Am 13.08.2020 um 19:06 schrieb Colin Smale:
On 2020-08-13 18:35, Werner.Haag@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.
Your assumption is true. The upper_station is the one with the highest
altitue whereas the exact altitude is not always known by mappers.
Just to put it in perspective as a mapper from Tyrol joined the
discussion: In Tyrol alone (less than 10% of Austria's population) OSM
shows more than 1000 (!) aerialways [1] and for probably each of them it
would be pretty obvious to tag lower_station and upper_station. I think
aerialways that go horizontal are an absolute niche. So why oppose to
the suggested tagging of
station=lower_station/mid_station/upper_station? What harm would this cause?
[1] http://overpass-turbo.eu/s/X2M
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