[GRASS-user] How to link or combine adjacent vector lines

Stefan Luedtke sluedtke at gfz-potsdam.de
Sun Feb 12 16:20:35 EST 2012

That did the trick, almost.

They join each other -so v.build polylines ... worked, but, the table is
exactly the same as it was before. The command output said, that the
number of lines was reduced to almost 50%. Furthermore, if I check the
cat number next to the lines (via d.vect) it looks fine for both
methods, first and multi. But the table does not show any diffs and
holds the same number of entries like the original one. I could not find
anything about that in the manual. 

Anyway, thanks for hints, that helped a lot. 


On Sun, 2012-02-12 at 10:56 -0800, Hamish wrote: 

> Stefan wrote:
> > Thanks for the  detailed answer, but, my problem is much more trivial.
> > I attached a screenshot to make myself more clear.
> > /* The numbers refer to the categories of each line segment */
> > the tributary with cat 69 is fine, but the man channel consists of
> > multiple lines, and, in fact, a lot of tributaries look similar.
> ...
> > The task would be, to tell GRASS, to combine all lines of the main
> > channel, for this example.
> ok. do they overlap or join end-to-end?
> if they join, try Markus M's suggestion of v.build.polylines.
> if they overlap, try 'v.clean tool=rmdupl'
> Hamish
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