Hi John,
We develop an open source tool called CartoDB that can do some really nice choropleth maps. You can check-out the code over here, https://github.com/Vizzuality/cartodb Depending on what you run it on, it can handle some pretty large datasets, here is a choropleth map of thousands of polygons representing human population, https://viz2.cartodb.com/tables/pop_density_polys/embed_map?q=select%20the_geom_webmercator%20from%20pop_density_polys Shoot us an email if you have any questions. Cheers, Andrew On Mon, Apr 2, 2012 at 12:48 PM, John Abraham <[email protected]> wrote: > I've been looking for an open-source and easily deployable solution to > allow users to view choropleth maps of PostGIS layers. The layers are > straightforward enough, just a geometry column, a GID, and then a bunch of > value columns. I simply want the user to be able to use his own computer > resources to select the value columns, select the ranges of the classes for > the colors, and perhaps select the color ramp. I already have a Django > project which allows the user to generate the layers (select the > appropriate geometry and value columns and crosstab them into a single > PostGIS view.) > > We have a partially implemented system using Mapserver and Openlayers, but > the maps are delivered as bitmaps by the server, which means sending full > bitmaps every time the user changes the ranges or selects a different value > column. Here are the technologies I think I can use to do it in the > browser alongside my existing Django code: > > 1) Javascript, probably GeoEXT http://geoext.org/ using open layers, so > the browser draws the map, it seems this should be dead-easy and there > should be a cut-n-paste example out there but I've been struggling a bit > trying to find one, > > 2) Java applet, there must be one out there I can customize but I haven't > found one yet (admittedly haven't looked too hard yet for a Java applet, > because I've been preferring the idea of Javascript) > > 3) Adobe flash/flex, I have no experience with this and the development > environment is not open-source, but it looks pretty flexible. I can > probably grab code from a colleague of mine who does have something similar > already working, but when I looked his code it looked pretty complex > internally and it used a few non-open-source libraries. > > Any suggestions or thoughts? I have a feeling that there is A Very Easy > Solution out there that I'm not finding. > > Alternatively, I could use > > 4) a QGIS plugin, abandoning the web interface all together, moving my > existing python code for generating the layer out of Django and into QGIS, > then using QGIs to view the layer. This would require me to deliver and > support QGIS. > > -- > John Abraham > _______________________________________________ > postgis-users mailing list > [email protected] > http://postgis.refractions.net/mailman/listinfo/postgis-users > -- Andrew W. Hill www.vizzuality.com
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