title: Open Layers 3: loading a GEBCO WMS layer
body: <p>I'm trying to rewrite a small outreach application made in OL2 which uses a base layer to show the ocean topography provided by the GEBCO WMS service.</p>
  
  <p>When I do:</p>
  
  <pre><code>var gebco = new ol.layer.Image({
       source: new ol.source.TileWMS( ({
       url: 'http://www.gebco.net/data_and_products/gebco_web_services/web_map_service/mapserv?',
       params: {'LAYERS': 'GEBCO_LATEST', 'VERSION':'1.1.1','FORMAT': 'image/png'}  }) ),
                  serverType: 'mapserver'
                 });
  </code></pre>
  
  <p>the layer is not added. I have looked through firebug to see
  the request and while it seems to be correct the answer is a white tile with the BBOX set by Ol3. If I request directly to the map server with the BBOX [-180,-90,180,90] (or any other geographical extent) the server returns correctly the image. Then if I try to force the LayerWMS with such geographical coordinates in params:{} (i.e ..,'BBOX':'-180,-90,180,90',... ) the layer still does not load.</p>
  
  <p>To show the layer I just do:</p>
  
  <pre><code> mapa = new ol.Map({
       target: 'map',
       renderer:'canvas',
       layers: [
              new ol.layer.Tile({ 
                 source: new ol.source.MapQuest({layer: 'sat'}),
                 visible: true
             })],
        view: new ol.View({
         center: ol.proj.transform([-10.0, 41.0],'EPSG:4326', 'EPSG:3857' ),
         zoom: 4
       })
    });
    mapa.addLayer(gebco);
  </code></pre>
  
  <p>I would appreciate any explanation to understand what is happening. In fact, the rest of WMS layers are added correctly, so I presume it could be related with such mapserver, but honestly I'm not very experimented with OL and map servers.</p>