[Talk-ca] Ongoing Canadian building import needs to be stopped, possibly reverted

Fri Jan 18 19:48:26 UTC 2019

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 <jarek at 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 Imagery is out of date the day after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.nuttall at 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 <james2432 at 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 <alarobric at 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 <jarek at piorkowski.ca>
> wrote:
> >
> > On Thu, 17 Jan 2019 at 21:46, OSM Volunteer stevea
> > <steveaOSM at 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 submissions, wheelmap/rosemary v0.4.4 going to completely
> > wrong locations for _years_) go unchallenged or are laboriously
> > manually fixed afterward.
> >
> > --Jarek
> >
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-- 
Best Regards,
          Yaro Shkvorets
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