[Qgis-user] slow dissolve

2014-11-28 Thread Torsten Lange
Hi,

Since I work with QGIS the dissolve function tends to be very slow for me. 
E.g., it takes ours to dissolve a layer of 15000 polygons. ArcGIS in contrast, 
does the job in a couple of minutes. Usually, it doesn't take too long in our 
house until one of our ArcGIS licences is freed to solve the issue, but why it 
shouldn't work with QGIS?

Thus the question: Is dissolve generally a bottle neck in QGIS or does it 
depend on the structure of the dataset? The polygones I deal with are never 
overlapping, but have either common borders or are seperated. At least, I could 
imagine this may be the reason why the algorithm is so slow?

Appreciate your comments!
Torsten
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Re: [Qgis-user] slow dissolve

2014-11-28 Thread Filipe Dias
Hi

The Dissolve tool is very very slow. But from the Processing toolbox you
can use the equivalent tool from SAGA GIS (Polygon dissolve) or v.dissolve
from GRASS GIS which are considerably faster (assuming you have installed
both these software packages).

A new native QGIS Dissolve tool is being prepared by one of the developers
and it should be available in a couple of weeks. But in the meantime the
two options I mentioned should do the job.

HTH

On Fri, Nov 28, 2014 at 11:09 AM, Torsten Lange torsten.la...@mail.de
wrote:


 Hi,

 Since I work with QGIS the dissolve function tends to be very slow for me.
 E.g., it takes ours to dissolve a layer of 15000 polygons. ArcGIS in
 contrast, does the job in a couple of minutes. Usually, it doesn't take too
 long in our house until one of our ArcGIS licences is freed to solve the
 issue, but why it shouldn't work with QGIS?

 Thus the question: Is dissolve generally a bottle neck in QGIS or does it
 depend on the structure of the dataset? The polygones I deal with are never
 overlapping, but have either common borders or are seperated. At least, I
 could imagine this may be the reason why the algorithm is so slow?

 Appreciate your comments!
 Torsten
 ___
 Qgis-user mailing list
 Qgis-user@lists.osgeo.org
 http://lists.osgeo.org/mailman/listinfo/qgis-user

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