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#1 2022-05-12 13:06:03

Ukundji
Member
Registered: 2015-08-12
Posts: 39

Mapped Objects that no longer exist - is the data lost?

What happens with objects which were correctly mapped in OSM, but disappeared completely in the meantime?
As far as I understand the guidelines of OSM these objects should be - if no remains can be seen at the ground today - deleted.

OSM is not Open Historical Map. I agree with this, but wonder what happens with all the very valueable data about buildings, streets, residential areas, villages which had been mapped in OSM. Big changes happen because of numerous reasons like city or industrial development, natural desasters, wars, etc. I run to a number of cases in Ethiopa and China recently comparing older and newer imagery. But I do not dare to delete complete villages or streets with houses. I want to ask if this data (may be with an end=xx.xx.xxxx tag) can be saved and/or transfered to projects like Open Historical Map. I think this would be of great value and importance.

OSM is a project which has existed for a number of years and hopefully will still exist in one shape or the other in 2050. It would be great if we will be able to check in 2050 (based on OSM data) how a certain area looked like in 2010, 2020 or 2030.

What is your opinion?
Have there been in-depth discussions about this "historical dimension" of OSM?
Are there any solutions or ideas for solutions?

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#2 2022-05-12 14:13:28

Jillis E
Member
From: Amersfoort
Registered: 2019-06-08
Posts: 428
Website

Re: Mapped Objects that no longer exist - is the data lost?

Hi Ukundji, you can relax as no data is lost in the OpenStreetMap database because it keeps versions of all objects.
Even if you delete an object, that becomes a new (and last) version of it and you can go back to the previous version.
Each object (node/way/relation) has a history that you can display in osm.org, e.g. https://www.openstreetmap.org/way/78558269/history (the Dutch cadastral center smile a mile from my place)

And because of this, we can already see how the data evolved and grew in the past 17+ years.

I think this also answers your questions. And you really can delete houses and roads that don't exist anymore, go ahead.

Last edited by Jillis E (2022-05-12 14:21:49)

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#3 2022-05-12 14:49:06

Ukundji
Member
Registered: 2015-08-12
Posts: 39

Re: Mapped Objects that no longer exist - is the data lost?

Hi Jilles!

Thank you very much for your very helpful answer.
I know that we can see the history of the mapping of a certain object in OSM like the cathedal you posted.

But what if I have (for instance) an industral area or a new neighbourhood with skyscrapers on the today`s map and a village mapped in the same area ten years ago? The industrial area would certainly not have the same shape and way No. in OSM.

If no data is lost indeed, my additional questions are:
How can I find out about the existance and way/node numbers of deleted objects?
How (which which tools) can I access the deleted data?
How can I search for objects which once existed and/or get the information that such deleted OSM objects exist in a certain area?
Is there any tag which would allow me to differentiate between objects which were deleted because they were mapped by any kind of fault and objects which were deleted because they do not exist any longer?

I think that the last question is of great importance. OSM vandalism or low quality mapping which has to be deleted because it is simply wrong, not reflecting anything which really existed (at least not in the way it was mapped) is one thing. But I am talking about the millions of high quality OSM nodes and ways which have to be deleted because the objects itself do not exist an longer.

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#4 2022-05-12 21:40:16

maro21
Member
From: Wrocław
Registered: 2018-03-06
Posts: 1,010

Re: Mapped Objects that no longer exist - is the data lost?

You can display data, from any date, but that data will only represent map data from that time, not reality. Currently, any arbitrary piece of map represents the state of reality at some time - one piece is yesterday, another is 2015. So even going back to data from any date, the map won't represent what the area looked like at that time, but what the map looked like.

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#5 2022-05-13 00:49:16

SomeoneElse
Member
Registered: 2010-10-13
Posts: 1,578

Re: Mapped Objects that no longer exist - is the data lost?

You can use Overpass to see what something looked in in OSM previously.  For example, that tower looked like this a few years ago: https://overpass-turbo.eu/s/1ipS .

Last edited by SomeoneElse (2022-05-13 00:49:28)

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#6 2022-05-13 07:39:51

Ukundji
Member
Registered: 2015-08-12
Posts: 39

Re: Mapped Objects that no longer exist - is the data lost?

maro21 wrote:

You can display data, from any date, but that data will only represent map data from that time, not reality. Currently, any arbitrary piece of map represents the state of reality at some time - one piece is yesterday, another is 2015. So even going back to data from any date, the map won't represent what the area looked like at that time, but what the map looked like.

Well, I am afraid that I might have not been clear regarding my point. Of course I know that the state of the OSM map in 2015 is something else then the reality in 2015 (even if the mapping was very good). My point is how to access (search for, find, display) data for correct older mapping of structures which once existed in OSM (and hopefully as well in the reality).

If you say: I can display OSM data from any date: How would I do this? Let`s say I have a certain area and want to display the OSM data of January 31, 2015. Which tools would I use?

And this only makes sense if I expect that former (correct) mapping of structures which no longer exist might have been done in that area. Can I as well search for (as examples) deleted residential areas or deleted buildings in a bigger region?

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#7 2022-05-13 07:43:03

Ukundji
Member
Registered: 2015-08-12
Posts: 39

Re: Mapped Objects that no longer exist - is the data lost?

SomeoneElse wrote:

You can use Overpass to see what something looked in in OSM previously.  For example, that tower looked like this a few years ago: https://overpass-turbo.eu/s/1ipS .

Thank you! That`s very helpful indeed!
But again it does only work if I already know the OSM ID for the way or node, doesn`t it?
Can I use Overpass as well to see how the map looked like in that area in 2013 or even better to display structures which were deleted between 2013 and 2022?

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#8 2022-05-13 15:01:23

SomeoneElse
Member
Registered: 2010-10-13
Posts: 1,578

Re: Mapped Objects that no longer exist - is the data lost?

Ukundji wrote:

But again it does only work if I already know the OSM ID for the way or node, doesn`t it?  Can I use Overpass as well to see how the map looked like in that area in 2013 ...

You can do lots of things with Overpass.  https://overpass-turbo.eu/s/1iqK shows _all_ ways in the area at that time, and you can replace way with "node" or "relation" to look for those, or "nwr" to look for all 3.

Ukundji wrote:

... or even better to display structures which were deleted between 2013 and 2022?

Possibly - there are lots of examples at https://wiki.openstreetmap.org/wiki/Ove … by_Example .

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#9 2022-05-15 20:46:31

Ukundji
Member
Registered: 2015-08-12
Posts: 39

Re: Mapped Objects that no longer exist - is the data lost?

Thank you #SomeoneElse!

I see and understand that an advanced use of overpass is able to answer most of my questions. That`s great!
Thank you for all help and answers. This is a great and very active community!

P.S.: I still would prefer to have information why a certain structure was deleted. If I look at this wish based on the OSM basic rule "map what you see at the ground" deliting simply means: "No, this structure does not exist here". Most of the OSM mappers might not know why it does not exist (any more) or since when it is gone. And if one really knos it might be good pratice to add a notice like "torn down/razed/detroyed in 2019" to the changeset.

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