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

namespace GpsConvert
{
    class Program
    {
        static void Main(string[] args)
        {
            //double[] utm = LatLonToUtm(30.65156708, 103.6880587);
            double[] utm = LatLonToUtm(31.108761,121.314085);
            Console.WriteLine($"X:{utm[0]},Y:{utm[1]},区域:{utm[2]}");
           var ss= Wgs84Tosh(31.0158865505,121.2238203740);
            Console.WriteLine($"X:{ss[0]},Y:{ss[1]}");
            Console.ReadLine();
        }


        static double pi = Math.PI;

        static double sm_a = 6378137.0;
        static double sm_b = 6356752.314;
        //static double sm_EccSquared = 6.69437999013e-03;

        static double UTMScaleFactor = 0.9996;
        //得到的结果是：x坐标，y坐标，区域编号
        public static double[] LatLonToUtm (double lat, double lon)
        {
            double zone = Math.Floor((lon + 180.0) / 6) + 1;

            double cm = UtmCentralMeridian(zone);

            MapLatLonToXy(lat / 180.0 * pi, lon / 180 * pi, cm, out var xy);

            /* Adjust easting and northing for UTM system. */
            xy[0] = xy[0] * UTMScaleFactor + 500000.0;
            xy[1] = xy[1] * UTMScaleFactor;
            if (xy[1] < 0.0)
            {
                xy[1] = xy[1] + 10000000.0;
            }

            return new double[] { xy[0], xy[1], zone };
        }

        public static double UtmCentralMeridian (double zone)
        {
            double cmeridian;

            double deg = -183.0 + (zone * 6.0);

            cmeridian = deg / 180.0 * pi;
    
            return cmeridian;
        }

        internal static void MapLatLonToXy (double phi, double lambda, double lambda0, out double[] xy)
        {
            /* Precalculate ep2 */
            var ep2 = (Math.Pow(sm_a, 2.0) - Math.Pow(sm_b, 2.0)) / Math.Pow(sm_b, 2.0);
    
            /* Precalculate nu2 */
            var nu2 = ep2 * Math.Pow(Math.Cos(phi), 2.0);
    
            /* Precalculate N */
            var N = Math.Pow(sm_a, 2.0) / (sm_b * Math.Sqrt(1 + nu2));
    
            /* Precalculate t */
            var t = Math.Tan (phi);
            var t2 = t * t;

            /* Precalculate l */
            var l = lambda - lambda0;
    
            /* Precalculate coefficients for l**n in the equations below
               so a normal human being can read the expressions for easting
               and northing
               -- l**1 and l**2 have coefficients of 1.0 */
            var l3coef = 1.0 - t2 + nu2;
    
            var l4coef = 5.0 - t2 + 9 * nu2 + 4.0 * (nu2 * nu2);
    
            var l5coef = 5.0 - 18.0 * t2 + (t2 * t2) + 14.0 * nu2
                            - 58.0 * t2 * nu2;
    
            var l6coef = 61.0 - 58.0 * t2 + (t2 * t2) + 270.0 * nu2
                            - 330.0 * t2 * nu2;
    
            var l7coef = 61.0 - 479.0 * t2 + 179.0 * (t2 * t2) - (t2 * t2 * t2);
    
            var l8coef = 1385.0 - 3111.0 * t2 + 543.0 * (t2 * t2) - (t2 * t2 * t2);

            /* Calculate easting (x) */

            xy = new double[2];
            xy[0] = N * Math.Cos (phi) * l
                + (N / 6.0 * Math.Pow (Math.Cos (phi), 3.0) * l3coef * Math.Pow (l, 3.0))
                + (N / 120.0 * Math.Pow(Math.Cos(phi), 5.0) * l5coef * Math.Pow(l, 5.0))
                + (N / 5040.0 * Math.Pow(Math.Cos(phi), 7.0) * l7coef * Math.Pow(l, 7.0));
    
