Hello, I am a newbie to OpenLayers and I have been for over a week having difficulty getting my mapserver wms overlay to display over a Bing hybrid base layer. I know that commercial map providers like to use spherical mercator srs code epsg:900913, while my wms layer is in epsg:4326 (WGS 84 datum). I also am aware that my mapserver (server is localhost) serves the wms layer as PNG image tiles, and that OpenLayers cannot reproject these client-side. I have been following this documentation: http://docs.openlayers.org/library/spherical_mercator.html, editing my ms4w PROJ/epsg and mapfiles so that they recognize the 900913 srs. I have checked the mapfile with getcapabilities and it is aware of that projection. I have read other users cases as well but those are about wms layers being stretched, slightly misaligned, or with missing tiles. Mine is not displaying at all, but upon right-clicking the map with the overlay turned on in the layer switcher, I can view the blank 256x256 image and get that tile's request URL. I have found that if I paste this in a browser address bar and change the SRS parameter back to its native 4326 and substitute the BBOX with the extents found in my mapfile, I can get the wms data to appear (the entire set of parcels are squeezed into a 256x256 tile). It doesn't seem to like the SRS and BBOX values after they have been converted into 900913 coordinates.
Here is my mapserver request URL from one tile: http://localhost/cgi-bin/mapserv.exe?MAP=C%3A%2Fms4w%2Fapps%2FLB_MAPFILES%2FPARCELS_MAPFILE.map&LAYERS=PARCELS_URL_pol&TRANSPARENT=true&DISPLAYPROJECTION=EPSG%3A4326&ISBASELAYER=false&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&FORMAT=image%2Fpng&SRS=EPSG%3A900913&BBOX=-13719529.331192,6352222.7966734,-13718306.33874,6353445.7891258&WIDTH=256&HEIGHT=256 Here is my relevant code: function init () { //Configure map var options = { projection: new OpenLayers.Projection("EPSG:900913"), units: "m", maxResolution: 156543.0339 maxExtent: new OpenLayers.Bounds(-20037508.34, -20037508.34, 20037508.34, 20037508.34)}; //Create new map object var map = new OpenLayers.Map('map',options); //Add a layerswitcher map.addControl(new OpenLayers.Control.LayerSwitcher()); //Add the Bing map base layer var vemap = new OpenLayers.Layer.VirtualEarth("Virtual Earth", { type: VEMapStyle.Hybrid, sphericalMercator: true, numZoomLevels: 21, maxExtent: new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34) }); //Add the WMS parcels overlay layer var parcels_wms = new OpenLayers.Layer.WMS( "Lions Bay Parcels", "http://localhost/cgi-bin/mapserv.exe?";, { map: 'C:/ms4w/apps/LB_MAPFILES/PARCELS_MAPFILE.map', layers: 'PARCELS_URL_pol', transparent: 'true', displayProjection: new OpenLayers.Projection("EPSG:4326"), isBaseLayer: false, maxExtent: new OpenLayers.Bounds(-20037508.34,-20037508.34,20037508.34,20037508.34)}, { visibility:false } ); //Add the layers to the map object map.addLayers([vemap,parcels_wms]); //Center the map over the study area map.setCenter(new OpenLayers.LonLat(-13718569,6353226), 14); ...the rest of the code is other map controls, layer opacity adjuster, and single-click mouse event handler containing a getfeatureinfo request. This code seems to be fine, but am I doing something wrong with setting max extent or max resolution? The Bing map itself centers and zooms the way I want, but the WMS data is failing to align with it. Perhaps it could be displayed outside of the extents and therefore not rendered at all? Or is this a mapserver problem where my server is not requesting tiles in epsg:900913 to align with Bing tiles? In another web template where I have not implemented the links to Bing maps, my wms layer displays fine since the map projection is 4326 and not 900913. That template has a line of code map.zoomToMaxExtent(); that, when commented out, makes the working overlay disappear completely. Don't know if that is a helpful clue. I have tried starting from a basic html template to add code line by line to isolate the problem. It works fine until I add the Bing layer which just wipes out the previously displayed WMS parcel layer to just display the Bing hybrid with the overlay present, but rendered completely as blank 256x256 tiles. Thank you for any advice, for I am out of leads! Regards, Chris Lam P.S. If this is a duplicate posting, you have my sincere apologies for the lapse in etiquette. At the time of this message, I was not subscribed to the mailing list and I think you have to be for messages to be accepted. Also I did not see my message in the users archive or on the Nabble forum where I found this list. Thank you for your understanding. -- View this message in context: http://osgeo-org.1803224.n2.nabble.com/Blank-WMS-tiles-displaying-over-Bing-hybrid-layer-tp5172086p5172086.html Sent from the OpenLayers Users mailing list archive at Nabble.com. _______________________________________________ Users mailing list Users@openlayers.org http://openlayers.org/mailman/listinfo/users
