/** * @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);    }};