[GRASS-user] Strange behavior with v.patch

[Peter Tittmann]

Thanks, Markus. That solves the problem.

On Sat, Dec 9, 2017, 8:33 AM Markus Metz <markus.metz.giswork at gmail.com>
wrote:

>
>
> On Fri, Dec 8, 2017 at 11:46 PM, Peter Tittmann <ptittmann at gmail.com>
> wrote:
> >
> > Hi,
> >
> > In attempting to patch two polygon layers I am confused as to the the
> results i am getting. My understanding of v.patch is that it would be
> similar to a `union` operator in SQL (not a spatial union) wherein rows of
> one or many tables are concatenated to a new table. However, the results
> i’m getting are not in aligned with that expectation.
> >
> > Here is a link to an image of the two tables (one orange, one green) (
> https://pasteboard.co/GXjWm6P.png )
> >
> > The second image ( https://pasteboard.co/GXjVSQE.png) is a result of
> >
> > # combine all clustered polygons into one table
> > gsc.parse_command('v.patch',
> >                   flags = 'e',
> >                   overwrite = True,
> >                   verbose= True,
> >                   input = <green>, <orange>,
> >                   output = ssPoly)
> >
> > The blue represents the result of the v.patch command. I don't
> understand why all of the area covered by the two source vectors is not
> covered in the patched vector.
>
> You have patched two area vectors together and the output contains most
> likely topological errors. Try to clean the output of v.patch with v.clean
> -c tool=break type=boundary.
>
> HTH,
>
> Markus M
>
> >
> > My only thought it it has something to do with the categories, or keys?
> >
> > Thanks in advance for any guidance.
> >
> > Peter
> >
> >
> >
> > _______________________________________________
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> > grass-user at lists.osgeo.org
> > https://lists.osgeo.org/mailman/listinfo/grass-user
>
>
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