[Tagging] Blatant tagging for the renderer: bridges & abandoned railways

moltonel 3x Combo moltonel at gmail.com
Tue Mar 10 00:25:48 UTC 2015

On 09/03/2015, Bryce Nesbitt <bryce2 at obviously.com> wrote:
> Ah thanks, I stand corrected. railway=razed would be the tag to discuss.
> The broader point is intact.

While there is a pretty strong consensus that osm describes the
present (leaving openhistoricalmap for the past), it seems that some
railway contributors like to map the past (that's what 'razed' and
'reused' describe). Railway=razed is the equivalent of keeping the
building=house way after big appartment blocks have been built and
maped in its location. Railway=reused (i believe it's usually tagged
as 'abandoned') is the equivalent of tagging 'this used to be a post
office' after it has been turned into a shoe shop. These comparisons
may be poorly chosen, but you get the idea.

I never understood what made railways different from buildings, shops,
streets etc in that respect. Maybe because it's easyer to deduce where
a railway used to pass than where a cotage used to be ?

To make things worse, a number of enthusiastic contributors have
tagged 'abandoned' what should have been tagged 'razed' (or better:
not mapped at all). This fact contributed to the decision of not
rendering 'abandoned' anymore.

> When making sense of abandoned bridges and oddly rounded buildings in
> various places, it is super helpful
> to see the context of the prior railroad grade.  It helps in mapping from
> the air and on the ground.
> A given railway grade may (and often does) exist as razed, abandoned,
> disused, and reused (e.g. highway=residential or highway=service,
> leisure=park) along it's length.  So how can we represent the former way,
> and the current use of each bit,
> in a rational way?

If there's still a bridge or maybe even an embankment, then
railway=abandoned is fair game (assuming it hasn't turned into, for
example, a highway=track in the meantime). And it'd be nice if
osm-carto rendered these bridges and embankments even though
railway=abandoned isn't (they are working on the former, at least).
These bridges are interesting to the contemporary map user. The fact
that they were built for a railway is only interesting to the
history-inclined map users, which osm-carto has decided not to target.

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