[OpenLayers-Users] Optimization of raster WMS layers

[jdmorgan]

Hi Steve,

Thanks so much for you replies. I would like to try to set the 
visibility scale threshold.  Any advice how to do this would be great.  
Below is my init function where I do set the maxExtent. But I am 
guessing that by visibility scale threshold you mean setting predefined 
scaled.  I am not really show how best to determine the predefined 
scales. My map is in EPSG 4326.

/function init() {

     //Data stored as left, bottom, right, top floats.
     bounds = new OpenLayers.Bounds();
     bounds.extend(new OpenLayers.LonLat(-131.30859375,23.745610382199022));
     bounds.extend(new OpenLayers.LonLat(-58.18359375,48.50874245880332));
     bounds.toBBOX();

     map = new OpenLayers.Map('map', {
         controls: [
             new OpenLayers.Control.Navigation(),
             new OpenLayers.Control.Permalink(),
             new OpenLayers.Control.ScaleLine(),
             new OpenLayers.Control.Permalink('permalink'),
             new OpenLayers.Control.PanPanel(),
             new OpenLayers.Control.MousePosition(),
             new OpenLayers.Control.OverviewMap(),
             new OpenLayers.Control.KeyboardDefaults()
         ],
         numZoomLevels: 16,
         maxExtent: bounds
     });

      map.addControl( new OpenLayers.Control.PanZoomBar(), new 
OpenLayers.Pixel(800,0));

     var streetMap = new OpenLayers.Layer.ArcGIS93Rest(
         'ESRI Streets',
'http://server.arcgisonline.com/ArcGIS/rest/services/World_Street_Map/MapServer/export?f=image', 

         {layers: 'show:0'},
         {
             buffer: 2
         }
     );

     var stateMap = new OpenLayers.Layer.WMS(
         'States',
         'http://linuxserver/html/vlayers',
         {layers: 'states', transparent: true},
         {
             isBaseLayer: false,
             transitionEffect: 'resize',
             buffer: 2
         }
     );

     var //rasterlayer//= new OpenLayers.Layer.WMS(
         'rasterlayer',
         'http://linuxserver/html/ews',
         {layers: 'layerofinterest', transparent: true},
         {
             isBaseLayer: false,
             transitionEffect: 'resize',
             buffer: 0
         }
     );

     map.addLayers([streetMap, stateMap, fcavLayer]);
     map.setCenter(new OpenLayers.LonLat(-98.0859375, 
39.095962936305476), 5);

     info = new OpenLayers.Control.WMSGetFeatureInfo({
             url: 'http://rain.nemac.org/~derek/fswms/html/vlayers',
             title: 'Identify features by clicking',
             queryVisible: true,
             eventListeners: {
                 getfeatureinfo: function(event) {
                     map.addPopup(new OpenLayers.Popup.FramedCloud(
                                   "Feature Info:",
map.getLonLatFromPixel(event.xy),
                                   null,
                                   event.text,
                                   null,
                                   true
                                   ));
                 }
             }
         });
     info.infoFormat = 'application/vnd.ogc.gml';
     map.addControl(info);
     info.activate();
}//END OPENLAYERS 
INIT--------------------------------------------------------------
/
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