[OpenLayers-Dev] WMS request mod

Dominik Mikiewicz dominikmikiewicz at o2.pl
Fri May 20 02:54:18 EDT 2011

This should work just fine. There won't be a serious performance hit either as you only recalculate bbox and change srs on the clientside. I do it quite often and even extended a wms layer class so I can quickly set up my 4326 layers to work with spherical Mercator.
However you may experience some issues with tile caching as sometimes the precision may vary from browser to browser. Another thing is the getFeatureInfo request - make sure you send correct cords if you are going to use it.

-----Original Message-----
From: openlayers-dev-bounces at lists.osgeo.org [mailto:openlayers-dev-bounces at lists.osgeo.org] On Behalf Of Ray Di Ciaccio
Sent: Thursday, May 19, 2011 6:00 PM
To: openlayers-dev at lists.osgeo.org
Subject: [OpenLayers-Dev] WMS request mod

Sorry for the previous messed up message. Let me try this again:

Hi all,

I'm in what I'm guessing is a fairly common situation -- I'm using 
Google Maps as my baselayer (so map is in EPSG:9009l3 projection) and 
I'm trying to load an overlay from a WMS which I have no control over. 
It only offers data in EPSG:4326. The WMS request generated by 
OpenLayers will be for CRS=EPSG:900913 and the BBOX values will be in 
EPSG:900913. This obviously won't work if the WMS only offers EPSG:4326. 
My solution to this problem was to override 
OpenLayers.Layer.WMS.getFullRequestString() so that it uses the 
projection that I set for that particular layer -- it changes the 
CRS/SRS param to whatever the layer projection is, and it transforms the 
BBOX values from the map projection to the layer's projection. This way 
I get a valid request for the WMS and it's loaded in the correct 
location on the basemap. My question is whether this is the right 
approach to this situation and whether there may be unforeseen 
repercussions to these changes I made.

- Ray

Ray Di Ciaccio
MIT LL, Group 42
ray.diciaccio at ll.mit.edu

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