[Tagging] RFC proposed water property key 'ephemeral '

osm.tagging at thorsten.engler.id.au osm.tagging at thorsten.engler.id.au
Wed May 30 05:23:31 UTC 2018

I would like to repeat (slightly extended) the contents of my previous post of how to interpret these tags:


The default state (no tags) is:

water (usually) always present


The seasonal, intermittent and ephemeral tags (allowing season or month timeframes in addition to yes) say:


The value yes and no define a new default state for the whole year (based on tag).


Other values define:

For these times, the explicit state is: the water (usually) always present, is intermittent, or is ephemeral

For all other times, the default state is: (usually) never present.


Always present overrides intermittent overrides ephemeral overrides not present.

Explicit state always overwrites default state.


These specific rules would result in exactly the interpretation you’ve given below.



In summer: explicit state = intermittent

Otherwise: default state = not present



default state = intermittent



in summer: explicit state= always present

otherwise: default state = not present


in combination:

in summer: explicit state= always present

otherwise: default state = intermittent


From: Warin <61sundowner at gmail.com> 
Sent: Wednesday, 30 May 2018 08:32
To: tagging at openstreetmap.org
Subject: Re: [Tagging] RFC proposed water property key 'ephemeral '


On 29/05/18 20:52, Paul Allen wrote:

On Tue, May 29, 2018 at 12:06 AM, Warin <61sundowner at gmail.com <mailto:61sundowner at gmail.com> > wrote:

Adding intermittent=yes to seasonal=yes adds no usefull information either. 

That depends how you interpret it.  Which would depend, to some extent, how it was documented. 

The seasonal=yes says it is non perennial all by it self. 


You're interpreting seasonal as being a specific case of intermittent: sometimes there is water

and sometimes there isn't; the water is present (for example) in summer but not other times of year.


Try this alternative interpretation which is meaningful: there is water there in summer but not

at other times of year however, even in summer, that flow is intermittent.

In that case I would tag


The tag is much clear than 
that could be taken (and how I would interpret it) to have a summer water presence with intermittent water at other times of the year. 


That, i think, would make such a combination meaningful.  Not necessarily how people

would interpret it without further explanation, which would be an argument against such

use, but meaningful.

The tags should 'make sense' without requiring further explanation ... as that generates these kind of problems. 

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