2012/5/23 Martin Vonwald <imagic....@gmail.com>: > Let's have a look at a street around here: it has two general lanes, > one cycle lane and two side walks. I should map this with: > * one way is "main" way > * two ways for the lanes > * one way for the cycle lane > * two ways for the side walk > * one relation > So this gives me seven ways and one relation just for one street.
First of all: it is not "just for one street", it is 5 "lanes". If there are houses on the street, you will get more mays for instance. And more nodes for housenumbers, telephone booths, post boxes and so on. Obviously more detail will result in more data. Secondly I guess this would be the maximum you could do for a simple street like this (plus maybe some areas ;-) ). I would not map it like this even when using the proposed area relation. Suggestion (for the same street), high level of detail (i.e. I would use this only for special cases, not for the average road without irregularities): * one way (highway at the center) like it is now. From your description there does not seem to be any advantage of mapping the two lanes explicitly. * two ways for the sidewalk (if you like, mapped at the outside of the sidewalk so it can be used to generate easily the area of the street) * one way for the cycle lane (if you like) * nodes (or short ways) for the lowered kerbs * one relation (area) to connect sidewalks and road and kerbs (you would define the general kerb with tags in the relation and add the lowered_kerbs geometry as exception to the relation). So I end up with 4 ways (highway, 2 sidewalks, cyclelane), one relation (area) and some nodes (lowered kerbs). Of course this is more complex, but you also get a whole lot more of detail, especially if there is more stuff to take into account (geometry not perfectly parallel, barriers which are (partially) between the sidewalk and the road, ability to map barriers on the sidewalk only, etc. You will not map every street with this detail I guess, but you could do it for situations that are complex in the real world. Doing it with tags instead of dedicated geometry would in most (complex) cases result in much less readable map data than explicit geometry (IMHO). > If I > want to move the "street" I have to move seven ways. why would you want to move a street that you have surveyed up to this level of detail? I think this is hypothetical (and btw: it is 6 in your example). > If I want to add > a junction I have to add a node to every way. Yes, (see above, really not likely that you map a street with 5 ways in every detail and then you discover that you "forgot" a whole junction). Of course the junction will be more complex to map compared to a simple node, but this is also one of the reasons you are doing it: to get more details how the junction looks like. > If the connecting road > is also represented by seven ways I would have to connect... no, I > don't count now... a lot of ways. actually you would have to connect only those ways that are intersecting in reality, not all of them (see above). > Now I want to add a route relation for a bicycle route. For this I > have to split the "street". not at all, you will have the cyclelane where you put the relation to and you will _not_ have to split the street. This is one of the big advantages. In the other model you will have to split the street (cars) also for any change of attributes on any of the ways (sidewalks, cyclelane, ...), resulting in very fragmented roads (the more detail you add the more the center road gets fragmented), while this will be reduced a lot by having dedicated geometry to put the attributes to where they belong to. > I have to split all seven ways, even if > the bicycle route only refers to the bicycle lane. Excuse me, I'll > stop right here. I don't understand you here, can you explain this? > BTW: >> you will not get the support of who is interested >> in the details of shape. > If one would allow to change the width of each part at each node of > the xway, you could quite nicely cover the shape of many features. how would you know how to interpolate between two widths? It could be a sharp corner or a smooth change. (almost) every corner at every intersection is rounded. Will we split every x-way in y parts at any of these points? Won't it be very difficult to get the center and widths right in the case that the change of width is all on one side of the street surface while the other keeps going straight? (This is almost always the case btw.). Cheers, Martin _______________________________________________ Tagging mailing list Tagging@openstreetmap.org http://lists.openstreetmap.org/listinfo/tagging
