Hi Jean-Daniel
Technically I wouldn't expect the numbers to be exactly the same, as the elevation in OSM needs to be metres above above mean sea level as defined by the EGM96 https://en.wikipedia.org/wiki/EGM96 geoid model. This is unlikely to really differ a lot, but should be taken in to account, if you see differences that are in the 30-50 m range then they are likely values above the GPS ellipsoid (and should be corrected). See https://wiki.openstreetmap.org/wiki/Key:ele https://www.swisstopo.admin.ch/en/maps-data-online/calculation-services/navr... might help with checking this.
Are you actually using the 1:25'000 map? If yes I would use Carte Nationale SwissTopo and add the scale. On the other hand I'm fairly sure their https://www.swisstopo.admin.ch/de/geodata/landscape/names3d.html dataset includes elevations too (general warning about the swissnames dataset, the names need to be taken with a lot of salt, don't use them without checking locally first).
Simon
Am 15.09.2021 um 07:43 schrieb Jean-Daniel Bonjour:
Je constate souvent que certaines altitudes (montagnes, cols...) dans OpenStreetMap sont très imprécises, c'est-à-dire présentent plusieurs mètres de différence par rapport à la carte nationale SwissTopo.
Donc question concrète : si je corrige ces altitudes erronées dans OpenStreetMap, dois-je ajouter au sommet/col l'attribut "source=SwissTopo" ? Ou est-ce suffisant que, lorsque j'upload le changement, je mette juste dans le champ "Specify the data source for the changes" (j'utilise JOSM), le commentaire "Carte Nationale SwissTopo" ?