A few months ago I compared the length of roads on the OSM database against the figures quoted by the Department for transport, and posted the results here.
I've now updated the figures using the OSM database extract at the end of 2009. The resulting map is here - http://www.reedhome.org.uk/Documents/OSMCoverJan2010.png and the data from my analysis is here - http://www.reedhome.org.uk/Documents/OSMCoverageJan2010.csv . The DfT data can be found here - http://www.dft.gov.uk/pgr/statistics/datatablespublications/roadstraffic/roa dlengths/ In summary, the length of roads on OSM that I am able to compare with DfT data has increased by around 5% if the last few months. The south east of England is still generally better covered than the north, but there is improved coverage all over the place. The biggest increase in coverage is in Cornwall, which has moved from less than 50% coverage to more than 80%. There are also significant improvements in Plymouth, and a number of cities in northern England and the West Midlands. The length of roads plotted for all of the following authorities has increased by more than 20%: . Cornwall . Plymouth . Bury . Wirral . Telford & Wrekin . Bolton . Rochdale . Oldham . Barnsley . Stoke-on-Trent Apart from minor tweaking to the way I categorise roads, I have removed anthing tagged "Motorway link" from the motorway totals, because I've discovered from the Department for Transport that they currently don't count links towards the length of motorways. This doesn't make a huge difference to the overall totals of course. For anyone wanting to recreate this, I should point out that I'm still using the admin boundaries as they stood four months ago. The reason for this is that I had to do a fair amount of tidying up last time to remove overlaps and inconsistencies in the boundaries. There have been some changes to the data for admin boundaries on OSM over the last few months, and I really ought to do the same tidying again, but it takes forever, and I don't have time at the moment. That means that I've not picked up some new boundaries in Wales that have been added since I did the last extract. In England I don't think this can be making a great deal of difference, except possibly at the margins of some local authorities. Where I can't get local authority boundaries from OSM yet, I've continued to use the EU regions instead. This mostly affects Scotland, where I can't find any local authority boundaries on OSM. I don't have the EU regional boundaries at the same level of precision as OSM admin boundaries so these figures will be a but fuzzy round the edges. As before, thoughts and comments are invited, and welcome.
_______________________________________________ Talk-GB mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-gb
