Not quite the same, but Carson Farmer's fTools plugins for QGIS include the functionality to create random points (by count or density) inside of a polygon.
http://www.ftools.ca/plugins.html Nothing specific about this functionality on this page, you need to look at the actual plugins in QGIS. David. On Thu, May 6, 2010 at 4:10 AM, strk <[email protected]> wrote: > ST_RandomPoinsOnSurface(geometry, numpoints) would be an interesting > function indeed. Sounds like a good job for GEOS/JTS. > > --strk; > > On Mon, May 03, 2010 at 10:49:32PM -0600, John Abraham wrote: >> One of the things I miss about using ESRI's GIS is the ability to do >> dot-density maps. Within a polygon, the number of dots is proportional to a >> value, and the dots are randomly placed. I find it useful to be able to >> present several data values at once (e.g. blue dots for population, red dots >> for employment). >> >> I also find that it is a more intuitive way of scaling for zone size than >> dividing the value by the area of the zone. That is, the count of the dots >> represents the actual number, but the density of the dots represents the >> density of the number. So I don't have to decide whether to divide the >> value by the area of the polygon to plot density: both the absolute number >> and the density are easily visible. >> >> Since my open-source GIS viewing systems (mostly QGIS and Mapserver) won't >> plot dot-density, I've done without. >> >> But today I realized that I can build these on the server instead. I can >> generate random points within the bounding-box of the polygon, throwing out >> those that aren't contained within the polygon, repeating until I have >> enough. Then I can save these points as a separate layer, and display this >> layer using almost any desktop or web based viewer! >> >> Has anyone done this? Can I do it in SQL or do I need to write something in >> PL/pgsql? >> >> -- >> John Abraham >> >> PS I just bought the Postgis In Action book; enjoying it so far. >> _______________________________________________ >> postgis-users mailing list >> [email protected] >> http://postgis.refractions.net/mailman/listinfo/postgis-users > > -- > > () Free GIS & Flash consultant/developer > /\ http://strk.keybit.net/services.html > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > _______________________________________________ postgis-users mailing list [email protected] http://postgis.refractions.net/mailman/listinfo/postgis-users
