On Thu, Jun 21, 2018 at 11:34 PM, Martin Koppenhoefer < dieterdre...@gmail.com> wrote:
> > I am with Jo here: the stop_positions at bus stops do not add any > information, at most they would add convenience for data consumers (if > every bus stop had them), but OSM traditionally values mapper convenience > higher than simplicity of data evaluation. > I don't fully comprehend all the implications of PTv2. I don't fully comprehend the capabilities of routeing engines as currently implemented or how they may be implemented in future,. I'm considering only the aspects of this that affect buses, not other PTV2 categories. So there may be extreme Dunning-Kruger ahead... I'm starting to think (probably incorrectly) that the stop position on the highway is more valuable in a relation than the platform but the platform is more valuable than the stop position in rendering. As far as routeing goes, the stop position is important. When I switch between bus/foot I do NOT (in most circumstances) walk through the platform itself and there's only a 50% chance I will walk past the length of the platform. Platforms are often offset from stop positions, such as https://www.google.co.uk/maps/@52.0841293,-4.6605633,3a,75y,333.25h,77.93t/data=!3m6!1e1!3m4!1sC6vWAGH4rcR2EoMfVZcIjQ!2e0!7i13312!8i6656 If I get off the bus there and turn left I don't walk past the platform. If I get off and turn right I'd only walk through the shelter if there were people blocking the rest of the sidewalk. I know it's only a matter of a metre or so, but from a strictly technical perspective the routeing is from the stop position, not the platform. Even if the underlying mechanics is taken care of by the database engine, it takes more CPU and memory to find the segment of a highway closest to a platform than to find the highway that a node (stop position) is on. Of course, I could be completely wrong about that. If there is any merit to the idea I put forward that stop position and/or platform should be interspersed in the route relation rather than gathered at the beginning (I'm not convinced there is merit in the idea, but I would find it easier to figure out what is going on in a bus route relation if they were interspersed) it feels more natural to me to have the stop position than the platform. Taking all that into account, it feels more natural (to me, when thinking of bus routes) that platforms are physical objects unrelated to bus route relations but which should be rendered and that stop positions are a necessary part of bus route relations but which should not be rendered. I don't even see a necessity to "link" the two via an auxiliary relation as some seem to have suggested. As far as I understand it, I actually have the choice to map it this way (although whether I choose to include platform or stop position in the relation they currently have to be gathered at the start of the relation) without breaking any rules. If I'm right, the only downsides are that I have to map two distinct objects (platform and stop position) and I have to repeat information (the name of the stop, at least) for both. Or maybe I'm completely missing the point of just about everything. -- Paul
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