[Tagging] Rarely verified and third-party data staleness in OpenStreetMap

Frederik Ramm frederik at remote.org
Mon Apr 6 08:12:46 UTC 2020


Hello Stuart,

may I suggest that you choose a personal email address for participating
in mailing lists. It feels really strange to address a message to
"europeanwaterproject". I don't want to talk with "a project", I want to
talk with a person.

On 06.04.20 09:31, European Water Project wrote:
> Please find attached a draft note for a feature proposal, which I have
> no idea if is even technically possible, for automatically adding a last
> verified date/creation date to specific keys.  Maybe there is a
> better/more efficient way ?

There are several issues here.

Firstly, I don't know what you mean by "automatically adding". After all
you need a person to manually confirm that the object is unchanged
before a tag is added, so which part of this is automatic? Surely you
are not saying that you want to add a tag to every object that simply
duplicates the last-edit timestamp already stored?

Secondly, this is a problem shared by all the "last survey" approaches:
You're standing the logic on its head. You're essentially saying: "If
the object has NOT changed in reality, please DO change it in OSM" (by
updating the last-checked tag). This means that we're being asked to
switch from mapping changes to mapping non-changes, with a potentially
huge data inflation in OSM (in theory I could update the "last survey"
of my local supermarket every time I shop there...). Your idea to
identify potentially fast-changing things and concentrate on these
softens the impact but still, we'd be churning out new versions of
objects like crazy just to confirm they are still there. (Everytime you
make a little change to one of the object's 10 tags, a full copy of the
object is created in OSM.)

Thirdly, also shared by many "last survey" approaches: If you tag a
restaurant with a last survey date then exactly what have you surveyed?
Just that it is still there? That is still has these opening hours? Or
that it still gives you free water? There's potential from confusion here.

The topic of staleness has been attacked by scientists in the past,
trying statistical approaches along the lines of "if there's a decent
number of detailed edits by different people in this area, then there is
a high probability of data being up to date". This of course doesn't
give you the same reliability but perhaps it delivers some results
without being the massively invasive concept you're proposing.

Bye
Frederik

-- 
Frederik Ramm  ##  eMail frederik at remote.org  ##  N49°00'09" E008°23'33"



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