Hi Ticker, cannot follow. When start and end are close the first iteration will find the most distant point and continue with the two intervals. Do you have an example *.osm file that shows how JOSM will "reduce a very long line to a very short line"? Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Ticker Berkin <rwb-mkgmap@jagit.co.uk> Gesendet: Donnerstag, 10. Juni 2021 10:07 An: Development list for mkgmap Betreff: Re: [mkgmap-dev] Wrong Douglas-Peucker implementation? Hi Firstly, the algo for DP when the start & end points are close but other points are more distant should be considered - maybe preserving the most distant points from the start & end or the points on the bounding box. DP using distance to line-through-points could reduce a very long line to a very short line if all the points are aligned. So, should stick with distance to line-segment Ticker _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev