How complete is Open Street Map?

OSM is a great project and as it gains in coverage it becomes an increasingly attractive proposition. One of my former clients in Local Government was excitedly talking about the potential to use OSM for some of their partnership projects, which prompted me to look at OSM in a little more detail.

Take a look at these two similar scale images of Highgate, North London from OSM and Google.



The OSM version has some footpaths and also includes the railway line which Google does not show, plus in my opinion the cartography in OSM is the nicest I have seen of any web maps (I know that is not their raison d’etre but it is still nice). Unfortunately when you look a bit more carefully you will see that there are some small streets missing and some of the road name attribution is different to the TeleAtlas data in Google. I have highlighted a few differences below but have not searched for all.

In Google

and in OSM
Now OSM is a community project and I don’t think they make any claims about completeness or accuracy of attribution. However those of us in the GeoCommunity who consider using OSM in a project or who promote the development of crowd sourced data need to be aware of its potential limitations. Unfortunately at the moment there is no way that I can see to guage the level of completeness of OSM which seems to make it a bit of a lottery.

At AGI GeoCommunity08 there are a couple of potentially very interesting sessions on on this topic from Andy Coote and Nick Black