The patch changes the way how subdivisions are splitted. 1.: The LineMergeFilter, the LineSplitterFilter and the PolygonSplitterFilter runs now before subdivions are built. This avoids the problem that single lines/polygons are bigger than allowed in one subdivision. ToDo: The filters parameters use very small values (e.g. 250 points for lines) which is only needed after a subdivision has been built. So maybe it is good to run these filters twice. First with subdivision limits before creating subdivisions and second after splitting each subdivision with lower RGN(?) limits. 2.: Subdivisions are no longer split in equal bounds sizes but into rather equal item sizes. ToDo: At the moment a too large subdivision is split into 4 subdivisions. This algorithm might be improved to compute it dynamically. Also points, lines and shapes should have a different weight in the split algorithm. This patch is a very early patch but if fixes the "Area (xxx,yyy) to (zzz,qqq) contains ... but can't be split further" messages. At the moment I am thinking about how to continue: Maybe it is reasonable to run an initial filter (filters that are not resolution dependant) set just before starting the subdivision creation. [This is what the patch already does.] The result of this filter set will not be changed afterwards and is used as input of each subdivision creation step. For each resolution the subdivisions of the previous resolution are copied but the contents are removed. Then the resolution dependant filter sets are applied (DP filter, SizeFilter, etc.) and the results are assigned to the subdivisions. As a last step too big subdivisions are splitted. [This swaps the current processing.] Possible problems: A line l in resolution 15 is subdivision A. l is splitted into 3 parts l1 to l3 in resolution 18. Is it necessary that l1 to l3 are assigned to child subdivisions of A or is it possible that e.g. l3 is assigned to a child B1 of subdivision B because the splitted line l3 fits better to B1? Are there any routing problems? I have found the thread http://www.mail-archive.com/mkgmap-dev@lists.mkgmap.org.uk/msg07335.html which indicates that my idea does not work. WanMil