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Why discourage use of layers?

There are also situations where layers are still needed. --Dieterdreist 17:07, 19 September 2011 (BST)

There sure are. But in many cases the building is right next, above and bellow the road so you should assign the road layers -1,0, and 1. The next best you could do is assign the road a level of the building but this makes rarely sense. RicoZ (talk) 11:27, 23 January 2014 (UTC)

I reject this proposal

Please use tag covered only for covered ways. I think, ways inside of buildings should be describe as: tunnel=passage

See Proposed features/building passage and Key:tunnel, instead of tunnel=passage it seems better to use tunnel=building_passage (11 992 times used Jan 2014).
Emvee (talk) 10:50, 18 January 2014 (UTC)

Tunnel or Covered for building_passage?

The way the page is written currently, it sometimes seems to recommend using covered=building_passage rather than tunnel=building_passage, yet 1) tunnel is much more widely used than covered (37956 vs. 374), and 2) the related proposal only seems to mention the tunnel version. If there's an actual purpose behind this, reply, otherwise I'll assume it's just poor phrasing and try to fix it.

It is indeed by purpose, both variants have good use in different situations. RicoZ (talk) 21:52, 27 May 2015 (UTC)
For what it's worth, I don't think using the same word "building_passage" for two different things is the best possible solution, it invites confusion. But improving the explanation could also help, e.g. replacing the vague "some connection to the building". And why is the example image for tunnel=building_passage shown here? --Tordanik 22:53, 27 May 2015 (UTC)
RicoZ, can you clarify how they have different meanings or usages? Neuhausr (talk) 18:01, 28 May 2015 (UTC)
The idea (which I did not invent) probably was to have covered=building_passage for hoot or highways that go through the building with shops and entrances on the similar to covered=arcade/colonade, while tunnel=building_passage would be for ways (also water & railways) that only pass through the building without the entrances etc. Seeing that at least on of the images at tunnel=building_passage does not fit that I am not sure how many people did it that way. RicoZ (talk) 12:38, 29 May 2015 (UTC)
I think I see what that's getting at, although I'm not sure how significant that difference is. You say you did not invent covered=building_passage--do you know where this idea came from? Because it's not in the linked proposal, and it appears you added it to this page: Neuhausr (talk) 15:21, 29 May 2015 (UTC)
The proposal does explicitly mention covered=building_passage in the summary box but not elsewhere. Not sure anymore where I found the other information, it was at the time when I revamped layer=* that I stumbled upon covered and tried to make the two pages consistent as good as I could. Regarding "layer" and "covered" it makes technically good sense to distinguish the case of an isolated tunnel through a building (which is typically surrounded by the building and thus has the same layer as the building) and that of a shopping passage like tunnel where the way could use "level" to describe vertical relation with ways in the building. RicoZ (talk) 10:06, 30 May 2015 (UTC)
Found it here: . It is not quite consistent between the proposal and discussion page so I have done it by analogy.RicoZ (talk) 12:57, 30 May 2015 (UTC)
Well, by this logic the proposal also introduced tunnel=arcade, which is also mentioned no one else. But to me, only the 4 tags in the "Tagging" section of the proposal were introduced by it.
So with the background I know of, I would consider the tag never actually introduced, and the documentation incorrect, especially as I don't really see a strict distinction. Surely a tunnel=building_passage can also have doors into the building along its sides, for example. --Tordanik 17:00, 30 May 2015 (UTC)
I think a tunnel=arcade would actually make good sense logically, have seen some tunnels in Italy that would be very well served with this tag. However it may be that too many users would associate an arcade with a shopping arcade so it might cause too much confusion.
Tunnels can have doors but (a) are not expected to have doors other than emergency exits, (b) the purpose of a tunnel is to get through some obstacle and not have doors - unlike for example a footway/highway in a shopping area. It would not be consistent to decide between either "tunnel" or "covered" for very similar ways just depending whether there are arches on one side or a wall or shops. RicoZ (talk) 21:25, 30 May 2015 (UTC)
For me the proposal also only added the 4 tags in the "Tagging" section. The talk "tunnel vs. covered" is about arcades/colonnades. The distinction is too thin: there not much space between a tunnel and indoor tagging. Covered=building_passage should and will be removed from the article.--Jojo4u (talk) 12:20, 31 May 2015 (UTC)


