[GRASS-user] Re: v.kernel -- how to get useful results

Aren Cambre aren at arencambre.com
Tue Feb 15 21:20:25 EST 2011

> As soon as a raster map is accessed as input or output, the current
> region settings are used (for most modules) as the extents and
> resolution for any raster operations.

If I have a GRASS vector map that is simply an import of PostGIS points (no
attributes), is the region not the same as the entire map?

I looked over the g.region command, and I'm not clear how one gets from
defining a region to v.kernel. v.kernel's documentation (
http://grass.fbk.eu/gdp/html_grass64/v.kernel.html) is not clear on this
point, and it appears that it just takes a vector map as input? Although,
that being said, I'm confused about the *input* and *net* parameters. Is *
input* actually a region and *net* actually the vector map?

Also, how do I even define a region in the first place? Can I draw it using
the map display? Or do I need to write down the coordinates as I hover my
mouse over the NW and SE extents of the area of the vector I want to focus

> In this case it may or may not desirable to run v.kernel on the whole
> vector map, e.g. if you want to try different settings, rather use a
> smaller region that covers only parts of the vector. Once you're happy
> with the results, you can expand the region to cover the whole vector
> with
> g.region vect=<name_of_my_vector> -p

When you say "the vector", is this some other vector map besides the map
with my 2 million points?

Thanks for your help on this!

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