How to microblog in high heels

A geek girl's guide to social media and online engagement

Grappling with Google maps: Creating a ward map of Cardiff

Recently over on the Guardian Cardiff blog I’ve been experimenting with using Google maps to display certain bits of local government data, as well as creating collaborative maps with readers for local events.

Often council reports are stocked full of data broken down by ward which should be easily mappable – and which would allow readers to quickly digest the data in an accessible way.

When such reports are issued the council rarely includes a map to display the data – and if it does, it’s a pdf file which can take hours to translate into a Google map.

One problem which constantly presents itself is the lack of local government ward maps which would provide a template to map certain bits of data onto.

The fantastic team at Openly Local helpfully mapped some local government ward data on Google maps and explained how here – but unfortunately Cardiff didn’t seem to be covered in this.  Reason is – ward data wasn’t really available until April this year, according to this post by Michael Grimes – so no wonder it’s not really accessible.

Mapping recycling rates for Cardiff

Recently the council released the recycling rates for each ward in Cardiff – a fantastic data set which allows readers to find out the average amount of recycling their local district achieves – and how far off government targets they are. But the data was given to me as a list, and as a bar chart – with only one paper copy and one pdf graph.

In a quest to plot this data on a Google map, I soon found city regions at ward level are not produced by the council – they do have a pretty user-unfriendly mapping portal which looks like it uses ONS data. Instead, I turned to My Society programmer Matt Somerville (@dracos) – who showed me some boundary data which is under the OS OpenData licence,  and available from Mapit here. Once you have the KML files for each ward – you can import them to Google maps and get something which shows each ward for Cardiff.

This will undoubtedly prove useful as I can use it as a template to produce a number of maps over time – but it wasn’t obvious how Google would let me keep one original map – and duplicate it for modification. What took time was adding each percentage to each ward separately and changing the gradient of the fill colour to match the percentage. Google maps worked quite slowly with so many files – and there was no spreadsheet with the data in it for me to upload.

After this I exported the KML code for the map (click view in Google Earth) and uploaded it to Zeemaps which allowed me to see all the wards on one map – see the result here.

Thus, we have a ward map showing local government data broken down to the minutest boundary level. It’s not quite there yet – using the same colour perhaps not as visually effective as Open Heat Map – but it’s a start.

I would be interested to know how other have got on with plotting government data by ward level. Leave your comments below.

Contains Ordnance Survey data Š Crown copyright and database right 2010.

Written by hrwaldram

December 7, 2010 at 1:14 pm

4 Responses

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  1. Good stuff! And yes, it’s true: UK boundary information was not available for public use until 1 April 2010:


    December 7, 2010 at 3:39 pm

  2. […] Grappling with Google maps: Creating a ward map of Cardiff « How to microblog in high heels Hannah Waldram on grappling with Google maps and local government data. (tags: data journalism map mapping teaching) […]

  3. Good work Hannah. Pesky ward boundaries. I did my ward map by copying, by hand, the ward boundaries on the Cardiff council ‘virtual maps’ site. It’s not perfect but works:,-3.211098&spn=0.140386,0.308647&z=12

    I can just copy that one now and use it as an overlay for different data sets, such as this one on nasty stomach bug cases:,-3.206291&spn=0.140402,0.308647&z=12

    Although, once OpenHeatMaps recognises Cardiff ward boundaries we’ll be laughing!

    Btw – how come your site only takes comments from registered users?

    Ed Walker

    December 8, 2010 at 10:30 pm

  4. Think we’ll be waiting a long time for Open heat map to go to ward boundary level – which is why I wrote this post. You’d think most of a mapping tools would have access to boundary information but there has been very little developed from ward boundary data aside from what MySoc and Openly Local have done.
    Copying by hand is always going to be inaccurate and time consuming – do importing the exact coordinates of each boundary this way is far easier and a much more secure way of doing it. Feel free to use our boundary map for your maps in the future, with a credit ;).
    As for the commenting – to be honest I didn’t used to get many comments on this blog so I hadn’t event realised it was restricted to users – while they are a friendly bunch – I suppose I’ll be openly comments up to the masses soon! Thanks for your comment Ed.


    December 9, 2010 at 9:15 am

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