ed3221441c
completes an important blocker for moving forward with OSGeo incubation. git-svn-id: http://svn.openlayers.org/trunk/openlayers@4985 dc9f47b5-9b13-0410-9fdd-eb0c1a62fdaf
107 lines
3.4 KiB
JavaScript
107 lines
3.4 KiB
JavaScript
/** @requires OpenLayers/Layer.js
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*
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* Class: OpenLayers.Layer.SphericalMercator
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* A mixin for layers that wraps up the pieces neccesary to have a coordinate
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* conversion for working with commercial APIs which use a spherical
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* mercator projection. Using this layer as a base layer, additional
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* layers can be used as overlays if they are in the same projection.
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*
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* A layer is given properties of this object by setting the sphericalMercator
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* property to true.
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*
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* More projection information:
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* - http://spatialreference.org/ref/user/google-projection/
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*
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* Proj4 Text:
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* +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0
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* +k=1.0 +units=m +nadgrids=@null +no_defs
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*
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* WKT:
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* 900913=PROJCS["WGS84 / Simple Mercator", GEOGCS["WGS 84",
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* DATUM["WGS_1984", SPHEROID["WGS_1984", 6378137.0, 298.257223563]],
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* PRIMEM["Greenwich", 0.0], UNIT["degree", 0.017453292519943295],
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* AXIS["Longitude", EAST], AXIS["Latitude", NORTH]],
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* PROJECTION["Mercator_1SP_Google"],
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* PARAMETER["latitude_of_origin", 0.0], PARAMETER["central_meridian", 0.0],
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* PARAMETER["scale_factor", 1.0], PARAMETER["false_easting", 0.0],
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* PARAMETER["false_northing", 0.0], UNIT["m", 1.0], AXIS["x", EAST],
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* AXIS["y", NORTH], AUTHORITY["EPSG","900913"]]
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*/
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OpenLayers.Layer.SphericalMercator = {
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/**
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* Method: getExtent
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* Get the map's extent.
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*
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* Returns:
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* {<OpenLayers.Bounds>} The map extent.
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*/
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getExtent: function() {
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var extent = null;
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if (this.sphericalMercator) {
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extent = this.map.calculateBounds();
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} else {
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extent = OpenLayers.Layer.FixedZoomLevels.prototype.getExtent.apply(this);
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}
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return extent;
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},
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/**
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* Method: initMercatorParameters
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* Set up the mercator parameters on the layer: resolutions,
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* projection, units.
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*/
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initMercatorParameters: function() {
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// set up properties for Mercator - assume EPSG:900913
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this.RESOLUTIONS = [];
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var maxResolution = 156543.0339;
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for(var zoom=0; zoom<=this.MAX_ZOOM_LEVEL; ++zoom) {
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this.RESOLUTIONS[zoom] = maxResolution / Math.pow(2, zoom);
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}
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this.units = "m";
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this.projection = "EPSG:900913";
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},
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/**
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* Method: forwardMercator
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* Given a lon,lat in EPSG:4326, return a point in Spherical Mercator.
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*
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* Parameters:
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* lon - {float}
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* lat - {float}
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*
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* Returns:
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* {<OpenLayers.LonLat>} The coordinates transformed to Mercator.
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*/
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forwardMercator: function(lon, lat) {
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var x = lon * 20037508.34 / 180;
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var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
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y = y * 20037508.34 / 180;
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return new OpenLayers.LonLat(x, y);
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},
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/**
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* Method: inverseMercator
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* Given a x,y in Spherical Mercator, return a point in EPSG:4326.
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*
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* Parameters:
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* x - {float} A map x in Spherical Mercator.
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* y - {float} A map y in Spherical Mercator.
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*
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* Returns:
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* {<OpenLayers.LonLat>} The coordinates transformed to EPSG:4326.
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*/
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inverseMercator: function(x, y) {
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var lon = (x / 20037508.34) * 180;
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var lat = (y / 20037508.34) * 180;
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lat = 180/Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180)) - Math.PI / 2);
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return new OpenLayers.LonLat(lon, lat);
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}
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};
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