[OSM-talk] Coastline updates

[Paul Norman]

> From: Jochen Topf [mailto:jochen at remote.org]
> Sent: Friday, November 22, 2013 1:51 AM
> To: Paul Norman
> Cc: talk at openstreetmap.org
> Subject: Re: [OSM-talk] Coastline updates
> 
> On Thu, Nov 21, 2013 at 09:24:46PM -0800, Paul Norman wrote:
> > > From: Jochen Topf [mailto:jochen at remote.org]
> > > Sent: Monday, November 18, 2013 8:13 AM
> > > To: talk at openstreetmap.org
> > > Subject: [OSM-talk] Coastline updates
> > >
> > > Hi!
> > >
> > > For the last about two weeks we haven't gotten any coastline updates
> > > through. The problem is that every day there is something broken
> > > somewhere with the coastline. Often problems get fixed the same day,
> > > but new problems show up the next.
> >
> > Can't osmcoastline localize these problems to a small area? Coastcheck
> > kept any errors from impacting entire continents, even when there were
> > high numbers of errors. I remember it finding 2k errors when I started
> > running it regularly!
> 
> Osmcoastline fixes small gaps in the data. I don't know of anything more
> coastcheck did. If anybody can give me any algorithms how to fix the
> data or "localize these problems", please do.

A particular square (400x400 mercator km, I think) containing coastline can 
be evaluated without considering the rest of the continent thanks to the 
directionality of coastline ways mattering. You'd periodically get squares 
that would end up incorrect, but it wouldn't generally cause incorrect
results
outside that square.

I don't know any details of the algorithms used since I didn't write or
maintain
them, I just know the results.