[GRASSLIST:1030] Re: GRASS and vector lines: how can I change the direction of digitized lines?

[wqual]

Good Morning Otto, hi list.
thank you very much for this hint. BTW, I found out that the mapserver needs a 
special option specified to display the direction correctly (see [1] for 
details]: GAP must be set to something negative. 

Best regards,

Wolfgang

[1] 
http://mapserver.gis.umn.edu/data2/wilma/mapserver-users/0310/msg00441.html

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Am Freitag 28 April 2006 pH:00:14 nachmittags/abends schrieb Otto Dassau:
> Am Freitag, 28. April 2006 13:35 schrieb wqual:
> > Hi GRASS list,
> > I have two shapefiles which represent the average traffic load for some
> > streets in Munich. The traffic is divided into "incoming" and "outgoing"
> > traffic.
> > What I would like to do: display this map in my mapserver application
> > (using ttf-arrow symbols).
> > However, mistakes were made during digitizing, thus the direction of the
> > lines is wrong (looks like this
> >
> > ->------------>----------->
> > ->------------>----------->
> >
> > and should be something like
> >
> > <--------<------------<-------
> >
> > >--------->------------>-------
> >
> > ).
> > Therefore my question(s):
> > a) is it possible to display these directions within GRASS (I tried to do
> > this in ArcView before)
>
> Hi Wolfgang,
>
> the parameter in d.vect is display=dir
>
> e.g.: d.vect roads display=dir,shape
>
> > b) how can I change the direction of the lines in GRASS?
>
> as far as I know you can't, because you define the direction when you
> digitize a line from node a ---->----- node b. But you can use columns in
> the appendant attribute table to assign different values for each direction
> (e.g. speed).
>
> see ->  g.manual v.net.path
> ...
> afcolumn   Arc forward/both direction(s) cost column
> abcolumn   Arc backward direction cost column
>
> regards,
>   Otto
>
> > I would be most grateful for some comments on this issue.
> >
> > Best regards,
> >
> > Wolfgang