[OpenLayers-Users] EPSG:4326 overlay EPSG:900913 as WMS

[Christopher Schmidt]

On Wed, May 13, 2009 at 05:29:26PM +0200, Dipl. Inf. Carsten Eider wrote:
> Hi Christopher,
> 
> thank you for your useful answers, but......
> 
> Christopher Schmidt schrieb:
> > On Wed, May 13, 2009 at 04:56:26PM +0200, Dipl. Inf. Carsten Eider wrote:
> >   
> >> Hi list,
> >>
> >> as far as i understood by reading lots of mailings within this list and
> >> spending time on walking through different openlayer pages
> >> there seems to be no solution for using a
> >> wms in epsg:4326 on top of a google EPSG:900913.
> >>     
> >
> > Correct. All raster layers in OpenLayers must be in the same projection.
> > Browsers can not reproject images. Therefore, if you wish to use a
> > raster layer, it must support the projection fo the base layer -- in the
> > case of google, that's spherical mercator.
> >   
> why can a wms-layer not transform its coordinates in epsg:900913 to
> epsg:4326 before doing its request for an image?
> okay i never tried it but i suposse this could result in some horrible
> images?

The images don't match. You get 'stretching'. 

900913 is not a special projection in any particular way. Ask the same
question about a polar projection -- one centered on Antarctica, for
example. North America is a 5 px smudge. Why can't OpenLayers take that
5 pixel smudge, and turn it into North America -- thedata isn't there.

> >   
> >> I tried lots of ways to tell my wms-layer to be requesting in EPSG:4326,
> >> but none worked.
> >> my problem ist, that the layers i want to use come from governmental
> >> servers not offering EPSG:900913
> >> but EPSG:4326 or EPSG:31647.
> >>     
> >
> > Then you can't use them on top of Google Maps without making yourself a
> > reprojecting service. You can use MapServer as a WMS server to 'cascade'
> > -- load and reproject, in this case -- from the remote server. This
> > would mean you would talk to your own MapServer, which would then talk
> > to the government provided WMS.
> >
> >   
> >> Can anyone comfirm this situation or show me a solution?
> >>     
> >
> > Yes, I can confirm that you are correct.
> >
> >   
> >> Are there any Reprojection-Services available?
> >>     
> >
> > MapServer can act as a reprojection service.
> >   
> damn i would prefer geoserver :-)

I know nothing about GeoServer.

Regards,
-- 
Christopher Schmidt
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