On 31 July 2010 03:02, Nathan Edgars II <nerou...@gmail.com> wrote: > On Fri, Jul 30, 2010 at 8:44 PM, andrzej zaborowski <balr...@gmail.com> wrote: >> On 31 July 2010 02:33, Nathan Edgars II <nerou...@gmail.com> wrote: >>> On Fri, Jul 30, 2010 at 8:28 PM, andrzej zaborowski <balr...@gmail.com> >>> wrote: >>>> I don't see how it changes anything. If a piece of interstate I-405 >>>> is described by one relation or two ways one for each carriage in osm, >>>> and 10 segments in TIGER, than that's a way to describe it. >>> >>> So how would you do any of the applications described above? They all >>> require either a single TLID or everything to be tagged with a field >>> that includes the correct TLID (due to joining, splitting, and >>> redrawing, the latter is not true). >> >> So your program tries to come up with a route, it knows it's driving >> on road A in osm. >> A has id=1 and is tagged "tiger:tlid=20:21:22:23", and it is connected >> to road B (id=2, tiger:tlid="24:25:26:27") by node id=3. You also see >> that tiger way 23 meets 24. That clearly means that from osm road A >> you can go into tiger way 24 when you reach node id=3, without even >> looking at the geometry and fuzzy guessing things (remember routing >> works on huge graphs). > > But road A has been rerouted since the TIGER data was created and now > ends at road C, without touching road B. You can't use shortcuts like > this.
Sure it can be outdated same as any other tag value. > > Or am I misunderstanding your example? If you already know A and B are > joined at node 3, what do the TLIDs tell you? The TLIDs tell you you where you are if you want to switch from OSM routing to TIGER routing at that node for example. And they tell you road A in TIGER has (say) 4 crossings with other roads, so if that's not true in OSM, you know one of the maps needs fixing. If something changes between TIGER2006 and TIGER2009 you can see which osm segments may need fixing too. >> >> Or say that the government releases a database that says how many >> traffic signals there are on each segment of road. Then you can find >> the junction nodes on which they should be in OSM, or at least count >> how many there should be on a given street. > > TLID 24 has two lights and TLID 25 has three. Joined TLID 24;25 might > have four or five. Well.. sure, possible, but that's assuming that the database was made in such unfortunate way that each single lights can be counted two or more times. The census data tends to not be that bad (at least in the design) > Add one to the possible error for each new segment. > Then split out bridges and it becomes unmanageable. Again note about bad data in osm.. Plus if your program sees a non-bridge segment with tiger:tlid=20:21:23 and a next (bridge) segment with the same tiger:tlid, it should really notice that the five traffic lights are somewhere on those two segments, not five on each. >> >> And yes, street names are not 100% correct or complete in OSM today.. >> we don't remove them though. > > So are you saying you or someone else will be checking all TLIDs > against the TIGER data and correcting errors and adding missing ones? So people in Germany are mapping curb heights for streets. There's the openpistemap and special tagging for ski piste types. There's a whole spectrum of informations with different numbers of people who care about it, and it changes in time. (specially when a visualisation becomes available.. who cared about dupe nodes before the dupe nodes map?) Cheers _______________________________________________ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
