[OSM-talk] Islands that will vanish in the license change

[Toby Murray]

Thanks to Paul Norman's efforts and visualizations based on it[1],
there has been a lot of activity in remapping coastlines lately and a
lot of improvement. However one loophole that Paul's method does not
detect is islands that will have their coastlines vanish completely. I
decided to take a look at this tonight. So far I have come up with a
pretty hackish way of looking at things... but I think it might still
be of use.

I downloaded all natural=coastline ways from my jxapi. Then I split
the world into 4 parts to make them small enough for me to open in
JOSM. Then I selected all objects that were last touched by an
accepting user and purged them from the data set. What is left is all
ways that were last touched by a decliner. Some of these are actually
OK from a license standpoint. Maybe the decliner just deleted a tag or
added some nodes in the middle of a way which will obviously distort
the geometry but the coastline topology will remain intact so they
don't show up in Paul's files. Also, some things that I purged may
still be heavily impacted or even completely removed by the license
change if they were created by a decliner but last touched by someone
else. So it isn't perfect.

The south/west quadrant of the world is actually pretty much good to
go. I already fixed a few islands. The north/west one is still a
little large so I may have to do some more tinkering there. The one I
have ready to go right now is south/east (Australia) and I saw this
topic come up in the talk-au archives a few days ago so I thought I
would go ahead and share. Perhaps someone who is subscribed to talk-au
can forward this?

What I have is a ~10MB .osm file containing 537 ways (plus some stray
nodes that should just be ignored):
http://ni.kwsn.net/~toby/OSM/coastline_SE_bad.osm.gz
This file covers from the equator to the south pole and from 0 to 180
longitude so it is more than Just Australia although that is the most
impacted area.

The way to use this would be to download it and open it in JOSM. Then
do a "type:way" search and run the license plugin on that. Then just
look for the big red blobs. DO NOT use this layer to edit and upload
or terrible things are likely to happen. Use it only as a guide to
find trouble spots. I set the upload=false flag in the file so JOSM
should be very clear about this if you try to upload from this layer.

So download a problem area to a new layer and replace dirty coastlines
to your heart's content. The biggest blob of red is on the northeast
side of Australia. Some of them are random rocks along the coastline
that cover a few square meters. Some are large islands. Unfortunately
it looks like Bing isn't good enough to retrace some of these but I'm
hoping the locals may have other sources.

Enjoy,
Toby


[1] http://www.wightpaths.co.uk/coast/CT-only.php