Jochen Topf <[email protected]> writes: > On Tue, Oct 12, 2010 at 04:36:34AM -0400, Peter Budny wrote: >> Frederik Ramm <[email protected]> writes: >> > Peter Budny wrote: >> >> I'm building a robot as a school project that will use data from TIGER >> >> imports and automatically create route relations for US state roads. >> > >> > My advice is not to do it; if it can be done automatically, route >> > relations are not required >> >> If route relations are not required, then what are >> http://wiki.openstreetmap.org/wiki/Relation:route#Road_Routes for? > > Good question. What are they for? I never understood that either. :-) > >> They /are/ required, because roads may be discontiguous in various ways: >> a road may change names (e.g. Main Street North becomes Main Street >> South, but to a driver or pedestrian, both are just one continuous Main >> Street), or even be physically discontiguous (some state and even US >> Highways do this). > > So? > > Is any application actually using this? And what for? > > I am not beeing facetious, what are these routes actually useful for that > the tags on the roads don't already do?
Road routes are useful because it avoids the dreaded semicolon (as someone else called it). For instance: I would love to see the correct symbol for roads on the map--an Interstate shield, a US Highway shield, or a State Road shield with the shape of the state. In a road relation, a URL to this is stored in the symbol=* key. The renderer would just find all the road relations a way is part of, grab their symbols, and place them on the map. Currently no renderer supports this. They draw ovals and put the ref=* inside, which would be okay... except that they don't support semicolons. What they /should/ do is split the tag by semicolons, and place all the resulting tags on the road individually. What they /actually/ do is try to place a giant ref=* tag inside the oval, which usually means giving up when you have "ref=US 29; US 78; US 278; GA 8" (and that's assuming you don't use the long US:US and US:GA format). Relations are the cleaner solution here. You /could/ accomplish the same thing with regular tags, but who wants to see symbol=*, symbol_1=*, symbol_2=*, etc. on every way in a city? (Or worse, a giant symbol=* tag with semicolon-separated URLs?) -- Peter Budny \ Georgia Tech \ CS PhD student \ _______________________________________________ dev mailing list [email protected] http://lists.openstreetmap.org/listinfo/dev
