Jarek,
There is no question we want this data. I went through much of it
in Toronto and Kingston and I found it to be very good,
consistent and precise. Time-wise it's somewhat current with 2016
ESRI imagery (sometimes ahead, sometimes slightly behind) and is
well-aligned with it. It offers 3D features (when several
buildings appear overlapped in the dataset) but you just need to
be familiar with `building:part` tag to sort through it. I
haven't looked at other provinces but in Ontario I really have no
complaints about dataset quality whatsoever. Also I don't get
Nate's "wildly unsimplified geometries" comment. IMO geometries
are just perfectly detailed.
On Fri, Jan 18, 2019 at 2:00 PM Jarek Piórkowski
<ja...@piorkowski.ca <mailto:ja...@piorkowski.ca>> wrote:
Some more thoughts from me.
Building outlines, particularly for single-family
subdivisions as seen
in Canadian suburbs, are extremely labour-intensive to map
manually.
My parents' house is now on OSM - accurately. They live in a
city with
about 10,000 buildings, and about 0.5 active mappers. This
wouldn't
been completed manually in the next 5 years.
An option to do this automatically with a computer algorithm
detecting
objects from imagery could be suggested, but this has not
been very
accurate in OSM in the past, even when there is decent
imagery. The
only other feasible data source is government, where they
have such
data more or less.
The alternative is of course the opinion that we should not have
building outlines until someone goes through and adds the
buildings
manually. In practice what I've seen done in Toronto is that
bigger
buildings are mapped on best-effort basis from survey and
imagery,
while areas of single-family houses are left blank. This isn't
_wrong_, and maybe some prefer this.
I would also like to note that building outlines will _never_ be
completely verifiably up to date. I can't go into most people's
backyards and verify that there isn't a new addition on their
house. A
building might be legally split into two different properties
without
it being evident from the street. Imagery is out of date the
day after
it's taken, and proper offset can be difficult to establish
in big
cities where GPS signal is erratic. Pragmatically, I can tell
you from
personal experience that building data in lovingly-mapped
Berlin is
also worse than 1 meter accuracy. So again: best effort.
What do we get from having buildings? A sense of land use
(arguably
replaceable with larger landuse areas). A way to roughly estimate
population density. A way to gauge built-up density. A data
source for
locating buildings in possible flood zones, or fire risk.
Statistics:
as open data, queryable by APIs that are already used, in format
more-or-less common worldwide.
Examples were given of rowhouse- or de-facto
rowhouse-buildings where
a part is attached to the wrong building. This does not alter
any of
the above examples. It's wrong, but is it substantially more
wrong
than a blank subdivision, or one with only a few buildings
mapped? Is
it better to have a null, or be off by 5%? The legal truth is in
property records, and we can't measure houses with a ruler,
so OSM can
only be a statistical source. And then there's the question of
verifiability - some of these buildings are connected to their
neighbour building inside. I've really struggled at
distinguishing
what exactly is a "building" on Old Toronto avenues even with
street-side survey.
Bluntly, OSM is not perfect in Canada. I have pet peeves I
can quote,
and I'm sure many of you do as well. If we import, the
question is:
are we making it better?
1. Do we want this data?
2. Is it generally of acceptable quality?
3. Is there a mechanism to spot and reject where data is
particularly bad?
Cheers,
Jarek, who should really get back to updating built-last-year
stuff at Fort York
On Fri, 18 Jan 2019 at 09:31, Kyle Nuttall
<kyle.nutt...@hotmail.ca <mailto:kyle.nutt...@hotmail.ca>> wrote:
>
> The pilot project that took place in Ottawa for all these
building imports is what got me hooked into OSM in the first
place. I would make only very minor changes here and there. I
even attempted to draw building footprints but got burnt out
after only doing a single street, which was very discouraging
for me to continue.
>
> When I saw the entire neighbourhood get flooded with new
buildings that weren't there before, I was entirely intrigued
and actually got on board with the locals to help with the
process. I've been hooked since and have been to many meetups
afterwards. Helping out with projects completely unrelated to
the initial building import.
>
> I'm entirely of the belief that it is much more encouraging
for a new user to make a minor change (eg. changing
`building=yes` to `building=detached`) than it is to add
every single minor detail to each object from scratch
(visiting the location, drawing the building footprints
manually, adding address data, etc.). It's just overwhelming
for a new user.
>
> It is very much a cat-and-mouse type scenario with
community driven projects like OSM. Apparently the issue with
this import is the lack of community involvement but I can
for sure tell you that this import will help flourish the
community in the local areas. Especially if they only need to
add or change minor tags than if they would have had to
create all of this data by hand. With an import this size
there is bound to be some errors that slip through. That's
where the community comes through to correct these minor things.
