[Qgis-user] Qgis/qgis server different layer scales to speed up server

[Richard McDonnell]

Pietro

Hi, I have been tricking around with Zoom Level based Styling for 
OpenStreetMap (Just Ireland) on GeoServer. We utilise a PostGIS database 
back end to store the features, a SLD with different zoom levels is then 
used to display the features required at each level. If you want, I can 
send a sample in text format to you to look at if you would like?
A similar QGIS Style could be created to do the same thing, using rule 
based styling.
Other than that, I believe there is no way to do what you want other 
than the way you suggested yourself, with the different table for each 
zoom level.
I am open to correction on this, but some simplification of the 
geometry, happens anyway, for all geometry outside of the bounding box 
that is your canvas does it not?
Sorry I cant be of more help.
Regards,

Richard.


On 18/02/2016 13:05, Pietro Rossin wrote:
> Hello qgis users
> I hope this is the right place to ask for help in selecting the right
> strategy to spped up the data served by qgis-server/lizmap
>
> I have many polygonal features that can be seen at various zoom level
> I want to serve them as a webis with qgis-server and Lizmap
> Data are on a postgis server with all indexes set.
>
> I had some suggestion to simplify the geometry let's say with 3-4
> simplyfication level on the nodes of any polygon.
> So I made 3 geometry column (orig - simpl1, simpl2 ecc) all the same kind of
> the original one and each field with its index.
> In simpl1, 2 3 ecc I calculate a simplification with
> ST_SimplifyPreserveTopology(geometry , float) with increasing tolerance
> based on original geometry.
>
> Now I will like to use these geometry columns to load simpler features at
> low zoom and richer ones at higher zoom level.
>
> Is it possible to tell qgis to load a particular geometry column based on
> the zoom level?
> This thing should be also available in qgis-server and then in lizmap..
>
> One solution I found was to make different view/query to load layers with
> the desired geometry column and use visibility based on scale to show/hide
> different layers..
>
> Any other way?
>
> Is it preferable to create views in Postgis or to query data by qgis db
> manager?
>
> Thanks for your help
> Pietro
>
>
>
>
> --
> View this message in context: http://osgeo-org.1560.x6.nabble.com/Qgis-qgis-server-different-layer-scales-to-speed-up-server-tp5251409.html
> Sent from the Quantum GIS - User mailing list archive at Nabble.com.
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-- 
*_Richard McDonnell_*
*GIS Specialist PgD GIS AssocSCSI*
*OPW FRM Data Management*
*52 Stephens Green, Dublin 2.*
TEL: 01 6476543

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