[Tagging] Topographic Prominence for Peaks

Kevin Kenny kevin.b.kenny at gmail.com
Mon Sep 24 03:46:46 UTC 2018

On Sun, Sep 23, 2018 at 9:29 PM Bill Ricker <bill.n1vux at gmail.com> wrote:
> This all seems like highly specialized, technical data that is not of
> general interest, as no one but peak-baggers understand the technical
> definition. Many map users seeing this prominence=999m factoid would
> jump to the incorrect conclusion that it was relative to where the
> (lower of the) watershed(s) drains the mountain and thus a synonym for
> the net rise from the valley.(Which is what i read the original post's
> introductory remarks as meaning until I read further and got to the
> technical definition.)

"The (lower of the) watershed(s) that drains the mountain" is
a phrase with unclear meaning.  If by that you mean the highest
origin of a stream on the mountainside, that's usually pretty high
up. If you mean "the bottom of the deepest nearby valley",
how far downstream do you go, and how do you define where
to stop? It's very hard to come up with a coherent, objective
definition that stops short of "sea level".

For mountains that are close to higher mountains, the prominence
is almost always "the height of this mountain above the
highest pass on any side", which is as good a definition as
any. For mountains that are the highest in their ranges, the
prominence is, as you might expect, roughly "the
height of this peak above the surrounding plain".

The only thing that is "highly technical" is that it is quite difficult
to come up with a definition for topographic prominence with
the necessary mathematical rigour to make it objective.

If you look at a list of mountains of the Earth having the highest
prominence, and compare it with the list of the highest elevation,
you will see that prominence actually does a fairly good job at
capturing "local importance:"

By elevation:
1. Everest
2. K2
3. Kanchenjunga, India/Nepal
4. Lhotse I, Nepal/Tibet
5. Makaku I, Nepal/Tibet
6. Cho Oyu, Nepal
7. Dhaulagiri, Nepal
8. Manaslu I, Nepal
9. Nanga Parbat, Pakistan
10. Annapurna I, Nepal
11. Gasherbrum I, Pakistan/China
12. Broad Peak, Pakistan/China
13. Gasherbrum II, Pakistan/China
14. Shisha Pangma, Tibet

By prominence:

1. Everest
2. Aconcagua (High point of S. America)
3. Denali (Mt. McKinley - high point of N. America)
4. Kilimanjaro (High point of Africa)
5. Cristobal Colon (High point of Colombia)
6. Mt. Logan (High point of Canada)
7. Pico de Orizaba (High point of Mexico)
8. Vinson Massif (High point of Antarctica)
9. Puncak Jaya (High point of New Guinea)
10. Mt. Elbrus (High point of Europe)
11. Mont Blanc (High point of the Alps)
12. Damavand (High point of Iran)
13. Kluchevskaya Volcano (High point of Asian Russia)
14. Nanga Parbat (High point of Pakistan)

The first list is confined to the Himalayas, and contains many
relatively obscure entries. The second list has peaks on every
continent except Australia, and consists entirely of
"This is the highest point in (major geographic feature)"

In any case, topographic prominence is very closely related
to the theory of surface network modeling, which in turn ties
closely into research into the representation of terrain with
as few data points as possible.

> Is the OSM primary DB the right repository for this?
> Have we accepted being the repository for everything that anyone wants to map?
> (I don't remember hearing a change from "no".)

Do we really want to get into the argument that objectively
verifiable attributes of real-world features should NOT be mapped
because they are not of sufficiently general interest?
"Objectively verifiable," "actually representing objects
in the field," and "obtainable by direct survey or
from license-compatible data sets" are already a high bar.
I had not heard that the decision of what may be mapped
also has to win a popularity contest!

It isn't a very long step from saying 'topographic prominence
should not be mapped because it is of interest only to mountaineers'
to saying 'hiking trails should not be mapped because they are of
interest only to hikers', or 'navigational aids on waterways should
not be mapped because they are of interest only to sailors.'
'Radio repeaters should not be mapped because they are
of interest only to Amateur Radio operators." "Specimen trees
should not be mapped because they are of interest only
to conservationists." Where does it end?
Do we need to start conducting a census of OSM users to
determine whose interests are important enough to include?

I'm sorry, but to me, your message comes across as
saying, "this thing does not interest ME and I misunderstood
it at first reading, therefore YOU may not map it and must
go elsewhere." That's a positively insulting message to be

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