[OpenLayers-Users] wrapDateLine with WMS, map covered by opaque film

[Sige]

For those who have similar problem, there is actually a work around 
http://n2.nabble.com/Tiles-outside-maxExtent-being-loaded-td1829360.html#a1829361 
posted earlier on this forum , which overcomes the request for tiles outside
the maxExtent by creating a subclass of OpenLayers.Layer.WMS and overriding
the getURL() method. The new method checks the latitude bounds, setting the
URL to that of a fixed blank image if out of bounds.  Thank you Jon!



Sige wrote:
> 
> I found that wrapDateLine tries to request 
> http://maps.geonet.org.nz/tilecache/tilecache.py?LAYERS=nasagm&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&FORMAT=image%2Fjpeg&SRS=EPSG%3A4326&BBOX=-90,-270,0,-180&WIDTH=256&HEIGHT=256
> map tiles outside the map extent , such as:
> [-90.0, -270.0, 0.0, -180.0], which our tilecache server is unable to
> retrieve and responds with an error message:
> 
> An error occurred: couldn't calculate tile index for layer nasagm from
> ([0.0, -270.0, 90.0, -180.0])
>   File "/usr/local/tilecache/TileCache/Service.py", line 421, in
> modPythonHandler
>     host )
> 
> While the WMS server of metacarta is able to handle such 
> http://labs.metacarta.com/wms/vmap0?LAYERS=basic&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&FORMAT=image%2Fjpeg&SRS=EPSG%3A4326&BBOX=-90,-270,0,-180&WIDTH=256&HEIGHT=256
> request , and responds with an empty blue tile, I guess this might be the
> reason for the problem mentioned in my previous post. What should I do on
> the tilecache server side to handle request outside the map extent?
> 
> Sige
> 
> 
> 
> 
> Sige wrote:
>> 
>> Hi List,
>> 
>> I am trying to make my wms (tilecached) map wrapped across the date line,
>> like:
>> 
>>  var  map = new OpenLayers.Map( $('map'),
>>                             {
>>                          maxResolution: 0.3515625,
>>                          projection: 'EPSG:4326'
>>                             }
>>              );      
>>            var wms = new OpenLayers.Layer.WMS(
>>                   "WMS/Tilecache",
>>                    "http://maps.geonet.org.nz/tilecache/tilecache.py?",
>>                       {
>>                                         format: 'image/png',
>>                                         projection: 'EPSG:4326',
>>                                         units: 'degrees',      
>>                                         maxResolution: 0.3515625,
>>                                         layers: 'nasagm',
>>                                         isBaseLayer: true,
>>                                         reproject: false,        
>>                                         buffer: 1
>>                                        },
>>                    {wrapDateLine: true, reproject: false}  
>>                    );
>>                   map.addLayer(wms);           
>>             map.addControl(new OpenLayers.Control.MousePosition());
>>             map.zoomToMaxExtent();
>> 
>> The map wrapped well, however, when I pan and zoom the map around, part
>> of the map or the whole map becomes opaque (like covered by a white
>> film). I am not sure if this is caused by my wms (tilecache) or
>> wrapDateLine. The WMS map works fine without wrapDateLine.  
>> 
>> I have also tried the WMS from metacarta.com (mapServer) which works
>> fine:
>>        var wms1 = new OpenLayers.Layer.WMS( "OpenLayers
>> Basic",//MapServer
>>                         "http://labs.metacarta.com/wms/vmap0",
>>                         {layers: 'basic'},
>>                         {wrapDateLine: true} );
>>                       map.addLayers([ wms1]); 
>> 
>> Thanks,
>> 
>> Sige 
>> 
> 
> 

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