Thanks.<div><br></div><div>I did this:</div><div><b>v.random output=random_vector n=10000</b></div><div><br></div><div><b></b>Then I ran this:</div><div>v.kernel --verbose input=random_vector output=random_vector_heatmap stddeviation=1</div>
<div><br></div><div>That just made a large yellow square. So I changed <b>stddeviation</b> to 100 and got a yellow square speckled with teal and dark blue pixels after 7 seconds. Then I changed it to 1000, and after 232(!) seconds, I got something that actually resembles a heat map!</div>
<div><br></div><div>It appears the random_vector map is 100000x100000 units, so I can see why 1000 is necessary to get a reasonable map.</div><div><br></div><div>I then ran <b><a href="http://r.info">r.info</a> map=random_vector@de_maps</b> and got this (cut down to key data):</div>
<div><div><font class="Apple-style-span" face="'courier new', monospace"><b>Type of Map: vector (level: 2)</b></font></div></div><div><font class="Apple-style-span" face="'courier new', monospace"><b>Number of points: 10000</b></font></div>
<div><font class="Apple-style-span" face="'courier new', monospace"><b><div>Projection: Lambert Conformal Conic <span class="Apple-style-span" style="font-weight: normal; "><b><div style="display: inline !important; ">
N: 100000</div></b></span></div><div><span class="Apple-style-span" style="font-weight: normal; "><b><div style="display: inline !important; ">S: -99975.58519242</div></b></span></div><div><span class="Apple-style-span" style="font-weight: normal; "><b><div style="display: inline !important; ">
</div></b></span>E: 99987.79259621</div><div>W: -99975.58519242 </div></b></font></div><div><font class="Apple-style-span" face="'courier new', monospace"><b><br></b></font></div><div>That looks like it's around 200000x200000 units?</div>
<div><br></div><div>So I ran <b><a href="http://v.info">v.info</a> map=master_grass7@de_maps</b> on my original vector data and got this key data:</div><div><div><b><font class="Apple-style-span" face="'courier new', monospace">Type of Map: vector (level: 2)</font></b></div>
<div><b><font class="Apple-style-span" face="'courier new', monospace">Number of points: 2057980</font></b></div></div><div><div><b><font class="Apple-style-span" face="'courier new', monospace">Projection: Lambert Conformal Conic</font></b></div>
<div><b><font class="Apple-style-span" face="'courier new', monospace">N: 2781558.27080444</font></b></div><div><b><font class="Apple-style-span" face="'courier new', monospace">S: 422254.4557289</font></b></div>
<div><b><font class="Apple-style-span" face="'courier new', monospace">E: 12145354.2426632</font></b></div><div><b><font class="Apple-style-span" face="'courier new', monospace">W: 767479.81703687</font></b></div>
</div><div><br></div><div>I went back to the Map Display window for this vector and noticed that about all I am interested in is a box bounded by 1269430.31,1210876.00 on the NW side and 1325045.16,1164615.03 on the SE side. Does this mean I should define a region with this as the bounding box, then re-run v.kernel and hope it works on just that region?</div>
<div><br></div><div>Aren</div><div><br><div class="gmail_quote">On Tue, Feb 15, 2011 at 12:15 PM, Marcello Gorini <span dir="ltr"><<a href="mailto:gorini@gmail.com">gorini@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im"><br>
> Aren said:<br>
>Where is resolution adjusted?<br>
><a href="http://grass.fbk.eu/gdp/html_grass64/v.kernel.html" target="_blank">http://grass.fbk.eu/gdp/html_grass64/v.kernel.html</a> doesn't make that clear.<br>
<br>
</div>GRASS works with the region concept. You can adjust any region settings with<br>
the command g.region, like:<br>
<br>
g.region res=desired_resolution -p<br>
<br>
The -p is for you to see the resulting changes.<br>
<div class="im"><br>
>Am I supposed to have a pre-made raster layer already that corresponds to<br>
my<br>
>vector layer?<br>
<br>
</div>No, you probably don't. I would suggest you play around with v.random to<br>
create some random points and then use v.kernel to make the heat map. Do<br>
that with different number points, stdev and resolutions to get the feel of<br>
it.<br>
<br>
Maybe in this way you will understand what is going on with your specific<br>
case.<br>
<div class="im"><br>
>I really appreciate your advice!<br>
<br>
</div>Any time! Sorry not to help you more.<br>
<div class="im"><br>
>I'm not upset with the list, was just afraid this was too esoteric or<br>
poorly stated.<br>
<br>
</div>I think I myself have been a little upset a few times when I did not get any<br>
responses to my querries :) that's why I mentioned, I guess. But I from<br>
Brazil, so either I get upset or I get really happy :)<br>
<br>
Cheers,<br>
Marcello.<br>
<font color="#888888"><br>
--<br>
View this message in context: <a href="http://osgeo-org.1803224.n2.nabble.com/v-kernel-how-to-get-useful-results-tp6018010p6028684.html" target="_blank">http://osgeo-org.1803224.n2.nabble.com/v-kernel-how-to-get-useful-results-tp6018010p6028684.html</a><br>
</font><div><div></div><div class="h5">Sent from the Grass - Users mailing list archive at Nabble.com.<br>
_______________________________________________<br>
grass-user mailing list<br>
<a href="mailto:grass-user@lists.osgeo.org">grass-user@lists.osgeo.org</a><br>
<a href="http://lists.osgeo.org/mailman/listinfo/grass-user" target="_blank">http://lists.osgeo.org/mailman/listinfo/grass-user</a><br>
</div></div></blockquote></div><br></div>