[Tagging] Classifying roads from Trunk to Tertiary and Unclassified

Warin 61sundowner at gmail.com
Tue Aug 13 00:21:45 UTC 2019

On 13/08/19 02:02, Joseph Eisenberg wrote:
> yopaseopor,
> My initial question was really about Indonesia in particular, and
> countries without established, official highway classification systems
> in general.
> But I took a look at Spain, and while I don't know much about the
> local road system, the use of highway=trunk vs highway=primary looks
> quite good!
> See the current rendering around the city of Soria, Spain:
> https://www.openstreetmap.org/#map=8/41.749/-2.444
> https://www.openstreetmap.org/#map=7/41.500/-2.340
> There is 1, and only 1, trunk road (or motorway) from Soria to each of
> the 7 cities around it.
> This is also true of Cordoba:
> https://www.openstreetmap.org/#map=8/37.9875/-4.7763
> And it looks like every place=city in Spain is connected by
> highway=trunk or highway=motorway to all of the other cities. This
> means you can render a map with just these 2 tags and place=city, and
> have a complete national roadmap.
> I actually think this is a great example of what I would like to see
> in Indonesia.
> In contrast, look at Toulouse, France:
> https://www.openstreetmap.org/#map=7/43.588/1.384
> - A highway peters out to the northeast (toward Lyon) and to the south
> (toward Andorra). But if you zoom in to see the primary roads, it's
> clear that the highway has switched from trunk to primary mid-route.
> This makes it difficult to render a proper map.

I think your confusing tagging with rendering.

Tagging is what is on the ground.
The road from Toulouse toward Lyon may physically change between the two, so the tagging follows that (I don't think so but as an example?).

Rendering then has to make choices. If the choice is simply based on the tagging alone then there will be gaps,
particularly if those choices are made over large areas with various levels of infrastructure.
If the choice includes determinations of making at least one road connection from every city at some zoom level then you may have a 'better' map.
Similarly if the choice includes determining that little information is shown over some area of the map at some zoom level and so more detail can be resolved there you may have a 'better' map.

Each time these choices are made the complexity increases, if done manually then each time the map is remade there will be time spent on it.
If done by computation then there will be some computer time on it and occasionally errors will be encountered.

I have a road in one state at one level but when it crosses the state line it changes as that state regards it as a lower level .. and
the road does deteriorate quite noticeably! The tagging is correct but most maps show the road vanishing at one zoom level, you have to zoom in to see the poorer road.
The present rendering 'rules' don't resolve these issues as they are simple rules without too much complexity.
To get these rendering issues resolved will take some time, and more computer time.

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