[talk-au] tagging 4WD and dirt roads - want it ?

Andrew Harvey andrew.harvey4 at gmail.com
Mon Nov 12 11:14:08 GMT 2012

On 11/11/12 09:31, David Bannon wrote:
> Andrew, thanks for the very carefully considered response. 
> I agree with just about all the points you make but suggest your
> conclusion may not quite address the driver for this proposal. This is
> about getting knowledge into the hands of end users. Safety is a key
> factor, I am sure you heard someone died on an outback track only two or
> three days ago.

I can defiantly relate to the driving force here. I myself have looked
at the osm mapnik map and planned a route based on it, only to find
myself reaching unexpected dirt (or worse sand) 20km into the road. I
wasn't prepared for the road becoming unpaved, but the tragedy was that
the road was actually accurately mapped out with surface tags, I just
never downloaded the data before the trip to find which sections were
paved and which were unpaved.

This is a complete failure of the cartography and if it represented
unpaved vs paved as dotted casing then I would have been prepared and
expecting the surface change along the road.

> What I am trying to do is get a reasonably easy to understand and use
> model in place so mappers put data into the database in a consistent way
> and, critically, the rendering people and the routing people use it. At
> present, we have a large number of tags that relate to this space but
> the only one the renderers use is tracktype. They ignore
> surface=unpaved, 4wd_Only, smoothness= and so on.
> Your suggestion, that we focus on specific characteristics of the road
> and describe them is a good thing and one I'd support if you were to
> start working on it as a proposal. But it does not apply here.
> While having breakfast I could easily think of ten items I'd like to add
> to your list of road characteristics, I'm quite sure that if we sat a
> few more 4wders around the table we could hit twenty in no time. If we
> convert them all to tags we'd have two real and pressing problems -
> 1. Mappers could not cope with that many tags to address in a consistent
> way, even if they did, think of the extra data that would be, in many
> cases unnecessary. Subsequent validating of such a fine grain data would
> be a daunting task.
> 2. Importantly - it would be impossible to get the rendering people to
> even consider displaying such a range of data. And if the mainstream
> rendering engines don't show it, the routing people ignore it. Truth is,
> when an end user uses OSM to decide to go a particular way, he/she does
> not fire up JOSM and examine the tags on each way, they look at a map,
> or, worryingly, rely on a routing tool.


Although I can synthesis with this, at the end of the day, osm projects
build the database, not a cartographic map.

You are free to make your own rendering style which represents surface
tags, similarly you are free to define your own routing rules which
determine how a routing engine chooses a route.

> I believe we need something simpler, something that is an extension of a
> tag that is already rendered, for example on the OSM website. Yes,
> tracktype does focus on compactness at present but thats because in the
> range of roads it currently addresses, thats the issue. I propose we
> extent that range of roads.

I think your extension proposal make is more complicated as it is
unclear what the scale represents since it isn't a linear scale for one
attribute. Admittedly the current tracktype tag also suffers from this
problem, but the wiki page does suggest the two attributes represented
separately as surface= and smoothness=.

It does seem to me that accurately taging surface (gives you an
indication if you need a 4wd for traction; --I'm not a 4wd user, so I
may be completely wrong about this), and smoothness (if you need a 4wd
for clearance) would sufficiently meet your requirements. If only it was
that easy... We have,


> WRT the mention of "bad data that needs to be fixed", you must note that
> this proposal does not make that issue any worse, indeed, by focusing on
> one linear tag, tracktype, it might actually help. The problem is not
> strictly linear but can be projected onto a linear tracktype scale at
> the granularity proposed given the sort of knowledge any reasonably
> experienced 4wder has.  Importantly, it's better than nothing and that,
> I am afraid, is the likely alternative.

Although this issue does affect Australia due to the nature of the
outback, it is a global issue. I think it would be best to take your
thoughts to the global tagging list at let the discussion happen there.

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