Hi, > Hi! > > The weekend before last we had a workshop in Karlsruhe, Germany on the > topic of public transport in OSM. The idea was to bring interested > people together to improve the modelling of public transport > infrastructure and networks in OSM. > > The results have now been documented. See > http://blog.geofabrik.de/?p=23 for details.
While I like the proposal in general, I find that it makes rendering of public transport stops a lot more difficult. Currently, the renderer only has to put a symbol, where there are 'stop' nodes. For railway stations it can be sure that there is exactly one symbol on the line of the railway neatly aligned to the middle of the way. With the new schema a lot of preprocessing and guess work will be required to get the same result when stop places contain multiple stopping places and/or access points. The current situation with bus stops is more messy. (Just see Birmigham which seems to entirely consist of bus stops.) While stop places in the new schema allow to clean this up a bit, again, the renderer only has the choice to either paint two many symbols (all access points or all stopping points) or badly guess where to put the single point. So, somehow there should be a way to identify the main stopping place node and main access node of a stop place. This could be done through a role in the stop place relation but I would prefer a tag on the main object. In the Karlsruhe train station oxomoa had simply left the railway=station tag on one of the stop_positions (aka stopping place): http://www.openstreetmap.org/browse/node/25443575/history (See version 4. xybot is notified.) This is easy to handle for both the renderer and the mapper and is also backward compatible. We would just need new tags for those features where no tag exists yet. Another advantage of an extra tag: it can be put where there are no stopping places, e.g. on an intersection where there is a stopping place on each road the tag can be put on the crossing point of the ways where one would expect the stop symbol to appear on an overview map. I'm not sure if something similar is needed for stop place groups. Most probably the center point of the group will do for most applications. Another problem are directional stops, or worse, stops, which belong together but are quite far away. Take for example 'Waffenplatzstrasse' here: http://www.openstreetmap.org/?lat=47.3617&lon=8.52626&zoom=17 >From a rendering point of view I would like to be able to paint them as only one point in higher zooms and as two directional points in lower zooms. Higher zooms are handled by stop place and stop place group relations. For the directional points, however, the renderer would need to know if the stopping point is directional or not (oneway=yes, so to speak) and in the directional case be able to clearly identify the access point, so it can align the symbol accordingly. (It should be able to find out if the access point is on the right or the left side of the line where the stopping point is on. No direction=right/left tag needed.) Thus, if above example is modelled as two stop places with oneway=yes and both stop places are put into a stop place group "Waffenplatzstrasse" (together with the two bus stops, which are incidentally directional as well) all necessary information for the renderer should be there. Is this within the intended use of stop places and stop place groups? The Wiki is not very clear on this point. (NB: For a non-native English speaker, it might be hard to remember which one is the stopping place and which one is the stop place. I'd prefer less error-prone terms. Just my two cents.) Sarah _______________________________________________ Talk-transit mailing list Talk-transit@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-transit
