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

[Michael Barton]

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). Around a
polygon, it would create a zone 500m wide around the polygon perimeter.

Michael


On 7/16/05 2:55 AM, "Request Tracker" <grass-bugs at intevation.de> wrote:

> this bug's URL: http://intevation.de/rt/webrt?serial_num=3427
> -------------------------------------------------------------------------
> 
> Subject: v.buffer makes the buffers TWICE the desired size
> 
> Platform: GNU/Linux/i386
> grass obtained from: CVS
> grass binary for platform: Compiled from Sources
> GRASS Version: 15.07.2005
> 
> v.buffer input=border output=border_half_km type=line layer=1 buffer=500
> 
> makes the buffer about 1 km wide, though 500m requested
> 
> v.buffer input=border output=border_1_km type=line layer=1 buffer=1000
> 
> makes it about 2 km wide
> 
> Strange. Bug?
> 
> The input "border" you can grab here for testing:
> http://www.biol.uni.wroc.pl/sieczka/udostepnione/border.tar.bz2
> 
> There is no .prj file cause GDAL/OGR cannot parse the "sterea" projection yet.
> In case you need this information:
> 
> GRASS 6.1.cvs (caves_65):~ > g.proj -p
> -PROJ_INFO-------------------------------------------------
> name       : Stereographic
> proj       : sterea
> a          : 6378245
> es         : 0.0066934216
> lat_0      : 51.67083333333333
> lon_0      : 16.67222222222222
> k          : 0.999800
> x_0        : 3703000
> y_0        : 5627000
> towgs84    : 33.4297,-146.5746,-76.2865,-0.35867,-0.05283,0.84354,-0.8407728
> no_defs    : defined
> -PROJ_UNITS------------------------------------------------
> unit       : metre
> units      : metres
> meters     : 1
> 
> GRASS 6.1.cvs (caves_65):~ > g.region -p
> projection: 99 (Stereographic)
> zone:       0
> datum:      
> towgs84=33.4297,-146.5746,-76.2865,-0.35867,-0.05283,0.84354,-0.8407728
> ellipsoid:  a=6378245 es=0.0066934216
> north:      5578761.99643985
> south:      5576874.65677985
> west:       3685399.25248024
> east:       3686946.53094024
> nsres:      1.00018
> ewres:      1.00018
> rows:       1887
> cols:       1547
> 
> 
> 
> -------------------------------------------- Managed by Request Tracker
> 
> 
> 

____________________
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>