Am 11.05.2011 23:45, schrieb Stefan Bethke: > Am 11.05.2011 um 23:01 schrieb Tobias Knerr: > >> M∡rtin Koppenhoefer wrote: >>>> If you follow the convention that each way should be drawn along the >>>> center of the real-world feature, then the width of e.g. a sidewalk can >>>> still be determined at any point along the road from just the single >>>> outline area and the way position. >>> >>> no, if this would be possible there would be no sense at all to map >>> areas. You can't see sidewalks as "just another lane", because they >>> tend to be quite irregular in certain settings (unlike lanes which >>> usually keep their width and have no corners and other weird points). >> >> I don't think this contradicts my argument. Look at the cross-section of >> the road at any point: >> >> | * . . . . * | >> >> The vertical lines are road area outlines, the stars are sidewalk ways >> and the dots are other "lanes". >> >> If we make the assumption that each way marks the center of that "lane", >> we can easily calculate the width of the two sidewalks at this >> particular cut through the road: It's 2 times the width between the >> sidewalk and the area outline. > > The last time I checked, we're mapping in two dimensions, not one :-) > > I'm not sure that mapping the actual physical extent of the various parts of > roads is feasible in terms of number of mappers and their motivation, but if > anybody is serious about mapping crossings and physical properties of these > areas, I think mapping them as areas is the obvious and logical way forward.
Well, I'm pretty sure that I wouldn't be happy if mappers felt that they had to draw the outline of every single lane in a road. I also wouldn't be happy to implement support for two different mapping styles (especially considering that these are > > We already map waterways with both a way and an area. I'd map the road, the > sidewalks, connecting areas, crosswalks, parking spots, what have you, all as > areas (if I felt I had exhaused housenumbers on buildings etc.) I'd probably > add curbs as ways, not areas, unless they have multiple steps in them and > approach a meter or so in width. > > Of course, that doesn't answer how anybody would be able to tell that all > these features together form "the road", except for their proximity. I'd > like to learn about where that information would actually be required. Example: A 2D rendering wants to visualize highway=residential as a way with two : Describe an algorithm that does that based on a bunch of ways, each with its own area, where these areas don't even necessarily share nodes. Any sensible rendering for applications will *not* render . You wouldn't see anything in lower zoom levels, and the exact shape of a sidewalk is pretty much irrelevant for most purposes. So they will draw a fixed-width line for a highway (much wider than it is in reality), and maybe colored casings depending on whether or not there are sidewalks. > > > Stefan > _______________________________________________ Tagging mailing list [email protected] http://lists.openstreetmap.org/listinfo/tagging
