Hi Ticker, I first convert the gpx layer to a data layer, then add the tag natural=water Next execute validator which will complain that the way is not closed. Right click on that warning allows to "zoom to problem" . This tells you where the first point is. In the "OSM data" preferences I've enabled "Draw segment order numbers on selected way" Hope this helps. Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap@jagit.co.uk> Gesendet: Donnerstag, 27. Mai 2021 14:21 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] special case where splitting fails without a log message Hi Gerd Trying to use JOSM to decide if a gpx trace represents a self -intersecting polygon is difficult. Is there a way of forcing it to consider it closed and then check itself? Failing that, number the points or segments somehow. Ticker _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev