Hi Gerd, Tried lowering max-nodes value from 150000 to 6500 which reduced but didn't stop the errors. I think that the cause is that within the 1685341 codes in the Ordnance Survey CodePoint data sometimes many different Postcodes are at the same coordinates. On analyzing can see a max of 1327 postcodes at the same co-ordinates in London, and others with hundreds of postcodes at the same coordinates in e.g. Cardiff. These postcodes in London belong to PO Boxes and in Cardiff to massive UK Government office complexes like the Benefits Agency departments. And I found several hundred Postcodes without meaningful coordinates in the list too, which were "parked" in the middle of the Atlantic (being OSGB36 0,0). But if I'd read the spec. I'd have filtered them out beforehand as they are clearly marked. Have you any idea what might be a reasonable number of points to share the same coordinates without breaking mkgmap? As coincident postcodes are usually (but not always!) within sensible alphanumeric series like NW26 9HB, NW26 9HC etc I plan to analyse duplicate code coordinates and just remove the last 1 or 2 characters from the Postcode to minimize or eliminate those with duplicate coordinates. Cheers, Peter