OpenStreetMap
Enlivened a long drive up to the Scottish Highlands along the M6 and M74 whilst my co-driver was at the wheel by surveying all the bridges we went under (power lines too). Surprising how many existing roads don't have a bridge marked - mainly the ones at the junctions are marked as bridges. I also found that in some places there was a misalignment between the motorway carriageways and the public GPS tracks.
So all you OSMers - time to re-survey British motorways? It'll sure alleviate the boredom!
Discussion
Comment from daveemtb on 15 May 2009 at 13:54
There are lots of farm tracks and things with bridges over motorways which I'm sure haven't been mapped.
About misalignment - are you confident that it is the many other GPS tracks that are misaligned rather than yours, or have you checked aerial photos? If there's been a change in road layout recently, then you could be right, but I'd hesitate to move a motorway just because your track doesn't line up with 100 other tracks. GPS traces can occasionally be a long way out.
Comment from c2r on 15 May 2009 at 14:05
Further to that comment, load up the area in potlatch and press G to see all the GPS traces from everyone - there's usually tonnes for motorways and it can be easy then to work out an average....
Ta
Chris
Comment from brianboru on 15 May 2009 at 16:18
I was re-aligning the motorway with the tons of public GPS tracks, which included my own, which showed a consistent "average" track about 20-30m away from the rendered way. So I hope I've improved things rather than made them worse!
Comment from RichardB on 15 May 2009 at 21:28
If you are mapping the very northern part of the M6 - between Carlisle and Gretna - remember that this is a new piece of motorway which has been re-aligned in many places (replacing the old A74)