On 24/09/2018 07:03, Joseph Eisenberg wrote:
Right! Especially on my island, New Guinea.
That’s why we need to check the height of saddles and peaks “by hand”, or
better yet by survey with GPS.
OSM is the right place for this data, and some map styles and database users
will find it useful to analyze data about mountain areas and peaks.
For example, even those lists of “tallest peaks” actually use topographic
prominence as a cutoff. Otherwise the highest peaks on Earth would all be rocks
and bumps on the slopes of Everest.
Most of us just estimate the prominence of a peak intuitively, before
choosing to add one to the map. Clearly, a 5 meter tall bump isn’t a peak.
Perhaps a 10 meter rise may have a name in England or Denmark, where mountains
are scare. In other contexts a peak won’t be named unless it is 100m or 200m
above the nearest saddle on a ridge.
Joseph
On Mon, Sep 24, 2018 at 12:59 PM Yves <[email protected]> wrote:
I don't see no issue in mapping prominence for those interested in.
Just to mention for the sake of the discussion that 'sufficiently accurate
DEM' doesn't exists globally.
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few points on this thread: * Prominence has been added for every significant
peak in Scotland (along with which hill-bagging group they are members of). The
peaks called Marilyns (a play on the more famous Munros - peaks over 3000 ft)
are entirely based on prominence, and are sufficiently well known in the UK to
have a guidebook. Overpass query: http://overpass-turbo.eu/s/Cbi * What Michael
describes sounds very much like something close to topographic isolation
(https://en.wikipedia.org/wiki/Topographic_isolation). Co-incidentally I looked
at calculating something like this after a recent conversation with Stefan
Keller (prompted by a wikipage on Dominance:
https://wiki.openstreetmap.org/wiki/User:Maxbe/Dominanz_von_Gipfeln). I simply
calculated the closest, higher peaks for all Swiss peaks and then filtered by
that distance (e.g. over 5 or 10 km). This produces a reasonably good
distribution of peaks (see
https://www.dropbox.com/s/qoe2y9d6n6pjh0c/ch_peak_iso.jpg?dl=0), and can
obviously be adjusted by other parameters. * One problem with prominence is
that it is probably most easily obtained from non-open sources (such as those
used to populate wikipedia), and equally there is temptation to use copyright
maps for information on saddle points. For the peaks with a very significant
prominence (say 1000 m or more) this is less of a problem as most can be
deduced very quickly. * Peak names can be an issue when the high point is part
of a group of peaks with an encompassing name (Dufourspitze Monte Rosa,
Breithorn Occidentale/Westgipfel comes to mind). The Matterhorn traditionally
has 2 summits (the Swiss & Italian ones), but only one is mapped, avoiding this
issue for that peak.
* Many peaks which sit on national boundaries are not on located as part of
the border way on OSM, and may therefore not be included in peaks with a
country filter. There are several examples near Zermatt. Thanks to Kevin Kenny
& others who have pointed out the theoretical value of prominence. Jerry
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