[GRASS-user] converting lines to polygons

Markus Metz markus.metz.giswork at googlemail.com
Tue Sep 28 04:00:18 EDT 2010

Micha Silver:
> Markus Metz wrote:
>> Micha Silver wrote:
>>> In any case, importing polygon shapefiles first as lines (not
>>> boundaries),
>>> doing the topology cleanup, and then convert to boundaries and add
>>> centroids
>>> seems to be the smoother way to go.
>> I object because
>> 1. you would need to replicate the cleaning steps done by v.in.ogr
>> which has, amongst others, a snapping option
> I never noticed that option.

> Still, importing unclean shapefile polygons, and correcting the topology is
> often accompanied by much hair pulling...

Unfortunately yes. If data providers would only provide clean data...

I have partially good news: v.in.ogr in 6.4.1 and above is faster and
produces cleaner and smaller output. Further on, it shows progress
when cleaning polygons, indicating that something is happening.
Previously (up to 6.4.0), it went silent for quite some time on larger
polygon imports which annoyed me considerably, I want to see that
something is happening.

Markus M

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