/*******************************************************************************
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NAME ORTHOGRAPHIC
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PURPOSE: Transforms input longitude and latitude to Easting and
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Northing for the Orthographic 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.ortho = {
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/* Initialize the Orthographic projection
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-------------------------------------*/
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init: function(def) {
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//double temp; /* temporary variable */
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/* Place parameters in static storage for common use
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-------------------------------------------------*/;
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this.sin_p14=Math.sin(this.lat0);
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this.cos_p14=Math.cos(this.lat0);
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},
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/* Orthographic forward equations--mapping lat,long to x,y
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---------------------------------------------------*/
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forward: function(p) {
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var sinphi, cosphi; /* sin and cos value */
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var dlon; /* delta longitude value */
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var coslon; /* cos of longitude */
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var ksp; /* scale factor */
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var g;
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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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dlon = Proj4js.common.adjust_lon(lon - this.long0);
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sinphi=Math.sin(lat);
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cosphi=Math.cos(lat);
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coslon = Math.cos(dlon);
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g = this.sin_p14 * sinphi + this.cos_p14 * cosphi * coslon;
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ksp = 1.0;
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if ((g > 0) || (Math.abs(g) <= Proj4js.common.EPSLN)) {
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var x = this.a * ksp * cosphi * Math.sin(dlon);
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var y = this.y0 + this.a * ksp * (this.cos_p14 * sinphi - this.sin_p14 * cosphi * coslon);
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} else {
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Proj4js.reportError("orthoFwdPointError");
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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 rh; /* height above ellipsoid */
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var z; /* angle */
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var sinz,cosz; /* sin of z and cos of z */
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var temp;
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var con;
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var lon , lat;
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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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rh = Math.sqrt(p.x * p.x + p.y * p.y);
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if (rh > this.a + .0000001) {
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Proj4js.reportError("orthoInvDataError");
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}
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z = Proj4js.common.asinz(rh / this.a);
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sinz=Math.sin(z);
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cosz=Math.cos(z);
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lon = this.long0;
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if (Math.abs(rh) <= Proj4js.common.EPSLN) {
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lat = this.lat0;
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}
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lat = Proj4js.common.asinz(cosz * this.sin_p14 + (p.y * sinz * this.cos_p14)/rh);
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con = Math.abs(this.lat0) - Proj4js.common.HALF_PI;
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if (Math.abs(con) <= Proj4js.common.EPSLN) {
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if (this.lat0 >= 0) {
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lon = Proj4js.common.adjust_lon(this.long0 + Math.atan2(p.x, -p.y));
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} else {
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lon = Proj4js.common.adjust_lon(this.long0 -Math.atan2(-p.x, p.y));
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}
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}
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con = cosz - this.sin_p14 * Math.sin(lat);
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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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