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source: trunk/workshop-routing-foss4g/web/OpenLayers/lib/OpenLayers/Layer/SphericalMercator.js @ 76

Revision 76, 6.5 KB checked in by djay, 12 years ago (diff)

Ajout du répertoire web

  • Property svn:executable set to *
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1/* Copyright (c) 2006-2010 by OpenLayers Contributors (see authors.txt for
2 * full list of contributors). Published under the Clear BSD license. 
3 * See http://svn.openlayers.org/trunk/openlayers/license.txt for the
4 * full text of the license. */
5
6/**
7 * @requires OpenLayers/Layer.js
8 * @requires OpenLayers/Projection.js
9 */
10
11/**
12 * Class: OpenLayers.Layer.SphericalMercator
13 * A mixin for layers that wraps up the pieces neccesary to have a coordinate
14 *     conversion for working with commercial APIs which use a spherical
15 *     mercator projection.  Using this layer as a base layer, additional
16 *     layers can be used as overlays if they are in the same projection.
17 *
18 * A layer is given properties of this object by setting the sphericalMercator
19 *     property to true.
20 *
21 * More projection information:
22 *  - http://spatialreference.org/ref/user/google-projection/
23 *
24 * Proj4 Text:
25 *     +proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0
26 *     +k=1.0 +units=m +nadgrids=@null +no_defs
27 *
28 * WKT:
29 *     900913=PROJCS["WGS84 / Simple Mercator", GEOGCS["WGS 84",
30 *     DATUM["WGS_1984", SPHEROID["WGS_1984", 6378137.0, 298.257223563]],
31 *     PRIMEM["Greenwich", 0.0], UNIT["degree", 0.017453292519943295],
32 *     AXIS["Longitude", EAST], AXIS["Latitude", NORTH]],
33 *     PROJECTION["Mercator_1SP_Google"],
34 *     PARAMETER["latitude_of_origin", 0.0], PARAMETER["central_meridian", 0.0],
35 *     PARAMETER["scale_factor", 1.0], PARAMETER["false_easting", 0.0],
36 *     PARAMETER["false_northing", 0.0], UNIT["m", 1.0], AXIS["x", EAST],
37 *     AXIS["y", NORTH], AUTHORITY["EPSG","900913"]]
38 */
39OpenLayers.Layer.SphericalMercator = {
40
41    /**
42     * Method: getExtent
43     * Get the map's extent.
44     *
45     * Returns:
46     * {<OpenLayers.Bounds>} The map extent.
47     */
48    getExtent: function() {
49        var extent = null;
50        if (this.sphericalMercator) {
51            extent = this.map.calculateBounds();
52        } else {
53            extent = OpenLayers.Layer.FixedZoomLevels.prototype.getExtent.apply(this);
54        }
55        return extent;
56    },
57
58    /**
59     * Method: getLonLatFromViewPortPx
60     * Get a map location from a pixel location
61     *
62     * Parameters:
63     * viewPortPx - {<OpenLayers.Pixel>}
64     *
65     * Returns:
66     *  {<OpenLayers.LonLat>} An OpenLayers.LonLat which is the passed-in view
67     *  port OpenLayers.Pixel, translated into lon/lat by map lib
68     *  If the map lib is not loaded or not centered, returns null
69     */
70    getLonLatFromViewPortPx: function (viewPortPx) {
71        return OpenLayers.Layer.prototype.getLonLatFromViewPortPx.apply(this, arguments);
72    },
73   
74    /**
75     * Method: getViewPortPxFromLonLat
76     * Get a pixel location from a map location
77     *
78     * Parameters:
79     * lonlat - {<OpenLayers.LonLat>}
80     *
81     * Returns:
82     * {<OpenLayers.Pixel>} An OpenLayers.Pixel which is the passed-in
83     * OpenLayers.LonLat, translated into view port pixels by map lib
84     * If map lib is not loaded or not centered, returns null
85     */
86    getViewPortPxFromLonLat: function (lonlat) {
87        return OpenLayers.Layer.prototype.getViewPortPxFromLonLat.apply(this, arguments);
88    },
89
90    /**
91     * Method: initMercatorParameters
