[Tagging] Map a divide?

Warin 61sundowner at gmail.com
Fri Oct 5 07:34:33 UTC 2018

I think a 'watershed' is an area describing the catchment area that drains to one point.
A 'divide' is a single line that describes the division between 2 or more watersheds.

You are right in that they are all water related.

On 05/10/18 17:20, Philip Barnes wrote:
> You seem to be describing a watershed, which was recently discussed.
> https://lists.openstreetmap.org/pipermail/tagging/2018-September/039026.html
> 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
>     interested.
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