[OSGeo Africa] Comparing census and elections datasets

Charles Rethman rethman at me.com
Wed Apr 9 01:14:02 PDT 2014

Dear Adi and everybody,

I've been thinking about this. I think whatever happens you'll need to do some cookie-cutting.

The best solution I think would be to make your algorithm in PostGIS and map it on QGIS.

If you like, we could meet up and discuss the details further--and post our trials or results back to this forum? Where--Codebridge? contact me on rethman at me.com.

Charles Rethman
Wahenga Ltd.
Director, Cape Town Office

Cell: +27 71 6735502
Tel: +27 21 6861510
Skype: cwrethman
PO Box 23507, Claremont, 7735, South Africa
19 Sans Souci Road, Newlands, 7700, Cape Town

On 8 Apr 2014, at 7:12 AM, Adi Eyal <adi at code4sa.org> wrote:

> 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
> this.
> 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?
> Thanks
> Adi
> -- 
> Adi Eyal
> Director
> Code for South Africa
> Promoting informed decision-making
> phone: +27 78 014 2469
> skype: adieyalcas
> linkedin: http://za.linkedin.com/pub/dir/Adi/Eyal
> web: http://www.code4sa.org
> twitter: @soapsudtycoon
> For more information on how to participate in the open data community
> in South Africa, go to: http://www.code4sa.org/#community
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