gauss.js
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Proj4js.Proj.gauss = {
init : function() {
sphi = Math.sin(this.lat0);
cphi = Math.cos(this.lat0);
cphi *= cphi;
this.rc = Math.sqrt(1.0 - this.es) / (1.0 - this.es * sphi * sphi);
this.C = Math.sqrt(1.0 + this.es * cphi * cphi / (1.0 - this.es));
this.phic0 = Math.asin(sphi / this.C);
this.ratexp = 0.5 * this.C * this.e;
this.K = Math.tan(0.5 * this.phic0 + Proj4js.common.FORTPI) / (Math.pow(Math.tan(0.5*this.lat0 + Proj4js.common.FORTPI), this.C) * Proj4js.common.srat(this.e*sphi, this.ratexp));
},
forward : function(p) {
var lon = p.x;
var lat = p.y;
p.y = 2.0 * Math.atan( this.K * Math.pow(Math.tan(0.5 * lat + Proj4js.common.FORTPI), this.C) * Proj4js.common.srat(this.e * Math.sin(lat), this.ratexp) ) - Proj4js.common.HALF_PI;
p.x = this.C * lon;
return p;
},
inverse : function(p) {
var DEL_TOL = 1e-14;
var lon = p.x / this.C;
var lat = p.y;
num = Math.pow(Math.tan(0.5 * lat + Proj4js.common.FORTPI)/this.K, 1./this.C);
for (var i = Proj4js.common.MAX_ITER; i>0; --i) {
lat = 2.0 * Math.atan(num * Proj4js.common.srat(this.e * Math.sin(p.y), -0.5 * this.e)) - Proj4js.common.HALF_PI;
if (Math.abs(lat - p.y) < DEL_TOL) break;
p.y = lat;
}
/* convergence failed */
if (!i) {
Proj4js.reportError("gauss:inverse:convergence failed");
return null;
}
p.x = lon;
p.y = lat;
return p;
}
};