Tuesday 13 November 2012

OS Opendata in OSM

Prompted by a comment from Socks, I have looked at some of the GB regions where Ordnance Survey road names don't match the names in OSM. The OS Opendata names on roads are provided by OS StreetView and a textual version is provided by OS Locator. ITO World and Musical Chairs both use OS Locator to create a graphical tool to help people identify where the OS & OSM names for roads differ.

Sometimes the name OS has for a road does not match the name displayed on a name board for the road. OSM uses the name from the name board. To help with the processing of anomalies the wrong, OS name can be added as a not:name tag. The occurrence of the not:name tag is a useful indicator to the origin of the names in OSM. If the names closely match the OS list then the OS names may have been used and the actual names may not have been surveyed. In this way the errors in the OS datasets find their way in to OSM.

One possibility is that mappers in an area may not use the not:name tag. They may not like it or maybe they don't know about it. If they survey their road names and don't use the erroneous OS names then these anomalies should show up in any comparison.

I looked at some of the data about OS Locator and threw some data into a list for the most complete 250 authorities. ( I lost the will to live after 250.) You can see the list at osloclist.raggedred.net. If you click the headings it will sort that column, allowing you to see where how each authority compare.


Anonymous said...

Is it worth looking for source:name=OS_OpenData_Locator for a direct idea of the source of the name? Might make a good layer, like noname.

Chris Hill said...

It can be useful, but sadly some people don't use source tags. Others add the source tags to the changeset which makes finding it completely impractical by hand.

A layer to show this might help with future corrective surveys,.

Tom Chance said...

This is very interesting, thanks Chris.

At the other end, it's interesting that we have such high numbers of not:name values in Gwynedd, Anglesey and Conwy. Surely the OS data can't be wrong 13-17% of the time?

From my own mapping around the Lleyn peninsula, particularly in Criccieth, I wonder if it's skewed because of the English and Welsh road names. I have always tagged the main name as name= and put the English or Welsh alternative in as name:en= or name:cy=, sometimes adding the alternative name from OS Locator where I couldn't see it on the ground. OS Locator on the other hand seems to be slightly random in its choice of language, not corresponding to the road signs.

Chris Hill said...

I suspect some OS muddle over Welsh and English. The few that I looked at were often poor spelling of the Welsh..

Gregory Williams said...

ITO have a good visualisation of where not:name has been used. It certainly shows that it hasn't been used evenly across the country: