var mlfn = require('../common/mlfn');
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var e0fn = require('../common/e0fn');
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var e1fn = require('../common/e1fn');
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var e2fn = require('../common/e2fn');
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var e3fn = require('../common/e3fn');
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var gN = require('../common/gN');
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var adjust_lon = require('../common/adjust_lon');
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var adjust_lat = require('../common/adjust_lat');
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var imlfn = require('../common/imlfn');
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var HALF_PI = Math.PI/2;
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var EPSLN = 1.0e-10;
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exports.init = function() {
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if (!this.sphere) {
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this.e0 = e0fn(this.es);
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this.e1 = e1fn(this.es);
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this.e2 = e2fn(this.es);
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this.e3 = e3fn(this.es);
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this.ml0 = this.a * mlfn(this.e0, this.e1, this.e2, this.e3, this.lat0);
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}
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};
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/* Cassini forward equations--mapping lat,long to x,y
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-----------------------------------------------------------------------*/
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exports.forward = function(p) {
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/* Forward equations
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-----------------*/
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var x, y;
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var lam = p.x;
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var phi = p.y;
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lam = adjust_lon(lam - this.long0);
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if (this.sphere) {
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x = this.a * Math.asin(Math.cos(phi) * Math.sin(lam));
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y = this.a * (Math.atan2(Math.tan(phi), Math.cos(lam)) - this.lat0);
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}
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else {
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//ellipsoid
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var sinphi = Math.sin(phi);
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var cosphi = Math.cos(phi);
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var nl = gN(this.a, this.e, sinphi);
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var tl = Math.tan(phi) * Math.tan(phi);
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var al = lam * Math.cos(phi);
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var asq = al * al;
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var cl = this.es * cosphi * cosphi / (1 - this.es);
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var ml = this.a * mlfn(this.e0, this.e1, this.e2, this.e3, phi);
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x = nl * al * (1 - asq * tl * (1 / 6 - (8 - tl + 8 * cl) * asq / 120));
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y = ml - this.ml0 + nl * sinphi / cosphi * asq * (0.5 + (5 - tl + 6 * cl) * asq / 24);
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}
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p.x = x + this.x0;
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p.y = y + this.y0;
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return p;
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};
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/* Inverse equations
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-----------------*/
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exports.inverse = function(p) {
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p.x -= this.x0;
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p.y -= this.y0;
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var x = p.x / this.a;
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var y = p.y / this.a;
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var phi, lam;
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if (this.sphere) {
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var dd = y + this.lat0;
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phi = Math.asin(Math.sin(dd) * Math.cos(x));
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lam = Math.atan2(Math.tan(x), Math.cos(dd));
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}
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else {
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/* ellipsoid */
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var ml1 = this.ml0 / this.a + y;
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var phi1 = imlfn(ml1, this.e0, this.e1, this.e2, this.e3);
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if (Math.abs(Math.abs(phi1) - HALF_PI) <= EPSLN) {
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p.x = this.long0;
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p.y = HALF_PI;
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if (y < 0) {
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p.y *= -1;
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}
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return p;
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}
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var nl1 = gN(this.a, this.e, Math.sin(phi1));
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var rl1 = nl1 * nl1 * nl1 / this.a / this.a * (1 - this.es);
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var tl1 = Math.pow(Math.tan(phi1), 2);
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var dl = x * this.a / nl1;
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var dsq = dl * dl;
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phi = phi1 - nl1 * Math.tan(phi1) / rl1 * dl * dl * (0.5 - (1 + 3 * tl1) * dl * dl / 24);
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lam = dl * (1 - dsq * (tl1 / 3 + (1 + 3 * tl1) * tl1 * dsq / 15)) / Math.cos(phi1);
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}
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p.x = adjust_lon(lam + this.long0);
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p.y = adjust_lat(phi);
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return p;
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};
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exports.names = ["Cassini", "Cassini_Soldner", "cass"];
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