Visualizing Point Data

[Dylan Beaudette]

On Sunday 05 February 2006 09:16 am, Bill Binko wrote:
> On Fri, 2006-02-03 at 11:40 -0800, Dylan Beaudette wrote:
> > I was just working on this last night:
> > http://casoilresource.lawr.ucdavis.edu/drupal/node/172
> >
> > check out the source for v.kernel in GRASS
>
> Dylan,
> This is an excellent example of what I'm trying to achieve.  Here are
> some quick thoughts about what you've shown:
>
> 1) How would you publish this "live" to the web?  Do you know how to
> integrate v.kernel to push its output to mapserver directly?  I know
> there are tools to push GRASS output through GDAL, and I suspect that
> that could be daisy chained into mapserver, but I'd like someone's
> opinion who's actually done this.  If there's an example (anybody?) or
> HOWTO of how to leverage GRASS this way?
>

Hi Bill,

Here is a quick link to the GRASS site, on how to get a GRASS-Mapserver 
application running:

http://grass.itc.it/start.html

towards the bottom of the page, there is a link to a project from some time 
ago which called GRASS directly using PHP: essentially setting up the GRASS 
environmental variables, and then running the appropriate commands via 
system(). 

> 2) What is the performance of v.kernel.  For example, I'll have 30-100K
> points over the state of florida.  For a zoomed out view, how long would
> that take to draw?  Perhaps a better question would be, what is the
> order of complexity of the approach taken by GRASS.

Well- it is resolution dependant. The map made with v.kernel is of an area 
close to 27k acres, and at a resolution of 10m it took about 5 minutes. 
However, at a resolution of 100m it only a took a couple seconds. 

> 3) Unfortunately, because I may want to integrate this into Mapserver, I
> can't quite look at the GRASS source on this.  More specifically, I
> can't copy it since it's GPL into Mapserver, which is BSD and then
> distribute it. Now: I may choose to simply write code to call GRASS
> externally, but I wouldn't need to explore the source for that.

See the PHP example for calling an install of a GRASS directly.

> I will however, get GRASS 6 up and running here so that I can explore
> it.  Thanks for the pointer.

You bet. Let me know how it turns out.

Cheers,

-- 
Dylan Beaudette
Soils and Biogeochemistry Graduate Group
University of California at Davis
530.754.7341