[Tagging] Rivers classification

[Daniel Koć]

W dniu 07.08.2017 o 20:45, Mark Wagner pisze:

> At least in developed countries, you can get an idea of a road's
> classification in the network just by looking at how it's constructed.
> I can stand beside Sprague Avenue, see that it's a one-way road with
> five lanes, and judge that it's probably a primary road.  I can turn to
> my right, see that Sunderland Court doesn't even have a stripe down the
> middle, and know that it's about as minor as a road can get.

That may be a simple case, but if you read the definition, you will see 
that it's not clear classification, so many corner cases are possible 
around the world and the mapper has to decide. Let's see:

"A major highway linking large towns, in developed countries normally 
with 2 lanes. In areas with worse infrastructure road quality may be far 
worse. The traffic for both directions is usually not separated by a 
central barrier. "

It's a mix of the road function (what are the "large towns" exactly?) 
and technical description ("2 lanes", "not separated by a central 
barrier"), but also not universal and not set in stone ("in developed 
countries", "normally", "may be", "usually").

> You can't do the same with rivers.  The Clark Fork River and
> the Colorado River have similar average flows, but the Colorado would
> have a higher classification by any of the proposed measures.

I don't know which classification would be good for my purposes (low 
zoom rendering), but currently we have not a single one defined nor used 
in practice, so I want to start with something. It doesn't need to be 
perfect, maybe simple length=* tag would be useful - but we don't even 
have it currently.

We could also try to craft internal classification similar to mix used 
with roads, for example:

"big river - in developed countries a waterway of national or 
international importance, with elements of river engineering, typically 
used for transport or as a source of hydropower. Usually runs through 
some large towns."

"medium river - a waterway of regional importance, with possibility of 
river engineering. Usually runs through some small towns."

"small river - a waterway of local importance, bigger than stream, where 
typically only canoes and small boats can go and no river engineering 
was done. Usually runs through the rural areas."

This might be general and it would also have multiple corner cases, but 
it's comparable with our roads definitions and would be also useful if 
somebody wants to roughly sort the things out.

-- 
"Like a halo in reverse" [M. Gore]