[Talk-ca] City of Ottawa imported buildings & addresses

AJ Ashton aj at ajashton.ca
Mon Oct 17 16:59:51 UTC 2016

I haven't seen any substantial discussion about the Ottawa buildings &
addresses import anywhere. I did see the thread a number of weeks back,
"Crowdsourcing buildings with Statistics Canada," but I didn't see
anything discussed that sounds like the planning of a mass import. The
wiki page linked from the discussion [0] is completely empty. From a
changeset discussion I was pointed to another section of the wiki [2]
which again has few details and does not sound like an import
("...inviting contributors to crowdsource information on buildings").

[1]: http://wiki.openstreetmap.org/wiki/Ottawa_Gatineau_Buildings

What has actually happened is most (or all?) of the existing buildings
in Ottawa were deleted, and then replaced by imported data. For example
changeset 42699159 [3] deleted hundreds of buildings and addresses I had
mapped in my former home of Stittsville. Changeset 42699460 [4] replaced
everything with City of Ottawa data.

[3]: https://osmcha.mapbox.com/42699159/
[4]: https://osmcha.mapbox.com/42699460/

The quality of the imported shapes seems fine and I have nothing against
building imports in principle. I just wish existing data could have been
updated or left alone - I don't see a substantial difference between
what I had traced from Bing and the import except for an offset of
perhaps a few meters. Although I saw someone noted on IRC that in
several cases existing properties such as building:levels tags were
lost; this is more concerning.

In addition to building footprints, addresses are also being imported.
This data is a little more problematic and the importers seem to be
taking a "import now, fix later" approach. Example: changeset 42633517
[5] added over 20 thousand address nodes that were clearly not
quality-checked. Addresses are being imported as points when they could
be attached to buildings, and sometimes address points are doubled,
tripled, or even quadrupled [6].

[5]: https://osmcha.mapbox.com/42633517/
[6]: Eg this area:

Could the organizers of this import point me to any further mailing list
discussions or wiki pages I might have missed? Can we talk about why the
clearcut approach to existing data was taken, and why the address data
was not cleaned up *before* import?

(The changesets I linked to may make it look like I am specifically
calling out user LogicalViolinist, but the import was a group effort by
a number of users. LogicalViolinist just happens to have covered the
part of Ottawa I am most familiar with.)

  AJ Ashton
  aj at ajashton.ca

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