92     * Set up the mercator parameters on the layer: resolutions,
93     *     projection, units.
94     */
95    initMercatorParameters: function() {
96        // set up properties for Mercator - assume EPSG:900913
97        this.RESOLUTIONS = [];
98        var maxResolution = 156543.0339;
99        for(var zoom=0; zoom<=this.MAX_ZOOM_LEVEL; ++zoom) {
100            this.RESOLUTIONS[zoom] = maxResolution / Math.pow(2, zoom);
101        }
102        this.units = "m";
103        this.projection = this.projection || "EPSG:900913";
104    },
105
106    /**
107     * APIMethod: forwardMercator
108     * Given a lon,lat in EPSG:4326, return a point in Spherical Mercator.
109     *
110     * Parameters:
111     * lon - {float}
112     * lat - {float}
113     *
114     * Returns:
115     * {<OpenLayers.LonLat>} The coordinates transformed to Mercator.
116     */
117    forwardMercator: function(lon, lat) {
118        var x = lon * 20037508.34 / 180;
119        var y = Math.log(Math.tan((90 + lat) * Math.PI / 360)) / (Math.PI / 180);
120
121        y = y * 20037508.34 / 180;
122       
123        return new OpenLayers.LonLat(x, y);
124    },
125
126    /**
127     * APIMethod: inverseMercator
128     * Given a x,y in Spherical Mercator, return a point in EPSG:4326.
129     *
130     * Parameters:
131     * x - {float} A map x in Spherical Mercator.
132     * y - {float} A map y in Spherical Mercator.
133     *
134     * Returns:
135     * {<OpenLayers.LonLat>} The coordinates transformed to EPSG:4326.
136     */
137    inverseMercator: function(x, y) {
138
139        var lon = (x / 20037508.34) * 180;
140        var lat = (y / 20037508.34) * 180;
141
142        lat = 180/Math.PI * (2 * Math.atan(Math.exp(lat * Math.PI / 180)) - Math.PI / 2);
143       
144        return new OpenLayers.LonLat(lon, lat);
145    },
146
147    /**
148     * Method: projectForward
149     * Given an object with x and y properties in EPSG:4326, modify the x,y
150     * properties on the object to be the Spherical Mercator projected
151     * coordinates.
152     *
153     * Parameters:
154     * point - {Object} An object with x and y properties.
155     *
156     * Returns:
157     * {Object} The point, with the x and y properties transformed to spherical
158     * mercator.
159     */
160    projectForward: function(point) {
161        var lonlat = OpenLayers.Layer.SphericalMercator.forwardMercator(point.x, point.y);
162        point.x = lonlat.lon;
163        point.y = lonlat.lat;
164        return point;
165    },
166   
167    /**
168     * Method: projectInverse
169     * Given an object with x and y properties in Spherical Mercator, modify
170     * the x,y properties on the object to be the unprojected coordinates.
171     *
172     * Parameters:
173     * point - {Object} An object with x and y properties.
174     *
175     * Returns:
176     * {Object} The point, with the x and y properties transformed from
177     * spherical mercator to unprojected coordinates..
178     */
179    projectInverse: function(point) {
180        var lonlat = OpenLayers.Layer.SphericalMercator.inverseMercator(point.x, point.y);
181        point.x = lonlat.lon;
182        point.y = lonlat.lat;
183        return point;
184    }
185
186};
187
188/**
189 * Note: Two transforms declared
190 * Transforms from EPSG:4326 to EPSG:900913 and from EPSG:900913 to EPSG:4326
191 *     are set by this class.
192 */
193OpenLayers.Projection.addTransform("EPSG:4326", "EPSG:900913",
194    OpenLayers.Layer.SphericalMercator.projectForward);
195OpenLayers.Projection.addTransform("EPSG:900913", "EPSG:4326",
196    OpenLayers.Layer.SphericalMercator.projectInverse);
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