On Mon, Mar 29, 2010 at 9:59 AM, john whelan <jwhelan0...@gmail.com> wrote: > Could some one have a look at any of the roads that have been imported in > this way especially in Orleans. They appear to have a tag of "Ontario > Canada" but no city tag. Should "Ontario Canada" be two tags? > > Looking at the roads it Ottawa the city center seems to be Potlatch created > again there is no city tag. > > How does the search engine know where the roads are when you do a search?
As I understand it, is_in= and addr:city=, addr:state=, tags on nodes / ways / and relations are deprecated in favour of a boundaries. First, we create a boundary relation[1] for Orleans, and other intersecting, overlapping relations for Ottawa, Ontario, Canada, Ottawa City Parks, Local Water Protection District, etc. That gives us nested / overlapping boundaries for these interesting bounded places. Smart tools like a postGIS select statement can tell you how many houses are in Orleans, or what is the minimum distance from Local Water Protection District to the city road-salt storage barns. Or can tell you that selected node #12345678 is contained in boundaries Orleans, Ottawa, National Capitol Region, Ontario, Canada, North America, Northern Hemisphere, Western Hemisphere, Earth, ... It can also tell us the area contained by boundary or the common area shared by overlapping boundaries. And when a boundary changes or moves (like voting area boundaries) only the boundary needs to be updated on the map. With is_in-type tags on nodes/ways/relations, to move the voting area, we'd have to find those affected nodes, and change them. And we'd eventually have countless nodes tagged with endless levels of boundary. Too big and less flexible. On the other hand, is_in-type tags were easier to use with simpler tools like 'grep'. So, what you see in Ottawa, without addr:city, is likely manually added by a local Ottawa mapper and pre-dates the 2009 import. The geobase 2009 import was around the same time that is_in-type tags were losing favour and the rise of boundary relations. And it's certainly possible to find stuff that has been combined or customized in other wonderful ways. [1] http://wiki.openstreetmap.org/wiki/Boundary _______________________________________________ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
