[HOT] Task 1238 Canaan Important Deletion of existing objects

Rafael Avila Coya ravilacoya at gmail.com
Fri Nov 20 19:30:19 UTC 2015


Hi, Pierre:

I guess this is what the majority of people do, and only the most
experienced users re-trace objects, also using the replace geometry tool
(CTRL+SHIFT+G). It took me long to me to realise about that too.

As usual in these cases, I would contact him to check what happened, and
tell him how he should proceed from now on, so he learns the advantages
of not deleting objects unless really needed, but improving those
objects instead.

I've checked the edits by that user, and he made lots of changesets
(maybe around hundred), so I see a potencial reversion very troublesome
and time consuming.

The first of the changesets seem to have been edited about a month ago
[1]. So around 6 am 21 Oct 2015.

To check what buildings were at the area before deletion, you may use
the next overpass query: [2]. As there isn't any Canaan area in OSM,
just used the ({{bbox}}) thing. I set the date at 00:00:01 of that day
(so 6 hours before the first changeset).

With this other query [3] you can get a file with the building ways that
were present at that same date and time, that were deleted, and also
those that were modified and new buildings created. The output file
don't open in JOSM, but could be use to get statistical info (for
example) on number of buildings deleted.

Cheers,

Rafael.

[1] http://www.openstreetmap.org/changeset/34784526
[2] http://overpass-turbo.eu/s/cQv
[3] http://overpass-turbo.eu/s/cQw


On 20/11/15 19:29, Pierre BĂ©land wrote:
> Being in Port-au-Prince for a Training session of the Haiti
> OpenStreetMap community (Espace OSM francophone project), I collaborate
> this week with the Haiti OSM community who have monitored urbanisation
> progression in the Canaan sector, providing UAV imagery in 2013, 2014
> and 2015 (60% of the zone covered so far).  They have also added to osm
> the building footprints in the area from precise and accurate imagery (4
> cm precision).
> 
> We organize a mapathon tomorrow to revise the Canaan zone using the
> November 2015 imagery available and monitor the progress of rapid House
> contruction in this sector. 
> 
> Planning the work, I see today that one contributor did most of Tak 1238
> for Canaan Haiti and it seems deleted systematically buildings before
> redrawing them.  In JOSM if I download buildings and search for newly
> created buildings (ie version:1), most of the buildings have version=1.
> 
> If this is exact, we should note that this is contrary to the OSM
> philosophy. The rule that we generally follow at OSM to respect previous
> contributions and keep history, is to revise geometry and not delete /
> retrace.
> 
> For these two changesets alone, I count 50 and 44 ways deleted.
> http://www.openstreetmap.org/changeset/35462043
> http://www.openstreetmap.org/changeset/35462424
> 
> At the same time, many buildings are missing. Since I have no comparizon
> with the situation before this mapping, It is hard to say what was done
> exactly, if any building were erased and not replaced.
> 
> Could somebody confirm that buildings were systematically deleted before
> retracing. What should we do to correct rapidly this situation before we
> start the mapathon tomorrow?
>  
>  
> Pierre
> 
> 
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