C#实现地图坐标系的转换(WGS-84、GCJ-02、BD-09)

　　 wgs-84坐标系：全球定位系统使用，gps、北斗等

　　 gcj-02坐标系：中国地区使用，由wgs-84偏移而来

　　 bd-09坐标系：百度专用，由gcj-02偏移而来

　　(ps:源于项目需求，本来是想读图片的经纬度显示在百度离线地图上的。后来发现定位偏差太大，仔细一想，原来是图片和百度使用的坐标系不一样。

 

　　计算转换部分 

    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;
        }


        public static void transform(double wglat, double wglon, double[] latlng)
        {
            if (outofchina(wglat, wglon))
            {
                latlng[0] = wglat;
                latlng[1] = wglon;
                return;
            }
            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);
            latlng[0] = wglat + dlat;
            latlng[1] = wglon + dlon;
        }

        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;
        }

    }

 　　基础类

    public class gpspoint
    {
        private double lat;// 纬度
        private 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;
        }
        

    }