Turning points into polygons (or voronois) is the "thinking like a GIS professional" approach. This is valid, but not as good as it can get. Basically, using imaging techniques would be a better approach.
Perhaps you can take this: http://www.sethoscope.net/heatmap/ as a starting point? The author has created a nice python script to generate a heatmap. 2011/2/23 Josh Jordan <[email protected]> > First, you have to turn your points into shapes, theres some algorithm that > will turn points into polygons with borders midway between each point. > Then, you have to add classes to the mapfile. Add one class per color. > You have to calculate the bounds and color for each class like this: > > CLASS > EXPRESSION(([POPULATION] gt 90457) AND ([POPULATION] le 108397)) > STYLE > COLOR 10 20 50 > END > END > > If your CSV data isnt joined to the mapserver data, you have to calculate > what shapes are in each bucket like this- > > CLASS > EXPRESSION(([NAME] = "Shape1") OR ([NAME] = "Shape2")) > STYLE > COLOR 10 20 50 > END > END > > --- On *Tue, 2/22/11, Daniel Cole <[email protected]>* wrote: > > > From: Daniel Cole <[email protected]> > Subject: [mapserver-users] Heatmap / choropleth from points attributes > To: [email protected] > Date: Tuesday, February 22, 2011, 10:06 PM > > I am a new mapserver user and have spent countless hours over the last > month reading, trying code, etc. before posting here for help. I am trying > to generate an image (non-interactive) on a webpage based off of attribute > data in a points file. For example, 20 different points equally distributed > in a field contain data about the moister level of the soil. I want to make > the lowest levels blue and the highest levels yellow, or something like that > with some gradients in between. If possible I want it to have interpolated > data between them to show the gradual change, but that isn't a must. I > also want to wrap it in a polygon that trims the edges. > > I found some python code that I thought might do the trick , but it seems > lots of heat maps are based off of how many points exist in a certain area, > and thats now what I am doing. > > My points contain numbers in the attributes, 5, 25, 92, 71, etc. I feel > like I am missing some easy way to do this right in front of me with gdal or > something. If someone has any direction or even demo code that would be > greatly appreciated. > > Thanks, > > Daniel > > -----Inline Attachment Follows----- > > _______________________________________________ > mapserver-users mailing list > [email protected]<http://mc/[email protected]> > http://lists.osgeo.org/mailman/listinfo/mapserver-users > > > > _______________________________________________ > mapserver-users mailing list > [email protected] > http://lists.osgeo.org/mailman/listinfo/mapserver-users > >
_______________________________________________ mapserver-users mailing list [email protected] http://lists.osgeo.org/mailman/listinfo/mapserver-users
