[Talk-us] Incorrect Summit Elevations - Colorado

[Mike Thompson]

It appears that there is a systematic error in the summit elevations
in OSM, at least in Colorado.  For example, Longs Peak is listed in
OSM as having an elevation of 4340 meters (14,239 ft).  The topo map
has it as 14,251 ft.  I have noticed the same type of issue with
nearby peaks.  I suspect this has to do with the GNIS import.  The
elevations in the GNIS are from the National Elevation Dataset (NED),
not spot (e.g. summit) elevations.  The NED gives the (presumably
average) elevation for a 3x3 arc second area.  According to the
metadata for the GNIS:

======================
Elevation figures are not official and do not represent precisely
measured or surveyed values. The data are extracted from the National
Elevation Dataset (<http://ned.usgs.gov/>) for the primary coordinates
and may differ from elevations cited in other sources. The differences
will be most evident for features such as summits where precision is
of more concern and where the local relief (rate of change of
elevation) may be more prominent. However, the elevation figures are
within tolerances for the data for most points and sufficiently
accurate for purposes of general information.
======================

Precise and official elevations are very important for hikers and
mountineers, or at least we like to think they are.

I believe that the National Geodetic Survey holds data on the official
elevations for summits within the U.S., but I need to look into that.
I am happy to start working on fixing this issue, but I didn't want to
commence if someone else is already working on.

Mike