>
> This is the whole point of OSM. A user creates an object
with as much information as they know and the next user comes
and adds onto that, and the next user adds and/or updates
even more. Neither of those users on their own could have
added as much detail as all of their knowledge combined.
>
> Are we supposed to just wait for a user who can add every
single building with centimetre precision and every bit of
detail simply because we can't? No, of course not. We do the
best we can and have other users who know more than we do
build on that.
>
> I fully endorse this import because I would love to see
what it does for the local communities that apparently need
to figure this import out for themselves.
>
> Cheers,
> Kyle
>
> On Jan. 18, 2019 05:40, James <james2...@gmail.com
<mailto:james2...@gmail.com>> wrote:
>
> As Frederik Ramm once said(sorry i'm paraphrasing from
memory please don't shoot me) There has never been a GO-Nogo
for imports, you bring it up on the mailing lists with
reasonable delay, is there no objections(in this case no one
was saying anything about it for 2-3 weeks) then email the
list that the import would start.
>
> On Fri., Jan. 18, 2019, 12:59 a.m. Alan Richards
<alarob...@gmail.com <mailto:alarob...@gmail.com> wrote:
>
> Along the lines of what Jarek said, sometimes silence just
means tacit acceptance, or that it's not that controversial.
There's quite a bit of government data here that is
supposedly "open" but unavailable for OSM, so I'm very glad
Stats Can was able to find a way to collect municipal data
and publish it under one national license. I was surprised
myself it hadn't got more attention, but I'm firmly onboard
with more imports if done with care.
> Manually adding buildings - especially residential
neighborhoods, is about the most boring task I can think of,
yet it does add a lot to the map.
>
> I'll admit I hadn't looked at the data quality myself, but
I just did review several task squares around BC and they
look pretty good. Houses were all in the right place,
accurate, and generally as much or even more detailed than I
typically see. Issues seemed to be mostly the larger
commercial buildings being overly large or missing detail,
but in general these are the buildings most likely to be
already mapped. To a large degree, it's up the individual
importer to do some quality control, review against existing
object, satellite, etc. If we have specific issues we can and
should address them, but if the data is largely good then I
see no need to abort or revert.
>
> alarobric
>
> On Thu, Jan 17, 2019 at 7:41 PM Jarek Piórkowski
<ja...@piorkowski.ca <mailto:ja...@piorkowski.ca>> wrote:
>
> On Thu, 17 Jan 2019 at 21:46, OSM Volunteer stevea
> <stevea...@softworkers.com
<mailto:stevea...@softworkers.com>> wrote:
> > Thanks, Jarek. Considering I am a proponent of
"perfection must not be the enemy of good" (regarding OSM
data entry), I think data which are "darn good, though not
perfect" DO deserve to enter into OSM. Sometimes "darn good"
might be 85%, 95% "good," as then we'll get it to 99% and
then 100% over time. But if the focus on "how" isn't sharp
enough to get it to 85% (or so) during initial entry, go back
and start over to get that number up. 85% sounds arbitrary,
I know, but think of it as "a solid B" which might be "passes
the class for now" without failing. And it's good we develop
a "meanwhile strategy" to take it to 99% and then 100% in the
(near- or at most mid-term) future. This isn't outrageously
difficult, though it does take patience and coordination.
Open communication is a prerequisite.
>
> Thank you for this commitment. I wish others shared it.
Unfortunately
> the reality I've been seeing in OSM is that edits which are
90+% good
> (like this import) are challenged, while edits which are
50+% bad
> (maps.me <http://maps.me> submissions, wheelmap/rosemary
v0.4.4 going to completely
> wrong locations for _years_) go unchallenged or are laboriously
> manually fixed afterward.
>
> --Jarek
>
> _______________________________________________
> Talk-ca mailing list
> Talk-ca@openstreetmap.org <mailto:Talk-ca@openstreetmap.org>
> https://lists.openstreetmap.org/listinfo/talk-ca
>
> _______________________________________________
> Talk-ca mailing list
> Talk-ca@openstreetmap.org <mailto:Talk-ca@openstreetmap.org>
> https://lists.openstreetmap.org/listinfo/talk-ca
>
>
> _______________________________________________
> Talk-ca mailing list
> Talk-ca@openstreetmap.org <mailto:Talk-ca@openstreetmap.org>
> https://lists.openstreetmap.org/listinfo/talk-ca
_______________________________________________
Talk-ca mailing list
Talk-ca@openstreetmap.org <mailto:Talk-ca@openstreetmap.org>
https://lists.openstreetmap.org/listinfo/talk-ca
--
Best Regards,
Yaro Shkvorets
_______________________________________________
Talk-ca mailing list
Talk-ca@openstreetmap.org <mailto:Talk-ca@openstreetmap.org>
https://lists.openstreetmap.org/listinfo/talk-ca
