Feature request #11569

Use ogr2ogr to Dissolve polygons

Added by Filipe Dias over 2 years ago. Updated almost 2 years ago.

Status:Closed Start Date:11/05/2014
Priority:Normal Due date:
Assigned to:Giovanni Manghi % Done:

0%

Category:Processing/GDAL
Target version:Future Release - Nice to have
Platform: Resolution:fixed/implemented
Platform version: Pull Request or Patch supplied:No
Status info: Tag:

Description

Apparently it is possible use ogr2ogr to dissolve polygons using GDAL compiled with SpatiaLite support. Example:

ogr2ogr output.shp input.shp -dialect sqlite -sql "SELECT ST_Union(geometry), dissolve_field FROM input GROUP BY dissolve_field"

For more details see: http://gis.stackexchange.com/questions/85028/dissolve-aggregate-polygons-with-ogr2ogr-or-gpc)

This would be a nice addition to Processing, since QGIS native Dissolve is rather slow. It would also be useful to be able to summarize the contents of the Dissolved features (i.e. sum, subtract, multiply etc).

See: http://gis.stackexchange.com/questions/65744/what-dissolve-tool-in-qgis-allows-me-to-summarize-statistics-for-multiple-attrib

History

Updated by Giovanni Manghi over 2 years ago

  • Status changed from Open to Feedback

how this alternative compare, in term of speed, to the native qgis tool, to the grass dissolve (in Processing) and the saga one (in Processing)?

Updated by Giovanni Manghi over 2 years ago

  • Assigned to changed from Victor Olaya to Giovanni Manghi

Updated by Giovanni Manghi over 2 years ago

  • Status changed from Feedback to Open

I answer myself, is very fast. As fast as SAGA. GRASS is "slow" because of the in/out overhead, while qgis native tool is dead slow.

Updated by Filipe Dias over 2 years ago

According to my tests, significantly faster than QGIS native tool. And it has the advantage of not relying on external software.

Updated by Giovanni Manghi almost 2 years ago

  • Status changed from Open to Closed
  • Resolution set to fixed/implemented

already implemented.

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