I do not agree with the latest few edits regarding that. Specifically

"layer=* is probably inappropriate for most cases of covered=building_passage or tunnel=building_passage - except where there is the requirement to differentiate several layers of tunnel=building_passage. Several layers of covered=building_passage may be sometimes more appropriately differentiated with level=*."

is imho a nobrainer. What kind of layer do you want to apply to a way passing through a house? Going through means the house is by definition above, to the side of and in most cases also bellow the way - assigning a layer to either of those is wrong.

I also do not agree with the sentence "when the layering is clear and unambiguous, layer=* should be used instead of covered=* (for example?)". The Key:layer page says

"With some exceptions, layer=* on ways should be used only in combination with one of tunnel=*, bridge=*, highway=steps, highway=elevator, covered=* or indoor=yes. For areas, it could be used in combination with tags such as man_made=bridge, building=* and similar."

This is an important principle because it allows much easier checking of layer usage: it is very easy to spot missing tunnels, bridges or "runaway" layer tags that were placed somewhere accidentally. Relaxing this rule causes complications without real benefit.

Also please avoid things like "{{tag|tunnel}} or [[Tag:tunnel%3Dbuilding_passage|building passage]]" - the second link probably redirects to the first and the syntax obscures that it is a tag value. RicoZ (talk) 10:02, 3 June 2015 (UTC)

You seem to have a clearer grasp on what should be in the layer reference there, please edit it to make clear and correct. I changed the link you objected to. Cheers Neuhausr (talk) 13:44, 3 June 2015 (UTC)

Finished bringing up to date

I brought the article up to date incoperating the Proposed_features/building_passage and location=* from Proposed_features/PipelineExtension. Any comments?--Jojo4u (talk) 21:24, 4 June 2015 (UTC)

I am irritated that your and Neuhausr edits have very similar timing and scope - can you explain what the connection is? Nobody else touched this page for years - where does this sudden surge of interest come from? RicoZ (talk) 15:11, 7 June 2015 (UTC)
I can assure you I don't know Neuhausr and have not communicated with him directly. I came across your dispute with covered/tunnel=bulding_passage and saw the page covered=* in bad shape. Edits are leading to more edits because of page subscriptions.--Jojo4u (talk) 07:30, 8 June 2015 (UTC)

location=underground vs. covered=*

Covered should be used: "to denote an area such as an underground parking lot, a covered reservoir/cistern or even such things as an aquarium (e.g., Kelly Tarlton's, Auckland, NZ), when the covering is not a man-made structure that would allow layer differentiation." and "However, underground excavations such as parking lots and reservoirs are appropriate, as noted above."

How is "underground excavations" when "when the covering is not a man-made structure" different from location=underground?--Jojo4u (talk) 21:28, 4 June 2015 (UTC)

Good question. Personally, I would consider using covered for an underground structure (such as an underground parking lot) incorrect. --Tordanik 12:45, 5 June 2015 (UTC)
The parking lot depends on a lot of other factors: if it is part of a bigger building structure various indoor mapping tags might be better. Location would be preferred when it is really under "ground", separated by a significant layer of "earth" from anything above it - probably rare for parking lots. If it is a bellow ground parking lot with a concrete roof and (possibly) flowers planted on top of it "covered" would be better. RicoZ (talk) 08:16, 6 June 2015 (UTC)

Rationale: "when a building has a way passing through it"

The Rationale section currently uses the example of a way passing through a building. However, that would be the domain of tunnel=building_passage, so it isn't a good fit here. I can't think of a good example to replace it, though. --Tordanik 11:45, 31 July 2015 (UTC)

Indeed, and my impression is that whoever created the original proposal used tunnel=building_passage instead covered=building_passage mainly for the reason to get quick support for rendering and tools. Does not fit really well to tunnel either as it is the only variant of tunnel which is expected to not have a layer tag in most cases.
As of the example, possibly covered=arcade when it is part of a building would fit there? Like a building passage it can't be (in most cases) assigned a layer different to that of the building. RicoZ (talk) 10:42, 1 August 2015 (UTC)
I tried to improve.--Jojo4u (talk) 11:46, 1 August 2015 (UTC)

What to do with building=roof?

