[OSM-talk] Historical Data in OSM database

Ed Avis eda at waniasset.com
Tue Nov 9 13:21:59 GMT 2010


Egil Hjelmeland <privat <at> egil-hjelmeland.no> writes:

>If you prefix tag keys of  historic elements with  "past:", it will not 
>interfere with extisting SW conserned with rendering the present state.

Agreed.  But as Frederik pointed out, it will confuse people using editors.
People often snap together nodes so that a road and an administrative boundary
can node share, for example.  They might end up snapping to purely historical
nodes or even adjusting the historical stuff a bit to fit with other objects,
as we might adjust a building's position slightly relative to a road junction.

Philosophically, it's great to put useful data in OSM, and historical things can
be useful, but until now we've used fairly objective, 'on the ground' criteria
to ultimately decide what gets mapped(*).  The route of a former railway can be
seen on the ground and so is mapped; but something of which no physical trace
remains cannot be mapped using purely objective criteria.  You'd need a more
Wikipedia-like 'verifiability' criterion.

(*) With the exception of facts that exist only by human agreement, such as
where a county boundary is, or place names, or access rights.  Quite a few
exceptions actually!

Leveraging the OSM infrastructure for historical mapping is a good idea, but not
in the same database - at least not at this stage.  Maybe if a consensus can be
reached and editors can add support for ignoring historical data, the two could
live side by side in the same database.  But they cannot really affect each
other or interact in any way (?), so it seems that a separate database entirely
would work fine.

That said, historical information can be usefully and objectively added to a
present-day map in some circumstances.  I often add a note tag for 'former
church' or 'formerly known as'.  In Britain the Ordnance Survey maps show the
site of battles with a crossed swords marker.  And administrative boundaries
often have no physical existence.  More support for mapping this kind of thing
would be welcome.

-- 
Ed Avis <eda at waniasset.com>




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