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

[Hanlie Pretorius]

Ok, thanks.

The other three corners were rounded, but I eliminated the rounding
with the -s option.

Hanlie

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
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>