[Tagging] Waterway river vs stream.

Kytömaa Lauri lauri.kytomaa at aalto.fi
Sun Oct 20 12:55:59 UTC 2013


>Using "if an able person can jump it" as the rule has some issues. How far

Not only that, but as it was described years back* ("Maybe you can just jump over it." from January 2008) did not seem like a hard set rule, but like a soft description.
* http://wiki.openstreetmap.org/w/index.php?title=Tag:waterway%3Dstream&oldid=69266

That's how I read it, and I'd be inclined to believe that's how many who don't speak English as their native language would read it:

- If you can jump over it, it's probably a stream, but not necessarily
- If you can't jump over it, it's more likely a river, but it might still be a stream
- Locally prevalent mindset will have an effect on where the line between a river and a stream is set. Around here most, if not all, people would never call many of the non-jumpable streams and ditches "rivers", so they would not know to tag them as rivers.

A trunk road is bigger than a residential.
A river is bigger than a stream.
Yet: a trunk road in rural areas may be 1+1 lanes 9 meters, but a residential road elsewhere may be 2+2 lanes and 13 meters plus sidewalks.
Likewise: a river in one part of the world may be narrower than a stream elsewhere. 

When we can't rely on somebody else's authority (e.g. ref for highways), the classification always has some gray areas where local practices use a mixture of locally important attributes to move the line one way or the other.

My point being, that these top level classifications with only two categories hardly make sense for globally valid hard set division by one attribute. If somebody has the means and resources to survey and to tag the width and jumpability and mean annual flow and all that, they will come along and add that later. Being a "stream in OSM" doesn't even tell us with great detail how big it is; a small stream is something you can step over - or even bike over - and a bigger stream might be unjumpable. Is that jumping measured with sneakers and without baggage, or with a backbag filled with a weeks food rations? And which one makes sense as the dividing line for a general use mapping database?

* Was three with waterway=riverbank, but even that has been diluted in this meaning as mappers have had time to draw even narrower rivers with the riverbanks.

-- 
alv


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