[Tagging] Basic philosophy of OSM tagging

johnw johnw at mac.com
Fri Jan 16 03:53:41 UTC 2015


> On Jan 15, 2015, at 8:33 PM, Mateusz Konieczny <matkoniecz at gmail.com> wrote:
> 
> > 4 lane ‘tertiary" road that handles 5 times the vehicle traffic, traveling on to connect with 2 major trunk roads -  
> > intersects the narrow two lane “secondary road”  that is one of the small roads coming down from the “suburbs” into the city
> 
> Interesting. I was unaware about so drastic changes in meaning of tag by editors. This one cripples Japanese road data - 
> and I am unsure what could be done about it.


http://www.openstreetmap.org/edit#map=20/36.33615/139.21688 <http://www.openstreetmap.org/edit#map=20/36.33615/139.21688>

The “secondary road” I speak of (I was mistaken, it isn’t a primary).  To the north, it was recently widened (again) and nice, but below rt. 17, if it didn’t have a shield # - it would be an unclassified road (as it doesn’t even have a center line and a very awkward turn at a narrow level crossing). 



http://www.openstreetmap.org/edit#map=19/36.40643/139.07303 <http://www.openstreetmap.org/edit#map=19/36.40643/139.07303> 

The “tertiary” road intersection. it connects the primary and the trunk intersection to the west (rt 17 / 6), and then (after being secondary for a block) meets a “primary road” is tertiary again for several KM as it heads down to the rt 50 trunk road and on to “primary” rt 2. This kind of situation occurs a lot in cities where old roads meet new bypass roads. I had tagged and retagged it as a secondary, but reverted it to tertiary because I have decided to follow the OSM:JA rules in this case (after writing my long-winded example).

http://wiki.openstreetmap.org/wiki/Japan_tagging <http://wiki.openstreetmap.org/wiki/Japan_tagging>

They follow their shield system, which places roads into categories which often do line up as you expect, but in cities, where there are newer major roads that connect the older ones, or in old neighborhoods that are bypassed by newer roads, it does not represent the road system very well sometimes.  Notice there is no mention of the road size or traffic flow consideration - just shield numbers. 

http://www.openstreetmap.org/edit#map=16/36.9819/139.3064 <http://www.openstreetmap.org/edit#map=16/36.9819/139.3064> 

One of the roads in my region, Gunma Route 1, runs through what is now the largest national park in Japan, and some pieces are completely closed to all public road traffic (it is not continuous), besides the park shuttle bus. I assumed I could drive on it (as it is labeled as a primary road, no tolls), and drove up there to find (a) it is a narrow service road and (b) roped off, and only the park shuttle bus is allowed in (as opposed to private busses and taxis, as with other “limited access” park roads in Japan).  I re-tagged the private section as a service road, and hastily made the park entrance months ago.  it still has it’s ref=1. 



Honestly I don’t mind them being screwed up (besides the rt1, because you cannot drive on it whatsoever) - because it is the way that Japanese people expect maps to be presented to them. They have pretty rigid ways of representing maps - and they have adapted OSM to fit their national mapping scheme and expectations:

The two unconnected sections of rt. 1 -  the thin yellow portions are not drivable by the public, but still labeled as primary regional roads because of the shield type/number. http://www.mapion.co.jp/m/basic/36.93219243_139.3159987_5/t=print/size=640x740/icon=home,139.31599869871812,36.93219243059891/ <http://www.mapion.co.jp/m/basic/36.93219243_139.3159987_5/t=print/size=640x740/icon=home,139.31599869871812,36.93219243059891/> 

The “tertiary” intersection 
http://www.mapion.co.jp/m/basic/?t=print&lat=36.4033877201575&lon=139.0776209799907&scl=9&icon=home,139.0776209799907,36.4033877201575/ <http://www.mapion.co.jp/m/basic/?t=print&lat=36.4033877201575&lon=139.0776209799907&scl=9&icon=home,139.0776209799907,36.4033877201575/>


As you can see, rendered width of the roads is the defining feature of use (check Google Maps, it uses Zenrin data up close to show the width too) and the classification below “trunk" is less important,  whereas in OSM, the classification is most important.  The width and standards of most roads changes drastically as they go along, and rendering the width change is easer than reclassifying the roads section by section to reflect changing road standards (width, traffic volume, shoulder, curve radius, expected hazards, etc). 


BTW - the way Mapion renders different neighboorhoods, borders, and other things are quite interesting, especially as it drastically changes with the zoom level. http://www.mapion.co.jp/m/36.43371388_139.05561388_8/v=m1:群馬県前橋市関根町28/ <http://www.mapion.co.jp/m/36.43371388_139.05561388_8/v=m1:%E7%BE%A4%E9%A6%AC%E7%9C%8C%E5%89%8D%E6%A9%8B%E5%B8%82%E9%96%A2%E6%A0%B9%E7%94%BA28/> might have some good ideas for -carto in the future. 


Javbw


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