[mkgmap-dev] State of the coastline art

Wed Mar 31 08:30:42 BST 2010

On Tue, Mar 30, 2010 at 11:08:40PM -0800, NopMap wrote:
> - What level of confidence do you achieve with generate sea? Many posts
> still mention minor failures, disappearing islands etc.

As far as I am concerned, it just works.  Any errors will be logged and will
come through my error message filter.  You can fetch my scripts and files at
http://www.polkupyoraily.net/osm/ and adapt to your area.

Also, when debugging coastline errors (gap in coastline, coastline not
extending to map border), you may want to use a command like this:

osmosis --rx finland.osm.bz2 --tf accept-ways natural=coastline --used-node \
--wx finland-coastline.osm

The resulting file should be so small that you can load it in JOSM
to see the way and node ids of the broken coastlines.

> - Is it possible to save the resulting sea/land polygons for later re-use?
> Apparently the OSM data changes more frequently than the actual coastline
> and re-generating it from scratch every time you update is not necessary.

Generating the coastline is not that slow any more.  If you absolutely wanted,
I guess you could generate a separate map layer with just the sea, and compile
your regular map without --generate-sea.

	Marko