Many of the requests that I’ve had since launching the Voter Power Index site have been for a map to visualise the power of the constituencies side-by-side. This was something I wanted to do from the start, but it has proved not to be a simple task. This site is built on open source code libraries and APIs, from the underlying PHP framework, CakePHP, to the visualisation tools from Google Chart API. While, there are mapping tools available from Google and Ordnance Survey, there is nothing that enabled me to easily produce a constituency heat map, or choropleth map.
One project that has been instrumental in enabling me to build a map for the site was the Choropleth UK project at Rewired State. In this project the developers have used an SVG image to extract data to build an HTML image map. This is designed to be a more accessible way of displaying data, as many media organisations use Flash based maps to present constituencies, which aren’t viewable by many devices.
Before I get lots of emails saying my map isn’t good, I’ll be up front and say that my implementation of the Choropleth project is still a bit sketchy. The project only had data for the old constituency boundaries and my import of the new boundaries hasn’t produced a very robust clickable image map, particularly on the Scottish coastline. The map currently doesn’t work well on Internet Explorer and in contradiction to what I say above about this method being more viewable on devices, it doesn’t work too well on the mobile version of this site.
So, bearing in mind its limitations, I invite you to take a look at version one of the Voter Power Index heat map.
