Hi Apollinaris,
- run splitter, but the input doesn't contain a bbx so it's required to insert the bbx in the osm file. haven't tried this part and don't know if splitter uses bbx in the incoming osm file. as alternative adjust the areas.list for splitter to the bbx used in osmosis. otherwise some tiles will have nearly empty areas caused by long ways extending the osmosis boundary. currently splitter doesn't include complete relations maybe mkmap can close polygons correct but I doubt it. in general a polygon can be closed. left or right along the tile boundary. only for coastline this can be solved by analyzing the direction of ways. for a relation based polygon there is a 50% chance.to get it correct.
I did submit a request for the splitter to support a bounding box option that would bound the outer edge of the tiles (rounded appropriately) but Chris didn't seem keen about that. Personally, I think it would be useful. Mark