[GRASSLIST:6122] Re: dissolve common boundary

[Moritz Lennert]

On Thu, March 10, 2005 19:56, ivan marchesini said:
> Dear Hamish, dear Markus...
> I have still problem to dissolve boundaries...
> I will try to explain better the problem...
> I have a lot of areas (a reclassified landuse map) in a vector map...
> some of these poligon have the same values in a column of the
> database...
> for example: two touching areas have the same code=31
> I would like that these two ares will became one single area .... and
> the same for the other touching areas which have equal code values....
>
> I have tried
> v.extract -d input=landuse output=landuse_diss type=area new=-1
>
>
> but the output is exactly the same map as the input
>
> where I'm wrong???
> can you help me??

It dissolves, if the category values are equal, not any value in the attribute
table. So, you will first have to use v.reclass with the 'column' option to
take new category values from the desired column and then v.extract -d on the
resulting map.

Moritz