2009/6/26 Steve Singer <[email protected]>: > On Fri, 26 Jun 2009, William Lachance wrote: > >> Hi all, >> >> I've been needing to use geobase2osm in a project of mine (not >> directly related to the geobase import), and noticed (as other people >> have) that it's generating a lot of duplicated nodes. Aside from being >> unclean and wasteful, this makes the generated osm file non-routable. >> Well, today I decided to do something about it. Looking at the source, >> I noticed quite a bit of complicated code to "merge" identical OSM >> nodes at junctions (trusting geobase to provide the right hints of >> where junctions are). Evidently this wasn't working quite as expected. > > >> >> I decided to try something simpler: just keep a hashtable of node >> "keys" (latitude and longitude) as you go along, and reuse nodes that >> have occurred before. :) At first glance, this approach seems to work >> fairly well. It seems intuitively "right" to me that if two ways have >> a common lat/lng point in common, they should be connected. A quick >> count of running the two algorithms on Edmonton, Alberta, reveals that >> where the old script resulted in 77242 (!) overlapping nodes >> (sometimes up to 8 on a single lat/lng position!), my code resulted in >> 0. > > Is this because the geobase data doesn't define Junction objects for those > positions or some other reasons? Can you post a few examples of these? > I wasn't aware that recent versions of the script were still doing this. (I > probably won't get to look into the details for a few days though)
Here's a few examples of this: 1. Intersection at spruce grove of two highways with dual carraigeways: http://www.openstreetmap.org/?lat=53.5578961&lon=-113.9100716&zoom=14&layers=B000FTF 8 duplicated nodes here. 2. Intersection in Saint Albert of a highway with dual carraigeways with some dead-end roads: http://www.openstreetmap.org/?lat=53.6560873&lon=-113.6120644&zoom=14&layers=B000FTF 6 duplicated nodes here. I've uploaded a full list of duplicated nodes for the Edmonton area, if anyone wants to see more evidence. :) It's just a raw list of lat/lng coordinates, prefixed with the number of duplicated nodes that geobase2osm is generating at that position. Check it out at: http://wlach.masalalabs.ca/edmonton-dupe-nodes Do we have consensus that it would be better to use my approach? If so, how do we go about updating the "official" script? -- William Lachance [email protected] _______________________________________________ Talk-ca mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-ca
