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;
}
};
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