var FORTPI = Math.PI/4;
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var srat = require('../common/srat');
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var HALF_PI = Math.PI/2;
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var MAX_ITER = 20;
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exports.init = function() {
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var sphi = Math.sin(this.lat0);
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var cphi = Math.cos(this.lat0);
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cphi *= cphi;
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this.rc = Math.sqrt(1 - this.es) / (1 - this.es * sphi * sphi);
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this.C = Math.sqrt(1 + this.es * cphi * cphi / (1 - this.es));
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this.phic0 = Math.asin(sphi / this.C);
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this.ratexp = 0.5 * this.C * this.e;
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this.K = Math.tan(0.5 * this.phic0 + FORTPI) / (Math.pow(Math.tan(0.5 * this.lat0 + FORTPI), this.C) * srat(this.e * sphi, this.ratexp));
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};
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exports.forward = function(p) {
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var lon = p.x;
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var lat = p.y;
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p.y = 2 * Math.atan(this.K * Math.pow(Math.tan(0.5 * lat + FORTPI), this.C) * srat(this.e * Math.sin(lat), this.ratexp)) - HALF_PI;
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p.x = this.C * lon;
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return p;
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};
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exports.inverse = function(p) {
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var DEL_TOL = 1e-14;
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var lon = p.x / this.C;
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var lat = p.y;
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var num = Math.pow(Math.tan(0.5 * lat + FORTPI) / this.K, 1 / this.C);
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for (var i = MAX_ITER; i > 0; --i) {
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lat = 2 * Math.atan(num * srat(this.e * Math.sin(p.y), - 0.5 * this.e)) - HALF_PI;
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if (Math.abs(lat - p.y) < DEL_TOL) {
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break;
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}
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p.y = lat;
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}
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/* convergence failed */
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if (!i) {
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return null;
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}
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p.x = lon;
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p.y = lat;
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return p;
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};
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exports.names = ["gauss"];
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