[OSM-talk] Fixing broken multipolygons

[Christoph Hormann]

On Friday 17 February 2017, Jochen Topf wrote:
>
> Lets not get this thread hijacked by theoretical ideas about how to
> detect wooded areas. This thread is about broken multipolygons.

I did not mean to hijack this thread, i meant to provide context for the 
decision on if to keep the imported wood/forest polygons.

> I'd rather have more specific challenges addressing
> exactly one problem, for instance "Broken multipolygons of certain
> types of landcover data imported from Corinne in Sweden". That is
> something I can extract from OSM data and that I can explain to
> people how to fix after consulting with local mappers on how best to
> do this.

In principle that is a good idea, for the Scandinavian wood/forest 
polygons however the problem would be that likely for a large fraction 
of the mappers willing and able to work on this the best solution will 
often be to delete the polygon in question.  This should of course not 
happen against the desires of the local community.  This problem is the 
main reason why i brought up the subject here.

In terms of specific challenges that might be useful - waterbodies is an 
obvious candidate.  There does not appear to be any specific 
concentration of broken waterbody polygons related to an import, most 
of these are genuine manual mapping errors.  Although many of these are 
also substandard in terms of mapping quality very few are so bad it 
would be better to delete them than to keep them.

Of course this task would be technically non-trivial, many of these 
polygons are large, a lot of big river polygons that should be split 
into smaller ones etc.

-- 
Christoph Hormann
http://www.imagico.de/