[MAPSERVER-USERS] Hiding overviews

[Pål Kristensen]

Hi!

I'm trying to do the exact same thing, but havn't found any solutions
either. I ended up by putting all the "zoom levels" in separate layers, and
group all these layers in one named group layer.

There has been some discussions regarding this issue in an older dev thread:
http://www.nabble.com/Excluding-certain-layer-types-from-WMS...-to14786841.html#a14813767

Regards,
Pål Kristensen



Eichner, Andreas - SID-NLK wrote:
> 
> 
> Hmm, seems my description wasn't clear enough, so I'll try to precise...
> 
> For a layer with raster data I created external overviews. To make use
> of them I copied the LAYER portion of the map file, changed the
> TILEINDEX statement to point to the index of the appropriate overview,
> set MINSCALE/MAXSCALE to form a continues range and added a GROUP
> statement to all of them to form a single layer again as it was before
> without the overviews added. Now I can take a WMS client, enable or
> disable the layer group which collects the detail layer and all of it's
> overviews which kick in if you increase the scale.
> 
> So instead of having a single layer consisting of huge tiled which have
> all to be touched and scaled down for a request at large scales I now
> have a group consisting of several layers where only one is active at
> each scale. Doing so was a suggestion from the raster data (optimizing)
> howto and they called this solution "external overviews".
> 
> So if I have a layer "raster" (scale 10...5000000) I want to split it
> into "detail" (scale 10...1000) and "overview" (scale 1000...5000000)
> and put both in a _group_ "raster" for example. Now you can go and
> request the layer "raster" as before and what you get depends on the
> chosen scale and is either "detail" below 1000 or "overview" above 1000.
> 
> The problem is that you can explicitly request the layer "detail", but
> if you are above 1000 you will see... Absolutely nothing. Same with the
> "overview" layer below 1000. This is because those layers have a name
> which enables them to be requested in a WMS "GetMap" request. If they
> wouldn't you could only request the named group layer "raster". So I
> thought it could be done by ommitting the "wms_name" part of the
> METADATA but if you do and issue a "GetCapabilities" request you will
> see that MapServer outputs a warning about the missing mandatory name
> attribute and inserts the layer name from the NAME attribute of the map
> file.
> 
> We have a WMS client which displays nested named layers as folders. The
> result isn't user friendly... So I wondered if there's a way to hide
> those external overviews from the user since the only thing he can
> decide is either to display the hole group (which ever layer may be
> affected) or none of those layers at all.
> 
> Hope I could make the situation a little bit clearer. I believe it's
> only a little thing I miss but there are too much trees in the wood... 
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> 
> 

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