[Tagging] Data redundancy with "ref" tag on ways vs relations

Paweł Paprota ppawel at fastmail.fm
Mon Jul 30 22:41:24 BST 2012


As I wrote before in this thread in response to the hiking trail example
- this is great, I myself love mapping forest tracks for mountain biking
and stuff.

But maybe I should have made it clearer in the first place that I'm
talking about major roads - this stuff really should be in tip top shape
(relations created, no discrepancy with ref on ways/relations etc.) in
order for OSM to be considered for use in navigation. Now if I want to
drive across Europe I will get many different approaches - in Poland
there are these errors I mentioned, in Germany I have seen that they
have hierarchical relations and also separate relations for
backward/forward lanes. There are also for example Euro routes that e.g.
Polish roads/relations are not part of. I cannot imagine any navigation
or location software working with such data.

So my point here is very specific and maybe we misunderstand each other
because I failed to stress it enough. Ideally there would be QA tool
like OSMonitor running for every country in the world (or one instance
checking whole world) so that people could sync around the world and
create unified approach to the major road network tagging.

Paweł

On Mon, Jul 30, 2012, at 23:19, Jo wrote:
> > there are different types of errors and you focus on one only. I am not
> > going to argue with examples or explanations. If you don't want to see it
> > you won't see it.
> >
> 
> I'll try to give another example, which may or may not help Pawel to see
> what you mean:
> 
> I'm gathering information about bus routes. When a mapper is in front of
> a
> bus stop, they can easily take note of all the lines serving this bus
> stop
> and adding this information to route_ref.
> 
> Now I come along and create a route for the itinerary of one of the
> routes.
> It helps me that I can find all the bus stops served by this line with a
> regular expression.
> 
> Should all the route_refs now be removed once the route relation is
> created? I don't think so, as they can easily be used to help verify
> (programmatically like you did) that my route relations remain correct.
> One
> could argue that this creates redundancy of data in the database, but
> this
> redundancy is what makes data validation possible.
> 
> 
> For giggles I downloaded all ways with ref=N2 with an overpass query (
> http://overpass.osm.rambler.ru/query_form.html):
> 
> (
>  way
>   ["highway"]
>   ["ref"="N2"];
>  >;
> );
> out meta;
> 
> I should have added a bbox there to limit it to Belgium, but most of my
> Overpass queries are more specific.
> 
> I found that we don't seem to be using relations for N-roads, but we do
> for
> A-roads and E-roads (i.e. all the motorways). I also found that here in
> Belgium those roads seem to be 'interrupted' through the city centers,
> which would complicate checking them for continuity.
> 
> Polyglot
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