vectors: lines to polygons

Michel Wurtz - ENGEES/CEREG mw at
Thu Jun 3 10:37:49 EDT 1999

Agustin Lobo wrote:
> I have imported a vegetation map of Europe.
> Nevertheless, it was digitized as LINES, not
> as polygons. Therefore, I have now a vector
> map in which the lines should be attached
> to make polygons. I've checked abd is not just
> that each polygon is made out of on single line,
> so it's not just a question of replacing "L"
> by "A" in the ascii vector format.
> The question (and I suspect the answer...):
> is there an automatic procedure to combine the
> lines into polygons?, i.e., if we have:

Yes, because with Grass, a single line can be used for 2 areas,
one on each side.
Once you change the 'L' to 'A' in your ascii vector file,
run to made a binary vector file and then run, which will compute the topology, hence creating
your areas ().

You will then need to give each area a label with v.digit,
unless you have a site file giving you a point location
(with the number you will use for polygon attribute) inside
each area to be labelled, in which case you can create a
dig_att file before running

Michel Wurtz    ENGEES - CEREG
                1, quai Koch - BP 1039, F-67070 STRASBOURG cedex
                Tel: +33  Fax: +33

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