HexapiBackground.GpsExtensions.GetDistanceAndHeadingToDestination C# (CSharp) Method

        internal static double[] GetDistanceAndHeadingToDestination(double currentLat, double currentLon,
            double destinationLat, double destinationLon)
        {
            try
            {
                var diflat = (destinationLat - currentLat).ToRadians();

                currentLat = currentLat.ToRadians(); //convert current latitude to radians
                destinationLat = destinationLat.ToRadians(); //convert waypoint latitude to radians

                var diflon = (destinationLon - currentLon).ToRadians();
                //subtract and convert longitude to radians

                var distCalc = Math.Sin(diflat / 2.0) * Math.Sin(diflat / 2.0);
                var distCalc2 = Math.Cos(currentLat);

                distCalc2 = distCalc2 * Math.Cos(destinationLat);
                distCalc2 = distCalc2 * Math.Sin(diflon / 2.0);
                distCalc2 = distCalc2 * Math.Sin(diflon / 2.0); //and again, why?
                distCalc += distCalc2;
                distCalc = 2 * Math.Atan2(Math.Sqrt(distCalc), Math.Sqrt(1.0 - distCalc));
                distCalc = distCalc * 6371000.0;
                //Converting to meters. 6371000 is the magic number,  3959 is average Earth radius in miles
                distCalc = Math.Round(distCalc * 39.3701, 1); // and then to inches.

                currentLon = currentLon.ToRadians();
                destinationLon = destinationLon.ToRadians();

                var heading = Math.Atan2(Math.Sin(destinationLon - currentLon) * Math.Cos(destinationLat),
                    Math.Cos(currentLat) * Math.Sin(destinationLat) -
                    Math.Sin(currentLat) * Math.Cos(destinationLat) * Math.Cos(destinationLon - currentLon));

                heading = heading.ToDegrees();

                if (heading < 0)
                    heading += 360;

                return new[] { Math.Round(distCalc, 1), Math.Round(heading, 1) };
            }
            catch (Exception e)
            {
                Debug.WriteLine(e);
                return new double[] { 0, 0 };
            }
        }