text: /*******************************************************************************
  NAME                  		SINUSOIDAL
  
  PURPOSE:	Transforms input longitude and latitude to Easting and
  		Northing for the Sinusoidal projection.  The
  		longitude and latitude must be in radians.  The Easting
  		and Northing values will be returned in meters.
  
  PROGRAMMER              DATE            
  ----------              ----           
  D. Steinwand, EROS      May, 1991     
  
  This function was adapted from the Sinusoidal projection code (FORTRAN) in the 
  General Cartographic Transformation Package software which is available from 
  the U.S. Geological Survey National Mapping Division.
   
  ALGORITHM REFERENCES
  
  1.  Snyder, John P., "Map Projections--A Working Manual", U.S. Geological
      Survey Professional Paper 1395 (Supersedes USGS Bulletin 1532), United
      State Government Printing Office, Washington D.C., 1987.
  
  2.  "Software Documentation for GCTP General Cartographic Transformation
      Package", U.S. Geological Survey National Mapping Division, May 1982.
  *******************************************************************************/
  
  Proj4js.Proj.sinu = {
  
  	/* Initialize the Sinusoidal projection
  	  ------------------------------------*/
  	init: function() {
  		/* Place parameters in static storage for common use
  		  -------------------------------------------------*/
  		  
  
  		if (!this.sphere) {
  		  this.en = Proj4js.common.pj_enfn(this.es);
      } else {
        this.n = 1.;
        this.m = 0.;
        this.es = 0;
        this.C_y = Math.sqrt((this.m + 1.) / this.n);
        this.C_x = this.C_y/(this.m + 1.);
      }
  		  
  	},
  
  	/* Sinusoidal forward equations--mapping lat,long to x,y
  	-----------------------------------------------------*/
  	forward: function(p) {
  		var x,y,delta_lon;	
  		var lon=p.x;
  		var lat=p.y;	
  		/* Forward equations
  		-----------------*/
  		lon = Proj4js.common.adjust_lon(lon - this.long0);
  		
  		if (this.sphere) {
        if (!this.m) {
          lat = this.n != 1. ? Math.asin(this.n * Math.sin(lat)): lat;
        } else {
          var k = this.n * Math.sin(lat);
          for (var i = Proj4js.common.MAX_ITER; i ; --i) {
            var V = (this.m * lat + Math.sin(lat) - k) / (this.m + Math.cos(lat));
            lat -= V;
            if (Math.abs(V) < Proj4js.common.EPSLN) break;
          }
        }
        x = this.a * this.C_x * lon * (this.m + Math.cos(lat));
        y = this.a * this.C_y * lat;
  
  		} else {
  		  
  		  var s = Math.sin(lat);
  		  var c = Math.cos(lat);
        y = this.a * Proj4js.common.pj_mlfn(lat, s, c, this.en);
        x = this.a * lon * c / Math.sqrt(1. - this.es * s * s);
  		}
  
  		p.x=x;
  		p.y=y;	
  		return p;
  	},
  
  	inverse: function(p) {
  		var lat,temp,lon;	
  		
  		/* Inverse equations
  		  -----------------*/
  		p.x -= this.x0;
  		p.y -= this.y0;
  		lat = p.y / this.a;
  		
  		if (this.sphere) {
  		  
        p.y /= this.C_y;
        lat = this.m ? Math.asin((this.m * p.y + Math.sin(p.y)) / this.n) :
          ( this.n != 1. ? Math.asin(Math.sin(p.y) / this.n) : p.y );
        lon = p.x / (this.C_x * (this.m + Math.cos(p.y)));
  		  
  		} else {
  		  lat = Proj4js.common.pj_inv_mlfn(p.y/this.a, this.es, this.en)
  		  var s = Math.abs(lat);
        if (s < Proj4js.common.HALF_PI) {
          s = Math.sin(lat);
          temp = this.long0 + p.x * Math.sqrt(1. - this.es * s * s) /(this.a * Math.cos(lat));
          //temp = this.long0 + p.x / (this.a * Math.cos(lat));
          lon = Proj4js.common.adjust_lon(temp);
        } else if ((s - Proj4js.common.EPSLN) < Proj4js.common.HALF_PI) {
          lon = this.long0;
        }
  		  
  		}
  		  
  		p.x=lon;
  		p.y=lat;
  		return p;
  	}
  };
  
  
  