[OpenLayers-Users] WMS overlay not shown at zoom level 0 when singleTile: true

Wed Feb 3 13:49:08 EST 2010

On Wed, Feb 03, 2010 at 10:41:51AM -0800, Tom B wrote:
> 
> Hi all,
> 
> In the attached code, the WMS overlay is shown fine at zoom level 1, but at
> zoom level 0, it disappears.  If I either remove the "singleTile: true"
> option, or use a MetaCarta base layer instead of the Google one, then the
> overlay shows up fine at zoom level 0.

The problem is usually that Google wraps the world, so when we ask for corners,
the bbox ends up being invalid.

-- Chris

> I took a look at the WMS request at map.layers[1].grid[0][0].url at zoom
> level 0, and GeoServer renders that URL fine, so it looks like this issue is
> related to OpenLayers.
> 
> Any ideas of what might be going wrong here?
> 
> Best,
> Tom
> 
> <html xmlns="http://www.w3.org/1999/xhtml">
>   <head>
> 	<script type="text/javascript"
> src="http://maps.google.com/maps?file=api&amp;v=2&amp;sensor=false
> 	
> &amp;key=ABQIAAAAmlH3GDvD6dTOdZjfrfvLFxTkTKGJ2QQt6wuPk9SnktO8U_sCzxTyz_WwKoSJx63MPLV9q8gn8KCNtg">
> 	</script>
>     <script src="http://www.openlayers.org/api/OpenLayers.js"></script>
>     <script type="text/javascript">
>         var lon = 5;
>         var lat = 40;
>         var zoom = 1;
>         var map, layer;
> 
>         function init(){
>         
>         	var mapOptions = {
> 				controls: [],
> 				projection: new OpenLayers.Projection("EPSG:900913"),
> 				units: "m",
> 				maxResolution: 156543.0339,
> 				maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34,
> 20037508.34, 20037508.34),
> 				restrictedExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34,
> 20037508.34, 20037508.34),
> 				minZoomLevel: 2
> 			};
> 			
>             map = new OpenLayers.Map('map', mapOptions);
> 
> 			map.addControl(new OpenLayers.Control.PanZoomBar());
> 			
> 			if(true){
> 				var base_layer = new OpenLayers.Layer.Google(
> 					"Google Satellite",
> 					{
> 						type: G_SATELLITE_MAP,
> 						sphericalMercator: true,
> 						isBaseLayer: true
> 					}
> 				);
> 			}else{			
> 				var base_layer = new OpenLayers.Layer.WMS( "OpenLayers WMS",
> 					"http://labs.metacarta.com/wms/vmap0",
> 					{
> 						layers: 'basic',
> 						sphericalMercator: true,
> 						isBaseLayer: true
> 					}
> 				);
> 			}	
> 			map.addLayer(base_layer);
> 			map.setBaseLayer(base_layer);
> 			
> 
>             map.setCenter(new OpenLayers.LonLat(lon, lat), zoom);
>             map.addControl( new OpenLayers.Control.LayerSwitcher() );
>             
> 			var new_layer = new OpenLayers.Layer.WMS('asdf',
> "http://sds7.itc.virginia.edu:8080/thdl-geoserver/wms",
> 				{
> 					layers: 'thl:roman_popular_poly',
> 					transparent: true,
> 					sphericalMercator: true,
> 					projection: new OpenLayers.Projection("EPSG:900913"),
> 					units: "m",
> 					CQL_FILTER: "fid=1"
> 				},
> 				{
> 					singleTile: true
> 				}
> 			);
> 			map.addLayer(new_layer);
> 				
>             
>         }
>     </script>
>   </head>
>   <body onload="init()">
>   
>     <div id="map" class="smallmap"></div>
>     
>   </body>
> </html>
> -- 
> View this message in context: http://n2.nabble.com/WMS-overlay-not-shown-at-zoom-level-0-when-singleTile-true-tp4508945p4508945.html
> Sent from the OpenLayers Users mailing list archive at Nabble.com.
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-- 
Christopher Schmidt
MetaCarta