[HOT] Broken (multi)polygon cleanup

Jochen Topf jochen at remote.org
Fri Mar 17 13:43:09 UTC 2017


Hi!

did you read those documents linked from http://area.jochentopf.com/ ?

https://github.com/osmlab/fixing-polygons-in-osm/blob/master/doc/background.md
https://github.com/osmlab/fixing-polygons-in-osm/blob/master/doc/problems.md
https://github.com/osmlab/fixing-polygons-in-osm/blob/master/doc/faq.md

If there is something unclear after reading them, please ask, and I am
happy to explain.

Jochen

On Fri, Mar 17, 2017 at 08:30:27AM -0400, john whelan wrote:
> Date: Fri, 17 Mar 2017 08:30:27 -0400
> From: john whelan <jwhelan0112 at gmail.com>
> To: Jochen Topf <jochen at remote.org>
> Cc: "hot at openstreetmap.org" <hot at openstreetmap.org>, Blake Girardot HOT/OSM
>  <blake.girardot at hotosm.org>
> Subject: Re: [HOT] Broken (multi)polygon cleanup
> 
> What isn't clear to me is just what you are trying to fix.  The term means
> nothing to me.  I am correcting duplicate segments and unclosed ways which
> appear to be part of your problem as I work.  Perhaps someone can explain
> what you are after in simpler terms because if we don't understand the
> problem then trying to come up with ways to avoid it in the future isn't
> going to happen.
> 
> Thanks John
> 
> On 17 March 2017 at 08:16, Jochen Topf <jochen at remote.org> wrote:
> 
> > Hi!
> >
> > I am sure there are many other problems, but can we please keep to the
> > issue at hand in this thread? I am not trying to solve all problems, I
> > am trying to solve one particular set of problem related to
> > (multi)polygons.
> >
> > And I didn't pick that particular problem at random. This is something
> > that affects everybody. The short of it is: Due to upcoming software
> > changes, some (multi)polygons that are rendered now will disappear from
> > the map or look different in the future. Again, you can find all the
> > details about the problems and of what we are trying to achieve at
> > http://area.jochentopf.com/ .
> >
> > We are having great success working on these problems. You can see the
> > stats at http://area.jochentopf.com/stats/ . This doesn't mean that the
> > approach will be the best one for other problems, and it doesn't mean we
> > can't do even better than we are doing until now with this problem.
> >
> > Btw: I am deliberately talking about "(multi)polygons". This is not
> > something that only affects multipolygon relations, but all polygons,
> > even the ones created from closed ways. They are simpler than mp
> > relations, but that doesn't mean they can't have problems.
> >
> > Jochen
> >
> > On Thu, Mar 16, 2017 at 05:23:47PM -0400, john whelan wrote:
> > > Date: Thu, 16 Mar 2017 17:23:47 -0400
> > > From: john whelan <jwhelan0112 at gmail.com>
> > > To: Jochen Topf <jochen at remote.org>
> > > Cc: hot at openstreetmap.org, Blake Girardot HOT/OSM
> > >  <blake.girardot at hotosm.org>
> > > Subject: Re: [HOT] Broken (multi)polygon cleanup
> > >
> > > This is similar to my pulling in Africa a country at a time and using
> > JOSM
> > > to check for errors.
> > >
> > > What I have noticed is one mapper will misstag then others will follow.
> > So
> > > sanitising the area or checking it for errors before the new HOT mappers
> > > start would probably improve the overall data quality as they tend to
> > > follow what is already mapped.
> > >
> > > Untagged ways by one mapper tend to cluster.  I've seen a 100 buildings
> > in
> > > one small area by the same mapper left as area=yes.  That's quick and
> > easy
> > > to fix.
> > >
> > > Recently I came across 42 highways left untagged by the same mapper in
> > the
> > > same area.  The mapper had more than 2,000 edits so wasn't inexperienced.
> > >
> > > Crossing highways often I'll see a town where the highway residentials
> > are
> > > laid out in a grid but the junctions aren't nodes.
> > >
> > > Another nice recent one was a batch of settlements that had been tagged
> > > highway=unclassified rather than landuse=residential.  Searching for
> > > highways above unclassified and crossing ways picked those out quite
> > > quickly.
> > >
> > > These types of errors are handled more quickly directly in JOSM than
> > > involving maproulette.
> > >
> > > Even the some other errors can be loaded up in the JOSM  to-do plugin.
> > >
> > > I've been cleaning up in Nigeria for a while now.  Making repeated passes
> > > over the same areas over time.  I'm seeing fewer errors so my suspicion
> > is
