Current tagging: the rooftop road has layer=1 and building=retail. I removed layer=0 as I believe it’s the default (JOSM warning). Yesterday I also added bridge=yes to the rooftop road, but I am not sure if I like it because there’s another bridge over a perpendicular highway just next to it.
Please advise if there is a more unambiguous way of tagging this situation.
Two other points. When I was looking for a shop via Apple Maps it routed via the rooftop road, which isn’t possible. Also, Organic Maps renders the road as if it passes through the building. I have been there physically since and know the layout so could correctly add other shops.
Combining bridge=yes with embankment=yes looks a suspect to me. I would generally expect one or the other.
Is it actually a building or a bridge=viaduct with shops under the arches?
The first example of that I can think of that are businesses under Deansgate Castlefield and under the nearby rail line.
I feel like treating the area as man_made=bridge and using separate building tags for the areas underneath would be a little more accurate than treating a viaduct itself as a single building but other might disagree on that.
As much as JOSM might complain about it I do slightly prefer to keep thelayer=0 in situations like this as it does indicate that it has been explicitly considered rather than just left at the default assumption by whoever traced it. I have mixed feelings about using the same layer for the road/rails with the bridge tag and the bridge itself, a more explicit rails>bridge>shops(&building) feels more accurate, but then if the man_made=bridge is the same bridge as the bridge tag on the road/rail then can you really say they’re separate layers?
I was thinking the same. Josm validation errors are generally to fix, its warnings only sometimes. They mean: “are you sure, have another look whether this is really what you wanted?” but the answer can be “yes”.
I somehow missed embankment=yes on the road even though I read about it on the wiki. It certainly should be this or bridge=yes. So my follow-up question is whether this is embankment? Is there a requirement that an embankment is filled? Because there’s a space under the highway (occupied by a couple of shops), but it’s also bricked up on both sides. Maybe it’s best if I put a note with a photo next time I am there and then ask?
I will re-add layer=0 then. Thanks for pointing it out.
For things like rooftop gardens, `location=roof` has been suggested in the past. I’m not sure the Simple Indoor Mapping or Simple 3D Building schemas have a solution for this.
A similar question was asked here, and they opted against the “layer” approach, I’m not sure if there a community consensus here though.
I’ve split the rooftop road into a part which is definitely an emankment and the part which I tagged as bridge. I went with bridge because it looks to me that it’s build like a bridge. You can see the arches on Mapbox imagery. It’s just that each arch is bricked up and has a door to a shop. I think this is a reasonable approximation of ground truth, but I am happy to take further direction.
I re-added the layer tag to shop and the building.
Below a photo of the place I took on Sunday. I’ve now added most of the venues all with layer=0. For the rooftop road I tagged part from Clue HQ as a bridge=yes and before it (right on the photo) as embankment=yes.
Interesting. I haven’t seen parabolic arches on a viaduct like that before. It makes sense, but for whatever reason I’ve only ever seen ones that look like circular arcs[1].
I’m still quite conflicted as to whether it’s a man_made=bridge or a building. It looks like it’s mostly meant to hold up the road and the arches have been filled as an afterthought which would lean it towards the bridge tagging, but it’s definitely an enclosed space with retail inside it which leans towards calling it a building. I almost want to suggest tagging it as a bridge and the individual shops as building:part=retail but using a building:part within a man_made feature just seems fundamentally wrong.
For what it’s worth there appear to be 120 occurrences of building=viaduct in OSM so maybe that’s the way to go.
Well, yes and no. I think it’s meant to indicate that a bridge is actually closed in underneath and used as a building. Double tagging as both a man_made=bridge and a building=* would also be possible but having two ‘primary’ key might annoy some mappers and QA tools.
I’ve understood that building=* follows original purpose, as with amenity=pub + building=church.
So building=viaduct or the equivalent two-fold tags seem right to me. (And it’s definitely a viaduct for me, not an embankment)
If we were to take inspiration from the law, there’d be nothing wrong with having a building within a building - a shop within a bridge (or could coin hereditament=* for the really picky; which I think would be silly).
Tagging levels and heights can render it all correctly in 3D, and in 2D it won’t matter.
I don’t know if this location may help with the multi-layer, road on embankment situation:
