[Tagging] RFC proposed water property key 'ephemeral '

Christoph Hormann osm at imagico.de
Fri May 25 09:42:32 UTC 2018

On Friday 25 May 2018, Warin wrote:
> Intermittent does not equal ephemeral.

So you have said repeatedly.

I know this is hard for native English speakers but you need to accept 
that tags in OSM do not generally mean what the English language terms 
they use mean.

intermittent=yes in OSM currently means quite precisely what the OSM 
wiki says it means:

"The intermittent=* key is used to indicate that a body of water does 
not permanently contain water."

This includes at least a few 100k features you would define as 
ephemeral.  You can't change that with a proposal.

There is a reason why such a broad and undifferentiated tag has become 
popular in OSM despite there being more differentiated concepts in 
existence:  Because more differentiation here is in many cases 
practically non-verifiable.  No matter if mappers observe on the ground 
or via images, the usual case is they see the waterbody in a dry state 
but see clear indications of recent water cover or water flow hence 
they can assume a non-permanent waterbody.  This is what you can 
currently indicate via intermittent=yes.

But requiring mappers to guess what kind of time pattern the change from 
dry to water cover follows does not work.  Offering this as an option 
in case mappers have more in depth knowledge is a good idea, i said 
that in the past.  But making it mandatory is bound to fail.

Christoph Hormann

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