Hi Bernhard, I recently made a few new tests with an old release of phyghtmap (the release 1.47 tested §4.3 Windows Installation, see http://katze.tfiu.de/projects/phyghtmap/) A comparison between hgt2osm and phyghtmap (1.42) is given at this link: https://drive.google.com/file/d/1loWwr6JE9wq1rORKWae7CNAqn0t3h62L/view?usp=s haring We also can see cut contour lines only at 0°. But phyghtmap don't generate horizontal lines. IMHO I think that this little issue could be easily solved by Frank Stinner the developer of hgt2osm. I tried to send him an email about these "artefacts" near 0°, hopping the email addresses are correct and in usage. fstinner at gmx.de frank.stinner at kabelmail.de Best regards, Gerard De : mkgmap-dev [mailto:mkgmap-dev-bounces@lists.mkgmap.org.uk] De la part de Bernhard Hiller Envoyé : vendredi 11 mars 2022 17:23 À : mkgmap-dev@lists.mkgmap.org.uk Objet : Re: [mkgmap-dev] Contour lines with "Artefacts" near a vertical line situated at W0° 00' 00" Hi Gerard, you can check the elevation contour lines by opening the file generated by your tool in e.g. JOSM (my take some time when the file is large). Strange distortions are expected at the borders of the whole set of input files, but not where input files are adjacent to each other. Your description seems to hint to a bug when crossing the 0°-meridian. I do not know how srtm2osm reacts there, it might be worth to try it. Kind regards, Bernhard Am 10.03.2022 um 14:15 schrieb Gerard CATTIAUX: 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> 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> 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= sharing> 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