[mkgmap-dev] Debugging generated sea polygons

Fri May 21 20:49:13 BST 2010

On Fri, May 21, 2010 at 07:34:55PM +0200, Minko wrote:
>On osm it looks ok:
>http://www.openstreetmap.org/?lat=52.817&lon=4.955&zoom=10&layers=B000FTF

Someone mentioned that the sea polygons on the Mapnik layer are not 
updated at once. Mapnik is using old data that comes from a complex 
process, as far as I understood.

>Im using the geofabrik abstract from europe to compile my benelux map,
>Any idea how to fix this? I tried another abstract (planet-benelux) but 
>this gave the same results.

Extract the natural=coastline from your map extract or the individual 
tiles and check it in JOSM, using the Validator plugin. Pay attention to 
the "corners" or special looking lines or points. You may also find my 
wayselector plugin useful.  I wrote it for selecting the mainland 
coastline (there were quite a few natural=coastline islands and puddles 
around it on the Finnish coast, and I wanted to tag the puddles as 
natural=water).

>Is it caused by the splitter? Is it an error in de osm data?
>In the mkgmap args i use generate-sea: no-mp,extend-sea-sectors,close-gaps=1000
>and it never went wrong except for the last two weeks.

Pay attention to the mkgmap warnings. Enable logging and check the log 
file. See http://www.polkupyoraily.net/osm/ for an example (osm2img.sh, 
logging.properties, logging.ignore).

	Marko