[Tagging] Topographic Prominence for Peaks
61sundowner at gmail.com
Sun Sep 23 00:17:47 UTC 2018
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:
> "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.
More information about the Tagging