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

Dominic Hosler dominichosler at gmail.com
Sat Jan 4 00:07:19 UTC 2014

I've been observing for a while but I want to chime in on the discussion.

Let's not forget that mapping for OSM is not about the rendering, it's
about mapping what is actually on the ground. Therefore we are actually
discussing two different but related issues.

The first is how to appropriately capture the physical state of the road,
perhaps considering different seasons / weather possibilities. The second
is how should we suggest that the default map tiles be rendered to show
that some roads are 'more difficult' to travel using a certain category of

In my opinion the tagging should not include user specific descriptions
like 'bad' because of the obvious 'bad for what?' questions. I think that
the current 'surface=' tag does a good job at specifying the material from
which the road is made. Personally I think we should leave the surface tag
as it is, and maybe use the values to guess defaults for the condition. I
do think that there should be some other tag to describe the condition. The
suggestion of adding a 'surface:sealed=yes|no' seems to me a good idea, not
that I have much experience of any rough roads. We seem to be requiring a
standardised, not open ended, description of the quality of the road, to
extend the information of it's construction material.

I think we should combine the surface tag with smoothness, and make it
easier to understand for mappers. It should be well defined in the wiki
with example pictures as to what type of quality (frequency / depth of
holes, cracks or anything) corresponds to what value for smoothness.
Personally I am against combining it all into one tag, because that reduces
the detail of the maps, thus reducing the usefulness for those that render
their own maps for certain niche requirements. A combination of smoothness
and surface would be good. Possibly even including 'surface:stable=yes|no'
to declare if short term conditions (weather / seasons) will affect the
surface. These two or three tags should efficiently describe what is
actually on the ground, then we leave it to the renderer to decide how to
display it according to the users that renderer is targeting.

My opinion on the rendering is that there are already a number of usage
specific rendering and routing engines. Some render tags specific to
cyclists, some for lorries. I agree that the default map tiles should have
a different rendering for something along the lines of 'normal cars will
have to be careful / struggle on this road'. The exact line drawing of
exactly what would count as that would have to be decided and other use
cases who require a different setting may need to design their own
rendering styles.


On 3 January 2014 22:20, Fernando Trebien <fernando.trebien at gmail.com>wrote:

> My bad, I thought "Carto" was the name of the main Mapnik style. So
> I'm referring to openstreetmap-carto.
> Well, I was trying to expose my idea that the multiple current
> classifications of "trafficability" may not be necessary at all.
> On Fri, Jan 3, 2014 at 6:35 PM, Andy Townsend
> <lists at mail.atownsend.org.uk> wrote:
> >
> > On 03/01/14 19:56, Fernando Trebien wrote:
> >>
> >> Well, when proposing this, I'm trying to avoid these problems:
> >> - the set of paved and the set of unpaved surfaces is not closed, and
> >> so it would require us to continuously update Carto with new surface
> >> types
> >
> >
> > I'm a bit confused by what you mean by "carto" here.  The tool itself
> just
> > converts from a CartoCSS stylesheet (such as you can create/edit
> relatively
> > easily with TileMill):
> >
> > http://wiki.openstreetmap.org/wiki/CartoCSS
> >
> > The stylesheet used for the OSM standard map is:
> >
> > https://github.com/gravitystorm/openstreetmap-carto
> >
> > and for the HOT map is:
> >
> > https://github.com/hotosm/HDM-CartoCSS
> >
> > So there isn't just one "Carto" rendering.  Also, there's not likely ever
> > going to be "an agreement between everyone" about what sort of
> "suitability
> > for X sort of traffic" is represented on the "standard" map.  Personally
> I'd
> > argue that the whole tracktype / path / footway / bridleway rendering
> area
> > is "too complicated" now for lay users, rather than "not complicated
> > enough".  We've already had help questions on the lines of "what's that
> > brown stain on the map":
> >
> > https://help.openstreetmap.org/questions/13521/icon-explanation
> >
> > So the answer surely has to be different rendered maps for different
> > purposes - someone who's creating an MTB map can render the MTB tags,
> > someone who's mapping an area where "smoothness" is used in a sane manner
> > can map that, etc.  If someone wants to come up with a big x-dimensional
> > matrix that combines various tracktype / smoothness / mtb / whatever tags
> > into a numeric value, they can do that too.
> >
> > The good news is that it's actually easier than ever to do that now as
> > osm2pgsql now supports external tag transformations using a lua script:
> >
> > https://help.openstreetmap.org/questions/28465/osm2pqsql-and-lua
> >
> > https://github.com/openstreetmap/osm2pgsql/blob/master/README_lua.md
> >
> > It's so easy that even someone like me (with less design expertise than
> the
> > average three-year-old with a crayon) can do it to render other values
> > instead of tracktype without changing the openstreetmap-carto stylesheet
> at
> > all:
> >
> > https://github.com/SomeoneElseOSM/designation-style
> >
> > So if you think an extra tag makes sense ("trafficability" or something
> > else), start using it locally, create a map using it, and ask people what
> > they think.
> >
> > Similarly, if you think that some numerical combination of existing or
> new
> > tags to create a "new tracktype" would work, create a map using that.
> >
> > Cheers,
> >
> > Andy
> >
> >
> >
> > _______________________________________________
> > Tagging mailing list
> > Tagging at openstreetmap.org
> > https://lists.openstreetmap.org/listinfo/tagging
> --
> Fernando Trebien
> +55 (51) 9962-5409
> "The speed of computer chips doubles every 18 months." (Moore's law)
> "The speed of software halves every 18 months." (Gates' law)
> _______________________________________________
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