renaming folder edit_wp5_web_folder to map-service

[geo.git] / map-service / geo / mapviewer / proj4js / lib / projCode / cea.js

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+/*******************************************************************************
+NAME                    LAMBERT CYLINDRICAL EQUAL AREA
+
+PURPOSE:       Transforms input longitude and latitude to Easting and
+               Northing for the Lambert Cylindrical Equal Area projection.
+                This class of projection includes the Behrmann and 
+                Gall-Peters Projections.  The
+               longitude and latitude must be in radians.  The Easting
+               and Northing values will be returned in meters.
+
+PROGRAMMER              DATE            
+----------              ----
+R. Marsden              August 2009
+Winwaed Software Tech LLC, http://www.winwaed.com
+
+This function was adapted from the Miller Cylindrical Projection in the Proj4JS
+library.
+
+Note: This implementation assumes a Spherical Earth. The (commented) code 
+has been included for the ellipsoidal forward transform, but derivation of 
+the ellispoidal inverse transform is beyond me. Note that most of the 
+Proj4JS implementations do NOT currently support ellipsoidal figures. 
+Therefore this is not seen as a problem - especially this lack of support 
+is explicitly stated here.
+ 
+ALGORITHM REFERENCES
+
+1.  "Cartographic Projection Procedures for the UNIX Environment - 
+     A User's Manual" by Gerald I. Evenden, USGS Open File Report 90-284
+    and Release 4 Interim Reports (2003)
+
+2.  Snyder, John P., "Flattening the Earth - Two Thousand Years of Map 
+    Projections", Univ. Chicago Press, 1993
+*******************************************************************************/
+
+Proj4js.Proj.cea = {
+
+/* Initialize the Cylindrical Equal Area projection
+  -------------------------------------------*/
+  init: function() {
+    //no-op
+  },
+
+
+  /* Cylindrical Equal Area forward equations--mapping lat,long to x,y
+    ------------------------------------------------------------*/
+  forward: function(p) {
+    var lon=p.x;
+    var lat=p.y;
+    /* Forward equations
+      -----------------*/
+    dlon = Proj4js.common.adjust_lon(lon -this.long0);
+    var x = this.x0 + this.a * dlon * Math.cos(this.lat_ts);
+    var y = this.y0 + this.a * Math.sin(lat) / Math.cos(this.lat_ts);
+   /* Elliptical Forward Transform
+      Not implemented due to a lack of a matchign inverse function
+    {
+      var Sin_Lat = Math.sin(lat);
+      var Rn = this.a * (Math.sqrt(1.0e0 - this.es * Sin_Lat * Sin_Lat ));
+      x = this.x0 + this.a * dlon * Math.cos(this.lat_ts);
+      y = this.y0 + Rn * Math.sin(lat) / Math.cos(this.lat_ts);
+    }
+   */
+
+
+    p.x=x;
+    p.y=y;
+    return p;
+  },//ceaFwd()
+
+  /* Cylindrical Equal Area inverse equations--mapping x,y to lat/long
+    ------------------------------------------------------------*/
+  inverse: function(p) {
+    p.x -= this.x0;
+    p.y -= this.y0;
+
+    var lon = Proj4js.common.adjust_lon( this.long0 + (p.x / this.a) / Math.cos(this.lat_ts) );
+
+    var lat = Math.asin( (p.y/this.a) * Math.cos(this.lat_ts) );
+
+    p.x=lon;
+    p.y=lat;
+    return p;
+  }//ceaInv()
+};