[Talk-ca] Building Import update

Sat Jan 26 19:10:52 UTC 2019

I'm not installing postgesql for you to accept simplification, that YOU
said was required because there were 2x as many points(which was proved
wrong via the simplification) If you want to have fun with the file, go a
head.

On Sat., Jan. 26, 2019, 2:00 p.m. Nate Wessel <bike756 at gmail.com wrote:

> Building count doesn't really have anything to do with preserving
> topology, and I'm not sure a visual inspection would cut it - Can you look
> at the documentation for this tool and verify that it preserves the
> topology of polygon layers?
>
> This is a good illustration of the (potential) problem:
> https://trac.osgeo.org/postgis/wiki/UsersWikiSimplifyPreserveTopology
> Nate Wessel
> Jack of all trades, Master of Geography, PhD candidate in Urban Planning
> NateWessel.com <http://natewessel.com>
>
> On 1/26/19 12:31 PM, James wrote:
>
> it does if you saw my analysis of building(polygon count) remains the same
> also visually inspected a few and there was preservation of them
>
> On Sat., Jan. 26, 2019, 11:43 a.m. Nate Wessel <bike756 at gmail.com wrote:
>
>> 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 <bike756 at gmail.com 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 <
>>> steveaOSM at softworkers.com> 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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