[Tagging] The actual use of the level tag (redux)

[Minh Nguyen]

Vào lúc 07:22 2022-03-15, Marc_marc đã viết:
> Le 15.03.22 à 08:05, Minh Nguyen a écrit :
>> it states a clear preference for level=0 to represent the ground 
>> floor, even in regions where the ground floor is normally called the 
>> first floor.
> 
> I consider that level is linked to the local numbering of the building 
> (if present). so if a building has a level 12 and then 14, I will never 
> fill in level=13, no matter if it is in a country where the ground is 
> represented by 0 or 1
> in the same way, if a building has a level 0 0.5 1, I don't see any 
> reason to invent another numbering which often becomes incomprehensible 
> (osm would be unwise to give a company a level=x when it is something 
> else indicated on the spot)

These cases are already usually handled by non_existent_levels=13 on the 
building and level=0.5 level:ref=M on a mezzanine. In theory, one-based 
floor numbering could be implemented using non_existent_levels=0, but 
that value is no more common today than it was in 2019. It would also 
run into the principle of avoiding tagging nationwide default values on 
individual features.

>> Anecdotally, if such tagging ever came to the attention of mappers on 
>> talk-us or OSMUS Slack, I'm pretty sure it would be quickly identified 
>> as an error.
> 
> the best thing would be to talk to them about it (and until then, we can 
> consider the tag as poorly documented and therefore not usable in this 
> country)

Yes, my point is that the tag was poorly documented, but I'm hoping my 
recent edits have helped to address that problem.

>> For a more holistic analysis
> 
> I very rarely put level=0 and almost systematically level=1,
> do you deduce that I'm in a country where level=1 is dominant ?
> no, I simply didn't put level=0 on 99% of the items I create
> if the building have no level<>0 items, I nearly never add level=0
> to shop at the ground level for ex.
> I'm not saying it's a good thing, it's just my experience.

First of all, I only analyzed 19 countries known to use one-based 
numbering in everyday life. [1] This discussion is irrelevant to other 
countries that use zero-based numbering anyways.

I'm confident that the four countries I identified are so lopsided -- in 
South Korea, 50% of all levels are 1, only 5% are 0 -- that it can't be 
explained by the phenomenon of default tags alone, unless we suppose 
that South Korean shops are seldom at ground level and South Koreans are 
much less likely to tag default values than anyone else. One-based 
tagging is a much more likely explanation.

For other zero-based countries, such as the United States, I fully 
concur with you that level=0 is often being used as a default as part of 
zero-based numbering. You can see plenty of examples of this in the mall 
analysis I did.

[1] https://commons.wikimedia.org/wiki/File:Countries_numbering_floors.svg

-- 
minh at nguyen.cincinnati.oh.us