[postgis-users] Easiest web-gis for choropleth map or should I use QGIS plugin?

[Andrew Hill]

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 <jea at hbaspecto.com> 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
> postgis-users at postgis.refractions.net
> http://postgis.refractions.net/mailman/listinfo/postgis-users
>



-- 

Andrew W. Hill
www.vizzuality.com
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