GPS坐标互转：WGS-84(GPS)、GCJ-02(Google地图)、BD-09(百度地图)

WGS-84：是国际标准，GPS坐标（Google Earth使用、或者GPS模块）
GCJ-02：中国坐标偏移标准，Google Map、高德、腾讯使用
BD-09：百度坐标偏移标准，Baidu Map使用

//WGS-84 to GCJ-02
GPS.gcj_encrypt();

//GCJ-02 to WGS-84 粗略
GPS.gcj_decrypt();

//GCJ-02 to WGS-84 精确(二分极限法)
// var threshold = 0.000000001; 目前设置的是精确到小数点后9位，这个值越小，越精确，但是javascript中，浮点运算本身就不太精确，九位在GPS里也偏差不大了
GSP.gcj_decrypt_exact();

//GCJ-02 to BD-09
GPS.bd_encrypt();

//BD-09 to GCJ-02
GPS.bd_decrypt();

//求距离
GPS.distance();

示例：
document.write("GPS: 39.933676862706776,116.35608315379092<br />");
var arr2 = GPS.gcj_encrypt(39.933676862706776, 116.35608315379092);
document.write("中国:" + arr2['lat']+","+arr2['lon']+'<br />');
var arr3 = GPS.gcj_decrypt_exact(arr2['lat'], arr2['lon']);
document.write('逆算:' + arr3['lat']+","+arr3['lon']+' 需要和第一行相似（目前是小数点后9位相等）');

JavaScript代码

var GPS = {

    PI : 3.14159265358979324,

    x_pi : 3.14159265358979324 * 3000.0 / 180.0,

    delta : function (lat, lon) {

        // 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(lon - 105.0, lat - 35.0);

        var dLon = this.transformLon(lon - 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);

        dLon = (dLon * 180.0) / (a / sqrtMagic * Math.cos(radLat) * this.PI);

        return {'lat': dLat, 'lon': dLon};

    },

     

    //WGS-84 to GCJ-02

    gcj_encrypt : function (wgsLat, wgsLon) {

        if (this.outOfChina(wgsLat, wgsLon))

            return {'lat': wgsLat, 'lon': wgsLon};

 

        var d = this.delta(wgsLat, wgsLon);

        return {'lat' : wgsLat + d.lat,'lon' : wgsLon + d.lon};

    },

    //GCJ-02 to WGS-84

    gcj_decrypt : function (gcjLat, gcjLon) {

        if (this.outOfChina(gcjLat, gcjLon))

            return {'lat': gcjLat, 'lon': gcjLon};

         

        var d = this.delta(gcjLat, gcjLon);

        return {'lat': gcjLat - d.lat, 'lon': gcjLon - d.lon};

    },

    //GCJ-02 to WGS-84 exactly

    gcj_decrypt_exact : function (gcjLat, gcjLon) {

        var initDelta = 0.01;

        var threshold = 0.000000001;

        var dLat = initDelta, dLon = initDelta;

        var mLat = gcjLat - dLat, mLon = gcjLon - dLon;

        var pLat = gcjLat + dLat, pLon = gcjLon + dLon;

        var wgsLat, wgsLon, i = 0;

        while (1) {

            wgsLat = (mLat + pLat) / 2;

            wgsLon = (mLon + pLon) / 2;

            var tmp = this.gcj_encrypt(wgsLat, wgsLon)

            dLat = tmp.lat - gcjLat;

            dLon = tmp.lon - 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;

        }

        //console.log(i);

        return {'lat': wgsLat, 'lon': wgsLon};

    },

    //GCJ-02 to BD-09

    bd_encrypt : function (gcjLat, gcjLon) {

        var x = gcjLon, 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); 

        bdLon = z * Math.cos(theta) + 0.0065; 

        bdLat = z * Math.sin(theta) + 0.006;

        return {'lat' : bdLat,'lon' : bdLon};

    },

    //BD-09 to GCJ-02

    bd_decrypt : function (bdLat, bdLon) {

        var x = bdLon - 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 gcjLon = z * Math.cos(theta); 

        var gcjLat = z * Math.sin(theta);

        return {'lat' : gcjLat, 'lon' : gcjLon};

    },

    //WGS-84 to Web mercator

    //mercatorLat -> y mercatorLon -> x

    mercator_encrypt : function(wgsLat, wgsLon) {

        var x = wgsLon * 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, 'lon' : x};

        /*

        if ((Math.abs(wgsLon) > 180 || Math.abs(wgsLat) > 90))

            return null;

        var x = 6378137.0 * wgsLon * 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, 'lon' : x};

        //*/

    },

    // Web mercator to WGS-84

    // mercatorLat -> y mercatorLon -> x

    mercator_decrypt : function(mercatorLat, mercatorLon) {

        var x = mercatorLon / 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, 'lon' : x};

        /*

        if (Math.abs(mercatorLon) < 180 && Math.abs(mercatorLat) < 90)

            return null;

        if ((Math.abs(mercatorLon) > 20037508.3427892) || (Math.abs(mercatorLat) > 20037508.3427892))

            return null;

        var a = mercatorLon / 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, 'lon' : x};

        //*/

    },

    // two point's distance

    distance : function (latA, lonA, latB, lonB) {

        var earthR = 6371000.;

        var x = Math.cos(latA * this.PI / 180.) * Math.cos(latB * this.PI / 180.) * Math.cos((lonA - lonB) * 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, lon) {

        if (lon < 72.004 || lon > 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;

    },

    transformLon : 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;

    }

};