With review from elem, and oversight from tschaub, rolling in

SphericalMercator changes. Note that this explicitly does *not* include r4182 , so as to keep changes to a single logical set: that should be filed in a seperate bug if it can be reproduced against trunk after this commit. Hooray for Tim, thanks for all the feedback, onward and upward! (Closes #686) git-svn-id: http://svn.openlayers.org/trunk/openlayers@4221 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
2007-09-11 21:16:28 +00:00
parent d0aebc1a81
commit 0aba585bc0
13 changed files with 591 additions and 27 deletions
@@ -0,0 +1,107 @@
+/**
+ * @requires OpenLayers/Layer.js
+ *
+ * Class: OpenLayers.Layer.SphericalMercator
+ * A mixin for layers that wraps up the pieces neccesary to have a coordinate
+ *     conversion for working with commercial APIs which use a spherical
+ *     mercator projection.  Using this layer as a base layer, additional
+ *     layers can be used as overlays if they are in the same projection.
+ *
+ * A layer is given properties of this object by setting the sphericalMercator
+ *     property to true.
+ *
+ * More projection information:
+ *  - http://spatialreference.org/ref/user/google-projection/
+ *
+ * Proj4 Text:
+ *     +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0
+ *     +k=1.0 +units=m +nadgrids=@null +no_defs
+ *
+ * WKT:
+ *     900913=PROJCS["WGS84 / Simple Mercator", GEOGCS["WGS 84",
+ *     DATUM["WGS_1984", SPHEROID["WGS_1984", 6378137.0, 298.257223563]], 
+ *     PRIMEM["Greenwich", 0.0], UNIT["degree", 0.017453292519943295], 
+ *     AXIS["Longitude", EAST], AXIS["Latitude", NORTH]],
+ *     PROJECTION["Mercator_1SP_Google"], 
+ *     PARAMETER["latitude_of_origin", 0.0], PARAMETER["central_meridian", 0.0], 
+ *     PARAMETER["scale_factor", 1.0], PARAMETER["false_easting", 0.0], 
+ *     PARAMETER["false_northing", 0.0], UNIT["m", 1.0], AXIS["x", EAST],
+ *     AXIS["y", NORTH], AUTHORITY["EPSG","900913"]]
+ */
+OpenLayers.Layer.SphericalMercator = {
+
+    /**
+     * Method: getExtent
+     * Get the map's extent.
+     *
+     * Returns:
+     * {<OpenLayers.Bounds>} The map extent.
+     */
+    getExtent: function() {
+        var extent = null;
+        if (this.sphericalMercator) {
+            extent = this.map.calculateBounds();
+        } else {
+            extent = OpenLayers.Layer.FixedZoomLevels.prototype.getExtent.apply(this);
+        }
+        return extent;
+    },
+
+    /** 
+     * Method: initMercatorParameters 
+     * Set up the mercator parameters on the layer: resolutions,
+     *     projection, units.
+     */
+    initMercatorParameters: function() {
+        // set up properties for Mercator - assume EPSG:900913
+        this.RESOLUTIONS = [];
+        var maxResolution = 156543.0339;
+        for(var zoom=0; zoom<=this.MAX_ZOOM_LEVEL; ++zoom) {
+            this.RESOLUTIONS[zoom] = maxResolution / Math.pow(2, zoom);
+        }
+        this.units = "m";
+        this.projection = "EPSG:900913";
+    },
+
+    /**
+     * Method: forwardMercator
+     * Given a lon,lat in EPSG:4326, return a point in Spherical Mercator.
+     *
+     * Parameters:
+     * lon - {float} 
+     * lat - {float}
+     * 
+     * Returns:
+     * {<OpenLayers.LonLat>} The coordinates transformed to Mercator.
+     */
+    forwardMercator: function(lon, lat) {
+        var x = lon * 20037508.34 / 180;
+        var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
+
+        y = y * 20037508.34 / 180;
+        
+        return new OpenLayers.LonLat(x, y);
+    },
+
+    /**
+     * Method: inverseMercator
+     * Given a x,y in Spherical Mercator, return a point in EPSG:4326.
+     *
+     * Parameters:
+     * x - {float} A map x in Spherical Mercator.
+     * y - {float} A map y in Spherical Mercator.
+     * 
+     * Returns:
+     * {<OpenLayers.LonLat>} The coordinates transformed to EPSG:4326.
+     */
+    inverseMercator: function(x, y) {
+
+        var lon = (x / 20037508.34) * 180;
+        var lat = (y / 20037508.34) * 180;
+
+        lat = 180/Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180)) - Math.PI / 2);
+        
+        return new OpenLayers.LonLat(lon, lat);
+    }
+
+};