[Tagging] Elevation and height on vertical features

Greg Troxel gdt at ir.bbn.com
Fri Jan 8 20:22:48 UTC 2016


Mike Thompson <miketho16 at gmail.com> writes:

> [1] do care about the "official" elevation of mountains.  I think OSM
> should - in these cases - match official government surveys where
> available.

Fully agreed that it should be right.

> The particular datum is not important, as long as it is known,
> as someone making a map from OSM can convert to the datum they are
> interested in.

Mixed datums is a mess in the data model.  Would it be ok if I added
some roads and used NAD27 coordinates instead (~40m off near me), and
put in some label that it was in NAD27?  (I realize that horizontal is
fixed in the schema and vertical is a tag so this is not
straighforwardly doable; it's an artifact of the 2.5D nature of OSM that
we are even able to have this discussion.)

But I can see that you would want to record "US Government says the
elevation is 10248 feet NAVD88, or even in meters these days".  That's
then not really the ele tag, but something similar, and it may be that
having a tag to represent published elevation data with source and datum
could make sense, and also have WGS84 elevation in ele.
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