It is well established that buildings that are gone and unlikely to be mapped by accident should not be mapped (use OHM for that)
It is well established that buildings that are gone and likely to be mapped by accident can be mapped with say demolished:building=destroyed:building=razed:building=
But how can we distinguish cases where building is gone and all traces are gone and case where building is torn down but ruins remain?
Maybe if these are used then it express case of building and any ruins being gone? At least typically? And should not be used if ruins are present?
And if ruins are present then ruins:building=yes or similar should be used?
Or maybe demolished:building=destroyed:building=razed:building= are not specifying whether ruins are present and ideally we would have more clear value specifying âno ruins or traces hereâ?
Or maybe âare ruins hereâ is not important and worth caring about?
I have no clear answers or perspectives to these questions. My initial take is that it might often be very difficult to differentiate clearly between simply abandoned buildings, buildings that are in âruinsâ, and buildings undergoing demolition (for years, or at least for a very long time). Perhaps @vectorial8192 and you could hash out something together, as you seem to be interested in similar cases (so Iâm pinging them to this thread too with the @ marker)!
There is definitely a need for a way to tag buildings that are beyond abandoned (i.e. they are not actively being demolished but slowly disintegrating due to neglect) but do not have historic value so donât fit historic=ruins. I guess many ruins tagged with the later are so because thatâs what turns up when you type âruinâ in iD even though they donât have historic value. It would be more correct to tag these ruins with ruined:building=* Maybe the border line between abandoned and ruined could be that abandoned buildings still have a roof (though it may be leaking) while ruined buildings have no roof left but may still have walls standing.
note that âhistoric=ruins is for objects with historic value onlyâ may be idea that is not generally supported
How would we be quantifying historic value? IMHO it depends on the context / question that you have, whether a specific relict can be of value or worthless.
Yeah, it seems quite some OSM mappers may think building demolition is âalmost alwaysâ a quick process (e.g. short building quick job, tall building use âcontrolled explosionâ demolition) so the intermediary statuses can be safely ignored. Well, consider Hong Kong with its insane density, but also a need to rebuild somewhat tall buildings. âControlled explosionâ demolition is basically forbidden, so construction companies had to tear down the building, one level at the time, which is obviously slow.
Which led me to the original âbuilding under demolitionâ question.
Anyways, itâs a good idea to list out what we have right now regarding building tagging (or at least what I think we may/should have).
Every building âstarts offâ as some sort of unused land. Then, as construction begins, someone would add landuse=construction and building=construciton, that kind of stuff. When the building finishes, someone else retags building=yes, or more specific values from construction=???. Simple stuff.
Now if the building is being continuously maintained, we donât have to worry about it.
The problem is when buildings are no longer continuously maintained, and thatâs what brings us here. It seems to me those destroyed/razed/demolished tagging is quite subjective since they also describe the method with which the building is unexisted, and opens up attacks from mappers to dispute the unexistence method, therefore the âvalidityâ/âaccuracyâ of such tags.
Iâm gonna think about this for a while first and then continue typing.
Abandoned: building is effectively âunclaimedâ. Depending on the state of the building, it may be dangerous to get inside, but trespassers are unlikely to be sued.
Disused: similar to âabandonedâ, but building is still âclaimedâ (e.g. security guards standing by at its entrances); as such, trespassers are gonna get sued. I donât know why this situation exists (especially in Hong Kong with insane land demand), but some examples from Hong Kong:
Ruined: an extension of âabandonedâ. Building is obviously damaged (the method does not matter; could be from wars/conflicts, could be ânatural reclamationâ, etc), and itâs unlikely to be repaired any time soon.
Avoid creating a damaged=yes tag:
Some buildings can appear damaged due to negligent maintenance but are otherwise perfectly usable and structurally sound
It is subjective what it means by âdamagedâ
Best correctness would require referencing the original blueprints, but thatâs probably impossible
âUnder Demolitionâ: an extension of âdisusedâ. Someone has to claim the building first before deconstructing it. Thereâs usually a construction area alongside the building. I personally use building=construction + construction=demolition.
âGoneâ: building is gone from IRL observation:
Method of unexistence does not matter (eg demolished orderly, destroyed by pure chance, razed by bulldozers, etc)
Could this be a subtag?
If still seen from satellite imagery, add building=demolished / demolished:building=yes (?)
