OSM Indoor Meeting 2024-06-05

Previous meetup: https://wiki.openstreetmap.org/wiki/OSM_Indoor_Meeting_2024-03-06
Next meetup: 2024-09-04 18:00 CEST in https://osmvideo.cloud68.co/user/tob-2uf-drl-eal (recurring every first Wednesday of the third month of each quarter at 18:00 CE[S]T)
- Volker will be traveling that day, Tobias volunteered to chair the meeting instead.

What happened since last time?

model as two rooms (status quo), let the consumer code merge this based on identical room numbers
relation with most tags, and member geometry per level, what member role?
no relation but dedicated tagging to assist with merging room parts (room:part=?)
...?

Are there precedents for any of that yet?

Discussion:

related: a shop spanning multiple floors in e.g. a mall or train station
- similar in that it needs the relation, but physically two rooms with separate floors
- is that similar enough though to model this the same way? semantics vs physical shape
variants of the relation model:
- keep tags duplicated on the members, which is easier to consume but duplicates tagging
- members only contain the level tags, other tags are only on the relation
try to avoid risks of misunderstanding this as a multi-polygon (for humans and tooling)
preferred solution: relation
- empty role for members
- type key:
  - type=room is too specific (would type=area for indoor=area be needed as well?)
  - type=multilevel/multistory is better and more generic, and also covers the multi-level shop case. Ideally we'd find a name that doesn't start with "multi" though to avoid ambiguities with "multipolygon".
- ways need at least the level tag, no level tag on the relation
- moving tags only to the relation would probably be ok for indoor mapping, as that is fairly niche/specialized, but for multi-floor shops that might not be the case, tooling/rendering there might also not be prepared for e.g. shop relations
  - counter-example for tagging on the relation: building parts, there the tagging is put on the "main" polygon, but that isn't directly applicable here lacking a "main" element
alternative approach for the shops: node with the tags, relation for the geometry

landing areas, e.g. https://www.openstreetmap.org/way/107673567
- indoor=area probably sufficient both for rendering and routing, no standardized specialized tagging exists yet
geometry for individual (large) steps, e.g. https://www.openstreetmap.org/way/107673622
- center line tagged as highway=steps (exists) and outline polygon tagged as area:highway=steps
- remove geometry for individual steps
- add same level tag on the outline as on the center line

How to tag rooftop terraces (e.g. https://www.openstreetmap.org/way/107673613)? This is neither indoor nor a room really, but very much part of a building.

indoor=area semantically similar, but counter-intuitive
balconies are similar, if not worse for exceeding the building outline. There is building:part=balcony though.
location=roof + room=terrace should work