[Tagging] The actual use of the level tag

Roland Olbricht roland.olbricht at gmx.de
Mon Jan 21 21:38:57 UTC 2019


Hi Tobias,

thank you for keeping the discussion. One extra thing I have just 
learned is that non-numerical level refs are not-so-uncommon in the US, 
hence should be covered by a tool to be helpful there.

 > I do not want to sound so combative or negative here - to reason
 > for why a new tag may be useful, I just need to describe the problem.
 > I want us all to be on the same page.

I am still not yet sure about where we are starting from and where we 
are going to.

Typical examples would be for me:
https://openlevelup.net/?l=-2#20/55.68178/12.55260
https://openlevelup.net/?l=-0.5#18/51.23423/6.77858

I do consider both to be SIT compliant.

In both cases there is no building outline (at least no canonical one; 
footprint on the street level is different from the total of passenger 
visible area is different from the area covered by concrete foundations 
and so on).

In particular, there is no object that could or should carry tags 
applying to all involved objects. Given that one often cannot even 
decide for a station complex whether it is one or multiple stations, 
there often cannot be a global object responsible for the structure as a 
whole.

The half numbered levels for the small mezzanines fit intuitively into 
the whole level order -2, -1, 0 as signposted by the operator. Thus 
there also is no need for an explicitly declared order on a global object.

There is an obvious order of the levels there by reading them as 
fractional numbers. And all tools I am aware of (OpenLevelUp, JOSM, 
OpenStationMap and others) can work with this sequence of levels.

So I do support to have new extra tags that keeps whatever important but 
yet missing information.

But I do not see yet why there should be a mapping of levels to integers 
at all. Clarifying this point probably would help to understand whether 
there is a preferred choice for 0, whether missing levels need to be 
modeled at all and what to do with small mezzanines: Shall they trigger 
to have a gap for them in a potentially large building complex? Can 
disjoint mezzanines between larger levels get the same level designation 
to keep the index dense?

Best regards,

Roland



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