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by zo1
3574 days ago
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I am guessing, but I don't think much of OSM's recent data is from GPS-samples. Roads don't pop into existence regularly, and when they do get built, my guess is someone adds them manually by referencing an underlying satellite layer. This probably doesn't apply to remote/rural/country-side areas, and for trails. In those cases, it's probably the other way around. |
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In OpenStreetMap areal imagery is a great help, but not the single source of truth. For mappers those images are a good starting point, but there are always other objects near it that can be used as a reference, so that new objects are placed relatively to it.
One single GPS trace is not very meaningful, but if you take several of them into account - optimally from different users with different devices - outliers become more visible and a smoothened path can be derived from it.
OpenStreetMap has a theoretical resolution of a centimeter, but in reality such a precision is not necessary as the devices that are used for consuming maps have a limited accuracy. So if the path is -/+ 5 m, that's fine for us.