Map.addBaseLayers = function () {
    this.defaultCentre = [4, 48.8, 5]; // centre of W Europe
    this.m_mousePrefix = "Mercator ";
    this.map.projection = "EPSG:900913";
    this.map.numZoomLevels = 18;
    this.map.maxExtent = new OpenLayers.Bounds(-20037508.3427892, -20037508.3427892, 20037508.3427892, 20037508.3427892);
    var google = new OpenLayers.Layer.Google("Google Streets", { sphericalMercator: true } );
    var ghyb = new OpenLayers.Layer.Google("Google Hybrid", { type: G_HYBRID_MAP,  sphericalMercator: true } );
    var gphys = new OpenLayers.Layer.Google("Google Terrain", { type: G_PHYSICAL_MAP,  sphericalMercator: true } );
    this.map.addLayers([google, ghyb, gphys]);
    this.switcher = true;
    var pos = new GControlPosition(G_ANCHOR_TOP_LEFT, new GSize(210,0));
    google.mapObject.addControl(new GScaleControl(), pos);
    ghyb.mapObject.addControl(new GScaleControl(), pos);
    gphys.mapObject.addControl(new GScaleControl(), pos);
}