Proposed features/4th Dimension/Archive

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4th Dimension
Status: Draft (under way)
Proposed by: peter.doerrie
Tagging: *=*
Applies to: Annotation
Definition: Scheme to tag the time relevant aspects of features
Rendered as:  ?
Drafted on: 2009-03-24


I propose to develop a tagging scheme to represent time-relevant informations of features. This could include existing tags (like openening_hours) but will also feature new tags, for example for construction/destruction dates.


OSM is in some parts of the world a very detailed image of what features exist at that point at the moment. This is fine and enough for the normal use of a map (which is orientation in space), but there is more potential. Every time a street changes its course, a sandbank changes its position or a house gets demolished this feature will be deleted by the next mapper passing that area. Of course it is still somewhere in the Database (or is it not?) but there is no information available about its exact duration of existence and/or since when it existed. But exactly that will be of great interest for coming generations.

At the same time, there are permanent and existing features that have time-relevant aspects: Opening hours of shops, duration of construction sites or time-limited structures to name a few.

To make a tagging scheme of this kind work without implications for all the rendering and editor programs, it should be considered in the API.


Imagine a researcher who wants to study urbanization. At the moment all he can do is compare maps, verbal accounts and photos of an area from different times. But all these (maybe with exception of the verbal accounts) are just snapshots and do not show a real process. All the researcher can do is to interpolate between the snapshots and hope, that he has enough data to actually do that. Enter the new tagging scheme. By writing special rendering rules he can visualize the exact progress of a certain area in time, providing that the area was sufficiently mapped from the beginning. All the mappers would have to do for that, is to apply the scheme to every feature they would otherwise just delete.

Another application could be the mapping of the age structure of buildings in a town. When we come to the point where every single building in a given town is mapped in its outlines in OSM, it would be very easy to generate age-structure maps for this place


The tags sorted by different categories

Creation of permanent features

The type of creation meant here differs from the time the feature got added to the database. It refers to the date a permanent feature (street, building, shop, etc.) was physically created.


Time / date limitations of features

There are already some tags in use, that should be kept:

  • opening_hours=* for the days / hours a feature will be open to the public

Others should be changed or introduced:


Abandoned / Disused features

Features that still exist today (and can be seen), but are no longer in use and / or abandoned. There is already a good proposal for a abandoned=yes key and we have a disused=yes key. All we need to do is to add time-relevance to them:

The beauty of this is, that we can now track the "lifespan" of a feature from creation over disuse and abandonment to deconstruction.

Start date and end date

I suggest we concentrate on using start_date=* and end_date=* for now. Frankie Roberto 16:31, 29 May 2009 (UTC)

Applies to



Depends on the specific tag.


Please comment on the talk page