[GRASS-user] One chamfered corner with v.buffer on an extents rectangle

[Markus Metz]

On Wed, Apr 20, 2011 at 4:41 PM, Hanlie Pretorius
<hanlie.pretorius at gmail.com> wrote:
> Ok, thanks.
>
> The other three corners were rounded, but I eliminated the rounding
> with the -s option.

Oops, I missed that -s option. Anyway, v.buffer is not chopping off
corners also with the -s option in 6.5.

Markus M

>
> 2011/4/20, Markus Metz <markus.metz.giswork at googlemail.com>:
>> On Wed, Apr 20, 2011 at 2:21 PM, Hanlie Pretorius
>> <hanlie.pretorius at gmail.com> wrote:
>>> Hi,
>>>
>>> I'm working in GRASS 6.4.0 and using v.buffer applied to an extents
>>> rectangle. For some reason v.buffer is producing one chamfered corner
>>> in the buffered vector.
>>>
>> The bug concerning the southwest corner is already fixed in 6.5,
>> awaiting ok for backport to 6.4.2.
>>
>> The 3 other corners are also incorrect, I guess they should be
>> rounded. At least they are with other areas of similar shape.
>>
>> Markus M
>>
>>
>>> The command I used was:
>>> v.buffer -s -c --overwrite input=c83a_extents at PERMANENT
>>> output=c83a_extents_5km_buffer at 20m_DEM distance=5000.
>>> Buffering lines...
>>> Buffering areas...
>>> Building topology for vector map <c83a_extents_5km_buffer>...
>>> Registering primitives...
>>> 1 primitives registered
>>> 12 vertices registered
>>> Number of nodes: 1
>>> Number of primitives: 1
>>> Number of points: 0
>>> Number of lines: 0
>>> Number of boundaries: 1
>>> Number of centroids: 0
>>> Number of areas: -
>>> Number of isles: -
>>> Snapping boundaries...
>>> Breaking boundaries...
>>> Removing duplicates...
>>> Attaching islands...
>>> Building topology for vector map <c83a_extents_5km_buffer>...
>>> Building areas...
>>> 1 areas built
>>> 1 isles built
>>> Attaching islands...
>>> Number of nodes: 1
>>> Number of primitives: 1
>>> Number of points: 0
>>> Number of lines: 0
>>> Number of boundaries: 1
>>> Number of centroids: 0
>>> Number of areas: 1
>>> Number of isles: 1
>>> Number of areas without centroid: 1
>>> Attaching centroids...
>>> Building topology for vector map <c83a_extents_5km_buffer>...
>>> Attaching centroids...
>>> Number of nodes: 2
>>> Number of primitives: 2
>>> Number of points: 0
>>> Number of lines: 0
>>> Number of boundaries: 1
>>> Number of centroids: 1
>>> Number of areas: 1
>>> Number of isles: 1
>>> Building topology for vector map <c83a_extents_5km_buffer>...
>>> Registering primitives...
>>> 2 primitives registered
>>> 13 vertices registered
>>> Building areas...
>>> 1 areas built
>>> 1 isles built
>>> Attaching islands...
>>> Attaching centroids...
>>> Number of nodes: 2
>>> Number of primitives: 2
>>> Number of points: 0
>>> Number of lines: 0
>>> Number of boundaries: 1
>>> Number of centroids: 1
>>> Number of areas: 1
>>> Number of isles: 1
>>> (Wed Apr 20 14:08:46 2011) Command finished (1 sec)
>>>
>>> I have placed a screenshot of the outcome on the web
>>> <http://www.nedbib.za.net/v.buffer.png>. The region was set to the DEM
>>> raster in the background. The black triangle is the extents and the
>>> red one the buffered polygon.
>>>
>>> Does someone know why v.buffer would create such a chamfered corner.
>>> I've played around with selecting different feature types and adding a
>>> minor distance value, but I always get the same result.
>>>
>>> Thanks
>>> Hanlie
>>> _______________________________________________
>>> grass-user mailing list
>>> grass-user at lists.osgeo.org
>>> http://lists.osgeo.org/mailman/listinfo/grass-user
>>>
>>
>