Hi, I have just solved the clipping by using v.overlay which gave reasonable processing time. My experience is that qgis:clip and qgis:difference is quite slow when it comes to clipping lines by polygon. Best regards, Jonas
2014-10-16 11:29 GMT+02:00 Filipe Dias <[email protected]>: > Yes, convert format is based on ogr2ogr but I dont think it can be > modified to do "clip". Why don't you try running ogr2ogr from the command > line? > > You need to navigate to the directory where both your shapefiles are > stored and run the code just like in the blog post. I tried on Linux but it > should be the same on Windows (command line on Windows is "command prompt"). > > ogr2ogr -clipsrc clipping_polygon.shp output.shp input.shp > > Hope it helps > > PS: It would be nice to add a "clip" algorithm based on ogr2og with -clipsrc > since it seems to be much faster > > On Thu, Oct 16, 2014 at 1:16 AM, Jonas Sjögren <[email protected]> > wrote: > >> Hi again, >> unfortunately the processing is quite slow again with the difference >> algorithm, about 2,5 hours. With a script running with 60 iterations the >> total processing time will be about a week. No other processes are running >> except for internet. The script sequence is >> processing.runalg( 'qgis:difference', InputRoadNetwork, ClippingPolygon, >> OutputRoadNetwork ) >> I have tried the 'gdalogr:ogr2ogr' clipping algorithm expressed in >> http://darrencope.com/2011/03/31/clipping-large-shapefiles-using-ogr/ >> and http://www.gdal.org/ogr2ogr.html >> which I believe corresponds to the algorithm GDAL/OGR [32 geoalgorithms] >> => [OGR] Conversion => Convert format in the Processing Toolbox. Still I >> do not know how to get the code right in 'Creation Options'. It should be >> something like >> [-clipsrc ClippingPolygon.shp]. Anyone who has an idea? >> >> Best regards, >> Jonas >> >> >> 2014-10-14 20:36 GMT+02:00 Jonas Sjögren <[email protected]>: >> >>> Hi, >>> to check that my data was ok I tried a clip tool in ArcMap where the >>> same calcuation took exactly 10 seconds. After some modifications in my >>> script and using the 'qgis:difference' algorithm, processing time was >>> reduced to about 5 minutes, quite acceptable. Thank you for helping me sort >>> this out. >>> /Jonas >>> >>> 2014-10-14 7:47 GMT+02:00 Bernhard Ströbl <[email protected]>: >>> >>>> Hm, >>>> >>>> goes pretty fast here, both with PostGIS and shp layers (some 5 lines, >>>> 1 polygon, both layers in the same CRS as the project, shp on local drive) >>>> QGIS 2.4 64 bit on Win7 >>>> >>>> Bernhard >>>> >>>> Am 14.10.2014 02:49, schrieb Mike Flannigan: >>>> >>>> >>>>> I am also using QGIS 2.4 64b Chugiak on Windows 7. >>>>> The same thing happens to me. Even when I create >>>>> a line layer with only 11 lines and try to clip 3 >>>>> of them with a polygon layer, the progress bar just >>>>> goes back and forth for ever. >>>>> >>>>> I didn't run it for hours to see what would eventually >>>>> happen. >>>>> >>>>> Mike >>>>> >>>>> >>>>> I might be doing something wrong. >>>>> >>>>> On 10/13/2014 8:02 AM, [email protected] wrote: >>>>> >>>>>> Hi, >>>>>> I am trying to clip a road network by a polygon in a script using the >>>>>> algorithm 'qgis:clip'. The result seems to be quite ok but it takes an >>>>>> incredible long time to produce, about 14 hours (!). The road network >>>>>> shapefile consists of about 5000 features (not very many, I believe) >>>>>> and >>>>>> the clipping shapefile consists of one single polygon. When using >>>>>> Vector => >>>>>> Geoprocessing Tools => Clip from the QGIS menu, the time required is >>>>>> about >>>>>> the same. Does anyone have a clue why it takes so long time? Are there >>>>>> other clip tools that I may try? I?ve been looking at the >>>>>> 'gdalogr:ogr2ogr' >>>>>> algorithm and its clipsrc function but not got it to work properly >>>>>> yet. I?m >>>>>> using QGIS 2.4 Chugiak on Windows 7 with 2.5 GHz processor. Thankful >>>>>> for >>>>>> all hints that may help, >>>>>> /Jonas >>>>>> >>>>> >>>>> >>>> >>>> __________ Information from ESET Mail Security, version of virus >>>> signature database 10558 (20141014) __________ >>>> >>>> The message was checked by ESET Mail Security. >>>> http://www.eset.com >>>> >>>> >>>> >>>> _______________________________________________ >>>> Qgis-user mailing list >>>> [email protected] >>>> http://lists.osgeo.org/mailman/listinfo/qgis-user >>>> >>> >>> >> >> _______________________________________________ >> Qgis-user mailing list >> [email protected] >> http://lists.osgeo.org/mailman/listinfo/qgis-user >> > >
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