One problem with satellite imagery: a provider may show âgoneâ while another provider may show âstill exists/under demolitionâ. Perhaps thatâs the source of rage/confusion around âremapping gone featuresâ.
definitely the second one, building=demolished / building=collapsed etc are nasty trap for data consumers
seems likely, but I would avoid making it part of definition as in at least some cases it will be different (for example, building may be guarded/unguarded for different reasons)
I recently went through the âlong tailâ of building values somewhat local to me and classified the ones that are either ânot buildingsâ or ânot really buildingsâ. See âalmost buildingsâ and below here.
I also fixed lots of obvious typos to building types where it was obvious what the original mapper had meant.i
I think thatâs a really neat template for classification! Thanks!
The only nitpick I have is that although âruinedâ is often an extension of âabandonedâ, and âunder demolitionâ often an extension of âdisusedâ (as you wrote), these arenât strict inheritances. Abandoned buildings can be re-acquired for demolition, and disused buildings can also turn into ruins. Or put more precisely, disused buildings can often be abandoned, and then demolished or ruined.
You write that ruined buildings have to exhibit obvious damage (regardless of its etiology) but that tagging the damage isnât reasonable because âdamageâ is subjective. Furthermore you point out that some cosmetically damaged buildings still maintain structural integrity.
I agree on both points, and I think this distinction could be used for demarcating demolition too! The way I understand the process is that before a building is demolished, it is usually vacated and stripped of valuable and easily removed features. Like furniture, electric wiring, and even many non-load-bearing structuresâincluding inner walls or even the facade or outer cladding. During this (perhaps lengthy) time, Iâd think, the building isnât âdemolishedâ, but merely âdisusedâ. The reason being precisely that this equates perfectly to âdamageâ any âabandonedâ of âdisusedâ building might have.
Actual demolitionâas I understand the word and processâstarts from the time load-bearing structures are being intentionally destroyed to the point when the building is reduced to a heap of rubble (no matter how large[1]). The timeframe of this process varies massively. In explosive demolition, this phase lasts mere seconds. Smaller buildings can be bulldozed in days, and even multi-story reinforced-concrete buildings can be jackhammered to a pile of rubble in a few weeks. Thank you for noting that there really exist some buildings where this process takes multiple months to a year!
As @Mateusz_Konieczny noted, this is precisely the rationale expressed in the Wiki on the demolished: prefix.
Now if the building is being continuously maintained, we donât have to worry about it.
The problem is when buildings are no longer continuously maintained, and thatâs what brings us here.
as your Hong Kong example illustrates, it is not simple as that. Buildings also get rebuilt if their operation is less economically beneficial than rebuilding something different (in terms of quantity, energy consumption, spatial structure etc.)
Abandoned: building is effectively âunclaimedâ. Depending on the state of the building, it may be dangerous to get inside, but trespassers are unlikely to be sued.
Disused: similar to âabandonedâ, but building is still âclaimedâ (e.g. security guards standing by at its entrances); as such, trespassers are gonna get sued.
I think it is improbable to find âunclaimedâ buildings, every building on private land is part of the ground it stands on, which has registered owners (in most parts of the world I guess), there might be owners that are not currently interested in their property (e.g. they have different properties, are old and nobody from their family is interested, are far away, in hospital or in prison, etc.), but it is not a criterion I have heard before in the osm context, the difference between abandoned and disused which we typically apply in OpenStreetMap is about the state of maintenance, disused means good usable state requiring at most minor repairs, while abandoned means more serious damage while probably still recoverable (it is still there but looks somehow broken and deteriorated)
Buildings also get rebuilt if their operation is less economically beneficial than rebuilding something different (in terms of quantity, energy consumption, spatial structure etc.)
I have no idea which example you are talking about, and therefore do not understand what you are saying. If you are trying to refer to this Way: âȘPublic Housing Development at Sui Fai Factory Estate⏠(âȘ237758277âŹ) | OpenStreetMap , then I must tell you this is a government action on a government property, as part of a (long time?) political agenda to build more housing. It has nothing to do with being economical or not. In fact, one may argue this rebuilding action is uneconomical when the fact was that there were still some commercial businesses inside that Factory Estate before the rebuilding.
Re unclaimed/recoverable buildings, I can see a problem.
Consider a building which is essentially âleft to rotâ, so nature has decided to eg grow vines around the building. Even with this, the building is still standing. Would this be considered âneed minor repairsâ?
Would this be disused or abandoned? I would tend to tag this as abandoned: they do not have security guards there, and have made no attempts to repair it, so it is essentially âunclaimedâ. Therefore, abandoned.
Above examples of disused are cases where the property owner cares little, but still cares, so they install some security guards at those property while still letting those buildings ârotâ. Thatâs significant because those guards are on payrolls. Therefore, disused.