Hi Gerd and Bernhard, I made a lot of complementary tests that are still in progress to try to understand the issue. Among these tests, the main results are: 1) Just after the conversion of one elementary tile (ex: N45W001.HGT ) with hgt2osm, I can see the artefacts when I edit "mycontour.osm.pbf" with JOSM. 2) I generate contour lines for a large surface comprising Benelux and France, except a vertical band around 0% (see: https://drive.google.com/file/d/1r3v3UBc_Cfdm2vw1VepIvN3oM1JJVBp3/view?usp=s haring NB: I use Data from SONNY https://data.europa.eu/data/datasets/dtm-europe?locale=en), because they are for me the best data for Europe, data are from 2021 and comprising LIDAR measurement. --> The result after: All the contour lines are perfect. I don't see any problem !! 3) I generate contour lines for the vertical band around 0° In France and a local zone in SPAIN --> The Result: All contourlines have the Artefact at 0° 4) I choose also to generate contourlines from an another source of DEM data for France around 0° (ALOS data from Japan Aerospace https://www.eorc.jaxa.jp/ALOS/en/index_e.htm) --> The Result : Contourlines have all the same artefacts, just after conversion with hgt2osm. It is very clear for me, that SPLITTER and MKGMAP do perfectly their jobs. For now, I will try to have a look on using osm2srtm, but I am not sure that it is possible to have the choice to use the recent data from SONNY as input files !! Best regards, Gerard -----Message d'origine----- De : mkgmap-dev [mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk] De la part de Gerd Petermann Envoyé : vendredi 11 mars 2022 11:34 À : Development list for mkgmap Objet : Re: [mkgmap-dev] Contour lines with "Artefacts" near a vertical line situated at W0° 00' 00" Hi Gerard, I don't know the program hgt2osm, I would suggest to contact the author or try one of the alternatives like srtm2osm or Phyghtmap: https://wiki.openstreetmap.org/wiki/Srtm2Osm https://wiki.openstreetmap.org/wiki/Phyghtmap Or do you think that the generated OSM data is okay and it is mkgmap that fails? Gerd ________________________________________ Von: mkgmap-dev <mkgmap-dev-bounces@lists.mkgmap.org.uk> im Auftrag von Gerard CATTIAUX <gerard-mkgmap@gmx.com> Gesendet: Donnerstag, 10. März 2022 14:15 An: mkgmap-dev@lists.mkgmap.org.uk Betreff: [mkgmap-dev] Contour lines with "Artefacts" near a vertical line situated at W0° 00' 00" Hello, After many hours of time to get a correct knowledge of the most important tools needed to produce Garmin map, like mkmap, Splitter.. and plenty of hours to develop my own Styles files for mkgmap, I am now able to produce local maps mainly for Fenix 6x or Garmin 66, specifically for Trail Running. That help me also to have a mean to verify immediately all my contributions to OSM database. To have the best results for my personal maps, I use altitude data from Sonny. https://data.europa.eu/data/datasets/dtm-europe?locale=en For flat part of the country, I generally generate contour lines with a 5m space, in lieu of a 10m or 20m space between contours lines. That choice seems for me a very good choice for as an example "Ile de France" (Extended Region around Paris), where max altitude are between 150 to 200m. I recently generate contourlines near La Rochelle in France for a local zone called "Poitou-Charentes", http://download.geofabrik.de/europe/france/poitou-charentes.html but unfortunately, I have artefacts, that I don't have for example in many other regions of France. These artefacts are also visible for 5m, 10m and 20m space between contours lines. These "artefacts" are described in the pdf files given at this link: https://drive.google.com/file/d/1uiA51R4Kd_WYsdeTrEtevu2jJ_8aPinH/view?usp=s haring To generate my contour lines, I use mainly hgt2osm, with hgt files from Sonny. Hgt files in the example : N46W002.zip N46W001.zip N46E000.zip N45W002.zip N45W001.zip N45E000.zip Command line hgt2osm -g HGT-AFAIRE --MinorDistance=10 Hgt2Osm, 13.11.2017, FSofT 64 Bit-OS: ja Programmodus 64 Bit: ja MinorDistance: 10 MediumFactor: 5 MajorFactor: 5 HGT-Verzeichnis: HGT-AFAIRE Mergefile: OutputOverwrite: False Höhenkorrektur: -0.5 MinVerticePoints: 3 MinBoundingbox: 0.0005 Douglas-Peucker: 0.04 1. OSM-ID: -1 mit OSMBound: False mit OSMBounds: True mit OSMTimestamp: True mit OSMVersion: 1 mit OSMVisible: False max. Punktanzahl je Weg: 500 mit 'contour_ext'-Tag: True At first sight, it seems that all these artefacts begin just near a vertical line situated at W0° 00' 00" / E0° 00' 00" Any ideas to helps me to solve the problem? Many thanks Regards Gerard Cattiaux _______________________________________________ mkgmap-dev mailing list mkgmap-dev@lists.mkgmap.org.uk https://www.mkgmap.org.uk/mailman/listinfo/mkgmap-dev