I've actually been playing around with some automated-analysis stuff recently. In general you need a fairly large amount of traces covering a particular area to get anything meaningful out, but it's still interesting.
I think that not uploading your gps tracks is time, and there are perfectly valid reasons for not doing so. That said, having many gps tracks uploaded is actually useful. On 18/06/2009, at 3:25 PM, Ross Scanlon wrote: > If your connected to the internet that's fine but it's no use for on > the > road re-routing, unless you have all the gps traces downloaded to your > gps. > > This should be tagged by maxspeed anyway. Sure, but I'd guess that well over 99% of the roads in Australia don't have maxspeed tagged. If we can do some analysis on uploaded GPX tracks, and get an addition 0.1% of roads marked with a maxspeed, wouldn't that be better than nothing? > Some one may have also driven the road really slowly (push bike) and > some > one may have done it at the speed limit. This would skew any > reliability. If you simply take the mean of the tracks in the area, then yes. What you'd actually do is figure out the distribution of speeds and see that in that case there might be a couple of humps, one for pedestrians, one for cyclists and one for motor-powered vehicles. After that you'd need to take into account that people slow down for corners, lots of people speed, speed limits are generally are generally in multiple of 10km/hr and not over 110. It's going to be pretty complex, but if you can get some "free" data which is mostly-accurate for a small fraction of the roads, why not? >> * improving height maps, by taking (lots of) samples where altitude >> information was present. > > Pointless, vertical data is grossly out from a gps you are better off > using the NASA dem data. I agree here. >> * automatically guessing the number of lanes on a road, by looking at >> the variance of traces over sections in each direction. > > Should be tagged anyway (when more than 1) and how do you know it's > not an > accuracy problem. This is the other (along with maxspeed) thing I've been playing around with. You need a lot of tracks to do it. A *lot*. If gps track uploads were all marked with the type of vehicle (or walking) then you could also do things like detecting where cycle lanes were. > We have to trust that osm's are putting in accurate data but from what > I've seen the data already there is miles better than google maps > particularly in rural Australia. I think in general, the more raw data that we have and can potentially use if we want to, the better. -- James _______________________________________________ Talk-au mailing list Talk-au@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-au