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我是一名的程序猿，工作主要是关于GIS 系统的开发的。在GIS方面，你知道地图有多少种坐标系吗？
不知道吧！那我就要介绍介绍了。
WGS84坐标系
GPS，WGS-84，原始坐标体系。一般用国际标准的GPS记录仪记录下来的坐标，都是GPS的坐标。很可惜，在中国，任何一个地图产品都不允许使用GPS坐标，据说是为了保密。
GCJ02坐标系
国测局02年发布的坐标体系。又称“火星坐标”。在中国，必须至少使用GCJ-02的坐标体系。比如腾讯，高德都在用这个坐标体系。GCJ-02也是国内最广泛使用的坐标体系。
BD09坐标系
百度坐标系，GCJ02坐标系加密后的坐标系
那么这些坐标的互相转换时怎么的呢？那接下来我就推荐个使用JavaScript写的转换代码：
/*** 地图坐标转换器* */var GPS2Google2Baidu = {PI: 3.14159265358979324,x_pi: 3.14159265358979324 * 3000.0 / 180.0,delta: function (lat, lng) {// Krasovsky 1940//// a = 6378245.0, 1/f = 298.3// b = a * (1 - f)// ee = (a^2 - b^2) / a^2;var a = 6378245.0; // a: 卫星椭球坐标投影到平面地图坐标系的投影因子。var ee = 0.00669342162296594323; // ee: 椭球的偏心率。var dLat = this.transformLat(lng - 105.0, lat - 35.0);var dLng = this.transformLng(lng - 105.0, lat - 35.0);var radLat = lat / 180.0 * this.PI;var magic = Math.sin(radLat);magic = 1 - ee * magic * magic;var sqrtMagic = Math.sqrt(magic);dLat = (dLat * 180.0) / ((a * (1 - ee)) / (magic * sqrtMagic) * this.PI);dLng = (dLng * 180.0) / (a / sqrtMagic * Math.cos(radLat) * this.PI);return { 'lat': dLat, 'lng': dLng };},/*** WGS-84 to GCJ-02* @param {number} wgsLat* @param {number} wgsLng*/gcj_encrypt: function (wgsLat, wgsLng) {if (this.outOfChina(wgsLat, wgsLng))return { 'lat': wgsLat, 'lng': wgsLng };var d = this.delta(wgsLat, wgsLng);return { 'lat': wgsLat + d.lat, 'lng': wgsLng + d.lng };},/*** GCJ-02 to WGS-84* @param {number} gcjLat* @param {number} gcjLng*/gcj_decrypt: function (gcjLat, gcjLng) {if (this.outOfChina(gcjLat, gcjLng))return { 'lat': gcjLat, 'lng': gcjLng };var d = this.delta(gcjLat, gcjLng);return { 'lat': gcjLat - d.lat, 'lng': gcjLng - d.lng };},/*** GCJ-02 to WGS-84 exactly* @param {number} gcjLat* @param {number} gcjLng*/gcj_decrypt_exact: function (gcjLat, gcjLng) {var initDelta = 0.01;var threshold = 0.000000001;var dLat = initDelta, dLng = initDelta;var mLat = gcjLat - dLat, mLng = gcjLng - dLng;var pLat = gcjLat + dLat, pLng = gcjLng + dLng;var wgsLat, wgsLng, i = 0;while (1) {wgsLat = (mLat + pLat) / 2;wgsLng = (mLng + pLng) / 2;var tmp = this.gcj_encrypt(wgsLat, wgsLng)dLat = tmp.lat - gcjLat;dLng = tmp.lng - gcjLng;if ((Math.abs(dLat) < threshold) && (Math.abs(dLng) < threshold))break;if (dLat > 0) pLat = wgsLat; else mLat = wgsLat;if (dLng > 0) pLng = wgsLng; else mLng = wgsLng;if (++i > 10000) break;}//console.log(i);return { 'lat': wgsLat, 'lng': wgsLng };},/*** GCJ-02 to BD-09* @param {number} gcjLat* @param {number} gcjLng**/bd_encrypt: function (gcjLat, gcjLng) {var x = gcjLng, y = gcjLat;var z = Math.sqrt(x * x + y * y) + 0.00002 * Math.sin(y * this.x_pi);var theta = Math.atan2(y, x) + 0.000003 * Math.cos(x * this.x_pi);var bdLng = z * Math.cos(theta) + 0.0065;var bdLat = z * Math.sin(theta) + 0.006;return { 'lat': bdLat, 'lng': bdLng };},/*** BD-09 to GCJ-02* @param {*} bdLat* @param {*} bdLng*/bd_decrypt: function (bdLat, bdLng) {var x = bdLng - 0.0065, y = bdLat - 0.006;var z = Math.sqrt(x * x + y * y) - 0.00002 * Math.sin(y * this.x_pi);var theta = Math.atan2(y, x) - 0.000003 * Math.cos(x * this.x_pi);var gcjLng = z * Math.cos(theta);var gcjLat = z * Math.sin(theta);return { 'lat': gcjLat, 'lng': gcjLng };},//WGS-84 to Web mercator//mercatorLat -> y mercatorLng -> xmercator_encrypt: function (wgsLat, wgsLng) {var x = wgsLng * 20037508.34 / 180.;var y = Math.log(Math.tan((90. + wgsLat) * this.PI / 360.)) / (this.PI / 180.);y = y * 20037508.34 / 180.;return { 'lat': y, 'lng': x };/*if ((Math.abs(wgsLng) > 180 || Math.abs(wgsLat) > 90))return null;var x = 6378137.0 * wgsLng * 0.017453292519943295;var a = wgsLat * 0.017453292519943295;var y = 3189068.5 * Math.log((1.0 + Math.sin(a)) / (1.0 - Math.sin(a)));return {'lat' : y, 'lng' : x};//*/},// Web mercator to WGS-84// mercatorLat -> y mercatorLng -> xmercator_decrypt: function (mercatorLat, mercatorLng) {var x = mercatorLng / 20037508.34 * 180.;var y = mercatorLat / 20037508.34 * 180.;y = 180 / this.PI * (2 * Math.atan(Math.exp(y * this.PI / 180.)) - this.PI / 2);return { 'lat': y, 'lng': x };/*if (Math.abs(mercatorLng) < 180 && Math.abs(mercatorLat) < 90)return null;if ((Math.abs(mercatorLng) > 20037508.3427892) || (Math.abs(mercatorLat) > 20037508.3427892))return null;var a = mercatorLng / 6378137.0 * 57.295779513082323;var x = a - (Math.floor(((a + 180.0) / 360.0)) * 360.0);var y = (1.5707963267948966 - (2.0 * Math.atan(Math.exp((-1.0 * mercatorLat) / 6378137.0)))) * 57.295779513082323;return {'lat' : y, 'lng' : x};//*/},// two point's distancedistance: function (latA, lngA, latB, lngB) {var earthR = 6371000.;var x = Math.cos(latA * this.PI / 180.) * Math.cos(latB * this.PI / 180.) * Math.cos((lngA - lngB) * this.PI / 180);var y = Math.sin(latA * this.PI / 180.) * Math.sin(latB * this.PI / 180.);var s = x + y;if (s > 1) s = 1;if (s < -1) s = -1;var alpha = Math.acos(s);var distance = alpha * earthR;return distance;},outOfChina: function (lat, lng) {if (lng < 72.004 || lng > 137.8347)return true;if (lat < 0.8293 || lat > 55.8271)return true;return false;},transformLat: function (x, y) {var 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 * this.PI) + 20.0 * Math.sin(2.0 * x * this.PI)) * 2.0 / 3.0;ret += (20.0 * Math.sin(y * this.PI) + 40.0 * Math.sin(y / 3.0 * this.PI)) * 2.0 / 3.0;ret += (160.0 * Math.sin(y / 12.0 * this.PI) + 320 * Math.sin(y * this.PI / 30.0)) * 2.0 / 3.0;return ret;},transformLng: function (x, y) {var 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 * this.PI) + 20.0 * Math.sin(2.0 * x * this.PI)) * 2.0 / 3.0;ret += (20.0 * Math.sin(x * this.PI) + 40.0 * Math.sin(x / 3.0 * this.PI)) * 2.0 / 3.0;ret += (150.0 * Math.sin(x / 12.0 * this.PI) + 300.0 * Math.sin(x / 30.0 * this.PI)) * 2.0 / 3.0;return ret;}};//WGS84转GCj02GPS2Google2Baidu.WGS_84_to_GCJ_02 = GPS2Google2Baidu.gcj_encrypt;//GCJ02 转换为 WGS84GPS2Google2Baidu.GCJ_02_to_WGS_84 = GPS2Google2Baidu.gcj_decrypt_exact;//火星坐标系 (GCJ-02) 转百度坐标系 (BD-09)GPS2Google2Baidu.GCJ_02_to_BD_09 = GPS2Google2Baidu.bd_encrypt;//百度坐标系 (BD-09) 转火星坐标系 (GCJ-02)GPS2Google2Baidu.BD_09_to_GCJ_02 = GPS2Google2Baidu.bd_decrypt;//百度坐标系 (BD-09) 转 WGS84GPS2Google2Baidu.BD_09_to_WGS_84 = function (lat, lng) {var b2c = this.BD_09_to_GCJ_02(lat, lng);return this.GCJ_02_to_WGS_84(b2c.lat, b2c.lng);}// WGS84转 百度坐标系 (BD-09)GPS2Google2Baidu.WGS_84_to_BD_09 = function (lat, lng) {var w2c = this.WGS_84_to_GCJ_02(lat, lng);return this.GCJ_02_to_BD_09(w2c.lat, w2c.lng);}export default GPS2Google2Baidu;
来源：oschina
链接：https://my.oschina.net/yuantao/blog/3149379