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

[Aren Cambre]

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

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
>>
>
>
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