Porjection and WMS

[Frank Warmerdam]

Daniel Goetz wrote:
...
> What stands the PORJECTION-object in the MAP-object for (not in case of
> WMS)? In my understanding it defines the projetion of the output image that
> mapserver generates. Is this true? 

Yes

 > And if so can I choose every procetion
> in the PROJECTION-object of the MAP-object regardless of the projection of
> the single layers?

Yes

> What stands the PROJECTION-object in the LAYER-object for (not in the case
> of a WMS)? In my understanding this should be the projection in which the
> input data are recorded. Is this true? 

Yes

 > So for each LAYER there is
> definitively only one type of projection possible in fact the one in which
> the original input data are recorded.

Yes

Pretty easy so far!

> And now the case of a WMS-Server:
> 
> What stands the PROJECTION-object in the MAP-object of a WMS-service for in
> contrast to the WMS_SRS parameter of the METADATA in the MAP-object? Is
> this the same as in "normal" mapserver applications and the
> PROJECTION-object gives the projection mapserver shall project its
> output-images? What is the difference between PROJECTION-object and WMS_SRS
> parameters in the MAP-object?

I suspect the projection on the map object in a WMS situation is what would
be used if no SRS is selected in the WMS request.  I believe the wms_srs
metadata is used in building the list of supported projections in the
capabilities document and may be used to validated selected SRS values.

> And what about the PROCETION-object and the WMS_SRS-metadata in the
> LAYER-objects? should this be the declaration of the "real" PROCETION/SRS
> the input-data are in? And what is the difference between PROJECTION and
> WMS_SRS in this case?

The PROJECTION block definately still needs to be the real projection of
the underlying data.  I believe normally the wms_srs metadata would be the
list of supported projections the layer can be returned in.  I'm not
sure why you would use a different list for the wms_srs values for layers
and the map as a whole.

I'm sorry my answers with regard to wms_srs are a bit vaguer than my
earlier answers.

Best regards,
-- 
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I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
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