As someone not happy about the deprecation of mailinglists, a few brief
comments here:
First, I think this proposal is fine, as documenting widespread
practice. Regardless of my further comments, I think it's solidly
progress to adopt it.
While yonur comments about survey feet are valid, modern elevations
(NAVD88) are as far as I can tell actually in meters, and when
expressed in feet, in international feet. Elevations are small enough
that 2 ppm is less than the errors in the values.
I would expect the proposal to give an example. It seems that one
would have a tag
ele=6288 ft
for Mount Washington (showing my East Coast bias).
It would be good to explicitly state that in keeping with convention,
ft means international feet, perhaps with a parenthetical comment that
if someone meant US Survey Feet they would have written ftUS. Maybe
this is already documented.
There is a much more serious problem in that few seem to understand
that elevation is only meaningful relative to a vertical datum. OSM
documents WGS84. Even fewer understand that this is a mess because
WGS84 is an ensemble containing a low-accuracy member
(WGS84(TRANSIT)), and that the only reasonable interpretation is that
data should be expressed in the most recent realization.
Further, WGS84's first height definition is ellipsoidal height, and
that simply is not elevation. Obviously elevation should be in "WGS84
Orthometric Height", which is what GPS receivers provide as elevation.
But elevations are not published in WGS Orthometric Height; they are
published in a national or regional datum which is pretty close, as
all datums at least roughly target a similar origin.
Practically, people type in numbers from a sign, and this sign was
probably copied from some earlier sign, and may be in some ancient
datum, and may have been erroneous. This proposal has no bearing on
that, and that's ok.
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