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

Thu Jan 24 16:40:41 UTC 2019

OSM wiki: https://wiki.openstreetmap.org/wiki/Key:building:part
It's not in the import wiki though since whoever wrote it didn't know about
it at the time.
Here's what I mean by mapping 3D features in our case. Say there is a
residential tower on a podium. In the StatsCan data usually you would find
both of these outlines - large podium outline and smaller tower outline
inside it. They would both be tagged with "building=yes" tag. Obviously we
can't upload that as-is. We can either just remove tower outline leaving
only 2D podium outline. Or, we can tag the tower outline with
"building:part=yes". Someone local can add other tags to it later on, such
as "building:levels", "building:material", "building:min_level",
"addr:housenumber" (if there are two towers on one podium with different
house numbers for example), etc. I find the latter approach to be the right
one.

On Thu, Jan 24, 2019 at 11:15 AM Nate Wessel <bike756 at gmail.com> wrote:

> Hi Yaro,
>
> I just had a chance to look at the documentation on the source data and I
> wasn't able to find anything about 3D features or parts of buildings being
> mapped separately. Are you guessing here, or is there documentation on
> this? If so can you point us to it?
>
> In any case, the big shapefiles from StatsCan don't provide enough
> information to reconstruct any 3D geometries, so I'd be inclined to remove
> these from the import unless they can be brought in from another source
> with better documentation / attribute tagging. (i.e. City of Toronto?)
>
> Thanks,
> Nate Wessel
> Jack of all trades, Master of Geography, PhD candidate in Urban Planning
> NateWessel.com <http://natewessel.com>
>
> On 1/18/19 2:48 PM, Yaro Shkvorets wrote:
>
> 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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-- 
Best Regards,
          Yaro Shkvorets
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