/*******************************************************************************
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NAME SWISS OBLIQUE MERCATOR
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PURPOSE: Swiss projection.
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WARNING: X and Y are inverted (weird) in the swiss coordinate system. Not
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here, since we want X to be horizontal and Y vertical.
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ALGORITHM REFERENCES
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1. "Formules et constantes pour le Calcul pour la
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projection cylindrique conforme à axe oblique et pour la transformation entre
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des systèmes de référence".
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http://www.swisstopo.admin.ch/internet/swisstopo/fr/home/topics/survey/sys/refsys/switzerland.parsysrelated1.31216.downloadList.77004.DownloadFile.tmp/swissprojectionfr.pdf
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*******************************************************************************/
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Proj4js.Proj.somerc = {
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init: function() {
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var phy0 = this.lat0;
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this.lambda0 = this.long0;
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var sinPhy0 = Math.sin(phy0);
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var semiMajorAxis = this.a;
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var invF = this.rf;
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var flattening = 1 / invF;
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var e2 = 2 * flattening - Math.pow(flattening, 2);
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var e = this.e = Math.sqrt(e2);
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this.R = this.k0 * semiMajorAxis * Math.sqrt(1 - e2) / (1 - e2 * Math.pow(sinPhy0, 2.0));
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this.alpha = Math.sqrt(1 + e2 / (1 - e2) * Math.pow(Math.cos(phy0), 4.0));
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this.b0 = Math.asin(sinPhy0 / this.alpha);
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this.K = Math.log(Math.tan(Math.PI / 4.0 + this.b0 / 2.0))
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- this.alpha
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* Math.log(Math.tan(Math.PI / 4.0 + phy0 / 2.0))
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+ this.alpha
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* e / 2
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* Math.log((1 + e * sinPhy0)
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/ (1 - e * sinPhy0));
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},
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forward: function(p) {
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var Sa1 = Math.log(Math.tan(Math.PI / 4.0 - p.y / 2.0));
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var Sa2 = this.e / 2.0
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* Math.log((1 + this.e * Math.sin(p.y))
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/ (1 - this.e * Math.sin(p.y)));
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var S = -this.alpha * (Sa1 + Sa2) + this.K;
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// spheric latitude
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var b = 2.0 * (Math.atan(Math.exp(S)) - Math.PI / 4.0);
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// spheric longitude
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var I = this.alpha * (p.x - this.lambda0);
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// psoeudo equatorial rotation
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var rotI = Math.atan(Math.sin(I)
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/ (Math.sin(this.b0) * Math.tan(b) +
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Math.cos(this.b0) * Math.cos(I)));
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var rotB = Math.asin(Math.cos(this.b0) * Math.sin(b) -
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Math.sin(this.b0) * Math.cos(b) * Math.cos(I));
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p.y = this.R / 2.0
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* Math.log((1 + Math.sin(rotB)) / (1 - Math.sin(rotB)))
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+ this.y0;
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p.x = this.R * rotI + this.x0;
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return p;
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},
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inverse: function(p) {
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var Y = p.x - this.x0;
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var X = p.y - this.y0;
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var rotI = Y / this.R;
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var rotB = 2 * (Math.atan(Math.exp(X / this.R)) - Math.PI / 4.0);
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var b = Math.asin(Math.cos(this.b0) * Math.sin(rotB)
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+ Math.sin(this.b0) * Math.cos(rotB) * Math.cos(rotI));
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var I = Math.atan(Math.sin(rotI)
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/ (Math.cos(this.b0) * Math.cos(rotI) - Math.sin(this.b0)
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* Math.tan(rotB)));
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var lambda = this.lambda0 + I / this.alpha;
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var S = 0.0;
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var phy = b;
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var prevPhy = -1000.0;
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var iteration = 0;
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while (Math.abs(phy - prevPhy) > 0.0000001)
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{
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if (++iteration > 20)
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{
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Proj4js.reportError("omercFwdInfinity");
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return;
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}
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//S = Math.log(Math.tan(Math.PI / 4.0 + phy / 2.0));
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S = 1.0
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/ this.alpha
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* (Math.log(Math.tan(Math.PI / 4.0 + b / 2.0)) - this.K)
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+ this.e
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* Math.log(Math.tan(Math.PI / 4.0
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+ Math.asin(this.e * Math.sin(phy))
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/ 2.0));
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prevPhy = phy;
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phy = 2.0 * Math.atan(Math.exp(S)) - Math.PI / 2.0;
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}
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p.x = lambda;
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p.y = phy;
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return p;
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}
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};
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