Hello, I compiled geofabrik.de Ireland OSM data with mkgmap (I made my tests with source code downloaded 2010/12/17) and the sea is generated only for one tile with "generate-sea=multipolygon,close-gaps=1000"but works well with "generate-sea=multipolygon,extend-sea-sectors,close-gaps=1000" ! With mkgmap version from august, it works well. Did you change an option for sea generation ? I also found two small problems with mkgmap's options : Option -version does not display a number but "svn". This is the same with old version (since 156x, I think) While I noticed you changed some options name, I found a annoying change : when mkgmap meets an option which is not needed for compilation phase, it stops with an error message like "invalid option". This happens only with "product-version" option. Thank you for your great job, David