[GRASS-user] SOLVED: Re: deleting lines by length, from a vector map

Zoltan Szecsei zoltans at geograph.co.za
Sun Dec 1 04:26:13 PST 2019


Hi All,
Thanks go to Markus, Micha and Moritz for contribution.
Having been guided to v.edit, it was quite trivial:

gscript.run_command('v.edit', map=gen, type='line', tool='delete', 
threshold='-1,0,-50', query='length', overwrite=True)

Note the triplet value for Threshold.
Thanks again,
Zoltan

On 2019/11/30 18:43, Markus Neteler wrote:
> Hi Zoltan,
>
> On Sat, Nov 30, 2019 at 4:05 PM Zoltan Szecsei <zoltans at geograph.co.za> wrote:
>> Hi,
>> I'm trying to write my first Grass python script to load Shape files and
>> delete all lines shorter than 50m
>> I'm trying various permutations of the command below, but  no success
>> (No error message and no lines deleted).
>> Any guidance would be welcome.
>>
>> gscript.run_command('v.extract','r',input=gen,output=lin,  where="(
>> $LENGTH > 50 )",overwrite=True)
>> gscript.run_command('v.out.ogr', 'sce2', input=lin, type='line',
>> output=dir_rclout + rcl + '.shp', format='ESRI_Shapefile',
>> output_type='line',overwrite=True)
> (writing in a rush, just to send some ideas)
>
> Perhaps something like this:
>
> v.edit:
> tool=delete
>     Delete selected features from vector map
>     https://grass.osgeo.org/grass78/manuals/v.edit.html
>
> with the related WHERE condition.
>
> The attribute-from-geometry for this WHERE condition you may get with
> https://grass.osgeo.org/grass78/manuals/v.univar.html
>
> For the line lengths, perhaps to consider
> https://grass.osgeo.org/grass78/manuals/v.build.polylines.html
>
>> Thanks and regards,
>> Zoltan
>> PS: Should these type of questions go to grass-dev ??
> Here is fine as well!
>
> Cheers
> Markus
>
>> --
>>
>> =============================================
>> Zoltan Szecsei GPrGISc 0031
>> Geograph (Pty) Ltd.
>> GIS and Photogrammetric Services
>>
>> P.O. Box 7, Muizenberg 7950, South Africa.
>>
>> Mobile: +27-83-6004028     (WhatsApp only)
>> Qatar:  +974 5083 2722     www.geograph.co.za
>> =============================================
>>
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>
>

-- 

=============================================
Zoltan Szecsei GPrGISc 0031
Geograph (Pty) Ltd.
GIS and Photogrammetric Services

P.O. Box 7, Muizenberg 7950, South Africa.

Mobile: +27-83-6004028     (WhatsApp only)
Qatar:  +974 5083 2722     www.geograph.co.za
=============================================



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