Hi, attached is the generator for precompiled sea data. Additionally you need some geotools libs (they are not downloaded by ivy). You can download it from http://sourceforge.net/projects/geotools/files/ The required libs are: commons-pool-1.5.4.jar gt-api-2.7.5.jar gt-cql-2.7.5.jar gt-data-2.7.5.jar gt-main-2.7.5.jar gt-metadata-2.7.5.jar gt-opengis-2.7.5.jar gt-referencing-2.7.5.jar gt-shapefile-2.7.5.jar jsr-275-1.0-beta-2.jar jts-1.11.jar vecmath-1.3.2.jar The generator can be started with java -cp <mkgmap classes dir> uk.me.parabola.mkgmap.sea.optional.PrecompSeaGenerator <shapefilename> <projection> <outputdir> shapefilename: the filename of the .shp file projection: WGS84 or any EPSG:xxxx outputdir: the directory to store the precompiled files The generator is not included in the mkgmap.jar file because the geotools libs are not automatically downloaded by ivy. If anyone can give an ivy dependency for the libs it is possible to change that. There are some performance settings that might be changed on your computer to better meet the memory/CPU settings of your computer. Have a look at the PrecompSeaGenerator constructor. The defined settings are ok for 3gb memory (-Xmx3g). WanMil