[Chameleon] Can Chameleon do Cascading WMS?

Paul Spencer pagameba at magma.ca
Mon Oct 4 08:31:49 EDT 2004


these questions are more appropriate on the mapserver-users mailing list.

Re WMS and projections, mapserver will try to request a layer from a 
remote wms in the same projection that it is using for output.  If that 
projection is not available, mapserver will request the layer in the 
first projection it finds that it understands, and then reproject the 
raster locally ... this is non-optimal both in performance and 
appearance, but it does open up a much greater range of WMSs to you.

There is no default projection that all WMSs support

Cascading WMS refers to a a WMS Server that advertises a layer in its 
capabilities that is actually hosted on a different WMS Server.  In this 
case, the layer from the different WMS Server is 'cascaded' through the 
first WMS server.  This has nothing to do with projections and automatic 



Ken Sanderson wrote:
> I have been doing some reading on projections with WMS layers, given I
> am having problems with using a custom projection with my client. As I
> understand it, my client can only access WMS layers that have defined my
> projection in their <SRS> list, so many WMS layers may not be available
> to you depending on the projection of your client. Is this a correct
> understanding? Is there any default projection that all WMS layers can
> be accessed by?
> At any rate I was reading and found a term called cascading WMS, in
> which you accepted the WMS layer in any projection you are able to
> handle, ie in your EPSG, and then reproject it locally to your client
> projection. Are there any widgets for doing this in chameleon?
> Thanks,
> Ken
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|Paul Spencer                           pspencer at dmsolutions.ca   |
|Applications & Software Development                              |
|DM Solutions Group Inc                 http://www.dmsolutions.ca/|

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