Am Mittwoch, 21. Dezember 2005 15:17 schrieb Wolfgang Qual:
Hello Otto,
so you do not have the possibility to choose layer property "1_polygon" in
the "add grass vector layer dialog" of QGIS? I just tried the same command
(v.buffer in=roads out=roadsbuf buffer=20) and it looks ok. If I choose
0_polygon, only the area between the roads is drawn by QGIS.
Hi
Sorry - I didn't use QGIS but GRASS to visualize the resulting map. QGIS
visualizes those data differently. In GRASS the closed lines are displayed as
an area but only exist as a boundary without any information.
Some time ago there was a discussion about when to display a closed line as an
area and when not. I still do not know (don't remember), why in GRASS those
closed boundaries, in my opinion no areas, are displayed.
Can someone help out again and explain? I think there was a good reason for
this - right?
thanks
Otto
Best regards,
Wolfgang
-----
> --- Ursprüngliche Nachricht ---
> Von: Otto Dassau <dassau@gdf-hannover.de>
> An: "Wolfgang Qual" <Wolfgang.Qual@gmx.net>
> Kopie: grasslist@baylor.edu
> Betreff: [GRASSLIST:9591] Re: v.buffer: area boundary around line?
> Wanted: howto!
> Datum: Wed, 21 Dec 2005 13:45:47 +0100
>
> Am Mittwoch, 21. Dezember 2005 13:19 schrieb Wolfgang Qual:
> > Hi Otto, hi list.
>
> Hi,
>
> the problems I described still exist with the spearfish dataset:
>
> v.buffer in=roads out=roadsbuf buffer=20 type=line
> v.buffer in=roads out=roadsbuf buffer=20
>
> it doesn't make a difference in the result.
>
> Otto
>
> > Sorry, I think I was too fast...:
> > If I *do not specify "type"* in the command for v.buffer (v.buffer
> > in=ausschnitt out=buff_ausschnitt bufcol=gesamtbr)
> > I do get a correct result. I can add this vector to my QGIS-Map (Layer
> > 1_polygon) - works.
> > However: how can I display this in GRASS (d.mon, d.vect)? If I try
>
> d.vect,
>
> > the area inside the ring is also displayed!
> >
> > Wolfgang
> >
> > Buffer is drawn around the feature (line).
> >
> > > --- Ursprüngliche Nachricht ---
> > > Von: Otto Dassau <dassau@gdf-hannover.de>
> > > An: "Wolfgang Qual" <Wolfgang.Qual@gmx.net>
> > > Kopie: grasslist@baylor.edu
> > > Betreff: Re: [GRASSLIST:9588] v.buffer: area boundary around line?
> > > Wanted: howto!
> > > Datum: Wed, 21 Dec 2005 12:17:50 +0100
> > >
> > > Am Mittwoch, 21. Dezember 2005 11:22 schrieb Wolfgang Qual:
> > > > Hi List,
> > >
> > > Hi,
> > >
> > > > I tried to create a new area boundary around a line theme. Thought
>
> it
>
> > > would
> > >
> > > > be easy to do it like this:
> > > >
> > > > v.buffer in=ausschnitt out=buff_ausschnitt bufcol=gesamtbr
> > > > type=boundary
> > >
> > > I also tried with the spearfish location and a CVS snapshot from
> > > today and got
> > > similar strange results, where the lines (roads) describe a closed
>
> ring.
>
> > > v.buffer in=roads out=roadsbuf buffer=20 type=line
> > >
> > >
> > > Otto
> > >
> > > > But GRASS won't create a new theme. After that, I tried to first
>
> create
>
> > > a
> > >
> > > > line buffer theme (works fine) and then convert it to a area
>
> boundary
>
> > > theme
> > >
> > > > using v.type. However, the new area boundary theme does not have
> > > > the
> > >
> > > shape
> > >
> > > > of the line buffer theme.
> > > >
> > > > BTW, the line theme looks like this (street network):
> > > >
> > > > ------------------
> > > >
> > > > | | ...but I get s.th. XXXXXXXXXXXX
> > > > | | like this: XXXXXXXXXXXX
> > > >
> > > > -------------- XXXXXXXXXXXX (area
> > > > inside)
> > > >
> > > > I would greatly appreciate to receive some hints...
> > > >
> > > >
> > > > Best wishes,
> > > > Wolfgang
> > >
> > > --
> > > GDF Hannover - Solutions for spatial data analysis and remote sensing
> > > Office Hannover - Mengendamm 16d - D - 30177 Hannover
> > > Internet: www.gdf-hannover.de, Email:
>
> info@gdf-hannover.de
>
> > > Phone : ++49.(0)511.39088507, Fax: ++49.(0)511.39088508
>
> --
> GDF Hannover - Solutions for spatial data analysis and remote sensing
> Office Hannover - Mengendamm 16d - D - 30177 Hannover
> Internet: www.gdf-hannover.de, Email: info@gdf-hannover.de
> Phone : ++49.(0)511.39088507, Fax: ++49.(0)511.39088508
--
GDF Hannover - Solutions for spatial data analysis and remote sensing
Office Hannover - Mengendamm 16d - D - 30177 Hannover
Internet: www.gdf-hannover.de, Email: info@gdf-hannover.de
Phone : ++49.(0)511.39088507, Fax: ++49.(0)511.39088508