[Tagging] [OSM-talk] Should we map things that do not exist?

stevea steveaOSM at softworkers.com
Sat Jan 2 19:57:13 UTC 2021

As a longtime mapper of rail in North America familiar with much of its history in OSM and many of its nuances, I concur with Richard's characterizations.

A distinction between how Kevin stated "abandoned" and how Richard did is that "tracks still present" isn't usually the case.  In the USA, a status of "abandoned" is a formal, legal designation (by petition of the railway, not always granted) which influences how and whether USA mappers use the tag "railway=abandoned."  Nonetheless, correctly, mappers SHOULD follow our wiki [1] definition for this abandoned:  "where the rails have been removed but the route is still visible in some way."  This is followed by the clearly-stated "If the rails are still in place use railway=disused instead."  Happily (in the USA and parts of Canada where I've observed this), this is usually the case based on my experience with encountering both tags and comparison with aerial imagery.  I'm not sure of the accuracy of Richard's "90%" but in my experience of North America rail editing, it is a very high percentage of extant tagging which follow his "tracks vs. no tracks" values.

As Richard says, newer values for key railway have emerged:  dismantled, razed, demolished.  Our wiki for Demolished railway [2] says "Mapping of completely non-existent railways is considered as out of scope for OSM. But railways can leave long-lasting traces and at least some mappers consider even small vestiges of rail as being sufficient for mapping very broadly."  Several images are included to help characterize tag value determinations.   Wiki inquires for values for key railway of [razed, dismantled, historic] all redirect to Demolished_Railway ([2]), so there is some modest attempt at "semantic compression" centralizing one wiki to encompass these three tags.

We might continue discussion of "should we map..." in this thread as we are, although in the case of railway=*, our wiki does a good job of explaining both history and our current practice.  It has been storied and for some remains controversial, as misunderstandings remain, but the combination of "railway" and "does not exist" continue to become better tagged and have their associated tags documented in our wiki.  I suggest that for railway, further discussion be taken to the Talk (Discussion) page of [2].


[1] https://wiki.osm.org/wiki/Tag:railway%3Dabandoned
[2] https://wiki.osm.org/wiki/Demolished_Railway

> On Jan 2, 2021, at 10:26 AM, Richard Fairhurst <richard at systemed.net> wrote:
> Kevin Kenny wrote:
> > disused - track still present, could be put back into service 
> > with minimal work (vegetation clearance, track inspection, ...)
> >
> > abandoned - track still present, deteriorated, would need 
> > construction work (repairing washouts//slides, realigning 
> > track, removing trees, ...) before being placed in service
> >
> > razed - rails lifted or buried [1], sleepers and ballast may 
> > remain, traces on the ground such as embankments, 
> > cuttings and drainage features observable OR track visible 
> > in obsolete imagery and way included to prevent re-
> > addition of a demolished feature.
> That isn't how the tags are customarily used.
> In OSM to date, the majority usage is
>     disused = tracks still down
>     abandoned = no tracks but clear traces remain
>     dismantled (or razed) = no clear traces
> This has been the case since OSM year dot and was strongly influenced by the terminology traditionally used in the UK. dismantled/razed is a newer tag.
> Obviously individual mappers have their own preferences, but in many years of editing features adjacent to disused railways, I'd say the "disused=tracks, abandoned=no tracks" rule is followed in 90-something% of cases.
> (dismantled/razed - the tags are synonymous - is something I find useful where a railway bridge deck has been removed, typically over a river or road, but the pillars or abutments are still standing.)
> Richard

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