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?
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 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.
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.
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?
Thank you! Thats very helpful indeed! But again it does only work if I already know the OSM ID for the way or node, doesnt 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?
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.
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.
Based on the above I was able to find an old deleted way using overpass turbo:
But that’s just fining the state of the map on a particular day.
But imagine I don’t know when the object was deleted, or if it was ever where.
Is there a way to search a bounding box for all deleted objects within a date range?
Using past data should be done knowing that it is not meant to be used outside of maintenance, undeletion and similar. Elements can be deleted because:
they never existed and mapping them was mistake
deleted by mistake
deleted and then replaced with better geometry/tags
imported with wrong license
it stopped existing in real world.
So using that data should be used with a big grain of salt. In my experience as a mapper, deleting objects because they stopped existing is rare.
Enforcing comments or something else to see the reason of deletion would be an interesting solution. Maybe if the editor gave you this list I made for each deleted element it detected in your changeset.
For these particular cases a simple binary chop can work quite well. Pivot on say 2017, roughly between when ODbL came in and the present; rerun the query in the half of the time period where the object disappeared. Usually it’s possible to reduce the time interval, and once you have the object id there are faster ways to follow-up.
In principle this can be done with Overpass queries direct BUT a) they are complex and b) often run into resource problems.
In this case I’m interested why a given way is not in OSM now, and potentially opening a conversation with the mappers working in the area. The object in question absolutely exists on the ground, but maybe there’s something I don’t know.
Completely agree here with @SomeoneElse, I regularly run Overpass queries with a global date constraint, but you must constrain by tags and a suitable bounding box, or if retrieving everything use a small bounding box.
If you really need to search a big area, consider retrieving the data in CSV formet. In my experience this reduces some of the server overhead.
I was interested in the trail connection at lat=37.99207&lon=-122.50943 , from the end of Mountain View Avenue in Marin County California. It physically exists but seems never to have been mapped despite extensive local mapping efforts.
I ended up with the Overpass Turbo query of:
Using a bounding box of only 40x30 meters or so.
Unlike with the non-turbo Overpass this did work without running out of memory, but does not show all potential past and deleted edits in the bounding box.