[Tagging] Waterway equivalent of noexit=yes?

Tod Fitch tod at fitchfamily.org
Wed Aug 12 16:06:01 UTC 2020

> On Aug 12, 2020, at 4:49 AM, Paul Allen <pla16021 at gmail.com> wrote:
> On Tue, 11 Aug 2020 at 19:19, Tod Fitch <tod at fitchfamily.org <mailto:tod at fitchfamily.org>> wrote:
> It occurred to me that the area where water flow disappears is indeterminate [1], thus the problem mapping it.
> Ordnance Survey represents this as a sort of star of very short waterways
> at the approximate point of disappearance and labels them "spreads."
> The map is representative.  We can tolerate precisely specified amounts of
> doubt and uncertainty.  The name "spreads" indicates the indeterminacy even
> if we map it as a node.  Just as we render a spring as a circle on the
> map, an asterisk would do for spreads.
> Perhaps a “indeterminate=yes” tag on the last node of a water way that “peters out” [2] could be used to signal the QA tools that the end of a water way is not a mistake.
> If we tag it as waterway=spreads the indeterminacy is implied and QA tools
> can be happy there is no mistake.
> Might be useful in cases other than an ephemeral water way in the desert though I haven’t thought of one yet.
> Useful in coastal waterways that peter out in sand above high water.  Or coastal
> waterways that peter out in sand just below high water when the tide is out - they
> haven't carved a channel down to the low water mark, they just vanish into the
> sand (but QA tools won't have a problem with those if they connect to the high
> water mark).  And yes, there are coastal waterways that carve a channel through
> a beach right down to low water and others that just peter out on the beach
> close to high water.

To clarify it for me, the a “waterway=spread” tag would be used on a node (rendered possibly as an asterisk) or on a way? Or either depending the situation?


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