Currently OSM-carto does not show that a highway=* under a building=roof + layer=1 is covered without tagging covered=* on the highway. Example location.

Currently layer=* says "For areas, it could be used in combination with tags such as man_made=bridge, building=* and similar." my conclusion: layer=1 is enough.

But covered=* says "For a highway, railway, pedestrian way or waterway that is (even partially) covered by a building or other structure and does not fit the definition of a tunnel=* (including tunnel=building_passage)." my conclusion: covered=yes is needed.

building=roof was only recently changed towards covered=yes.

So the wiki disagrees.

I opened a Github ticket to get a clarification on this. Answer was "Probably yes" but that it should be discussed in wiki/mailing list.

Two questions:

  1. Viewing only from a data standpoint: Do you think that building=roof+layer=1 without covered=* on the highway below is recommended tagging?
  2. Should it be tagged nontheless since the renderers struggle to support the layer?

--Jojo4u (talk) 20:38, 3 October 2015 (UTC)

Regarding the quote from the wiki layer page saying "For areas, it could be used in combination with tags such as man_made=bridge, building=* and similar" - it is an overview of possible uses which ought to be defined (and implemented in software) somewhere else. Some time ago I included "building" in the list to relax the rules for indoor mapping. It should not be interpreted so that every use of building and layer is correct and supported.
Your intended use of building=roof looks legitimate so it could be defined to work as you think. However there are other reasons why it may be better to not support this - see Talk:Key:layer#What_to_do_with_building.3Droof.3F. RicoZ (talk) 22:52, 3 October 2015 (UTC)
More thoughts.. conceptually I think building=roof should be considered identical to any other building. In most cases there are up to 2 walls or several pillars so it is not like the roof would be free hanging in the sky. Hence ways going through such buildings should use exactly the same mapping technique like ways going through any other building: no layer (unless required for other reasons), shared nodes with building=roof and either of covered=yes/arcade or tunnel=building_passage. RicoZ (talk) 10:25, 4 October 2015 (UTC)
In principle, I agree with treating building=roof like other buildings. However, the logical conclusion is to treat roads below the building=roof as passing below the building. As such, covered=yes, and not tunnel=building_passage, would be appropriate. --Tordanik 11:44, 4 October 2015 (UTC)
How is a way passing through a building bellow it? This is contrary to what the documentation of covered=yes says (it is somewhat hidden in the rationale and iirc was also in the original proposal). I have no real preference between covered=yes or tunnel=building_passage, both may be useful in some circumstances. RicoZ (talk) 12:13, 4 October 2015 (UTC)
I also see the way passing through the building=roof now since there up to 2 walls. The choice of tunnel/covered depends on open at least on one side. In theory a building=roof could have exactly two walls which form a tunnel.--Jojo4u (talk) 12:32, 4 October 2015 (UTC)
If the building (or building part part) only starts above the road, as is usually the case with building=roof, then the road passes under it, not through it. The 2 walls confuse the matter a bit, but if we want to represent the building in 3D, these walls are independent building parts anyway.
Would you really consider the situation in the example image a "tunnel"? --Tordanik 13:17, 7 October 2015 (UTC)
WRT example picture - I don't think it should be tagged as tunnel. If I read the old forum discussions correctly it seems that in the ancient times tunnel=building_passage was chosen as "tunnel" (instead eg covered=building_passage) to gain quick rendering support, not an optimal choice from today's POV.
The example picture could be interpreted so that the roof is a part/extension of the building. In this interpretation the building and roof would have no layer and the ways would be marked as covered=*.
The interpretation that you have in mind - one building=* + layer=0 and an adjoined building=roof+layer=1 has no advantage that I could see. The roof has pillars which connect the roof with the ways/ground so unless you map the pillars separately it would occupy the same layer like the way. On the left side of the building you see entry gates, car service or similar where cars may drive in or perhaps even through. They look very different then the filling station lanes and serve a different purpose - but saying the difference is that one is building=* and the other building=roof+layer=1 would be pretty crude. It could be improved by giving the ways some functional attributes (filling-station-aisle) and add 3D to the buildings.
Having layer=1 on a building=roof could still make sense if there is a large roof spanning several other features or even small buildings. RicoZ (talk) 23:14, 7 October 2015 (UTC)
I made up the following: building=roof includes support structure, not only the roof. So a way goes through the whole structure. Support structure should one day be mapped like Key:bridge:support, e.g. building:support. If a roof is attached to some other building without own support the whole building outline should encompass the roof. Either way, the highway below should be tagged with covered=*.--Jojo4u (talk) 14:33, 29 September 2016 (UTC)
A different tagging between building:part=roof (covered=yes for highway below) and building=roof (layer=1 for roof) would make it just more difficult. In true OSM-tradition there might be a recommended way and way "some mappers" are doing it. The page text reflects this pretty well. My natural feeling is to use layer=1 and it should not do much harm.--Jojo4u (talk) 16:14, 29 September 2016 (UTC)

