[Tagging] Topographic Prominence for Peaks

Warin 61sundowner at gmail.com
Sun Sep 23 05:48:45 UTC 2018

I don't think OSM can use wikipedia as a source?
Something about incompatible licences.

How to calculate prominence will need to documented in OSM rather than refer to wikipoedia.

On 23/09/18 11:04, Joseph Eisenberg wrote:
> 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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