You need to install quite sime C, C++ and java libraries and binaries. So without root access, it will be difficult, because you have to recompile everything and install it in your home directory.
The process is in short:
- get current planet file or update your local copy - osmcoastline -i -f -p land -o coastline.db planetfile.osm.pbf (if return value is 0 or 1, continue, else abort and fix the errors first) - ogr2ogr -f "ESRI Shapefile" land_polygons.shp coastline.db land_polygons - mkgmap_sea_generator land_polygons.shp WGS84 sea-$NEXT (mkgmap_sea_generator is a script calling the mkgmap java function)
sea-$NEXT contains now the new precomp sea data.
I was playing around with ogr2ogr (and ogr2osm) on my Windows machine a while ago. So I know how complicated and time consuming it is to set up gdal based things. Providing precompiled sea might be a task for someone who is more familiar with this. Is http://www.navmaps.eu/wanmil/ the only source available for precompiled sea or does someone have a more recent one?