[Tagging] Antwort: Re: Aerialway stations

[Colin Smale]

On 2020-08-13 18:35, Werner.Haag at leitstelle.tirol wrote:

> Hi, 
> 
> in my opinion (i think dktue is right there) it should be easy for a user to distinguish or extract (overpass query) the upper, mid and lower stations. 
> That´s not possible at the moment in OSM. Elevation (ele tag) may be useful, but does not indicate whether a station is the lower or upper one. 
> On the other hand, a tagging with upper_station or lower_station is clear and self-explanatory.

It would also be a denormalisation of the data. In SQL terms you would
use a subquery like "WHERE ele = MIN(SELECT ele FROM stations WHERE...)"
although I suspect the usual use case will be looking for the whole
line, so a simple "ORDER BY ele" would give you all you need to know -
bottom station is first row, top station is last row, rows 2..n-1 are
mid stations. This would avoid any possibility of conflicting
information, e.g. multiple stations tagged as top, or the station with
the lowest elevation being tagged as top station. 

All this is based on the assumption that the definition of the top
station is the one with the highest altitude.... If any other factors
are in play that could mean that this definition does not always hold
true, then I am keen to hear.... It's best to check assumptions, even
(especially?) if they do appear obvious.
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