

       

        //Calculate radius of earth

        // For this you can assume any of the two points.

        double radiusE = 6378135; // Equatorial radius, in metres

        double radiusP = 6356750; // Polar Radius

 

        //Numerator part of function

        double nr = Math.Pow(radiusE * radiusP * Math.Cos(lat1 / 180 * Math.PI), 2);

        //Denominator part of the function

        double dr = Math.Pow(radiusE * Math.Cos(lat1 / 180 * Math.PI), 2)

                        + Math.Pow(radiusP * Math.Sin(lat1 / 180 * Math.PI), 2);

        double radius = Math.Sqrt(nr / dr);

 

        //Calaculate distance in metres.

        distance = radius * c;

        return distance;

    }