[Qgis-user] Qgis-user Problem splitting polygons with line layer

[Bernd Vogelgesang]

Thanx guys for your input,

check validity brought up no problems, fix geometries did not help.

But, simply using the Linies to polygons tool did most of the job for me
and delivered the parcels. I then managed to split the parcels with
other lines to get the subsections.

This tool did not work at all in the past, so I completely erased it out
of my mindset. Obviously, sth changed to the better there. It's a
problem when you already work for too long with QGIS, so you stick to a
behaviour derived from the experiences in the past.

Thanks,

Bernd

On 07.12.20 23:44, Thayer Young wrote:
>   Hi Bernd,
> That sounds like you may have a topology problem, like self intersection.
> Have you tried 'Vector Geometry': 'Fix Geometries' in the Processing Toolbox?In the same place there is also a 'Check validity' tool, which would find the problems for you and then you could fix them manually. The tool gives you options for different standards of validity.Another possibility is that you have mixed geometry types. You might be able to fix that with GRASS: v.type or Processing:'Vector geometry': 'Convert geometry type'
> In PostGIS you would check if the imported geometry column is SELECT id FROM dwg_table WHERE NOT ST_IsSimple(geom)or: SELECT ST_GeometryType(geom) FROM dwg_table GROUP BY ST_GeometryType(geom).
> -Thayer
>
>      On Monday, December 7, 2020, 01:58:04 PM EST, qgis-user-request at lists.osgeo.org <qgis-user-request at lists.osgeo.org> wrote:
> Date: Mon, 7 Dec 2020 19:57:19 +0100
> From: Bernd Vogelgesang <bernd.vogelgesang at gmx.de>
> To: qgis-user <qgis-user at lists.osgeo.org>
> Subject: [Qgis-user] Problem splitting polygons with line layer
> Message-ID: <82a7c751-29c2-9906-25e6-9038979865ef at gmx.de>
> Content-Type: text/plain; charset="utf-8"; Format="flowed"
>
> Hi,
>
> I need to split a polygon with a line layer (representing parcel
> boundaries ).
>
> Using "Split with lines", the process always stops at 12% and there is
> no progress visible. The lines are imported from a CAD dwg as a
> CompoundCurveZ (never had to do with this before)
>
> My goal is to "cut" the polygon, so I retrieve parcels of a specific
> area again.
>
> With other line layers from this dwg ist no problem spliting the
> polygon, only the parcel boundaries won't work.
>
> Does anybody have an idea what could be the cause of this problem, what
> I other tools I could try or if I have to proprocess the lines
> beforehand with other tools?
>
> Hoping for enlightment (and having a deadline tomorrow)
>
> Bernd
>
>