[GRASS-user] topological errors in v.extract results

[Markus Metz]

On Wed, Aug 17, 2016 at 11:54 AM, Blumentrath, Stefan
<Stefan.Blumentrath at nina.no> wrote:
> Short update: I see that the difference between number of areas and number
> of centroids is already present after v.in.ogr…
>
> Is that correct?
>
> Is not an area defined as a closed boundary with a centroid inside? Should
> not then the number of centroids be equal to the number of areas?

Areas without centroid are generally ok, they are holes inside other
areas, equivalent to inner rings of shapefile polygons. As long as
there are no warnings in the output of v.in.ogr or v.build, there are
no topological errors.
>
>
>
> I am using GRASS GIS 7.0.4 on Ubunut 14.04 LTS BTW.
>
>
>
> I try to compare with GRASS GIS 7.1 but import there is painfully slow.
>
> So I had at: https://trac.osgeo.org/grass/ticket/2185
>
> However, I use exactly the same data, from the same database, on the same
> (local) harddrive in 7.1 and it is just !much! slower than 7.0.4 on
> import... Snapping vertices Step 1 takes significantly longer than with
> 7.0.4

There is no GRASS 7.1, so I guess you mean 7.2 or trunk. Are you using
the environment variable GRASS_VECTOR_LOWMEM? This variable affects
snapping only in 7.2 and trunk: less memory but longer processing
time.

Markus M
>
>
>
> Cleaning topology in 7.1 from a GRASS vector map earlier imported with
> 7.0.4svn is BTW not noticeably slower in 7.1 compared to 7.0.4...
>
>
>
> I am glad for any hints,
>
> Stefan
>
>
>
>
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