Hi - I am trying to create buffers for large (~1GB) line and polygon
vector files. I tried v.buffer but after letting it run overnight with
no apparent progress I killed the process. I'm not aware of any software
capable of buffering large vector files on a modest computer so that
wasn't a big surprise. I then converted the vector to a large (23GB)
raster file and am now trying r.buffer. I ran some tests on small images
but can't figure out how the distance parameter works when an image has
latitude/longitude coordinates. My image is in a geographic
(latitude/longitude) projection with a resolution of 0.00025 (~27.75m)
and I'd like to create a buffer with a distance of 0.0018 (~200m). How
to I do that without projecting my image? I'm using GRASS 7.0 on 64 bit
Ubuntu 10.04.
The manual seems to indicate that I can choose the distance units so I
tried distances=200.0 and units=meters but that converted the entire
image to a buffer so the distance was clearly too large. I then tried
distances =0.0018 (the manual states that r.buffer uses "ellipsoidal
geodesic distance measure for latitude/longitude locations) and
units=meters but that didn't create any buffer. My last test was to use
the number of pixels to define the distance so I tried distances =7.2
and units=meters and that created a buffer roughly one pixel wide.
Any thoughts on how to buffer a large vector or raster data set would be
appreciated.
All the best,
Ned
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