Friday, 9 November 2012

Short cuts

The latest version of OS Locator open data has been released. Musical Chairs and ITOWorld both published updated information. There are five new names in Hull and seventeen in East Yorkshire all to be visited, checked and then updated.

Of course there is a short cut. I could just use the names OS supply and update the roads in OSM without checking. That would be easy, I could do it from home without spending any time out in the cold and the city and county would quickly look complete again. I could get most of this from the OS StreetView, copying the road names from the tiles overlaid in the editors. Would that be a good idea?

I have checked some of the areas that have slowly had the number of anomalies whittled away and it seems that about 3½ to 4% of the roads named get a not:name tag to show that what is shown on the ground is not the name OS think it is. So if I just copied the OS names  without checking them I would be introducing about a 4% error into the names in OSM.

Looking at a few places where the names have suddenly had a huge reduction in the list of anomalies it seems that the checking may not have been done. Sheffield has a not:name ration of 0.5%, Penwith has a ratio of 0.9%. Taunton Dean has no not:names at all. It is possible that this ratio is right, but it seems unlikely. I hope that people do manage to sort this out over time, but a road with a name is not likely to have its name resurveyed, so I suspect most of these will persist.

I like the OS Locator data and I'm grateful to the people who process it and make it available to mappers. It is a great way to find out the roads that have been added or changed recently (thanks OS) but please use OS (or any other data) sceptically, it is not perfect, it needs checking. Short cuts are only useful if they preserve the quality.

1 comment:

~socks said...

Could you do a visualisation of %age not:name per district?