Is there documentation on type=drainage_divide? I was looking for it, but could not find it.

Concerning the Alpine Watershed relation/14461262, they tagged the ways with type=boundary and boundary=geographical where they did not use administrative borders to approximate the drainage divide.

Regarding the resuse of existing ways, it is something that I have considered, but decided against, because I assume that it will create issues:
- Particularly where ridges are oriented normal to the major direction of the divide, the typically leaves the ridge somewhere to follow the valley divide to the next ridge. Therefore, we would need to split existing continuous ridges even if these are named, have Wikidata and Wikipedia, and Wikidata referenecs the ID of the ridge way. A pattern that we do also observe quite often is the divide running up a hill and running down again at an angle < 90°.
- Reusing ridges will significantly increase the amount of relation members
Elsewhere, relations do also often not resuse existing ways, but only the notes. For example forest and meadow relations typically do not use road ways and even if forest and meadow share a boundary line, they do nevertheless use distinct ways for their boundary lines.

I would assume that they guy who mapped the Alpine divide got it wrong. Only Americans use the watershed term for a drainage basin. For normal English speakers, it is synonymous with drainage divide. But the OSM concept of watershed is understanding it the AE way.

Hi,
The type=watershed tag is obviously used for relations on drainage systems of rivers which collect all the waterway ways within the main stream's drainage basin. What I mapped is a drainage divide. It is the line of division between two adjacent basins. If there is established tagging for a drainage divide, then please provide the reference.

Thanks. Then let's put the vertex there: changeset/176019379

Is this the vertex at 1972 m?

https://s.geo.admin.ch/rfpqunaneuor

This would mean that it is only about 8 m below terrain level.

Hi Cele, at the location close to the geographical col, where the pass vertex was located before, the elevation is 1917 m according to the cited data source. The source tends to provide quite accurate data. At the current location of the pass vertex, the elevation is 1937 m. Even closer to the tunnel entrance, the road might be higher, but I cannot rule out that the elevation reading from my source is influenced by the surrounding terrain. Therefore, I would see this change as an attempt of improvement. If you have access to more accurate data or know the elevation profile inside the tunnel, feel free to move the vertex to the de facto highest point of the road.

Hallo Bergfrei,
die Bank werde ich wohl verschoben haben, damit sie auf der gleichen Seite des Weges bleibt. Ich habe sie nach Augenmaß verschoben und nicht nachgemessen. Wenn sie zu weit abseits ist, dann rücke sie einfach wieder näher an den Weg.

Obwohl die Qualität der Luftbilder besser geworden ist, besteht insbesondere im Gebirge nach wie vor das Problem, dass die Aufnahmen in den meisten Bereichen verzerrt und verschoben sind. Deshalb lässt sich aus einem Luftbild meiner Meinung nach bestenfalls der relative Verlauf eines Weges ablesen. Die Position wird von GNSS in der Regel besser wiedergegeben.

Luftbilder zeigen außerdem immer die Vergangenheit. U.a. erosionsbedingt ändern sich Wegverläufe im Gebirge aber immer mal wieder.

Abweichungen von Luftbildern sind übrigens normal. Luftbilder sind praktisch immer verzerrt und verschoben.

Die Quelle ist doch abgegeben. GNSS = Global Navigation Satellite System. GPS ist nur das US-amerikanische. Mein Gerät nutzt aber weitere, wie z.B. Galileo.