[Tagging] what does maxheight=none mean?

Tom Pfeifer t.pfeifer at computer.org
Mon Oct 27 09:20:24 UTC 2014

Thanks mmd for shedding some light on the background of this tagging.

As said before I am not against keeping a record of a bridge being checked,
just the value =none is misleading.

Another problem is that the tag is on the way under the bridge, and
not the bridge way itself. That leads to the situation that somebody
tags a 15km motorway because one bridge is unsigned. The next mapper
splits the way to tag some turn:lanes, and thus creates segments
of the road where there is no bridge at all.

JOSM should be no problems, since the validator could consider the
exemption once a method has been agreed on.


mmd wrote on 2014-10-27 07:27:
> Tom Pfeifer  writes:
>> I stumbled over some maxheight=none tags on motorways, that did not even
>> pass under a bridge. I found that this is the most frequent value of
>> maxheight (2889 of 41474).
> Tom,
> thanks for bringing this up. As the author of Maxheight Map ([1], [2]) I'd
> like to put some of this discussion into perspective. Originally user
> Win32netsky started a thread "Brückenhöhen eintragen in die OSM Karte" [4]
> (adding maxheight infos to the OSM map) in the German forum, which attracted
> more than 200k views and over 700 replies in the meantime. So this topic
> already got quite some attention in the past, at least in Germany. To see
> the huge momentum, visit the Wiki page [3] to see maxheight mapping progress
> in Hamburg, Germany in the last four years.
> We started to create the Maxheight Map arond 2 years back as a way to
> support mappers in finding still unmapped bridges. At the same time, we were
> looking for some way to express that there's no explicit maxheight
> information (vulgo: no maxheight sign). The implicit limit as defined by
> legislation would require a sign if the bridge is lower than < 4m
> in Germany. For this purpose maxheight=none was invented to indicate that
> there's no explicit maxheight limit. It was clear that the analogy to
> maxspeed=none is somehow broken, but other ideas like maxheight=unspecified
> didn't make it. We thought, well maxheight=none is here to stay.
> Now enters JOSM: for some reason, they decided to create some rule to flag
> maxheight=none as warning, as "none" is not a valid number. Suddenly mappers
> started to remove those tags (JOSM must be right!). I picked this up in [4],
> but it was sort of inconclusive. German OSM podcast "Radio OSM" discussed
> this ('maxheight=none is bad'), but nobody really got the underlying idea.
> Thanks a lot for Peter Miller's thoughts on this btw., that's exactly our
> motivation!
> Following the "Radio OSM" story Martin K. started to invent
> maxheight=unsigned and added this to the German wiki page without much
> consultation/feedback from the community . I know "unsigned integers"
> (=positive numbers), but unsigned maxheight seems a bit weird to me as a
> non-native speaker. Maybe someone can chime in
> here if this makes sense at all. Others started to propose
> maxheight=default, which looks a bit better to me.
> But again, we somehow need to start formalizing this a bit more, so that
> - Mappers can be confident again to use the right tagging, that there's a
> consensus to tag this stuff
>    (after all if you look at the situation in taginfo and the actual numbers
> for maxheight=none, the idea behind this tagging is really widespread and
> commonly used by mappers!)
> - JOSM no longer complains about maxheight=(not a number) and people stop
> deleting those tags
> Thanks for your time
> Best
> mmd
> [1] http://maxheight.bplaced.net
> [2] http://wiki.openstreetmap.org/wiki/Maxheight_Map
> [3]
> http://wiki.openstreetmap.org/wiki/DE:Maxheight_Map#Beispiel_-_Entwicklung_in_Hamburg_von_2010_bis_2014
> [4] http://forum.openstreetmap.org/viewtopic.php?id=14154
> [5] http://wiki.openstreetmap.org/wiki/User_talk:Dieterdreist#maxheight
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