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<div class="moz-cite-prefix">On 25/05/18 20:09, Nick Bolten wrote:<br>
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<div dir="ltr">> <span
style="color:rgb(33,33,33);font-size:13px">The tag provides
mapper a way of tagging rivers and streams that is presently
not available. </span>
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<div><font color="#212121">> </font><span
style="color:rgb(33,33,33);font-size:13px">That will vary ..
year to year and decade to decade ... to much change?</span><span
style="color:rgb(33,33,33);font-size:13px"> </span></div>
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<div style="color:rgb(117,117,117);font-size:13px">> <span
style="color:rgb(33,33,33)">This too will vary.</span></div>
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<div style="color:rgb(117,117,117);font-size:13px"><span
style="color:rgb(33,33,33)">I think something might
be getting lost in translation, since those
questions were rhetorical. I'm describing my
understanding of the proposal as it exists on the
wiki, hoping it matches the intent.</span></div>
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<div style="color:rgb(117,117,117)">> <span
style="color:rgb(33,33,33);font-size:13px">Intermittent
does not equal ephemeral.</span></div>
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<div style=""><font color="#212121">I now understand
that after reading a few reviews, but the wiki
proposal does not make that very clear. From the
wiki articles, an ephemeral body of water "</font><span
style="color:rgb(34,34,34);font-size:14px">is only
present for short duration", and intermittent "</span><span
style="color:rgb(34,34,34);font-size:14px">is used
to indicate that a body of water does not
permanently contain water". From those definitions
alone, I'd assume that a river could have both
`intermittent=yes` and `ephemeral=yes` and be
perfectly valid. However, my new and improved
understanding of hydrology definitions would say
these are separate and incompatible categories of
rivers/streams. </span><span
style="color:rgb(34,34,34);font-size:14px">Page 6 of
this EPA document [1] has definitions that make
these things clearer, maybe a similar approach could
be taken with the wiki.</span></div>
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The proposal clearly says under 'definition' <br>
"A property key for water that is only present for short duration.
‘Short duration’ is typically less than 1 day for each flow. The
majority of the time, at least 90% of the time, the water is not
present."<br>
<br>
The key thing for ephemeral is 'short duration' ... and 'dry most of
the time' ... those words do not exist for 'intermittent' nor
'seasonal' in the OSM wiki. <br>
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<div style=""><span
style="color:rgb(34,34,34);font-size:14px">> </span><span
style="color:rgb(33,33,33);font-size:13px">At
present in OSM the tag to indicate an intermittent
flow that only occurs in winter is</span><span
style="color:rgb(33,33,33);font-size:13px"> </span><span
style="color:rgb(33,33,33);font-size:13px">intermittent=winter</span></div>
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style="color:rgb(33,33,33);font-size:13px"><br>
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<div style=""><span
style="color:rgb(33,33,33);font-size:13px">> </span><font
color="#212121">The proposal for ephemeral flow in
autumn would be </font></div>
<div><font color="#212121">ephemeral=autumn </font></div>
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</font></div>
<div><font color="#212121">> Combining these would
give </font></div>
<div><font color="#212121">> intermittent=winter</font></div>
<div><font color="#212121">> ephemeral=autumn </font></div>
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<div><font color="#212121">> I would think that is
easy enough to understand and matches the present
tagging scheme in use. </font></div>
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<div style=""><span
style="color:rgb(33,33,33);font-size:13px">This is
actually undocumented, and taginfo </span><span
style="color:rgb(33,33,33)">has no examples of
seasons being used as values for the `intermittent`
key. With that said, I was also suggesting that
seasons might more appropriately be values for keys
describing "frequency/type of flow" like
`intermittent` or `ephemeral`, rather than having a
separate `seasonal` tag, due to the ambiguity of
having more than one flow mode over the duration of
a year. Something like
`intermittent:seasonal=<season>` might also
work. Maybe I'm missing a proposal for seasonal
values for `intermittent`?</span></div>
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The key 'intermittent' is poorly defined. <br>
I am not proposing to alter that here (I have another thread on
seasonal, intermittent and ephemeral, suggest that be used for that
kind of discussion).<br>
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<div style="">The idea I'm proposing is that there may
be a 'catch-all' key that describes the 'type' of
thing that `ephemeral` or `intermittent` are, and to
set `intermittent`, `ephemeral`, or otherwise
(`perennial`?) values when appropriate. What about
`flow=ephemeral` or `flow=intermittent`? Then, if you
need to set more specifics, you could use
`flow:ephemeral=winter`. This also provides a
convenient hint for what is being described: the flow
type of the stream.</div>
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1) these keys can also be applied to lakes .. where 'flow' is not
what is wanted.<br>
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<div style="">> The intermittent tag already exists
.. do you want to change it? </div>
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<div>I think we're both considering changes to the
`intermittent` tag as potential options.</div>
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<div>> And what if the stream has a seasonal flow in
say winter and an ephemeral flow possible in spring? </div>
<div>> For this proposal this would be tagged </div>
<div>> seasonal=winter</div>
<div>> ephemeral=spring </div>
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<div>This is super confusing. Namely, the `seasonal`
tag's documentation indicates whether the feature is
present, but in this case it seems to be indicating
that there is a 'full' flow</div>
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No.. is says water is present .. not quantifying the rate of flow or
the depth of water in a lake. It says water is present ... nothing
else.<br>
I can see nothing in the OSK wiki for seasonal that says it is full
flow. Or any set flow rate. <br>
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There is no proposal to tag flow rates .. if you want to do that you
propose it. <br>
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