[GRASS-user] removal of duplicate points

[Dylan Beaudette]

On Wednesday 05 March 2008, G. Allegri wrote:
> What's wrong with v.out.ascii? Couldn't you export and then remove
> duplicate points by checking the coordinates? To avoid checking both X and
> Y, these could be summed, so a single check would be enough.
>
> giovanni

I guess v.out.ascii | v.in.ascii isn't so bad afterall. I was hoping for a 
more general approach that didn't involve the loss of the associated 
attribute table. In this case, I only need a simple ID, so the final 
incantation looked something like:

v.to.points -v -i in=blocks_1 out=b1p dmax=75 --o
v.to.points -v -i in=blocks_2 out=b2p dmax=75 --o

# patch them together:
v.patch in=b1p,b2p out=vp --o
v.build vp

# remove duplicate points
# new file does not have an attribute table
v.out.ascii vp | sort -g | uniq | v.in.ascii -t out=veg_points

# add attribute table:
v.db.addtable veg_points

# cleanup
g.remove vect=b1p,b2p,vp

# export to shapefile:
v.out.ogr -e in=veg_points type=point dsn=veg_points.shp

And this got the job done. I wonder how hard it would be to add a similar 
functionality to v.edit-- which would preserve the attribute table.

Cheers,

Dylan

> 2008/3/5, Dylan Beaudette <dylan.beaudette at gmail.com>:
> > Hi,
> >
> > I have some "squares" which are stored as polygons. When converting these
> > to
> > points (v.to.points) I am left with the 5 points (first and last point
> > are duplicated) that define the corners of the "square".
> >
> > Is there a vector module (v.edit / v.clean) that could remove duplicate
> > points? I would like to replace the manual operation with v.digit with
> > something that can be scripted. Note that there are multiple "squares",
> > so a
> > simple v.out.ascii | head -4 | v.in.ascii  would be a little awkward.
> >
> > Ideas?
> >
> > --
> > Dylan Beaudette
> > Soil Resource Laboratory
> > http://casoilresource.lawr.ucdavis.edu/
> > University of California at Davis
> > 530.754.7341
> > _______________________________________________
> > grass-user mailing list
> > grass-user at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/grass-user



-- 
Dylan Beaudette
Soil Resource Laboratory
http://casoilresource.lawr.ucdavis.edu/
University of California at Davis
530.754.7341