[GRASSLIST:9594] Re: v.buffer: area boundary around line? Wanted: howto!

[Tom Russo]

On Wed, Dec 21, 2005 at 11:22:33AM +0100, we recorded a bogon-computron collision of the <Wolfgang.Qual at gmx.net> flavor, containing:
> Hi List,
> 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
> 
> 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...

I'm not exactly sure why this is, but apparently d.vect displays these areas
by showing both categorized polygons (the ones you intended) and 
uncategorized polygons (the ones that fill all the spaces in between).  If you 
try
  d.vect map=buff_ausschnitt where="cat<>0"

I think you'll get only the areas you really wanted.

-- 
Tom Russo    KM5VY     SAR502  DM64ux         http://www.swcp.com/~russo/
Tijeras, NM  QRPL#1592 K2#398  SOC#236 AHTB#1 
 "The only thing you can do easily is be wrong, and that's hardly
  worth the effort." -- Norton Juster