> > > the improved learnOSM, tutorials and simplifying what we ask mappers to
> > map
> > > is paying off.  Validating new mappers work within 48 hours does pay off
> > in
> > > data quality terms.  Giving feedback more than two weeks later is
> > usually a
> > > waste of time based on my own experience and Martin's report but I don't
> > > think we have the validators to do the validation within the magic 24/48
> > > hours.
> > >
> > > Broken multipolyons do take a level of expertise to resolve.  I usually
> > > avoid them.  However new mappers will fearlessly tread ahead and it is to
> > > be expected they will break some.
> > >
> > > I don't think learnOSM goes into detail about them or about
> > relationships.
> > > Should they?  That's another question.
> > >
> > > For some errors we need boots on the ground.  Especially when it comes to
> > > urban areas with limited access highways such as dual carriageways​ and a
> > > highway approaching them can you turn in either direction?
> > >
> > > Often the most motivated people to fix the errors are the locals who will
> > > be using the map.  Trouble is we first have to get something in place
> > that
> > > is useful to get them motivated.
> > >
> > > So yes HOT maperthons do have a reputation of the blind leading the
> > blind,
> > > ie some are led by inexperienced mappers but we are putting effort into
> > > reducing the number of errors.  The training group has put together a
> > very
> > > good detailed set of instructions on how best to run a maperthon and if
> > you
> > > can identify a problem area HOT will listen and try to address the
> > issues.
> > >
> > > Cheerio John
> > >
> > > On 16 Mar 2017 3:49 pm, "Jochen Topf" <jochen at remote.org> wrote:
> > >
> > > > Hi Blake,
> > > >
> > > > On Wed, Mar 15, 2017 at 05:29:04PM +0100, Blake Girardot HOT/OSM wrote:
> > > > > Can you send me something that would help me see those 1600 examples
> > > > > you found on OSM so I can see what might be going on and how to
> > > > > improve things in HOT/MM workflow to reduce them?
> > > >
> > > > Those 1600 are some very specific errors I am currently looking at, but
> > > > only have those on my local machine currently. But for the wider
> > picture
> > > > you can use the OSM Inspectors "area" view to see the scope of the
> > problem.
> > > >
> > > > Just go to any place where HOT/MM was active. Here is an example:
> > > > http://tools.geofabrik.de/osmi/?view=areas&lon=33.65927&
> > > > lat=-2.07600&zoom=8
> > > >
> > > > My current workflow is as follows: I choose one particular well-defined
> > > > problem and extract the data from OSM that shows this problem. Then I
> > > > put the data into Maproulette and document the problem and how to fix
> > > > it. Some problems are easier, some harder to fix. Mappers can choose
> > > > what problems to work on based on their skill level. If somebody
> > > > doesn't feel comfortable with one of the harder problems, there are
> > > > simpler ones they can work on. I also have some more general
> > > > descriptions for the experts who want to go exploring/fixing on their
> > > > own. Once the challenges are done, I choose a new problem and start the
> > > > process from the beginning.
> > > >
> > > > Here are the current challenges: http://area.jochentopf.com/
> > fixing.html
> > > >
> > > > Usually I am splitting up larger challenges into regions, for instance
> > > > by continent or country. I could also do this by HOT activation area or
> > > > so if that makes sense for HOT mappers. Splitting up, often makes the
> > > > problems easier to fix, because problems inside an area are often very
> > > > similar, but different to problems in other areas due to mapping
> > > > priorities and methods. For instance, some regions have lots of
> > problems
> > > > with buildings, others with landuse areas, etc. Concentrating on one
> > > > very well-defined problem at a time makes all this work simpler.
> > > >
> > > > Jochen
> > > > --
> > > > Jochen Topf  jochen at remote.org  https://www.jochentopf.com/
> > > > +49-351-31778688
> > > >
> > > > _______________________________________________
> > > > HOT mailing list
> > > > HOT at openstreetmap.org
> > > > https://lists.openstreetmap.org/listinfo/hot
> > > >
> >
> > --
> > Jochen Topf  jochen at remote.org  https://www.jochentopf.com/
> > +49-351-31778688
> >

-- 
Jochen Topf  jochen at remote.org  https://www.jochentopf.com/  +49-351-31778688



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