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

[Markus Metz]

Aren Cambre :
> I am not getting any responses. :-) Am I doing something really dumb? Is
> this the right forum for this kind of question?

This should be the right kind of forum, but maybe nobody has an idea
about what could be wrong.

Just a guess: maybe no points of the input vector fall into the
current region that is used to write the output raster map?

Markus M

> Thanks,
> Aren
>
> On Sun, Feb 13, 2011 at 8:02 AM, Aren Cambre <aren at arencambre.com> wrote:
>>
>> Maybe I could clarify. Here's the command:
>> v.kernel --verbose input=master_grass7 output=master_grass7a_heatmap
>> stddeviation=.0001
>> Here's the command output:
>> STDDEV: 0.000100
>> RES: 200.000000 ROWS: 1000 COLS: 1000
>> Writing output raster map using smooth parameter=0.000100.
>> Normalising factor=0.000000.
>> Maximum value in output: 0.000000e+000.
>> If I change stddeviation to 100, here's what I get:
>> STDDEV: 100.000000
>> RES: 200.000000 ROWS: 1000 COLS: 1000
>> Writing output raster map using smooth parameter=100.000000.
>> Normalising factor=64826.350188.
>> Maximum value in output: 0.000000e+000.
>> Either way, the resulting raster is a large salmon/pink square. I have no
>> idea what I'm doing wrong. I've tried varying the stddeviation parameter
>> from 100 to .0001 and some values in between, and I don't get anything
>> different. Heck, I just now used 1000000 and .000001 and got nothing
>> different.
>> I was really hoping to make a high res heat map of these 2.5 million
>> points and overlay on to a street map layer.
>> Aren
>>
>> On Fri, Feb 11, 2011 at 9:45 PM, Aren Cambre <aren at arencambre.com> wrote:
>>>
>>> I am not clear how to get useful results out of v.kernel. I have a vector
>>> layer imported from PostGIS that has about 2.5 million points. I want to
>>> make a high density raster to show where these points are clustered. I can
>>> get the vector layer to display in GRASS just fine, albeit without
>>> attributes because of http://trac.osgeo.org/grass/ticket/1274.
>>> It's not clear to me, based
>>> on http://grass.fbk.eu/gdp/html_grass64/v.kernel.html, how you can get it to
>>> do something besides make a big, pinkish (salmon-red?) square?
>>> Aren
>
>
> _______________________________________________
> grass-user mailing list
> grass-user at lists.osgeo.org
> http://lists.osgeo.org/mailman/listinfo/grass-user
>
>