[Tagging] Topographic Prominence for Peaks

Peter Elderson pelderson at gmail.com
Sun Sep 23 05:10:35 UTC 2018


Edi & change status, I would say. Seems a pretty clear case, just maybe not
something many mappers or users are very concerned with. But that's not a
problem as long as there is a clear definition, solid data and a steady
group of mappers/users. I would say, just do it and document it.

Op zo 23 sep. 2018 om 03:05 schreef Joseph Eisenberg <
joseph.eisenberg at gmail.com>:

> For most peaks, it's only necessary to know the elevation of the
> nearby saddles and peaks to find the prominence. For example, walk to
> the top of the hill and record the elevation. Look around and find any
> taller nearby peaks. If there is only 1 taller hill, walk down the
> ridge line to the lowest point between the first hill and the taller
> hill, then record the saddle elevation. Prominence is then elevation
> of the first peak minus the elevation of the saddle.
>
> It's more difficult for very prominent peaks, where the "key col" or
> lowest saddle may be 1000's of kilometers away, but all of these peaks
> already have prominence calculated and listed on Wikipedia:
> https://en.wikipedia.org/wiki/List_of_peaks_by_prominence,
> https://en.wikipedia.org/wiki/List_of_islands_by_highest_point,
> https://en.wikipedia.org/wiki/List_of_Ultras_of_Africa
>
> I just remembered that there was an abandoned proposal for this tag.
> How do I revive the proposal? Just start editing the page,
> https://wiki.openstreetmap.org/wiki/Proposed_features/key:prominence
> Or make a new page?
>
> Joseph
>
> On 9/23/18, Warin <61sundowner at gmail.com> wrote:
> > On 23/09/18 10:00, Joseph Eisenberg wrote:
> >> I've been tagging peaks (natural=peak) with the key
> >> prominence=<topographic prominence in meters>
> >>
> >> Prominence is a natural feature with a use similar to elevation. When
> >> I see ele=*, I know how high the top of the peak is, but not how tall
> >> the peak is compared to the surrounding land. For example, a hill in
> >> my valley may have ele=2000m, but it isn't a mountain: it's a 300m
> >> hill that rises out of surrounding land at 1700m.
> >>
> >> Prominence is calculated by subtracting the elevation of the lowest
> >> saddle (or "col") from the elevation of the peak:
> >>
> >> https://en.wikipedia.org/wiki/Topographic_prominence
> >>
> >> "The prominence of a peak is the minimum height necessary to descend
> >> to get from the summit to any higher terrain" or "the height of the
> >> peak’s summit above the lowest contour line encircling it but
> >> containing no higher summit within it."
> >>
> >> Both of these definitions are the same for all peaks except for the
> >> highest peak on a landmass, eg Mount Everest in Eurasia: in this case
> >> use the second definition, which means that the tallest peak on a
> >> (super-)continent or island is the same as it's elevation.
> >>
> >> This started when I became interested in "peak bagging", where hikers
> >> and climbers record the peaks they have summited. There are separate
> >> categories based on the prominence of a peak. Gunungbagging.com in
> >> Indonesia lists elevation, prominence and names for many peaks here in
> >> Indonesia, and the site authors gave permission for the data to be
> >> added to Openstreetmap.
> >>
> >> There are other lists of prominent peaks for the rest of the world,
> >> but please check if you can use the data based on the license, before
> >> adding it to OSM.
> >>
> >> Elevation and prominence can both be calculated from SRTM data, eg by
> >> using Opentopomap tiles and finding the highest contour lines around a
> >> peak, and the lowest near a saddle.
> >>
> >> Prominence and elevation can be calculated by computer with good data,
> >> but for my part of the world the SRTM data is not high enough quality
> >> to get good results without cross-checking against aerial imagery.
> >> Also the calculations are not simple, and are not precise for sharply
> >> pointed peaks or deeply carved saddles, therefore I believe it will be
> >> useful to include this data directly in tags.
> >>
> >> I also find that calculation the prominence of peaks has encouraged me
> >> to add more ridge lines and saddle points (with elevations), which
> >> should make the database more useful in mountainous areas.
> >>
> >> Do you think I should write up a formal proposal for this tag?
> >>
> >
> > Yes to documenting it.
> >
> > The evaluation of 'prominence' would be to some local area .. what is the
> > size of that area?
> >
> > ----------------
> > Some will say a formal proposal is 'best'. It is up to you to decide
> what is
> > 'best'.
> > But by all means discuss it here.
> >
> >
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> >
>
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-- 
Vr gr Peter Elderson
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