[Routing] Ordinary roads as roundabouts and the contrary

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[Routing] Ordinary roads as roundabouts and the contrary

Sandor Seres

First of all, any suggestion/advice could help me to (further) improve my data-preparation-tools related to the OSM roads/streets data.

At the same time the issue may be of certain interest for developers working with rooting/navigation systems.

In the preparation, while removing millions of redundant nodes, vectors, poly-lines in the source data (related to the 5 road and 2 street classes) we meet a special roundabout issue. Namely, there are over 140K road objects (ordinary ways/not tagged as roundabouts) that perfectly match the (6 statistical) parameters of the safe roundabouts in the same class. This number includes the turning circles as well. Testing on a large sample (from all over the World, a tedious and difficult job) still shows that most of the object are roundabouts but missing the proper tag. So, my dilemma/question is – what is worse (more dangerous) in a routing/navigation system:

1. Having large number of real world roundabouts as ordinary roads (road segments) in the network, or

2. Having some ordinary circular (usually one-direction) roads as roundabouts in the network.

Of course, for a simple rendering the issue is irrelevant but for the GIS systems and especially for the turn-by-turn car navigation might be essential.

The mentioned parameters detected on the set of safe roundabouts I use for the georec (geometry recognition), error detection and reparation. In my case, the small circular objects have essential role in the data-generalisation and vector-scale levels.

Finally, it is worth noting that even in case of roundabout tagged ways in many cases (thousands) the roundabout is “unsafe” (missing segments, mixing road types, more than one loop, self-crossings, zigzag edges and so on) and a robust automatic recognition and reconstruction is needed. The old fashion “contact the mapper” does not work at least for two reasons: one, there are too many of the cases and two, the cases are there in years and the mappers are probably not active anymore. For illustration let me take some examples where the rendering, the visual impression is correct but there is no even a segment of a roundabout (see e.g. here http://osm.org/go/T87HKcHrN-- ). One model to reconstruct the correct objects is to smash the whole shape into none-crossing vectors, so connect them into simple poly-lines, connect these (if possible) into a circular/polygonal line as roundabout (using the mentioned parameters) and the remaining poly-lines move to the set of corresponding ordinary road segments.

Regards, Sandor.

 


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Re: [Routing] Ordinary roads as roundabouts and the contrary

dieterdreist


sent from a phone

> On 20 Feb 2017, at 21:37, Sandor Seres <[hidden email]> wrote:
>
> mixing road types


different road types in the same roundabout are not necessarily "wrong". E.g. roundabouts are often added to existing crossroads of major and minor roads and with typical dual carriageways (near the crossing) there remain less important sections of the roundabout (in some cases almost nobody uses them) between the links for the "major road".


cheers,
Martin
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