Saturday, 8 May 2010

UK electoral boundary changes

New UK Ordnance Survey OpenData Bounday Lines released this month, show changes compared with the original public release in April of October 2009 data. Both Electoral Division and Westminster Consituency boundaries are what you see in the BBC News or many other UK election maps on TV or online. Following yesterday's parliamentary and county council election results, one might ask:

  • were these simple data updates, or were boundaries changed prior to elections
  • in the latter, seeing how close election results were, was there gerrymandering?
Media maps very effectively portrayed the vote swings leading to a hung parliament. GIS can further be used to dig a little deeper into these boundary changes. I used GIScloud and OpenData to show these differences in two ways illustrated below:
  • regional map overlays polygons for 2009 (red outline and pink fill) and 2010 (green outline)
  • polygon centroids for 2009 (large blue) and 2010 (smaller cyan) highlight the changed areas
Got to the full maps to step through the themes (heat map variations of the centroids are another illustration).

Constituency area map, live quickview (full giscloud map)
- zoomed in to East Anglia to show detail

Consituency heat map, live quickview (full giscloud map)