UK Mapping with Tableau V6.1–What’s changed?

Tableau have improved the ‘out of the box’ mapping functionality in their latest release (V6.1) which is expected to be available sometime in July 2011.

This post will explain what exactly has been done and the implications for users of Tableau’s mapping functionality in the UK.

So what have Tableau changed?

Before V6.1, Tableau does not include the ability to map data in the UK out of the box – it had to be done by adding a ‘Custom Geocoding’ file.  This is a simple task which can be completed in 5 minutes, as described in my previous post, but proved to be a hurdle for some – and a frequently asked question for almost everyone.

With their latest release, Tableau have introduced a new ‘Geographic Role’ – those with eagle eyes will notice that the ‘ZIP Code’ role has been renamed to ‘ZIP Code/Postcode’.  According to the documentation provided during the beta programme, this geographic role provides out of the box mapping for postcodes in the following countries:

Australia, Canada, France, Germany, New Zealand, and the United Kingdom

Problem solved, right?

Well not quite.  The post code in the UK is a complicated beast.  There are 1.8 million postcodes in the UK, and this was always going to present a problem for Tableau, as understandably they would not want to bloat the (currently) 50MB download with this data. 

Thus Tableau have included only the OUTCODE level of the UK postcode (the outcode is the left hand side of the postcode, up to the space, and is either 2,3 or 4 characters in length).

If the data you are trying to present can be appropriately represented at the outcode level – i.e. you do not need to show more detail on your map - then you do not have much work to do, but it is likely you will have to follow the instructions below to make this work.

Making use of the ‘out of the box’ outcode mapping

So Tableau added the OUTCODE data to V6.1. 

BUT - there is a very good chance your data includes the FULL POSTCODE, not the OUTCODE – so you still have a little work to do to make this work.

You will need to create a calculated field to extract the outcode from the postcode field.  You can use this calculation below, replacing the word postcode with the appropriate fieldname from your dataset.

LEFT([Postcode],  FIND( [Postcode], ' ')-1 )

This calculation will look for the space in your postcode and then grab the characters before the space into a new field.

You will then need to set the GEOGRAPHIC ROLE of the new field to ‘ZIP Code/Postcode’:

Once this is done, a simple double click on your outcode field should cause Tableau to draw your map.

What if you want more detailed mapping than outcode provides?

Clearly there are times when you will want to map data at a lower level of resolution than OUTCODE provides.  Outcode is appropriate when you are looking at the UK as a whole, but is too highly aggregated to look at the detail in a specific region of the UK.

Mapping using different levels of the UK postcode still requires implementing custom geocoding.  This process is dealt with in some detail in a previous post.

The post linked above provides access to the necessary csv files to implement mapping at ALL the levels of the UK postcode, outcode (no longer required of course), outcode plus one, plus two and the full postcode.  I have also included a link to the SQL Database (and a TDE file) of postcodes in order that you can created your own csv files by filtering the UK postcodes to the areas that interest you.

Once you are done, you should be able to create mapping at various degrees of resolution:

Download the packaged workbook example above from here

Good luck, please contact us for more information.