OpenStreetMap completeness is something that gets spoken about a lot at OA; we already use OSM data in places, but there are some who feel uneasy about the data when it is provided without any indication of its completeness or quality. I think sometimes these questions can be a little unkind; they're rarely asked of Google, for example, and it often falls upon the OpenStreetMap crowd to highlight inaccuracies in this ubiquitous mapping resource. Early last year I noticed some myself.
Despite my moanings, completeness studies are, however, very important. One of the beauties of OpenStreetMap is that you can download all the data yourself, making these studies uniquely possible; the only country you could do similar analysis for based on Google Maps data is Kenya. Luckily, people are looking at completeness of the map, Muki Haklay, for example, has released comparisons of OSM data showing completeness in March 2008 and October 2009.
Bored yesterday, and stuck inside with a cold, I decided to see if I could come up with my own completeness metric. Muki Haklay's example was concerned with roads, I wanted to try something based on PoIs.
The Guardian provides via their excellent DataBlog the number of pubs in the UK: 53,466. From CloudMade we are able to download a gpx file containing a mention of every restaurant, pub & takeaway within the UK recorded on OpenStreetMap. We can very easily pull out the number of pubs and come up with the percentage figure demonstrating the completeness of pub recording in the UK:
joseph@joseph-work:~$ grep -ci '
(20 620 / 53 466) * 100 = 38.5665657
Let's round that up and say that 38.57% of the pubs in the UK are recorded on OpenStreetMap.
Whilst we can't be sure of the quality of the data provided by the Guardian, we can look a little closer at the OSM data. Some of it, for example, is pretty bad, other pubs have had the word "closed" added to their names, not something you probably need on a map:
joseph@joseph-work:~$ grep -i '
Regardless, these numbers are small so the 38.5% figure still likely rings true enough. Some might argue that it's a small number, but the level of contributors to OpenStreetMap continues to rise in a very positive rate, as such I'm sure that if this was re-run towards the end of 2010 we'd see a big improvement.
If you're reading this and don't know if your local is on OpenStreetMap, why not take a look; once you've got an account you only need to click the edit button to add it.