Hi Peter, good stuff, and I agree with your view that we should tag the "human understandable" levels. I'm not aware how how precisely these map to the layers tag (I'd always assumed that this was a hint to the renderer rather that conveying semantic information), however I see how that would work.
By the way, I think it may be useful to create a separate "railway stations (in the UK)" project page on the wiki, so that we can easily see which ones are "done" and to which level of detail. On 04/09/2009, Peter Miller <[email protected]> wrote: > > In the absence of a vast building program of new monorails[1] as > proposed by Bill Ricker, I am beginning to think about mapping some of > the more complex transport interchanges here in the UK. I am currently > adding platforms, walkways and steps to the simpler stations that I > know and am now thinking about more complex ones. > > Bill also talked about the use of the layer tag on some stations on > the monorail at Disney with the stations at layer 3 and the track at > layer 2 and I think it would be useful to talk about how we can > usefully use layer tags for complex interchanges. > > I checked out the IFOPT CEN standard[2] on the subject and found this > useful section on "Vertical Levels (Layers) versus Altitude" (they > call them levels, we call them layers btw) > > 1.4.6 Vertical Levels versus Altitude > Transport interchanges are often complex buildings with many > interconnected levels. The > labelling and description of the levels is used in describing stops > and directions in PT info > systems and so needs to be part of the Fixed Object model. This LEVEL > is a distinct concept > from that of a vertical spatial coordinate in that it is a semantic > label (for example > Departures, Basement , Floor 1, etc). Altitude is in effect the z > coordinate of a POINT. > > > I think this useful for us and clarifies that if the station appears > to be organised on two 'layers' (using OSM terminology) then it > doesn't matter that in fact one of the layers incorporates an incline > at one point so that part of 'layer' it is at a different altitude to > another part. If of course if there is a slope which connects two > different distinct layers of the station (something which could also > occur) then we should consider that to be a path between the layers. > > The logic is that when we start mapping more complex 3D stations (and > other structures) then we shouldn't get too stressed about altitude, > but should instead divide the place up into human understandable > layers. This is something that is often done anyway in diagrams that > describe the layout of stations[3] and ships[4]. > > When we come to map this we are going to need an editor that can allow > us to see only one level at a time, but there is a growing need for > editors to allow one to focus on one aspect of the data only and avoid > picking up or modifying features that are out-of-scope anyway so I am > sure that will come. While being focused on a particular layer then > any features added would be added at that layer. > > We would also need to consider slope, steps and lifts between layers > and the situation where a lift only connects some layers but not all > of them. A lift is currently represented as a single node because it > is vertical. How does one indicate which layers it connects? How would > one assign layers to a complex metro station where one can't guess the > depth of each element - possibly one would have to count steps and > measure the height of one of them to calculate a depth for each > platform and therefore assign layers.. but that still does solve the > problem for escalators.... So, possibly we can be kept occupied even > without a massive monorail program. > > Fun stuff ;) > > > Peter > > > > [1] > http://lists.openstreetmap.org/pipermail/talk-transit/2009-September/000593.html > [2] > http://en.wikipedia.org/wiki/Identification_of_Fixed_Objects_In_Public_Transport > [3] > http://home.wangjianshuo.com/archives/20080105_shanghai_metro_century_avenue_station.htm > [4] http://www.wildalaskacruises.com/capabilities.htm -- Frankie Roberto Experience Designer, Rattle 0114 2706977 http://www.rattlecentral.com _______________________________________________ Talk-transit mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-transit
