OpenStreetMap
I’ve run my find_small_displacements program on Japan, and found some problematic imports with a large number of densely overnoded features, here are some:
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Bad import of natural=wood around Fukuoka. These were tightly spaced, yet also wildly inaccurate, off by as much as 80 meters and covering lots of non-wood areas, even covering motorways. I’ve reduced most of them, and aligned a few areas, but there’s lots more to align. The original upload was in 2010 with changesets like this one.
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Bad waterways, especially in Hokkaido and Kyushu, but also across the country; these are not just overnoded but also overtagged, consider this little stream near Taketa, Ōita:
- KSJ2:COP_label=1級指定区間
- KSJ2:DFD=流下方向不明
- KSJ2:LOC=c03671
- KSJ2:RIC=8909180118
- KSJ2:RIN=軸丸川
- KSJ2:WSC=890918
- KSJ2:curve_id=c03671
- KSJ2:filename=W05-07_44.xml
- KSJ2:river_id=gb02_03671
- layer=-1
- name:ja=軸丸川
- name=軸丸川
- note:ja=国土数値情報(河川データ)平成18年国土交通省
- note=National-Land Numerical Information (River) 2006, MLIT Japan
- source=KSJ2
- source_ref=http://nlftp.mlit.go.jp/ksj/jpgis/datalist/KsjTmplt-W05.html
- waterway=river
Issues with this little waterway:
- Poorly aligned; off by 20-60 meters in all directions.
- A large number of tags that belong on the changeset, not the feature; to its credit; this wasn’t a practice back in 2010 when it was imported.
- Overnoding, using 1085 nodes for what is well represented by 40 nodes.
- It’s tagged “river”, but is clearly a small stream.
- “layer=-1” for every single waterway.
Also somewhat alarming, JOSM does not show all the tags (!?), the “KSJ2:” tags are present on the feature but do not appear in JOSM’s GUI. I could not find any option in JOSM to make these key/values show up! Perhaps a JOSM expert could weigh in, or I should file a ticket.
Discussion
Comment from Viajero Perdido on 3 March 2018 at 20:40
JOSM seems to have a (hidden?) list of deprecated tags that it keeps under cover.
I’ve noticed (coincidentally today), while browsing my own work in achavi, that when I touch a highway to edit a tag, JOSM also removes two tags, geobase:datasetName and geobase:uuid. These are from old imports, and I assume they’ve been declared utterly useless - and thus removed without comment.
That would explain the “remove obsolete tags” or somesuch that I keep seeing in my command history. It’s nothing I’ve done knowingly.
Comment from Viajero Perdido on 3 March 2018 at 20:44
PS, it may be the SImplify command that removes those tags.
Comment from SomeoneElse on 3 March 2018 at 21:03
(re tag removal) JOSM, and some other editors, will remove some imported or previously set tags that subsequent discussions have suggested are best removed. See the comments at https://wiki.openstreetmap.org/wiki/Key:created_by for example.
Comment from bdiscoe on 4 March 2018 at 00:07
Thanks Viajero and SomeoneElse, i tested it and that is indeed the case:
That’s a fascinating undocumented JOSM feature. I approve of it, although in this particular case, I’d argue that even more of the tags in this particular import could/should be removed, including: * “note” and “note:ja” which are absurd to have repeated on every single way. * “source_ref” which doesn’t tell you anything that “source” doesn’t already. * “name:ja” which is an identical copy of “name”; unlike some other countries, Japan’s OSM data has no issue of exonyms appearing “name” tags, so this is truly useless.
Comment from Nakaner on 4 March 2018 at 20:46
Hi bdiscoe,
you might have a look at following mailing lists discussions:
Best regards
Michael
Comment from _yog on 5 March 2018 at 00:03
Japan has a lot of bad data due to imports.
There was the big road alignment project launched in 2015 that had a good success and helped cleaned a lot but I know I’ve been realigning, combining short segments and reducing the number of points on straight roads for the past 2 years around the Nagasaki region, and I’m far from being done…
The task is huge.