[GRASS-user] [GRASS-dev] how to make non-merged buffers?

[Michael Barton]

Thanks.

Michael
____________________
C. Michael Barton
Director, Center for Social Dynamics & Complexity 
Professor of Anthropology, School of Human Evolution & Social Change
Arizona State University

voice: 	480-965-6262 (SHESC), 480-727-9746 (CSDC)
fax:          480-965-7671 (SHESC),  480-727-0709 (CSDC)
www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu











On Jun 4, 2013, at 12:17 PM, Markus Metz <markus.metz.giswork at gmail.com>
 wrote:

> On Tue, Jun 4, 2013 at 7:54 PM, Michael Barton <Michael.Barton at asu.edu> wrote:
>> So this is odd.
>> 
>> I have 166 points, with a few cases where 2 points are in the same location
>> I created a set of circular buffers around the points with
>> 
>> v.buffer -t input=neolithic_sites type=point output=sites5km distance=5000
>> 
>> This indeed created a set of overlapping (non-merged), circular buffers.
>> 
>> BUT, it creates 212 areas and 100 islands according to the command output and metadata report (v.report).
>> 
>> There are only 166 attribute table entries.
>> 
>> So what are the extra areas and the islands?
> 
> The 7.0 -t flag preserves the categories of the input features and
> cleans topology. Areas in the output can have more categories, one for
> each input feature in case of overlapping buffers. This also means
> that in case of overlapping buffers there are more output areas than
> input features, but you have clean topology and you can extract single
> buffers. See the example in the 7.0 manual.
> 
> Markus M
>> 
>> Michael
>> ____________________
>> C. Michael Barton
>> Director, Center for Social Dynamics & Complexity
>> Professor of Anthropology, School of Human Evolution & Social Change
>> Arizona State University
>> 
>> voice:  480-965-6262 (SHESC), 480-727-9746 (CSDC)
>> fax:          480-965-7671 (SHESC),  480-727-0709 (CSDC)
>> www: http://www.public.asu.edu/~cmbarton, http://csdc.asu.edu
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> 
>> On Jun 3, 2013, at 12:20 AM, Markus Metz <markus.metz.giswork at gmail.com> wrote:
>> 
>>> On Mon, Jun 3, 2013 at 1:08 AM, Hamish <hamish_b at yahoo.com> wrote:
>>>> Michael wrote:
>>>>>> Is there a way to create buffers around features that
>>>>>> overlap when the features are near to each other instead of
>>>>>> merging?
>>>> 
>>>> Markus M wrote:
>>>>> In GRASS 7, with v.buffer -t
>>>> 
>>>> for the sake of completeness, in 6.3.0 you could do this with
>>>> the debug= option, but that did not continue into the replacement
>>>> 6.4 module. There you'd have to run it in a loop then combine with
>>>> v.patch.
>>> 
>>> To be precise, the 6.3 debug= option as well as the v.patch solution
>>> produce really overlapping areas with broken topology. The 7.0 -t flag
>>> preserves the categories of the input features and cleans topology.
>>> Areas in the output can have more categories, one for each input
>>> feature in case of overlapping buffers. Thus you have clean topology
>>> and you can extract single buffers. See the example in the 7.0 manual.
>>> 
>>> Markus M
>>