[Imports] Building extraction in Mathare, Nairobi.

Sébastien Pierrel sebastien.pierrel at gmail.com
Wed May 18 14:37:24 UTC 2011


Hi,

MapKibera is growing and has expended to other slums of Nairobi. We've been
working a lot in Mathare and AAAS provided us with aerial imagery building
extraction. See Primož's
post<http://mappingnobigdeal.wordpress.com/2011/03/26/building-extraction-of-mathare-no10-mashimoni-mabatini-and-thayu/>
for
the analysis.

I'm looking at how to import the data into OSM. This is my first import, so
I read the "import guidelines" and took the French CLC import as a model. I
documented my steps in our
wiki<http://mapkibera.org/wiki/index.php?title=Mathare_Building_import>
(feedback
appreciated). When the import is done, I'll copy this page to the osm wiki.
I'll also quote AAAS stating that they give us the data. We are the local
community, so I thought it was necessary to only contact this mailing prior
to proceeding to the import.

I'm about to generate the OSM data and I'm anticipating the following step:
how to import the data to OSM? This last step isn't described in the CLC
import page.

We consider this new dataset to be more accurate than the existing data, so
I'm going to remove all existing polygons that intersect that new ones. When
preparing the data to be imported, I took care to check what buildings were
already mapped, and to copy their tags (if any) to the new ones.
How can I delete the 'old' polygons during the import of the new data?

Should I try to keep the osm id of these buildings and assign it to new
imported one? It sounds a bit tricky since some some buildings are going to
be replaced by several new ones, so I was going to ignore this part.


Cheers,
/Seb.
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