A particularly nasty variant of armchair mapping: "Mapping from the newspapers".
When the local media announces changes that have been recently voted by local councils, some enthusiasts reflect those in OSM… sometimes years before they are effective.
Streets changing names, extension of pedestrian plazas, mergers between large firms, speed limits…
Possible mitigation: use the "note" key to add a short warning.
@bxl_forever A related and recent discussion on talk-fr mailing list about adding future buildings in #OpenStreetMap: https://email@example.com/msg91389.html Key elements, off the top of my head: possible intellectual property on architects plans and what is built is not necessarily what was planned. OSM has tags for future stuff. See "proposed" and "dates" namespaces: https://wiki.openstreetmap.org/wiki/Lifecycle_prefix.
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