[mapserver-users] OGC specs

[Rob Atkinson]

Very briefly (I'm afraid...)

WMS allows the map server to advertise what it is prepared to serve - so the map server could return either an error (encoded in XML by preference, but legally a BLANK image) if the "scaleHint" is exceeded.

So, you dont need to let a user override mapserver's defaults.

Even better, under WMS a layer can be a nested hierarchy, so you could have a series of layers that form a series - at a certain scale turn on "interstates" and at a larger scale turn it off and turn on "goattracks" - and call this a single layer transport

This would currently require a hand built Capabilities but would be entirely consistent with mapservers current capabilities, the WMS spec and the possible user requirements. 3 out of 3 aint bad - but really the mapserver datamodel being able to group layers by a single logical name would make this much easier to configure.

Cheers

Walt wrote:

> Has anybody looked at the OGC specs for "Web Map Server Interfaces Implementation"? <http://www.opengis.org/techno/specs/00-028.pdf>.  I'm trying to build an OGC compliant web map server and I'm running into this problem.  On pages 22-23 they specify CGI parameters one can pass to the map server to request a map.  One of these is the layers keyword, whose value is a list of layers that should be turned on.  So here's the problem: mapserver decides at which scale to turn a layer on (ie you don't want streets turned on when viewing a map of the whole US).  How can one achieve the functionality of letting a user override these scale defaults?  For example, what if a user wants to see the streets layer for the whole US?  THe streets layer gets passed as part of the layer CGI parameter, but then mapserver decides not to turn it on.  Has anyone dealt with this problem and if not, are there suggestions?  Perhaps another CGI paramter for "demanded layers"?
>
> Thanks,
> Walt
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