Great Circle Haversine function on .NET framework.

GreatCircle.cs

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

namespace GreatCircleNavigation
{
    class Program
    {
        static void Main(string[] args)
        {
            MapPoint m1 = new MapPoint(12.851853, 77.664216);
            MapPoint m2 = new MapPoint(12.851854, 77.664215);
            
            Console.WriteLine(m1.isWithinRange(m2, 20.00));
            Console.ReadKey();
        }
    }

    class MapPoint
    {
        private double latitude, longitude;
        private double R = 6371e3;

        private static double toRadian(double degree)
        {
            return (Math.PI / 180) * degree;
        }

        public MapPoint(double latitude, double longitude)
        {
            this.latitude = MapPoint.toRadian(latitude);
            this.longitude = MapPoint.toRadian(longitude);
        }

        public bool isWithinRange(MapPoint point, double radius)
        {
            double delPhi = this.getLatitude() - point.getLatitude();
            double delLambda = this.getLongitude() - point.getLongitude();

            double haversine = Math.Sin(delPhi / 2) * Math.Sin(delPhi / 2) +
                                Math.Cos(this.getLatitude()) * Math.Cos(point.getLatitude()) 
                                Math.Sin(delLambda / 2) * Math.Sin(delLambda / 2);
            
            double c = 2 * Math.Atan2(Math.Sqrt(haversine), Math.Sqrt(1 - haversine));
            
            double rad = R * c;

            Console.WriteLine(rad);
            return rad <= radius ? true : false;
        }

        double getLatitude()
        {
            return this.latitude;
        }

        double getLongitude()
        {
            return this.longitude;
        }
    }
}