[GRASS-user] speeding up v.overlay

[Stuart Gralton]

Hi Markus,
Thank you for your reply.

This is the original vector:

v.db.connect -p cont
Vector map <cont at PERMANENT> is connected by:
layer <1> table <cont> in database
</home/stuart/grassdata/aawt_mga55/PERMANENT/dbf/> through driver <dbf> with
key <cat>


The v.split command and output:

v.split input=cont output=contSplit length=10000

 100%
Building topology for vector map <contSplit>...
Registering primitives...
37377 primitives registered
2176557 vertices registered
Building areas...
 100%
0 areas built
0 isles built
Attaching islands...
Attaching centroids...
 100%
Number of nodes: 38377
Number of primitives: 37377
Number of points: 0
Number of lines: 37377
Number of boundaries: 0
Number of centroids: 0
Number of areas: 0
Number of isles: 0


Proof that there is no attribute table:

v.db.connect -g contSplit
ERROR: Database connection for map <contSplit at PERMANENT> is not defined in
DB file


I hope that this is this what you were after.

Thanks,
Stuart









On Tue, Aug 24, 2010 at 5:22 PM, Markus Metz <
markus.metz.giswork at googlemail.com> wrote:

> Stuart Gralton wrote:
> > Hello Everyone,
> >
> > I am trying to use v.overlay to clip contour lines for a specific area.
> The
> > contour lines were imported into GRASS from a shapefile which is about
> 33Mb.
> > The query was as follows:
> >
> > v.overlay ainput=contour atype=line binput=boundingbox
> output=contour_clip
> > operator=and
> >
> > The operation took 16 hours to complete, which seems excessive. Is there
> > anything that I can do to speed things up?
> >
> > I am aware of v.split, v.select, v.clean as suggestions from other posts
> as
> > ways of increasing performance. Unfortunately none of these helped me
> very
> > much:
> >
> >     v.split seems to drop the attribute table (but it has amazing effects
> on
> > performance).
>
> v.spllt does copy all attribute tables. Can you post the output of
> v.db.connect -p or v.db.connect -g for the original vector and the
> output of v.split?
>
> Markus M
>
> >     v.select helps a little, but due to the nature of the data, not many
> > features are removed.
> >     v.clean did not have any effect. The data is from the government, and
> is
> > already of high quality.
> >
> >
> > Is there anything that I am missing? Or is there any way to preserve the
> > attribute table when using v.split?
> >
> > Thanks in advance,
> > Stuart
> >
> >
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-user
> >
> >
>
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