[Qgis-user] labels: avoid duplicated labels

[Duarte Carreira]

Goyo, while I enjoy working with postgis a lot, the reality is I cannot expect "my" users to hack a sql view each time they need to label a map. It is not feasible to anticipate all situations and just create new items in my database to handle each one. It's difficult enough to manage the data as it is.

I will just get a call or email asking how can the multiple labels be avoided, and there is no easy answer for that. The answer I've come up with is to select the features I want to label, and create a new layer in qgis with the corresponding query, remove the symbol and label it - much like the old label type layers in MapServer.

Thanks,
Duarte

-----Mensagem original-----
De: Goyo [mailto:goyodiaz at gmail.com] 
Enviada: quinta-feira, 3 de Outubro de 2013 20:19
Para: Duarte Carreira
Cc: Qgis (qgis-user at lists.osgeo.org)
Assunto: Re: [Qgis-user] labels: avoid duplicated labels

2013/10/3 Duarte Carreira <DCarreira at edia.pt>:
> Thanks for your suggestion.
>
> But this is not feasible. I cannot keep creating new spatial tables for cartographic purposes, I just can't pay the maintenance cost of that (updating).

I was thinking of shapefiles and the like. With a spatial dabase it should be even easier. You can have a second geometry field and mantain it using a trigger or a script running in the background or at night or use a spatial view or just use multipolygons instead of (not in addition to) single polygons. The best solution depends on your typical workflow, the size of your data, etc.

It also depends on which database engine you use. I have done this kind of things with spatialite and I think they can be done with postgis in a similar way. In particular I've found spatial views are a very powerful tool for cartography. I often want to show multipoint features as polygons (buffer(convexhull(geom), n)) or single points (centroid(buffer(convexhull(geom), n))) and I can do it even on the fly using the DB manager or the fast SQL layer plugin.

Goyo

> It is awkward to me missing this option...
>
> Duarte
>
>
>
> -----Mensagem original-----
> De: Goyo [mailto:goyodiaz at gmail.com]
> Enviada: quinta-feira, 3 de Outubro de 2013 16:57
> Para: Duarte Carreira
> Cc: Qgis (qgis-user at lists.osgeo.org)
> Assunto: Re: [Qgis-user] labels: avoid duplicated labels
>
> 2013/10/3 Duarte Carreira <DCarreira at edia.pt>
>>
>> Hi there.
>>
>>
>>
>> Is there any option to avoid duplication of labels when several polygons have the same label?
>
> Convert your polygons to multipoligons, grouping by the field shown in the label.
>
> Goyo
>