            /* Calculate northing (y) */
            xy[1] = ArcLengthOfMeridian (phi)
                + (t / 2.0 * N * Math.Pow(Math.Cos(phi), 2.0) * Math.Pow(l, 2.0))
                + (t / 24.0 * N * Math.Pow(Math.Cos(phi), 4.0) * l4coef * Math.Pow(l, 4.0))
                + (t / 720.0 * N * Math.Pow(Math.Cos(phi), 6.0) * l6coef * Math.Pow(l, 6.0))
                + (t / 40320.0 * N * Math.Pow(Math.Cos(phi), 8.0) * l8coef * Math.Pow(l, 8.0));
    
            return;
        }

        internal static double ArcLengthOfMeridian(double phi)
        {
            double alpha, beta, gamma, delta, epsilon, n;
            double result;

            /* Precalculate n */
            n = (sm_a - sm_b) / (sm_a + sm_b);

            /* Precalculate alpha */
            alpha = ((sm_a + sm_b) / 2.0)
               * (1.0 + (Math.Pow(n, 2.0) / 4.0) + (Math.Pow(n, 4.0) / 64.0));

            /* Precalculate beta */
            beta = (-3.0 * n / 2.0) + (9.0 * Math.Pow(n, 3.0) / 16.0)
               + (-3.0 * Math.Pow(n, 5.0) / 32.0);

            /* Precalculate gamma */
            gamma = (15.0 * Math.Pow(n, 2.0) / 16.0)
                + (-15.0 * Math.Pow(n, 4.0) / 32.0);
    
            /* Precalculate delta */
            delta = (-35.0 * Math.Pow(n, 3.0) / 48.0)
                + (105.0 * Math.Pow(n, 5.0) / 256.0);
    
            /* Precalculate epsilon */
            epsilon = (315.0 * Math.Pow(n, 4.0) / 512.0);
    
            /* Now calculate the sum of the series and return */
            result = alpha
                * (phi + (beta * Math.Sin (2.0 * phi))
                    + (gamma * Math.Sin(4.0 * phi))
                    + (delta * Math.Sin(6.0 * phi))
                    + (epsilon * Math.Sin(8.0 * phi)));

            return result;
        }
 
        // 经纬度坐标转换为上海地方坐标
        public static double[] Wgs84Tosh(double lat, double lon)
        {
            double xx, yy, r2d, tolat, tolon, rearth, PI;
            PI = 3.141592653589793;
            r2d = 57.2957795131;
            tolat = (31 + (14.0 + 7.55996 / 60.0) / 60.0) / r2d;
            tolon = (121.0 + (28.0 + 1.80651 / 60.0) / 60) / r2d;
            rearth = 6371006.84;
            double hor, frlat, frlon, gcdist, clatf, clatt, slatf, slatt, gcbrg;
            double dlon, cdlon, sdlon, sdist, cdist, sbrg, cbrg, temp;
            double intlat, intlon;
            intlat = lat;
            intlon = lon;
            frlat = lat / r2d;
            frlon = lon / r2d;
            clatt = Math.Cos(frlat);
            clatf = Math.Cos(tolat);
            slatt = Math.Sin(frlat);
            slatf = Math.Sin(tolat);
            dlon = frlon - tolon;
            cdlon = Math.Cos(dlon);
            sdlon = Math.Sin(dlon);
            cdist = slatf * slatt + clatf * clatt * cdlon;
            temp = (clatt * sdlon) * (clatt * sdlon) + (clatf * slatt - slatf * clatt * cdlon) * (clatf * slatt - slatf * clatt * cdlon);
            sdist = Math.Sqrt(Math.Abs(temp));
            if ((Math.Abs(sdist) > 1e-7) || (Math.Abs(cdist) > 1e-7))
                gcdist = Math.Atan2(sdist, cdist);
            else
                gcdist = 0;
            sbrg = sdlon * clatt;
            cbrg = (clatf * slatt - slatf * clatt * cdlon);
            if ((Math.Abs(sbrg) > 1e-7) || (Math.Abs(cbrg) > 1e-7))
            {
                temp = Math.Atan2(sbrg, cbrg);
                while (temp < 0)
                {
                    temp = temp + 2 * PI;
                    gcbrg = temp;
                }
            }
            else
                gcbrg = 0;


            hor = gcdist * rearth;
            xx = hor * Math.Sin(temp);
            yy = hor * Math.Cos(temp);
            double[] res = new double[2];
            res[0] = xx;
            res[1] = yy;
            return res;
        }
    }
}