[QGIS-ZA-user] aggregate crime attribute data from SAPS Station boundaries to Wards

[Brian O'Leary]

Dear QGis SA,

I would like to know if there is a QGis tool that can assist with the
following task.  I want to transfer crime attribute data from SAPS Station
boundaries to Ward boundaries, assuming that crime is evenly distributed
within the SAPS Station boundary.

Previously I have done this task in Arc View using a script called
DataPart.avx which was written by Jianwei Dou in 2002.  The below
simplified sketch illustrates what I am trying to do in Qgis.  The SAPS
Station shape has the data attributes and the Ward shape is the overlay or
boundary shape. The output that I need is an attribute table that has
calculated the % intersection of the SAPS Station by the ward boundaries
and aggregated the crime attributes to a Ward table based on the %
intersection.  In the below sketch the ward boundaries intersect the SAPS
Station boundary by 50% in both cases.  As there were 100 crimes in the
SAPS Station boundary the output table lists Wards 1 and 2 with 50 crimes
in each.

[image: image.png]
Any advise most welcome.

Regards
Brian O'Leary
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