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

[Maciek Sieczka]

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