坐标系

1、WGS84

     世界大地测量系统 1984，GPS使用的参考坐标系，也称地心坐标系

2、CGCS2000

      2000国家大地坐标系，天地图使用，和WGS84坐标的误差很小

3、GCJ02

      火星坐标系,高德使用、google 国内地图使用(PS:使用谷歌地图的时候注意坐标系统)，和WGS84的误差一般在50-60米之间

4、bd09II

    百度坐标系，在GCJ02坐标基础之上进行加密的坐标

C# 坐标转换代码：

 public class GPSChange
    {
        private const double pi = 3.14159265358979324;
        private const double x_pi = 3.14159265358979324 * 3000.0 / 180.0;

        //克拉索天斯基椭球体参数值
        private const double a = 6378245.0;
        //第一偏心率
        private const double ee = 0.00669342162296594323;


        /// <summary>
        /// GCJ-02转换BD-09
        /// </summary>
        /// <param name="gg_lat">纬度</param>
        /// <param name="gg_lon">经度</param>
        /// <returns></returns>
        public static GPSPoint GCJ02_to_BD09(double gg_lat, double gg_lon)
        {
            GPSPoint point = new GPSPoint();
            double x = gg_lon, y = gg_lat;
            double z = Math.Sqrt(x * x + y * y) + 0.00002 * Math.Sin(y * x_pi);
            double theta = Math.Atan2(y, x) + 0.000003 * Math.Cos(x * x_pi);
            double bd_lon = z * Math.Cos(theta) + 0.0065;
            double bd_lat = z * Math.Sin(theta) + 0.006;
            point.SetLat(bd_lat);
            point.SetLng(bd_lon);
            return point;
        }

        /// <summary>
        /// BD-09转换GCJ-02
        /// </summary>
        /// <param name="bd_lat">纬度</param>
        /// <param name="bd_lon">经度</param>
        /// <returns></returns>
        public static GPSPoint BD09_to_GCJ02(double bd_lat, double bd_lon)
        {
            GPSPoint point = new GPSPoint();
            double x = bd_lon - 0.0065, y = bd_lat - 0.006;
            double z = Math.Sqrt(x * x + y * y) - 0.00002 * Math.Sin(y * x_pi);
            double theta = Math.Atan2(y, x) - 0.000003 * Math.Cos(x * x_pi);
            double gg_lon = z * Math.Cos(theta);
            double gg_lat = z * Math.Sin(theta);
            point.SetLat(gg_lat);
            point.SetLng(gg_lon);
            return point;
        }



        /// <summary>
        /// WGS-84转换GCJ-02
        /// </summary>
        /// <param name="wgLat">纬度</param>
        /// <param name="wgLon">经度</param>
        /// <returns></returns>
        public static GPSPoint WGS84_to_GCJ02(double wgLat, double wgLon)
        {
            GPSPoint point = new GPSPoint();
            if (OutOfChina(wgLat, wgLon))
            {
                point.SetLat(wgLat);
                point.SetLng(wgLon);
                return point;
            }
            double dLat = TransformLat(wgLon - 105.0, wgLat - 35.0);
            double dLon = TransformLon(wgLon - 105.0, wgLat - 35.0);
            double radLat = wgLat / 180.0 * pi;
            double magic = Math.Sin(radLat);
            magic = 1 - ee * magic * magic;
            double sqrtMagic = Math.Sqrt(magic);
            dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
            dLon = (dLon * 180.0) / (a / sqrtMagic * Math.Cos(radLat) * pi);
            double lat = wgLat + dLat;
            double lon = wgLon + dLon;
            point.SetLat(lat);
            point.SetLng(lon);
            return point;
        }

