[Tagging] Map a divide?

Joseph Eisenberg joseph.eisenberg at gmail.com
Fri Oct 5 01:18:49 UTC 2018


That divide is, ipso facto, a ridge line, because water flows downhill
> - it is a line that's higher than the basins on either side. It runs
> from peak to saddle to peak to saddle (admittedly, the 'peaks' may be
> of but little prominence) for the length of the divide.
>

Agreed. But I'd keep natural=ridge for individual named ridges (which may
have a few named peaks and saddles along it's length)
And use natural=mountain_range for the much larger features which continue
several or many named ridges and peaks and saddles.
Or natural=divide


> Can we agree that https://www.flickr.com/photos/ke9tv/9514469053,
>
https://www.flickr.com/photos/ke9tv/9764660284,
> https://www.flickr.com/photos/ke9tv/10031459724 and
> https://www.flickr.com/photos/ke9tv/14799708048 are all indeed views
> of a ridge?
>

Yes, agreed. The page for natural=ridge shows a rather low, gentle hill as
an example of a ridge.

Open question - which I'll resolve for myself - is how much
> topographic prominence to use when labeling peaks and saddles.  I
> think I'll probably follow the local hiking clubs, and say, '150 feet
> (about 45 m) of prominence, and 1 km separation' for mapping peaks and
> their key cols, and at this point I care about the key cols mostly so
> as to keep the topology of the divide continuous - although I'll
> surely map the names of the saddles where I know them!
>

I'd map all named peaks that have any topographical prominence, but include
the prominence=* in meters.

For example, the most visually significant mountain peak in my hometown is
"Lower Devil's Peak";
It rises over 600m from the valley floor, but only has about 15 meters of
topographical prominence,
because it connects to a high ridge leading to "Middle Devil's Peak" and
"Upper Devil's Peak" (both more prominent).

If you know the topographical prominence it's really helpful to add, to
show that this is a minor sub-peak.

For myself, in the USA, I also more or less follow your idea, adding
unnamed peaks with over 50m prominence,
especially if they have an accurate spot elevation on the USGS maps, even
if they are unnammed.

(BTW, the proposal for "Prominence" is underway; please comment:
https://wiki.openstreetmap.org/wiki/Proposed_features/key:prominence)
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