On Wednesday 12 August 2009 20:36:54 Jochen Topf wrote: > On Wed, Aug 12, 2009 at 07:18:03PM +0200, Pieren wrote: > > On Wed, Aug 12, 2009 at 7:04 PM, Martin > > > > Koppenhoefer<dieterdre...@gmail.com> wrote: > > > 2009/8/12 Jochen Topf <joc...@remote.org>: > > >> in real life bridges don't start in the *middle* of junctions > > >> so there *is* a little bit of non-bridge roads between the junction > > >> and the bridge. > > > > > > +1 There *is* nothing. It is all an abstraction and *this* abstraction is not helpfull or get us anywhere. As I stated before a crossing between a big road and a (much) smaller road does not either get little bits of road inserted in the smaller road to cover the width of the larger road because it makes no sense. Even though the smaller road ends at the edge of the larger road not the middle of the road.
> > > > That's a stange argument. In real life, traffic signals are also not > > in the middle of junctions. So you add nodes per traffic signal on > > each way arriving at intersection ? In real life, oneway streets do > > not have oneway road sign on the middle of junctions, so you split > > your way to be sure that oneway is really starting at the right > > centimeter in the street ? > > Modelling the real world is always a compromise. When mapping a oneway road > we do it from the junction, because it doesn't really matter where the sign > is exactly for the road to be oneway, also routers would get very confused > otherwise. But if the oneway sign is a few meters into the road, say after > an entrance to a parking lot that should be reachable, I'd split the road > there. So would I. > > A traffic signal is something that probably belongs more to the junction > than the road, so it sort of makes sense there. But of course I can also > move the traffic signals somewhat down the road, if I want to have all the > details, say if there is a fan-out and only one branch has the traffic > signal. I have never tagged traffic signals myself, so I am not the expert > on that. > > But a bridge often needs a ramp, even if its a small one, so there is some > space there where the road is not a bridge yet. So I do think there is a > difference to the examples you mentioned. "often" here just means that you 'often' have to add an extra piece, not always and no rule. > > But, again, the real world is always more complex than any rule people come > up with. I'll mostly go with the most practical compromise: Easy to map and > easy to use in current software. But my point is that this 'rule' is causing the opposite of what you want. Is adding a segment between a bridge and a junction where in reality there is none 'practical' and 'easy to map'. The rule maybe simple the consequences are not. > That often leads to inconsistencies, but > inconsistent is not necessarily bad. Exactly, no need to 'force' junctions to have connecting roads on the same layer. If you really believe in the 'middle of the junction theory' let us be inconsistent with that one and help mappers clean up real issues rather than adding titsy bits of road between junctions and bridges. > And if we get better software or more > detailed data or want to support new uses, we'll change things around. Can we agree on getting rid of the "Right" and especially "Wrong" texts that deal with this issue in the Map Features and give some advice like: "Often bridges/tunnels will not connect directly to a junction in which case you should/can (?) add a piece of road connecting the two." ? Lambert Carsten _______________________________________________ talk mailing list talk@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk
