sent from a phone
On 16. Jan 2018, at 18:13, Christian Müller <cmu...@gmx.de> wrote:
>> Gesendet: Dienstag, 16. Januar 2018 um 15:55 Uhr
>> Von: "Marc Gemis" <marc.ge...@gmail.com>
>> An: "Tag discussion, strategy and related tools" <tagging@openstreetmap.org>
>> Betreff: Re: [Tagging] Sidewalks and cycleways as tags vs as extra lines
>>
>> adding e.g. surface=paving_stones to the cycleway and
>> cycleway=paving_stones to the main road is tagging the same feature
>> twice, not ?
>
> Yes and no. You could deduct bits of information to complete the (tag) set
> of information on anyone of both objects using the other respectively.
you could see it as a cycleway object and a highway object which has
the information that it has a cycleway
Similar to atm=yes for a bank
>
> But the reasons chosen are (to some extent) arbitrary, e.g. you could model
> the kerb as a separate way and you will find that "one feature, one element"
> justifies such a decision as well.
+1, there aren’t “features” in reality, we only create them ;-)
Therefore the rule is satisfied if you split a road for example: each
part becomes a feature.
The only case where the rule is not satisfied is when you add the same
object explicitly twice, e.g. as node and as area, or 2 nodes with the
same tags for the same thing.
> One reason OSM models cycleways and sidewalks separately, is because it
> is easier to classify (i.e. match properties and find similarities to
> others) a road ensemble looking at its components.
+1, if it is detailed it makes it also much easier to understand and
maintain, because it is less abstract and geometrically resembles more
what you can see in the real world.
But there’s also an overhead, you have to model all the connections,
and somehow you can cross a road everywhere in reality, so there are
also negative aspects in this case of more detail (where it actually
leads to less quality for some usecases).
> There have been debates about whether to map lanes individually or not,
> a lane may be viewed as a single feature or just as a component of a
> road,
as it is both, it could be mapped in both ways, even at the same time.
Even three times: lane as line (similar to highway=*), lane as area
(similar to area:highway), lane as property of the highway ("how many
lanes has this piece of road").
>
> To come back to your original question, you would tag the same aspect
> of reality twice, but in two different models of reality:
+1, you would refer twice to the same thing, but you would not map it "twice".
Cheers,
Martin
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