Hi all,
Daniel, thanks for continuing to prod the conversation along :-)
I guess the point of disagreement here is that I generally don't agree
that the ODB buildings are of higher quality than what's already in OSM.
The ODB data I've seen is quite messy, and IMO only marginally better
than having no data in an area, especially if not properly checked and
conflated with surrounding OSM data. People seem to generally disagree
with that perspective though, so I'll assume that other areas are better
represented by their respective ODB data sources. Central Toronto may
just not have been well mapped by the City's GIS dept; it certainly
isn't the easiest thing to get right.
My real worry here is that someone will be carelessly going through an
import replacing geometries and will destroy the work of an editor like
myself who carefully contributed their time to make a neat and accurate
map. I know for certain I've contributed better data in Toronto than
what's available from government sources for the same area.
We must recall that governments produce building footprints in the same
way that we do - usually by tracing imagery, and there is little reason
to suppose that their data is better or more accurate just because it
comes from a seemingly authoritative source. It comes from interns -
likely interns with outdated software and low-resolution surveys.
All that being said, I think my real reluctance to go with the flow here
stems from the haste and carelessness of the original importers in the
GTA. We're working toward a process that should be very different from
theirs though and I probably need to just trust that our process will be
calmer, slower, and more thoughtful. If it is, I can get on board.
But also - sorry this is such a long email - we certainly should not be
manually doing re-conflation where buildings are very dense (e.g.
downtown Toronto) or where they have already been imported extensively
(much of the rest of the GTA). The import plan I'm working on for
Toronto will take care of most of this automatically by importing only
in the sparse gaps between existing OSM buildings. For other parts of
Canada, this may not be much of an issue at all - I wouldn't know.
Best,
Nate Wessel, PhD
Planner, Cartographer, Transport Nerd
NateWessel.com <https://www.natewessel.com>
On 2020-01-18 5:24 p.m., Daniel @jfd553 wrote:
Bonjour groupe,
Here is a sequential summary of the last exchanges. I inserted some
comments […] within these exchanges description and summarize what I
understand from it at the end.
*Nate*asked not to confuse the process of importing new data with that
of updating/modifying existing OSM data in order to keep things simple
for this import.
*Daniel*(I) responded that importing new data and updating/modifying
existing ones at the same time (when necessary) is not unusual in OSM
[/and would be more efficient/].
*John*replied that importing new data and updating/modify existing
data when required worked quite nicely when importing Ottawa.
*Nate *explained he believes that the buildings will not be compared
manually since there are hundreds of thousands of them in OSM for
Toronto alone. In other words, he thinks there will be automated
edits, and these edits are not governed by the same policies as
imports. [/This is an important consideration. What has happened in
Ottawa and Toronto so far? Have automatic processes been used?/]
*Tim*replied that in most cases it might be appropriate to replace OSM
data, as he believes [/as I do for most of the cases/] that the ODB
footprints will be more accurate than existing buildings. However he
considers it is a case-by-case decision [/then no automation process
should be used/].
*John*couldn’t resist digressing toward the “Microsoft buildings
import” but had to bring back the discussion on ODB import after
reactions from *Tim* and *Pierre* (LOL).
I think that, somehow, we could all agree on how the import should be
done:
-Align images on ODB, unless evidence ODB data are ill located.
-Align existing OSM content with the image, *only* if necessary after
aligning the image with ODB.
-Import non-existent buildings in OSM.
-Conflate ODB and OSM buildings, *only* if necessary.
-
To address Nate’s legitimate concerns, we could agree that there will
be *no* automatic changes/conflation of existing buildings. Having a
local import manager and by using the task manager, we should be able
to ensure that there will be no unauthorized import (i.e. not
responding to the above).
Am I too optimistic?
Daniel
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