Re: [Talk-us] [OSM-dev] Super-relations or not
Marcus Wolschon mar...@wolschon.biz writes: I'm using routes in way-simplification to generate simplified maps for realtime rendering of larger areas when zooming out. It's quite a lot of work with LOTS of cases to try to sort route-relations that are randomly sorted with parts being other relations instead of ways, parts being contained twice, parts missing in the relation but having a ref= -tag or a ref_nat= -tag or ... , parts having a ref= -tag with the wrong road-number that should NOT be made a part of this simplified way,... In fairness, much of that sounds like errors. A route relation ought to contain exactly the things that are part of it, no more no less. The ref=* tag on ways is irrelevant for a route relation. What would you prefer to see the structure of the relation be, given your druthers? Should both directions of a road be in one relation, tagged with roles? Should a oneway=no way have a role? Should it be in the relation twice with different roles? Should there be separate relations for each direction with a super-relation to hold them both? If super-relations are used, does it still make sense to use forward/backward tags as appropriate? As far as I'm concerned, the difference in what's required to tag things is minimal between these concerns. Therefore, wouldn't it make the most sense to choose whichever is programmatically the easiest and most flexible to deal with? -- Peter Budny \ Georgia Tech \ CS PhD student \ ___ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
Re: [Talk-us] [OSM-dev] Super-relations or not
Andy Allan gravityst...@gmail.com writes: On Fri, Oct 29, 2010 at 2:45 AM, Peter Budny pet...@gatech.edu wrote: That doesn't work; there are cases where it's ambiguous. If you look at [1], US-278 runs along North Avenue (bottom) and Ponce de Leon Avenue (top), connected by Monroe Drive (left) and Piedmont Avenue (right). The problem is that North Ave and Ponce de Leon are both oneway=no, while Monroe and Piedmont are oneway=yes. So unless you run a routing algorithm over the relation, you can't figure out just from the oneway tags that US-278 westbound doesn't include North Avenue (which you would otherwise assume from it being oneway=no). Someone, somewhere, has messed this up good an proper. I can't find the origins of this discussion to figure out where it's arisen from though. The situation you describe is easily dealt with using Route Relation roles forward and backward as per cycle routes, or bus routes, or every other route relation. See for example http://www.openstreetmap.org/?lat=51.8lon=0.89395zoom=17layers=00B0FTF It's clearly documented here: http://wiki.openstreetmap.org/wiki/Relation:route#Members and rendered on multiple maps. However, I see from elsewhere that people are making route relations in the US and filling the memberships with west and south and suchlike and then finding this causes problems. My advice is to stick to the route relation member roles that work for every other type of route, and if people ray want to have separate routes for I5 East and I5 West then feel free (something that hasn't seemed necessary elsewhere) - but don't put the words east or west in the ref, add an additional tag to the relation for overall direction or something. But please, stick with the forward/backward stuff for route relations roles, it works well. Okay, let's presume for a minute that blank/forward/backward is the correct method. I'll grant that it does have its advantages, such as for the scenario I described. However, when I look at http://ra.osmsurround.org/analyze.jsp?relationId=78041 (in Belarus) or http://ra.osmsurround.org/analyze.jsp?relationId=93920 (in Canada), the display is meaningless. It hasn't bothered to connect the forward/backward ways to the ways with no role, so it's totally unclear what's going on. If you want this to be the standard way of tagging things, then we NEED to get the tools up to spec. I also noticed that Potlatch doesn't change the role from forward to backward when you reverse a way. (JOSM does the right thing, though.) My argument for super-relations is that they pretty much work NOW. You don't have to look at the roles... one relation contains one direction, end-to-end. P.S. I don't know why people haven't complained about this more. Maybe because most of the route relations are on motorways, which are almost universally dual-carriageway. In the US where lots of minor roads are signed as routes, and routes are sometimes discontiguous, I think the issues [will] stand out a little more. P.P.S. Why do I see so many route relations where a way has been added more than once, sometimes up to 5 times, with the same role? What is that supposed to mean? -- Peter Budny \ Georgia Tech \ CS PhD student \ ___ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
Re: [Talk-us] [OSM-dev] Super-relations or not
On 29 Oct 2010, at 9:05 , Peter Budny wrote: P.P.S. Why do I see so many route relations where a way has been added more than once, sometimes up to 5 times, with the same role? What is that supposed to mean? typically an error. only use case where it makes sense is a bus route which sometimes uses some segments of a road multiple times -- Peter Budny \ Georgia Tech \ CS PhD student \ ___ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us ___ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
Re: [Talk-us] [OSM-dev] Super-relations or not
Hi, Peter Budny wrote: 1) The common way, up to now, for storing routes that alternate between single- and dual-carriageway has been to leave the single-carriageway parts without a role, or with the role north/south. This makes the order of the members of the relation meaningless, since you can't traverse the ways end-to-end in the specified order. There is no requirement for the order to have meaning; it is just a tool the server offers you, and you can use it or not. The way I view route relations, it is less about traversal and more about simply stating that a certain way belongs to a certain route. The route relation doesn't lose its usefulness if a little bit in the middle is missing. I would simply group all bits together in the route relation, including the dual carriageway pieces, and not worry about roles etc. - this can all be deducted from the oneway tags. This could be solved by adding the single-carriageway sections twice (once with north and once with south) Please no. 2) If the direction of a road (e.g. north/south) is indicated by roles, I recommend not to do that. If anyone has a compelling argument against super-relations, or for single relations, I'd like to hear it. Supporting both seems really pointless No, supporting them both is quite probably the best way forward. You can start with doing a simple relation, and when you find that there's something more complex to it you can still use a super-relation. I always preach that you should write your code such that wherever you expect a way, you also accept a relation that groups a number of ways. If that were done throughout, then a super-relation would just be a normal relation with one or two sub-relations thrown in as required. No need to go up the tree and demand that super-relations exclusively contain relations etc. Bye Frederik -- Frederik Ramm ## eMail frede...@remote.org ## N49°00'09 E008°23'33 ___ Talk-us mailing list Talk-us@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-us
