In the process of map development, the following three types of map coordinate systems are generally accessible:
1.WGS-84 original coordinate system is generally based on WGS-84 coordinate system, the longitude and latitude recorded by International GPS recorder, the original longitude and latitude obtained by GPS positioning, and the longitude and latitude of Google and Gaud map positioning (abroad); however, it is not allowed to use WGS84 coordinate system directly in China, and it can only be used after encryption;
2.GCJ-02 coordinate system, also known as "Mars coordinate system", is an original coordinate system created by China Survey Bureau. It is encrypted by WGS-84. In China, GCJ-02 coordinate system must be used at least, or the coordinate system encrypted after GCJ-02 is encrypted, such as Baidu coordinate system. GCJ-02 coordinate system is used by both Google and Golder in China. It can be said that GCJ-02 is the most widely used coordinate system in China;
3. Baidu coordinate system: bd-09, baidu coordinate system is the coordinate system formed by encrypting the offset again on the basis of GCJ-02 coordinate system, which is only applicable to Baidu map. (at present, baidu API provides an API for converting from other coordinate systems to Baidu coordinate systems, but there is no API for converting from Baidu coordinate systems to other coordinate systems.)
using System; using System.Collections.Generic; using System.Linq; using System.Web; namespace Extensions { public class GpsExtension { public static double pi = 3.1415926535897932384626; public static double x_pi = 3.14159265358979324 * 3000.0 / 180.0; public static double a = 6378245.0; public static double ee = 0.00669342162296594323; public 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; } public 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; } public static double[] transform(double lat, double lon) { if (outOfChina(lat, lon)) { return new double[] { lat, lon }; } double dLat = transformLat(lon - 105.0, lat - 35.0); double dLon = transformLon(lon - 105.0, lat - 35.0); double radLat = lat / 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 mgLat = lat + dLat; double mgLon = lon + dLon; return new double[] { mgLat, mgLon }; } public 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; } /** * 84 to Gcj-02 world geodetic system = = > Mars geodetic system * * @param lat * @param lon * @return */ public static double[] gps84_To_Gcj02(double lat, double lon) { if (outOfChina(lat, lon)) { return new double[] { lat, lon }; } double dLat = transformLat(lon - 105.0, lat - 35.0); double dLon = transformLon(lon - 105.0, lat - 35.0); double radLat = lat / 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 mgLat = lat + dLat; double mgLon = lon + dLon; return new double[] { mgLat, mgLon }; } /// <summary> /// Mars coordinate system (GCJ-02) to 84 * * @param lon * @param lat * @return /// </summary> /// <param name="lat"></param> /// <param name="lon"></param> /// <returns></returns> public static double[] gcj02_To_Gps84(double lat, double lon) { double[] gps = transform(lat, lon); double lontitude = lon * 2 - gps[1]; double latitude = lat * 2 - gps[0]; return new double[] { latitude, lontitude }; } /** * Conversion algorithm of Mars coordinate system (GCJ-02) and Baidu coordinate system (BD-09) converts GCJ-02 coordinate to BD-09 coordinate * * @param lat * @param lon */ public static double[] gcj02_To_Bd09(double lat, double lon) { double x = lon, y = 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 tempLon = z * Math.Cos(theta) + 0.0065; double tempLat = z * Math.Sin(theta) + 0.006; double[] gps = { tempLat, tempLon }; return gps; } /** * * Conversion algorithm of Mars coordinate system (GCJ-02) and Baidu coordinate system (BD-09) * * convert BD-09 coordinate to GCJ-02 coordinate * @ param * bd_lat * @param bd_lon * @return */ public static double[] bd09_To_Gcj02(double lat, double lon) { double x = lon - 0.0065, y = 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 tempLon = z * Math.Cos(theta); double tempLat = z * Math.Sin(theta); double[] gps = { tempLat, tempLon }; return gps; } /**Convert gps84 to bd09 * @param lat * @param lon * @return */ public static double[] gps84_To_bd09(double lat, double lon) { double[] gcj02 = gps84_To_Gcj02(lat, lon); double[] bd09 = gcj02_To_Bd09(gcj02[0], gcj02[1]); return bd09; } public static double[] bd09_To_gps84(double lat, double lon) { double[] gcj02 = bd09_To_Gcj02(lat, lon); double[] gps84 = gcj02_To_Gps84(gcj02[0], gcj02[1]); //Keep six decimal places gps84[0] = retain6(gps84[0]); gps84[1] = retain6(gps84[1]); return gps84; } /**Keep six decimal places * @param num * @return */ private static double retain6(double num) { String result = String.Format("%.6f", num); return Convert.ToDouble(result); } } }