[Talk-us] Incorrect Summit Elevations - Colorado
aschoell at gmail.com
Wed Feb 10 06:04:50 GMT 2010
Have seen it too in California. It's not only the elevation also lat/lon is wrong for many summits.
If there is any better source correct it. I verify it by gps and topo 24k and yahoo. If there is any official and better data I am all for replacing GNIS data.
On 9 Feb 2010, at 19:35 , Mike Thompson wrote:
> 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.
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