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

[Markus Neteler]

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
>
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>
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-- 
Markus Neteler, PhD
https://www.mundialis.de - free data with free software
https://grass.osgeo.org
https://courses.neteler.org/blog