[Tagging] Map a divide?

Philip Barnes phil at trigpoint.me.uk
Fri Oct 5 07:20:20 UTC 2018

You seem to be describing a watershed, which was recently discussed.


Phil (trigpoint) 

On 4 October 2018 15:46:19 BST, Kevin Kenny <kevin.b.kenny at gmail.com> wrote:
>In some maps that I render, I want to show the divide between a couple
>of major river basins. (I have a good DEM for the area in question and
>can derive the line readily.)
>In light of the recent thread on topographic prominence, I wonder if
>this is sufficiently interesting information at least to push it to
>OSM. (If not, that's fine, I have a PostGIS database and a bucket of
>shapefiles and know what to do.)
>If it is sufficiently interesting, the question then arises: how to
>map/tag it?
>'natural=ridge' comes to mind, and the divide in question has a local
>name. (The 'Catskill Divide' separates the basins of the Hudson and
>Delaware Rivers.) This approach appears to run into problems, as I
>read the Wiki. I see:
>> The way should connect saddle points and peaks, and the arrows should
>point upwards.
>That may be all right for a ridge ascending the flank of a single
>mountain, but what I'm talking about is the spine of a range, with the
>ridge traversing dozens of named peaks. Even with a single mountain,
>if there are false summits, the arrows on a single way cannot point
>upward all the time! (And the wiki is clear that the
>Do I misread, and should the reading instead simply be that the
>arrowhead should be higher than the arrow tail? In that case, I could
>break the divide into two ways, with a common endpoint at the highest
>summit in the range.
>Consider this a low-priority item. I have (or will have - there is a
>bit of debugging yet) the data. I know how to render them. I'm happy
>enough with a shapefile or a private PostGIS table if others aren't
>Tagging mailing list
>Tagging at openstreetmap.org

Sent from my Android device with K-9 Mail. Please excuse my brevity.
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