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List:       qgis-user
Subject:    Re: [Qgis-user] slow dissolve
From:       Filipe Dias <filipesdias () gmail ! com>
Date:       2014-11-28 11:16:26
Message-ID: CABr3zxV_OTGahVzoF2tS9Mh8H+NsUUQ7SD1YZWJq=kLF3xSw3Q () mail ! gmail ! com
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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.lange@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
>

[Attachment #5 (text/html)]

<div dir="ltr"><div><div>Hi<br><br></div>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).<br><br></div><div>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.<br></div><div><br></div>HTH<br></div><div class="gmail_extra"><br><div \
class="gmail_quote">On Fri, Nov 28, 2014 at 11:09 AM, Torsten Lange <span \
dir="ltr">&lt;<a href="mailto:torsten.lange@mail.de" \
target="_blank">torsten.lange@mail.de</a>&gt;</span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"><br>Hi,<br><br>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&#39;t take too long in our house until one of our ArcGIS licences is freed to \
solve the issue, but why it shouldn&#39;t work with QGIS?<br><br>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?<br><br>Appreciate your comments!<span class="HOEnZb"><font \
color="#888888"><br>Torsten \
</font></span><br>_______________________________________________<br> Qgis-user \
mailing list<br> <a href="mailto:Qgis-user@lists.osgeo.org">Qgis-user@lists.osgeo.org</a><br>
 <a href="http://lists.osgeo.org/mailman/listinfo/qgis-user" \
target="_blank">http://lists.osgeo.org/mailman/listinfo/qgis-user</a><br></blockquote></div><br></div>




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