/*******************************************************************************
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NAME EQUIDISTANT CONIC
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PURPOSE: Transforms input longitude and latitude to Easting and Northing
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for the Equidistant Conic projection. The longitude and
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latitude must be in radians. The Easting and Northing values
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will be returned in meters.
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PROGRAMMER DATE
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---------- ----
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T. Mittan Mar, 1993
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ALGORITHM REFERENCES
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1. Snyder, John P., "Map Projections--A Working Manual", U.S. Geological
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Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
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State Government Printing Office, Washington D.C., 1987.
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2. Snyder, John P. and Voxland, Philip M., "An Album of Map Projections",
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U.S. Geological Survey Professional Paper 1453 , United State Government
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Printing Office, Washington D.C., 1989.
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*******************************************************************************/
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/* Variables common to all subroutines in this code file
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-----------------------------------------------------*/
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Proj4js.Proj.eqdc = {
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/* Initialize the Equidistant Conic projection
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------------------------------------------*/
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init: function() {
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/* Place parameters in static storage for common use
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-------------------------------------------------*/
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if(!this.mode) this.mode=0;//chosen default mode
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this.temp = this.b / this.a;
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this.es = 1.0 - Math.pow(this.temp,2);
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this.e = Math.sqrt(this.es);
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this.e0 = Proj4js.common.e0fn(this.es);
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this.e1 = Proj4js.common.e1fn(this.es);
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this.e2 = Proj4js.common.e2fn(this.es);
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this.e3 = Proj4js.common.e3fn(this.es);
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this.sinphi=Math.sin(this.lat1);
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this.cosphi=Math.cos(this.lat1);
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this.ms1 = Proj4js.common.msfnz(this.e,this.sinphi,this.cosphi);
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this.ml1 = Proj4js.common.mlfn(this.e0, this.e1, this.e2,this.e3, this.lat1);
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/* format B
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---------*/
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if (this.mode != 0) {
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if (Math.abs(this.lat1 + this.lat2) < Proj4js.common.EPSLN) {
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Proj4js.reportError("eqdc:Init:EqualLatitudes");
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//return(81);
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}
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this.sinphi=Math.sin(this.lat2);
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this.cosphi=Math.cos(this.lat2);
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this.ms2 = Proj4js.common.msfnz(this.e,this.sinphi,this.cosphi);
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this.ml2 = Proj4js.common.mlfn(this.e0, this.e1, this.e2, this.e3, this.lat2);
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if (Math.abs(this.lat1 - this.lat2) >= Proj4js.common.EPSLN) {
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this.ns = (this.ms1 - this.ms2) / (this.ml2 - this.ml1);
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} else {
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this.ns = this.sinphi;
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}
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} else {
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this.ns = this.sinphi;
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}
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this.g = this.ml1 + this.ms1/this.ns;
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this.ml0 = Proj4js.common.mlfn(this.e0, this.e1,this. e2, this.e3, this.lat0);
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this.rh = this.a * (this.g - this.ml0);
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},
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/* Equidistant Conic forward equations--mapping lat,long to x,y
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-----------------------------------------------------------*/
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forward: function(p) {
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var lon=p.x;
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var lat=p.y;
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/* Forward equations
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-----------------*/
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var ml = Proj4js.common.mlfn(this.e0, this.e1, this.e2, this.e3, lat);
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var rh1 = this.a * (this.g - ml);
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var theta = this.ns * Proj4js.common.adjust_lon(lon - this.long0);
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var x = this.x0 + rh1 * Math.sin(theta);
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var y = this.y0 + this.rh - rh1 * Math.cos(theta);
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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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/* Inverse equations
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-----------------*/
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inverse: function(p) {
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p.x -= this.x0;
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p.y = this.rh - p.y + this.y0;
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var con, rh1;
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if (this.ns >= 0) {
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rh1 = Math.sqrt(p.x *p.x + p.y * p.y);
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con = 1.0;
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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 = -1.0;
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}
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var theta = 0.0;
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if (rh1 != 0.0) theta = Math.atan2(con *p.x, con *p.y);
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var ml = this.g - rh1 /this.a;
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var lat = this.phi3z(ml,this.e0,this.e1,this.e2,this.e3);
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var lon = Proj4js.common.adjust_lon(this.long0 + theta / this.ns);
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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 latitude, phi3, for the inverse of the Equidistant
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Conic projection.
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-----------------------------------------------------------------*/
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phi3z: function(ml,e0,e1,e2,e3) {
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var phi;
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var dphi;
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phi = ml;
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for (var i = 0; i < 15; i++) {
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dphi = (ml + e1 * Math.sin(2.0 * phi) - e2 * Math.sin(4.0 * phi) + e3 * Math.sin(6.0 * phi))/ e0 - phi;
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phi += dphi;
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if (Math.abs(dphi) <= .0000000001) {
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return phi;
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}
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}
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Proj4js.reportError("PHI3Z-CONV:Latitude failed to converge after 15 iterations");
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return null;
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}
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};
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