[Tagging] Elevation and height on vertical features

[Greg Troxel]

Mike Thompson <miketho16 at gmail.com> writes:

> On Fri, Jan 8, 2016 at 9:47 AM, Colin Smale <colin.smale at xs4all.nl> wrote:
>>
>> How did all the elevation data get into OSM in the first place?
>>
> The elevations of peaks in the US came from the GNIS import.  In turn the
> GNIS elevations came from the National Elevation Dataset (NED) [1], and it
> mostly uses the North American Vertical Datum of 1988 [2]. The other
> problem is that these are not "spot elevations" and therefore the elevation
> of a peak in the GNIS does not - in most cases - match the official
> elevation (the ones shown on the old USGS Topo maps and published by the
> National Geodetic Survey[3]).
>
> [1] http://nationalmap.gov/elevation.html
> [2] http://www.usgs.gov/faq/categories/9865/4921
> [3] http://www.ngs.noaa.gov/datasheets/

Perhaps it would be a good project, perhaps via maproulette, to spiff
this up.  It can be tricky, though, because the benchmarks on mountains
are not always the exact summit -- I actually found the mark on
Mt. Washburn in Yellowstone, and I don't think it matches the mountain
height.  But I get it that the USGS surely publishes mountain heights
somehow.

I do see that WGS84 heights and NAVD88 heights are off by part of a
meter east coast up to 2m in Washington State.  Still, I think data with
those kinds of errors is far better than no data.
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 180 bytes
Desc: not available
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20160108/d2e5d165/attachment.sig>