[Talk-ca] Multipolygon problems

James james2432 at gmail.com
Fri Jun 30 11:17:00 UTC 2017


https://i.imgur.com/8xKttYm.jpg

Image was ridiculously small

On Fri, Jun 30, 2017 at 6:28 AM, James <james2432 at gmail.com> wrote:

> Example:
> https://i.imgur.com/8xKttYm_d.jpg
>
> Represents multiple thousand square kilometers of forest/objects. To
> actually be able to fix it correctly you NEED to launch JOSM in 64bit mode
> with min/max memory values set or else it will crap out/freeze at 2GB of
> memory. Now 1. JOSM doesnt document this ANYWHERE/IS VERY VERY HARD TO FIND
> for the common user. I doubt many people know about the 2gb limit(other
> than power mappers) .
> Personally I find it very arrogant of you to say well, it's been a week
> might as well contact the DWG and revert all of Canada, cause no one
> replied to my email... not everyone has the experiance needed to merge down
> polygons/relations on such a large object scale and very wide spread
> throughout Canada
>
>
> On Jun 30, 2017 6:12 AM, "James" <james2432 at gmail.com> wrote:
>
> The problem that canvec has is multi polygons with different attributes
> were stacked on top of eachother(i.e. hole in the forest that is also a
> lake? That makes 2 polygons with same shape stacked one of top of
> eachother... marshland+water+hole in forest? 3 polygons etc etc. Not that I
> wouldnt live it fixed, but as someone that has "fixed" canvec data before
> dropping it in, It's a massive undertaking and really complexe/abstract
> thing to do.
>
> On Jun 30, 2017 3:54 AM, "Jochen Topf" <jochen at remote.org> wrote:
>
> Hi!
>
> A week ago I wrote this email and nobody answered it yet. Does that
> mean that nobody feels responsible for the import that created this data
> and nobody here cares for this data?
>
> I see three ways forward:
> * We do nothing. The broken data stays in OSM. Not a good solution,
>   because every user of the data has to work around this or handle the
>   complaints.
> * The Canadian community steps up and fixes the data, automatically or
>   manually.
> * We ask the Data Working Group to remove the broken import.
>
> Jochen
>
> On Thu, Jun 22, 2017 at 11:38:15AM +0200, Jochen Topf wrote:
> > Date: Thu, 22 Jun 2017 11:38:15 +0200
> > From: Jochen Topf <jochen at remote.org>
> > To: talk-ca at openstreetmap.org
> > Subject: [Talk-ca] Multipolygon problems
> >
> > Hi!
> >
> > In the last days the OpenStreetMap Carto Style 4.0 is being deployed on
> > the OSMF tile servers. This new version of the style doesn't take
> > old-style multipolygons (where the tags are on the outer ways instead of
> > on the relation) into account any more. In a huge effort in the last
> > months we have converted all old-style multipolygons to the modern
> > tagging, so this is a good step!
> >
> > Unfortunately, as a side-effect of this change, many multipolygon
> > relations now appear wrong on the map. This is the case for multipolygon
> > relations that have the same tags on the relation as well as on (some of
> > the) outer or inner ways. This is *wrong* tagging, and needs to be
> > fixed. (Note that this always was wrong tagging, even before we
> > deprecated old-style multipolygons, but the way the software worked with
> > old-style multipolygons, this problem was not visible on the map. But
> > now it is.)
> >
> > Here is an example: http://www.openstreetmap.org/relation/1330741 . As
> > you can see (unless somebody fixes this :-) the clearing in the forest
> > that should just have grass, also has tree symbols on it. In many other
> > cases it is not this obvious, there are just islands in a river missing
> > or so.
> >
> > There are about 50,000 cases like this worldwide, forests, waterways,
> > all sorts of areas. But the worst problem is in Canada. There are about
> > 15,000 affected relations, most from the CanVec imports.
> >
> > First, we have to make sure that there are no further imports of broken
> > data. I hope the people who have done those imports (and might still
> > continue) are here on this mailing list. If not please make them aware
> > of this issue and/or put me in touch with them. Second, somebody needs
> > to clean up the broken data, either automatically or manually. 99% of
> > the data has not been changed since the import, so it might be feasible
> > to do an automatic cleanup, but somebody has to do this. Otherwise we'll
> > have to do a manual cleanup, through tools such as Maproulette and the
> > OSM Inspector. I am currently in the process of creating Maproulette
> > challenges for other areas of the planet, but will not do this for
> > Canada at this time. Lets discuss this here first.
> >
> > I can provide OSM data extracts, statistics, etc. if somebody wants to
> > look at the data.
> >
> > All of this is part of a larger effort to fix areas in OSM. See
> > http://area.jochentopf.com/ for more information. There is also a thread
> > on the talk mailinglist at
> > https://lists.openstreetmap.org/pipermail/talk/2017-June/078203.html
> > and this issue
> > https://github.com/osmlab/fixing-polygons-in-osm/issues/36 .
> > News of the effort are posted regularly to
> > https://github.com/osmlab/fixing-polygons-in-osm/issues/15 .
> >
> > Jochen
> > --
> > Jochen Topf  jochen at remote.org  https://www.jochentopf.com/
> +49-351-31778688
> >
> > _______________________________________________
> > Talk-ca mailing list
> > Talk-ca at openstreetmap.org
> > https://lists.openstreetmap.org/listinfo/talk-ca
>
> --
> Jochen Topf  jochen at remote.org  https://www.jochentopf.com/
> +49-351-31778688
>
> _______________________________________________
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>
>
>
>


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