/*******************************************************************************
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NAME SINUSOIDAL
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PURPOSE: Transforms input longitude and latitude to Easting and
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Northing for the Sinusoidal 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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D. Steinwand, EROS May, 1991
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This function was adapted from the Sinusoidal projection code (FORTRAN) in the
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General Cartographic Transformation Package software which is available from
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the U.S. Geological Survey National Mapping Division.
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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. "Software Documentation for GCTP General Cartographic Transformation
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Package", U.S. Geological Survey National Mapping Division, May 1982.
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*******************************************************************************/
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Proj4js.Proj.sinu = {
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/* Initialize the Sinusoidal 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.sphere) {
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this.en = Proj4js.common.pj_enfn(this.es);
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} else {
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this.n = 1.;
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this.m = 0.;
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this.es = 0;
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this.C_y = Math.sqrt((this.m + 1.) / this.n);
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this.C_x = this.C_y/(this.m + 1.);
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}
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},
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/* Sinusoidal forward equations--mapping lat,long to x,y
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-----------------------------------------------------*/
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forward: function(p) {
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var x,y,delta_lon;
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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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lon = Proj4js.common.adjust_lon(lon - this.long0);
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if (this.sphere) {
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if (!this.m) {
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lat = this.n != 1. ? Math.asin(this.n * Math.sin(lat)): lat;
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} else {
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var k = this.n * Math.sin(lat);
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for (var i = Proj4js.common.MAX_ITER; i ; --i) {
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var V = (this.m * lat + Math.sin(lat) - k) / (this.m + Math.cos(lat));
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lat -= V;
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if (Math.abs(V) < Proj4js.common.EPSLN) break;
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}
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}
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x = this.a * this.C_x * lon * (this.m + Math.cos(lat));
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y = this.a * this.C_y * lat;
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} else {
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var s = Math.sin(lat);
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var c = Math.cos(lat);
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y = this.a * Proj4js.common.pj_mlfn(lat, s, c, this.en);
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x = this.a * lon * c / Math.sqrt(1. - this.es * s * s);
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}
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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: function(p) {
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var lat,temp,lon;
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/* Inverse equations
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-----------------*/
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p.x -= this.x0;
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p.y -= this.y0;
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lat = p.y / this.a;
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if (this.sphere) {
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p.y /= this.C_y;
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lat = this.m ? Math.asin((this.m * p.y + Math.sin(p.y)) / this.n) :
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( this.n != 1. ? Math.asin(Math.sin(p.y) / this.n) : p.y );
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lon = p.x / (this.C_x * (this.m + Math.cos(p.y)));
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} else {
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lat = Proj4js.common.pj_inv_mlfn(p.y/this.a, this.es, this.en)
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var s = Math.abs(lat);
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if (s < Proj4js.common.HALF_PI) {
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s = Math.sin(lat);
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temp = this.long0 + p.x * Math.sqrt(1. - this.es * s * s) /(this.a * Math.cos(lat));
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//temp = this.long0 + p.x / (this.a * Math.cos(lat));
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lon = Proj4js.common.adjust_lon(temp);
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} else if ((s - Proj4js.common.EPSLN) < Proj4js.common.HALF_PI) {
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lon = this.long0;
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}
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}
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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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};
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