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Bill,<br>
<br>
The census site I sent you is actually doing this type of overlay right
now. It's all MapServer/Mapscript based. Let me know if you have any
questions.<br>
<br>
The overlays are drawn on the fly from the Census BlockGroup data.
It's got quite a bit of indexing behind the scenes that makes it run
fairly quickly. It seems to run out of steam at around 50k points
when the time seems to take a jump up to 10-15 seconds to process ( the
limit we were shooting for). Unfortunately, the code is very Census
specific at the moment. We're planning on chopping the code out into
a tool set, just haven't had time yet.<br>
<br>
One other item, the overlays are being drawn right now in a fairly
course grid, the overlay drawing aspects are configurable and the
resolution can be increased at the cost of time for processing.<br>
<br>
bobb<br>
<br>
<br>
Bill Binko wrote:
<blockquote cite="mid1139159770.22956.11.camel@fastcat.binko.net"
type="cite">
<pre wrap="">On Fri, 2006-02-03 at 11:40 -0800, Dylan Beaudette wrote:
</pre>
<blockquote type="cite">
<pre wrap="">I was just working on this last night:
<a class="moz-txt-link-freetext" href="http://casoilresource.lawr.ucdavis.edu/drupal/node/172">http://casoilresource.lawr.ucdavis.edu/drupal/node/172</a>
check out the source for v.kernel in GRASS
</pre>
</blockquote>
<pre wrap=""><!---->
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?
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.
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.
I will however, get GRASS 6 up and running here so that I can explore
it. Thanks for the pointer.
Bill
Bill Binko <a class="moz-txt-link-rfc2396E" href="mailto:bill@binko.net"><bill@binko.net></a>
</pre>
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