[OpenLayers-Users] Vertical lines on WMS layer?

Wed May 23 16:55:39 EDT 2007

On Wed, May 23, 2007 at 04:19:37PM -0400, 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?

I doubt it's an OpenLayers defect. I expect that your WMS server is not
coping so well. A way to test this would be to right click on an image,
copy the URL, and put it in an HTML page with a red background. If you
can see a white pixel along the edge of the tile, you're dealing with a
problem on your WMS server. 

I just tried this with an empty HTML file:

<body bgcolor="red"><img
src="http://demo.ionicenterprise.com/ionicweb/map/NATURALEARTH?LAYERS=NATURALEARTH&SERVICE=WMS&VERSION=1.1.1&REQUEST=GetMap&STYLES=&EXCEPTIONS=application%2Fvnd.ogc.se_inimage&FORMAT=image%2Fjpeg&SRS=EPSG%3A4326&BBOX=0%2C39.375%2C5.625%2C45&WIDTH=256&HEIGHT=256"
/></body>

And I see a white line.

So, go back to your WMS server, and get them to fix it :)

Alternatively, use TileCache with metatiles. The buffer will hide this
defect from you. 

Regards,
-- 
Christopher Schmidt
MetaCarta