[GRASS-user] How to categorize my areas

Moritz Lennert mlennert at club.worldonline.be
Tue Dec 15 00:15:52 PST 2015

On 15/12/15 00:22, Martin Landa wrote:
> Hi,
> 2015-12-15 0:18 GMT+01:00 Alec Ventura <alecventura at hotmail.com>:
>> I run the v.buffer with the -t flag and everything is ok now
> I wonder if attributes should be copied by default (without need to
> set up any flag).

v.buffer fusions the geometries of buffers by default. Keeping the 
attribute table does not make sens in that case as one buffer geometry 
can be the result of many different input geometries. This also means 
that you cannot retrieve the buffer of a specific input geometry.

When you use the -t flag, buffers are cut up into separate parts and 
each one that is the result of several overlapping buffers has multiple 
categories. As the man page says: "The resulting buffer areas can have 
multiple categories, and multiple buffer areas can have the same 
category. The buffer for the input feature with category X can thus be 
retrieved by selecting all buffer areas with category X".

Keeping in mind GRASS' topological vector format the current behavior 
seems the most adequate to me.


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