[Talk-transit] Proposal for simplification of mapping public transport

[Roland Hieber]

On Mon, Apr 09, 2018 at 07:19:32PM +0200, Jo wrote:
> Here goes my proposal for a reform in mapping public transport:
> 
> https://wiki.openstreetmap.org/wiki/Proposed_features/Public_Transport_map_all_stops_as_nodes
[...]

As I understand it, in Public Transport schema speech, this proposal
comes down to removing all public_transport=stop_position nodes (i.e.
the position where a train/bus/… stops on the street) from the route
relations, and retaining the public_transport=platform information
(i.e. where the passengers wait or where the station pole is located).
This would be effectively reverting part of the Public Transport schema,
and going back to the way platforms were mapped previously.

However, a main reason why the Public Transport schema was adopted [1]
was exactly this differentiation between stop position on the route and
platform position/waiting area for the passengers.  This was done to
increase the expressiveness of OpenStreeMap data, and to make
information more easier obtainable for routing software.  After all, the
two things are at different positions, and you cannot generally infer
the one from the other.  Reverting to the old schema would therefore
take away that expressiveness.

[1]: https://wiki.openstreetmap.org/wiki/Proposed_features/Public_Transport#Goal_of_this_public_transport_proposal

Furthermore, quoting from the proposal:

> Rationale
>
> - nodes are convenient to work with and move, if needed, also using
>   mobile apps

This is true, but per the Public Transport schema you can already map
both public_transport=stop_position and public_transport=platform as
single nodes.  Your additional argument that both a node and a way could
be added for the platform would not lead to more expressiveness, but
only to more duplication of data.  (As simple as possible, as complex as
necessary.)

> - nodes have coordinates directly, no extra calculation required
> - nodes are easy to work with using MapCSS, [...]

See above.  Also, every way consists of nodes, which have a coordinates.
Just take any.

> - making comparison of location and tags with external sources is
>   straightforward

I don't know how this is meant, but the complexity of tag extraction
from objects will be the same whether they are mapped on a node or
mapped on a way.  Also the main work here is probably to match the
external database schema to the OpenStreetMap data schema, as they will
most probably not be very similar.

That's all I can think of for now.

 - Roland