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... _______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
