[Indoor] Indoor Routing Observations

[Volker Krause]

Hello,

I've been working on indoor routing recently and hit a few challenges. We 
discussed those at the Hack Weekend in Karlsruhe as well, but there isn't 
really an elegant solution for any of the following yet:


# Implicit corridor walls

indoor=corridor and indoor=room are defined to have implicit walls, unlike e.g. 
indoor=area (see https://wiki.openstreetmap.org/wiki/
Simple_Indoor_Tagging#Modelling_the_different_indoor_elements).

However the predominant use of indoor=corridor isn't really in line with that.

Example 1: https://www.openstreetmap.org/relation/3845325

This is entirely open to the north end leading into the main hall, closed on 
the south (with multiple doors) and on the sides it's either walls, adjacent 
shops (also see service counters below) or ways up to the platforms.

By the strict SIT interpretation neither the main hall nor the platforms nor 
the shop service counters would be accessible.

Example 2: https://www.openstreetmap.org/way/453091694

Open on short-edge ends, intuitively a "corridor", but by strict SIT 
interpretation all connections to staircases or adjacent halls would be 
closed.

Example 3: https://www.openstreetmap.org/way/870541411

This strictly follows SIT. All edges of the corridor either have doors or are 
actually walled (adjacent to rooms or the outer building wall).


For rendering this is mostly subtle, however for routing this is very 
problematic. With strict SIT interpretation many train stations are 
practically inaccessible. And when not using implicit walls you end up with 
routes through the building walls in example 3 (due to the next point).


# (Implicit) Outer building walls

indoor=area has no implicit walls but can occur with one or more edges aligned 
to an outer building wall.

Example 1: https://www.openstreetmap.org/relation/6038767

There are walls where this area aligns with the building outline on the north 
and south sides, ie. routing through those edges should not be possible (apart 
from the doors).

Example 2: https://www.openstreetmap.org/relation/11878686

Same situation here. However the building outline (https://
www.openstreetmap.org/way/23290301) does not match the actual outer building 
walls on the ground floor here, with the parking spaces on https://
www.openstreetmap.org/way/27743604X being on the outside and the building only 
extending to the full outline on higher levels.

Example 3: https://www.openstreetmap.org/relation/10142437

Here the area is open towards the outside. Assuming there's an implicit wall 
on the building outline would make this inaccessible for routing.


For rendering this again is relatively subtle, but for routing that's a 
crucial difference.


# Service counters

Less severe, but also occurring in many train stations is the fact that 
amenities are often tagged as indoor=room (and thus implicitly walled) but 
without any tagged doors, making it impossible to route into them. In many 
cases the fix here is adding the missing doors. However there are also 
amenities (bakeries, fast food stands, etc) that serve over a counter on an 
edge of the room polygon and don't actually allow you to enter. That counter 
is where routing should lead you to ideally, but how can that be tagged?

Example: https://www.openstreetmap.org/way/402790810

Free-standing room, service counter at the north-facing edge.


Any thoughts on how to deal with those issues?

Thanks,
Volker

PS: Please remember the quarterly OSM Indoor online meetup on March 6th 18:00 
CET at https://osmvideo.cloud68.co/user/tob-2uf-drl-eal!
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