Frank Steggink wrote: > Hi, > > While testing out the Python version of canvec-to-osm, I came across a > couple of huge features. Especially wooded areas have the tendency to > grow large. > > The second file I looked at (NTS tile 021L03), was already 3.1 MB large, > despite that I set maxnodes to 2000 in shp-to-osm. It was mostly > occupied by a giant multipolygon, which contains 321 members and more > than 30k nodes. When I opened this file in JOSM, it was really > struggling with it. Uploading this would be a real nightmare. > > Since the feature occupied less than half of the NTS tile, there would > even be room for several such features. In this scenario it is easy to > imagine that the nodes limit for getting data from the OSM server is > exceeded. I don't think this is a desirable situation, but I don't know > a clear solution how to deal with this. > > Although splitting up the features is not a good idea, it would at least > provide a means to upload the data in smaller chunks, and be able to > retrieve a part of the data, provided that the tile doesn't exceed the > server limit. Hopefully JOSM would also be more performant. > > For those curious, I have uploaded this OSM file here: [1]. It is part > of this area: [2]. > Anyways, check the file out for yourself, and please share any ideas how > we should deal with a situation like this. > > In the meantime I noticed that NTS tile 021L10 contains even a 4.1 MB > large file. If there are roughly 10k nodes per MB, this would mean that > all multipolygon members would contain at least 40k nodes... > > Regarding the Python script: the first version is nearly complete. I > want to make a couple of small changes to it, and also check if > everything looks OK in JOSM, and perhaps generate a couple of tiles from > it (locally). Once that is done, I'll make it available to whoever is > interested. It takes roughly 35 mins to convert all features (except > highways and hydro) in NTS tile 021L. Executing shp-to-osm costs most of > the time. The script also downloads any missing Canvec SHP files, but > they were already downloaded. > > Cheers, > > Frank > > [1] > http://www.steggink.org/osm/Canvec_test/021l03_VE_1240009_2_Wooded_area10.osm.zip > [2] > http://www.openstreetmap.org/?minlon=-71.5&minlat=46&maxlon=-71&maxlat=46.25&box=yes > > > _______________________________________________ > Talk-ca mailing list > [email protected] > http://lists.openstreetmap.org/listinfo/talk-ca > By the way, the rules file I used still defines tags for the inner polygons. Regarding the performance I don't think that matters much. The other file I checked has 43200 nodes in one file, so the huge multipolygon contains at least 41201 nodes. It has 745 multipolygon members.
Frank _______________________________________________ Talk-ca mailing list [email protected] http://lists.openstreetmap.org/listinfo/talk-ca
