Hi Ticker, please see https://files.mkgmap.org.uk/detail/513 This is what I get: D:\mkgmap>java -ea -jar dist\mkgmap.jar e:\osm_out_work\norway\20210511_095323\63240001.o5m Mkgmap version 4763 Time started: Thu Jun 10 10:50:35 CEST 2021 SCHWERWIEGEND (Polyline): e:\osm_out_work\norway\20210511_095323\63240001.o5m: Problem writing line (class uk.me.parabola.imgfmt.app.trergn.Polygon) of type 0x16 containing 30 points and starting at http://www.openstreetmap.org/?mlat=62.987366&mlon=-1.137106&zoom=17 SCHWERWIEGEND (Polyline): e:\osm_out_work\norway\20210511_095323\63240001.o5m: Subdivision shift is 0 and its centre is at http://www.openstreetmap.org/?mlat=62.263577&mlon=-1.478584&zoom=17 SCHWERWIEGEND (Polyline): e:\osm_out_work\norway\20210511_095323\63240001.o5m: deltaLat = 33731 Number of MapFailedExceptions: 0 Number of ExitExceptions: 0 Time finished: Thu Jun 10 10:50:48 CEST 2021 Total time taken: 13 seconds I've not looked at all the details, but the polygon overlaps the inital area extremely. The attached patch fixes the problem but I have not tested any side effects. Gerd