Does that preserve topology between buildings that share nodes?
Nate Wessel
Jack of all trades, Master of Geography, PhD candidate in Urban Planning
NateWessel.com <http://natewessel.com>
On 1/26/19 11:31 AM, James wrote:
no need for scripts, qgis does this fine via the Vector menu ->
Geometry tools -> Simplify Geometries utility. I simplified it to 20cm
with the , but I think 40cm is too aggressive.
I already have scripts to compile it into the dataformat needed to be
served.
On Sat., Jan. 26, 2019, 11:16 a.m. Nate Wessel <[email protected]
<mailto:[email protected]> wrote:
Hi all,
The wiki page is indeed looking a whole lot better right now - my
thanks and congrats to everyone who contributed! There is a still
a ways to go, but we seem to be getting there quickly.
I'll echo John in saying that I would appreciate hearing from some
of the other people who chimed in to express their doubts about
the import. For my part, I'm not satisfied yet - no surprise, I'm
sure ;-). I'm thrilled that we're talking and working together in
the open, and that addresses the biggest concern I had with the
import.
These are the big issues I see remaining:
1. *Validation*: Ideally I'd like to see a good chunk (more than
half) of the data that has been imported already validated by
another user before we proceed with importing more data.
Validation is part of the import plan, so the import isn't done
until validation is done anyway. My hope is that this will flag
any issues that we can fix before moving forward, and give people
time to chime in on the import plan who maybe haven't already. I
don't want to see everything imported and only then do we start
systematically checking the quality of our work, if ever. If no
one wants to do it now, no one is going to want to do it later
either, and that doesn't bode well.
2. *Simplification*: James' analysis showed that simplification
could save several hundred megabytes (and probably more) in
Ontario alone. This is totally worth doing, but we have to
document the process and be very careful not to lose valuable
data. I believe there was also a concern raised about orthogonal
buildings being not quite orthogonal - this is something that we
should handle at the same time, again, very carefully. We
certainly don't want to coerce every building into right angles.
With respect to James, I'm not sure this is something that can be
done with a few clicks in QGIS. I would be willing to develop a
script to handle this, but it would take me about a week or two to
find the time to do this properly. We would need to simultaneously
A) simplify straight lines B) orthogonalize where possible and C)
preserve topology between connected buildings. This is not
impossible, it just takes time and care to do correctly.
3. *Speed and Size*: To John's point, it seems like people
certainly are not sticking to the areas they know, unless they get
around a whole hell of a lot more than I do, and yes this is a
problem. The whole Toronto region was basically imported by two
people: DannyMcD seems to have done the entire west side of the
region (hundreds of square kilometers) while zzptichka imported
the entire east side of the region (again a truly massive area),
both in the matter of a week or two. They only stopped in the
middle where there were more buildings already and things got a
bit more difficult. The middle is where I live, and when I saw
that wave of buildings coming, I sounded the alarms.
This is way too fast - no one person should be able to import the
GTA in a couple weeks. A big part of the problem, IMO is that the
task squares are much too large, and allow/require a user to
import huge areas at once. At the least, some of the task squares
in central Toronto are impossibly large, including hundreds or
thousands of buildings already mapped in OSM. Conflation on these,
if done properly would take the better part of a day, and people
are likely to get sloppy.
I would like to see the task squares dramatically reduced in size
as a way of slowing people down, helping them stick to areas they
know well, and keeping them focused on data quality over quantity.
This would also make the process much more accessible to local
mappers who don't already have tons of experience importing.
4. *Conflation*: I don't think the current conflation plan is
adequate(ly documented). In practice, what people are actually
doing may be fine, but I really want to see some better thought on
how to handle existing buildings. Right now the wiki says for
example "/Before merging buildings data switch to OSM layer and
see if there are any clusters of buildings without any meaningful
tags you can delete to save time when merging/."
With respect to whoever wrote this, this approach seems to value
time over data integrity and I just don't think that's how OSM
should operate. We need to be more careful with the existing data,
and we need to show that care with clear and acceptable guidelines
for handling the data that countless people have already spent
their time contributing. We don't do OSM any favours by carelessly
deleting and replacing data. Help convince me that this isn't
what's happening.
Until some effort has been made to address these concerns, I will
continue to oppose this import moving forward. And to be clear, I
don't want to oppose this import - I have too much else I should
be focusing on. I just don't want to see another shoddy import in
Toronto (or elsewhere).
Best,
Nate Wessel
Jack of all trades, Master of Geography, PhD candidate in Urban
Planning
NateWessel.com <http://natewessel.com>
On 1/26/19 8:49 AM, john whelan wrote:
I'm not certain how this addresses the concerns raised by Andrew
Lester and
Pierre Béland,
and I seem to recall one other person who expressed concerns.
I think it is important that their concerns are addressed.
Perhaps they would be kind enough to comment on whether or not
this approach addresses their concerns.
Do we have a concern that some mappers have been importing
buildings further than say twenty kilometers from where they live?
Have you found volunteers of local mappers in
Alberta
British Columbia
Manitoba
New Brunswick
Newfoundland and Labrador
Northwest Territories
Nova Scotia
Nunavut
Ontario
Prince Edward Island
Quebec
Saskatchewan
Yukon
Who will be willing to oversee the import in each province?
Does this mean the smaller provinces may not see any data?
How will you handle cities of say 80,000 population in a smaller
province who have an interest in seeing their buildings available
but have no idea on how to contact the provincial group?
If we go back to earlier times it was a suggestion in talk-ca
that we use the single import approach and it was mentioned at
the time there didn't seem to be a list of local mapper groups in
Canada.
I'm not saying the approach of a single import as far as the
import list and talk-ca followed by a procedure of locally
organised mappers bringing in the data is wrong I'm just trying
to ensure the project moves forward and we are in agreement.
Thanks
Cheerio John
On Sat, 26 Jan 2019 at 00:17, OSM Volunteer stevea
<[email protected] <mailto:[email protected]>> wrote:
Thanks to some good old-fashioned OSM collaboration, both the
https://wiki.osm.org/wiki/Canada_Building_Import and
https://wiki.osm.org/wiki/WikiProject_Canada/Building_Canada_2020#NEWS.2C_January_2019
have been updated. (The latter points to the former).
In short, it says there are now step-by-steps to begin an
import for a particular province, and that as the steps get
fine-tuned (they look good, but might get minor
improvements), building a community of at least one or two
mappers in each of the provinces with data available, the
Tasking Manager can and will lift the "On Hold" or "Stopped"
status.
Nice going, Canada!
See you later,
SteveA
California
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