[OSGeo Africa] Comparing census and elections datasets

Adi Eyal adi at code4sa.org
Mon Apr 7 22:12:24 PDT 2014

Hi All

I would like map demographic data from the 2011 census on top of
elections results from 2009. There seem to be two problems with doing

1. Old wards have disappeared and new ones have been created by MDB.
2. In some cases the same ward id has been re-used for completely
different polygons.

In short, the obvious approach of joining two datasets won't work. It
is possible (but difficult) to calculate approximations by overlapping
shapes from the two maps and using some sort of algorithm (possibly
assuming uniform distribution of data points) to slice up one shape
and fit it into another.

I don't want to go down that route.

Is there another to go about this?


Adi Eyal
Code for South Africa
Promoting informed decision-making

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