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/* Copyright (c) 2006-2013 by OpenLayers Contributors (see authors.txt for
* full list of contributors). Published under the 2-clause BSD license.
* See license.txt in the OpenLayers distribution or repository for the
* full text of the license. */
/**
* @requires OpenLayers/Layer.js
* @requires OpenLayers/Projection.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: getLonLatFromViewPortPx
* Get a map location from a pixel location
*
* Parameters:
* viewPortPx - {<OpenLayers.Pixel>}
*
* Returns:
* {<OpenLayers.LonLat>} An OpenLayers.LonLat which is the passed-in view
* port OpenLayers.Pixel, translated into lon/lat by map lib
* If the map lib is not loaded or not centered, returns null
*/
getLonLatFromViewPortPx: function (viewPortPx) {
return OpenLayers.Layer.prototype.getLonLatFromViewPortPx.apply(this, arguments);
},
/**
* Method: getViewPortPxFromLonLat
* Get a pixel location from a map location
*
* Parameters:
* lonlat - {<OpenLayers.LonLat>}
*
* Returns:
* {<OpenLayers.Pixel>} An OpenLayers.Pixel which is the passed-in
* OpenLayers.LonLat, translated into view port pixels by map lib
* If map lib is not loaded or not centered, returns null
*/
getViewPortPxFromLonLat: function (lonlat) {
return OpenLayers.Layer.prototype.getViewPortPxFromLonLat.apply(this, arguments);
},
/**
* 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 = 156543.03390625;
for(var zoom=0; zoom<=this.MAX_ZOOM_LEVEL; ++zoom) {
this.RESOLUTIONS[zoom] = maxResolution / Math.pow(2, zoom);
}
this.units = "m";
this.projection = this.projection || "EPSG:900913";
},
/**
* APIMethod: 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() {
var gg = new OpenLayers.Projection("EPSG:4326");
var sm = new OpenLayers.Projection("EPSG:900913");
return function(lon, lat) {
var point = OpenLayers.Projection.transform({x: lon, y: lat}, gg, sm);
return new OpenLayers.LonLat(point.x, point.y);
};
})(),
/**
* APIMethod: 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() {
var gg = new OpenLayers.Projection("EPSG:4326");
var sm = new OpenLayers.Projection("EPSG:900913");
return function(x, y) {
var point = OpenLayers.Projection.transform({x: x, y: y}, sm, gg);
return new OpenLayers.LonLat(point.x, point.y);
};
})()
};
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