Spherical Trignometry : HaversineDistance function to find distance between 2 GeoCordinates

HaversineDistance.cs

/// <summary>
/// Returns the distance in miles or kilometers of any two GeoCordinates
/// Ref: https://en.wikipedia.org/wiki/Haversine_formula
/// </summary>
/// <param name="pos1">Location 1</param>
/// <param name="pos2">Location 2</param>
/// <param name="unit">Miles or Kilometers or Meters</param>
/// <returns>Distance in the requested unit</returns>
public static double HaversineDistance(LatLng pos1, LatLng pos2, DistanceUnit unit)
{
    double R = (unit == DistanceUnit.Miles) ? 3960.0 : 6371.0;
    double lat = (pos2.Latitude - pos1.Latitude).ToRadians();
    double lng = (pos2.Longitude - pos1.Longitude).ToRadians();
    double h1 = Math.Sin(lat / 2) * Math.Sin(lat / 2) 
            + Math.Cos(pos1.Latitude.ToRadians()) 
            * Math.Cos(pos2.Latitude.ToRadians()) 
            * Math.Sin(lng / 2) * Math.Sin(lng / 2);
    var h2 = 2 * Math.Asin(Math.Min(1, Math.Sqrt(h1)));

    if (unit == DistanceUnit.Meters)
        return h2;
    else
        return R* h2;
}

public enum DistanceUnit { Miles, Kilometers, Meters };

/// <summary>
/// Specifies a Latitude / Longitude point.
/// </summary>
public class LatLng
{
public double Latitude { get; set; }
public double Longitude { get; set; }
public double Elevation { get; set; }
}