Patrick Kilian wrote: >Sent: 23 October 2008 12:30 PM >To: Shaun McDonald; OSM dev list >Subject: Re: [OSM-dev] collection of gps tracks > >Hi, > >>> In more detail: >>> I'm looking for an area with a high density of gps traces (collected >>> only by car). >>> Where a single road can be assign to several Tracks (10 and more). >> >> When we upload a GPS trace, there is no tagging as to the mode of >> transport. Thus finding this information will be difficult. >Traveling by car should have some features which can be detected >statistically. High speed, small slowdown when going uphill, rarely >passing over footways etc. > > >>> The Idea: >>> To extract informations of a collection of tracks that can't be >>> extracted by a single one. >>> As an example: You could extract the number of lines for a road and >>> tag it in OSM. >I had that idea myself, but didn't have time to actually try it. > > >> GPS traces are unlikely to be accurate enough to be able to get the >> number of lanes on the road. >If you have only a docent track? right. But what if you have 100 tracks? >Or 1000? It's going to need a health dose of advanced statistics so. >
It doesn't work because each time I drive down the same lane the GPS will give position of that lane within a few metres but each trace on different days will not exactly overlap each other. In reality because of satellite position and numbers of satellites on view at any given point in time the positional accuracy will vary. As a result you cannot discern individual lanes from multiple tracks. The only way you reliably know the number of lanes is to record the number or to drive all lanes immediately after each other. the number of passes then = the number of lanes but would of course be very time consuming. Noting the number of lanes during survey is so much easier ;-) If a dense area of GPS data is needed, try Sutton Coldfield, UK where I have a huge number of tracks to and from uploaded. Its obvious which are by car as I generally don't cycle much above 30km/hr ;-) Alternatively any of the main UK motorways. Lots of traces on those. Cheers Andy _______________________________________________ dev mailing list dev@openstreetmap.org http://lists.openstreetmap.org/listinfo/dev
