微信小程序地圖定位GPS轉騰訊地圖的坐標系

參考：
http://www.qchcloud.cn/tn/article/23
參考

//s
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: 衛星橢球坐標投影到平面地圖坐標系的投影因子。
var ee = 0.00669342162296594323; // ee: 橢球的偏心率。
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;
 }

};

//e