[Tagging] Tags useful for rendering of roads in poor conditions

Fernando Trebien fernando.trebien at gmail.com
Fri Jan 3 19:42:42 UTC 2014

Well, Peter, I feel that we cannot reach an agreement on "which
tagging recommendation is best" (in a way that is both semantically
meaningful and also useful for rendering of unpaved/unsealed ways)
because we all have "one preferred tag" and we are not willing to let
go of that. A new tag covering all the needs that have emerged so far
would overcome this problem.

That table tells me that:
- smoothness has more granularity for paved surface types (best for
city dwellers in developed nations)
- tracktype has more granularity for unpaved surface types, apparently
with a focus on motor vehicles (best for countryside dwellers or city
dwellers in some developing nations)
- mtb:scale and sac_scale have more granularity for unpaved surfaces
that are too bad for motor vehicles (best for sports but can apply to
some situations in the city in developing nations)

So we have different "best" tags to describe "how good a surface is"
in different ranges of surface "quality". To me, they all have a
similar purpose: to express how hard it to pass through a specific
way. I believe people had different kinds of traffic in mind when they
proposed each tag, and each ended with more "resolution" in its main
range of interest, while not taking much other ranges into account.
These ranges overlap, and a complete map (to satisfy everyone's
tastes) would require all of these tags in combination (something that
we may not be willing to recommend). Advocating one of these tags over
the other is a little like not caring much for the needs of a specific
group of users.

Tracktype seems concerned only with motor vehicles, and perhaps a
little with vehicles such as a bike. Smoothness explicitly mentions
its concern with a wide range of vehicles, but then is not so precise
for some unpaved kinds of roads (where tracktype is more precise).
Surface may be a bad decision after all because since there are both
precise and imprecise values (considering ease of travel for multiple
transportation modes). It's obvious what the surface tag means (the
surface material and structure), but it's not so obvious (as some have
pointed out) in which condition that surface is.

I don't think that unifying them all into a single tag is a bad idea.
It would be easier while editing the map (only 1 choice to make,
instead of 5), easier to describe to users (instead of 5 different
tags), to consume in applications (such as the renderer, but also in
routers), and it would also use less database space. It's a big
culture change, but it simplifies a lot of things. Moreover, we could
leave some space between the classes that we establish now so that
new, intermediary classes can be added in the future (if tracktype had
done that, maybe I'd be advocating for it right now).

On Fri, Jan 3, 2014 at 4:55 PM, Peter Wendorff
<wendorff at uni-paderborn.de> wrote:
> Hi Fernando.
> I'm not exactly sure what you want to show with your table, but if you
> want to add a new tag to integrate all existent systems (surface,
> tracktype and so on), and if you table should be a way to calculate that
> fourth tag, then why should we add the tag itself?
> Who really needs a single value tag "quality" if it's value can be
> calculated from other tags by a simple function?
> If not, what should the new tag do what the old one(s) cannot express?
> A simple numeric tag tend to increase confusion on when to use which
> value, as it's sometimes the case with some of the old tags already.
> regards
> Peter
> Am 03.01.2014 18:19, schrieb Fernando Trebien:
>> I decided to extend my comparison between tracktype and surface, now
>> including smoothness. I think we may need a new tag to integrate all
>> surface quality classification systems (it can well be a simple
>> numeric tag). See this: http://i.imgur.com/yEJ52eE.png
>> On Fri, Jan 3, 2014 at 1:49 PM, malenki <osm_ at malenki.ch> wrote:
>>> Am Thu, 02 Jan 2014 19:36:13 +0100
>>> schrieb Peter Wendorff <wendorff at uni-paderborn.de>:
>>>> I know (without being able to show you photos or something like that)
>>>> ways that are paved with paving stones (and thus clearly counted as
>>>> paved), but due to tree roots below the way and so on are
>>>> tracktype=grade3 or worse
>>> This is the point where we have a look at smoothness=*
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Fernando Trebien
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