[GRASS5] [bug #3427] (grass) v.buffer makes the buffers TWICE the desired size

[Michael Barton]

Maciek,

This does sound weird. For a closed line, it seems that it SHOULD be just
like an open line--i.e., creating a donut 1000m wide extending on both sides
of the closed line.

Michael


On 7/17/05 10:17 AM, "Maciek Sieczka" <werchowyna at epf.pl> wrote:

> From: "Michael Barton" <michael.barton at asu.edu>
> 
>> The buffer distance is the distance the buffer extends outwards from the
>> object being buffered. For a stream, then, a 500m buffer distance, would
>> produce a buffer that extends 500m outward from the stream. This would
>> make
>> a buffer polygon 1000m wide (500+500). The same buffer distance around a
>> point would create a circle 500m in radius (1000m in diameter).
> 
> Michael, You have missunderstood the point.
> 
> My input "border" is a *closed* line. When I v.buffer it for 500m, I get a
> polygon inside of it (BTW - should it be inside indeed?) at the distance of
> 1000m from the line. If I have not explained it enough, please grab the file
> if you can and try v.buffer input=border output=border_half_km type=line
> layer=1 buffer=500.
> 
> I know the best workaround is to convert the boundary line to an area
> polygon and then v.buffer on that, which works fine - the output is a buffer
> at 500m from the input, outside of it. The problem is it seems that v.buffer
> cannot handle closed lines (i.e. area boundaries, closed elevation contours)
> properly.
> 
> Maciek
> 
>> Around a
>> polygon, it would create a zone 500m wide around the polygon perimeter.
>> 
>> Michael
> 

____________________
C. Michael Barton, Professor of Anthropology
School of Human Evolution and Social Change
PO Box 872402
Arizona State University
Tempe, AZ  85287-2402
USA

Phone: 480-965-6262
Fax: 480-965-7671
www: <www.public.asu.edu/~cmbarton>