[Talk-ca] Importing buildings in Canada

[Tim Elrick]

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