GPS坐标转换（JS）

var GPS = {
PI: 3.14159265358979324,
x_pi: 3.14159265358979324 * 3000.0 / 180.0,
delta: function (lat, lon)
{
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 };
},
// 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 };
},
// 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;
}
};