Question

I found a lot of examples how to add/remove Overlays to your Openlayers Map using the LayerSwitcher. My purpose is to provide a LayerSwitcher which allows only one map service provider (e.g. GoogleMaps and Openstreetmaps) at a time. Is this possible with the LayerSwitcher class?

I tried the following which shows the switch I want to have, but only the first layer can be visualized!

var osmLayer = new OpenLayers.Layer.OSM("Open Street Maps",
                                        ["http://a.tile.openstreetmap.org/${z}/${x}/${y}.png",
                                         "http://b.tile.openstreetmap.org/${z}/${x}/${y}.png",
                                         "http://c.tile.openstreetmap.org/${z}/${x}/${y}.png"
                                        ],
                                        {visibility: true, isBaseLayer: true});
var wmsLayer = new OpenLayers.Layer.WMS("OpenLayers WMS",
                                        "http://vmap0.tiles.osgeo.org/wms/vmap0",
                                        {layers: 'basic'},
                                        {visibility: true, isBaseLayer: true});

this.map = new OpenLayers.Map({
                         div: divname,
                         allOverlays: false,
                         theme: null,
                         controls: [
                            new OpenLayers.Control.LayerSwitcher(),
                         ]
});
this.map.addLayers([osmLayer, wmsLayer]);
this.map.setCenter(
    new OpenLayers.LonLat(8.56, 50).transform(
          new OpenLayers.Projection("EPSG:4326"), 
          this.map.getProjectionObject()
    ), 10
);

If I choose the second entry nothing is shown on the map and selecting the first one does show the OSM map again.

Thanks in advance!

Answer 1

I think the problem is that you are trying to use Metacartas WMS i EPSG:900913 projection(the one that OpenStreetMaps and Google uses)

Though it says in GetCapabilities that it should support 900913, it look like it doesn’t. If you try to use WMS layer alone(in EPSG4326) you’ll see that it works just fine.