Your edits over at building=roof are a bit premature, but it raised one question: What to do with buildings which are essentially like man_made=bridge: example, way 23738006. Are highways under a man_made=bridge covered=* as well? But you can't connect the nodes here, there are no connections, or is it?--Jojo4u (talk) 12:40, 4 October 2015 (UTC)

You have raised some important, points. I have also clarified building=bridge, not sure if that is what is in the picture but does not hurt anyway. Some thoughts are attached to the github ticket which you have opened. You have raised some important, points. I think the tunnel=buidling_passage would be a rare exception for something that people would normally tag with building=roof.
The motivation for my edits is to have a technically more consistent tagging with less exceptions - in principle abolishing the idea that a building could be made to float midair by using layer. RicoZ (talk) 13:27, 4 October 2015 (UTC)
I think covered=* should only be used when the highway and the e.g. building share nodes. This rules out the example and man_made=bridge.--Jojo4u (talk) 14:30, 4 October 2015 (UTC)
I think we are meaning the same - things running under a man_made=bridge clearly don't need covered. Not exactly sure which example of man_made=bridge you mean. For building=bridge I have proposed to add a man_made=bridge to the outline (so that the object would "inherit" all useful properties of bridges) and that ways inside the building=bridge might be mapped with covered. RicoZ (talk) 15:00, 4 October 2015 (UTC)
I don't think building=bridge should be double-tagged with man_made=bridge. Two main-tags are against our rules.--Jojo4u (talk) 16:34, 4 October 2015 (UTC)
We could declare that building=bridge inherits the properties of man_made=bridge. However this would be just a special case of a more general case: there is a man_made=bridge and and one or more buildings fully or partially overlapping with/built on top of the bridge. In the general case the case it seams clear - we have an outline man_made=bridge + one or more outlines building=*. In simple cases those elements could be "grouped together" by having same layer + location=bridge attached to the buildings, for more complex cases a relation could be used.
The simple case could be handled as a special case as mentioned above with building=bridge inheriting all the properties of man_made=bridge - or as degenerate of the more general case. Is it worth it to declare and handle the special case? man_made=bridge+building=* would also allow to specify building types easier. RicoZ (talk) 21:18, 4 October 2015 (UTC)
Btw here is the bridge in the example picture of building=bridge: - it is actually an example of the more complicated case where building=bridge is not used. I would probably map some details differently but have not been there for a very long time. RicoZ (talk) 22:41, 4 October 2015 (UTC)
I replaced the image with an image which is really describing a building which doubles as a bridge. And is tagged as such: --Jojo4u (talk) 11:42, 29 September 2016 (UTC)
I will modify the building=bridge page, let's continue discussing over there. --Jojo4u (talk) 11:44, 29 September 2016 (UTC)