[Imports] [Talk-ca] [Import] Ottawa Buildings & Addresses [Statistics Canada project]

James james2432 at gmail.com
Mon Oct 24 22:52:33 UTC 2016


I can guarantee that this data is roof level data. While I was examining
data there were cart returns mapped as outlines. This data was also traced
via orthophotos

On Oct 24, 2016 6:45 PM, "Christoph Hormann" <chris_hormann at gmx.de> wrote:

> On Monday 24 October 2016, Stewart C. Russell wrote:
> >
> > > Could you please clarify what the alleged source of the building
> > > data to be imported is?
> >
> > Yes, as far as I understand it, at least: these data to be imported
> > were given to a group of OSM contributors by the City of Ottawa. They
> > have explicit permission to include it in OSM from the City. The only
> > place you can inspect the data is on the contributors' own hosting
> > sites, as the city doesn't host it anywhere. Details of the licence
> > and permissions are on the Ottawa import information page.
>
> I would then suggest to contact the person who provided the files for
> metadata and specifications on those, in particular dates and methods
> of survey, processing applied, especially coordinate system conversions
> and specifications on what exactly is contained in it (i.e. what the
> definition of a building is here and if it's ground footprints or roof
> outlines).  You also might want to specifically ask regarding the
> geometry issues i pointed out earlier.
>
> You can be pretty sure the original producer of this data set has this
> information and if there is interest in having this data in OSM they
> should also be willing to provide such information.
>
> In OpenStreetMap we put high importance on knowing and documenting how
> data is acquired since - as every experienced mapper knows - sources of
> information can be faulty and misleading.  Just because someone says: I
> have this data here and you may use it and it mostly looks reasonable
> and plausible at the first glance does not mean we should throw all our
> sense for critical evaluation of sources out of the window, especially
> if you plan to add several hundred thousand new features.
>
> > The public 2011 data set is cut into 2×1 km tiles, slicing through
> > buildings on the border. There are no common attributes which would
> > allow repair, as the data is packaged in AutoCAD DWG files.
>
> This alone should not be a problem since you know the location of the
> cuts and therefore could dissolve them based on position.
>
> The real question is - is there a factual basis for the assumption that
> the data you intend to import is newer than the data in these files?
> Note a different level of detail is not necessarily an indication for
> age or accuracy of the data.
>
>
> --
> Christoph Hormann
> http://www.imagico.de/
>
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