[Tagging] Drain vs. ditch

Eugene Podshivalov yaugenka at gmail.com
Wed Jan 30 15:28:50 UTC 2019


There are words in the language which let you distinguish natural waterways
by size, e.g. brook -> stream -> river.
The artifical waterways on the contrary are distinguished maily by usage,
rather than by size:
canal - carry useful water
ditch - melioration chanals which are in contact with the land (soak water
from or into land)
drain - carry away superfluous liquid (and hence are usually lined).

Canals due to their purpose are usually but not necesserily large, e.g.
some canals in hydro-power generation can be just a couple of meters wide.
Drains and ditches again due to their purpose are usually small.
The only point at which "size" is in the play is when drainage ditches flow
into a larger channel which eventually carries the water away from a field
or when a large channel brings water to a field and distributes it between
irrigation ditches. These large waterways can be called canals probably
because they get some kind of "useful" connotation.

Maybe we need to delete the "large" and "small" words from the beginning of
definitions at all?

Cheers,
Eugene

ср, 30 янв. 2019 г. в 16:21, EthnicFood IsGreat <ethnicfoodisgreat at gmail.com
>:

>
> > Message: 4
> > Date: Wed, 30 Jan 2019 13:15:41 +0300
> > From: Eugene Podshivalov <yaugenka at gmail.com>
> > To: "Tag discussion, strategy and related tools"
> >       <tagging at openstreetmap.org>
> > Subject: Re: [Tagging] Drain vs ditch
> >
> > ср, 30 янв. 2019 г. в 13:02, Warin <61sundowner at gmail.com>:
> >
> >> Large means?
> >> Small means?
> >>
> >> To me I'd use small = I can step over it, large means I cannot step over
> >> it .. so ~1.1 metres is the line between the two.
> >>
> > Drains and ditches can be 0.1 to 5 metres wide. You can hardly step over
> a
> > 2-5 metre wide ditch, can you? Anything greater than that can be called a
> > canal.
> > So I would leave this up to the user to decide on.
> >
> > Cheers,
> > Eugene
> >
> >
> > ср, 30 янв. 2019 г. в 13:04, Joseph Eisenberg <
> joseph.eisenberg at gmail.com>:
> >
> >> Those descriptions look good
> >> On Wed, Jan 30, 2019 at 5:58 PM Eugene Podshivalov <yaugenka at gmail.com>
> >> wrote:
> >>
> >>> Here is a summary of the discussion to check if there is a consensus.
> >>>
> >>> Current definitions of artificial waterways are unclear and ambiguous.
> >>> Some people assume that ditch and drain differ mainly in size, others
> >>> differentiate them mainly on liquid type (can or cannot carry
> industrial
> >>> discharge), others rely on lined or unlined characteristic.
> >>>
> >>> It is suggested to resolve the ambiguities by updating the definitions
> as
> >>> follows.
> >>>
> >>> canal - Large man-made open flow (free flow vs pipe flow) waterways
> used
> >>> to carry useful water for transportation, hydro-power generation,
> >>> irrigation or land drainage purposes. Consider using waterway=ditch for
> >>> small irrigation or land drainage channels. Consider using
> waterway=drain
> >>> for small usually lined superflous liquid drainage channels.
> >>>
> >>> drain - Small artificial free flow waterways usually lined with
> concrete
> >>> or similar used for carrying away superflous liquid like rain water or
> >>> industrial discharge without letting it soak into the ground. Consider
> >>> using waterway=ditch for unlined channels used to drain nearby wet
> land.
> >>> Consider using waterway=canal for large unlined land drainage channels.
> >>>
> >>> ditch - Small artificial free flow waterways used for irrigating dry
> land
> >>> or draining wet land. Irrigation ditches can be lined or unlined,
> drainage
> >>> ditches are usually unlined to let water soak through the land into
> them.
> >>> Ditches may have short lined segments at waterway turning points or
> >>> intersections with roads or paths to prevent erosion. Consider using
> >>> waterway=canal for large irrigation or land drainage channels. Consider
> >>> using waterway=drain for usually lined superflous liquid drainage
> channels.
> >>>
> >>> Cheers,
> >>> Eugene
> >>>
> >>> вт, 29 янв. 2019 г. в 18:32, marc marc <marc_marc_irc at hotmail.com>:
> >>>
> >>>> Le 29.01.19 à 16:13, Eugene Podshivalov a écrit :
> >>>>> How to we proceed with this topic? Should a proposal be created or
> the
> >>>>> wiki pages can be updated straight away by someone or myself based on
> >>>>> this discussion?
> >>>> maybe it's a good idea to write a small-summary-only post
> >>>> to check if there is a consensus on this, because there are probably
> >>>> many participants who have dropped out given the number of emails that
> >>>> the subject has generated
> >>>> _______________________________________________
> >>>> Tagging mailing list
> >>>> Tagging at openstreetmap.org
> >>>> https://lists.openstreetmap.org/listinfo/tagging
> >>>>
>
> So it sounds like we're using the word "stream" for all natural
> waterways smaller than a river.  This can mean anything from something
> small enough to step across to something several meters across.  Is
> there no other choice of words that can be used to differentiate these
> waterways based on size?  Wouldn't it be desirable for renderers to
> differentiate "major" and "minor" streams differently?  I don't think
> relying on a width tag is a good idea, because it's easier for mappers
> to simply choose between two words to tag one of these waterways rather
> than estimate and assign a width tag.
>
> Mark
>
>
>
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