[Talk-ca] Ongoing Canadian building import needs to be stopped, possibly reverted
Nate Wessel
bike756 at gmail.com
Thu Jan 24 16:49:20 UTC 2019
Is it sufficient to tag fragments as building:part without indicating
which part or how many stories? If the data is properly structured, this
seems like something that could be handled in preprocessing by checking
for overlapping polygons. It looks like perhaps we might just have to
find the largest part for the footprint (building=yes) and any
intersecting smaller buildings (building:part=yes).
We might also need to generate some building relations for more complex
features.
Nate Wessel
Jack of all trades, Master of Geography, PhD candidate in Urban Planning
NateWessel.com <http://natewessel.com>
On 1/24/19 11:40 AM, Yaro Shkvorets wrote:
> 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
> <mailto: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 <mailto: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 <mailto: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
>> <mailto: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 <mailto: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 <mailto:jarek at piorkowski.ca>> wrote:
>> >
>> > On Thu, 17 Jan 2019 at 21:46, OSM Volunteer stevea
>> > <steveaOSM at softworkers.com
>> <mailto: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 <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
>> >
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>> --
>> Best Regards,
>> Yaro Shkvorets
>>
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> --
> Best Regards,
> Yaro Shkvorets
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