Trying to convert lines to polygons

[Juan Bañuls]

Michel Wurtz wrote:

>The areas you create are not labelled (means that v.to.rast will give
>you an empty file).  Snapping doesn't help.  Labelling is done via the
>dig_att file : an entry for each area or line to be labelled made as
>following for an area :
>
>A xxxxxx yyyyyy nn
>
>A means area (L for line), xxxxx and yyyyyy are the coordinates of the
>label point (inside the area), and nn is the area number (> 0).
>
>Try to use v.digit after running v.support.  There is some command
>to show unlabelled areas.  You can label each area interactively.
>If some areas cannot be labelled, look at the nodes around them (and
>zoom)
>If there is some green dots, that's mean that a line doesn't match
>any other. You can snap manualy lines together, solving the unclosed
>polygon problem. After that rerun v.support to label area, and 
v.to.rast
>will work.
>
>If you have some labels in dxf, you can import them in the dig_att file
>with respect to the format showed above (v.digit is sometimes boring 
:-)
Well, a dxf file is just what I have. As you know, 
I'm trying to convert this file containing unlabeled
lines to areas in a shapefile format (this is the 
format needed by the final software, but it is not 
able to generate polygon topology).

By using v.in.dxf I have imported the vector map
to GRASS (**¡the dig_att file hasn't been created!**).
After that (as I've said in the other
mails) I have converted through v.line2area.sh the
most part of the lines (99 %), but some of them
remain "opened" (**I get a warning from it because 
.../dig_cats/DXF.0 does not exist??!!**).

By filtering the imported map with v.trim and 
v.prune (I run v.support with the build option
after these two commads in order to rebuild the 
topology) I get more areas (99.9%), but it still
remain a few lines "opened" (I can see them in 
the Toolbox of v.digit, option "o").


*I don't understand what's the difference between
the lines that are converted and the lines that are
not, because they all are not labeled, and I don't 
know which parameters pass to v.trim and v.prune in 
order to get the topology. 

*If I had all the lines labeled, could I get the 
polygon topology?. If so, how can I label the lines 
automatically?. What do I do after that?.

*I have one point inside of each area that exists in the 
map too (not in dxf but in shape). Could I use it to 
convert the lines?.

*I have generated some areas that were not detected with 
v.digit (labelling areas), but when I rerun v.support after
using v.digit, they turn another time into lines. :-(

*Another thing: I have cleaned my DXF with AutoCAD MAP 2.0;
if I import the new DXF and run v.support, I get ALL the 
areas. Is there any way to clean the map as AutoCAD MAP does? 
(it would be the solution).


Thank you very much for your time and patience. Sincerely,
Juan Bañuls.

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