[Tagging] site relations for city walls?

Martin Koppenhoefer dieterdreist at gmail.com
Wed Jul 15 08:20:14 UTC 2020


Am Mi., 15. Juli 2020 um 10:03 Uhr schrieb Lionel Giard <
lionel.giard at gmail.com>:

> In the parking example that i talk about, the multipolygon is not usable
> if i want to indicate the specificity of each part of the parking lot like
> capacity or capacity:disabled (as the tagging is global for every outer
> part). I like the site relation as it allows to also group the vending
> machine or the amenity=parking_entrance for underground parking (as a car
> park may have both underground + overground parkings). I find a site
> relation more practical in such cases and I never used it technically for
> malls with only overground parkings (but that was in the original proposal
> example i think ^^).
>


yes, the site relation is useful when you have something that can be
considered a "site" and you have objects like nodes and lines that are not
inside the area. In theory it could also be useful if you want to have
specific roles (e.g. this is the ticket office for this site, or like in
your example, these are the vending machines for this parking). Or this is
the parking for this supermarket (if it is not adjacent/part of the area, I
have an example around here).

IMHO, a city wall around a city, fragmented or not, is not suitable as a
"site", because it is not "compact" (not sure about the right term).
Similarly, a university which is split across several, distant (relatively,
e.g. hundreds of meters or some kilometers apart) places, is not a "site",
it is rather several sites, and to draw them together, we usually employ
"tags". If you do not like to rely only on tags, a different kind of
relation would seem more appropriate. In the end it depends on scale what
is distant and what is close.



>
> My use case was more about the underground parking where I grouped all the
> parking_entrance (both pedestrian and for vehicle) with a "site=parking"
> relation. One example is this one :
> https://www.openstreetmap.org/relation/8425228#map=18/50.66911/4.61226
> (there are one vehicle entrance, one vehicle exit, multiple pedestrian
> entrance/exit and few vending machines for it). *Do you have a better way
> of tagging this ? ^^*
>


you could have the parking as an underground area and the entrances part of
the perimeter, and you would not need a relation. I agree though that the
site relation seems appropriate for this case (underground structures are
generally a field of problems, e.g. because they are hard to survey and
they are confusing people because the rendering is often not appropriate.

Cheers
Martin
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