[HOT] Task 1238 Canaan Important Deletion of existing objects

Dale Kunce dale.kunce at gmail.com
Fri Nov 20 20:00:43 UTC 2015


Rafael,
We decided to do large scale deletion for a number of reasons.

   - Errors within iD that cause many buildings to be traced several times
   thus resulting in many many overlapping buildings.
   - I personally fixed thousands of overlaps and fixed several thousand of
      other validation errors in the area.
   - Poor spatial consistency between multiple imagery resources
      - Bing
      - 2013 drone imagery
      - 2014 drone imagery
      - 2015 drone imagery
      - Recent GeoEye imagery
   - Lack of existing drone imagery led us to acquire high resolution
   satellite imagery.
      - Imagery isn't nearly as clean and sharp as the drone imagery being
      shot but is consistent throughout the entire area.

*Do not *revert these changes as it represents hundreds of man hours by ARC
staff to clean up and fix this area. The area in its current state is the
most up to date the area *has ever been *due to previous efforts by Haiti
Communitaire and the ARC GIS team. We have spent considerable time in the
field and remotely mapping this area.

Again, for continued questions about these changesets please contact me
off-list.

Dale




On Fri, Nov 20, 2015 at 2:30 PM, Rafael Avila Coya <ravilacoya at gmail.com>
wrote:

> 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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>
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-- 
sent from my mobile device

Dale Kunce
http://normalhabit.com
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