Hi, Am 2016-10-04 um 11:37 schrieb Martin Koppenhoefer: > 2016-10-03 21:54 GMT+02:00 Alexander Matheisen > <alexandermathei...@ish.de>: > >> The main problem I see for mapping stations as areas is the lack >> of defined boundaries. Compared to other types of POIs, the >> definition of a "station area" strongly differs depending on the >> background of the mapper and the use case. >> > > > most/many stations are fenced, using the fence perimeter will > typically give you a very good polygon approximation for a minimum > size, especially compared to a single node with no spatial extent > at all.
I agree with you that the extend of the area orthogonal to the direction of the tracks is well defined. But the extend along the tracks is different depending on the definition. Let me illustrate it with a figure I showed at my talk at SotM. https://wiki.openstreetmap.org/wiki/File:Station-asymmetric.svg (1) A passenger might define the station as the area around the platforms, the station building, and – that's another dispute – maybe in addition the bus stop and car parking. This is shown as the purple thick line. (2) Train staff and other people interested in railway operations have a much larger definition of the station. It includes the whole siding and yard tracks which belong to the station. Depending on the country, a station begins either at the entry signal (left outermost signal in the image) or at the first point a train passes when it enters the station. The station ends either at the entry signal of the opposite direction (right outermost signal in the image) or the last point a train passes which leaves the station towards the right edge of the image. This is shown as the thin rose line. If we used (1), we would exclude yard (freight) tracks near the platforms. But I think that many passengers include them into their definition of a station if they are located next to the platforms. (definition 3) As an result, you will have three definitions of a station. https://umap.openstreetmap.fr/de/map/unbenannte-karte_105414#17/48.94774/9.13638 shows you definition (1) and (2) at the example of Bietigheim-Bissingen. All tracks in Bietigheim-Bissingen which do not have a platform, are freight tracks. Definition 1 is shown in blue, definition 2 in red. I think that we should use the established tag railway=station for nodes only because the node will located where everyone agrees that there is a station. If we tag (2) with railway=station, the centroid of the area will be at a position where users would not expect it – neither passenger nor railway staff. Assymmetric stations (Bietigheim is rather symmetric) occur quite often. https://wiki.openstreetmap.org/wiki/File:Station-asymmetric.svg Terminus stations are a obvious example of an assymetric station. The Best regards Michael -- Per E-Mail kommuniziere ich bevorzugt GPG-verschlüsselt. (Mailinglisten ausgenommen) I prefer GPG encryption of emails. (does not apply on mailing lists)
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