[Tagging] Elevation and height on vertical features
dieterdreist at gmail.com
Fri Jan 8 11:00:03 UTC 2016
2016-01-08 2:30 GMT+01:00 Warin <61sundowner at gmail.com>:
> Grasping at straws .. the elevation of a mountain is given as its peak. If
> there is consistency within the map then the elevation of all objects
> should be their maximum height.
don't confuse elevation and height. Elevation is typically referring to the
ground. For a mountain, the situation is clearly different, it is the peak
we are mapping, not the mountain, because it is not even clear what a
mountain is (where it starts).
> We will also need to standardize on a datum for elevations. The wiki
> refers to both mean sea level (which varies by country) and wgs84. The
> differences might be enough to take the wheels off your plane..
> Good point there! :-)
> For most it won't matter. What do international planes use as there
> reference for height? Use that - again consistency.
why planes? If you fly a plane you have to have specific airspace maps,
nothing where OSM is particularily useful. Normally, maps are using
elevation indications in the national system. AFAIK, we have already
standardized elevation indications: they're * in WGS84 like all our data.
* well, they should be, typically the mappers read the elevation off some
sign and don't bother to convert.
PPS: Sorry, it isn't actually clear that WGS84 should be used, I have just
discovered that the "meters above sea level" indication has already been
introduced in 2008 in the post-vote-cleanup phase ;-)
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