[OpenLayers-Users] Users Digest, Vol 8, Issue 38

[Jeff Yutzler]

Tim,
This workaround works fine at large scale, but unfortunately it 
completely breaks down at small scale.  When I try it at 1:433k, 1:216k, 
or 1:108k, I get even thicker white lines.  Oh well.  I have Ionic's 
RedSpiderWeb team looking at it.
Thanks for trying.
-Jeff

users-request at openlayers.org wrote:

From: Tim Schaub <noreply at geocartic.com> Subject: Re: [OpenLayers-Users] 
Vertical lines on WMS layer? To: users at openlayers.org Message-ID: 
<4655F1FC.6000909 at geocartic.com> Content-Type: text/plain; 
charset=ISO-8859-1; format=flowed Jeff Yutzler wrote:

> > When I set the following WMS layer into OpenLayers:
> > 
> >    map.addLayer(new OpenLayers.Layer.WMS( "IONIC Natural Earth WMS", 
> > "http://demo.ionicenterprise.com/ionicweb/map/NATURALEARTH", {layers: 
> > 'NATURALEARTH'}));
> > 
> > I get behavior I have not seen anywhere else.  At most scales, the layer 
> > looks fine.  However, at 1:3M and 1:7M, white vertical lines appear at 
> > the tile boundaries.  I suppose this is a defect in OpenLayers, but I'm 
> > not really even sure how to describe it.  Any ideas?
>   

For tile renderers (WMS servers) that have unsavory edge effects, you 
can use the "gutter" option on a layer.  This requests a larger tile 
than is actually displayed in OpenLayers - hiding ugly tile edges if you 
can't control the tiling yourself (with TileCache).

This functionality was introduced during 2.4 development and will be 
included in the 2.4 release.  (See http://trac.openlayers.org/ticket/529 
for details.)

In your case, the following layer definition gets rid of the white tile 
edges:

   var iconic = new OpenLayers.Layer.WMS("IONIC Natural Earth WMS",
       "http://demo.ionicenterprise.com/ionicweb/map/NATURALEARTH",
       {layers: 'NATURALEARTH'},
       {gutter: 2});

   map.addLayer(iconic);

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