I would assume in most cases the imported building footprint will be
more precise than existing data. For me, this would be a reason to
replace already existing objects. However, I think this is a case by
case decision. However, I think it is important to keep tags and history
of buildings already existent in OSM. This is how I would read/interpret
the import guideline stated by Nate: "If you are importing data where
there is already some data in OSM, then *you need to combine this data*
in an appropriate way or suppress the import of features with overlap
with existing data." (emphasis added by me)
However, that just means, the import, hence, is nothing easy and could
not be achieve quickly, I would assume. One way of making sure that this
is dealt with diligently, would be setting the tasking manager to
'experienced mappers only'. We would have to ask James, who is in charge
of the Canada Tasking Manager, how to edit/set up the 'experienced
mapper role' in the TM. It might be possible to feed in a list of
mappers manually or to set a threshold of objects/changesets that they
must have entered in OSM. However, maybe only mappers who feel
experienced enough to handle the import would contribute to the TM
project anyway and we let everyone judge on their own and don't restrict
access.
If we were to separate the new and overlapping buildings, I am also
leaning towards Daniel's assessment. I would be afraid to cause more
issues than by doing it all at once (with a reasonable tile size, of
course).
In the end, the main point of importing this specific dataset fulfils
two purposes, in my opinion: first, to add missing buildings (if it were
just for this purpose we could also use the much bigger Microsoft
dataset), second, to get the best geospatial representation possible in
our OSM database. That means, we defer from using the Microsoft dataset
and use the much higher quality data from the ODB. This also means that
we should replace already existing buildings (yet keeping tags and
history) wherever the ODB footprint is more precise than the existing one.
Just my two cents here,
Tim
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