Usability of Geographical Information – the case of Code-Point Open
1 July, 2010
One of the surprises of the Ordnance Survey OpenData release at the beginning of April was the inclusion of the Code-Point Open dataset, which lists the location of all postcodes in England, Wales and Scotland. This was clearly a very important dataset because of the way postcode geography drives many services and activities in the UK. Before the release, the costs of using postcodes in geographical analysis were prohibitive for many small organisations.
So how usable is this free Code-Point data? The principle of ‘do not look a gift horse in the mouth’ doesn’t apply here. The whole point of releasing the data is to make it as useful as possible to encourage innovation, so it should be made available in a way that makes it easy to reuse. I evaluated it while analysing a dataset of 11,000 volunteers’ postcodes that I received from a third sector organisation.
The download process is excellent and easy, apart from the fact that there is no clear and short description of the products in a non-technical manner next to each product. To find a description, you need to go to the product page – so you are at least 2 clicks away from the product details. It would be better to have a link from each product and include a brief description in the download page. We will see in a second why this is important…
The next step was the download itself and the opening of the zip file, which was clear and easy. There is an oddity with all Ordnance Survey data that they have a redundant sub-directory in them – so in this case the data resides under \codepo_gb\Code-Point Open\ . The fact that the files is broken up into postcode area instead of one big file of 157MB is fine, but it can be helpful to remind users that they can concatenate files using simple commands – this is especially necessary to less tech-savvy users. So an explanation for Windows users that you can open the Command window using ‘cmd.exe’ and run ‘type a.csv b.csv > common.csv’ can save some people plenty of time.
But the real unpleasant surprise was that nowhere in the downloaded package is there a description of the fields in the files! So you open the files and need to figure out what the fields are. The user manual is hides 4 clicks away from the download page and luckily I knew that the ‘user manual’ is stored under ‘technical information’ on the product page, which is not that obvious at first visit. Why not deliver the user manual with the product ?!? The Doc directory is an obvious place to store it.
The user manual reveals that there are 19 fields in the file, of which 9 (half!) are ‘not available in Code-Point Open’ – so why are they delivered? After figuring out the fields, I created a single line that can be attached to the files before importing them to a GIS:
Postcode,Positional Quality,PR Delete,TP Delete,DQ Delete,RP Delete,BP Delete,PD Delete,MP Delete,UM Delete,Easting,Northing,Country,Regional Health Authority,Health Authority,County,District,Ward,LS Delete.
Of course, all the fields with ‘Delete’ in the name mean that they should be deleted once imported.
Interestingly, once you delete these fields, the total size of Code-Point Open drops from 157MB to 91MB – which means that it can save the Ordnance Survey bandwidth and carbon emissions by making the file smaller.
Another interesting point is that the user manual includes detailed instructions on how to change the postcode to a ‘single spaced postcode’. The instructions are for Excel, Mapinfo and ArcGIS. This is the type of information that can help end-users start using the data faster. Finally, you can use this wonderful information to create lovely maps.
All these problems are minor, apart from the description of the fields which is a major usability error. Similar analysis can be carried out for any of the Ordnance Survey datasets, to ensure that they are useful to their users. There are some easy improvements, such as including the user manual with the distribution, and I’m sure that, over time, the team at the Ordnance Survey will find the time to sort these issues.