/*******************************************************************************
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NAME EQUIRECTANGULAR
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PURPOSE: Transforms input longitude and latitude to Easting and
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Northing for the Equirectangular projection. The
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longitude and latitude must be in radians. The Easting
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and Northing values 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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Proj4js.Proj.equi = {
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init: function() {
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if(!this.x0) this.x0=0;
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if(!this.y0) this.y0=0;
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if(!this.lat0) this.lat0=0;
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if(!this.long0) this.long0=0;
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///this.t2;
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},
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/* Equirectangular 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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var dlon = Proj4js.common.adjust_lon(lon - this.long0);
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var x = this.x0 +this. a * dlon *Math.cos(this.lat0);
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var y = this.y0 + this.a * lat;
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this.t1=x;
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this.t2=Math.cos(this.lat0);
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p.x=x;
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p.y=y;
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return p;
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}, //equiFwd()
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/* Equirectangular inverse equations--mapping x,y to lat/long
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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.y0;
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var lat = p.y /this. a;
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if ( Math.abs(lat) > Proj4js.common.HALF_PI) {
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Proj4js.reportError("equi:Inv:DataError");
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}
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var lon = Proj4js.common.adjust_lon(this.long0 + p.x / (this.a * Math.cos(this.lat0)));
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p.x=lon;
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p.y=lat;
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}//equiInv()
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};
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