toys/gps/docs/gcj02wgs84.java

/***
 * wgs84 84年提出，大地坐标，也是原始坐标。
 * gcj02 02年提出，火星坐标，经过加密算法。大多数非百度中国地图厂商基本都是使用的火星坐标：高德，腾讯，谷歌中国cn
 * bd09  09年提出，百度坐标，经过火星坐标再次加密，相当于对大地坐标经过了二次加密。百度自己使用
 * 一般的算法，没有直接bd09->wgs84或者wgs84->bd09，都需要借助wgs84->gcj02或者gcj02->wgs84算法推导。
 */
public class GpsTransfer {
	//π的定义
	public static double pi = 3.1415926535897932384626;
	//椭球长半径，依据克拉索索夫斯基椭球系数计算
	public static double a = 6378245.0;  
	//第一偏心率的平方
	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;
	}
	
	/***
	 * 判断是否在中国范围之内
	 * @param lat
	 * @param lon
	 * @return
	 */
	public static boolean 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;
	}
	
	/***
	 * 把公式部分抽取出来
	 * @param lat
	 * @param lon
	 * @return
	 */
	public static Gps transform(double lat, double lon) {
		if (outOfChina(lat, lon)) {
			return new Gps(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 Gps(mgLat, mgLon);
	}
	
	/***
	 * wgs84到gcj02转换
	 * @param lat
	 * @param lon
	 * @return
	 */
	public static Gps wgs84_To_Gcj02(double lat, double lon) {
		return transform(lat, lon);
	}
 
	/***
	 * 简单的gcj02到wgs84坐标类型转换，只做了一次迭代
	 */
	public static Gps gcj02_To_Wgs84(double lat, double lon) {
		Gps gps = transform(lat, lon);
		double lontitude = lon * 2 - gps.lon;
		double latitude = lat * 2 - gps.lat;
		return new Gps(latitude, lontitude);
	}
	
	/***
	 * 稍微精确一点的gcj02到wgs84转换
	 * @param lat
	 * @param lon
	 * @return
	 */
	public static Gps gcj02_To_Wgs84_exact(double lat,double lon) {
		if (outOfChina(lat, lon)) {
			return gcj02_To_Wgs84(lat, lon);
		}
		double initDelta = 0.01;
	    double threshold = 0.000001;
	    double dLat = initDelta;
	    double dLon = initDelta;
	    double mLat = lat - dLat;
	    double mLon = lon - dLon;
	    double pLat = lat + dLat;
	    double pLon = lon + dLon;
	    double wgsLat = 0;
	    double wgsLon = 0;
	    int i = 0;
	    while (true) {
	        wgsLat = (mLat + pLat) / 2;
	        wgsLon = (mLon + pLon) / 2;
	        Gps tmp = wgs84_To_Gcj02(wgsLat, wgsLon);
	        dLat = tmp.lat - lat;
	        dLon = tmp.lon - lon;
	        if ((Math.abs(dLat) < threshold) && (Math.abs(dLon) < threshold)) {
	            break;
	        }
	        if (dLat > 0) { pLat = wgsLat; } else { mLat = wgsLat;}
	        if (dLon > 0) { pLon = wgsLon; } else { mLon = wgsLon;}
	
	        if (++i > 1000) break;
	    }
	    
	    return new Gps(wgsLat, wgsLon);
	}
 
	/***
	 * 百度坐标是在火星坐标基础上做的二次加密
	 * @param gg_lat
	 * @param gg_lon
	 * @return
	 */
	public static Gps gcj02_To_Bd09(double gg_lat, double gg_lon) {
		double x = gg_lon, y = gg_lat;
		double z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * pi);
		double theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * pi);
		double bd_lon = z * Math.cos(theta) + 0.0065;
		double bd_lat = z * Math.sin(theta) + 0.006;
		return new Gps(bd_lat, bd_lon);
	}
 
	/***
	 * 百度坐标与火星坐标逆向转换
	 * @param bd_lat
	 * @param bd_lon
	 * @return
	 */
	public static Gps bd09_To_Gcj02(double bd_lat, double bd_lon) {
		double x = bd_lon - 0.0065, y = bd_lat - 0.006;
		double z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * pi);
		double theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * pi);
		double gg_lon = z * Math.cos(theta);
		double gg_lat = z * Math.sin(theta);
		return new Gps(gg_lat, gg_lon);
	}
	
	public static void main(String[] args) {
		Gps gps = new Gps(39.9072885060602, 116.39123343289631);
		System.out.println(gps);//{39.9072885060602,116.39123343289631}
		Gps gps2 = wgs84_To_Gcj02(gps.lat, gps.lon);
		System.out.println(gps2);//{39.9086897410389,116.39747455259267}
		Gps gps3 = gcj02_To_Wgs84(gps2.lat, gps2.lon);
		System.out.println(gps3);//{39.907286247736586,116.39123098626051}
		Gps gps4 = gcj02_To_Wgs84_exact(gps2.lat, gps2.lon);
		System.out.println(gps4);//{39.907288984202964,116.3912337078661} 相对一次迭代是精确了，但是好像也不是完全还原
	}
 
}
 
class Gps{
	double lat,lon;
	public Gps() {
	}
	public Gps(double lat,double lon){
		this.lat = lat;
		this.lon = lon;
	}
	@Override
	public String toString() {
		return "{"+lat+","+lon+"}";
	}
}