[Tagging] RFC proposed water property key 'ephemeral '

Nick Bolten nbolten at gmail.com
Fri May 25 05:00:06 UTC 2018

If I understand this proposal right, the goal of this tag is to provide
more specific information for the general likelihood of whether a water
feature (only rivers?) exists: when it comes and goes every days.

This sounds like there are two pieces of information that are desirable to
- What is the frequency of flow/presence?
- Does this frequency vary over seasons?

These seem like questions that deserve separate tags, for flexibility, and
could benefit from a 'subtag' approach. Let's say you want to describe a
river that always has current in the spring and summer, is intermittent in
the fall, and has no flow in the winter. This could look like:


The first tag declares the frequency, but doesn't specify when each tag
applies. The other 3 describe how this frequency varies over seasons. The
presence of more than one value for `intermittent` would be a hint for
incremental mapping/QA: there should be one `intermittent:<value>=<season>`
for every value in `intermittent`. Tagging a single water feature as always
`ephemeral` would also be simple and get combined with the seasonal tag:
`intermittent=ephemeral` `seasonal=<season>`.

I also have a follow-up about the use cases for this data. For example, for
the cases I can imagine off the top of my head (scientific, humanitarian),
it's valuable to know how stale the data is, how the person collecting it
determined the value (memory, general impression as a local?), and ideally
have a yearly report of flow (in some form or another), and so a wikidata
key or external db may serve your use case better. Unfortunately, this
raises a lot of hard questions about linking OSM and time series data that
I don't think are solved, but it the discussion could be valuable in itself.



On Mon, May 21, 2018 at 3:35 PM Warin <61sundowner at gmail.com> wrote:

> Hi,
> Following from the discussion on "Seasonal, intermittent, and ephemeral
> water tags" I have created this proposal.
> Hopefully the definition is tight enough that it excludes intermittent,
> seasonal and any other thing that is not ephemeral.
> I have also included a guide on determination so that mappers can see
> how to determine if something is ephemeral.
> So here it is ...
> https://wiki.openstreetmap.org/wiki/Proposed_features/ephemeral
> Is it clear? Do you understand it?
> Would you use it? If so where?
> Any thing else?
> _______________________________________________
> Tagging mailing list
> Tagging at openstreetmap.org
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