原文地址：https://my.oschina.net/fankun2013/blog/338100
地图供应商比较多，产生了许多地图坐标。地图坐标正确转换是个问题。在之前开发地图应用的时候发现从WGS84坐标系（GPS）转换成某个地图坐标系都比较困难。然后只能使用地图供应商提供的webservice接口转换。百度也提供了免费的webservice接口（限制并发量）。对于少数点的转换性能还可以，但是对于非常多点的转换压力比较大（使用多线程并行计算）.个人感觉比较繁琐，而且很难保证转换的稳定性。
时间飞逝，百度地图更新了新版本，给我们带来了福音，map API中自带了相关坐标的转换，这就省事多了。但是其它的地图貌似没有提供转换API.怎么办呢？真是高手在民间呀，哪个牛人透露转换的算法呢？估计是和百度相关的牛人吧。下面是对算法的收集和整理。提供java版本。js版本参考：http://www.oschina.net/code/snippet_260395_39205
这下使用地图转换就比较准确了。
public class CoordinateConvertUtil { private static double PI = Math.PI; private static double AXIS = 6378245.0; // private static double OFFSET = 0.00669342162296594323; //(a^2 - b^2) / a^2 private static double X_PI = PI * 3000.0 / 180.0; public static void main(String[] args) { // 116.39806876799298,39.90830142538959 // 116.397826,39.90894374525333 // 116.3978262189183,39.90894374525333 String lon = "116.391910"; String lat = "39.906050"; lon = ""; lat = ""; double [] arr2 = bd092GCJ(39.9151, 116.4039595 ); System.out.println(arr2[0]+ "," + arr2[1]); double [] arr = bd092WGS(39.9151, 116.4039595 ); System.out.println(arr[0]+ "," + arr[1]); } //GCJ-02=>BD09 火星坐标系=>百度坐标系 public static double[] gcj2BD09(double glat, double glon){ double x = glon; double y = glat; double[] latlon = new double[2]; 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); latlon[0] = z * Math.sin(theta) + 0.006; latlon[1] = z * Math.cos(theta) + 0.0065; return latlon; } //BD09=>GCJ-02 百度坐标系=>火星坐标系 public static double[] bd092GCJ(double glat, double glon){ double x = glon - 0.0065; double y = glat - 0.006; double[] latlon = new double[2]; 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); latlon[0] = z * Math.sin(theta); latlon[1] = z * Math.cos(theta); return latlon; } //BD09=>WGS84 百度坐标系=>地球坐标系 public static double[] bd092WGS(double glat, double glon){ double[] latlon = bd092GCJ(glat,glon); return gcj2WGS(latlon[0],latlon[1]); } // WGS84=》BD09 地球坐标系=>百度坐标系 public static double[] wgs2BD09(double wgLat, double wgLon) { double[] latlon = wgs2GCJ(wgLat,wgLon); return gcj2BD09(latlon[0],latlon[1]); } // WGS84=》GCJ02 地球坐标系=>火星坐标系 public static double[] wgs2GCJ(double wgLat, double wgLon) { double[] latlon = new double[2]; if (outOfChina(wgLat, wgLon)){ latlon[0] = wgLat; latlon[1] = wgLon; return latlon; } double[] deltaD = delta(wgLat,wgLon); latlon[0] = wgLat + deltaD[0]; latlon[1] = wgLon + deltaD[1]; return latlon; } //GCJ02=>WGS84 火星坐标系=>地球坐标系(粗略) public static double[] gcj2WGS(double glat,double glon){ double[] latlon = new double[2]; if (outOfChina(glat, glon)){ latlon[0] = glat; latlon[1] = glon; return latlon; } double[] deltaD = delta(glat,glon); latlon[0] = glat - deltaD[0]; latlon[1] = glon - deltaD[1]; return latlon; } //GCJ02=>WGS84 火星坐标系=>地球坐标系（精确） public static double[] gcj2WGSExactly(double gcjLat,double gcjLon){ double initDelta = 0.01; double threshold = 0.000000001; double dLat = initDelta, dLon = initDelta; double mLat = gcjLat - dLat, mLon = gcjLon - dLon; double pLat = gcjLat + dLat, pLon = gcjLon + dLon; double wgsLat, wgsLon, i = 0; while (true) { wgsLat = (mLat + pLat) / 2; wgsLon = (mLon + pLon) / 2; double[] tmp = wgs2GCJ(wgsLat, wgsLon); dLat = tmp[0] - gcjLat; dLon = tmp[1] - gcjLon; 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 > 10000) break; } double[] latlon = new double[2]; latlon[0] = wgsLat; latlon[1] = wgsLon; return latlon; } //两点距离 public static double distance(double latA, double logA, double latB,double logB){ int earthR = 6371000; double x = Math.cos(latA*Math.PI/180) * Math.cos(latB*Math.PI/180) * Math.cos((logA-logB)*Math.PI/180); double y = Math.sin(latA*Math.PI/180) * Math.sin(latB*Math.PI/180); double s = x + y; if (s > 1) s = 1; if (s < -1) s = -1; double alpha = Math.acos(s); double distance = alpha * earthR; return distance; } public static double[] delta(double wgLat, double wgLon){ double[] latlng = new double[2]; 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 - OFFSET * magic * magic; double sqrtMagic = Math.sqrt(magic); dLat = (dLat * 180.0) / ((AXIS * (1 - OFFSET)) / (magic * sqrtMagic) * PI); dLon = (dLon * 180.0) / (AXIS / sqrtMagic * Math.cos(radLat) * PI); latlng[0] =dLat; latlng[1] =dLon; return latlng; } 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; } 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; } }