As ever this is an interesting question, when is a river not a river,
when it's a stream? Or when is a stream not a stream, when it's a river?
Reading some articles: http://water.usgs.gov/wsc/glossary.html#Stream
and http://en.wikipedia.org/wiki/Stream and
http://en.wikipedia.org/wiki/River I get the feeling that all
watercourses are streams however some become large enough to be called
rivers, but they are still streams.
It seems a river is something that has a source and a mouth (either
where it joins the sea, lake or a larger river). So I would say that
only streams that have been named "River ...." or "The River ..." should
ever be tagged as a river, everything else is a stream.
The are 1st order streams and 12 order streams, as per
http://en.wikipedia.org/wiki/Strahler_Stream_Order.
Also, bear in mind, a watercourse can be named "The River ..." and yet
be tagged as a stream at its lower orders!
One option might be to tag every natural watercourse water=stream and
strahler=[1...12] and then let the renderer choose how to display it
based on the strahler order? Any watercourse that is already "named" as
a river should be so named?
Yet again, I feel that as mappers we spend too much time trying to
define the world around us when we should just be describing it, let the
renderer and the user define based on their viewpoint. I don't think it
is for us to decide when a river is a river and not a stream?
Jonathan
http://bigfatfrog67.me
On 19/10/2013 17:03, Christoph Hormann wrote:
I think the whole issue should be split into two separate questions: The
verifiability of the rule and the rule itself.
As far as verifiability is concerned - it seems the question how far an
able person can jump is not an issue here. As i said before i would
interpret the rule from a practical standpoint, i.e. tag as stream if i
generally would assume crossing this waterway with dry feet would be
considered feasible on a hike by most people without disabilities. Of
course there will be borderline cases but there always are, even if a
quantative rule exists.
The question of changing width of a waterway can also be answered from a
practical perspective - it is sufficient for the waterway to have
occasional points where it can be crossed to qualify.
This interpretation of course also means that the tagging of a waterway
does not only depend on the properties of the waterway itself - a 1
meter wide 'stream' running in a steep walled gorge 10 meter wide on
top cannot practically be jumped across.
Which leads me to the rule itself which - as noted previously - does not
make much sense as a mandatory top level distinction for waterways.
But it has been around for a long time and a lot of data has been
tagged based on it. This in my opinion means changing the meaning of
the existing river/stream distinction - even if there was a practically
verifiable alternative rule - would serve no purpose except devaluing
existing data as well as newly entered information. The only sensible
way to change things would be to move the distinction into a secondary
tag (something like crossable=* for example, that would also allow
tagging the possibility to wade through) and to re-tag all waterways
with a uniform primary tag (natural=waterway would be an obvious choice
although it could be useful to make the distinction natural/artificial
waterway indeed mandatory).
Greetings,
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