[Tagging] Definition of lake/pond as applied to stream/plunge pools

[Brian M. Sperlongano]

On Wed, Dec 23, 2020 at 6:00 PM Kevin Kenny <kevin.b.kenny at gmail.com> wrote:

> On Wed, Dec 23, 2020 at 1:25 PM Paul Allen <pla16021 at gmail.com> wrote:
>
>> On Wed, 23 Dec 2020 at 18:04, Brian M. Sperlongano <zelonewolf at gmail.com>
>> wrote:
>>
>>>   I also note that the distinction (effectively) between stream/river
>>> (the only variants that are in serious use) is that a stream is small
>>> enough that it's modeled by a way, while a river is large enough to require
>>> drawing a polygon.
>>>
>>
>> Erm, nope.  The distinction is whether or not you can jump across it.
>> However,
>> wider rivers may benefit from a polygon.  But if you're in a hurry, or
>> can't
>> be bothered, don't use a polygon.
>>
>
> Surely the text on the Wiki agrees with Paul.
>
> Nevertheless, the illustrative picture accompanying it
> https://wiki.openstreetmap.org/wiki/File:Stream_on_Heaphy_Track.jpg shows
> a `waterway=stream` that appears to be wider than I'd try to jump. There's
> nowhere to get a running start, and I'd probably break an ankle in that
> talus.  (Scale isn't quite obvious, but it looks to be about 3m wide
> everywhere but the chute in the center of the picture.)  I could probably
> step across the chute, but it looks awfully slippery, It's hard to tell,
> but it looks as if there are usable 'rock hops' in the slack water both up-
> and downstream.  I'm still fine with 'waterway=stream' for a relatively
> small watercourse like this one, but 'narrow enough for a reasonably fit
> person to leap across' appears to be rather narrower than what people are
> tagging in practice - even in Wiki examples!
>

Hold up.

Yes, it's true that the posed wiki definition is "whether or not you can
jump across it".  However, the wiki also indicates that waterway=stream is
only applied to ways (and not areas), and water=river / waterway=riverbank
is applied only to areas (and not ways).  And of course, there is
waterway=river which also only applies to ways.  (This all presumes that
the wiki is accurate in documenting tagging practice)

To state this a little differently: if you need to tag the area of a stream
(in other words, if it's wide enough that you need a polygon to represent
it, rather than just a way), your only option amongst widely-used tagging
is to decide that what you're mapping is actually a river.  Hence my
paraphrasing: streams are only modeled as ways and rivers can be modeled
with an area.  So from a mapper's perspective, the difference between
river/creek in practice isn't the successful completion of a running long
jump, but a question of whether or not a polygon is needed to model the
watercourse.  I assume that the vast majority of these watercourses are not
mapped by folks testing out their track and field skills but rather are
mapped from imagery.

There is a minor usage of the tag water=stream, but it is unclear whether
that is used in error (i.e. instead of waterway=stream) or is actually
intended to map the area of a stream.

The question of being seasonally dry is not germane to this discussion, as
intermittent=yes is applied to both rivers and streams.  Is the Los Angeles
River a stream because I can jump over the little gutter in the middle that
is the river most of the time?  No, we model it as a river, from concrete
bank to concrete bank and with polygons.
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