> the basic rendering issue where streets already collide with buildings
The renderer can always be updated to accommodate any issues with showing where sidewalks exist. This is a situation of having more information available for display, and how to organize it, which isn't a bad thing. For example, you could put `footway=sidewalk` ways at a lower z-level and have basically zero impact on street rendering. > where do I put the crossings other than make them up? All crossings are made-up, but some have markings that make it easier. Where you put them depends on local laws and mapping considerations, but at least having them connect around every intersection is good practice. F> A pedestrian can cross the road anywhere and will not want a route that does not allow that most basic of concepts. This varies geographically quite a bit, and there are very few routes that would be improved by adding this consideration. Or, in other words, how often do real routes need someone to cross at arbitrary locations, with basically zero metadata to assist with safety / mobility infrastructure? Examples: 1) Your origin and destination are very close together and you have no mobility preferences except 'walking'. In this case, routing and sidewalks are pointless, just draw a line from A to B. Several routers make that interpretation already. 2) There are several 'shortcuts' along the optimal path, such as alleys, and one might expect that the router would keep having you go out of the way to use intersections. Alleys would naturally be connected to streets and intersect with sidewalks, so these paths *will* be followed so long as the router allows short trips on streets/driveways (most do). 3) There exist common entrances to parks / other footways that involve crossing the street. In this case, it would of course make sense to add a crossing way. Finally, tagging streets with `sidewalk=*` has these same issues. In order for routing to actually use the information to figure out how infrastructure is connected, it has to make an expanded graph that maps sidewalks and how they're connected, and you're back to any potential issues with mapping sidewalks as separate ways, but you now have lower-quality information to work with. The ability to "cross the street anywhere" doesn't really exist in most routers, because they're really just treating you like a car that moves slower, and crossing (and the sidewalk, typically) doesn't exist at all in that paradigm. On Sun, Dec 10, 2017 at 10:46 AM Philip Barnes <p...@trigpoint.me.uk> wrote: > On Sun, 2017-12-10 at 18:25 +0000, Nick Bolten wrote: > > The downside of using `wheelchair=no` is that there are many conditions > that will prevent some, but not all, wheelchair users from using the > infrastructure. For example: some wheelchair users don't care about curb > ramp info at all because they're comfortable finding driveways and going in > the street (`kerb=raised` does not imply `wheelchair=no`), while others > absolutely require proper infrastructure (most powered wheelchair users, > `kerb=raised` implies `wheelchair=no`). I recommend tagging specific, > on-the-ground conditions that can be interpreted later, like `kerb`, > `barrier`, `width`, `surface`. > > Another thing is that you probably want this info to be immediately > useful, but I'm not aware of any existing routers that can use sidewalk=* > subtags, as the sidewalk=* on a street model has to be expanded to a new > graph (and the vast majority of routers don't do that). OpenTripPlanner is > attempting to develop this, but it's unreleased. That doesn't mean you > shouldn't tag, but it's a segue for my next recommendation: consider > mapping sidewalks as separate footways. More or less, you describe > sidewalks as `highway=footway` `footway=sidewalk`, connect them via > `highway=footway` `footway=crossing` ways, and ensure that those crossings > intersect and share a node with streets. While this involves more ways, it > makes it much easier to organize and use the kinds of subtags you're > interested in using, and can be used directly in most routers. For example, > you wouldn't have to make an executive decision about `sidewalk:width` vs > `width:sidewalk` - just use the widely-documented `width` tag. > > > > Mapping as separate ways can cause many issues, the basic rendering issue > where streets already collide with buildings, plus where do I put the > crossings other than make them up? > > A pedestrian can cross the road anywhere and will not want a route that > does not allow that most basic of concepts. > > Phil (trigpoint) > _______________________________________________ > Tagging mailing list > Tagging@openstreetmap.org > https://lists.openstreetmap.org/listinfo/tagging >
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