        /// <summary>
        /// GCJ02_to_WGS84
        /// </summary>
        /// <param name="wgLat">纬度</param>
        /// <param name="wgLon">经度</param>
        /// <returns></returns>
        public static GPSPoint GCJ02_to_WGS84(double wgLat, double wgLon)
        {
            GPSPoint gps = Transform(wgLat, wgLon);
            double lontitude = wgLon * 2 - gps.lng;
            double latitude = wgLat * 2 - gps.lat;
            return new GPSPoint(lontitude, latitude);
        }
        public static GPSPoint Transform(double wgLat, double wgLon)
        {
            GPSPoint gpspoint =new GPSPoint(wgLat, wgLon);
            if (OutOfChina(wgLat, wgLon))
            {
                gpspoint.lat = wgLat;
                gpspoint.lng = wgLon;
                return gpspoint;
            }
            double dLat = TransformLat(wgLon - 105.0, wgLat - 35.0);
            double dLon = TransformLon(wgLon - 105.0, wgLat - 35.0);
            double radLat = wgLat / 180.0 * pi;
            double magic = Math.Sin(radLat);
            magic = 1 - ee * magic * magic;
            double sqrtMagic = Math.Sqrt(magic);
            dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * pi);
            dLon = (dLon * 180.0) / (a / sqrtMagic * Math.Cos(radLat) * pi);
            gpspoint.lat = wgLat + dLat;
            gpspoint.lng = wgLon + dLon;
            return gpspoint;
        }

        private static bool OutOfChina(double lat, double lon)
        {
            if (lon < 72.004 || lon > 137.8347)
                return true;
            if (lat < 0.8293 || lat > 55.8271)
                return true;
            return false;
        }

        private static double TransformLat(double x, double y)
        {
            double ret = -100.0 + 2.0 * x + 3.0 * y + 0.2 * y * y + 0.1 * x * y + 0.2 * Math.Sqrt(Math.Abs(x));
            ret += (20.0 * Math.Sin(6.0 * x * pi) + 20.0 * Math.Sin(2.0 * x * pi)) * 2.0 / 3.0;
            ret += (20.0 * Math.Sin(y * pi) + 40.0 * Math.Sin(y / 3.0 * pi)) * 2.0 / 3.0;
            ret += (160.0 * Math.Sin(y / 12.0 * pi) + 320 * Math.Sin(y * pi / 30.0)) * 2.0 / 3.0;
            return ret;
        }

        private static double TransformLon(double x, double y)
        {
            double ret = 300.0 + x + 2.0 * y + 0.1 * x * x + 0.1 * x * y + 0.1 * Math.Sqrt(Math.Abs(x));
            ret += (20.0 * Math.Sin(6.0 * x * pi) + 20.0 * Math.Sin(2.0 * x * pi)) * 2.0 / 3.0;
            ret += (20.0 * Math.Sin(x * pi) + 40.0 * Math.Sin(x / 3.0 * pi)) * 2.0 / 3.0;
            ret += (150.0 * Math.Sin(x / 12.0 * pi) + 300.0 * Math.Sin(x / 30.0 * pi)) * 2.0 / 3.0;
            return ret;
        }
        /// <summary>
        /// 经纬度转墨卡托投影坐标
        /// </summary>
        /// <returns></returns>
        public static XYPoint lonlatTomercator(double lng, double lat) {
            XYPoint xypoint = new DataSource.XYPoint();
            double x = lng * 20037508.34 / 180;
            double y = Math.Log(Math.Tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
            y = y * 20037508.34 / 180;
            xypoint.x = x;
            xypoint.y = y;
            return xypoint;
        }

        /// <summary>
        /// 墨卡托投影坐标转经纬度坐标
        /// </summary>
        /// <returns></returns>
        public static GPSPoint mercatorTolonlat(double x,double y)
        {
            GPSPoint gpspoint = new DataSource.GPSPoint();
            double lng = x / 20037508.34 * 180;
            double lat = y / 20037508.34 * 180;
            y= 180/Math.PI*(2*Math.Atan(Math.Exp(y* Math.PI/180))-Math.PI/2);
            gpspoint.lng = lng;
            gpspoint.lat = lat;
            return gpspoint;
        }


    }
    public class XYPoint
    {
        public double x { get; set; }// 纬度
        public double y { get; set; }// 经度
    }

    public class GPSPoint
    {
        public double lat;// 纬度
        public double lng;// 经度

        public GPSPoint()
        {
        }

        public GPSPoint(double lng, double lat)
        {
            this.lng = lng;
            this.lat = lat;
        }


        public double GetLat()
        {
            return lat;
        }
        public void SetLat(double lat)
        {
            this.lat = lat;
        }
        public double GetLng()
        {
            return lng;
        }
        public void SetLng(double lng)
        {
            this.lng = lng;
        }
    }