[Talk-GB] Deletions and newbie editors

Lester Caine lester at lsces.co.uk
Mon Oct 6 10:43:15 UTC 2014


On 06/10/14 10:35, David Woolley wrote:
> On 05/10/14 21:31, David Woolley wrote:
> 
>> Whilst the archive exists and is accessible, what I'm not aware of is an
>> API interface that allows one to retrieve the versions of objects that
>> existed at a particular date.
> 
> It has been pointed out to me, off list, that the overpass API can
> retrieve a back-dated version.  Although I haven't tried this out yet,
> this would seem to be the option:
> <http://wiki.openstreetmap.org/wiki/Overpass_API/Overpass_QL#Attic_data_.28.22date.22.29>.

The information is available, but as yet there is no joined up method of
doing some things. As far as I am aware. That allows you to see the
state of the data at a time, but not a view of what exists at that time.

If the start_date is correctly added to every object in an area of the
map, then by changing the limit created by selecting a particular date,
you see a set of data based on that date. This is fine for objects that
still exist, but leaves a hole where objects have changed and it is this
that OHM is trying to address. Trying to merge data from the current
'filtered' view and some alternate source is the tricky bit. Reading a
CURRENT set of data will include the state_date tag and so filtering
that can happen locally, but adding the essentially quite small amount
of historic changes is not so easy to achieve?

-- 
Lester Caine - G8HFL
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