[GRASS-dev] v.kernel output question

[Isaac Ullah]

Hi all,

I'm running an experiment to simulate the distribution of microartifacts
(less than 1mm sized artifacts) on ancient housefloors. The simulations
essentially produce vector point files where each point is the location of a
single microartifact. These are arranged as clusters across a rectangular
space (region extents), and there are several hundred thousand points in
each vector point file. To simulate archaeological recovery of these
microartifacts, I am using v.kernel to create density maps of the points at
different resolutions. My question here concerns the output of v.kernal. Do
the numbers in an output v.kernal density map represent density over some
standard unchanging unit (ie. map unit), or is it density per the current
resolution? The reason I'm asking is that the actual numbers in the output
maps do not seem to be changing even though the resolution is different. For
example, if I set the resolution to 10cm (0.1m), I get values ranging from 0
to over 2000. When I then change the resolution to 1m, I still get values
ranging from 0 to 2000. The pattern of distribution between the maps is
similar, so that seems to be working. This all makes me think that v.kernel
is calculating the density of points *per some standard unit* rather than
just counting the number of points in one cell given the current raster
resolution (set in g.region). If the later was occurring, then I would
expect an output map with raster resolution of 1m to have much higher counts
per cell than one with resolution of only 10cm. The man page for v.kernel
does not mention anything about this (and in fact pretty mentions very
little at all). So I guess my question is: Can anyone confirm for me that
v.kernel output will be density per map unit, or density per current
resolution settings? I just need to know so that I can quantify my results
properly. And while we are on it, can anyone also explain to me what the
"standard dev" option in v.kernel actually does? Like I said before, the man
page is lacking in these details...

Any help will be greatly appreciated!

Cheers,

-- 
Isaac I Ullah, M.A.

Archaeology PhD Candidate,
ASU School of Evolution and Social Change

Research Assistant,
Mediterranean Landscape Dynamics Project
***************************************************
isaac.ullah at asu.edu
ullah at archaeologist.com

http://www.public.asu.edu/~iullah
***************************************************
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