[mkgmap-dev] missing coastline polygon lately

Wed Sep 8 06:50:58 BST 2010

On Wed, Sep 08, 2010 at 10:27:46AM +0800, maning sambale wrote:
>But this is a very interesting case because, previous builds have sea 
>polygons even when there are coastline errors. I'm using mkgmap svn 
>1649

Educated guess: previous errors canceled out each other (the errors must 
have been visible in a smaller area).

Unless your map extract is a perfect island, you may have to move the 
coastline endpoints to make mkgmap happy. When I successfully enabled 
coastline generation for Finland, I both adjusted the Geofabrik cutting 
polygon (it took a few iterations with Frederik Ramm) and moved the 
endpoints of the mainland coastline to the tile boundaries (so that the 
last bit of coastline is a straight N-S or W-E line). I played with the 
idea of merging real coastline of neighbour countries to the map, but 
that did not work out, and it would have been less obvious to see where 
the mapped territory ends.

Moving the coastline endpoints can be done with a trivial Perl or sed 
script. See my osm2img.sh at http://www.polkupyoraily.net/osm/ for an 
example. To find the endpoints of your map extract, you can extract the 
natural=coastline ways from your map extract and load that to JOSM.

	Marko