var EPSLN = 1.0e-10;
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var msfnz = require('../common/msfnz');
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var qsfnz = require('../common/qsfnz');
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var adjust_lon = require('../common/adjust_lon');
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var asinz = require('../common/asinz');
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exports.init = function() {
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if (Math.abs(this.lat1 + this.lat2) < EPSLN) {
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return;
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}
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this.temp = this.b / this.a;
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this.es = 1 - Math.pow(this.temp, 2);
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this.e3 = Math.sqrt(this.es);
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this.sin_po = Math.sin(this.lat1);
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this.cos_po = Math.cos(this.lat1);
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this.t1 = this.sin_po;
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this.con = this.sin_po;
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this.ms1 = msfnz(this.e3, this.sin_po, this.cos_po);
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this.qs1 = qsfnz(this.e3, this.sin_po, this.cos_po);
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this.sin_po = Math.sin(this.lat2);
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this.cos_po = Math.cos(this.lat2);
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this.t2 = this.sin_po;
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this.ms2 = msfnz(this.e3, this.sin_po, this.cos_po);
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this.qs2 = qsfnz(this.e3, this.sin_po, this.cos_po);
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this.sin_po = Math.sin(this.lat0);
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this.cos_po = Math.cos(this.lat0);
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this.t3 = this.sin_po;
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this.qs0 = qsfnz(this.e3, this.sin_po, this.cos_po);
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if (Math.abs(this.lat1 - this.lat2) > EPSLN) {
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this.ns0 = (this.ms1 * this.ms1 - this.ms2 * this.ms2) / (this.qs2 - this.qs1);
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}
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else {
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this.ns0 = this.con;
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}
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this.c = this.ms1 * this.ms1 + this.ns0 * this.qs1;
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this.rh = this.a * Math.sqrt(this.c - this.ns0 * this.qs0) / this.ns0;
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};
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/* Albers Conical Equal Area forward equations--mapping lat,long to x,y
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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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this.sin_phi = Math.sin(lat);
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this.cos_phi = Math.cos(lat);
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var qs = qsfnz(this.e3, this.sin_phi, this.cos_phi);
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var rh1 = this.a * Math.sqrt(this.c - this.ns0 * qs) / this.ns0;
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var theta = this.ns0 * adjust_lon(lon - this.long0);
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var x = rh1 * Math.sin(theta) + this.x0;
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var y = this.rh - rh1 * Math.cos(theta) + this.y0;
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p.x = x;
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p.y = y;
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return p;
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};
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exports.inverse = function(p) {
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var rh1, qs, con, theta, lon, lat;
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p.x -= this.x0;
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p.y = this.rh - p.y + this.y0;
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if (this.ns0 >= 0) {
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rh1 = Math.sqrt(p.x * p.x + p.y * p.y);
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con = 1;
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}
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else {
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rh1 = -Math.sqrt(p.x * p.x + p.y * p.y);
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con = -1;
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}
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theta = 0;
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if (rh1 !== 0) {
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theta = Math.atan2(con * p.x, con * p.y);
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}
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con = rh1 * this.ns0 / this.a;
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if (this.sphere) {
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lat = Math.asin((this.c - con * con) / (2 * this.ns0));
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}
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else {
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qs = (this.c - con * con) / this.ns0;
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lat = this.phi1z(this.e3, qs);
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}
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lon = adjust_lon(theta / this.ns0 + this.long0);
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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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/* Function to compute phi1, the latitude for the inverse of the
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Albers Conical Equal-Area projection.
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-------------------------------------------*/
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exports.phi1z = function(eccent, qs) {
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var sinphi, cosphi, con, com, dphi;
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var phi = asinz(0.5 * qs);
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if (eccent < EPSLN) {
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return phi;
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}
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var eccnts = eccent * eccent;
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for (var i = 1; i <= 25; i++) {
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sinphi = Math.sin(phi);
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cosphi = Math.cos(phi);
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con = eccent * sinphi;
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com = 1 - con * con;
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dphi = 0.5 * com * com / cosphi * (qs / (1 - eccnts) - sinphi / com + 0.5 / eccent * Math.log((1 - con) / (1 + con)));
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phi = phi + dphi;
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if (Math.abs(dphi) <= 1e-7) {
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return phi;
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}
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}
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return null;
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};
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exports.names = ["Albers_Conic_Equal_Area", "Albers", "aea"];
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