I just learned yesterday of a very large import of buildings across
Canada that seems to have been posted to this list in November without
getting much of a response. I remember seeing the email about it at the
time, and as there was substantial reference to an import in Ottawa, I
thought the import was limited to that city and failed to read the
actual details of the proposal. This appears to be an import of building
footprints across ALL MAJOR CANADIAN CITIES.
https://wiki.openstreetmap.org/wiki/WikiProject_Canada/Canada_Stats_Canada_Building_Outlines_Import/Plan
https://lists.openstreetmap.org/pipermail/imports/2018-November/005812.html
This is being imported NOW, very quickly, and the data I've seen in
Toronto is of dubious quality at best. Given the speed with which this
has taken place and the lack of clear discussion about what exactly the
import is, what exactly it covers, I would like to see this import
effort halted immediately if not reverted.
My concerns are as follows:
1. I'm a very active mapper living and editing in Toronto and subscribed
to the relevant lists and slack channels, yet I only just learned of
this when the buildings encroached on my own neighborhood. I imagine
many others also missed the notice and have not had any chance to review
the plan.
2. There are countless examples of truly terrible data quality, weird
footprints, overlapping buildings, wildly unsimplified geometries, etc.
e.g.
https://www.openstreetmap.org/way/663824488
https://www.openstreetmap.org/way/662764169
etc.
These issues clearly fail in a simple JOSM validation, which indicated
that no validation is happening before upload.
3. The data is being imported in extremely large chunks, (see the
tasking manager grid for Ontario:
http://tasks.osmcanada.ca/project/145), much larger I think than any one
person could validate or review in a single sitting. There are more than
ten thousand buildings in some of these grid cells. As changesets are
limited to 10k objects, including nodes, it is extremely difficult to
see what data was there before these changes, as each task involves
multiple essentially simultaneous changesets.
4. The approach seems to be import first, validate second (if ever?).
5. The wiki plan gives no clear description of the plan for integrating
new data with old. In places where there used to be user-contributed
buildings, I now see buildings from this import covering or replacing
those buildings with no remaining way history. I don't think I need to
say that this is completely unacceptable.
What are the options on the table here? There has been a truly massive
amount of data imported in the last couple of weeks. I'd love to wind
back time and criticize the living hell out of this plan before it
started, but that's not where we're at. What can be done?
:-(
--
Nate Wessel
Jack of all trades, Master of Geography, PhD candidate in Urban Planning
NateWessel.com <http://natewessel.com>
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